Method of detecting Salmonella typhimurium

Information

  • Patent Grant
  • 11946107
  • Patent Number
    11,946,107
  • Date Filed
    Thursday, June 15, 2017
    6 years ago
  • Date Issued
    Tuesday, April 2, 2024
    a month ago
Abstract
Provided herein are methods and compositions for detecting Salmonella typhimurium in a sample.
Description
SEQUENCE LISTING

The instant application contains a Sequence Listing which has been submitted electronically herewith and is hereby incorporated by reference in its entirety. The ASCII copy, created on Dec. 17, 2018, is named 1050901_SEQ_ST25.txt, and is 5,089 bytes in size.


BACKGROUND


Salmonella is a leading cause of foodborne illnesses worldwide, with poultry and pork products being a primary source of infection to humans. Detecting Salmonella can be challenging because low levels of the bacteria may not be recovered using traditional culturing techniques. The genus Salmonella, member of the Enterobacteriaceae family, comprises two species Salmonella enterica and Salmonella bongori. Salmonella enterica is further divided into six subspecies, of which S. enterica subsp. enterica is the most clinically significant, causing 99% of Salmonella infections. The subspecies are further sub-divided into more than 2,500 serovars defined by somatic and flagellar antigens. Salmonella enterica subsp. enterica serovar Typhimurium and Salmonella enterica subsp. enterica serovar Enteritidis are the most frequently reported serovars associated with human cases of Salmonella infection from foodborne outbreaks. In the EU, a regulation in force since 2003 governs the mandatory detection of Salmonella. In 2011, this regulation was supplemented with the mandatory testing for S. enteritidis and S. typhimurium. According to Commission Regulation (EU) No. 1086/2011, all fresh poultry must be examined for S. enteritidis and S. typhimurium contamination. In the United States, the Food and Drug Administration (FDA) has published the Final Rule “Prevention of Salmonella enteritidis in Shell Eggs During Production, Storage, and Transportation” (74 FR 33030), which will introduce methods requiring egg producers to test for S. enteritidis. For non-egg producers, the FDA also published the guidance document for testing of human foods for salmonella: “Guidance for Industry: Testing for Salmonella Species in Human Foods and Direct-Human-Contact Animal Foods”.


Conventional microbiological methods for the detection and identification of Salmonella serovars are very time consuming. The current accepted method for isolation of Salmonella from food and environmental primary production samples takes up to 5 days according to the ISO 6579. The most widely-used method used to characterize Salmonella into its subspecies is the Kauffman-White serotyping system, based on the variability of the O, H and Vi antigens.


SUMMARY

Described herein are methods and compositions for detecting Salmonella typhimurium.


In an embodiment, a method of selectively detecting the presence of Salmonella typhimurium in a sample comprises (a) providing a reaction mixture comprising a suitable primer pair for amplification of residues 749 to 2136 (1388 bp), or a portion thereof, of Salmonella typhimurium ACCESSION CP007235 (SEQ ID NO:1); (b) performing PCR amplification of the nucleic acids of the sample using the reaction mixture of step (a); and (c) selectively detecting the presence of Salmonella typhimurium by detecting the amplified nucleic acids. In some embodiments, the step (b) is performed in partitions. In some embodiments, the detecting the presence of Salmonella typhimurium comprises sequencing the amplified nucleic acids.


In some embodiments, the reaction mixture comprises a primer pair for amplification of a sequence 95%, 97% or 99% homologous to SEQ ID NO:1 or a portion thereof. In certain embodiments, the reaction mixture comprises a primer pair for amplification of residues 749 to 1697 (947 bp), or portions thereof, of Salmonella typhimurium ACCESSION CP007235 (SEQ ID NO:2). In some embodiments, the reaction mixture comprises a primer pair for amplification of a sequence 95%, 97% or 99% homologous to SEQ ID NO:2 or a portion thereof. In certain embodiments, the reaction mixture comprises a primer pair for amplification of residues 755 to 1063 (309 bp), or portions thereof, of Salmonella typhimurium ACCESSION CP007235 (SEQ ID NO:3). In some embodiments, the reaction mixture comprises a primer pair for amplification of a sequence 95%, 97% or 99% homologous to SEQ ID NO:3 or a portion thereof.


In an embodiment, the primer pair for amplification of the nucleic acid region of SEQ ID NO:3 comprises the polynucleotide sequences set forth in SEQ ID NO:4 and SEQ ID NO:5. In an embodiment, the reaction mixture further comprises a probe for the nucleic acid region to be detected. In some embodiments, the probe comprises a detectable label. In some embodiment, the probe comprises the polynucleotide sequences set forth in SEQ ID NO:6 and SEQ ID NO:7. In certain embodiments, the probe comprises the polynucleotide sequences set forth in SEQ ID NO:6, SEQ ID NO:7, SEQ ID NO:8, or SEQ ID NO:9.


In an embodiment, an isolated polynucleotide comprises a polynucleotide sequence having at least 95% sequence identity based on the BLASTN method of alignment to the polynucleotide sequence set forth in SEQ ID NO:1. In some embodiments, the isolated polynucleotide sequence comprises a polynucleotide sequence set forth in SEQ ID NO:1. In an embodiment, an isolated polynucleotide comprises a polynucleotide sequence having at least 95% sequence identity based on the BLASTN method of alignment to the polynucleotide sequence set forth in SEQ ID NO:2. In some embodiments, the isolated polynucleotide sequence comprises a polynucleotide sequence set forth in SEQ ID NO:2. In an embodiment, an isolated polynucleotide comprises a polynucleotide sequence having at least 95% sequence identity based on the BLASTN method of alignment to the polynucleotide sequence set forth in SEQ ID NO:3. In some embodiments, the isolated polynucleotide sequence comprises a polynucleotide sequence set forth in SEQ ID NO:3.


In an embodiment, a kit for the detection of Salmonella typhimurium in a sample comprises a primer pair comprising SEQ ID NO:4 and SEQ ID NO:5. In some embodiments, the kit further comprises a probe comprising SEQ ID NO:6 and SEQ ID NO:7. In some embodiments, the kit further comprises a probe comprising SEQ ID NO:6, SEQ ID NO:7, SEQ ID NO:8, or SEQ ID NO:9. In certain embodiments, the kit further comprises at least one component selected from a lysis reagent, a DNA polymerase, at least one dNTP, a buffer, a negative control, a positive control, and instructions for performing a method to detect the presence of Salmonella typhimurium in a nucleic acid sample.







DETAILED DESCRIPTION

Provided herein are methods of selectively detecting the presence of Salmonella typhimurium in a sample. Also provided are compositions for use in the detection of Salmonella typhimurium in a sample by nucleic acid amplification, e.g., by real-time PCR.


The disclosed detection method finds utility in the detection of S. typhimurium in any type of sample, for example in samples for food testing, environmental testing, or human/animal diagnostic testing. Exemplary food samples include, but are not limited to, meats products, poultry (e.g., chicken, turkey), eggs, fish (e.g, cod), cookie dough, produce (e.g, lettuce, tomatoes), dairy (e.g, cheese, milk), milk powder (e.g., infant formula), chocolate (e.g., milk), cocoa, nacho cheese seasoning, pasta, pet food, peanut butter, soy flour, spices, and ready-to-eat food. Environmental samples include, but are not limited to, plastic, sealed concrete, and stainless steel. Other types of samples include, but are not limited to, water, stool, blood, urine, and tissue. Another type of sample includes weeds. The methods may be performed at the farm or processing facility prior to initial packaging, after packaging (e.g., prior to or after export from one country to another), or at the point of sale.


I. DEFINITIONS

Unless defined otherwise, technical and scientific terms used herein have the same meaning as commonly understood by a person of ordinary skill in the art. See, e.g., Lackie, DICTIONARY OF CELL AND MOLECULAR BIOLOGY, Elsevier (4th ed. 2007); Green et al., MOLECULAR CLONING, A LABORATORY MANUAL (FOURTH EDITION), Cold Spring Harbor Laboratory Press (Cold Spring Harbor, NY 2012).


The term “a” or “an” is intended to mean “one or more.” The term “comprise” and variations thereof such as “comprises” and “comprising,” when preceding the recitation of a step or an element, are intended to mean that the addition of further steps or elements is optional and not excluded. Any methods, devices and materials similar or equivalent to those described herein can be used in the practice of this invention. The following definitions are provided to facilitate understanding of certain terms used frequently herein and are not meant to limit the scope of the present disclosure.


The term “nucleic acid” refers to polymers of deoxyribonucleotides or ribonucleotides in either single- or double-stranded form, and complements thereof. The term “polynucleotide” refers to a linear sequence of nucleotides. Nucleotides can be ribonucleotides, deoxyribonucleotides, or modified versions thereof. Examples of polynucleotides contemplated herein include single and double stranded DNA, single and double stranded RNA (including siRNA), and hybrid molecules having mixtures of single and double stranded DNA and RNA.


“Polymerase chain reaction” is abbreviated PCR.


The term “isolated” refers to materials, such as nucleic acid molecules and/or proteins, which are substantially free or otherwise removed from components that normally accompany or interact with the materials in a naturally occurring environment. Isolated polynucleotides can be purified from a host cell in which they naturally occur. Conventional nucleic acid purification methods known to skilled artisans can be used to obtain isolated polynucleotides. The term also embraces recombinant polynucleotides and chemically synthesized polynucleotides.


The terms “polynucleotide”, “polynucleotide sequence”, “nucleic acid sequence”, and “nucleic acid fragment” are used interchangeably herein. These terms encompass nucleotide sequences and the like. A polynucleotide can be a polymer of RNA or DNA that is single- or double-stranded, that optionally contains synthetic, non-natural, or altered nucleotide bases. A polynucleotide in the form of a polymer of DNA can be comprised of one or more strands of cDNA, genomic DNA, synthetic DNA, or mixtures thereof.


The term “amplification product” refers to nucleic acid fragments produced during a primer-directed amplification reaction. Typical methods of primer-directed amplification include polymerase chain reaction (PCR), ligase chain reaction (LCR), or strand displacement amplification (SDA). If PCR methodology is selected, the replication composition can comprise the components for nucleic acid replication, for example: nucleotide triphosphates, two (or more) primers with appropriate sequences, thermostable polymerase, buffers, solutes, and proteins.


The term “primer” refers to a synthetic oligonucleotide that is capable of acting as a point of initiation of nucleic acid synthesis or replication along a complementary strand when placed under conditions in which synthesis of a complementary strand is catalyzed by a polymerase. A primer can further contain a detectable label, for example a 5′ end label.


The term “probe” refers to a synthetic oligonucleotide that is complementary (though not necessarily fully complementary) to a polynucleotide of interest and forms a duplexed structure by hybridization with at least one strand of the polynucleotide of interest. A probe can further contain a detectable label.


As used herein, the terms “label”, “detectable label”, and such refer to a molecule capable of detection, including, but not limited to, radioactive isotopes, fluorescers, chemiluminescers, enzymes, enzyme substrates, enzyme cofactors, enzyme inhibitors, chromophores, dyes, metal ions, metal sols, semiconductor nanocrystals, and ligands (e.g., biotin, avidin, streptavidin, or haptens). A detectable label can also include a combination of a reporter and a quencher.


The term “reporter” refers to a substance or a portion thereof which is capable of exhibiting a detectable signal, which signal can be suppressed by a quencher. The detectable signal of the reporter is, e.g., fluorescence in the detectable range; thus, a reporter can also be a label.


The term “quencher” refers to a substance which is capable of suppressing, reducing, inhibiting, etc., the detectable signal produced by the reporter.


As used herein, the term “quenching” refers to a process whereby, when a reporter and a quencher are in close proximity, and the reporter is excited by an energy source, a substantial portion of the energy of the excited state non-radiatively transfers to the quencher where it either dissipates nonradiatively or is emitted at a different emission wavelength than that of the reporter (e.g., by fluorescence resonance energy transfer or FRET).


The reporter can be selected from fluorescent organic dyes modified with a suitable linking group for attachment to the oligonucleotide, such as to the terminal 3′ carbon or terminal 5′ carbon. The quencher can also be selected from organic dyes, which may or may not be fluorescent, depending on the embodiment of the invention. Generally, whether the quencher is fluorescent or simply releases the transferred energy from the reporter by non-radiative decay, the absorption band of the quencher should at least substantially overlap the fluorescent emission band of the reporter to optimize the quenching.


Non-fluorescent quenchers or dark quenchers typically function by absorbing energy from excited reporters, but do not release the energy radiatively.


Selection of appropriate reporter-quencher pairs for particular probes can be undertaken in accordance with known techniques. Fluorescent and dark quenchers and their relevant optical properties from which exemplary reporter-quencher pairs can be selected are listed and described, for example, in R. W. Sabnis, HANDBOOK OF FLUORESCENT DYES AND PROBES, John Wiley and Sons, New Jersey, 2015, the content of which is incorporated herein by reference.


Reporter-quencher pairs can be selected from xanthene dyes including fluoresceins and rhodamine dyes. Many suitable forms of these compounds are available commercially with substituents on the phenyl groups, which can be used as the site for bonding or as the bonding functionality for attachment to an oligonucleotide. Another group of fluorescent compounds for use as reporters are the naphthylamines, having an amino group in the alpha or beta position. Included among such naphthylamino compounds are 1-dimethylaminonaphthyl-5 sulfonate, 1-anilino-8-naphthalene sulfonate and 2-p-touidinyl-6-naphthalene sulfonate. Other dyes include 3-phenyl-7-isocyanatocoumarin; acridines such as 9-isothiocyanatoacridine; N-(p-(2-benzoxazolyl)phenyl)maleimide; benzoxadiazoles; stilbenes; pyrenes and the like.


Suitable examples of quenchers can be selected from 6-carboxy-tetramethyl-rhodamine, 4-(4-dimethylaminophenylazo) benzoic acid (DABCYL), tetramethylrhodamine (TAMRA), BHQ-O™, BHQ-1™, BHQ-2™, and BHQ-3™, each of which are available from Biosearch Technologies, Inc. of Novato, Calif., Qy7™ QSY-9™, QSY-21 TM and QSY-35™, each of which are available from Molecular Probes, Inc, Iowa Black™ FQ available from Integrated DNA Technologies.


Suitable examples of reporters can be selected from dyes such as SYBR green, 5-carboxyfluorescein (5-FAM™ available from Applied Biosystems of Foster City, Calif.), 6-carboxyfluorescein (6-FAM), tetrachloro-6-carboxyfluorescein (TET), 2,7-dimethoxy-4,5-dichloro-6-carboxyfluorescein, hexachloro-6-carboxyfluorescein (HEX), 6-carboxy-2′,4,7,7′-tetrachlorofluorescein (6-TET™ available from Applied Biosystems), carboxy-X-rhodamine (ROX), 6-carboxy-4′,5′-dichloro-2′,7′-dimethoxyfluorescein (6-JOE™ available from Applied Biosystems), VIC™ dye products available from Molecular Probes, Inc., NED™ dye products available from Applied Biosystems, Cal Fluor dye products (such as, e.g., Cal Fluor Gold 540, Orange 560, Red 590, Red 610, Red 635) available from Biosearch Technologies, Quasar dye products (such as, e.g., Quasar 570, 670, 705) available from Biosearch Technologies, and the like.


The term “percent identity,” in the context of two or more nucleic acids, refers to two or more sequences or subsequences that are the same or have a specified percentage of nucleotides that are the same (i.e., about 60% identity, preferably 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or higher identity over a specified region, when compared and aligned for maximum correspondence over a comparison window or designated region) as measured using a BLAST or BLAST 2.0 sequence comparison algorithms with default parameters, or by manual alignment and visual inspection. See e.g., the NCBI web site at ncbi.nlm.nih.gov/BLAST. Such sequences are then said to be “substantially identical.” Percent identity is typically determined over optimally aligned sequences, so that the definition applies to sequences that have deletions and/or additions, as well as those that have substitutions. The algorithms commonly used in the art account for gaps and the like. Typically, identity exists over a region comprising a sequence that is at least about 25 nucleotides in length, or over a region that is 50-100 nucleotides in length, or over the entire length of the reference sequence.


The terms “selectively” or “selective” with respect to nucleic acids refers to the discrimination between the target nucleic acid sequence (e.g., target sequence of Salmonella typhimurium) over the non-target nucleic acid sequences (e.g., non-target sequence Salmonella typhimurium). An assay is selective for a sequence if little or no hybridization of the primer or probe occurs with non-target sequence.


The terms “partitioning” or “partitioned” refer to separating an aqueous solution having one or more of a sample and reactant into a plurality of portions, or “partitions.” Partitions can be solid or fluid. In some embodiments, a partition is a solid partition, e.g., a microchannel. In some embodiments, a partition is a fluid partition, e.g., a droplet. In some embodiments, a fluid partition (e.g., a droplet) is a mixture of immiscible fluids (e.g., water and oil). In some embodiments, a fluid partition (e.g., a droplet) is an aqueous droplet that is surrounded by an immiscible carrier fluid (e.g., oil).


II. NUCLEIC ACIDS

Genome Detection Regions


A detection method is provided herein that is based on the identification of residues 749 to 2136 (1388 bp) of Salmonella typhimurium ACCESSION CP007235 (see SEQ ID NO: 1 in Table 1).









TABLE 1







Sequences









SEQ




ID




NO
DESCRIPTION
SEQUENCE





1
1388 bp fragment
ATGTAGCTTAAGATATCTATAGTGATATCAGTGTAATACTTATTGGTTAG



from the 3315 bp
ATCGGTATGATCTTGAATATTTTTATATCGATAGTTTGGATTACATAGTA



gene of
GAGTTATTTCACTTTGCAATACAGCTTTAATTATAGTTTTGTCAAGTTGT




Salmonella

AATTTATCTATAAAAATATTATTTATAGTATTTTCTATTAGGAGAAGTGT



Typhimurium
TTCGACTAACTTGATATTTGTATTGATTTTTTGTTTGTAGATATTCCGTA



ACCESSION
GCAATTGAGTTGAATTGTGTTCAAGCAATGGTGAACAAACATAATCCCAT



CP007235
GATTGCTCTTGAGAGTCCCAGTCATTTTTAGCTATTTCAATAGCATTGGT




GACTAATTCGATAATTTCATCTTCAATTTCTGGATATGGTACTGAGGCTA




ATTCACCACTAGTAAAGCTAAGTGTGGGGGCTAGTATTGATAAATAATGG




TTTACAACCGGAGTGCACATTAATCCCGCAGCGTAAAGCAACTCATTTTT




GTTATTTGAAAAGCCGCAACGGCCTGTATCATCAAAAACAAACCCTTTTG




GACGATATCTCACGCAAAAATTACCTTGGCTTATTTTTGACCATGTTATG




CCTTCTCTAAAGTAATACTCATCATTTCTTACGGCAGAGCGAGTTTTGCC




ATTCTCAAATTTAAAATTTCGTATTTCGTAACCATTATTTTCCCAATTTA




CAACTATTTCGTTATTACCATACCACTTTCGATATTCACCTCCACTACTA




CAAGGAAACCATTTGATATTATGAATGTCGATTTTTGTATTTGATTCTTT




ATTTGTGATAAGGGTTTTTTTTATTGAAACCTCGTACCAATATCTTTGAA




ATTTAATATTGTCACCGGTGGACATGCCTGCTTTTAATGCTATTTTTTCT




CCAAGTTTTTTATGGTGGCGAAAAGATAATAGACTCGGTAAGTCTATCCA




ATATGCTATTGGCATTCCTGGTATGTTTTTAAAATCATGCTGTGTAAATT




TATCAAATATATTTTTCCTTAGAAGTAGATCGCTTTTCTTTACTTCTTCC




CTACCATCTATAAGTCTAAAAAATACAGGTTGGTAACGTTCGGAGTGTTG




GTTTTTAATCACCCAGGCAGTTGTCTGTACAACCTCTCCAGAAATTTGCC




CAAAAGCCCGAGCTCCCAAATGTGCCATCGTAATAAATGTTTTATTGTCC




AATAACCAGTTACGTAGTGCTTCATAACTTGACAAAAACATCCATGATTG




CATATTGACTTGAGCATTAAACCCATTTTCTTTAAGCAAAGAAAATGCAT




TCTGCATAAACATTGCAAACAAATCAGCTTTACTATCCGGGAAGTTATTT




TTGGCAAACTCTTTCAGCTCACTATTCATTCCCTTGCC





2
947 bp fragment
ATGTAGCTTAAGATATCTATAGTGATATCAGTGTAATACTTATTGGTTAG



of Salmonella
ATCGGTATGATCTTGAATATTTTTATATCGATAGTTTGGATTACATAGTA



Typhimurium
GAGTTATTTCACTTTGCAATACAGCTTTAATTATAGTTTTGTCAAGTTGT



ACCESSION
AATTTATCTATAAAAATATTATTTATAGTATTTTCTATTAGGAGAAGTGT



CP007235
TTCGACTAACTTGATATTTGTATTGATTTTTTGTTTGTAGATATTCCGTA




GCAATTGAGTTGAATTGTGTTCAAGCAATGGTGAACAAACATAATCCCAT




GATTGCTCTTGAGAGTCCCAGTCATTTTTAGCTATTTCAATAGCATTGGT




GACTAATTCGATAATTTCATCTTCAATTTCTGGATATGGTACTGAGGCTA




ATTCACCACTAGTAAAGCTAAGTGTGGGGGCTAGTATTGATAAATAATGG




TTTACAACCGGAGTGCACATTAATCCCGCAGCGTAAAGCAACTCATTTTT




GTTATTTGAAAAGCCGCAACGGCCTGTATCATCAAAAACAAACCCTTTTG




GACGATATCTCACGCAAAAATTACCTTGGCTTATTTTTGACCATGTTATG




CCTTCTCTAAAGTAATACTCATCATTTCTTACGGCAGAGCGAGTTTTGCC




ATTCTCAAATTTAAAATTTCGTATTTCGTAACCATTATTTTCCCAATTTA




CAACTATTTCGTTATTACCATACCACTTTCGATATTCACCTCCACTACTA




CAAGGAAACCATTTGATATTATGAATGTCGATTTTTGTATTTGATTCTTT




ATTTGTGATAAGGGTTTTTTTTATTGAAACCTCGTACCAATATCTTTGAA




ATTTAATATTGTCACCGGTGGACATGCCTGCTTTTAATGCTATTTTTTCT




CCAAGTTTTTTATGGTGGCGAAAAGATAATAGACTCGGTAAGTCTAT





3
123 bp fragment
TAGGAGAAGTGTTTCGACTAACTTGATATTTGTATTGATTTTTTGTTTGT



of Salmonella
AGATATTCCGTAGCAATTGAGTTGAATTGTGTTCAAGCAATGGTGAACAA



Typhimurium
ACATAATCCCATGATTGCTCTTG



ACCESSION




CP007235






4
Forward Primer
TAGGAGAAGTGTTTCGACTAAC



for 123 bp target




sequence




spanning residues




937 to 958






5
Reverse Primer
CAAGAGCAATCATGGGATTATG



for 123 bp target




sequence




spanning residues




1038 to 1059






6
Probe for 123 bp
TTTACAATTGAGTTGAATTGTGTTCAAGC



target sequence




spanning residues




1000 to 1024




(5′FAM-3′BkFQ)






7
Probe for 123 bp
AAAAGAACACAATTCAACTCAATTGCTACG



target sequence




spanning residues




995 to 1020




(5′FAM-3′BkFQ)






8
Probe for 123 bp
CAATTGAGTTGAATTGTGTTCAAGC



target sequence




spanning residues




1000 to 1024




(5′FAM-3′BkFQ)






9
Probe for 123 bp
GAACACAATTCAACTCAATTGCTACG



target sequence




spanning residues




995 to 1020









Based on a publicly available software (e.g., BLAST), SEQ ID NO:1 is conserved (e.g., 100% sequence identity) in 672 Salmonella typhimurium strains listed by Genbank accession number in Table 2.









TABLE 2





Strains of Salmonella Typhimurium in which SEQ ID NO: 1 is 100% Conserved


















LVHC01000004.1
LAPF01000001.1
CTPI01000002.1
CTHF01000003.1


LVHA01000006.1
LAPD01000063.1
CTPH01000002.1
CTHE01000002.1


LVGZ01000004.1
LAPC01000018.1
CTPG01000002.1
CTHD01000002.1


LVGY01000004.1
LAOX01000013.1
CTPF01000002.1
CTHC01000003.1


LVGX01000005.1
JZAH01000029.1
CTPE01000003.1
CTHB01000001.1


LVGW01000004.1
JZAB01000025.1
CTPD01000001.1
CTHA01000002.1


LVGU01000047.1
JYZR01000005.1
CTPC01000003.1
CTGZ01000002.1


LVGT01000051.1
JYZC01000010.1
CTPB01000003.1
CTGY01000002.1


LVGS01000046.1
JYZB01000030.1
CTPA01000004.1
CTGX01000005.1


LVGR01000047.1
JYYZ01000004.1
CTOZ01000002.1
CTGW01000025.1


LVGQ01000013.1
JYYU01000025.1
CTOY01000002.1
CTGV01000002.1


LVGP01000004.1
JYYT01000016.1
CTOX01000003.1
CTGU01000006.1


LVGN01000006.1
JYYQ01000066.1
CTOW01000001.1
CTGT01000002.1


LVGM01000008.1
JYYL01000011.1
CTOV01000003.1
CTGS01000002.1


LVGL01000007.1
JYYK01000018.1
CTOU01000002.1
CTGR01000004.1


LVGK01000003.1
JYYH01000035.1
CTOT01000003.1
CTGQ01000002.1


LVGJ01000009.1
JYYC01000006.1
CTOS01000002.1
CTGP01000004.1


LVGI01000006.1
JYYB01000003.1
CTOR01000003.1
CTGO01000001.1


LVGH01000005.1
JYYA01000024.1
CTOQ01000004.1
CTGN01000001.1


LVGG01000006.1
JYXZ01000019.1
CTOP01000003.1
CTGM01000002.1


LVGF01000006.1
JYXX01000004.1
CTOO01000002.1
CTGL01000004.2


LVFW01000011.1
JYXW01000003.1
CTON01000002.1
CTGK01000002.1


LVFV01000011.1
JYXT01000019.1
CTOM01000004.1
CTGJ01000035.1


LVFT01000012.1
JYXK01000009.1
CTOL01000003.1
CTGI01000004.1


LVFS01000014.1
JYXH01000002.1
CTOK01000002.1
CTGH01000004.1


LVFR01000005.1
JYXC01000008.1
CTOJ01000001.1
CTGG01000002.1


LVFQ01000008.1
JYWW01000034.1
CTOI01000002.1
CTGF01000002.1


LVFP01000006.1
JYWU01000014.1
CTOH01000003.1
CTGE01000002.1


LVFO01000002.1
JYWT01000009.1
CTOG01000003.1
CTGD01000002.1


LVFN01000004.1
JYWA01000003.1
CTOF01000002.1
CTGC01000002.1


LVFM01000005.1
JYVW01000007.1
CTOE01000002.1
CTGB01000004.1


LVFL01000037.1
JYVV01000004.1
CTOD01000002.1
CTGA01000002.1


LVFK01000003.1
JYVU01000035.1
CTOC01000003.1
CTFZ01000004.1


LVFJ01000013.1
JYVL01000001.1
CTOB01000002.1
CTFY01000002.1


LVFI01000003.1
JYVJ01000004.1
CTOA01000004.1
CTFX01000001.1


LVFH01000010.1
JYVG01000055.1
CTNZ01000003.1
CTFW01000003.1


LUJG01000006.1
JYVE01000037.1
CTNY01000003.1
CTFV01000004.1


LUJF01000005.1
JYUZ01000004.1
CTNX01000002.1
CTCJ01000002.1


LUJE01000003.1
JYUY01000010.1
CTNW01000004.1
CTCI01000003.1


LUJC01000020.1
JYUP01000020.1
CTNV01000003.1
CTGH01000003.1


LUIZ01000005.1
JYTX01000005.1
CTNU01000002.1
CTCG01000002.1


LUIY01000005.1
JYTW01000027.1
CTNT01000002.1
CTCF01000002.1


LUIW01000007.1
JYTU01000018.1
CTNS01000003.2
CTCE01000003.1


LUIU01000061.1
JYTT01000012.1
CTNR01000001.1
CTCD01000002.1


UIT01000019.1
JYTQ01000001.1
CTNQ01000001.1
CTCC01000044.1


UIS01000029.1
JYTP01000017.1
CTNP01000002.1
CTCB01000003.1


LUIR01000027.1
JYTL01000012.1
CTNO01000002.1
CTCA01000003.1


LUIQ01000009.1
JYTI01000010.1
CTNN01000003.1
CTBZ01000002.1


LUIP01000019.1
JYTD01000002.1
CTNM01000002.1
CTBY01000002.1


LUIO001000023.1
JYTB01000004.1
CTNL01000002.1
CTBX01000003.1


LUIN01000035.1
JYSY01000001.1
CTNK01000004.1
CTBW01000004.1


LUIM01000025.1
JYSX01000031.1
CTNJ01000001.1
CTBV01000003.1


LUIL01000040.1
JYSO01000094.1
CTNI01000002.1
CTBU01000002.1


LUIK01000041.1
JYSN01000051.1
CTNH01000002.1
CTBT01000001.1


LUIJ01000024.1
JYSM01000007.1
CTNG01000036.1
CTBS01000003.1


LUII01000036.1
JYSL01000029.1
CTNF01000003.1
CTBR01000004.1


LUIH01000014.1
JYSG01000016.1
CTNE01000002.1
CTBQ01000003.1


LUIG01000040.1
JYSB01000024.1
CTND01000002.1
CTBP01000005.1


LUIF01000036.1
JYSA01000003.1
CTNC01000001.1
CTBO01000002.1


LUIE01000017.1
JYRX01000002.1
CTNB01000046.1
CTBN01000003.1


LUID01000024.1
JYRW01000014.1
CTNA01000004.1
CTBM01000003.1


LUIC01000116.1
JYRT01000085.1
CTMZ01000002.1
CTBK01000003.1


LUIB01000040.1
JYRQ01000034.1
CTMY01000004.1
CTBJ01000002.1


LUIA01000027.1
JYRM01000039.1
CTMX01000002.1
CTBI01000002.1


LUHZ01000025.1
JYRD01000017.1
CTMW01000004.1
CTBH01000003.1


LUHY01000038.1
JYRC01000016.1
CTMV01000003.1
CTBF01000004.1


LUHX01000025.1
JYQU01000020.1
CTMU01000003.1
CTBE01000004.1


LUHV01000033.1
JYQM01000015.1
CTMT01000004.1
CTBC01000002.1


LUHU01000040.1
JYQC01000008.1
CTMS01000002.1
CTBB01000002.1


LUHT01000028.1
JYQA01000030.1
CTMR01000004.1
CTBA01000002.1


LUHS01000024.1
JYPT01000005.1
CTMQ01000003.1
CTAZ01000003.1


LUHR01000036.1
JYPP01000050.1
CTMP01000002.1
CTAY01000001.1


LONA01000003.1
JYPO01000064.1
CTMO01000003.1
CTAX01000001.1


LKJI01000024.1
JYPM01000008.1
CTMN01000003.1
CTAW01000001.1


LKJE01000032.1
JUIT01000021.1
CTMM01000003.1
CTAV01000002.1


LKJD01000006.1
JRZW01000002.1
CTML01000002.1
CTAU01000001.1


LJJK01000144.1
JRZV01000001.1
CTMK01000002.1
CTAT01000003.1


LIOJ01000001.1
JRZU01000002.1
CTMJ01000003.1
CTAS01000002.1


LIOG01000016.1
JRZT01000030.1
CTMI01000002.1
CTAR01000002.1


LIOF01000021.1
JRZS01000015.1
CTMH01000003.1
CTAQ01000002.1


LIOB01000013.1
JRZR01000010.1
CTMG01000002.1
CTAP01000002.1


LINM01000004.1
JRZQ01000006.1
CTMF01000002.1
CTAO01000002.1


LINL01000011.1
JRZO01000062.1
CTME01000001.1
CTAN01000001.1


LINK01000002.1
JRZN01000054.1
CTMD01000003.1
CTAM01000004.1


LINJ01000020.1
JRZM01000003.1
CTMC01000004.1
CTAL01000003.1


LINF01000009.1
JRZL01000059.1
CTMB01000002.1
CTAK01000004.1


LINE01000010.1
JRZK01000010.1
CTMA01000002.1
CTAJ01000002.1


LINB01000005.1
SJRZJ01000012.1
CTLZ01000002.1
CTAI01000002.1


LIMZ01000030.1
SJRZI01000017.1
CTLY01000002.1
CTAH01000003.1


LIMV01000008.1
JRZH01000001.1
CTLX01000004.1
CTAG01000004.1


LIMU01000022.1
JRYU01000004.1
CTLW01000002.1
CTAF01000002.1


LIMT01000027.1
JRYT01000009.1
CTLV01000004.1
CTAE01000002.1


LIMN01000012.1
JRGW01000022.1
CTLU01000001.1
CTAD01000002.1


LIMM01000010.1
JRGV01000045.1
CTLT01000004.1
CTAC01000004.1


LIMH01000001.1
JRGU01000009.1
CTLS01000004.1
CTAB01000002.1


LIDY01000003.1
JRGT01000034.1
CTLR01000003.1
CQIE01000002.1


LHOM01000023.1
JRGS01000001.1
CTLQ01000001.1
CQHW01000002.1


LHOJ01000006.1
JRGR01000006.1
CTLP01000003.1
CQHV01000002.1


LHOH01000004.1
JHAI01000005.1
CTLO01000001.1
CQHU01000002.1


LHOG01000003.1
JHAH01000020.1
CTLN01000003.1
CQHS01000002.1


LHOF01000033.1
JHAG01000020.1
CTLM01000004.1
CQHR01000002.1


LHNW01000001.1
JHAF01000018.1
CTLL01000004.1
CQHQ01000002.1


LHNS01000017.1
JHAE01000013.1
CTLK01000002.1
CQHN01000002.1


LHNM01000038.1
FKJD01000009.1
CTLJ01000002.1
CQHJ01000001.1


LHNL01000010.1
FKJC01000004.1
CTLI01000002.1
CQHI01000002.1


LHNI01000015.1
FKJB01000003.1
CTLH01000004.1
CQHH01000002.1


LHNH01000007.1
CYID01000003.1
CTLG01000004.1
CQHG01000001.1


LHNG01000002.1
CYIC01000003.1
CTLF01000002.1
CQHF01000001.1


LHMT01000026.1
CYIB01000003.1
CTLE01000002.1
CQHE01000002.1


LHMS01000025.1
CYIA01000002.1
CTLD01000004.1
CQHD01000002.1


LHMA01000007.1
CYHZ01000003.1
CTLC01000006.1
CQHC01000002.1


LHLX01000009.1
CYHY01000003.1
CTLB01000002.1
CQHB01000002.1


LHLU01000004.1
CYHX01000003.1
CTLA01000002.1
CQHA01000001.1


LHLP01000001.1
CYHW01000002.1
CTKZ01000002.1
CQGZ01000001.1


LHLO01000016.1
CYHV01000002.1
CTKI01000002.1
CQGY01000002.1


LHLK01000019.1
CYHU01000003.1
CTKG01000001.1
CQGX01000002.1


LHLF01000020.1
CYHT01000003.1
CTKD01000002.1
CQGW01000002.1


LHLA01000001.1
CVMK01000002.1
CTKC01000002.1
CQGV01000002.1


LHKL01000042.1
CVMH01000002.1
CTKB01000004.1
CQGU01000002.1


LHKK01000034.1
CVKN01000003.1
CTKA01000003.1
CQGT01000001.1


LHKD01000036.1
CVKM01000005.1
CTJZ01000002.1
CQGS01000002.1


LHKC01000003.1
CVKK01000004.1
CTJY01000002.1
CQGR01000002.1


LHKA01000038.1
CVKJ01000005.1
CTJX01000003.1
CQGQ01000002.1


LHJU01000003.1
CVKH01000004.1
CTJW01000002.1
CQGP01000002.1


LHJJ01000028.1
CVKC01000002.1
CTJV01000003.1
CQGO01000002.1


LHJF01000017.1
CVKA01000004.1
CTJU01000005.1
CQGN01000002.1


LHIX01000004.1
CVJW01000001.1
CTJT01000002.1
CQGM01000002.1


LHIW01000017.1
CTQZ01000003.1
CTJS01000002.1
CQGL01000002.1


LHIR01000013.1
CTQY01000002.1
CTJR01000003.1
CQGK01000001.1


LHIQ01000047.1
CTQX01000004.1
CTJQ01000002.1
CQGJ01000002.1


LHIK01000014.1
CTQU01000002.1
CTJP01000002.1
CQGI01000001.1


LHIE01000015.1
CTQT01000003.1
CTJO01000004.2
CQGH01000002.1


LHID01000040.1
CTQS01000002.1
CTJN01000001.1
CQGG01000002.1


LHHK01000011.1
CTQR01000002.1
CTJM01000004.1
CIJW01000002.1


LHHB01000001.1
CTQQ01000001.1
CTJK01000003.1
CIJD01000002.1


LHGZ01000002.1
CTQP01000002.1
CTJJ01000002.1
CHJY01000001.1


LHGY01000001.1
CTQO01000002.1
CTIL01000002.1
CGGH01000001.1


LHGL01000047.1
CTQN01000002.1
CTIK01000003.1
CGDA01000002.1


LHGJ01000005.1
CTQM01000002.1
CTIJ01000003.1
CGCS01000001.1


LHGI01000006.1
CTQL01000098.1
CTII01000002.1
CGCQ01000002.1


LHGH01000003.1
CTQK01000004.1
CTIH01000002.1
CGCH01000002.1


LHFW01000031.1
CTQJ01000002.1
CTIG01000002.1
CFOA01000002.1


LHFV01000044.1
CTQI01000001.1
CTIF01000004.1
CFNX01000002.1


LHFU01000031.1
CTQH01000001.1
CTIE01000003.1
CFLD01000002.1


LHFT01000032.1
CTQG01000002.1
CTID01000002.1
BAKU01000002.1


LHFS01000022.1
CTQF01000003.1
CTIC01000002.1
AYVJ01000114.1


LHFP01000043.1
CTQE01000004.1
CTIB01000003.1
AYUQ01000108.1


LHFF01000013.1
CTQD01000002.1
CTIA01000004.1
AUXR01000008.1


LHEY01000021.1
CTQC01000001.1
CTHZ01000002.1
AUXE01000003.1


EHEX01000008.1
CTQB01000003.1
CTHY01000001.1
AUVE01000003.1


LHEW01000017.1
CTQA01000002.1
CTHX01000001.1
AUVD01000043.1


LHEV01000005.1
CTPZ01000003.1
CTHW01000001.1
AUQU01000045.1


LHER01000004.1
CTPY01000003.1
CTHV01000002.1
AUQT01000034.1


LHEQ01000025.1
CTPX01000004.1
CTHU01000002.1
AUQO01000062.1


LHEP01000049.1
CTPW01000002.1
CTHT01000004.1
AUQN01000039.1


LHEA01000005.1
CTPV01000002.1
CTHS01000002.1
AUQM01000038.1


LFGM01000013.1
CTPU01000005.1
CTHR01000002.1
AOXO01000096.1


LFDY01000028.1
CTPT01000001.1
CTHQ01000002.1
AOXD01000065.1


LFDW01000010.1
CTPS01000002.1
CTHP01000002.1
AOXC01000083.1


LFCC01000059.1
CTPR01000003.1
CTHO01000004.1
AJTU01000007.1


LDPA01000008.1
CTPQ01000002.1
CTHN01000002.1
AHVA01000018.1


LAPQ01000066.1
CTPP01000002.1
CTHM01000002.1
AHUZ01000018.1


LAPP01000078.1
CTPO01000002.1
CTHL01000002.1
AHUV01000085.1


LAPO01000058.1
CTPN01000002.1
CTHK01000002.1
AHUT01000031.1


LAPN01000091.1
CTPM01000005.1
CTHJ01000001.1
AHUS01000047.1


LAPM01000076.1
CTPL01000004.1
CTHI01000039.1
AERV01000023.1


LAPH01000042.1
CTPK01000003.1
CTHH01000002.1
ABAO01000006.1


LAPG01000091.1
CTPJ01000002.1
CTHG01000002.1
LUIV01000062.1









Also based on a publicly available software (e.g., BLAST), SEQ ID NO:1 is partially conserved (e.g., at least 99% sequence identity) in 48 Salmonella typhimurium strains listed by Genbank accession number in Table 3.









TABLE 3





Strains of Salmonella Typhimurium in


which SEQ ID NO: 1 is Partially Conserved


















LVGO01000006.1
LUJA01000002.1
LDYH01000006.1
AMEA02000013.1


LVGE01000003.1
LUIX01000003.1
JYPX01000009.1
AMDZ02000027.1


LVGD01000004.1
LFGR01000011.1
JTED01000004.1
AMDY01000216.1


LVGC01000003.1
LFGQ01000013.1
AUQV01000023.1
AMDX02000108.1


LVGB01000001.1
LFGP01000017.1
ATWR01000084.1
JRZX01000002.1


LVGA01000003.1
LFGN01000015.1
AMEH02000182.1
JRZP01000003.1


LVFZ01000005.1
LFDX01000009.1
AMEG02000055.1
AUQL01000040.1


LVFY01000001.1
LFCI01000010.1
AMEF02000044.1
LFGO01000009.1


LVFX01000003.1
LFCH01000028.1
AMEE02000031.1
LFDZ01000012.1


LVFU01000005.1
LFCG01000008.1
AMED02000059.1
LECA01000009.1


LUJD01000002.1
LECD01000013.1
AMEC02000055.1
LUHW01000058.1


LUJB01000005.1
LECC01000010.1
AMEB02000105.1
LECB01000012.1









Based on a publicly available software (e.g., BLAST), SEQ ID NO:1 is not found in the following non-Typhimurium salmonella strains:



Salmonella_enterica_serovar_Ohio_CFSAN001079



Salmonella_enterica_serovar_Newport_WA14881



Salmonella_enterica_serovar_Schwarzengrund_SL480



Salmonella_enterica_serovar_Gallinarum_28791



Salmonella_enterica_serovar_Thompson_2010K1863



Salmonella_enterica_serovar_Kentucky_CDC191



Salmonella_enterica_serovar_Typhi_BL196



Salmonella_enterica_serovar_Enteritidis_P125109



Salmonella_enterica_serovar_Agona_72A52



Salmonella_enterica_serovar_Saintpaul_JO2008



Salmonella_enterica_serovar_Heidelberg_SL476



Salmonella_enterica_serovar_Virchow_ATCC51955



Salmonella_enterica_serovar_Paratyphi_B_SARA62



Salmonella_enterica_serovar_MontevideoMDA09249507



Salmonella_enterica_serovar_Muenchen_2009K0951



Salmonella_enterica_serovar_B areilly_CFSAN000197



Salmonella_enterica_serovar_Virchow_SL491



Salmonella_enterica_serovar_Pullorum_19945



Salmonella_enterica_serovar_Dublin_SL1438



Salmonella_enterica_serovar_Stanley_060538


In another embodiment, a detection method is based on the identification of residues 749-1697 of Salmonella typhimurium ACCESSION CP007235 REGION: 658819 . . . 662133 (see SEQ ID NO:2 in Table 1). In another embodiment, a detection method is based on the identification of residues 755-1063 of Salmonella typhimurium ACCESSION CP007235 REGION: 658819 . . . 662133 (see SEQ ID NO:3 in Table 1). In some embodiments, the detection method incorporates unlabeled primers and labeled probes for the detection of Salmonella typhimurium.


Oligonucleotides


Oligonucleotides of the instant invention are set forth in SEQ ID NOs: 4-9.


Disclosed oligonucleotides can be used as primers for PCR amplification and as hybridization probes. Primers and probes are shown in Table 1.


The nucleic acid probes can contain a detectable label. In some embodiments, the probe comprises a reporter-quencher combination as employed in a double-stranded probe, a TAQMAN™ probe, a molecular beacon probe, a SCORPION™ probe, a dual hybridization probe, or an ECLIPSE™ probe. In some embodiments, a double-stranded probe comprises two completely or partially complementary strands. In some embodiments, one strand of the double-stranded probe comprises a reporter on the 5′ end and the other strand comprises a quencher on the 3′ end such that when the two strands hybridize, the reporter and quencher face each other and the quencher quenches the fluorescence emitted by the reporter. During PCR, the strands separate, allowing the reporter to fluoresce and to be detected. In some embodiments, each strand of the double-stranded probe includes a reporter at one end (e.g., the 5′ end) and a quencher at the other end (e.g., the 3′ end). When the two strands hybridize with each other, the reporter from the first strand is in close proximity with the quencher of the second strand such that fluorescence quenching occurs. During PCR, the strands separate, allowing the reporter to fluoresce and to be detected. In an embodiment, the probe is a double-stranded probe as described in U.S. Pat. No. 9,194,007, which is incorporated by reference in its entirety herein. In an embodiment, a reporter-quencher pair used in a double-stranded probe is 6-FAM and Iowa Black® FQ.


III. METHODS

The oligonucleotides can be used in a method for selectively detecting the presence of Salmonella typhimurium in a sample. In an embodiment, the method begins by providing a reaction mixture comprising a suitable primer pair for amplification of residues 749-1697, or a portion thereof, of SEQ ID NO:2. In some embodiments, the reaction mixture comprises a primer pair for amplification of a sequence 95%, 97%, or 99% homologous to SEQ ID NO:2. In some embodiments, the reaction mixture comprises a primer pair for amplification of a sequence of SEQ ID NO:2 or a portion thereof.


In certain embodiments, the reaction mixture comprises a primer pair for amplification of residues 755-1063, or portions thereof, of SEQ ID NO:3. In some embodiments, the reaction mixture comprises a primer pair for amplification of a sequence 95%, 97%, or 99% homologous to SEQ ID NO:3. In some embodiments, the reaction mixture comprises a primer pair for amplification of a sequence of SEQ ID NO:3 or a portion thereof. In some embodiments, the primer pair for amplification of the nucleic acid region of SEQ ID NO:3 comprises SEQ ID NO:4 and SEQ ID NO:5.


In some embodiments, the method further comprises a probe for the nucleic acid region to be detected. In certain embodiments, the probe comprises a detectable label. In some embodiments, the probe is a single-stranded probe comprising SEQ ID NO:6, SEQ ID NO:7, SEQ ID NO:8, or SEQ ID NO:9. In some embodiments, each probe is labeled with a reporter on one end (e.g., the 5′ end) and a quencher on the other end (e.g., the 3′ end). In some embodiments, the probe is a double-stranded probe comprising SEQ ID NO:6 and SEQ ID NO:7 (e.g., SEQ ID NO:6 can hybridize to SEQ ID NO:7) with each strand having a reporter on one end (e.g., the 5′ end) and a quencher on the other end (e.g., the 3′ end).


The next step of the method comprises performing PCR amplification (e.g., real-time PCR) of the nucleic acids of the sample using the reaction mixture. In some embodiments, PCR amplification is performed in partitions (e.g, droplets). Methods and compositions for partitioning a solution are described, for example, in published patent applications WO 2012/135259, WO 2014/117088, WO 2010/036352, and U.S. Pat. No. 9,156,010, the entire content of each of which is incorporated by reference herein.


In the last step of the method, the presence of Salmonella typhimurium is selectively detected by detecting the amplified nucleic acids. In some embodiments, the detecting step comprises sequencing the amplified nucleic acids.


IV. KITS

In another aspect, kits for detecting Salmonella typhimurium in a sample according to the methods described herein are provided. In some embodiments, a kit comprises a primer pair as described herein. In some embodiments, the kit further comprises probes as described herein. In some embodiments, the kit further comprises assay components including, but not limited to, a lysis reagent, a DNA polymerase, dNTPs, a buffer, a negative control, and a positive control. In some embodiments, the kit further comprises instructions for carrying out the methods described herein.


V. EXAMPLES
Example 1—Comparison of Salmonella typhimurium Assay of the Instant Invention to Salmonella Spp. Assay

In this example, the Salmonella typhimurium assay of the instant invention was compared to a commercially available Salmonella spp. Assay. In the experiment, eleven Salmonella serovars that are most relevant for the food industry were tested with the Salmonella typhimurium assay of this disclosure and with the iQ-Check Salmonella spp. II Assay (Bio-Rad). The eleven Salmonella strains were streaked on a TCS Petri dish and allowed to grow for 24 hr at 37° C. Individual colonies were then picked, diluted in 500 μL sterile water and 5 μL were tested with each assay using the Bio-Rad CFX96 Touch™ Real-Time PCR Detection System. For the Salmonella typhimurium assay, the double-stranded probe comprised SEQ ID NOs 6 and 7. Each strand of the double-stranded probe was labeled with 6-FAM on the 5′ end and Iowa Black™ FQ on the 3′end. The double-stranded probe was synthesized by Integrated DNA Technologies using phosphoramidite chemistry. Results are shown in Table 4.









TABLE 4







Comparison of Assays










Bio-Rad iQ-Check Salmonella spp. II assay

Salmonella Typhimurium assay















Target
Internal

Target
Internal



Serovars
Cq
control Cq
Result
Cq
control Cq
Result
















Negative Ctrl
N/A
32.84
Negative
N/A
32.49
Negative


Positive Ctrl
31.72
32.24
Positive
31.95
31.78
Positive



Typhimurium

19.69
34.60
Positive
19.36
33.43
Positive



Monophasic Typhimurium

18.35
N/A
Positive
18.08
34.2
Positive



Enteritidis

20.34
32.72
Positive
N/A
32.15
Negative



Infantis

20.86
32.40
Positive
N/A
31.78
Negative


Virchow
19.71
33.28
Positive
N/A
32
Negative


Hadar
21,20
32.29
Positive
N/A
31.89
Negative


Paratyphi B Java
20.24
33.27
Positive
N/A
31.91
Negative


Livingstone
20.84
33.21
Positive
N/A
32.38
Negative


Kentucky
18.67
34.26
Positive
N/A
32.17
Negative


Dublin
21,24
32.68
Positive
N/A
31.99
Negative


Newport
20.23
32.67
Positive
N/A
31.98
Negative









The results shown in Table 4 illustrate that only typhimurium is detected by the Salmonella Typhimurium assay. The results also show that the sensitivities of both assays are identical and that the Salmonella typhimurium assay can be used as a primary screening assay or as a confirmatory, serotyping assay.


Example 2—Assay Selectivity

This example illustrates assay selectivity of the instant invention. One-hundred and nine Salmonella enterica subsp. enterica serovars and Salmonella enterica subspecies (in italics in Table 4) were tested with the Salmonella typhimurium assay. The same method and probes as in Example 1 were used in this experiment. The organisms tested are shown in Table 5.









TABLE 5





Selectivity

















Abaetetuba



Aberdeen



Adelaïde



Agama



Albany



Anatum




arizonae*




Bambylor



Bareilly



Berta



Betioky



Blegdam



Blockley




bongori




Braenderup



Brandenburg



Bredeney



Budapest



California



Cerro



Carrau



Canoga



Crossness



Cubana




Choleraesuis





diarizonae*




Dalhem



Derby



Dublin



Emek



Duisberg



Enteritidis



Fischerkietz



Ferruch



Give



Gaminara



Gallinarum



Glostrup



Grumpensis



Grabow



Goldgoast



Havana



Hadar



Guinea



Havanna




houtenae*




Illinois



Heidelberg



Indiana




indica*




Inverness



Johannesburg



Infantis



Kentucky



Kirkee



Kottbus



Kedougou



Lomita



Livingstone



Manica



London



Miami



Minnesota



Maregrosso



Mbandaka



Muenchen



Montevideo



Moscow



Napoli



Nienstedten



Naestved



Newport



Nottingham



Oranienburg



Ouakam



Okatie



Ohio



Phoenix



Panama



Paratyphi B**



Paratyphi B java



Postdam



Poona



Puttin



Quentin



Rostock



Salamae



Rubislaw



Senftenberg



Saint Paul



Schwarzengrund



Singapore



Sheffield



Sundsvall



Springs



Strasbourg



Taksony



Tallahassee



Tournai



Tenessee



Thompson



Treforest



Tranoroa



Utrecht



Virchow



Zuerich



Yoruba



Wayne



Worthington










Of the organisms listed in Table 5, all but Paratyphi B were not detected with the assay. The results illustrate that the Salmonella typhimurium assay is highly selective for Salmonella typhimurium.


Example 3—Assay Exclusivity

This example illustrates assay exclusivity of the instant invention. Thirty-nine non-Salmonella bacteria were tested with the Salmonella typhimurium assay. The same method and probe as in Example 1 was used in this experiment. The bacteria tested are tabulated in Table 6. None of the bacteria listed in Table 6 were detected by the Salmonella typhimurium assay, illustrating assay exclusivity.









TABLE 6





Exclusivity


















Acinetobacter baumanii





Aeromonas hydrophila





Aeromonas hydrophila/caviae





Bacillus licheniformis





Bacillus cereus





Campylobacter jejuni





Campylobacter coli





Campylobacter lari





Campylobacter upsaliensis





Citrobacter freundii





Cronobacter sakazakii





Enterobacter cloacae





Enterobacter pyrinus





Enterobacter sakazakii





Enterobacter aerogenes





Enterobacter asburiae





Enterobacter amnigenus





Enterobacter cowanii





Enterococcus faecium





Escherichia coli





Escherichia hermanii





Hafnia alvei





Klebsiella oxytoca





Klebsiella pneumoniae





Listeria monocytogenes





Micrococcus luteus





Pantoea agglomerans





Proteus mirabilis





Pseudomonas fluorescens





Pseudomonas aeruginosa





Raoultella terrigena





Serratia marcescens





Shigella flexneri





Shigella sonnei





Staphylococcus aureus





Staphylococcus internmedius





Staphylococcus xylosus





Staphylococcus epidermidis





Yersinia enterocoloitica











Example 4—Assay Specificity

This example illustrates assay specificity of the instant invention. Seventy-nine Salmonella typhimurium serovars were tested with the Salmonella typhimurium assay. The same method and probe as in Example 1 was used in this experiment. The bacteria tested are tabulated in Table 7. All of the bacteria listed in Table 7 were detected by the Salmonella typhimurium assay, illustrating assay specificity.









TABLE 7







Specificity














Antigenic

Primary

Strain number
Strain number


Serovar
formula
Comment
source
Origin
(Bio-Rad Library)
(Other Library)






Typhimurium

1,4,[5],12:i:1,2

Anses
Brine
002
no Anses: 38.09



Typhimurium

1,4,[5],12:i:1,2

Anses
Beef meat
003
no Anses: 442.09



Typhimurium

1,4,[5],12:i:1,2

Anses
Pork (crépine
004
no Anses: 447.09






de porc)





Typhimurium

1,4,[5],12:i:1,2

Anses
Lamb with
005
no Anses: 591.09






sauce





Typhimurium

1,4,[5],12:i:1,2

Anses
Stuffed quail
006
no Anses: 695.09



Typhimurium

1,4,[5],12:i:1,2

Anses
Culture from
007
no Anses: 839.09






lamb feces





Typhimurium

1,4,[5],12:i:1,2

Anses
Environment
008
no Anses: 838.09






(Duck)





Typhimurium

1,4,[5],12:i:1,2

Anses
Culture from
009
no Anses: 553.11






horse feces





Typhimurium

1,4,[5],12:i:1,2

Anses
White pepper
010
no Anses: 564.11



Typhimurium

1,4,[5],12:i:1,2

Anses
Hoki filet with
011
no Anses: 708.11






cream





Typhimurium

1,4,[5],12:i:1,2

Anses
Pigeon viscera
012
no Anses: 781.11



Typhimurium

1,4,[5],12:i:1,2

Anses
Compost
013
no Anses: 792.11



Typhimurium

1,4,[5],12:i:1,2

Anses
Environmental
014
no Anses: 835.11






(Chicken)





Typhimurium

1,4,[5],12:i:1,2

Anses
Streaky ham
015
no Anses: 840.11



Typhimurium

1,4,[5],12:i:1,2

Anses
Whole quail
016
no Anses: 845.11



Typhimurium

1,4,[5],12:i:1,2

Anses
Spareribs
017
no Anses: 880.11



Typhimurium

1,4,[5],12:i:1,2

Anses
Culture from
018
no Anses: 886.11






swine feces





Typhimurium

1,4,[5],12:i:1,2

Anses
Raw milk
019
no Anses: 907.11






(cow)





Typhimurium

1,4,[5],12:i:1,2

Anses
Sausage
020
no Anses: 976.11



Typhimurium

1,4,[5],12:i:1,2

Anses
Tomato filling
021
no Anses: 977.11



Typhimurium

1,4,[5],12:i:1,2

Anses
Stuffed
022
no Anses: 979.11






potatoes





Typhimurium

1,4,[5],12:i:1,2

Anses
Fish meal
023
no Anses: 985.11



Typhimurium

1,4,[5],12:i:1,2

Anses
Pet food
043
no Anses: 1175.11



Typhimurium

1,4,[5],12:i:1,2

Anses
Foie gras
030
no Anses: 119.11






(Liver)





Typhimurium

1,4,[5],12:i:1,2

ADRIA
Milk powder
081
ADRIA no4





Development






Typhimurium

1,4,[5],12:i:1,2

ADRIA
Pasteurized
082
ADRIA no13





Development
liquid egg





Typhimurium

1,4,[5],12:i:1,2

ADRIA
Pasteurized
083
ADRIA no206





Development
liquid egg





Typhimurium

1,4,[5],12:i:1,2

ADRIA
Egg yolk
084
ADRIA no472





Development






Typhimurium

1,4,[5],12:i:1,2

ADRIA
Pasteurized
085
ADRIA no776





Development
liquid egg





Typhimurium

1,4,[5],12:i:1,2

ADRIA
Ready-to-eat
086
CIP 58.58





Development






Typhimurium

1,4,[5],12:i:1,2

ADRIA
Foie (Liver)
087
ADRIA no19





Development






Typhimurium

1,4,[5],12:i:1,2

ADRIA
Raw ground
088
ADRIA no22





Development
meat





Typhimurium

1,4,[5],12:i:1,2

ADRIA
Ready-to-eat
089
ADRIA no167





Development






Typhimurium

1,4,[5],12:i:1,2

ADRIA
Chipolatas
090
ADRIA no193





Development
sausages





Typhimurium

1,4,[5],12:i:1,2

ADRIA
Chipolatas
091
ADRIA no830





Development
sausages





Typhimurium

1,4,[5],12:i:1,2

ADRIA
Merguez
092
ADRIA no911





Development
sausages





Typhimurium

1,4,[5],12:i:1,2

ADRIA
Chipolatas
093
ADRIA no987





Development
sausages





Typhimurium

1,4,[5],12:i:1,2

ADRIA
Meat (pâté)
094
ADRIA no4874





Development






Typhimurium

1,4,[5],12:i:1,2

ADRIA
Frozen meat
095
A00C003





Development






Typhimurium

1,4,[5],12:i:1,2

ADRIA
Frozen meat
096
A00C004





Development






Typhimurium

1,4,[5],12:i:1,2

ADRIA
Frozen beef
097
A00C059





Development
trim





Typhimurium

1,4,[5],12:i:1,2

ADRIA
ground beef
098
A00C060





Development






Typhimurium

1,4,[5],12:i:1,2

ADRIA
Pork
106
Ad1070





Development






Typhimurium

1,4,[5],12:i:1,2

ADRIA
Pork
107
ST325





Development






Typhimurium

1,4,[5],12:i:1,2

ADRIA
Pork
108
ST1





Development






Typhimurium

1,4,[5],12:i:1,2

ADRIA
Pork
109
ST394





Development






Typhimurium

1,4,[5],12:i:1,2

ADRIA
Pork
110
ST719





Development






Typhimurium

1,4,[5],12:i:1,2

ADRIA
Pork
111
ST11





Development






Typhimurium

1,4,[5],12:i:1,2

ADRIA
Liquid egg
113
JES411





Development






Typhimurium

1,4,[5],12:i:1,2

ADRIA
Beef trim
116
Ad913





Development






Typhimurium

1,4,[5],12:i:1,2

ADRIA
Pork
118
Ad1249





Development






Typhimurium

1,4,[5],12:i:1,2

ADRIA
pork (crépine)
119
Ad1338





Development






Typhimurium

1,4,[5],12:i:1,2

ADRIA
ground meat
120
Ad1410





Development






Typhimurium

1,4,[5],12:i:1,2

ADRIA
Liquid egg
121
Ad1484





Development






Typhimurium

1,4,[5],12:i:1,2

ADRIA
Drinking
122
Ad1546





Development
water from








trough





Typhimurium

1,4,[5],12:i:1,2

ADRIA
salmon with
123
Ad1603





Development
vegetables





Typhimurium

1,4,[5],12:—:—
non motile
ADRIA
Tiramisu
124
Ad1333




variant
Development






Typhimurium

1,4,[5],12:—:1,2
monophasic
ADRIA
Hen
125
Ad1335




variant
Development






Typhimurium

1,4,[5],12:i:—
monophasic
ADRIA
Pork specialty
126
Ad1334




variant
Development






Typhimurium

1,4,[5],12:i:1,2

Anses
Environmental
160
2002LSAL00347






(Quail)





Typhimurium

1,4,[5],12:i:1,2

Anses
Environmental
161
2016LSAL02607






(goose)





Typhimurium

1,4,[5],12:i:—
monophasic
Anses
Environmental
162
2009LSAL04410




variant

(Pork)





Typhimurium

1,4,[5],12:—:1,2
monophasic
Anses
Environmental
163
2010LSAL01759




variant

(Gallus gallus-








hen)





Typhimurium

1,4,[5],12:i:—
monophasic
Anses
Environmental
164
2011LSAL04681




variant







Typhimurium

1,4,[5],12:i:—
monophasic
Anses
Environmental
165
2012LSAL04635




variant

(Turkey)





Typhimurium

1,4,[5],12:i:1,2

Anses
Environmental
166
2013LSAL00987






(Gallus gallus)





Typhimurium

1,4,[5],12:i:—
monophasic
Anses
Environmental
167
2014LSAL00857




variant

(Bovine)





Typhimurium

1,4,[5],12:i:—
monophasic
Anses
Pork meat
168
2011LSAL06561




variant







Typhimurium

1,4,[5],12:i:—
monophasic
Anses
Veal meat
169
2012LSAL05317




variant







Typhimurium

1,4,[5],12:i:—
monophasic
Anses
Turkey meat
170
2014LSAL02635




variant







Typhimurium

1,4,[5],12:i:—
monophasic
Anses

Gallus gallus

171
2014LSAL03913




variant

meat





Typhimurium

1,4,[5],12:i:—
monophasic
Anses
Poultry Feed
172
2011LSAL04983




variant







Typhimurium

1,4,[5],12:i:—
monophasic
Anses
cattle feed
173
2012LSAL03407




variant







Typhimurium

1,4,[5],12:i:—
monophasic
Anses
animal blood
174
2012LSAL03874




variant

products





Typhimurium

1,4,[5],12:i:—
monophasic
Anses
cattle feed
175
2015LSAL00792




variant







Typhimurium

1,4,[5],12:i:—
monophasic
Anses
beef meat
176
2013LSAL02030




variant

(carcass)





Typhimurium

1,4,[5],12:i:—
monophasic
Anses
pork
177
2015LSAL01461




variant

(carcass)





Typhimurium

1,4,[5],12:i:—
monophasic
Anses
turkey
178
2013LSAL03886




variant

(carcass)





Typhimurium

1,4,[5],12:i:—
monophasic
Anses
chicken
179
2016LSAL00194




variant

(carcass)









It is understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims. All patents, patent applications, internet sources, and other published reference materials cited in this specification are incorporated herein by reference in their entireties. Any discrepancy between any reference material cited herein or any prior art in general and an explicit teaching of this specification is intended to be resolved in favor of the teaching in this specification. This includes any discrepancy between an art-understood definition of a word or phrase and a definition explicitly provided in this specification of the same word or phrase.

Claims
  • 1. A method of selectively detecting the presence of Salmonella typhimurium in a sample comprising nucleic acids, the method comprising: (a) providing a reaction mixture comprising (i) a suitable primer pair for amplification of an amplicon polynucleotide, which amplicon polynucleotide consists of a nucleic acid at least 95% homologous to SEQ ID NO:3 and (ii) the nucleic acids of the sample;(b) performing PCR amplification of the nucleic acids of the sample using the reaction mixture of step (a) to form the amplicon polynucleotide primed by the primer pair; and(c) selectively detecting the presence of Salmonella typhimurium by detecting the amplicon polynucleotide.
  • 2. The method of claim 1, wherein the reaction mixture comprises a primer pair for amplification of an amplicon polynucleotide at least 97% homologous to SEQ ID NO:3.
  • 3. The method of claim 1, wherein the reaction mixture comprises a primer pair for amplification of a polynucleotide at least 99% homologous to SEQ ID NO:3.
  • 4. The method of claim 1, wherein the reaction mixture comprises a primer pair for amplification of an amplicon polynucleotide consisting of SEQ ID NO:3.
  • 5. The method of claim 1, wherein the primer pair comprises SEQ ID NO:4 and SEQ ID NO:5.
  • 6. The method of claim 5, wherein the reaction mixture further comprises a probe for the amplicon polynucleotide.
  • 7. The method of claim 6, wherein the probe comprises a detectable label.
  • 8. The method of claim 6, wherein the probe comprises SEQ ID NO:6, SEQ ID NO:7, SEQ ID NO:8, or SEQ ID NO:9.
  • 9. The method of claim 6, wherein the probe is selected from the group consisting of a double-stranded probe, a molecular beacon probe, and a dual hybridization probe.
  • 10. The method of claim 1, wherein the detecting the presence of Salmonella typhimurium comprises sequencing the amplicon polynucleotide.
  • 11. The method of claim 1, wherein step (b) is performed in partitions.
CROSS-REFERENCE TO RELATED APPLICATION

This application is a national phase application under 35 U.S.C. 371 claiming priority to PCT/IB2017/000921, filed Jun. 15, 2017, which claims the benefit of U.S. Application 62/351,130 filed on Jun. 16, 2016, the content of each of which is hereby incorporated by reference in its entirety for all purposes.

PCT Information
Filing Document Filing Date Country Kind
PCT/IB2017/000921 6/15/2017 WO
Publishing Document Publishing Date Country Kind
WO2017/216635 12/21/2017 WO A
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Related Publications (1)
Number Date Country
20190177773 A1 Jun 2019 US
Provisional Applications (1)
Number Date Country
62351130 Jun 2016 US