Antibiotic substances

Abstract

The antibiotic gardimycin and process for producing said antibiotic by fermentation of strains belonging to the genus Actinoplanes.

Description

The present invention refers to the production and the isolation of a new family of antibiotic substances obtained by fermentation of strains belonging to the genus Actinoplanes. These substances will hereafter be referred to as metabolite A, metabolite B and metabolite C: metabolite B is also named gardimycin.

As stated above the antibiotic substances are produced by cultivation of fermenting strains belonging to the genus Actinoplanes. These strains were isolated from soil samples collected at the localities Temossi (Italy) and Garbadi Bridge (India). Our collection numbers are A/6353 for the strain isolated from the Italian soil sample and A/10889 for the strain isolated from the Indian soil sample: both have been deposited and made part of the stock culture collection of ATCC where they were assigned the numbers 31048 and 31049 respectively.

In the preparation of the new antibiotic substances the selected organism is cultivated under aerobic conditions in an aqueous nutrient medium containing a source of carbon, a source of nitrogen and inorganic salts. Ordinarily the strain is precultured in a shake flask, until substantial antibiotic activity is present, then the culture is used to inoculate jar fermentors containing a nutrient fermentative medium. Cultivation is continued at 25.degree.-35.degree. C. under aerobic conditions for a time sufficient to produce a substantial antibiotic level. During this time microbiological assays are carried out by the agar diffusion method to control the concentration of the antibiotic substance produced. Sarcina lutea is used as the test organism.

The so obtained antibiotic activity can be isolated from the fermentation broth by conventional procedures, such as, for instance, by extraction with an organic solvent in which the antibiotic activity is soluble and which is immiscible with the aqueous medium. For this purpose, organic solvents selected from lower alkanols of 3 to 6 carbon atoms and (C.sub.1-4)-lower halogenated hydrocarbons may advantageously be employed.

The organic phase is separated from the aqueous medium, concentrated to small volume and allowed to stand for 10-15 hours at low temperature until a precipitate forms, which is recovered by filtration. Paper chromatography on Whatman paper No. 1 and thin layer chromatography on silicagel of the obtained curde product, and subsequent microbiological development (Nicolaus et al., I1 Farmaco, Ed. Prat., 8, 350-370, 1961) on Staphylococcus aureus as the detecting system, indicate the presence of at least two active components, which for identification purposes, are named metabolite A and metabolite B, the latter being produced in higher amounts than the former. These two components have different R.sub.f values which vary depending on the nature of the eluting system. Metabolites A and B may be purified and isolated as the pure compounds by means of usual techniques, such as, for instance, by several countercurrent extractions in a predetermined solvent system in which the two antibiotic substances have different partition coefficients. During this step metabolite B is recovered as the monosodium salt, which can in turn be transformed into other salts with alkali or alkali earth metals, or into the corresponding free acid, by means of common operations.

The mother liquors deriving from the butanol extract are poured into an inert, non-polar organic solvent, as, for instance, light petroleum, and a further precipitate forms.

Chromatographic investigations and microbiological developments carried out as above indicate that the obtained solid essentially consists of a single product, which is different from metabolites A and B owing to the different R.sub.f values in the same eluting system: for identification purposes it is named metabolite C. The chromatographic patterns of the three metabolites A, B and C will be hereinafter reported.

Metabolite A, metabolite B (hereinafter referred to as gardimycin) as well as its salts with alkali and alkali earth metals and metabolite C show good antibacterial in vitro and in vivo activities. More particularly, gardimycin exhibits an outstanding in vitro antimicrobial action especially against gram-positive bacteria at concentration levels between 1 and 50 .mu.g/ml, as it results from the following table, reporting the minimal concentration of antibiotic substance which inhibits the growth of various pathogenic microorganisms.

TABLE 1______________________________________ Minimal inhibitoryStrain concentration (.mu.g/ml)______________________________________Staphylococcus aureus ATCC 538 50Micrococcus flavus ATCC 10240 1Streptococcus faecalis ATCC 10541 50Streptococcus haemolyticus C 203 2Diplococcus pneumoniae UC 41 50Clostridium perfringens ISS 30543 2Neisseria gonorrheae ATCC 9826 20______________________________________

Another favorable characteristic of the antibiotic substance gardimycin is that it is active against clinically isolated Streptococcus strains.

TABLE 2______________________________________ Minimal inhibitoryStrain concentration (.mu.g/ml)______________________________________Streptococcus haemolyticus 2078 1Streptococcus haemolyticus 2087 1Streptococcus viridans 2057 5Streptococcus viridans 2085 2______________________________________

Furthermore, as stated above, gardimycin displays also a very interesting in vivo activity against experimental infections in mice caused by pathogenic bacteria of the genus Diplococcus and Streptococcus. The hereinbelow reported table shows the ED.sub.50 values of gardimycin against experimental infections provoked by Streptococcus haemolyticus C 203 and Diplococcus pneumoniae UC 41.

TABLE 3______________________________________Strain ED.sub.50 mg/Kg______________________________________Streptococcus haemolyticus C 203 0.75Diplococcus pneumoniae UC 41 30______________________________________

These favorable antimicrobial properties are coupled with a very low toxicity as the LD.sub.50 value of the antibiotic gardimycin is higher than 1000 mg/Kg i.p. and about 2000 mg/Kg i.v.

DESCRIPTION OF THE PRODUCING STRAINS

Description of strain A/6353

The strain grows well on several agar media. On oat meal agar the colonies, which are of about 5 mm. in diameter, have indented contours, slight radial furrows and a central depression. Aerial mycelium is always absent. Sporangia form abundantly on oat meal agar, glycerol asparagine agar and Czapek glucose agar, showing different shape and size depending on the medium.

On oat meal agar they have regular contours and a shape varying from spherical to oval. The sporangia size is in the range 15-25.mu.. The spores are motile and spherical with a diameter of 1.5-2.mu.. A yellow-amber soluble pigment is produced in several media.

Description of Actinoplanes A/10889

The strain grows well on various nutrient agars. The surface is opaque and usually rough to wrinkled. Aerial mycelium is usually absent, however in some media rudiments of aerial mycelium are observed. At the microscopic examination the vegetative mycelium is slightly branched with a diameter of .apprxeq.1.mu.. The sporangia form moderately only on calcium malate agar and are globose with irregular surface often lobate, with diameter ranging from 7.0 to 12.0.mu.. After rupture of the sporangial wall it is possible to observe sporangial release. The subspherical spores are motile (1.0 to 1.5.mu. diameter).

A comparison of some morphological characteristics of the two strains is shown in Table 4.

TABLE 4______________________________________ Strains A/10889 A/6353______________________________________Sporangia formed only on Ca formed abundantly on malate agar several agars; but Size: 7 .times. 12 m.mu. variable in size and shape. On oat meal agar the size is 15-25 m.mu.Spores subspherical spherical (1 to 1.5 .mu.m) (1.5-2 m.mu.)Aerial mycelium rudimentary always absentSoluble pigment absent yellow-amber pigment present on some agars______________________________________

Table 5 reports the cultural characteristics of Actinoplanes A/6353 and Actinoplanes A/10889 cultivated on various standard media suggested by Shirling and Gottlieb (Intern. J. Syst. Bact. 16, 313-340, 1966) and other media recommended by Waksman (The Actinomycetes, vol. II, The Williams and Wilkins Co., 1961). The cultural characteristics were determined after 6 to 14 days of incubation at 30.degree. C.

TABLE 5__________________________________________________________________________The number of some of the culture media refers to those given by Shirlingand Gottlieb Cultural CharacteristicsCulture Medium A/10889 A/6353__________________________________________________________________________Medium n. 2 Abundant growth, wrinkled surface, Abundant growth, slightly wrinkled(Yeast extract-malt agar) amber light orange to light amberMedium n. 3 Moderate growth, smooth, opaque, Abundant growth, with smooth and thin(Oatmeal agar) cream to orange at edges surface, light orange. Some sporangia, hight yellow soluble pigmentMedium n. 4 Moderate growth, smooth surface, deep Abuntant growth with smooth surface(Inorganic salts-starch agar) orange orange. Some sporangia. Canary yellow soluble pigmentMedium n. 5 Moderate growth, smooth surface, Abundant growth with smooth surface,(Glycerol-asparagine agar) orange light orange. Abundant production of pigment. Canary yellow soluble pigmentMedium n. 6 Scanty growth, rough surface, dark Moderate growth with smooth surface(Peptone-yeast exctract-iron, agar) brown, with brown pigment orangeMedium n. 7 Abundant growth, crusty surface, Abundant growth with smooth surface,(Tyrosine agar) coffee colored rose amber. Good production of Weakly brown pigment sporangia. Rose amber soluble pigmentOatmeal agar (according to Abundant growth, crusty surface, Abundant growth, with smooth surface,Waksman) orange. light orange to topaze yellow Traces of rudimentary aerial mycelium Good production of big sporangia, - yellow soluble pigmentHickey and Tresner's agar Abundant growth, wrinkled surface, Abundant growth with smooth surface rose light brown amber Abundant production of sporangiaCzapek glucose agar Poor growth, smooth surface, light Abundant growth with smooth and thin orange surface, orange Abundant production of sporangia Traces of rudimentary aerial myceliumGlucose asparagine agar Abundant growth, crusty surface, deep Abundant growth with smooth surface orange orange. Some sporangiaNutrient agar Moderate growth, crusty surface, Abundant growth with smooth surface, orange to light brown orangePotato agar Abundant growth, wrinkled surface, Abundant growth, with smooth surface orange to light brown. amber Traces of rudimentary aerial myceliumBennett's agar Abundant growth, wrinkled surface, Abundant growth with crusty surface light orange. light orangeCalcium malate agar Moderate growth, crusty surface, Scarce growth with smooth surface. cream to light orange. colorless. Some sporangiaSkim milk agar Abundant growth, wrinkled surface, Abundant growth with slightly crusty deep orange. surface, deep orange yellow soluble pigmentCzapek agar Poor growth, crusty surface, light Scarce growth light orange orange Moderate production of sporangiaEgg agar Abundant growth, smooth surface, Abundant growth, with smooth surface, - orange light creme. Moderate production of sporangiaPeptone glucose agar Very scant growth, smooth surface, Abundant growth, with wrinkled surface, hyaline deep orangeAgar Very scanty growth, thin and smooth Very scanty growth thin and smooth. hyaline ColorlessLoeffler serum Very scanty growth, smooth surface, Scarce growth, light orange light orange to amberPotato Scanty growth, wrinkled surface, Scarce growth, wrinkled, light orange orange__________________________________________________________________________

The most convenient temperature for development of the colonies was found to range from about 18.degree. to about 42.degree. C., the optimum temperature being from about 28.degree. C. to about 37.degree. C.

Table 6 reports the utilisation of carbon sources examined according to the method of Pridham and Gottlieb.

TABLE 6______________________________________Carbon Utilization GrowthCarbon source A/10889 A/6353______________________________________Inositol - +Fructose + +Rhamnose + +Mannitol + -Xylose + +Raffinose - -Arabinose + +Cellulose - -Salicin + -Sucrose + -Mannose + +Lactose + -Glucose (positive control) + +______________________________________

Table 7 reports the physiological characteristics of the two strains.

TABLE 7______________________________________Physiological characteristicsTest A/10889 A/6353______________________________________Starch hydrolysis positive positiveH.sub.2 S formation positive negativeMelanin production positive negativeTyrosine hydrolysis positive negativeCasein hydrolysis negative positiveCa-malate hydrolysis negative negativeLitmus milk coagulation negative negativeLitmus milk peptonization negative negativeNitrate reduction positive negativeGelatin liquefaction positive negative______________________________________

The two strains A/6353 and A/10889 because of their global sporangia, motile spores and colony morphology are ascribed to the genus Actinoplanes. However, they are clearly different from each other on the basis of their growth pattern on different agars, production or non-production of soluble pigment, carbon utilization pattern, and physiological characteristics. In particular, A/6353 shows a very limited ability to hydrolize glycosidic bonds, including sucrose which is utilized by all the species of Actinoplanes so far described. A/10889 produces a rudimentary aerial mycelium, seldom found in Actinoplanes species. The two strains are also easily distinguishable from all the Actinoplanes species so far known. For these reasons, strain A/6353 and strain A/10889 are recognized as new species of Actinoplanes and are given the names Actinoplanes liguriae ATCC 31048 and Actinoplanes garbadinensis ATCC 31049.

EXAMPLE 1

Production of the antibiotic, isolation and separation of the various metabolities

For producing the antibiotic activities the strain Actinoplanes Garbadinensis ATCC 31049 is aerobically pre-cultured in a nutrient medium until substantial antibiotic activity is present. As an example a shake flask culture may have the following composition in g/l.

______________________________________Meat extract 3.0Yeast extract 10.0Calcium carbonate 4.0Starch 25.0Tap water q.s. to 1000 ml.______________________________________

The flasks are shaken for about 24 hours at about 28.degree.-30.degree. C. and then the pre-cultures (one liter) are used to inoculate jar fermentors each containing 10 liters of the following nutrient medium:

______________________________________Meat extract 40 gPeptone 40 gYeast extract 10 gSodium chloride 25 gSoybean meal 100 gGlucose 500 gCalcium carbonate 50 gTap. water q.s. to 10 liters______________________________________

The fermentation batches are incubated aerobically under stirring at 28.degree.-30.degree. C. At intervals the antibiotic activity is assayed microbiologically by the agar diffusion method using Sarcina lutea as the test organism. The maximum activity is reached after 96-120 hours of fermentation.

The fermentation broth is adjusted at pH 8.0 and then filtered using Hyflo super-cell as a filter aid. The mycelium is discarded and the filtrate is extracted with an amount of butanol corresponding to about 1/2 of its volume. The organic phase is separated from the aqueous one, and, after washing with acidic water (pH. 4.0) is concentrated to about 1/10 of its original volume and allowed to stand for 10-12 hours at a temperature of 3.degree.-6.degree. C. A crude precipitate forms, which is collected on filter, washed with butanol and dried under vacuum at room temperature: yield 3.0 g. Chromatographic assays on Whatman paper No. 1 or on silica-gel of this crude precipitate, and subsequent microbiological development of the spots by using Staphylococcus aureus as the detecting system, indicate the presence of two components which are defined as metabolite A and metabolite B (gardimycin): they have different R.sub.f values which depend on the nature of the employed eluting system.

The crude mixture is further purified by dissolving in about 30 ml. of water. The resulting solution is dialyzed for about 16 hours against distilled water and then concentrated to small volume under vacuum. 1.5 Grams of rough antibiotic substance are obtained, which still is a mixture of metabolite A and gardimycin. The two antibiotic substances are separated and purified by several countercurrent extractions, by relying upon the different partition coefficients of component A and gardimycin in the predetermined solvent system. The employed solvent system consists of butanol: sodium-potassiumphosphate buffer M/15 pH 7.2: hexane in the ratio 1:1:0.1; the partition coefficients in this medium of metabolite A and gardimycin are 0.3 and 0.8 respectively. After 100 extractions, 0.450 g. of gardimycin as its monosodium salt are obtained.

The mother liquors from the butanol extract after precipitation of the mixture of metabolites A and B are further concentrated to small volume and then poured into an excess of light petroleum. A precipitate readily forms, which is recovered by filtration. Chromatographic assays carried out under the same conditions as before indicate that this fraction consists of one product which has different R.sub.f value from metabolites A and B in the same eluting systems. This fraction is named metabolite C.

The different chromatographic-patterns of the three metabolites in the various eluting systems are reported in the following table:

__________________________________________________________________________Chromatographic patterns of metabolite A, metabolite B (gardimycin) andmetabolite C.Chromatography on Whatman paper No. 1Visualization of the spots by microbiological development R.sub.f valueson Staphylococcus aureus Metabolite B ELUTING SYSTEM Metabolite A (gardimycin)* Metabolite C__________________________________________________________________________(1) Butanol saturated with phosphate buffer M/15 pH 6.0 0.00 0.15 0.85(2) Butanol saturated with water containing 2% of p-toluenesulfonic acid 0.75 0.80 0.95(3) Butanol saturated with water containing 2% of ammonium hydroxide 0.15 0.10 0.85(4) Phosphate buffer M/15 pH. 6.0 saturated with butanol 0.65 0.80 0.00(5) 20% aqueous solution of sodium chloride 0.00 0.80 0.00(6) Butanol:methanol:water = 40:10:20 with 0.75% of methyl orange 0.70 0.65 0.90(7) Butanol:methanol:water = 40:10:20 0.85 0.60 0.90(8) Acetone:water = 1:1 0.80 0.80 0.65(9) Ethyl acetate saturated with water 0.00 0.00 0.75Thin-layer chromatography on silicagel.Visualization of the spots by sulfuric acid and vanillineand microbiological development on Staphylococcus aureusELUTING SYSTEMAmmonium hydroxide:ethanol:water = 1:8:1 0.30 0.70 0.00__________________________________________________________________________ *Metabolite B is tested as the monosodium salt?

EXAMPLE 2

By operating as described in Example 1 the strain Actinoplanes Liguriae ATCC 31048 is aerobically cultivated for 130-170 hours at about 28.degree.-30.degree. C. 1.4 Grams of antibiotic activity are obtained, which are a mixture of metabolite A and metabolite B (gardimycin). The existence of the two metabolites has been detected by means of the same chromatographic assays reported in Example 1. The purification of the obtained antibiotic activity and the separation of the two metabolites has been achieved as in Example 1. 0.2 Grams of gardimycin as the monosodium salt are obtained.

Chemico-physical properties of gardimycin as the monosodium salt

Gardimycin (as the monosodium salt) is an amorphus white powder with amphoteric character. It has an isoelectric point of 4.2 which was determined by electrofocalization. Upon strong hydrolysis in hydrochloric acid 6 N at 120.degree. in a closed funnel for 16 hours and chromatographic analysis of the hydrolysis products it was possible to evidence the following amino-acids: valine, serine, glycine, glutamic acid, isoleucine, leucine and alanine. After alkaline hydrolysis with barium hydroxide at 110.degree. in a closed funnel for 15 hours and chromatographic analysis of the hydrolysis products it is possible to evidence the presence of tryptophane. The above mentioned amino-acids are present in the following ratio:

______________________________________Amino-acids Approximate ratio______________________________________Valine 2Serine 1Glycine 2Glutamic acid 1Isoleucine 2Leucine 1Alanine 1Tryptophan 1______________________________________ Moreover, the analysis of the products resulting from the acidic hydrolysis reveals the presence of further amino-acids of undetermined structure, some of them containing sulfur. Furthermore, gardimycin (as the monosodium salt) is chracterized by the following properties:

(1) Melting point: 260.degree. C. (decomposition)

(2) Molecular weight: 2005-2168

(3) Elemental analysis: C=48.7-48.6%; H=6.7-6.6%; N=11.8-12.2%; S=5.3-5.5%; Na=1.1%; H.sub.2 O=3.6-3.3%

(4) U.V. absorpion bands:

In each of the below outlined solvent systems, gardimycin shows the following values:

______________________________________Solvent .lambda..sub.max (m.mu.) E.sub.1.sup.1% cm.______________________________________methanol 273 (shoulder) 280 26 299 24sodium hydroxide 0.1N 273 (shoulder) 279 26 288 22hydrochloric acid 0.1N 273 (shoulder) 279 26 288 22phosphate buffer 273 (shoulder)pH. 7.38 279 24 288 20______________________________________

The complete picture of the spectrum is given in FIG. 1 of U.S. Pat. application Ser. No. 596,702, filed July 17, 1975.

(5) Infrared spectrum: Characteristic absorption bands in nujol have been observed at the following frequencies: (cm.sup.-1): 3280, 2920-2840 (nujol); 1650, 1520, 1455 (nujol), 1375 (nujol), 1260, 1045, 990, 720. The complete picture of the spectrum is given in FIG. 2 of U.S. Pat. application Ser. No. 596,702, filed July 17, 1975.

(6) Specific rotation: [.alpha.].sub.D.sup.25 =-44.degree. (c=0.5% dimethylformamide)

(7) Solubility:

Soluble in water, aqueous sodium bicarbonate, diluted aqueous solutions of alkali hydroxides, hot methanol, dimethylformamide, dimethylsulfoxide, glacial-acetic acid. Insoluble in diluted mineral acids, benzene, acetone, chloroform, carbon tetrachloride, (C.sub.2-6)-aliphatic alkanols, tetrahydrofuran.

(8) Characteristic reactions:

______________________________________Fehling positiveTollens positiveKMnO.sub.4 positiveH.sub.2 SO.sub.4 conc. positiveNinhydrin negativeFeCl.sub.3 negativeMillion negativeSchiff negativeMaltol negative______________________________________

(9) Ionizable functions:

An ionizable function is potentiometrically evidenced with pK.sub.a =7.1 (water) and pK.sub.a =8.5 (methylcellosolve:water:16:4).

(10) Furthermore, starting from the monosodium salt of gardimycin it is possible to prepare the following derivatives:

(a) Gardimycin free acid: 1.0 g of gardimycin monosodium salt is dissolved in 150 ml. of water. The resulting solution is brought to pH 2.5 by adding aqueous 10% hydrochloric acid and is then extracted two times with 75 ml. of butanol saturated with water. The butanol extracts are collected and concentrated in vacuo at 45.degree. C. to a volume corresponding to 1/20 of the initial volume. After standing at 4.degree. C. for 12 hours a precipitate forms, which is collected, washed with light petroleum and dried in vacuo at 40.degree.-45.degree. C. 0.950 Grams of product are obtained which decomposes between about 250.degree. and about 300.degree. C.

(b) Gardimycin disodium salt: 1.0 g. of gardimycin monosodium salt is dissolved in 150 ml. of water and the pH of the resulting solution is brought to 9.6 by adding N/10 sodium hydroxide. The solution is then lyophilized. 0.900 Grams of product are obtained melting at 250.degree. C.

(c) Gardimycin calcium salt: 0.3 g. of gardimycin monosodium salt are dissolved in 20 ml. of water and the resulting solution is slowly added, under stirring, with several portions of a saturated solution of calcium chloride until a complete precipitation is reached. The obtained solid id filtered, dried in vacuo and dissolved in 10 ml. of acetone. After pouring into 200 ml. of diethylether a precipitate forms, which is filtered and dried in vacuo at 40.degree.-45.degree. C. 0.2 Grams of product are obtained which decomposes at 330.degree.-40.degree. C.

Claims

1. A biologically pure culture of the microorganism strain Actinoplanes garbadinensis ATCC 31049, said culture being capable of producing Gardimycin antibiotic in a recoverable quantity upon aerobic fermentation in an aqueous nutrient medium containing assimilable sources of carbon, nitrogen and inorganic salts.

2. A biologically pure culture of the microorganism strain Actinoplanes liguriae ATCC 31048, said culture being capable of producing Gardimycin antibiotic in a recoverable quantity upon aerobic fermentation in an aqueous nutrient medium containing assimilable sources of carbon, nitrogen and inorganic salts.