Edward O. Stapley

Avermectins, New Family of Potent Anthelmintic Agents: Producing Organism and Fermentation

The avermectins are a complex of chemically related agents which exhibit extraordinarily potent anthelmintic activity. They are produced by a novel species of actinomycete, NRRL 8165, which we have named Streptomyces avermitilis. The morphological and cultural characteristics which differentiate the producing organism from other species are described. The avermectins have been identified as a series of macrocyclic lactone derivatives which, in contrast to the macrolide or polyene antibiotics, lack significant antibacterial or antifungal activity. The avermectin complex is fully active against the gastrointestinal nematode Nematospiroides dubius when fed to infected mice for 6 days at 0.0002% of the diet. Fermentation development, including medium modification and strain selection, resulted in increasing the broth yields from 9 to 500 μg/ml. Images

Phosphonomycin, a New Antibiotic Produced by Strains of Streptomyces

Phosphonomycin is a newly discovered antibiotic produced by streptomycetes. It is effective, when administered by the oral route, to mice infected with Gram-positive or Gram-negative microorganisms. The antibiotic is bactericidal and inhibits cell-wall synthesis.

Cephamycins, a New Family of β-Lactam Antibiotics I. Production by Actinomycetes, Including Streptomyces lactamdurans sp. n

A number of actinomycetes isolated from soil were found to produce one or more members of a new family of antibiotics, the cephamycins, which are structurally related to cephalosporin C. The cephamycins were produced in submerged fermentation in a wide variety of media by one or more of eight different species of Streptomyces, including a newly described species, S. lactamdurans. These antibiotics exhibit antibacterial activity against a broad spectrum of bacteria which includes many that are resistant to the cephalosporins and penicillins.

Cefoxitin, a Semisynthetic Cephamycin Antibiotic: Resistance to Beta-Lactamase Inactivation

Cefoxitin is a new, cephalosporin-like antibiotic which is highly resistant to hydrolysis by β-lactamase. Ninety-one cultures were selected either for their general resistance to cephalosporin antibiotics or for their ability to produce β-lactamase. Some of these cultures were resistant to cefoxitin. The capacity of each of the 91 strains to hydrolyze cefoxitin with β-lactamase was determined. Only seven of the cultures degraded the antibiotic as determined by a general assay for β-lactamase. Several others were able to hydrolyze cefoxitin after enzyme was induced by low concentrations of the antibiotic. The role of the constitutive and inducible enzyme in bacterial resistance to the antibiotic was investigated. Enzymatic destruction of cefoxitin was found to be an important factor contributing to bacterial resistance. However, the complete and rapid degradation of cefoxitin is not essential to resistance since one strain, Enterobacter cloacae 1316, hydrolyzed the antibiotic very slowly but was able to grow unaffected in the presence of cefoxitin. The presence of the enzyme is not necessarily sufficient to confer resistance since another culture, Klebsiella D535, readily hydrolyzed the antibiotic but was susceptible to it.

Fosfomycin: Laboratory Studies

Fosfomycin, a nontoxic broad-spectrum antibiotic, different in structure from all previously described antibiotics, acts selectively by inhibiting cell wall formation. It was overlooked during many years of screening because of antagonism by culture medium ingredients and frequent occurrence of resistant mutants. It is effective in many because the neutralizing substances are not present and resistant mutants of most species are avirulent. Fosfomycin has favorable pharmacologic characteristics. It is not cross resistant, does not show antagonism, and has been used successfully in combinations. An insoluble calcium salt is used in oral formulation and a sodium salt for parenteral administration. Overall success rates of 86% were reported with 1,000 patients in Spain and 79% in Japan.

Cephamycins, a New Family of β-Lactam Antibiotics: Antibacterial Activity and Resistance to β-Lactamase Degradation

The susceptibility to some cephalosporin antibiotics and to cephamycin C, a member of a new family of β-lactam antibiotics, was evaluated for 466 cultures representing 11 different genera or species of gram-negative clinical isolates. The susceptibility of 39 gram-negative cultures known to produce β-lactamase was also determined. The β-lactamase activity of a representative group of the clinical isolates and the 39 enzyme producers was studied with the cephalosporins (cephalothin and cephaloridine) and cephamycin C as substrates and was related to the in vitro disc susceptibility to these same antibiotics. The significant resistance to β-lactamase displayed by the cephamycins is reflected in the kinetics of enzyme activity (Km and Vmax) that are reported for the cephalosporins and the cephamycins. Resistance to β-lactamase is probably one of the reasons that many cephalosporin-resistant cultures are susceptible to cephamycin C.

Hydroxylation of Steroids, Principally Progesterone, by a Strain of Aspergillus Ochraceus

The ability of certain species of Aspergillus to transform progesterone to lla-hydroxyprogesterone has been reported by the Upjohn (7) and Squibb groups (4) and has been observed in these laboratories. We find that the lla-hydroxy derivative usually is transformed further to 6/3,1 ladihydroxyprogesterone. Some cultures, however, were found to introduce secondary hydroxyls to lla-hydroxyprogesterone at positions other than carbon 6. These findings as well as data characterizing the lla-hydroxy and 6/2,1 la-dihydroxy derivatives of progesterone will be reported later (2). In the present communication are reported our studies of progesterone transformation by a strain of A. ochraceus and particularly the effect of Zn++ on introduction of the 6/?-hydroxyl to lla-hydroxyprogesterone.

Cephamycins, a New Family of β-Lactam Antibiotics. III. In Vitro Studies

Cephamycin A was found to be more active in vivo than cephamycin B. In comparison with cephamycin C, cephamycin A was more active against gram-positive organisms but less active against gram-negative organisms. Given subcutaneously, cephamycin C had good in vivo gram-negative activity, comparing favorably with cephalothin and cephaloridine against cephalosporin-susceptible organisms. In general, against the gram-negative organisms, it was more active than cephalothin or cephalosporin C and about as active as cephaloridine. In addition, cephamycin C protected mice against β-lactamase-producing Proteus cultures, including clinically isolated strains. The compound is remarkably nontoxic. Cephamycin C was detected in the serum and recovered from the urine of treated mice to about the same extent as cephaloridine. Like cephaloridine and cephalosporin C, cephamycin C must be excreted mainly by glomerular filtration, because the use of probenecid did not enhance the therapeutic effectiveness nor concentrations of these agents in the sera of treated mice.

Cefoxitin, a semisynthetic cephamycin antibiotic: in vivo evaluation.

Cefoxitin, 3-carbamoyloxymethyl-7-α-methoxy-7-[2-(2-thienyl)acetamido]-3-cephem-4- carboxylic acid, a semisynthetic cephamycin antibiotic shown to have broad-spectrum activity in vitro, is active also in vivo against a wide variety of bacteria including penicillin-resistant staphylococci. It is, however, particularly effective against gram-negative organisms including strains of indole-positive Proteus against which cephalothin and cephaloridine are ineffective. When cefoxitin is given subcutaneously, concentrations in mouse blood, urine, and other tissues are higher than those seen for cephalothin. Higher concentrations in the blood and greater therapeutic efficacy are achieved with cefoxitin when it is given with probenecid. For this reason it is believed that cefoxitin is excreted mainly by way of the renal tubules. The data indicate that cefoxitin has potential as a therapeutically useful antibiotic.

Similarity of Albomycin and Grisein.

Albomycin and grisein were found to be composed of four antibiotically active substances of which A, a strongly active component, and D, a very weakly active component, appear to be stable to purification, while C has been observed to break down continually with concomitant appearance of more A. On the basis of published reports and of studies made in our laboratories, it is concluded that albomycin and grisein are chemically very similar and identical with respect to antimicrobial activity (5).