Epithienamycins-novel beta-lactams related to thienamycin. I. Production and antibacterial activity.

The epithienamycins are cell wall active antibiotics structurally related to N-acetylthienamycin. We have found forty-three isolated of Streptomyces flavogriseus which are capable of producing members of the epithienamycin family. Six major epithienamycin components, and xanthomycin, have been isolated from fermentation broth. Fermentation conditions can be varied to enrich for certain members of the epithienamycin family. All six components show activity in vitro versus a broad spectrum of bacterial species. The weight potencies vary 27 fold from the most active to least active.

L-lysine epsilon-aminotransferase involved in cephamycin C synthesis in Streptomyces lactamdurans.

In Streptomyces lactamdurans, the precursor of the alpha-aminoadipoyl side-chain of cephamycin C is L-lysine. In this regard, streptomycetes differ strikingly from the fungi, which produce alpha-aminoadipic acid during the synthesis, rather than the breakdown, of L-lysine. Studies using a cell-free system showed that an aminoadipic acid. The product of this reaction was trapped and subsequently purified by ion-exchange chromatography. Thin-layer chromatography, spectrophotometry, and amino acid oxidase digestion studies identified the reaction product as L-1-piperideine-6-carboxylate, implying enzymatic removal of the epsilon amino group of L-lysine. This enzymatic activity (E.C. 2.6.1.36; L-lysine: 2-oxoglutarate 6-aminotransferase) is highly unusual and was previously conclusively demonstrated only in the genus Flavobacterium. In S. lactamdurans, the specific activity of this enzyme reaches a peak early in the fermentation (approximately 20 h) and decreases as the antibiotic begins to appear.

Cefoxitin and cephamycins: microbiological studies.

The cephamycins are a family of beta-lactam antibiotics that are produced by actinomycetes and are structurally similar to the cephalosporins. They are characterized by the presence of a 7-alpha-methoxyl group, which confers unusually high resistance to beta-lactamases. Cefoxitin, the first semisynthetic cephamycin, is resistant to almost all beta-lactamases. Cefoxitin retains the 3-carbamoyl group of cephamycin C and thus has excellent metabolic stability. Cefoxitin is bactericidal and almost devoid of any inoculum effect. Active against many cephalothin-resistant gram-negative bacteria, cefoxitin demonstrates a very broad spectrum that includes indole-positive Proteus and many strains of Serratia. In contrast to that of the cephalosporins, cefoxitin's spectrum of activity against anaerobic pathogens includes Bacteroides fragilis. The therapeutic effectiveness of cefoxitin in experimental infections in mice confirms the excellent characteristics of this semisynthetic cephamycin and indicates that it should be a very valuable agent for treatment of bacterial infections.

Thienamycin, a new beta-lactam antibiotic. I. Discovery, taxonomy, isolation and physical properties.

A new beta-lactam antibiotic, named thienamycin, was discovered in culture broths of Streptomyces MA4297. The producing organism, subsequently determined to be a hitherto unrecognized species, is designated Streptomyces cattleya (NRRL 8057). The antibiotic was isolated by adsorption on Dowex 50, passage through Dowex 1, further chromatography on Dowex 50 and Bio-Gel P2, and final purification and desalting on XAD-2. Thienamycin is zwitterionic, has the elemental composition C11H16N2O4S (M.W. = 272.18) and possesses a distinctive UV absorption (lambda max = 297 nm, epsilon = 7,900). Its beta-lactam is unusually sensitive to hydrolysis above pH8 and to reaction with nucleophiles such as hydroxylamine, cysteine and, to a lesser degree, the primary amine of the antibiotic itself. The latter reaction results in accelerated inactivation at high antibiotic concentrations.

Effect of fosfomycin on the fecal microflora of man.

Use of broad-spectrum antibiotics is known to cause changes in the intestinal microflora of man. The present study was initiated to determine the effect of oral fosfomycin calcium on several groups of microorganisms indigenous to the gut. Data from this double-blind study indicate that 2 g of fosfomycin given daily in four divided doses for 28 days increased the incidence of soft stools. No significant changes in numbers of staphylococci or Candida were observed during treatment. Although there was no significant change in total coliforms, the numbers of E. coli decreased markedly from 10(5) to 10(2) organisms/g feces. Concurrent with this decrease, the Klebsiella-Enterobacter counts increased from 10(3) to 10(6) organisms/g feces. Two weeks posttreatment the E. coli and the Klebsiella-Enterobacter counts approached pretreatment levels. These observations are similar to those reported for ampicillin. During the course of treatment when the E. coli dropped precipitously the few surviving E. coli still were suceptible to fosfomycin as determined by an agar diffusion disc test.

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.

Cefoxitin, a semisynthetic cephamycin antibiotic: susceptibility studies.

Cefoxitin, 3-carbamoyloxymethyl-7-alpha-methoxy-7-[2-(2-thienyl)acetamido]-3-cephem-4- carboxylic acid, is a new semisynthetic cephamycin with broad antibacterial activity. It is highly active against gram-negative microorganisms including indole-positive Proteus and Serratia strains, which are ordinarily reistant to the cephalosporins. Cefoxitin is also highly active against many strains of Escherichia coli and Proteus mirabilis which are resistant to the cephalosporins. Furthermore, E. coli and Klebsiella strains which are susceptible to the cephalosporins are generally more susceptible to the cephamycin analog. The susceptibility of the gram-positive bacteria falls well within the effective range of the antibiotic for gram-negative organisms, but cefoxitin is less active than cephalothin or cephaloridine. As is the case with the cephalosporins, strains of Pseudomonas and group D streptococci are resistant to cefoxitin. Changes in pH, inoculum density, and growth medium have no significant effect on the activity of the antibiotic.

Cefoxitin, a semisynthetic cephamycin antibiotic: in vivo evaluation.

Cefoxitin, 3-carbamoyloxymethyl-7-alpha-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.

Cefoxitin, a semisynthetic cephamycin antibiotic: resistance to beta-lactamase inactivation.

Cefoxitin is a new, cephalosporin-like antibiotic which is highly resistant to hydrolysis by beta-lactamase. Ninety-one cultures were selected either for their general resistance to cephalosporin antibiotics or for their ability to produce beta-lactamase. Some of these cultures were resistant to cefoxitin. The capacity of each of the 91 strains to hydrolyze cefoxitin with beta-lactamase was determined. Only seven of the cultures degraded the antibiotic as determined by a general assay for beta-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.

Cephamycins, a new family of beta-lactam antibiotics: antibacterial activity and resistance to beta-lactamase degradation.

The susceptibility to some cephalosporin antibiotics and to cephamycin C, a member of a new family of beta-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 beta-lactamase was also determined. The beta-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 beta-lactamase displayed by the cephamycins is reflected in the kinetics of enzyme activity (K(m) and V(max)) that are reported for the cephalosporins and the cephamycins. Resistance to beta-lactamase is probably one of the reasons that many cephalosporin-resistant cultures are susceptible to cephamycin C.

Cephamycins, a new family of beta-lactam antibiotics. 3. In vitro studies.

Cephamycins A, B, and C are naturally produced cephalosporin-type antibiotics. Although A and B were found to be more active than C against gram-positive organisms, they were not so active against such strains as are cephalosporin C or the semisynthetic antibiotics cephaloridine and cephalothin. Against gram-negative organisms, cephamycin C was more active than A or B and, in general, was as active as the cephalosporins. In addition, cephamycin C was active in vitro against clinically isolated strains resistant to the cephalosporins, such as Proteus, Providencia, and Escherichia coli. The in vitro antibacterial activity of cephamycin C, cephalothin, and cephaloridine is primarily bactericidal. A 10,000-fold increase in inoculum of a strain of Proteus mirabilis resulted in 200-fold or greater increases in minimal inhibitory and minimal bactericidal end points of cephalothin and cephaloridine, but only 10- and 16-fold increases, respectively, for cephamycin C. After 15 passages through antibiotic-containing broths, during which time a culture of E. coli showed an increase in minimal inhibitory concentrations of streptomycin of >1,000-fold, end points for cephamycin C increased 4-fold, for cephalothin, 1.5-to 6-fold, and for cephaloridine, 128-fold.

Cephamycins, a new family of beta-lactam antibiotics. IV. In vivo 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 beta-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.

Cephamycins, a new family of beta-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.

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.