Substrate inhibition of beta-lactamases, a method for predicting enzymatic stability of cephalosporins

Cefoxitin therapy in aerobic, anaerobic, and mixed aerobic-anaerobic infections

Cefoxitin, a new beta-lactamase-resistant cephamycin, was evaluated in 66 patients for clinical and bacteriological efficacy, serum levels, tolerance, and toxicity. Seventeen patients had soft tissue infections, 14 had pleuropulmonary infections, 14 had intraabdominal infections, 13 had pelvic infections, and 8 had urinary tract infections. Among the 66 patients, 62 were cured and 4 could not be evaluated. Twelve patients had hospital-acquired infections, 31 had underlying disease, and 45 required a surgical procedure. Isolates included 116 aerobic and 72 anaerobic bacteria. Cefoxitin was more active than cephalothin against facultative and obligate anaerobic gram-negative organisms isolated from these patients. Mean peak cefoxitin levels in sera were 52 micrograms/ml after a 2-g infusion and 30 micrograms/ml after a 1-g infusion. Phlebitis occurred in two patients, eosinophilia in one, rash in two, vasculitis in one, and transient rises in SGOT and SGPT in two. Cefoxitin appears to be a safe and effective drug for the treatment of many aerobic, anaerobic, and mixed aerobic-anaerobic infections.

Beta-lactamase stability and antibacterial activity of cefmenoxime (SCE-1365), a novel cephalosporin

Cefmenoxime, a new cephalosporin antibiotic, has been shown to be stable to a Staphylococcus aureus penicillinase and R plasmid-mediated type I and type IV penicillinases. It was also resistant to hydrolysis by most cephalosporinases, but was susceptible to hydrolysis by a Proteus vulgaris beta-lactamase. Cefmenoxime was active against cephaloridine-resistant species, except Pseudomonas aeruginosa, which was moderately resistant to cefmenoxime. Cefmenoxime was an inducer of P. vulgaris beta-lactamase biosynthesis, but 1 microgram or more of the drug per ml, which inhibits most of the clinical isolates of P. vulgaris, was required for the production of detectable amounts of the enzyme. Cefmenoxime was a strong competitive inhibitor of beta-lactamases of Enterobacter cloacae, Citrobacter freundii, P. aeruginosa, and Serratia marcescens, but it did not inhibit penicillinases in spite of its resistance to hydrolysis.

Procedure for assay of tobramycin in serum containing moxalactam

Moxalactam was examined as a substrate for 11 beta-lactamases. Hydrolysis was shown only with the beta-lactamase from Bacillus cereus, a nonpathogenic bacterium. Tobramycin was assayed in tobramycin-moxalactam mixtures by using this beta-lactamase.

Role of a cefoxitin-inducible beta-lactamase in a case of breakthrough bacteremia

Development of resistance during therapy with cefamandole contributes to treatment failure. A simple cefoxitin disk test was recently described which detects a cefamandole-active inducible beta-lactamase not otherwise detectable with cefamandole as the inducer. A case of breakthrough Enterobacter bacteremia due to selection of a resistant subpopulation is reported in an immunocompromised patient. The use of this simple disk test in selected clinical cases is advocated.

Emergence of resistance to cefamandole: possible role of cefoxitin-inducible beta-lactamases

Selection of resistance to cefamandole has been observed, and the drug has failed to protect animals lethally infected with certain Enterobacteriaceae that appeared to be highly susceptible in vitro. Using spectrophotometric assays, some of these organisms were found to produce beta-lactamases highly active against cefamandole. Cefoxitin, a poor enzyme substrate, was found to be superior to both cephalothin and cefamandole in induction of these enzymes. A simple disk induction test was developed and used to examine 147 Enterobacteriaceae for production of these beta-lactamases. The enzymes were found in 69% of cephalothin-resistant, cefamandole-susceptible strains and in only 3% of strains susceptible to both cephalothin and cefamandole. They were most prevalent among isolates of Enterobacter, indole-positive Proteus, and Serratia. Since selection of resistance and therapeutic failures have occurred most often among these genera, the relationship between presence of inducible enzymes and outcome of therapy should be examined further in humans.

Lack of correlation between beta-lactamase production and susceptibility to cefamandole or cefoxitin among spontaneous mutants of Enterobacteriaceae

A large number of cultures of gram-negative bacteria were examined for their susceptibility to various concentrations of cefamandole, cefoxitin, carbenicillin, and nalidixic acid. Heterogeneity of susceptibility was demonstrated in individual cultures to all of these antibiotics. Resistant clones isolated from cefamandole or cefoxitin plates were examined for beta-lactamase production. Approximately 13% of 262 resistant clones acquired the ability to produce a beta-lactamase. Examination of the substrate profile of the beta-lactamases from some of these clones revealed no change in the specific activity of these enzymes for cefamandole, cephaloridine, or compound 87/312 as compared with their parental enzymes. This study clearly shows that some resistant clones do not produce beta-lactamases, whereas some susceptible strains produced significant amounts of these enzymes. We conclude from these findings that little correlation exists between beta-lactamase production and decreased susceptibility to cefamandole or cefoxitin. The results suggest the possibility that characteristics other than beta-lactamase production may be responsible for resistance in Enterobacteriaceae.

beta-lactamase stability of HR 756, a novel cephalosporin, compared to that of cefuroxime and cefoxitin

The stability to beta-lactamase hydrolysis of HR 756, a new cephalosporin antibiotic, was compared to the beta-lactamase stability of cefoxitin and cefuroxime. HR 756, cefoxitin, and cefuroxime were not hydrolyzed by Richmond type I, III, IV, and V beta-lactamases. Antibacterial activity of HR 756 correlated well with resistance to beta-lactamase hydrolysis except against Pseudomonas aeruginosa. HR 756, cefoxitin, and cefuroxime inhibited type I beta-lactamases, but not type III, IV, or V enzymes. HR 756 was the most active inhibitor.

Transition state structures of a dipeptide related to the mode of action of beta-lactam antibiotics

The tetrahedral adducts formed during nucleophilic attack by a hydroxyl ion on the carbonyl carbon of a model dipeptide, glycylglycine, were studied by modified-intermediate-neglect-of-differential-overlap molecular orbital calculations. This dipeptide is taken to represent the D-alanyl-D-alanine terminus of the polypeptides involved in the cross-linking transpeptidation reaction of peptidoglycan in bacterial cell walls. It was found that nucleophilic attack on one face of the carbonyl carbon leads to a transition intermediate species structurally similar to that afforded by the bicyclic nucleus of penicillins and cephalosporin antibiotics. The results support the concept that the beta-lactam antibiotics, which are known to inhibit various bacterial cell wall enzymes, may act as transition state analogs. Also, the structure formed from nucleophilic attack on the so-called alpha face of the dipeptide is more similar to the antibiotic structures than is that from attack on the opposite face. In agreement with other types of experiments, the results suggest that the alpha face may be the one approached by a nucleophile in the receptor site(s) of the appropriate cell wall enzymes.

Results of a clinical trial of cefoxitin, a new cephamycin antibiotic

Cefoxitin was administered intravenously to 143 patients, 67% of whom were seriously ill. The rate of cure or improvement was 93%. The study was conducted in two phases; the first was an open, controlled clinical comparison of cefoxitin and cephalothin. In this phase, 28 patients received cefoxitin and 29 received cephalothin. In the second phase, cefoxitin alone was used for the treatment of an additional 115 patients. Twenty bacteremic patients treated with cefoxitin were cured or improved in 95% of cases. The infecting organism was eradicated in all bacteremic patients. All of 14 anaerobic or predominantly anaerobic infections were cured or improved. The infecting anaerobic organism was eliminated in 86% of the cases. Twenty-five patients infected by cephalothin-resistant, cefoxitin-susceptible gram-negative rods were cured. Three patients each with infective endocarditis and osteomyelitis were cured. The incidence of adverse experiences was: 1.4% drug eruption; 2% each asymptomatic serum transaminase elevation and leukopenia; and 2.5% asymptomatic eosinophilia. The incidence of severe thrombophlebitis was 5%. No permanent or serious adverse reactions were encountered. Although the numbers of patients in some categories were too small to permit statistical evaluation, I feel that cefoxitin may be a useful new antibiotic for treatment of infections caused by cehalothin-resistant bacteria and by anaerobic organisms.