Factors affecting the in vitro activity of cefoperazone against the Bacteroides fragilis group

Differences in susceptibilities of species of the Bacteroides fragilis group to several beta-lactam antibiotics: indole production as an indicator of resistance

Clinical isolates of the members of the Bacteroides fragilis group differ markedly in their susceptibilities to a variety of beta-lactam antibiotics, including cefoperazone, moxalactam, cefotaxime, cefoxitin, cefamandole, cephalothin, cefazolin, and carbenicillin, as determined by dilution techniques. The minimum concentrations required to inhibit at least 50% of the strains tested (MIC50) for the entire B. fragilis group were lowest with moxalactam and cefoxitin, 4 and 8 micrograms/ml, respectively, whereas the MIC90S of cefoperazone, cefotaxime, moxalactam, cefoxitin, and carbenicillin were equivalent (64 micrograms/ml); the MIC90S of cefamandole, cephalothin, and cefazolin were higher. Indole-positive members of the group (B. ovatus, B. thetaiotaomicron, and B. uniformis) were significantly more resistant to every antibiotic tested than were indole-negative members (B. fragilis, B. distasonis, and B. vulgatus). In a 6-month survey of clinical laboratory data, indole-positive strains comprised 40% of the B. fragilis group isolates and 22% of all Bacteroides isolates; B. fragilis was the most common species isolated (23%). The increased use of second-generation and the introduction of third-generation cephalosporins may dictate that clinical microbiology laboratories routinely identify members of the B. fragilis group as to species or, alternatively, test for indole production in addition to performing more extensive susceptibility testing.

Antimicrobial activity, pharmacokinetics, adverse reactions, and therapeutic indications of cefoperazone

Cefoperazone is a parenteral cephalosporin antibiotic that is pending approval by the U. S. Food and Drug Administration. Compared to most other cephalosporins cefoperazone has a greatly expanded spectrum of bactericidal activity that encompasses most aerobic gram-positive bacteria except enterococci, most aerobic gram-negative bacteria, including a majority of Pseudomonas aeruginosa strains, and a number of pathogenic anaerobic bacteria. Its long serum half-life, approximately two hours, permits a twelve hourly dosing schedule. No dosage modification is required in patients with renal insufficiency, and only minor modification is needed in patients with hepatic insufficiency or biliary obstruction. Clinical trials have established cefoperazone's efficacy in lower respiratory tract infections, urinary tract infections, and a variety of other bacterial infections. Adverse reactions have been infrequent, and few serious reactions have been identified. Cefoperazone is a promising new agent for the treatment of gram-negative bacillary and polymicrobial infections, especially in settings that require empiric therapy.