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Susceptibility of intestinal anaerobes to new beta-lactam antibiotics
Abstract:
In vitro susceptibility of 473 isolates of anaerobic bacteria derived from patients hospitalized for treatment of abdominal trauma was tested against third-generation cephalosporins--moxalactam, cefotaxime, ceftizoxime, cefmenoxime--and a penicillin--N-formimidoyl thienamycin--by serial agar dilution method in the anaerobic glove box. There were 208 Bacteroides isolates including 80 Bacteroides fragilis and 100 peptococci and peptostreptococci. The minimal inhibitory concentration (MIC) 75% of B. fragilis was less than or equal to 32 micrograms/ml for the cephalosporins tested and less than or equal to 8 micrograms/ml for thienamycin. The MIC of B. fragilis and Bacteroides vulgatus was not much influenced by increased inoculum size. Characteristically, peptostreptococci and peptococci were resistant to all four cephalosporins tested with MIC 75% being 32-64 micrograms/ml. All five antibiotics in this study appear suitable for therapy of intraabdominal suppurative infections, but the poor activity of third-generation cephalosporins on anaerobic cocci can be a cause of concern.
Insights
This study evaluated antibiotic susceptibility in anaerobic bacteria from abdominal trauma patients. N-formimidoyl thienamycin showed better activity against Bacteroides fragilis than cephalosporins, though both classes are suitable for intra-abdominal infections.
Area of Science:
- Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Intra-abdominal infections often involve anaerobic bacteria.
- Antibiotic resistance in these pathogens is a growing concern.
- Third-generation cephalosporins and N-formimidoyl thienamycin are used for such infections.
Purpose of the Study:
- To assess the in vitro susceptibility of anaerobic bacteria from abdominal trauma patients to specific antibiotics.
- To compare the efficacy of third-generation cephalosporins versus N-formimidoyl thienamycin.
Main Methods:
- Serial agar dilution method was used to determine minimal inhibitory concentrations (MICs).
- Testing was performed on 473 anaerobic bacterial isolates in an anaerobic glove box.
- Isolates included Bacteroides species, peptococci, and peptostreptococci.
Main Results:
- N-formimidoyl thienamycin demonstrated potent activity against Bacteroides fragilis (MIC75% ≤ 8 µg/ml).
- Third-generation cephalosporins showed moderate activity against B. fragilis (MIC75% ≤ 32 µg/ml).
- Peptostreptococci and peptococci exhibited resistance to all tested cephalosporins (MIC75% 32-64 µg/ml).
Conclusions:
- All tested antibiotics show potential for treating intra-abdominal suppurative infections.
- The limited efficacy of third-generation cephalosporins against anaerobic cocci warrants consideration in treatment selection.