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Post-antibiotic effect in Bacteroides fragilis group.
D J Siverhus1, C E Edmiston, J C Clausz
1Department of Surgery, Medical College of Wisconsin, Milwaukee 53226.
Annals of Clinical and Laboratory Science
|July 1, 1988
Summary
This study investigated the post-antibiotic effect (PAE) in anaerobic bacteria. Certain Bacteroides fragilis group members showed prolonged growth suppression after exposure to beta-lactam antibiotics, suggesting potential impacts on antibiotic dosing.
Area of Science:
- Microbiology
- Pharmacology
- Infectious Diseases
Background:
- The post-antibiotic effect (PAE) describes the delay in bacterial growth after antimicrobial exposure.
- PAE studies are common for aerobic bacteria but scarce for anaerobic microorganisms.
- The Bacteroides fragilis group is a significant component of the human gut microbiota and a common cause of intra-abdominal infections.
Purpose of the Study:
- To investigate the post-antibiotic effect (PAE) of specific beta-lactam antibiotics against anaerobic isolates from the Bacteroides fragilis group.
- To determine if brief, high-concentration antibiotic exposure induces a measurable PAE in these anaerobic bacteria.
Main Methods:
- Anaerobic isolates of the Bacteroides fragilis group were exposed to cefoxitin, cefotetan, and imipenem at 2-4 times their minimal inhibitory concentration (MIC) for one hour.
- The post-antibiotic effect was quantified by measuring the time for bacterial growth to increase by one Log10 above baseline post-drug removal.
- Broth dilution techniques were employed to assess bacterial growth and determine PAE.
Main Results:
- Bacteroides fragilis, B. ovatus, B. thetaiotaomicron, and B. vulgatus exhibited post-antibiotic effects with all tested antibiotics.
- The duration of the PAE varied among strains, ranging from 6 to 50 hours.
- No significant PAE was observed in Bacteroides distasonis strains using the broth dilution method.
Conclusions:
- Brief exposure to high concentrations of specific beta-lactam antibiotics can induce a prolonged growth suppression (PAE) in certain members of the Bacteroides fragilis group.
- The observed PAE in these anaerobic bacteria suggests that antibiotic dosing regimens may need to consider this phenomenon for effective treatment.
- Further research into PAE of anaerobes could refine therapeutic strategies for infections involving the Bacteroides fragilis group.