title: The role of beta-lactamase in mixed infections in mice in relation to treatment with ampicillin.
abstract: Beta-lactamase-producing Staphylococcus aureus and Bacteroides fragilis in a localized mixed infection has been found to degrade the beta-lactam antibiotic at the focus of infection, thus protecting both the bacteria and pathogens susceptible to the antibiotic. To determine if beta-lactamase produced by Hemophilus influenzae and Branhamella catarrhalis have similar importance in mixed infections, a thread infection model in mice was used to evaluate the capacity of beta-lactamase produced by S. aureus, B. catarrhalis, or H. influenzae to hydrolyze ampicillin in a mixed infection with Streptococcus pneumoniae in mice. For both S. aureus and B. catarrhalis, the ampicillin concentrations at infection sites where beta-lactamase was produced were lower than at sites where beta-lactamase was not produced; however, this difference was not found when clavulanic acid was added to the ampicillin. In mixed infections with strains that did not produce beta-lactamase, ampicillin concentrations were similar with or without clavulanic acid. S. aureus was the best "protector" followed by B. catarrhalis. The beta-lactamase produced by H. influenzae failed to protect the S. pneumoniae. No bactericidal effect of clavulanic acid was found.
authors.affiliation: Department of Medical Microbiology, University of Lund, Sweden.
authors.forename: J
authors.initials: J
authors.lastname: Renneberg
authors.forename: M
authors.initials: M
authors.lastname: Walder
mesh_terms: D000667:Ampicillin / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D001424:Bacterial Infections / Q000188:drug therapy*; D019818:Clavulanic Acid; D002969:Clavulanic Acids / Q000494:pharmacology; D005260:Female; D006193:Haemophilus influenzae / Q000201:enzymology*; D051379:Mice; D008807:Mice, Inbred BALB C; D001936:Moraxella catarrhalis / Q000201:enzymology*; D013211:Staphylococcus aureus / Q000201:enzymology*; D013296:Streptococcus pneumoniae / Q000187:drug effects*; D001618:beta-Lactamases / Q000502:physiology*
chemical_list: D002969:Clavulanic Acids; D019818:Clavulanic Acid; D000667:Ampicillin; D001618:beta-Lactamases