title: A model to show the role of extracellular beta-lactamases in mediating staphylococcal resistance.
abstract: Considerable amounts of extracellular beta-lactamase are liberated from penicillin-resistant staphylococci into the surrounding medium. The accumulation of exoenzyme in conventional in-vitro test systems may result in rapid inactivation of hydrolysable antibiotics, while in vivo the concentration of extracellular beta-lactamase varies depending on the site of infection. Using a new open test model designed to eliminate the effect of exoenzyme, it could be shown that resistance of beta-lactamase-producing staphylococci to mezlocillin as seen in the broth dilution test was mediated predominantly by the extracellular beta-lactamase fraction. Animal experiments suggested that mezlocillin may exhibit a therapeutic effect against beta-lactamase-producing staphylococci under certain conditions in vivo which prevent build-up of exoenzyme.
mesh_terms: D000818:Animals; D008802:Mezlocillin / Q000494:pharmacology; D051379:Mice; D008954:Models, Biological; D010403:Penicillin Resistance; D013210:Staphylococcus / Q000187:drug effects* / Q000201:enzymology; D001618:beta-Lactamases / Q000502:physiology*
chemical_list: D001618:beta-Lactamases; D008802:Mezlocillin