title: [Comparison of minimum inhibitory concentrations of group M penicillins against Staphylococcus aureus. Practical impact on diagnosis and treatment].
abstract: The MICs were determined in usual conditions and in special conditions for the detection of heterogeneous methicillin resistance. The study involved 40 strains of Staphylococcus aureus of the 3 categories of homogeneous resistant, heterogeneous resistant and sensitive strains. The MICs of the 4 main compounds of the group M penicillins, methicillin, oxacillin, cloxacillin and dicloxacillin, were lower in the presence of a higher number of chlorine atoms on the molecule. The heterogeneous strains were even sensitive to dicloxacillin. The MIC for a notable fraction of resistant strains were lower than the critical value, i.e. these strains entered the category of dicloxacillin sensitive even in reading conditions theoretically leading to the detection of heterogeneous resistance. These in vitro observations are of value in the presence of methicillin sensitive strains, since antibiotics containing one or two chlorine atoms will probably be more therapeutically effective. But the bacteriologist should pay more careful attention to the detection of methicillin resistant and heteroresistant strains, since the resistance in vivo is extended to other penicillinase-resistant penicillins or penicillins M.
authors.affiliation: Laboratoire de Microbiologie A, Centre Hospitalier Régional, Poitiers, France.
authors.forename: Y
authors.initials: Y
authors.lastname: de Rautlin de la Roy
authors.forename: B
authors.initials: B
authors.lastname: Grignon
authors.forename: O
authors.initials: O
authors.lastname: Castel
mesh_terms: D003023:Cloxacillin / Q000494:pharmacology; D004009:Dicloxacillin / Q000494:pharmacology; D006801:Humans; D008712:Methicillin / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D010068:Oxacillin / Q000494:pharmacology; D010403:Penicillin Resistance; D010406:Penicillins / Q000494:pharmacology*; D013211:Staphylococcus aureus / Q000187:drug effects*
chemical_list: D010406:Penicillins; D004009:Dicloxacillin; D003023:Cloxacillin; D008712:Methicillin; D010068:Oxacillin
vernacular_title: Comparaison des concentrations minimales inhibitrices des pénicillines du groupe M vis-à-vis des Staphylococcus aureus. Incidences pratiques sur le diagnostic et la thérapeutique.