title: Lack of in vitro and in vivo selection of bacterial resistance by roxithromycin.
abstract: The in vitro and in vivo selective pressure exerted by roxithromycin on Lancefield group A beta-haemolytic streptococci (GABHS) was investigated. In vitro antimicrobial activity on fifty GABHS strains was determined by the microdilution method and by boundary concentration (BC) determination. Insorgence of resistance was evaluated by redetermining MIC and BC after exposure to 16 x MIC roxithromycin concentration. In vivo insorgence of resistance was evaluated by MIC and BC determinations on the GABHS strain recovered from infected mice peritoneum, after treatment with 20 mg/kg roxithromycin. The roxithromycin serum kinetics was established in healthy and infected mice. Neither significant changes in GABHS MIC or BC after in vitro or in vivo exposure to roxithromycin nor a difference in roxithromycin serum levels between healthy and infected mice were detected, suggesting that the roxithromycin selection of resistance in GABHS is low.
authors.affiliation: Laboratory of Clinical Microbiology, LITA, 'L. Sacco' Teaching Hospital, Milan, Italy. microbio@mailserver.it
authors.forename: L
authors.initials: L
authors.lastname: Drago
authors.forename: M C
authors.initials: MC
authors.lastname: Fassina
authors.forename: E
authors.initials: E
authors.lastname: De Vecchi
authors.forename: B
authors.initials: B
authors.lastname: Mombelli
authors.forename: A
authors.initials: A
authors.lastname: Lombardi
authors.forename: M R
authors.initials: MR
authors.lastname: Gismondo
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000097:blood / Q000494:pharmacology*; D004352:Drug Resistance, Microbial; D005260:Female; D051379:Mice; D008815:Mice, Inbred Strains; D008826:Microbial Sensitivity Tests; D015575:Roxithromycin / Q000097:blood / Q000494:pharmacology*; D012641:Selection, Genetic; D013291:Streptococcus / Q000187:drug effects* / Q000502:physiology
chemical_list: D000900:Anti-Bacterial Agents; D015575:Roxithromycin