title: Postantibiotic effects and postantibiotic sub-MIC effects of benzylpenicillin on viridans streptococci isolated from patients with infective endocarditis.
abstract: We investigated the postantibiotic effects (PAEs) and the postantibiotic sub-MIC effects of benzylpenicillin on three strains of viridans streptococci isolated from infective endocarditis patients. The PAEs of benzylpenicillin on penicillin tolerant Streptococcus sanguis TW-70 (0.4-3.9 h), penicillin tolerant S. sanguis TW-80 (0.3-6.3 h) and nontolerant Streptococcus oralis TW-186 (0.5-3.1 h) were dependent on exposure time. The PAEs were not concentration dependent for S. sanguis TW-70 and S. sanguis TW-80 above the MIC, and for S. oralis TW-186 above 16 x MIC. The antimicrobial effects of benzylpenicillin at sub-MIC concentrations were examined in bacteria pretreated with benzylpenicillin (8 x MIC) for 2 h and compared with untreated bacteria. At the sub-MICs tested, the regrowth of pretreated S. oralis TW-186 cells was more prolonged than that of untreated cells and bactericidal action was seen only in pretreated cells. These effects (so-called 'postantibiotic' sub-MIC effects') were not observed in penicillin tolerant S. sanguis TW-70. The presence of the postantibiotic sub-MIC effect may be an important factor in determining the dosing regimen for infective endocarditis.
authors.affiliation: Department of Medicine, Tokyo Women's Medical College, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Kikuchi
authors.forename: T
authors.initials: T
authors.lastname: Enari
authors.forename: S
authors.initials: S
authors.lastname: Minami
authors.forename: K
authors.initials: K
authors.lastname: Haruki
authors.forename: Y
authors.initials: Y
authors.lastname: Shibata
authors.forename: H
authors.initials: H
authors.lastname: Hasegawa
authors.forename: J
authors.initials: J
authors.lastname: Katahira
authors.forename: K
authors.initials: K
authors.lastname: Totsuka
authors.forename: K
authors.initials: K
authors.lastname: Shimizu
mesh_terms: D004697:Endocarditis, Bacterial / Q000188:drug therapy / Q000382:microbiology*; D006801:Humans; D008826:Microbial Sensitivity Tests; D010400:Penicillin G / Q000494:pharmacology*; D013298:Streptococcus sanguis / Q000187:drug effects*; D013997:Time Factors
chemical_list: D010400:Penicillin G