Postantibiotic effects and postantibiotic sub-MIC effects of benzylpenicillin on viridans streptococci isolated from patients with infective endocarditis.
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.
Kikuchi
K
K
Department of Medicine, Tokyo Women's Medical College, Japan.
Enari
T
T
Minami
S
S
Haruki
K
K
Shibata
Y
Y
Hasegawa
H
H
Katahira
J
J
Totsuka
K
K
Shimizu
K
K
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
D010400:Penicillin G