title: [Morphological changes in penicillin-resistant Streptococcus pneumoniae and beta-lactamase-nonproducing, ampicillin-resistant Haemophilus influenzae after exposure to oral antibacterial agents].
abstract: Morphological changes in penicillin-resistant Streptococcus pneumoniae (PRSP) and beta-lactamase-nonproducing, ampicillin-resistant Haemophilus influenzae (BLNAR) after exposure to oral antibacterial agents could be observed over time under a phase-contrast microscope. Morphological changes in BLNAR were also observed using a scanning electron microscope. The organisms used in this study were ME19F strain identified as genotypic(g) gPRSP (serotype: 19F) and JPH002 strain identified as gBLNAR (serotype: b). The antibacterial agents used were amoxicillin (AMPC), cefditoren (CDTR), tebipenem (TBPM), and tosufloxacin (TFLX). The concentration of each antibacterial agent to which the bacteria were exposed was set at the blood level one hour after Cmax when administered to children at the usual dose. Bacteriolysis of gPRSP cells started after exposure of only 20minutes to TBPM, and 90% of the cells were lysed within 2 hours. A high bactericidal action of TBPM on gPRSP was supported by these findings. When gBLNAR was exposed to AMPC and TBPM, lysis from spheroplasts and cells with vacuoles were sometimes observed. In contrast, after gBLNAR was exposed to CDTR, lysis occurred after marked filamentation in the cells, but after exposure to TFLX, cells deduced to be killed after mild filamentation without lysis. Time-dependent morphological changes that reflect the differences in bactericidal activity and PBP affinity among beta-lactams provide beneficial information to select antibacterial agents.
authors: Laboratory of Molecular Epidemiology for Infectious Agents, Kitasato Institute for Life Sciences, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan.
authors: Naoko
authors: N
authors: Chiba
authors: Miyuki
authors: M
authors: Morozumi
authors: Kimiko
authors: K
authors: Ubukata
mesh_terms: D000658:Amoxicillin / Q000494:pharmacology*; D000668:Ampicillin Resistance; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001433:Bacteriolysis / Q000187:drug effects*; D015780:Carbapenems / Q000494:pharmacology*; D002511:Cephalosporins / Q000494:pharmacology*; D002648:Child; D004305:Dose-Response Relationship, Drug; D024841:Fluoroquinolones / Q000494:pharmacology*; D006192:Haemophilus Infections / Q000382:microbiology; D006193:Haemophilus influenzae / Q000187:drug effects* / Q000302:isolation & purification / Q000648:ultrastructure; D006801:Humans; D008858:Microscopy, Phase-Contrast; D009287:Naphthyridines / Q000494:pharmacology*; D010403:Penicillin Resistance; D011008:Pneumococcal Infections / Q000382:microbiology; D013296:Streptococcus pneumoniae / Q000187:drug effects* / Q000302:isolation & purification / Q000648:ultrastructure; D013997:Time Factors; D001618:beta-Lactamases / Q000096:biosynthesis
chemical_list: D000900:Anti-Bacterial Agents; D015780:Carbapenems; D002511:Cephalosporins; D024841:Fluoroquinolones; D009287:Naphthyridines; D000658:Amoxicillin; C073460:cefditoren; D001618:beta-Lactamases; C055185:tosufloxacin; C500135:tebipenem