In-Vitro Bactericidal Activities of Antimicrobial Agents During Short Period Incubation. I. A Comparative Study of Bactericidal Activities of Cephems Against Gram-Negative Bacilli

Seiichi Aonuma, Kikuo Onuma, Akira Watanabe, Masako Sasaki, Kotaro Oizumi, Kiyoshi Konno

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Determination of minimal bactericidal concentrations (MBCs) of antimicrobial agents has become much easier by the use of Dynatech MIC 2000 system. Thus it is now possible to determine MBCs of several drugs against many strains at various points in time during incubation. The results obtained by the present method differ only slightly from those obtained by the conventional method of counting viable ceils on agar plates. The MBC determined by Dynatech MIC 2000 system represents the lowest concentration with which 99.5 per cent of bacilli is killed during incubation with a drug We have determined MBCs of six cephems (CEZ, CMZ, CTM, CZX, CPZ and LMOX) against ten patient-strains each of E. coli, K. pneumoniae, S. marcescens and E. cloacae at various points in time of incubation, namely at 3,6 and 24 hours. The MBC thus determined was compared with minimal inhibitory concentration (MIC). It was found that the MBCs at 24 hour-incubation (24 h-MBCs) of all the six cephems tested were at nearly the same levels as those of MICs. The MBCs at 6 hour-incubation (6 h-MBCs) of the above cephems against test strains of E. coli and K. pneumoniae were at most eight times higher than the MICs. 6 h-MBCs against S. marcescens and E. cloacae were twice to 64 times higher than MICs. The 3 h-MBCs against four species of gram-negative bacilli of all the cephems examined were much higher than MICs. Bactericidal effects of CZX, CPZ and LMOX on S. marcescens IFO 3736 were evaluated by the conventional method of counting viable cells on agar plates. After 6 hour-incubation at a 6 h-MBC, the size of the initial inoculum was decreased to 1/100 with CZX, 1/128 with CPZ and to 1/240 with LMOX. This result indicates that the MBC determined by Dynatech MIC 2000 system correlates closely to the results obtained by the conventional viable counting method. In addition, it was found that, of the cephems examined, ceftizoxime exhibited the most potent bactericidal activity against four species tested, as evidenced by the results of determination of 3 hand 6 h-MBCs.

    Original languageEnglish
    Pages (from-to)733-738
    Number of pages6
    JournalChemotherapy
    Volume31
    Issue number7
    DOIs
    Publication statusPublished - 1983 Jan

    Keywords

    • CEZ
    • CMZ
    • CPZ
    • CTM
    • CZX
    • LMOX
    • cefazolin
    • cefmetazole
    • cefoperazone
    • cefotiam
    • ceftizoxime
    • latamoxef

    ASJC Scopus subject areas

    • Pharmacology (medical)
    • Infectious Diseases
    • Pharmacology
    • Drug Discovery
    • Oncology

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