JAC Advance Access originally published online on October 7, 2004
Journal of Antimicrobial Chemotherapy 2004 54(5):897-903; doi:10.1093/jac/dkh442
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JAC vol.54 no.5 © The British Society for Antimicrobial Chemotherapy 2004; all rights reserved
In vitro bactericidal activity of antimicrobial agents against enterohaemorrhagic Escherichia coli
1 Department of Pharmacy, Yamaguchi University Hospital, 1-1-1 Minamikogushi, Ube 755-8505; 2 Faculty of Pharmaceutical Science, Hiroshima International University, 5-1-1 Hiro-koshingai, Kure 737-0112; 3 Yamaguchi Prefectural Research Institute of Health, 2-5-67 Aoi, Yamaguchi 753-0821, Japan
* Corresponding author. Tel: +81-836-22-2665; Fax: +81-836-22-2673; Email: akira-ygc{at}umin.ac.jp
Objectives: In vitro bactericidal activity of four antimicrobial agents was determined against nine strains of enterohaemorrhagic Escherichia coli.
Methods: Pulsed-field gel electrophoresis was carried out with the Bio-Rad Gene Path system. Each antimicrobial agent was added to logarithmic phase of enterohaemorrhagic E. coli (four strains of E. coli O157:H7, two of E. coli O26, two of E. coli O111, and one of E. coli O165) in broth to obtain a concentration of 10 or 50 mg/L, and viable cells were counted after 1, 2, 6 and 24 h.
Results: All nine strains were confirmed to differ in their DNA pattern by pulsed-field gel electrophoresis. Norfloxacin at concentrations of 10 and 50 mg/L had bactericidal effects on all nine strains of enterohaemorrhagic E. coli. However, cefoperazone, kanamycin and fosfomycin had no bactericidal effects on some strains. In particular, after addition of 10 mg/L fosfomycin or kanamycin, four of the nine strains showed proliferation.
Conclusions: Norfloxacin had marked bactericidal effects on enterohaemorrhagic E. coli. This information could be of value in planning randomized clinical trials of antimicrobial agents as treatment for enterohaemorrhagic E. coli infection.
Keywords: killing kinetics , norfloxacin , cefoperazone , kanamycin , fosfomycin