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In vitro susceptibility of Escherichia coli O157 to several antimicrobial agents
1Department of Pharmacy, Yamaguchi University Hospital, Kogushi, Ube, Japan.
Abstract:
We evaluated the antimicrobial susceptibility of six strains of Escherichia coli O157 (E. coli O157) isolated from patients in Yamaguchi Prefecture between June and July, 1996. Seven antimicrobial agents that were expected to retain a high concentration in the intestine were selected. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of ciprofloxacin, polymyxin B, cefoperazone, and kanamycin for each strain were < or = 6.25 microg/ml. However, the MIC of fosfomycin was 3.13-100 microg/ml, and its MBC was > or = 100 microg/ml. The MIC of ampicillin and tetracycline was > 100 mcirog/ml in some strains. In a time-kill study of E. coli O157 at a drug concentration of 12.5 microg/ml, about 10(4) colony forming units/ml of E. coli O157 were eradicated within 10 min by ciprofloxacin, within 30 min by polymyxin B, within 4 h by cefoperazone, and within 16 h by kanamycin. These results suggest that the new quinolones with a poor absorption rate in the intestine (such as ciprofloxacin and norfloxacin) are effective against E. coli O157. When oral administration is impossible, bile excreting cephem antibiotics (such as cefoperazone, ceftriaxone, and cefotetan) may be useful.
Insights
New quinolones like ciprofloxacin are effective against Escherichia coli O157 (E. coli O157) infections. Bile-excreting cephem antibiotics are alternatives when oral administration of E. coli O157 treatments is not possible.
Area of Science:
- Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Escherichia coli O157 (E. coli O157) is a significant pathogen.
- Antimicrobial resistance is a growing concern in treating E. coli O157 infections.
Purpose of the Study:
- To evaluate the antimicrobial susceptibility of E. coli O157 strains.
- To identify effective antimicrobial agents for E. coli O157 treatment.
Main Methods:
- Antimicrobial susceptibility testing including Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC).
- Time-kill studies were conducted to assess the rate of bacterial eradication.
Main Results:
- Ciprofloxacin, polymyxin B, cefoperazone, and kanamycin showed potent activity against E. coli O157.
- Fosfomycin, ampicillin, and tetracycline exhibited variable or lower efficacy.
- Ciprofloxacin rapidly eradicated E. coli O157 in time-kill assays.
Conclusions:
- New quinolones with poor intestinal absorption, such as ciprofloxacin, are effective against E. coli O157.
- Bile-excreting cephem antibiotics are potential therapeutic options for E. coli O157 when oral administration is not feasible.