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摘要
A range of E. coli isolates were tested by agar dilution method comparing the Minimal Inhibitory Concentration (MIC) for eight antimicrobials obtained by Mueller-Hinton II agar, MacConkey agar and SEC plates. Kappa statistics was used to assess the levels of agreement when classifying strains as resistant, intermediate or susceptible.SEC plate showed that 74% of all strains agreed within ㊣ 1 log2 dilution when comparing MICs with Mueller-Hinton II media. High agreement levels were found for gentamicin, ampicillin, chloramphenicol and cefotaxime, resulting in a kappa value of 0.9 and 100% agreement within ㊣ 1 log2 dilution. Significant variances were observed for oxytetracycline and sulphamethoxazole. Further tests showed that the observed discrepancy in classification of susceptibility to oxytetracycline by the two media could be overcome when a plate-dependent breakpoint of 64 mg/L was used for SEC plates. For sulphamethoxazole, SEC plates provided unacceptably high MICs.SEC plates showed good agreement with Mueller-Hinton II agar in MIC studies and can be used to screen and discriminate resistant E. coli for ampicillin, cephalothin, streptomycin, chloramphenicol, cefotaxime and gentamicin using CLSI standardized breakpoints, but not for sulphamethoxazole. SEC plates can also be used to discriminate oxytetracycline-resistant E. coli if a plate-dependent breakpoint value of 64 mg/L is used.Escherichia coli is the most common intestinal bacterium of the Enterobacteriacae family and its presence outside the intestine is often used as an indicator of faecal pollution and in surveillance programs of antimicrobial resistance. Screening and enumeration of antimicrobial resistant E. coli directly from samples, e.g., food or animal specimens, is needed to identify emerging resistance clones and to obtain quantitative data for epidemiological investigations [1]. MacConkey agar has been widely used as selective medium for isolation and enumeration of E. coli due to its low co
- 出版日期2008
