Antimicrobial Resistance Unit, National Institute for Health and Welfare (THL), Turku and Helsinki, Finland.
J Clin Microbiol. 2012 Jan;50(1):52-6. doi: 10.1128/JCM.01090-11. Epub 2011 Nov 9.
The agar dilution method has been standardized by the CLSI for the susceptibility testing of Campylobacter species, and according to these standards, the disk diffusion method should be used only in screening for macrolide and ciprofloxacin resistance. Nevertheless, the disk diffusion test is currently widely used, since it is easy to perform in clinical microbiology laboratories. In this study, the disk diffusion method was compared to the agar dilution method by analyzing the in vitro activities of seven antimicrobial agents against 174 Campylobacter strains collected in Finland between 2003 and 2008. Recommendations of the CLSI were followed using Mueller-Hinton agar plates with 5% of sheep blood. For each strain, the disk diffusion tests were performed two to four times. Of the 33 erythromycin-resistant strains (MIC, ≥16 μg/ml), 24 (73%) constantly showed a 6-mm erythromycin inhibition zone (i.e., no inhibition), while for seven strains the inhibition zone varied from 6 to 44 mm in repeated measurements. Among the 141 erythromycin-susceptible strains (MIC, <16 μg/ml), erythromycin inhibition zones varied between 6 and 61 mm. Of the 87 ciprofloxacin-resistant strains, 47 (54%) showed 6-mm inhibition zones, while 40 strains showed inhibition zones between 6 and 60 mm. Significant differences between the repetitions were observed in the disk diffusion for all antimicrobial agents and all strains except for the macrolide-resistant strains regarding the macrolides. For 17 (10%) strains, the variation in repeated measurements was substantial. These results show that the disk diffusion method may not be a reliable tool for the susceptibility testing of Campylobacter spp. Further studies are needed to assess whether the disk diffusion test could be improved or whether all susceptibilities of campylobacters should be tested using an MIC-based method.
琼脂稀释法已被 CLSI 标准化，用于检测弯曲菌属的药敏试验，根据这些标准，纸片扩散法只能用于筛选大环内酯类和环丙沙星耐药性。然而，由于纸片扩散试验在临床微生物学实验室中易于操作，因此目前仍广泛应用。在这项研究中，通过分析芬兰 2003 年至 2008 年间收集的 174 株弯曲菌对 7 种抗菌药物的体外活性，比较了纸片扩散法和琼脂稀释法。采用含 5%绵羊血的 Mueller-Hinton 琼脂平板，遵循 CLSI 的建议。对每种菌株进行 2-4 次纸片扩散试验。在 33 株红霉素耐药菌株（MIC≥16μg/ml）中，24 株（73%）始终表现出 6mm 的红霉素抑制区（即无抑制），而 7 株的抑制区在重复测量中从 6mm 变化至 44mm。在 141 株红霉素敏感菌株（MIC<16μg/ml）中，红霉素抑制区在 6mm-61mm 之间变化。在 87 株环丙沙星耐药菌株中，47 株（54%）表现出 6mm 的抑制区，而 40 株表现出 6mm-60mm 的抑制区。除大环内酯类耐药菌株对大环内酯类药物外，所有抗菌药物和所有菌株的纸片扩散试验重复结果均存在显著差异。在 17 株（10%）菌株中，重复测量的变化较大。这些结果表明，纸片扩散法可能不是弯曲菌属药敏试验的可靠工具。需要进一步研究评估是否可以改进纸片扩散试验，或者是否应该使用基于 MIC 的方法检测所有弯曲菌的药敏性。
