Saiman L, Burns J L, Whittier S, Krzewinski J, Marshall S A, Jones R N
Department of Pediatrics and Clinical Microbiology, Columbia University, New York, New York 10032, USA.
J Clin Microbiol. 1999 Sep;37(9):2987-91. doi: 10.1128/JCM.37.9.2987-2991.1999.
The development of multidrug-resistant Pseudomonas aeruginosa in patients with cystic fibrosis (CF) is most likely a consequence of increasing life expectancy and more prolonged exposure to antibiotics. The optimal method for antibiotic susceptibility testing of CF strains, particularly mucoid P. aeruginosa strains, is unknown. Antimicrobial susceptibilities of 48 CF strains (25 mucoid) and 50 non-CF strains to 12 anti-Pseudomonas agents were tested by both agar dilution and commercially custom-prepared broth microdilution plates (PML Microbiologicals, Portland, Oreg.) in three laboratories simultaneously to determine if broth microdilution could substitute for agar dilution as the reference method in subsequent studies. Comparison of MICs generated by agar dilution and broth microdilution demonstrated correlation coefficients (r) exceeding 0.85 for all agents tested; correlation was excellent for aminoglycosides (r >/= 0.92) and very good for beta-lactam agents including agents paired with a beta-lactamase inhibitor (r >/= 0.87) and for ciprofloxacin (r = 0.86). Correlation was not improved by 48-h readings, but correlation between 24- and 48-h readings ranged between 0.91 and 0.98 for both methods. Interlaboratory variations were minimal, as the percentage of acceptable variations was 94% for both methods, and serious discords were infrequent (<2% of comparisons). However, CF strains were more likely to have serious discords than were non-CF strains (P < 0. 0001), although mucoid strains were not more likely to have serious discords than were nonmucoid strains. In this study, MICs determined by custom-prepared broth microdilution compared favorably with MICs determined by agar dilution. Thus, this broth microdilution assay can serve as a reference method and facilitate future studies to determine the optimal method for antibiotic susceptibility testing of CF strains.
囊性纤维化（CF）患者中多重耐药铜绿假单胞菌的出现很可能是预期寿命延长以及长期接触抗生素的结果。CF菌株，尤其是黏液型铜绿假单胞菌菌株的最佳抗生素敏感性检测方法尚不清楚。在三个实验室同时采用琼脂稀释法和商业定制的肉汤微量稀释板（PML Microbiologicals，俄勒冈州波特兰市）对48株CF菌株（25株黏液型）和50株非CF菌株对12种抗假单胞菌药物的抗菌敏感性进行检测，以确定在后续研究中肉汤微量稀释法是否可以替代琼脂稀释法作为参考方法。琼脂稀释法和肉汤微量稀释法所产生的最低抑菌浓度（MIC）比较显示，所有受试药物的相关系数（r）均超过0.85；氨基糖苷类药物的相关性极佳（r≥0.92），β-内酰胺类药物（包括与β-内酰胺酶抑制剂联用的药物）和环丙沙星的相关性很好（r≥0.87和r = 0.86）。48小时读数并未改善相关性，但两种方法在24小时和48小时读数之间的相关性在0.91至0.98之间。实验室间差异极小，因为两种方法的可接受差异百分比均为94%，严重不一致情况很少见（<2%的比较）。然而，CF菌株比非CF菌株更有可能出现严重不一致情况（P < 0.0001），尽管黏液型菌株与非黏液型菌株相比出现严重不一致情况的可能性并无差异。在本研究中，定制肉汤微量稀释法测定的MIC与琼脂稀释法测定的MIC相比具有优势。因此，这种肉汤微量稀释测定法可作为参考方法，并有助于未来研究确定CF菌株抗生素敏感性检测的最佳方法。
