三种AmpC酶表型检测方法比较

Evaluation on three phenotype methods for detecting AmpC beta-lactamase

目的对革兰阴性菌产AmpC酶的检测方法进行评价，并寻找一种适合临床常规应用的AmpC酶检测方法。方法对39株耐头孢西丁的革兰阴性菌同时进行改良Hodge试验、三维试验、氯唑西林（CLO）双纸片协同试验和ampC基因聚合酶链反应（PCR）检测，比较4种方法的结果。结果39株革兰阴性杆菌中，改良Hodge试验、三维试验和CLO双纸片协同试验检出产AmpC酶的阳性率分别为38．5％、43．6％和28．2％，3种方法AmpC酶检出率的差异无统计学意义（P〉0．05）。与PCR结果比较，改良Hodge试验特异性为87％，敏感性为75％；三维试验的特异性为78％，敏感性为75％；CLO双纸片协同试验特异性为87％，敏感性为50％。PCR显示ampC基因阳性率为41％（16／39），对16株阳性菌进行ampC基因测序，测序结果与基因数据库内相应的ampC核酸序列比对发现，同源性均在98％～100％之间。结论改良Hodge试验可作为一种操作快速、简便的筛选试验检测革兰阴性菌产AmpC酶的情况，而CLO双纸片协同试验可作为一种操作简便的排除产AmpC酶试验应用于实验室，但在准确性上低于改良Hodge试验。

Objective To evaluate methods for detecting AmpC beta-lactamase produced by Gram-negative bacillus and find a convenient and suitable method for clinical laboratories. Methods Modified Hodge test , three-dimensional test, cloxacillin （CLO） double-disk synergy test and polymerase chain reaction （PCR） were performed in the 39 cefoxitin-resistant strains of Gram-negative bacillus, and then their results were compared. Results From the 39 strains of Gram-negative bacillus, the AmpC positive rates of modified Hodge test, three-dimensional test and CLO double-disk synergy test were 38.5% , 43.6% and 28.2% , respectively. The percentage of detection of AmpC had no significant difference among three phenotype screening tests （P 〉 0.05 ）. In comparison with the results of PCR, the specificity and sensitivity were 87% and 75% for modified Hodge test, 78% and 75% for three-dimensional test, and 87% and 50% for CLO double-disk synergy test. The results of PCR showed that there were 16 positive strains carrying ampC gene and the percentage was 41% （16/39）. They were sequenced, and then the ampC gene sequencing results of 16 strains indicated that the homology was from 98% to 100% by comparing with the gene bank. Conclusions Modified Hodge test is a convenient method to detect MnpC enzyme produced by Gram-negative bacillus, and CLO double-disk synergy test is easy to use in clinical laboratories to eliminate a possibility of AmpC beta-lactamases production, but modified Hodge test is better than CLO double-disk synergy test in the accuracy.