四种碳青霉烯类抗生素筛选金属酶方法的比较

目的 以EDTA为金属酶抑制剂,比较4种碳青霉烯类抗生素对金属酶筛选的效果.方法 从浙江大学附属第二医院收集产金属β内酰胺酶革兰阴性杆菌30株(16株肠杆菌科细菌和14株非发酵菌)、产KPC肠杆菌科9株和产OXA鲍曼不动杆菌10株,用双纸片金属酶筛查试验分析IPM、MEM、PAN和ETP在加入EDTA前后抑菌环直径的变化.结果 当以抑菌环直径差值≥5 mm为假定判读标准时,PAN组的敏感度相对较高66.7％ (20/30)],其次为MEM组63.3％ (19/30)]和IPM组60.0％ (18/30)],ETP组最差43.3％ (13/30)]；当以抑菌环直径差值≥4 mm为假定判读标准时,MEM组和PAN组的敏感度达到80.0％ (24/30).以抑菌环直径差值≥3 mm为假定判读标准时,IPM组和MEM组的敏感度达到90.0％ (27/30),而PAN组和ETP组的敏感度为83.3％ (25/30)；在这3类假定判读标准下,4种抗生素的特异度均达到100％.用金属酶筛查试验筛选16株产金属酶的肠杆菌科细菌,当以5 mm为假定判读标准时,PAN组的敏感度最高75.0％ (12/16)]；以4mm为假定判读标准时,PAN组的敏感度高达93.8％ (15/16),远高于IPM组75.0％ (12/16)]、MEM组68.8％ (11/16)]和ETP组68.8％ (11/16)].结论 以EDTA为抑制剂的金属酶筛查试验,操作简便快捷,特异性高.不推荐使用ETP来筛查金属酶,对于革兰阴性杆菌的金属酶筛选可选择以≥4 mm为判读标准的MEM或PAN纸片；对于肠杆菌科细菌的金属酶筛选试验可选择以≥4 mm为判读标准的PAN纸片；而对于非发酵菌的金属酶筛查试验,不推荐使用PAN.

Evaluation of four carbapenems disk tests for screening metallo-beta-lactamases

Objective To evaluate the effect of four carbapenems combined with EDTA for metallobeta-lactamases (MBLs) detection.Methods Thirty MBLs-producing gram-negative bacteria ( 16 strains of Enterobacteriaceae and 14 strains of Non-fermentative),9 KPC-producing Enterobacteriaceae and 10 OXA-producing Acinetobacter baumannii strains were collected from the Second Affiliated Hospital of Zhejiang University.A double disk screening test with EDTA was performed for MBLs detection,comparing the changes of inhibition zone diameter with or without EDTA.Results When the inhibition zone diameter difference of ≥5 nn as standard,the sensitivity of panipenem (PAN) group was relatively high (66.7％,20/30),followed by meropenem group (MEM) (63.3％,19/30) and imipenem (IPM) group (60.0％,18/30),etrapenem (ETP) group was the wont (43.3％,13/30).When the inhibition zone diameter difference of ≥4 mm as standard,the sensitivity of meropenem and panipenem group was 80.0％ (24/30)respectively.When the inhibition zone diameter difference of ≥ 3 mm as standard,the sensitivity of imipenem and meropenem group was 90.0％ (27/30) respectively,while 83.3％ ( 25/30 ) for etrapenem and panipenem group.Specificity of four groups under these three interpretation was 100％ respectively.Results of screening test for 16 MBLs positive strains showed that the sensitivity of panipenem group was the highest (75.0％,12/16).While using ≥ 5 mm as the MBLs positive interpretation,the sensitivity of panipenem group was the highest (75.0％,12/16).While using ≥4 mm as the MBLs positive interpretation,the sensitivity of panipenem group (93.8％,15/16) was much higher than that of imipenem (75.0％,12/16),meropenem (68.8％,11/16) and ertapenem (68.8％,11/16).Conclusions Detection of MBLs with EDTA is easy to operate,and it shows a low false positive rate against gram-negative bacteria.Ertapenem is not recommended to screen for MBLs,the best method for screening for MBL production in gram-negative bacteria is the MEM-EDTA or PAN-EDTA with a breakpoint of ≥4 mm.As for Enterobacteriaceae,PAN-EDTA with a breakpoint of ≥4 mm is better than the other three carbapenems in screening for MBL production,but panipenem is not recommended for MBLs screening tests for nonfermentative gram-negative bacteria.