Evaluation of four carbapenems disk tests for screening metallo-beta-lactamases / 中华检验医学杂志

ABSTRACT

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.