Carbapenemase-producing carbapenem-resistant enterobacteriaceae from Bangkok, Thailand, and their detection by the Carba NP and modified carbapenem inactivation method tests

Abstract

© 2018 Mary Ann Liebert, Inc. Aim: The purpose of the study was to determine the epidemiology of carbapenemase genes among carbapenem-resistant Enterobacteriaceae and evaluate the Carba NP and modified carbapenem inactivation method (mCIM) tests in their detection. Materials and Methods: A total of 287 nonduplicated Enterobacteriaceae isolates, which were at least resistant to one of the carbapenems, were identified and detected for carbapenemase genes by multiplex PCR covering bla KPC , bla NDM , bla VIM , bla IMP , and bla OXA-48-like . All positive genes were then sequenced. These isolates were phenotypically tested for the production of carbapenemases by mCIM and Carba NP tests to evaluate the efficacy of these methods. Results: Seven species of carbapenem-resistant isolates mainly Klebsiella pneumoniae, Escherichia coli, and Enterobacter cloacae were detected. Of these isolates, three families of carbapenemase genes, including bla NDM (bla NDM-1 , -4 , -5 , -9 ), bla OXA (bla OXA-48 , -181 , -232 ), and bla IMP-14 , were found. Of these, 223 (77.70%) carried at least one of the carbapenemase genes. The bla NDM was detected in 160/223 (71.75%) isolates, of which 153/160 (95.63%) were the bla NDM-1 . Three types of the bla OXA-48-like group, bla OXA-48 , bla OXA-181 , and bla OXA-232 , were found, 91/104 (87.5%) harbored the bla OXA-232 . In addition, 25.11% (56/223) of the carbapenemase-producing isolates harbored a combination of bla NDM and bla OXA-48-like . Phenotypic detection methods, mCIM and Carba NP, showed 100% sensitivity and specificity to bla NDM , bla IMP-14 , and bla OXA-48 , while the mCIM was positive in all bla OXA-181 and bla OXA-232 isolates, only 12.5% (1/8) and 28.95% (11/38), respectively, were detected by the Carba NP test. Conclusions: This study revealed a unique prevalence of carbapenemase genes in Bangkok, Thailand, as well as demonstrated the efficacy and limitation of phenotypic detection methods of carbapenemase in the area where bla NDM-1 and bla OXA-232 were predominant.