Detection of metallo-beta lactamases and oxacillinase genes in carbapenem-resistant Acinetobacter baumannii strains isolated in Morocco

Abstract

Introduction: resistance to carbapenem is widespread among Acinetobacter baumannii (A. baumannii) strains. Metallo-beta lactamases enzymes (MBL) are responsible for carbapenem resistance, as are oxacillinases (OXA). In recent years, MBL producing carbapenem-resistant strains have been reported in the world and Morocco at increasing rates. Our study aimed to investigate the presence of carbapenemases in acinetobacter strains isolated from hospitalized patients in CHU Fez.

Methods: a total of 58 imipenem-resistant A. baumannii strains isolated from clinical samples were investigated. The presence of MBL was described phenotypically by the double-disk synergy test (DDST), MBL E-test, and modified Hodge test. The bla_IMP, bla_VIM, genes, and bla_OXA-23, bla_OXA-51 genes were investigated by multiplex polymerase chain reaction (PCR). The blaNDM-1 gene was determined by simplex PCR.

Results: fifty-eight strains were resistant to imipenem (98%), the modified Hodge test (MHT) was positive for 58 strains (100%), 47 strains (82%) were found to be positive for MBL by the test of double-disk synergy (DDST), 58 strains (100%) were positive by E-test MBL. The OXA 51 gene was detected in all strains, and the OXA 23 gene was detected in 53 strains (91%). In addition, the MBL genes were not detected by genotypic methods.

Conclusion: the OXA-23 and OXA-51 carbapenemases type are responsible for the resistance to carbapenems in A. baumannii resistant to carbapenems in our establishment. Resistance to carbapenems by MBL enzymes has been found by phenotypic tests, which must be confirmed by genotypic methods; and solicit other MBL genes.