Carbapenem resistance in bacteria isolated from soil and water environments in Algeria.

Abstract

OBJECTIVES: Recent research has demonstrated that natural populations of bacteria carry large numbers of mobile genetic elements which may harbour antibiotic resistance determinants. The aim of this study was to investigate carbapenem resistance in Gram negative bacteria isolated from natural environments in Bejaia (Algeria), and determine the horizontal gene transfer potential of a subset of these resistance genes. METHODS: Resistant bacteria were isolated and host identified with MALDI-TOF/16S rRNA sequencing. Resistance gene carriage was investigated using double disc synergy, metallo-β-lactamase (MBL) production tests and PCR screening for carbapenemase resistance genes. To determine potential mobility, conjugation experiments were performed. To identify resistance genes, genomic libraries were constructed, functionally screened; then inserts were sequenced. RESULTS: From soil and water samples, 62 resistant strains were classified as belonging to the Enterobacteriaceae, Pseudomonadaceae, Xanthomonadaceae and Aeromonadaceae families. Four highly imipenem and cefotaxime resistant (MICs >64μg/ml and >8μg/ml, respectively), clinically relevant strains were selected for further characterization. All four strains produced extended spectrum β-lactamases, but MBL production was not confirmed. Imipenem and cefotaxime resistance was transferable to E. coli strains but was not conferred by blaAMPc, blaIMP, blaNDM, blaKPC, blaOXA-48 or blaGES genes. Novel putative resistance mechanisms were identified, including a novel DHA β-lactamase which conferred clinical resistance to cefotaxime. CONCLUSIONS: The environment is a reservoir of carbapenem resistant bacteria. Further investigation of evolution and dissemination of antibiotic resistance in environmental bacteria is required, to understand and prevent the emergence of resistance in clinical environment.