Metallo-β-lactamases and class D carbapenemases in south-east Tunisia: Implication of mobile genetic elements in their dissemination

Abstract Carbapenem resistance in Gram-negative bacteria constitutes a major clinical problem. We characterized molecular features among carbapenem-resistant Gram-negative clinical isolates collected from Southeastern Tunisian Island Hospital. Eighteen carbapenem-resistant clinical isolates (13 Klebsiella pneumoniae , 1 Proteus mirabilis , 1 Enterobacter cloacae , 3 Acinetobacter baumannii ) were recovered during April 2015-August 2016. Molecular characterization of antimicrobial resistance was performed using polymerase chain reaction (PCR) and sequencing. Molecular typing of carbapenemase-producing K. pneumoniae was performed by pulsed-field gel electrophoresis (PFGE) after Xba I digestion and multilocus sequence typing (MLST). Conjugation experiments were conducted and type/number/size of plasmids were characterized by PCR-Based-Replicon-Typing and PFGE after S1 digestion. Carbapenemase genes were detected in K. pneumoniae [ bla NDM-1 (8), bla NDM-1 + bla OXA-48 (1), bla OXA-48 (4)], P. mirabilis [ bla OXA-48 (1)], E. cloacae [ bla VIM-2 (1)] and A. baumannii [ bla OXA-23 (3)]. K. pneumoniae isolates were typed as ST15, ST1412 and ST147 and showed seven different pulsotypes. The genetic structure surrounding bla NDM-1 was composed of IS Aba125 and ble . The bla VIM-2 carried by E. cloacae was located within the variable region of a class1 integron and bla OXA-48 gene was inserted into Tn 1999.2 . IncA/C and IncFIIA replicons were implicated in dissemination of bla NDM-1 and a non-typeable 48.5 kb plasmid in the propagation of bla OXA-48 . The emergence of carbapenemase-producing Gram-negative species in a Tunisian hospital shows the need for preventive strategies and hygiene measures to minimize their spread. Although conjugative plasmids play an important role in rapid carbapenemase genes dissemination, other mobile genetic elements, such as insertion sequences, transposons and integrons, are involved in acquisition of these resistances.