Prevalence of carbapenemases among Gram-negative bacteria in Tunisia: first report of KPC-2 producing Acinetobacter baumannii

The rapid evolution of the antibacterial resistance problem worldwide, including the Mediterranean countries, constitutes a real threat to public health. This study aims to characterize carbapenemase encoding genes among Gram-negative bacteria collected from some Tunisian hospitals. Twenty-two clinical carbapenem-resistant Gram-negative bacteria were recovered, and identified by the matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) method. Antibiotic resistance was tested by disk diffusion method on Muller-Hinton Agar. The minimum inhibitory concentration (MIC) for imipenem was revealed by the E-test method. Carbapenemase encoding genes were screened by polymerase chain reaction (PCR). Genetic relatedness was performed by the pulsed field gel electrophoresis (PFGE) method. Our isolates, identified as K. pneumoniae (n = 7), P. mirabilis (n = 1), A. baumannii (n = 13), and P. aeruginosa (n = 1), presented high MIC values for imipenem. Enterobacerales were resistant to carbapenems due to OXA-48 production. Only, four K. pneumoniae harbored the blaNDM-1 gene. VIM-2 production was detected in P. aeruginosa. However, OXA-23 production was observed in A. baumannii isolates, one of which co-produced the KPC-2 enzyme that was identified for the first time in Tunisia in this species. A high genetic diversity was demonstrated by pulsed-field gel electrophoresis in K. pneumoniae and A. baumannii after XbaI and ApaI digestion respectively. Our findings highlight the spread of various unrelated clones of carbapenemase-producers in some Tunisian hospitals as well as the spread of several carbapenemase types.