First characterisation in Tunisia of plasmid mediated AmpC bta-lactamase DHA-1 coexpressed TEM-24 and QnrA6 in a multidrug resistant Proteus mirabilis clinical strain

Abstract

The aim of the study was to investigate the coresistance of qnrA6 determinants and DHA-1, TEM-24 β-lactamases in a multidrug-resistant Proteus mirabilis SM18575 strainisolated from Tunisia with reduced succeptibility to oximinocephalosporins. The strain with an inducible phenotype was detected in March 2007 in a Tunisian hospital. The isolate was tested for broth minimum inhibitory concentrations, isoelectric focusing (IEF), polymerase chain reaction (PCR) for SHV, TEM, and DHA-derived β-lactamases, and nucleotide sequencing. A multiplex PCR was performed for the screnning of qnrA, qnrB and qnrS. IEF, PCR and sequence analysis revealed that the isolate possessed a blaTEM-1, blaTEM-24 and a blaDHA-1 gene and produced quinolone resistance determinants qnrA6.The inducible cephalosporin resistance was transferred and the transconjugantsexpressed non susceptibility to third generation cephalosporins. To the best of our knowledge, this is the first detection of DHA-1 and TEM-24 β-lactamases in a Tunisian hospital. Keys words: β-Lactamase, coresistance, qnr determinants.