Emergence of Proteus mirabilis Isolates Producing TEM-52 Extended-Spectrum β-Lactamases in Croatia

Background: An increased frequency of extended-spectrum β-lactamase (ESBL)-positive Proteus mirabilis isolates was observed recently in the Clinical Hospital Center Split in Croatia. The aim of this study was the molecular characterization of ESBLs in P. mirabilis isolates from this hospital. Material and Methods: Seven strains showing reduced susceptibility to ceftazidime were investigated. Antimicrobial susceptibility was determined using the broth microdilution method. ESBLs were characterized by PCR and sequencing of bla ESBL genes. Quinolone resistance determinants (qnr genes) were characterized by PCR. Genotyping of strains was performed by pulsed-field gel electrophoresis (PFGE). Results: The presence of an ESBL was confirmed in all strains by a double-disk synergy test. All strains were resistant to amoxicillin, piperacillin, gentamicin, ciprofloxacin, chloramphenicol, sulfamethoxazole and trimethoprim, but susceptible to ceftazidime/clavulanic acid, piperacillin/tazobactam, cefoxitin, imipenem and meropenem; PCR sequencing using primers targeting bla ESBL genes revealed TEM-52 β-lactamase. PFGE genotyping demonstrated the clonal relatedness of TEM-52-producing P. mirabilis strains isolated from different clinical samples and wards within the hospital. Bla TEM-52 in 3 isolates was carried by a 70-kb conjugative plasmid. Conclusions: Our findings indicate the emergence of the TEM-52 enzyme among P. mirabilis in Croatia.