Diffusion of extended-spectrum and plasmid-mediated amp-C β-lactamase producing Proteus mirabilis in hospitals and community setting in Croatia

Abstract

AIM: We report the characteristics of extended-spectrum β-lactamases (ESBLs) and plasmid-mediated AmpC β-lactamases (p-AmpC), encountered among hospital and community isolates of [P. mirabilis]. BACKGROUND: We observed increased rate of multidrug-resistant [P. mirabilis] isolates. It develops resistance to expanded-spectrum cephalosporins (ESC) due to production of ESBLs or p-AmpC. METHODS: Inhibitor based tests were applied to screen for ESBLs and p-AmpC. The resistance genes were investigated by PCR. RESULTS: 39 isolates were analysed. Twenty-two isolates phenotypically tested positive for p-AmpC and seventeen for ESBLs. AmpC producing organisms exhibited uniform resistance to amoxycillin-clavulanate, ESC, ciprofloxacin and cotrimoxazole and susceptibility to carbapenems and piperacillin-tazobactam and harboured (bla)CMY-16 genes. All ESBL positive isolates demonstrated resistance to amoxycillin-clavulanate, cefotaxime and ceftriaxone but variable susceptibility phenotype to aminoglycosides and possessed blaCTX-M genes belonging to cluster 1 or 9. CONCLUSIONS: The main finding of the study is the diffusion of CTX-M ESBL and CMY-16 p-AmpC among hospital and community-acquired isolates. AmpC-producing isolates showed uniform resistance patterns, whereas ESBL positive strains had variable degree of susceptibility/resistance to non-β-lactam antibiotics, resulting in more diverse susceptibility patterns.

Keywords

• Proteus mirabilis
• extended-spectrum bea-lactamases
• plasmid-mediated ampC beta-lactamases
• resistance