JAC Advance Access published online on February 20, 2008
Journal of Antimicrobial Chemotherapy, doi:10.1093/jac/dkn056
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Original research |
Increase in β-lactam-resistant Proteus mirabilis strains due to CTX-M- and CMY-type as well as new VEB- and inhibitor-resistant TEM-type β-lactamases
1 Servei de Microbiologia, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain 2 Departament de Genètica i de Microbiologia, Universitat Autònoma de Barcelona, Barcelona, Spain
Received 26 September 2007; returned 22 October 2007; revised 22 January 2008; accepted 23 January 2008
* Correspondence address. Servei de Microbiologia, Hospital de la Santa Creu i Sant Pau, Av. Sant Antoni Ma Claret, 167, 08025 Barcelona, Spain. Tel: +34-93-2919069; Fax: +34-93-2919070; E-mail: fnavarror{at}santpau.es
Objectives: The aim of this study was to characterize the different inhibitor-resistant TEM β-lactamases, extended-spectrum β-lactamases (ESBLs) and plasmid-mediated AmpC β-lactamases implicated in β-lactam resistance in Proteus mirabilis, which has increased over recent years.
Methods: From February 2000 to December 2005, 1423 clinical isolates of P. mirabilis were collected. The AmpC phenotype was checked by means of a double-disc synergy test using cloxacillin as an inhibitor of AmpC enzymes. The production of ESBL was assessed by the double-disc synergy method and by Etest ESBL. Analytical isoelectric focusing, determination of kinetic constants, conjugation, PCR and a sequencing strategy were used to characterize the enzymes. The possible relationships between isolates were analysed by PFGE.
Results and conclusions: Twenty-five of 1423 isolates were found to display intermediate or full resistance to co-amoxiclav, cefotaxime or ceftazidime. Seventeen isolates had reduced susceptibility to co-amoxiclav; of these, seven produced TEM-110, eight produced the new TEM-159, one the new TEM-160 and one TEM-1. Five isolates producing TEM-110, TEM-159 or TEM-160 enzymes shared the same PFGE profile. Three isolates produced an ESBL, CTX-M-1, CTX-M-32 and the new variant, VEB-4. Finally, five isolates with an AmpC phenotype produced CMY-2, two with the same PFGE profile. Our data emphasize the diversity of β-lactamases found in this species.
Key Words: antimicrobial resistance surveillance , Enterobacteriaceae , mechanisms of resistance , ESBLs , antimicrobial resistance mechanisms , extended-spectrum β-lactamases , resistance epidemiology
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