Plasmid-mediated CMY-2 AmpC b-lactamase and CTX-M-14 extended-spectrum b-lactamase in Proteus mirabilis clinical isolate

Abstract number: P1219

Simões S., Lito L., Melo-Cristino J., Salgado M., Duarte A.

Objectives:Proteus mirabilis is considered one of the most b-lactam susceptible members of the Enterobacteriaceae. Although extended-spectrum b-lactamases (ESBLs) have recently been identified, there are few reports of plasmid-mediated AmpC b-lactamase (PCBL) in P. mirabilis. In general, ESBLs confer resistance to oxyimino-cephalosporins but not cephamycins and are inhibited by b-lactamase inhibitors, while PCBLs provide resistance to cephamycins and oxyimino-cephalosporins and are refractory to b-lactamase inhibitors. We report the identification of ESBL and PCBL enzymes in P. mirabilis isolate.

Methods:P. mirabilis 10830 isolated from neurological abscess was collected in Hospital de Santa Maria at Lisboa. Susceptibility to antimicrobial agents was determined by disk diffusion test, following CLSI guidelines. The conjugation assay was performed using Escherichia coli 802 K as recipient strain. PCR experiments were performed using specific primers for ESBL, PCBL, insertion sequences and class 1 integrons. Plasmid extraction was prepared using Kado & Liu method.

Results: The isolate showed resistance to amoxicillin-clavulanate, cefoxitin, cefpime, cefotaxime; intermediate to ceftazidime and susceptible to imipenem and fluoroquinolones. It was observed two plasmids in both P. mirabilis and transconjugant E. coli P10830, which showed the same susceptibility to b-lactams including cefoxitin.

The double-disk synergy test was observed between clavulanate and cephalosporins (cefepime and cefotaxime). However, a higher synergic effect was observed when the cloxacillin was applied to Mueller-Hinton agar. PCR and sequencing revealed that P. mirabilis 10830 clinical isolate and the transconjugant E. coli K P10830 harboured CMY-2 AmpC b-lactamase and CTX-M-14 extended-spectrum b-lactamase; A complex class 1 integron containing the blaCMY-2 gene; and the blaCTX-M-14 gene was bracketed upstream and downstream by insertion sequences ISEcp1 and IS903, respectively.

Conclusions: This is the first report of a plasmid that carries both CTX-M-type ESBL and CMY-type PCBL genes. The finding of the coexistence of these genes in such a transmissible plasmid that can propagate in different hosts provides further insight into the mechanisms of transmission of these b-lactamases in Portugal.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Location: Barcelona, Spain
Presentation type:
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