Aquatic environment contamination with an epidemic Escherichia coli clone harbouring blaCTX-M-15, blaOXA-1, blaTEM-1, and aac(6')-Ib-cr in Portugal

Abstract number: P1525

Machado E., Rocha J., Coque T., Cantón R., Sousa J., Ferreira H., Peixe L.

Objectives: The presence of CTX-M-15-producing isolates in non-clinical compartments has been scarcely investigated. In this study we describe the presence of

CTX-M-15-producing Escherichia coli isolates in aquatic environments in Portugal. We also compared its clonal relationship with CTX-M-15-producing isolates recovered from clinical settings in the same geographic area.

Methods: We studied two CTX-M-15-producing E. coli isolates recovered from sea and streams reaching the shore, in Porto area, Portugal, during 2006. Water samples were plated on MacConkey agar with and without 1 mg/L ceftazidime or cefotaxime after filtration. Species identification, susceptibility testing and conjugation assays were performed by standard methods. ESBL characterisation included synergy test, IEF, and identification of known bla genes by PCR and sequencing. Clonal relatedness was established by RAPD-PCR. The RAPD patterns were also compared with those obtained in CTX-M-15-producing E. coli clinical strains. Multilocus sequence typing (MLST) using the standard seven housekeeping loci was also performed. E. coli phylogenetic groups were identified by multiplex PCR. Presence of specific resistance genes was searched by PCR [blaOXA, blaTEM, blaCTX-M, aac(6')-Ib].

Results: Both CTX-M-15-producing E. coli belonged to phylogenetic group B2 and were clonally related by RAPD analysis. Moreover, they shared the same RAPD pattern of the predominant Portuguese E. coli clinical clone, producing CTX-M-15 and belonging to clonal complex ST131. Both strains were resistant to b-lactams (except carbapenems), tetracycline, kanamycin, tobramycin and ciprofloxacin. blaTEM-1 and aac(6')-Ib-cr-blaOXA-1 were also detected. Transfer of CTX-M-15 was achieved in both isolates.

Conclusions: Aquatic contamination with an epidemic and multiresistant B2 CTX-M-15-producing E. coli clone belonging to clonal complex ST131 is a matter of concern. This fact will undoubtedly increase the possibilities of dissemination of this epidemic clone and the corresponding blaCTX-M-15 plasmid. Control of release of these bacteria to the environment should be a public health priority in our country.