Antibiotics in media for isolation of Campylobacter spp. do not enhance resistance.

in the promoter –attenuator region of the chromoso-mal ampC gene were also studied by PCR and sequencing. 3 Broad-spectrum cephalosporin-resistant E. coli strains were detected in five of the 75 faecal samples analysed (6.6%, four dogs and one cat). Four of the five strains, obtained from four unrelated dogs, gave positive ESBL screening test results and were resistant to cefotaxime and/or ceftazidime. The bla TEM-52b gene was identified in three of these four strains and the bla CTX-M-1 gene in the remaining one, these strains being negative for the other b-lactamase genes tested by PCR. The characteristics of these E. coli strains are included in Table 1. The three bla TEM-52b-containing strains were also resistant to streptomycin, and two of them also to tetracycline. The bla CTX-M-1-containing strain was resistant to streptomycin – tetracycline– sulfamethoxazole –chloramphenicol and also harboured the int I gene, associated with type I integrons (detected by PCR). The remaining broad-spectrum cephalosporin-resistant E. coli strain that was recovered from a healthy cat, showed a negative ESBL screening test and all PCR assays for TEM, SHV, OXA, CTX-M, FOX and CMY b-lactamase-encoding genes were negative. Mutations at the À42, À18, À1 and +58 positions of the promoter–attenuator region of the chromosomal ampC gene were detected by PCR and sequencing. This strain showed a pattern of multi-resistance, which included nalidixic acid, ciproflox-acin, tetracycline, streptomycin, gentamicin, tobramycin, trimethoprim/sulfamethoxazole and chloramphenicol, and this strain also harboured the int I gene. To our knowledge, this is the first time that ESBL-encoding genes have been detected in healthy pets and also the first time that CTX-M b-lactamases have been detected in E. coli strains from animal origin in Portugal. More studies should be carried out in the future to track the evolution of this type of b-lacta-mase in different environments.