Preliminary Study on Phenotypic Detection of ESBL and Amp-C β-Lactamase-Producing Escherichia Coli Isolates from Slaughtered Pigs

The presence of extended-spectrum beta-lactamase-producing Escherichia coli in food animals is a public health concern. The aim of this study was to phenotypically detect the extended β-lactamase and AmpC β-lactamase-producing E. coli isolated from pig caecum from three slaughterhouses in the North-East of Romania. After collecting the cecal samples, they were phenotypically processed. ESBL and AmpC screening was carried out by cultivation on MacConkey medium with addition of cefotaxime (MC+CTX). The isolates were confirmed as being E. coli based on the biochemical properties using MIU, TSI and API 20E and as ESBL based on synergy tests between clavulanic acid and ceftazidime and/or clavulanic acid and cefotaxime. Phenotypical detection of AmpC beta-lactamase-producing strains was carried out through a stable AmpC cephalosporin (cefepime). Following ESBL/AmpC screening, out of the 128 analysed samples, 51 (39.84%) grew on MC+CTX and they were identified as E. coli. After performing microdilution in broth using EUVSEC2 plates, 78.43% isolates were identified with ESBL phenotype, 9.8% isolates with ESBL/AmpC phenotype, and 11.77% isolates with AmpC phenotype. In this study, although a limited number of strains were analysed, the obtained results phenotypically confirm the presence of ESBL and AmpC enzymes in slaughtered pig populations from the North-East of Romania.