Y. enterocolitica is a b-lactamase producer, and thus is commonly
resistant to ampicillin and first-generation cephalosporins . A previous study
described two chromosomally encoded b-lactamases in
Y. enterocolitica, BlaA and BlaB. In the
present study, all strains of Y. enterocolitica carried both b-lactamase
genes, with the exception of one bioserotype 1A/O:3 strain
and one bioserotype 1A/O:8 strain, both isolated from raw pork and
negative for the presence of the blaA gene. The levels of resistance
to ampicillin (91.38%) were comparable to those found by Bonke
et al. (92%) (2011) and Bonardi et al. (89%) (2013). Resistance
against cephalothin (91.38%) was consistent with that found by
Bhaduri et al. (87.7%) (2009). Nevertheless, we identified several
blaAþ strains that were susceptible to ampicillin, and several blaAstrains
that were resistant. Similarly, we identified strains
harboring blaB that were susceptible to cephalothin. One explanation
for this apparent discrepancy may be differences in the cell
walls between different strains