Beta-lactam resistance in Campylobacter coli and Campylobacter jejuni chicken isolates and the association between bla gene expression and the action of β-lactamase inhibitors.

The objectives of this work were to evaluate β-lactamase-mediated β-lactam resistance in Campylobacter coli and Campylobacter jejuni isolates obtained from broiler chickens, expression of the bla gene in relation to β-lactamase production, and the possible association between bla gene expression and the action of inhibitors when combined with β-lactams. All strains were tested by disk diffusion and nitrocefin methods to assess antibiotic susceptibility and β-lactamase production, respectively. PCR and qPCR amplification were performed to evaluate qualitative and quantitative bla expression. Campylobacter spp. showed a high level of resistance to the most of antimicrobials tested. C. coli strains were ampicillin resistant and bla positive, and 59 out of 60 isolates were positive in the nitrocefin test. Twenty C. jejuni isolates were positive for bla and the nitrocefin test, although two isolates were ampicillin sensitive. Amoxicillin/clavulanic acid and ticarcillin/clavulanic acid do not seem to be active against C. coli, as 73.3 %, and 88.3 % of isolates were resistant to amoxicillin/clavulanic acid and ticarcillin/clavulanic acid, respectively. C. jejuni was not susceptible to amoxicillin/clavulanic acid, with 90 % of the strains showing resistance, whereas ticarcillin associated with clavulanic acid was significantly more efficient than ticarcillin alone (P < 0.01), with 90 % of the strains found to be susceptible. An association between bla expression and amoxicillin/clavulanic acid and ticarcillin/clavulanic acid resistance (P = 0.0001) was seen in C. coli, as well as in C. jejuni for ampicillin/sulbactam (P = 0.0001). Our results suggest that the clavulanic acid only shows an inhibitory effect on C. jejuni when combined with ticarcillin and that the inhibitors action is lower if the bla gene is highly expressed.