Improvement of Karmali agar by supplementation with tazobactam for detecting Campylobacter in raw poultry

Abstract

In this study, Karmali agar was modified by adding tazobactam (T-Karmali agar) to suppress the growth of extended-spectrum β-lactamase (ESBL) - producing Escherichia coli, which frequently contaminates raw poultry meat. By inoculating 30 Campylobacter spp. strains and 25 ESBL-producing E. coli strains onto Karmali agar and T-Karmali agar containing various concentrations of the antibacterial agent, we determined the optimum concentration of tazobactam to be 4 mg/liter. The Campylobacter spp. isolation rate on T-Karmali agar (13.3%) was higher than that on Karmali agar (8.3%), although the difference was not significant (P > 0.05). However, T-Karmali agar showed a significantly greater selectivity than Karmali agar, as evaluated by comparing the numbers of contaminated agar plates (20.8 versus 82.5%; P < 0.05) and the growth indexes (1.36 versus 2.83) of competing flora. The predominant competing flora on Karmali and T-Karmali agar were identified as ESBL-producing E. coli. Thus, T-Karmali agar might be effective for determining the real prevalence of Campylobacter in raw poultry and, especially, contamination with ESBL-producing E. coli.