Comparison of disc diffusion and E test® for in vitro antimicrobial susceptibility testing of Campylobacter jejuni and Campylobacter coli isolated from poultry

Abstract

The correlation between disc diffusion and E test® for in vitro antimicrobial susceptibility of Campylobacter jejuni and Campylobacter coli was evaluated using a quality control strain C. jejuni NCTC 11168 and 60 C. jejuni and 25 C. coli isolates recovered from poultry (chicken and turkey) faeces. Four antimicrobial agents ; ciprofloxacin, enrofloxacin, erythromycin and tetracyclin were tested using the two methods. The correlation between the E test, and disc diffusion varied greatly depending on the antimicrobial agents tested. The percentages of true results and 95% CI for disc diffusion for resistant strains were 75.3 % for ciprofloxacin, 25.9 % for enrofloxacin, 21.2 % for erythromycin and 14.1 % for tetracycline. Based on the E test® MICs, the resistant rate of the 85 Campylobacter isolates was highest for ciprofloxacin (78.8 %), followed by enrofloxacin (49.4%), erythromycin (21.2 %) and tetracycline (12.9%). Overall, our results suggest that disc diffusion is a reliable, easy and inexpensive susceptibility testing method for C. jejuni and C. coli for enrofloxacin, ciprofloxacin, erythromycin and tetracycline. The study indicated that the E test® results were reliable but it has been proven to be satisfactory testing method, its use for Campylobacter susceptibility testing requires further standardization. The resistance to four antibiotics for Campylobacter isolates in our study needs to be confirmed using the agar dilution or broth dilution methods. Therefore, surveillance programmes on antimicrobial-resistant clinical zoonotic pathogens in veterinary medicine in Turkey are needed.