Decreasing trend of -lactam resistance in isolates from broiler chickens due to the cessation of ceftiofur administration.

Ceftiofur, a third-generation cephalosporin antimicrobial, was used in Japanese hatcheries for many years before 2012. We continue to study in broilers and their antimicrobial resistance. The current study aimed to express how the cessation of ceftiofur affects the antimicrobial resistance of isolated from broiler chickens in Kagoshima Prefecture, Japan in 2017 and 2018. A total of 274 isolates were recovered from 1535 cecal content samples obtained from 96 broiler flocks over years 2017 and 2018. Among the isolates, the predominant serovars were Manhattan (128/274, 46.7%), Schwarzengrund (120/274, 43.8%), and Infantis (26/274, 9.5%). The isolates showed a high proportion of antimicrobial resistance for oxytetracycline, sulfamethoxazole, and streptomycin. However, the β-lactam resistance rates were significantly decreased ( < 0.01) in 2017, while no -lactam resistant isolates detected in 2018. The highlight of this study was the complete disappearance of -lactam resistance in isolates from broiler chicken in Kagoshima, Japan.