Ciprofloxacin- resistant ST198 Salmonella Kentucky in a hospitalized American black bear (Ursus americanus), with evidence of subsequent nosocomial transmission

Global emergence of ciprofloxacin-resistant ST198 Salmonella Kentucky poses an important public health threat. While conducting Salmonella surveillance among wildlife patients admitted to our veterinary medical teaching hospital in central New York, we isolated multidrug-resistant (MDR) ST198 Salmonella Kentucky from an American black bear (Ursus americanus) in September 2020. The isolate was phenotypically resistant to numerous antimicrobial agents, including ceftriaxone and ciprofloxacin, and several antimicrobial resistance genes and mutational resistance determinants were detected. Between April and July 2021, the same strain of MDR ST198 Salmonella Kentucky was also isolated from seven other wildlife patients and multiple hospital environmental locations, suggesting nosocomial transmission. Ciprofloxacin resistance is conferred by triple point mutations in the quinolone resistance-determining regions (QRDRs), a genotypic profile indicative of Clade ST198.2. To our knowledge, this is the first report of this ciprofloxacin-resistant clade being identified in animals or animal products in the United States. Timely resolution of the outbreak was achieved following efforts to further enhance environmental disinfection protocols and biosecurity measures at the hospital, with no known cases or positive environmental samples after July 2021.