Outbreak of multidrug resistant Salmonella Typhimurium in calves at a veterinary hospital in Brazil

The present study aimed to describe and characterize a nosocomial outbreak caused by a multidrug resistant Salmonella Typhimurium in hospitalized calves at a veterinary medical teaching hospital from Brazil. Sixty-three (96.9%) calves showed lethargy, hyperthermia and profuse diarrhea and despite treatment, 26 (41.2%) animals died. Five animals were necropsied and stool samples of six calves were collected. The isolated strains were subjected to antimicrobial susceptibility test by disc-difusion method and were fingerprinted by ERIC-PCR. Macroscopic lesions suggestive of salmonellosis, such as fibrinonecrotic enteritis and hepatosplenomegaly were observed. Salmonellosis was confirmed by isolation of S. Typhimurium from stool samples and organs from seven affected animals. Six out of seven isolates of S. Typhimurium, exhibited 100% of similarity at ERIC-PCR, suggesting occurrence of nosocomial transmission of S. Typhimurium among the hospitalized calves. All but one S. Typhimurium isolated were resistant to marbofloxacin, enrofloxacin, florfenicol, oxytetracycline and trimethoprim/sulfamethoxazole, antimicrobial agents largely used for humans and animal treatment. This is the first study of a nosocomial outbreak of multidrug resistant S. Typhimurium in a veterinary hospital in Brazil and highlighted the need for preventive measures to reduce the risks for inpatients and humans in contact with animals.