Outbreak of Salmonellosis Caused by Salmonella enterica Serovar Newport MDR-AmpC in a Large Animal Veterinary Teaching Hospital

BACKGROUND: Nosocomial salmonellosis is an important problem for large animal veterinary teaching hospitals (VTHs). OBJECTIVE: To describe failure of an Infection Control Program (ICP) that resulted in an outbreak of salmonellosis caused by Salmonella Newport multidrug resistant (MDR)-AmpC at a large animal VTH. ANIMALS: Sixty-one animals identified with the outbreak strain of Salmonella. METHODS: Retrospective study: Data collected included signalment, presenting complaint, duration of hospitalization, discharge status, and financial information. Phenotypic and genotypic characterization was performed on Salmonella isolates. RESULTS: The outbreak occurred despite an existing ICP; the ICP was reviewed and weaknesses identified. Routine patient surveillance was not performed before or during the outbreak; fecal sampling was triggered only by a patient algorithm based on clinical signs. Sixty-one animals were infected with the outbreak strain of S. Newport, and the majority were horses (n = 54). Case fatality rate was 36.1%. S. Newport isolates demonstrated high genetic similarity (Dice ≥ 0.96), and all had the MDR-AmpC phenotype. Environmental persistence of the organism necessitated complete hospital closure, extensive decontamination, and remediation of the facility. A paradigm shift in the relevance of biosecurity in a VTH and the establishment of a stringent ICP were integral components of successful hospital reopening. CONCLUSIONS AND CLINICAL IMPORTANCE: An ineffective ICP resulted in a nosocomial outbreak caused by a MDR S. Newport in a VTH. Closure of a VTH affected all missions of the institution and had substantial financial impact (US$4.12 million).