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).