Outbreak of salmonellosis caused by Salmonella enterica serovar Newport MDR-AmpC in a large animal veterinary teaching hospital.

The research focuses on an outbreak of Salmonella Newport at a large animal veterinary teaching hospital, despite an existing Infection Control Program (ICP). The outbreak infected 61 animals mainly horses and led to a significant fatality rate. This required the hospital’s closure, extensive decontamination, and large financial costs.

Methods of research

The researchers conducted a retrospective study to understand more about the outbreak. They collected various data from the infected animals, including:

• The animal’s species, breed, age, and gender (signalment)
• The reason the animal was brought to the hospital (presenting complaint)
• How long the animal was hospitalized
• Whether the animal was discharged or died (discharge status)
• The costs related to each infected animal

In addition, they performed phenotypic and genotypic characterization on the Salmonella isolates to understand more about the specific strain causing the outbreak.

Research findings

The research findings highlighted several major issues:

• The outbreak happened even though the hospital had an ICP in place. This suggests the ICP was not effective enough in preventing such an outbreak.
• The patient surveillance was not proactive but was instead triggered only when certain clinical signs appeared, possibly allowing the infection to spread before being detected.
• A total of 61 animals were infected by Salmonella Newport, the majority of which were horses. Nearly 36.1% of these cases were fatal, suggesting the severity of the outbreak.
• The S. Newport isolates showed high genetic similarity and all had the MDR-AmpC phenotype, indicating resistance to multiple antibiotics.
• The persistent presence of the bacteria in the environment meant that the hospital had to be closed for extensive decontamination. This incurred substantial financial costs, with a reported impact of US$4.12 million.

Conclusions and implications

The researchers concluded that the ineffective ICP resulted in the nosocomial outbreak of Salmonella Newport, causing financial strain and disruption to the hospital’s operation. This incidient served as a strong reminder of the importance of having a stringent ICP and biosecurity measures in place in a veterinary teaching hospital to prevent future outbreaks. Furthermore, more proactive patient surveillance methods should be considered for early detection of infections.