An outbreak of salmonellosis among horses at a veterinary teaching hospital.

The research is about an outbreak of Salmonella Typhimurium infection in a veterinary teaching hospital, which affected 27 horses and a veterinary student from May 1996 to February 1997. Despite efforts to clean and disinfect the facility and modify infection control, the disease persisted, leading to further investigation into the source and spread of the infection.

Research Context and Methodology

• Spread between May 1996 and February 1997, a nosocomial infection of Salmonella Typhimurium was identified among 27 horses and a veterinary student at a veterinary school hospital.
• The initial source was traced back to a neonatal foal admitted for the treatment of septicemia. This particular strain of Salmonella Typhimurium was resistant to multiple drugs.
• To understand the manifestation and control of the infection, various tests including polymerase chain reaction on environmental samples were conducted. The antibiotic resistance pattern of the isolates was also studied, supported by pulsed-field gel electrophoresis testing.

Research Findings

• Of the respective number of hospitalized horses, approximately 13% of them were infected with this strain of salmonella. This high infection rate, combined with a high fatality rate of 44% in the earliest 18 horses affected, led to the decision to close the hospital for extensive disinfection and cleaning.
• Despite these precautions, nine additional horses fell victim to the infection within six months after the hospital reopened. This emphasised the inherent challenge in controlling the infection spread.
• Through testing, a potential reservoir of the bacteria was identified in the drainage system in the isolation facility of the hospital.
• Results from antimicrobial resistance patterns combined with clinical data allowed researchers to quickly determine or disprove instances of nosocomial infection. Minor changes were observed in the genome of these isolates over the course of the outbreak.
• From the analysis of the antimicrobial resistance patterns and sequencing data using pulsed-field gel electrophoresis testing, it was confirmed that the Salmonella Typhimurium infections were hospital-acquired in all 27 horses.

Implication and Outcome

• This research sheds light on the significant challenge of controlling nosocomial infections even in controlled environments like a hospital.
• The findings highlight the importance of implementing rigorous disinfection procedures and stringent infection control measures, especially in animal care facilities.
• These results also underscore the usefulness of antimicrobial resistance patterns and genomic data in tracking and confirming the transmission routes of nosocomial infections, thereby informing efforts to prevent and control these infections.