Methodologic challenges and lessons learned through conducting a hospital-based Salmonella Javiana case-control study

Area of Science:

• Epidemiology
• Foodborne illness
• Infectious disease outbreaks

Background:

• Salmonellosis outbreaks can occur in healthcare settings, posing risks to vulnerable populations.
• Identifying the specific food source is crucial for controlling transmission and preventing future outbreaks.

Purpose of the Study:

• To determine the food item most likely contaminated with Salmonella Javiana during an outbreak affecting two North Carolina hospitals.
• To investigate the association between specific food exposures and salmonellosis in a hospital setting.

Main Methods:

• A 2:1 matched case-control study design was employed.
• Food histories were collected from hospital food orders, and patient medical records provided covariate data.
• Conditional logistic regression was used to estimate odds ratios (OR) for food exposures and salmonellosis.

Main Results:

• Twenty-one cases and 42 controls were included in the analysis.
• Fruit cups showed the strongest association with salmonellosis (adjusted OR = 7.9; 80% CI: 2.7, 23.6).
• Attack rate analyses supported fruit cups as a common source, despite variations in hospital-specific ORs.

Conclusions:

• Fruit cups were implicated as the likely source of the salmonellosis outbreak in the two hospitals.
• Methodological challenges, including control selection and reliance on food orders, were identified.
• Improving hospital policies and procedures is essential for effective outbreak investigations.