Risk factors for nosocomial Salmonella infection among hospitalized horses

Objective-To identify risk factors for nosocomial Salmonella infections amo ng hospitalized horses. Design-Longitudinal study. Animals-1,583 horses hospitalized in an intensive care unit between January 1992 and June 1996. Procedure-Survivor functions were used to estimate time to shedding salmone llae for various Salmonella serotypes. Survival analysis was then used to d etermine how Variables associated with patient management, environmental co nditions, hospital conditions, and other disease processes affected the ris k of nosocomial Salmonella infection. Results-78 horses shed Salmonella organisms: 35 shed Salmonella krefeld, 26 shed S typhimurium, and 17 shed other Salmonella serotypes. Mean time from admission to shedding was significantly longer for horses shedding S krefe ld or S typhimurium than for horses shedding other Salmonella serotypes. Th erefore, infection with S krefeld or S typhimurium was considered nosocomia l. Seven variables were found to be significantly associated with risk of n osocomial Salmonella infection: mean number of horses in the hospital shedd ing S krefeld during the 4 days prior to and the day of admission, mean num ber of horses shedding S typhimurium during this period, a diagnosis of lar ge colon impaction, withholding feed, number of days fed bran mash, duratio n of treatment with potassium penicillin G, and mean daily ambient temperat ure. Clinical implications-Results suggest that risk of nosocomial Salmonella in fections is greater for horses with large colon impactions. In addition to implementing hospital protocols that minimize cross contamination between p atients, strategies to reduce the risk Of nosocomial Salmonella infection s hould include minimizing use of potassium penicillin G and regulation of en vironmental temperature in the hospital.