Identification of sources of Salmonella organisms in a veterinary teaching hospital and evaluation of the effects of disinfectants on detection of Salmonella organisms on surface materials

Objective - To determine sources of Salmonella organisms in a veterinary teaching hospital, compare bacterial culture with polymerase chain reaction (PCR) testing for detection of Salmonella organisms in environmental samples, and evaluate the effects of various disinfectants on detection of Salmonella organisms on surface materials. Design - Prospective study. Sample Population - Fecal samples from 638 hospitalized horses and 783 environmental samples. Procedure - Standard bacterial culture techniques were used; the PCR test amplified a segment of the Salmonella DNA. Five disinfectants were mixed with Salmonella suspensions, and bacterial culture was performed. Swab samples were collected from 7 surface materials after inoculation of the surfaces with Salmonella Typhimurium, with or without addition of a disinfectant, and submitted for bacterial culture and PCR testing. Results - Salmonella organisms were detected in fecal samples from 35 (5.5%) horses. For environmental samples, the proportion of positive bacterial culture results (1/783) was significantly less than the proportion of positive PCR test results (110/783), probably because of detection of nonviable DNA by the PCR test. Detection of Salmonella organisms varied with the surface material tested, the method of detection (bacterial culture vs PCR testing), and the presence and type of disinfectant. Conclusions and Clinical Relevance - Results of the present study suggested that Salmonella organisms can be isolated from feces of hospitalized horses and a variety of environmental surfaces in a large animal hospital. Although recovery of Salmonella organisms was affected by surface material and disinfectant, bleach was the most effective disinfectant on the largest number of surfaces tested.