Detection of Salmonella spp. in pooled environmental samples from an equine veterinary hospital using a novel point-of-care PCR assay

Abstract

The objective of this study was to evaluate a point-of-care (POC) PCR assay for the detection of Salmonella spp. in pooled environmental samples collected at an equine veterinary hospital. A total of 945 environmental samples were collected from high-risk areas, including ICU and isolation stalls, high-traffic areas, treatment rooms, and surgical suites. The environmental samples were collected using drag swabs placed in selenite broth and individually incubated at 35 °C for 20 h. Following the incubation period, 1 mL of up to 10 individual environmental samples were pooled together. Each pool was processed for nucleic acid purification, followed by qPCR analysis for Salmonella spp., as well as direct testing using the POC PCR assay. PCR analyses were performed in a masked fashion, i.e., qPCR and POC PCR assay results remained unknown. Follow-up testing by qPCR and POC PCR for individual environmental samples was performed when a positive pool was detected. A total of 135 pools ranging from 6 to 10 samples per pool were tested. Results showed 100 % agreement between qPCR and POC PCR, with 118 and 17 pools testing PCR-negative and -positive, respectively. Testing of individual environmental samples from the 17 PCR-positive pools identified the same Salmonella spp. positive individual environmental samples by both qPCR and POC PCR. The strategy of pooling environmental samples for the PCR testing of Salmonella spp. has shown promise in monitoring high-risk areas in equine veterinary hospitals. The Salmonella spp. POC PCR assay showed excellent agreement with qPCR, further improving compliance by reducing the turn-around time to 24 h from sample collection to analysis.