Stool processing-methods for Salmonella enterica isolation and PCR detection

The aim of this study was to compare the efficiency of three protocols for bacteriological isolation of Salmonella enterica and detection by PCR in swine feces samples. Pool of feces (n=62) were processed by three different methods. Method 1: samples (10g) were pre-enriched in BPW (1:10) and enriched in Rappaport-Vassiliadis broth (1:100). Method 2: samples (1g) were first enriched in GN-Hajna broth (1:10) and secondly enriched in Muller-Kaufmann tetrathionate broth (1`:10). Method 3: Single step enrichment of feces (1g) in selenite-cystine broth (1:10). PCR was performed using DNA extracted from the last enrichment broth of each bacteriological method. Salmonella enterica was cultured from 13 out of 62 samples (20.9%) and seven different serotypes were isolated. The methods 1, 2 and 3 resulted in 9 (14.5%), 6 (9.6%) and 2 (3.2%) positive samples, respectively. PCR was significantly superior than conventional bacteriology for Salmonella detection only when Rappaport-Vassiliadis was used for DNA-template preparation