SALMONELLA DETECTION BY POLYMERASE CHAIN REACTION AFTER PRE‐ENRICHMENT OF FEED SAMPLES

Abstract

A polymerase chain reaction (PCR) procedure was developed for analysis of viable Salmonella spp. in feed samples and scrapings from feed mills. The objective was to develop a cost‐effective, user‐friendly method that could be performed within ordinary working hours. A single pre‐enrichment was enough for most feed raw materials. However, scrapings and pellets required additional pre‐enrichment. The results indicate that inhibition of the PCR reaction was correlated with a pH value below 7.0 in the first pre‐enrichment. Results of the PCR procedure were in agreement with the established culture‐based Nordic Committee on Food Analysis method in spiked samples. The developed PCR procedure can be used as a routine analysis method for feed samples and samples from a Salmonella feed control program based on hazard analysis critical control point principles.

Validation of a Diagnostic PCR Method for Routine Analysis of Salmonella spp. in Animal Feed Samples

“…Rapeseed has previously been noted to be PCR-inhibitory (Löfström et al 2004) with reduced amplification efficiency using the same PCR method. In contrast, Salomonsson et al (2005) did not have problems with PCR inhibition caused by rapeseed samples when detecting salmonella after pre-enrichment in BPW (Salomonsson et al 2005). However, a larger volume was used for the PCR (50 μl instead of 25 μl in this study), which diluted the inhibitors.…”

“…Hence, there is a growing demand for rapid methods for the detection of Salmonella in feed samples. Polymerase chain reaction (PCR) is considered to be one of the most promising techniques to meet this demand, and several PCR-based detection methods for Salmonella in food and feed have been developed (Hoorfar et al 2000;Salomonsson et al 2005;Löfström et al 2004;Malorny et al 2003aMalorny et al , 2004.…”

Accuracy and Sensitivity of Commercial PCR-Based Methods for Detection of Salmonella enterica in Feed

“…Efficient isolation methods and sampling plans are important tools in tracing scenarios, control programs, and decision-making processes by the industry or authorities. The low levels of Salmonella in compound feed and feed raw ingredients, the dehydration of the Salmonella present, the uneven distribution of contamination in feed commodities, and the high levels of competing aerobic bacteria combine to put great demands on the isolation methods (15,23,39).…”

“…The detection of Salmonella in feed samples may be substantially different since the cells present are stressed via low water activities and numerous bacterial species compete for similar survival niches (39). In addition, PCR methods may be more sensitive for some feed ingredients than for others, a finding that may affect the reported prevalence of Salmonella in different feed ingredients (21).…”

Animal Feed Production and Contamination by Foodborne Salmonella

“…Polymerase chain reaction (PCR) assays have been successfully applied to detection of Salmonella spp. in animal feeds but some cultural preenrichment appears to be generally unavoidable to achieve optimal results Stone et al, 1998;Schrank et al, 2001;Löfström et al, 2004;Salomonsson et al, 2005). To accomplish direct PCR detection several nucleic acid extraction methods and other means to improve bacterial DNA recovery from feed matrices have been examined with limited success (Maciorowski et al, 2001a and.…”