A four‐quadrant sequential streak technique to evaluate Campylobacter selective broths for suppressing background flora in broiler carcass rinses

Abstract

AbstractA semi‐quantitative ecometric technique was used to evaluate efficacy of selective culture media. It involved a standardized chronological streaking technique, leading to ever‐decreasing number of colonies. The objective was to evaluate the efficacy of this technique (four‐quandrant sequential streak [FQS]) with two commonly used Campylobacter broths (Bolton's and Tecra) with whole carcass rinses of post‐pick broilers (n = 30) obtained from a commercial processing plant. Ten ?L from each sample type was streaked (five individual streak lines) onto one quarter of a Campy‐cefex agar plate and sequentially into the next three quadrants. Growth of extraneous bacteria was expressed as an absolute growth index (AGI). A significant (P < 0.05) difference in background microflora suppression was observed using this procedure. A positive correlation between decreasing levels of background microflora within the broths was observed as the AGI declined. FQS can be used for rapid semi‐quantitative estimation of an enrichment broth's efficacy.Practical applicationsThe heavy presence of extraneous background microorganisms on a selective agar plate is a serious deterrent to the accurate detection of a target organism. This study confirmed sequential streaking as an appropriate and easily applied method to evaluate the relative efficiency of selective enrichment broths for Campylobacter in the suppression of background microflora on selective plates. The four‐quadrant sequential streak (FQS) ecometric technique is an inexpensive, rapid, semi‐quantitative method to evaluate the effectiveness of various selective enrichment broths.