title: Comparison of a real-time PCR method with a culture method for the detection of Salmonella enterica serotype enteritidis in naturally contaminated environmental samples from integrated poultry houses.
abstract: Conventional culture methods have traditionally been considered the "gold standard" for the isolation and identification of foodborne bacterial pathogens. However, culture methods are labor-intensive and time-consuming. A Salmonella enterica serotype Enteritidis-specific  real-time PCR assay that recently received interim approval by the National Poultry Improvement Plan for the detection of Salmonella Enteritidis was evaluated against a culture method that had also received interim National Poultry Improvement Plan approval for the analysis of environmental  samples from integrated poultry houses. The method was validated with 422 field samples collected by either the boot sock or drag swab method. The samples were cultured by selective enrichment in tetrathionate broth followed by transfer onto a modified semisolid Rappaport-Vassiliadis medium  and then plating onto brilliant green with novobiocin and xylose lysine brilliant Tergitol 4 plates. One-milliliter aliquots of the selective enrichment broths from each sample were collected for DNA extraction by the commercial PrepSEQ nucleic acid extraction assay and analysis by the Salmonella  Enteritidis-specific real-time PCR assay. The real-time PCR assay detected no significant differences between the boot sock and drag swab samples. In contrast, the culture method detected a significantly higher number of positive samples from boot socks. The diagnostic sensitivity of  the real-time PCR assay for the field samples was significantly higher than that of the culture method. The kappa value obtained was 0.46, indicating moderate agreement between the real-time PCR assay and the culture method. In addition, the real-time PCR method had a turnaround time of 2  days compared with 4 to 8 days for the culture method. The higher sensitivity as well as the reduction in time and labor makes this real-time PCR assay an excellent alternative to conventional culture methods for diagnostic purposes, surveillance, and research studies to improve food safety.
authors.affiliation: Poultry Diagnostic and Research Center, University of Georgia, Athens, GA 30602, USA.
authors.forename: Bwalya
authors.initials: B
authors.lastname: Lungu
authors.forename: W Douglas
authors.initials: WD
authors.lastname: Waltman
authors.forename: Roy D
authors.initials: RD
authors.lastname: Berghaus
authors.forename: Charles L
authors.initials: CL
authors.lastname: Hofacre
mesh_terms: D000822:Animal Husbandry; D000818:Animals; D002645:Chickens; D015169:Colony Count, Microbial / Q000379:methods* / Q000592:standards; D004783:Environmental Microbiology; D005506:Food Contamination / Q000032:analysis / Q000517:prevention & control; D006799:Housing, Animal; D006801:Humans; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods* / Q000592:standards; D015203:Reproducibility of Results; D012477:Salmonella enteritidis / Q000254:growth & development / Q000302:isolation & purification*; D012680:Sensitivity and Specificity