Differentiation of Campylobacter jejuni and Campylobacter coli by polymerase chain reaction.

A multiplex PCR assay was developed using two primer sets for the identification and differentiation of Campylobacter coli and Campylobacter jejuni. Primer Set I amplifies a 460-bp fragment present in C. coli and C. jejuni. Set II amplifies a 160-bp target unique to C. jejuni. When the assay was performed on reference strains, amplification of C. coli yielded only the 460-bp fragment. Amplification of C. jejuni generated both the 160- and 460-bp fragments. Campylobacter field strains (n = 85) isolated from raw poultry were identified by PCR and by conventional biochemical methods. Species determination by the two methods agreed for 83 of the 85 isolates examined. By PCR, 23 were identified as C. coli and 62 as C. jejuni. One isolate was unidentifiable by biochemical testing. The PCR assay identified this isolated as C. coli. In addition, one strain which was identified as C. coli by biochemical testing was determined to be C. jejuni by PCR. The PCR assay offers an alternative to traditional biochemical typing methods for the identification and differentiation of C. coli and C. jejuni isolated from poultry. It is accurate, simple to perform, and can be completed within 8 h.

Methods Used for Detection and Recovery of Escherichia coli O157:H7 Associated with a Food-Borne Disease Outbreak †.

The current Food Safety and Inspection Service method for detection and recovery of Escherichia coli O157:H7, (including modified EC broth with novobiocin (mEC+n) and a direct blot ELISA). was used to analyze beef and environmental samples during an investigation of a food-borne disease outbreak attributed to consumption of undercooked hamburger patties. Double-modified trypticase soy broth (dmTSB) and a commercially available dipstick immunoassay were also used to improve detection/recovery of E. coli O157:H7. A total of 1,115 beef and environmental samples was screened with the direct blot ELISA and the dipstick immunoassay; 178 presumptive-positive samples (by either or both of the screening methods) were subjected to recovery/isolation procedures. Toxigenic E. coli O157:H7 was recovered from 45 samples: 40 hamburger-patty samples produced on the epidemiologically identified date, 3 hamburger-patty samples produced on another date, and 2 beef briskets. The organism was not recovered from environmental samples. Limited quantitative analyses indicated that contaminated hamburger patties contained fewer than 4.3 CFU of E. coli O157:H7 per g. Atypical, toxigenic ornithine decarboxylase-negative E. coli O157:H7 and nontoxigenic sorbitol-positive E. coli O157:H29 were also recovered. Both enrichment broths gave strong positive reactions with the two immunoassay screening methods, but E. coli O157:H7 was recovered more often from mEC+n broth than from dmTSB. Both screening methods gave positive results for 44 of the 45 beef samples found to contain E. coli O157:H7. False-positive results were frequently observed with both screening methods.