Use of an alkaline phosphatase-labeled synthetic oligonucleotide probe for detection of Campylobacter jejuni and Campylobacter coli.

A commercially available synthetic nucleic acid probe (SNAP) conjugated to alkaline phosphatase was compared with standard culture techniques for detecting Campylobacter species. The SNAP was able to detect either 5 ng of C. jejuni DNA or 10(5) CFU of bacteria. The SNAP could also detect DNA extracted from 10(5) CFU in mock-infected stool samples. The SNAP detected C. jejuni and C. coli but showed no reactivity with C. laridis, C. fetus subsp. fetus, C. fetus subsp. venerealis, C. fennelliae, "C. upsaliensis," C. cinaedii, C. fecalis, C. hyointestinalis, C. mucosalis, or Helicobacter (Campylobacter) pylori. The SNAP also showed no cross-reactivity with other enteric pathogens. When applied to pure cultures, the SNAP detected 55 clinical isolates of C. jejuni and 11 clinical isolates of C. coli, with an accuracy of 100%. When applied directly to clinical specimens, the SNAP detected Campylobacter spp. in 19 of 23 culture-positive stool specimens (sensitivity, 82.6%; specificity, 100%). Pure cultures of the Campylobacter strains isolated from the four probe-negative, culture-positive stool specimens gave positive reactions with the SNAP. While the SNAP had excellent sensitivity and specificity for isolated bacterial colony isolates, the main limitation to the Campylobacter probe detection kit may be the sensitivity limit on direct detection of Campylobacter organisms in stools.