Detection of non-jejuni and-coli Campylobacter Species from Stool Specimens with an Immunochromatographic Antigen Detection Assay

The STAT! Campy immunochromatographic assay for Campylobacter antigen was compared to culture for 500 clinical stool specimens. Antigen was detected in six culture-negative, PCR-positive specimens. C. upsaliensis, a pathogenic species that is tra-ditionally difficult to recover in routine stool cultures, was detected in two of these culture-negative specimens. This study pro-vides evidence that antigen testing may cross-react with at least one additional non-jejuni and-coli Campylobacter species that may be missed by routine culture for campylobacteriosis. Campylobacter spp. are fastidious bacteria that may be difficultto recover in culture due to suboptimal specimen transport and/or storage conditions and lack of universal culture proce-dures. However, Campylobacter antigens may persist in clinical specimens in the absence of viable organisms. The variable clinical specificity reported for several commercially available Campylo-bacter antigen detection assays remains unresolved in the litera-ture (1–4). Several studies have reported higher numbers of anti-gen-positive than of culture-positive specimens (1, 2, 5), but it is unclear whether these are simply false-positive results or are due to Campylobacter spp. in the specimens that are nonviable, viable but nonculturable, or not readily cultivated under commonly employed conditions. This study sought to determine whether culture-negative, antigen-positive specimens, as determined by immunochromatographic assay, actually contained difficult-to-culture Campylobacter spp. which could explain the antigen pos-itivity. In addition, we examined the stability and cross-reactivity profile of the immunochromatographic assay to further define the performance characteristics of the test. A total of 500 fecal specimens submitted over 4months (July to September 2011 and June 2012) for routine stool culture or Cam-pylobacter-specific culture were tested with the Immunocar