Variation in the limit-of-detection of the ProSpecT Campylobacter microplate enzyme immunoassay in stools spiked with emerging Campylobacter species.
Campylobacter enteritis in humans is primarily associated with C. jejuni/coli infection. The impact of other Campylobacter spp. is likely to be underestimated due to the bias of culture methods towards Campylobacter jejuni/coli diagnosis. Stool antigen tests are becoming increasingly popular and appear generally less species-specific. A review of independent studies of the ProSpecT® Campylobacter Microplate enzyme immunoassay (EIA) developed for C. jejuni/coli showed comparable diagnostic results to culture methods but the examination of non-jejuni/coli Campylobacter spp. was limited and the limit-of-detection (LOD), where reported, varied between studies. This study investigated LOD of EIA for Campylobacter upsaliensis, Campylobacter hyointestinalis and Campylobacter helveticus spiked in human stools. Multiple stools and Campylobacter isolates were used in three different concentrations (10(4)-10(9)CFU/ml) to reflect sample heterogeneity. All Campylobacter species evaluated were detectable by EIA. Multivariate analysis showed LOD varied between Campylobacter spp. and faecal consistency as fixed effects and individual faecal samples as random effects. EIA showed excellent performance in replicate testing for both within and between batches of reagents, in agreement between visual and spectrophotometric reading of results, and returned no discordance between the bacterial concentrations within independent dilution test runs (positive results with lower but not higher concentrations). This study shows how limitations in experimental procedures lead to an overestimation of consistency and uniformity of LOD for EIA that may not hold under routine use in diagnostic laboratories. Benefits and limitations for clinical practice and the influence on estimates of performance characteristics from detection of multiple Campylobacter spp. by EIA are discussed.
(m)EpiLab, Infectious Disease Research Centre, Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand.
Krunoslav
K
Bojanić
(m)EpiLab, Infectious Disease Research Centre, Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand. Electronic address: A.C.Midwinter@massey.ac.nz.
Anne Camilla
AC
Midwinter
(m)EpiLab, Infectious Disease Research Centre, Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand.
Jonathan Craig
JC
Marshall
(m)EpiLab, Infectious Disease Research Centre, Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand; MedLab Central Limited, Palmerston North, New Zealand.
Lynn Elizabeth
LE
Rogers
(m)EpiLab, Infectious Disease Research Centre, Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand.
Patrick Jon
PJ
Biggs
Veterinary Teaching Hospital, Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand.
Els
E
Acke
D058491:Bacterial Load; D002169:Campylobacter Infections / Q000175:diagnosis / Q000382:microbiology; D017000:Campylobacter coli / Q000201:enzymology / Q000276:immunology / Q000302:isolation & purification*; D016123:Campylobacter jejuni / Q000201:enzymology / Q000276:immunology / Q000302:isolation & purification; D004797:Enzyme-Linked Immunosorbent Assay; D005243:Feces / Q000382:microbiology*; D006801:Humans; D007124:Immunoenzyme Techniques; D057230:Limit of Detection; D016133:Polymerase Chain Reaction; D012680:Sensitivity and Specificity
Analytical sensitivity; Campylobacter; Concordance; Elisa; Faecal consistency; Heterogeneous sample; Performance characteristics