Evaluation of a commercial colorimetric fecal dipstick assay for the detection of Helicobacter hepaticus infections in laboratory mice

Abstract

Mice used in biomedical research typically are tested for the presence of Helicobacter spp., including Helicobacter hepaticus. Here we evaluated the ability of a commercially available colorimetric Helicobacter dipstick assay to detect H. hepaticus in experimentally and naturally infected mice, with use of a Helicobacter PCR assay as the 'gold standard' test. None of the fecal samples from experimentally infected A/JCr mice (n = 12) tested positive for Helicobacter by the colorimetric dipstick test. In naturally infected A/JCr and C57BL/6 mice, 11% (1 of 9) and 30% (3 of 10) of fecal samples, respectively, tested positive for Helicobacter by the colorimetric dipstick assay. In these 3 groups of H. hepaticus-infected mice, statistically fewer mice tested positive by the colorimetric dipstick test than by PCR. The colorimetric Helicobacter dipstick assay had an overall diagnostic sensitivity of 13%, diagnostic specificity of 94%, and analytical sensitivity of 10(8) H. hepaticus cfu/mL. As currently formulated, the colorimetric dipstick assay had high specificity but lacked sensitivity for detecting H. hepaticus infections in 2 strains of mice commonly used in research, thereby limiting its utility as a diagnostic screening test for H. hepaticus infections in research mice.

Figure 1.

Percentages of fecal samples from A/JCr mice (A/J; n = 12) experimentally inoculated with H. hepaticus and A/JCr mice (n = 9) and C57BL/6 mice (B6; n = 10) naturally infected with H. hepaticus that tested positive for Helicobacter spp. by a colorimetric dipstick assay or a Helicobacter PCR assay. The same fecal sample from individual mice was tested by using both assays. The number of samples testing positive or negative was used for statistical analysis. *, P < 0.01 compared with mice of the same strain and method of infection.