Comparison of 2 PCR assays on environmental samples cultured forsubsp..

Abstract

subsp.(MAP) is the causal agent of paratuberculosis, a chronic, contagious, and incurable enteric disease of ruminants. An in-house ISPCR assay validated for MAP detection in sheep has been shown to have a higher sensitivity than a commercial PCR and fecal culture. We have now compared the performance of this in-house ISPCR assay with a commercial ISMapPCR assay for the detection of MAP DNA in bovine dairy farm environmental samples. We purposefully selected 30 culture-positive, 62 culture-negative, and 62 non-interpretable environmental samples. We applied the ISPCR assay directly to the frozen inoculum of these samples. Inocula were incubated in an automated system, and growth was confirmed by an acid-fast bacilli stain and the ISPCR assay. Among culture-positive samples before incubation, the ISPCR assay yielded significantly more positive results than the ISMapPCR assay; however, among culture-negative samples, the ISPCR assay yielded positive results both before and after incubation. The ISMapPCR assay did not flag positively among the culture-negative samples either before or after incubation. The ISPCR assay is a sensitive method that can be used to detect MAP DNA in environmental samples before incubation. The ISMapPCR assay is a specific method used to detect MAP DNA in environmental samples both before and after incubation.