Cross-reactions in specific Brachyspira spp. PCR assays caused by “Brachyspira hampsonii” isolates

Abstract

An emerging novel spirochete in swine, provisionally designated "Brachyspira hampsonii," has been detected worldwide. It has been associated with swine dysentery and cannot be differentiated from B. hyodysenteriae, the classical etiologic agent of this disease, using standard phenotypic methods. We evaluated cross-reactions of "B. hampsonii" isolates recovered from avian species in some of the currently available species-specific polymerase chain reaction (PCR) assays for the identification of swine Brachyspira species. Ten avian "B. hampsonii" isolates recovered from wild waterfowl were used. No false-positive results were recorded with a B. pilosicoli-specific PCR based on the amplification of a fragment of the 16S rRNA gene. However, the percentage of false-positive results varied, with a range of 10-80%, in the evaluated B. hyodysenteriae-specific assays based on the amplification of the 23S rRNA, nox, and tlyA genes. Similarly, results of the B. intermedia-specific PCR assays yielded poor specificity, with up to 80% of the "B. hampsonii" isolates tested giving false-positive results. Finally, 2 "B. hampsonii" avian isolates yielded a positive result in a B. innocens- and B. murdochii-specific PCR. This result should be interpreted very cautiously as these 2 isolates could represent a recombinant genotype.

Identification and distribution of Brachyspira species in feces from finishing pigs in Argentina

“…by bacteriology are not a straightforward approach, because of their slow growth and the difficulty of getting isolates in pure culture. At present, different molecular methods are available for detection and identification of Brachyspira species from fecal samples [7,8], or from bacteriological cultures [9], but the protocols need to be updated continuously [10]. One of the most useful genes to assess the diagnosis of Brachyspira spp.…”