Evaluation of PCR amplification from fixed caecal tissue to determine the infection of experimentally infected laying hens with Brachyspira pilosicoli

Avian intestinal spirochaetosis (AIS) is a condition arising from colonization of the caeca and colon of birds with anaerobic spirochaetes of the genus Brchyspira. The purpose of the present study was to evaluate PCR amplification from formalin-fixed, paraffin-embedded tissue method for detecting infected laying hens with Brachyspira pilosicoli  with the same primers that have been used for detecting the infection in live birds. Over a 4-week period following experimental infection, the faeces of three of the eight inoculated birds became culture-positive. At post-mortem examination, no specific pathological changes were found, and in histological examination of caeca, no forming a “false brush border” was observed, but the spirochaete-form bacteria were present between the intestinal villi. Faecal and swab cultures from caeca of three infected birds became positive and confirmed by PCR amplification of 16S rRNA gene of B. pilosicoli. But this gene was not detected by PCR amplification from fixed caecal tissues of infected birds. This result might be due to low number of bacteria in each section or damage and fragmentation of target DNA.