Multiple locus variable number tandem repeat analysis (MLVA) of the pathogenic intestinal spirochaete Brachyspira pilosicoli

Abstract

Brachyspira pilosicoli is an anaerobic intestinal spirochaete that colonizes the large intestine of various host species, in which it may induce diarrhoea, poor growth rates and a localized colitis known as intestinal (or colonic) spirochaetosis. The spirochaete is considered to be potentially zoonotic. The purpose of the current study was to develop a multiple-locus variable number tandem repeat analysis (MLVA) method as a simple and rapid tool to investigate the molecular epidemiology of B. pilosicoli. The genomic sequence of B. pilosicoli strain 95/1000 was analyzed for potential tandem repeats using the default parameters of the Tandem Repeat Finder program. A total of 22 repeat loci were identified and tested for their presence and variability on a set of 10 B. pilosicoli isolates. Five loci that were present in most isolates and that showed evidence of allelic variation were selected and used with a collection of 119 isolates from different host species and geographical locations. Not all the isolates amplified at all loci, but using the available data a total of 103 VNTR profiles were generated. The discriminatory power of this method was 0.976. A phylogenetic tree constructed from the allelic profiles confirmed the diversity of B. pilosicoli, and the general lack of clustering of strains based on species of origin or geographic origin. Some isolates with known epidemiological links were found to be identical or highly similar. The MLVA method was simple and easy to use, and could readily differentiate between strains of B. pilosicoli. MLVA should prove to be a useful tool for rapid identification of relationships between B. pilosicoli isolates in epidemiological investigations.