Genotyping Campylobacter jejuni by comparative genome indexing: an evaluation with pulsed-field gel electrophoresis and flaA SVR sequencing.

Comparative genome indexing (CGI) using whole-genome DNA microarrays was evaluated as a means of genotyping Campylobacter jejuni relative to two standard methods, pulsed-field gel electrophoresis (PFGE) and flaA short variable region sequencing (flaA SVR typing). Thirty-six geographically diverse C. jejuni isolates were selected from a collection of cattle and chicken isolates. The BioNumerics software program was used for cluster analysis of the data from all 36 isolates for each of the three typing methods. Comparative genome indexing assigned a unique type to each isolate while PFGE and flaA SVR distinguished 29 and 35 different types, respectively. The four common types identified by PFGE were also closely related by CGI, and the overall similarity of the CGI results to those for PFGE indicates the value of CGI as a more informative alternative to PFGE. While flaA SVR was very discriminative, the isolates were all highly similar (>78%) resulting in finer distinctions between isolates and fewer genotypic relations to CGI or PFGE. Campylobacter jejuni is one of the most common causative agents of bacterial gastroenteritis in the world. The development of CGI as a molecular typing tool for C. jejuni offers a highly effective and informative means of further understanding the epidemiology of this ubiquitous pathogen.