Analysis of HL and O serotypes of Campylobacter strains by the flagellin gene typing system

We recently developed a molecular typing system for Campylobacter jejuni and Campylobacter coli based on restriction fragment length polymorphism analysis of the flagellin gene,flaA (I.Nachamkin, K. Bohachick, and C.M. Patton, J. Clin. Microbiol. 31:1531-1536, 1993). We extended the typing system to 83 flagellin types (designated flaA-1,flaA-2, etc.) on the basis of analysis of 404 isolates of C. jejuni and C. coli including common serotypes isolated in the United States, a selection of less common serotypes, and serotype reference strains. Of the 295 strains previously shown to belong to common HL and O serotypes (C. M. Patton, M.A. Nicholson, S.M. Ostroff, A.A. Ries, I.K. Wachsmuth, and R.V. Tauxe, J. Clin. Microbiol. 31:1525-1530, 1993), six flaA types accounted for 53.6% of strains as follows: flaA-1, 21.7%; flaA-7, 14.9%; flaA-27, 5.1%; flaA-49, 4.4%; flaA-13, 3.7%; and flaA-21, 3.7%. Seventy-five percent of the strains were within 15 flaA types, 90% were within 30 flaA types, and all 295 strains were contained within 52 flaA types. Within each HL or O serotype, there usually were multiple flaA types. For 12 common HL serotypes and 7 common O serotypes, more than 50% of these isolates were a single flaA type. A database was developed by using commercially available restriction fragment length polymorphism analysis software (ProRFLP; DNA ProScan, Inc., Nashville, Tenn.) that should allow other investigators to perform typing with this system.