FimA Genotypes and Multilocus Sequence Types of Porphyromonas gingivalis from Periodontitis

Morten Enersen^*, Ingar Olsen, yvind Kvalheim, and Dominique A. Caugant

Institute of Oral Biology, University of Oslo, 0316 Oslo, Norway; Department of Bacteriology and Immunology, Norwegian Institute of Public Health, 0403, Oslo, Norway

^* To whom correspondence should be addressed. Email: morteene{at}odont.uio.no.

	Abstract

Fimbriae are important virulence factors of pathogenic bacteria, facilitating their attachment to host and bacterial cells. In the periodontal pathogen Porphyromonas gingivalis, the fimA gene is classified into six types (I, Ib, II, III, IV and V) based on different nucleotide sequences, with the fimA genotypes II and IV being prevalent in isolates from periodontitis. The aims of this study were to examine the distribution of fimA genotypes in a collection of 82 P. gingivalis isolates from adult periodontitis patients of worldwide origin and to investigate the relationship between the fimA genotypes and sequence types (STs) of the isolates, as determined by multilocus sequence typing (MLST). The fimA gene was amplified by PCR using specific primer sets for each genotype. STs of all strains were assigned according to the MLST database for P. gingivalis (www.pubmlst.org/pgingivalis). The 82 strains showed extensive genetic diversity and were assigned to 69 STs. Only isolates with closely related STs harbored the same fimA genotype. Twenty-eight (34.1%) strains harbored fimA genotype II, while only the reference strain for fimA genotype V reacted with the specific primers for this genotype. Twenty-one isolates (25.6%) were positive in more than one of the fimA PCR assays; the most frequent combinations were I, Ib and II (8 isolates) and I and II (4 isolates). Sequencing of the fimA gene in selected isolates did not support the observed specific fimA genotype combinations, suggesting that the genotyping method used for the major fimbriae in P. gingivalis should be reevaluated.