Aggregatibacter actinomycetemcomitans serotypes and DGGE subtypes in Thai adults with chronic periodontitis

• A. actinomycetemcomitans non-serotypeable strains were predominant in Thai patients with chronic periodontitis.
• Two strains of A. actinomycetemcomitans had a JP2 like deletion of the leukotoxin gene and, classified as serotype c.
• Two strains of A. actinomycetemcomitans had an insertion in the leukotoxin gene and, classified as serotype c.
• DGGE could classify A. actinomycetemcomitans non-serotypeable strains into 16 subtypes.
• Up to 4 subtypes of A. actinomycetemcomitans could be isolated from the same deep periodontal pocket.

ObjectiveTo investigate the distribution of Aggregatibacter actinomycetemcomitans serotypes and DGGE subtypes among isolates from Thai chronic periodontitis patients.DesignForty-four adult Thai periodontitis patients were assessed by a full mouth recording for CAL, PPD, and BOP. Seventy-nine strains of A. actinomycetemcomitans were isolated from deep pockets on selective TSBV agar and 17 strains were isolated from shallow pockets. The strains were serotyped using PCR and subtyped using DGGE.ResultsThe prevalence of A. actinomycetemcomitans was 84.1%. Non-serotypeable A. actinomycetemcomitans strains occurred equally frequent as serotypeable (54.5%); serotype a 18.2%, serotype c 15.9%, serotype e 9.1%, and serotype f 11.4%. Serotype b and d were not detected. A JP2 like strain but serotyped as c was isolated from two patients, and another two strains showed an 886 bp insertion on the ltx promoter of their A. actinomycetemcomitans isolates. DGGE typing disclosed 16 different subtypes among the non-serotypeable strains. Two of them (NS1 and NS2) were more common (12.7 and 10.1%) among the strains than the other 14 subtypes (˂5.1%). Most patients showed only one subtype (32.4%) but 29.7% had 2 and 3 different subtypes while 8.1% revealed 4 subtypes in one and the same deep pocket.ConclusionThis study showed a greater subtype diversity of A. actinomycetemcomitans predominated by non-serotypeable strains than previously reported in an adult Thai population. It was also revealed for the first time that isolates with a 530 bp deletion or 886 bp insertion of the ltx promoter were serotyped as serotype c.