PCR Serotyping of 29 Aggregatibacter actinomycetemcomitans Strains from Blood Isolates

Objective To determine serotypes of 29 Aggregatibacter actinomycetemcomitans strains from blood isolates by polymerase chain reaction. Methods ATCC 29523 (serotype a), ATCC 43718 (serotype b), ATCC 33384 (serotype c), IDH 781 (serotype d), IDH 1705 (serotype e) and CU 1000 (serotype f) were used as reference strains. Six pairs of oligonucleotide primers specific for gene clusters involved in the biosynthesis of serotype specific polysaccharide antigens were designed. The specificity of the primers were evaluated by the reference strains of Aggregatibacter actinomycetemcomitans. Serotypes of 29 Aggregatibacter actinomycetemcomitans strains from blood iaolates were determined by PCR with the primers. Results Each pair of primers can specifically identify one serotype of Aggregatibacter actinomycetemcomitans. No cross reaction was observed in all strains. The PCR product sizes were: 428 bp (serotype a), 298 bp (serotype b), 559 bp (serotype c), 690 bp (serotype d), 211 bp (serotype e) and 232 bp (serotype f). Of the 29 strains from blood isolates, 16 strains were serotype b (55%), 4 strains were serotype a (14%), 4 strains were serotype c (14%), 2 strains were serotype d (7%), 2 strains were serotype f (7%). One strain could not be serotyped by PCR assay. Conclusion Serotype b was the most frequently detected serotype of the Aggregatibacter actinomycetemcomitans strains from blood isolates. Serotype a and c could be detected more often than the other serotypes.