CHARACTERIZATION OF SEROLOGICALLY NONTYPABLE ACTINOBACILLUS-ACTINOMYCETEMCOMITANS ISOLATES

Our previous studies have shown that Actinobacillus actinomycetemcomit ans isolates of a given arbitrarily primed PCR (AP-PCR) genotype belon g to the same serotype (of serotypes a through e), In the present stud y we investigated whether the AP-PCR genotypes of nonserotypeable A. a ctinomycetemcomitans isolates match those of the serotypeable isolates . The isolates were additionally characterized by restriction analysis of the apaH PCR amplification products. The material included 75 nons erotypeable and 18 serotypeable A. actinomycetemcomitans isolates from 34 epidemiologically unrelated subjects. The serotypeable isolates we re obtained from subjects who also harbored nonserotypeable isolates. Eight AP-PCR genotypes were distinguished among the isolates; six geno types matched those detected in our previous studies, whereas two geno types were new. Intraindividually, the A. actinomycetemcomitans isolat es produced identical AP-PCR banding patterns, regardless of whether t hey were serotypeable or nonserotypeable, in 22 of 23 subjects partici pating with multiple isolates. AP-PCR genotype 3, corresponding to ser otype c, was by far the most common among the nonserotypeable isolates (62% of subjects). Results obtained with the apaH restriction analysi s confirmed the results obtained with AP-PCR for 31 of the 33 subjects . The results suggest that nonserotypeable A. actinomycetemcomitans is olates originate from serotypeable isolates, especially from serotype c isolates, and the likelihood of the existence of additional serotype s is small.