Characterization of serologically nontypeable Actinobacillus actinomycetemcomitans isolates

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Actinobacillus actinomycetemcomitans isolates with the same arbitrarily primed PCR (AP-PCR) genotype typically share the same serotype (a-e).
• Nonserotypeable strains of A. actinomycetemcomitans present a challenge for accurate classification and epidemiological tracking.

Purpose of the Study:

• To determine if nonserotypeable A. actinomycetemcomitans isolates share AP-PCR genotypes with serotypeable isolates.
• To investigate the relationship between serotypeable and nonserotypeable A. actinomycetemcomitans strains within the same subjects.

Main Methods:

• Arbitrarily primed PCR (AP-PCR) genotyping of 75 nonserotypeable and 18 serotypeable A. actinomycetemcomitans isolates.
• Restriction analysis of apaH PCR amplification products for confirmation.
• Analysis of isolates from 34 subjects, including those with both serotypeable and nonserotypeable strains.

Main Results:

• Eight AP-PCR genotypes were identified; six matched previous findings, and two were novel.
• Intra-individual isolates, regardless of serotypeability, showed identical AP-PCR patterns in 22 of 23 subjects.
• AP-PCR genotype 3 (serotype c) was most prevalent among nonserotypeable isolates (62%).
• ApaH restriction analysis results corroborated AP-PCR findings for 31 subjects.

Conclusions:

• Nonserotypeable A. actinomycetemcomitans isolates likely originate from serotypeable strains, particularly serotype c.
• The probability of additional, undiscovered serotypes is considered low based on genotypic concordance.