Aggregatibacter actinomycetemcomitans serotypes infections and periodontal conditions: a two-way assessment.
ABSTRACT This study investigated a large population of individuals positive for A. actinomycetemcomitans and performed a two way analysis assessing the relation between the different serotypes of the bacterium and periodontal conditions. The serotypes analysis (serotypes a, b, c, d, e, f) showed that out of the 204 selected individuals positive for A. actinomycetemcomitans, 152 were positive for a single serotype, 27 showed a variable mixed infection and 25 individuals were not positive for any of the serotypes tested. Serotypes a, b and c were largely found (98%), and serotype c was the most prevalent. Serotypes d, e, and f were either not detected or relatively rare. It was also verified that in non-periodontitis individuals, serotypes a and c were more prevalent (p<0.05); in individuals with mild or moderate/severe chronic periodontitis serotype c was also more common (p<0.05); and aggressive periodontitis subjects showed high prevalence of both serotypes b and c (p<0.05). In conclusion, our study showed that serotype c was the most prevalent in both diseased and healthy subjects. Aggressive periodontitis subjects were not exclusively associated with A. actinomycetemcomitans serotype b. Non-typeable strains were either not detected or were relatively infrequent, and serotypes d and f were not detected in the examined Brazilian population.
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ABSTRACT: The oral bacterium Actinobacillus actinomycetemcomitans is implicated as a causative agent of localized juvenile periodontitis (LJP). A. actinomycetemcomitans is classified into five serotypes (a to e) corresponding to five structurally and antigenically distinct O polysaccharide (O-PS) components of their respective lipopolysaccharide molecules. Serotype b has been reported to be the dominant serotype isolated from LJP patients. We determined the lipopolysaccharide O-PS structure from A. actinomycetemcomitans CU1000, a strain isolated from a 13-year-old African-American female with LJP which had previously been classified as serotype b. The O-PS of strain CU1000 consisted of a trisaccharide repeating unit composed of l-rhamnose and 2-acetamido-2-deoxy-d-galactose (molar ratio, 2:1) with the structure →2)-α-l-Rhap-(1–3)-2-O-(β-d-GalpNAc)-α-l-Rhap-(1→. O-PS from strain CU1000 was structurally and antigenically distinct from the O-PS molecules of the five known A. actinomycetemcomitans serotypes. Strain CU1000 was mutagenized with transposon IS903φkan, and three mutants that were deficient in O-PS synthesis were isolated. All three transposon insertions mapped to a single 1-kb region on the chromosome. The DNA sequence of a 13.1-kb region surrounding these transposon insertions contained a cluster of 14 open reading frames that was homologous to gene clusters responsible for the synthesis of A. actinomycetemcomitans serotype b, c, and e O-PS antigens. The CU1000 gene cluster contained two genes that were not present in serotype-specific O-PS antigen clusters of the other five known A. actinomycetemcomitans serotypes. These data indicate that strain CU1000 should be assigned to a new A. actinomycetemcomitans serotype, designated serotype f. A PCR assay using serotype-specific PCR primers showed that 3 out of 20 LJP patients surveyed (15%) harbored A. actinomycetemcomitans strains carrying the serotype f gene cluster. The finding of an A. actinomycetemcomitans serotype showing serological cross-reactivity with anti-serotype b-specific antiserum suggests that a reevaluation of strains previously classified as serotype b may be warranted.Infection and Immunity 10/2001; · 4.07 Impact Factor
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ABSTRACT: Aggregatibacter actinomycetemcomitans is frequently associated with localized aggressive periodontitis (LAP); however, longitudinal cohort studies relating A. actinomycetemcomitans to initiation of LAP have not been reported. A periodontal assessment was performed on 1,075 primarily African-American and Hispanic schoolchildren, ages 11 to 17 years. Samples were taken from each child for A. actinomycetemcomitans. A cohort of 96 students was established that included a test group of 38 A. actinomycetemcomitans-positive students (36 periodontally healthy and 2 with periodontal pockets) and 58 healthy A. actinomycetemcomitans-negative controls. All clinical and microbiological procedures were repeated at 6-month intervals. Bitewing radiographs were taken annually for definitive diagnosis of LAP. At the initial examination, clinical probing attachment measurements indicated that 1.2% of students had LAP, while 13.7% carried A. actinomycetemcomitans, including 16.7% of African-American and 11% of Hispanic students (P = 0.001, chi-square test). A. actinomycetemcomitans serotypes a, b, and c were equally distributed among African-Americans; Hispanic students harbored predominantly serotype c (P = 0.05, chi-square test). In the longitudinal phase, survival analysis was performed to determine whether A. actinomycetemcomitans-positive as compared to A. actinomycetemcomitans-negative students remained healthy ("survived") or progressed to disease with attachment loss of >2 mm or bone loss (failed to "survive"). Students without A. actinomycetemcomitans at baseline had a significantly greater chance to remain healthy (survive) compared to the A. actinomycetemcomitans-positive test group (P = 0.0001). Eight of 38 A. actinomycetemcomitans-positive and none of 58 A. actinomycetemcomitans-negative students showed bone loss (P = 0.01). A. actinomycetemcomitans serotype did not appear to influence survival. These findings suggest that detection of A. actinomycetemcomitans in periodontally healthy children can serve as a risk marker for initiation of LAP.Journal of Clinical Microbiology 12/2007; 45(12):3859-69. · 4.07 Impact Factor
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ABSTRACT: The phylogeny of 20 Actinobacillus actinomycetemcomitans strains isolated from patients with localized juvenile periodontitis (LJP) was investigated by using partial sequence analysis of 16S rRNA genes, arbitrarily primed PCR (AP-PCR), and four additional PCR assays that amplified polymorphic regions in the leukotoxin (lkt), cytolethal distending toxin (cdt), major fimbrial subunit (flp-1), and serotype-specific O polysaccharide gene clusters. Our analysis also included four strains isolated from healthy subjects and nine reference strains. We found that A. actinomycetemcomitans strains comprised three major phylogenetic lineages. One lineage consisted of serotype b strains, a second lineage consisted of serotype c strains, and a third lineage consisted of serotype a, d, e, and f strains. 16S rRNA sequences within each lineage were highly conserved (<1% base substitutions), whereas sequences between lineages were exceptionally divergent (1.9 to 5.0% substitutions). Two strains exhibited 16S rRNA sequences that were even more distantly related to those of the three major lineages (2.7 to 6.7% substitutions), indicating that additional minor lineages or variants exist. The distribution of 16S rRNA sequences and lkt, cdt, flp-1, and AP-PCR genotypes was consistent with a clonal population structure, with little evidence of assortative recombination between strains of different serotypes. Strains from all three major lineages were recovered from LJP patients, suggesting that phylogenetically diverse strains of A. actinomycetemcomitans carry pathogenic potential.Journal of Clinical Microbiology 04/2002; 40(4):1181-7. · 4.07 Impact Factor