Actinomyces naeslundii genospecies 1 and 2 express different binding specificities to N‐acetyl‐β‐D‐galactosamine, whereas Actinomyces odontolyticus expresses a different binding specificity in colonizing the human mouth

Abstract

A total of 102 strains of Actinomyces were isolated from teeth, buccal mucosa and tongue in eight individuals. The isolates were characterized by multivariate statistical analyses of phenotypic characteristics, serotyping and binding to beta-linked galactosamine (N-acetyl-beta-D-galactosamine) and acidic proline-rich protein structures. Based on these characteristics, isolates were classified into three major groups: (i) Isolates of Actinomyces naeslundii genospecies 2 were the dominant species on teeth and buccal mucosa and bound commonly to N-acetyl-beta-D-galactosamine (63 of 63 isolates) and acidic proline-rich proteins (63 of 63 isolates), regardless of tissue origin. They all exhibited a N-acetyl-beta-D-galactosamine binding specificity signified by N-acetyl-beta-D-galactosamine-inhibitable coaggregation with the streptococcal strains LVG1, GVE1, 24892 and MPB1; (ii) Isolates of A. naeslundii genospecies 1 were prevalent on teeth in certain individuals and bound commonly to N-acetyl-beta-D-galactosamine (20 of 20 isolates), but less commonly to acidic proline-rich proteins (5 of 20 isolates). They all possessed another N-acetyl-beta-D-galactosamine specificity, i.e. N-acetyl-beta-D-galactosamine-inhibitable coaggregation with the same streptococcal strains except for strain MPB1; (iii) Isolates of Actinomyces odontolyticus, the dominant species on the tongue (17 of 19 isolates), bound commonly to unknown structures on streptococci (17 of 19 isolates) but rarely to N-acetyl-beta-D-galactosamine (2 of 19 isolates) or acidic proline-rich proteins (3 of 19 isolates). In conclusion, A. naeslundii genospecies 1 and 2 exhibit different patterns of N-acetyl-beta-D-galactosamine and acidic proline-rich protein specificities to colonize dental and buccal mucosa surfaces, whereas A. odontolyticus utilizes another specificity to colonize the tongue.

Different Type 1 Fimbrial Genes and Tropisms of Commensal and Potentially Pathogenic Actinomyces spp. with Different Salivary Acidic Proline-Rich Protein and Statherin Ligand Specificities

“…A. viscosus and A. naeslundii strains were isolated as previously described (16) Strains were characterized by using the Analytical Profile Index products Rapid ID 32 strp and ID coryne (bioMérieux, Marcy l'Etoile, France), by wholecell protein patterning by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and by whole-cell agglutination with Actinomyces-specific rabbit antisera (G. H. Bowden, University of Manitoba, Winnipeg, Canada) (16,28,36).…”

“…Type 1 fimbriae, which mediate binding to acidic proline-rich proteins (PRPs) and statherin, are more common on A. naeslundii genospecies 2 (an early plaque colonizer) than on genospecies 1 (a late plaque colonizer) (11,16,17). Moreover, while type 1 fimbriae on A. naeslundii of human origin bind ProGln in acidic PRPs, type 1 fimbriae on A. viscosus of rat and hamster origin bind ThrPhe in statherin (28).…”

“…Type 2 fimbriae, which mediate binding to ␤-linked galactose structures, are highly prevalent on both A. naeslundii genospecies 1 and 2. Type 2 fimbriae involve at least four ␤-linked galactose specificities with different coaggregation and biological properties (16,17,45).…”

“…Type 2 fimbriae, which mediate binding to ␤-linked galactose structures, are highly prevalent on both A. naeslundii genospecies 1 and 2. Type 2 fimbriae involve at least four ␤-linked galactose specificities with different coaggregation and biological properties (16,17,45).Biogenesis, assembly, and function of type 1 fimbriae of A. naeslundii strain T14V require the FimP subunit and additional proteins encoded by a cluster of seven genes (orf1 to -6 and fimP) (52). Recently, a type 2 fimbria gene cluster containing three or four genes (ef-TU, orf977, fimA, and orf365) was found in A. naeslundii strain T14V (51) (GenBank accession no.…”

Salivary Statherin Peptide-Binding Epitopes of Commensal and Potentially Infectious Actinomyces spp. Delineated by a Hybrid Peptide Construct

“…naeslundii gsp 2 is an early commensal colonizer of teeth and mucosal surfaces of humans and monkey, whereas A. naeslundii gsp 1 occurs at later stages of oral biofilm development (13). A. viscosus is an oral commensal bacterium in rats and hamsters (8).…”