TABLE 3.
Hybridization of full-length and central fimP (type 1) and fimA (type 2) gene probes with chromosomal DNA from an independent reference collection of Actinomyces strains and with DNA from a single strain characterized by a statherin binding pattern
| Strain or coaggregation group (strain) | Speciesa | Degree of hybridization tob:
|
Binding specificityc
|
||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
|
fimP fimbrial gene
|
fimA fimbrial gene
|
||||||||||
| Full-length probe | Central probe | Full-length probe | Central probes
|
APRPs
|
GalNAcβ
|
Unknown structure | |||||
| 2:1 | 2:2 | APRP-1 | Stath. | 2:1 | 2:2 | ||||||
| Reference strainsb | |||||||||||
| LY7 | A. naeslundii genospecies 2 | 6 | 6 | 4 | 0 | 3 | + | (+) | − | + | − |
| ATCC 12104T | A. naeslundii genospecies 1 | 3 | 0 | 6 | 6 | 0 | − | − | + | − | − |
| Coaggregation groupsd | |||||||||||
| A (T14V) | A. naeslundii genospecies 2 | 6 | 6 | 4 | 0 | 3 | + | (+) | − | + | − |
| B (PK19) | A. naeslundii genospecies 1 | 3 | 0 | 6 | 5 | 0 | − | − | + | − | − |
| C (PK947) | A. naeslundii genospecies 1 | 6 | 5 | 6 | 4 | 0 | − | − | + | − | − |
| D (PK606) | A. naeslundii genospecies 1 | 5 | 5 | 6 | 4 | 0 | − | − | + | − | − |
| E (PK984) | A. odontolyticus | 2 | 0 | 5 | 0 | 0 | − | − | − | − | + |
| F (PK1259) | A. naeslundii genospecies 2 | 4 | 3 | 4 | 0 | 1 | + | (+) | − | + | − |
| Statherin binding straine ATCC 19246 | A. naeslundii genospecies 2 | 6 | 0 | 5 | 0 | 0 | (+) | + | − | − | − |
The isolates were identified by multivariate statistical analyses of phenotypic characteristics, serological reactions, and proteins banding patterns of cell extracts analyzed by SDS-PAGE (18).
The type 1 DNA probes were generated from the fimP fimbrial subunit gene of A. naeslundii T14V, and the type 2:1 and type 2:2 DNA probes were generated from the fimA type 2 fimbrial genes of A. naeslundii ATCC 12104T and A. naeslundii P-1-N (CCUG 33910), respectively. The probes were labeled with digoxigenin and used in slot blot hybridization with chromosomal DNA from isolates of Actinomyces spp. under high-stringency conditions. The degree of hybridization was scored from 0 to 6 according to the following densitometric values: 0 = <0.01, 1 = 0.01 to <0.04, 2 × 0.04 to <0.10, 3 = 0.10 to <0.16, 4 = 0.16 to <0.22, 5 = 0.22 to <0.27, and 6 = ≥0.27. Essentially identical results were obtained under low-stringency conditions.
APRP or statherin (Stath.) specificity denotes binding to acidic proline-rich proteins (APRPs) or statherin adsorbed onto hydroxyapatite beads, respectively (18, 19). A negative binding result (−) means complete absence of visible binding, and a positive binding result [+ and (+)] indicates that more than 15% of bacteria adhered to the protein-treated beads. A strong positive binding result, +, indicates markedly more binding than a low positive result, (+). GalNAcβ specificity denotes hemagglutination and aggregation of Actinomyces strains with an established collection of streptococcal strains in a GalNAcβ1-3Galα-O-ethyl-inhibitable fashion (18, 19). The different GalNAcβ specificities, types 2:1 and 2:2, denote different aggregation patterns with S. oralis Ss34 and MPB1: type 2:1 coaggregates with both strains, while type 2:2 coaggregates only with Ss34 (18, 19). Binding specificity to unknown structures denotes aggregation with streptococci that was not inhibitable by GalNAcβ1-3Galα-O-ethyl (18, 19).
The coaggregation groups A to F include strains showing adherence properties typically found in an independent reference collection of Actinomyces strains with a mainly subgingival plaque origin (28).
Statherin binding denotes a preferential binding to statherin over APRPs adsorbed onto hydroxyapatite beads (41).