Discrete protein determinant directs the species-specific adherence of Porphyromonas gingivalis to oral streptococci.

For pathogens to survive in the human oral cavity, they must identify a suitable niche in the complex multispecies biofilm that exists on oral tissues. The periodontal pathogen Porphyromonas gingivalis adheres to Streptococcus gordonii by interacting with a specific region of the streptococcal SspB polypeptide, designated BAR. However, it does not adhere to Streptococcus mutans, which expresses SpaP, a highly conserved homolog of SspB. Comparison of the predicted secondary structure of BAR with the corresponding region of SpaP suggested that the substitution of Asn for Gly1182 and Val for Pro1185 in SspB may confer a unique local structure that is not conserved in SpaP. A synthetic peptide of 26 amino acids that encompassed residues 1167 to 1193 of SspB promoted avid adherence of P. gingivalis, whereas a peptide derived from the region corresponding to BAR in SpaP was inactive. Substitution of Gly1182 and Pro1185 for Asn1182 and Val1185 in SspB by site-specific mutation generated proteins that were predicted to assume an SpaP-like secondary structure, and the purified proteins did not promote P. gingivalis adherence. Furthermore, Enterococcus faecalis strains expressing the site-specific mutants did not support adherence of P. gingivalis cells. In contrast, P. gingivalis adhered efficiently to E. faecalis strains expressing intact SspB or SspB-SpaP chimeric proteins containing BAR. These results suggest that a region of SspB consisting of 26 amino acids is sufficient to mediate the adherence of P. gingivalis to S. gordonii and that the species specificity of adherence arises from its interaction with a discrete structural determinant of SspB that is not conserved in SpaP.

Intergeneric communication in dental plaque biofilms.

Dental plaque is a complex biofilm that accretes in a series of discrete steps proceeding from a gram-positive streptococcus-rich biofilm to a structure rich in gram-negative anaerobes. This study investigated information flow between two unrelated plaque bacteria, Streptococcus cristatus and Porphyromonas gingivalis. A surface protein of S. cristatus caused repression of the P. gingivalis fimbrial gene (fimA), as determined by a chromosomal fimA promoter-lacZ reporter construct and by reverse transcription-PCR. Signaling activity was associated with a 59-kDa surface protein of S. cristatus and showed specificity for the fimA gene. Furthermore, P. gingivalis was unable to form biofilm microcolonies with S. cristatus. Thus, S. cristatus is capable of modulating virulence gene expression in P. gingivalis, consequently influencing the development of pathogenic plaque.

Biofilm formation by Porphyromonas gingivalis and Streptococcus gordonii.

Confocal scanning laser microscopy (CSLM) was used to visualize and quantify biofilm formation by the oral bacteria Streptococcus gordonii and Porphyromonas gingivalis. A saliva-coated glass coverslip under continuous bacterial challenge and conditions of low shear force was used to investigate attachment to the salivary pellicle and also the effect of cell-cell interactions on the extent of colonization and biofilm development. S. gordonii bound to the salivary pellicle and outcompeted P. gingivalis for attachment sites. Both P. gingivalis and S. gordonii failed to establish substantial biofilm formation independently. However, biofilm formation did occur subsequent to initial adherence of P. gingivalis to S. gordonii cells deposited on the salivary pellicle. The commensal species S. gordonii may, therefore, provide an attachment substrate for colonization and biofilm accretion by the potential pathogen, P. gingivalis.

Effect of provisional luting agents on polyvinyl siloxane impression material.

Eugenol-containing cements have been traditionally selected for seating provisional restorations, but incomplete polymerization of polyvinyl siloxane impression materials has been attributed to these cements. This study clinically evaluated the inhibitory effect on polymerization of a specific polyvinyl siloxane impression material with five luting agents used for provisional restorations. Three of these luting agents contained eugenol, whereas two interim cements did not contain eugenol. A total of 60 human posterior teeth were prepared for complete crowns, fitted for provisional crowns, and cemented with interim luting agents. After 2.5 weeks the provisional crowns were removed, the cement on tooth preparations was removed with an explorer, and impressions were made. The results revealed that none of the luting agents in this investigation had an inhibitory effect on polymerization of polyvinyl siloxane impression materials.

Leukocyte myeloperoxidase and salivary lactoperoxidase: identification and quantitation in human mixed saliva.

Human salivary lactoperoxidase (HS-LP) is synthesized and secreted by the salivary glands, whereas myeloperoxidase (MPO) is found in PMN leukocytes, which migrate into the oral cavity at gingival crevices. HS-LP levels vary with changes in salivary gland function, but increased numbers of MPO-containing leukocytes indicate infection or inflammation of oral tissues. To determine the contribution of each enzyme to the peroxidase activity of mixed-saliva samples, activity was assayed at pH 5.4 with tetramethylbenzidine as the substrate, with and without the inhibitor dapsone (4,4'-diaminodiphenylsulfone). Dapsone blocked the activity of HS-LP but not MPO. The enzymes were also separated and partially purified from the soluble portion of saliva samples and from detergent extracts of the saliva sediment. Chromatographic properties of the proteins were similar to those of LP from bovine milk (BM-LP) and MPO from human leukocytes. The identity and amounts of the enzymes were confirmed by the absorption spectra and by immunoblotting with antibodies to BM-LP and human MPO. Eosinophil peroxidase (EPO), a distinct enzyme found in eosinophilic leukocytes, was not detected by chromatography or with antibodies to human EPO. On average, 75% of the activity in samples from normal donors was due to MPO and 25% to HS-LP. When corrected for the lower specific activity of HS-LP in this assay, the average amount of MPO (3.6 micrograms/mL) was twice the amount of HS-LP (1.9 micrograms/mL). The amount of MPO corresponded to 1 x 10(6) PMN leukocytes/mL of saliva. The enzymes were distributed differently: Eighty-nine percent of the HS-LP was in the soluble portion of saliva, and 78% of the MPO was in the sediment, which contained 51% of the total activity. In contrast to results obtained with PMN leukocytes from blood, detergent was not required for MPO activity to be measured in saliva, indicating that the enzyme was accessible to peroxidase substrates. The results indicate that MPO is responsible for a large portion of peroxidase-catalyzed reactions in mixed saliva. The unique function of HS-LP may be carried out within the salivary glands, prior to secretion into the oral cavity.

Stress, adaptation, and the black individual: implications for nursing education.

It is the responsibility of nurse educators to be knowledgeable regarding the culture of clients and to provide this information to students via relevant classroom and clinical experiences. The nurse educator must provide more than superficial classroom time to the topic of cultural diversity if she/he wants to facilitate students' learning of this content. This pilot study has indicated that the responses selected by black clients when adapting to stressful situations reflect the influence of cultural variables. Recognizing the importance of cultural influences is important because stress can have a debilitating effect on the individual. Nursing interventions to decrease the stress can be effective if the interventions exemplify the cultural background of the client. Knowledge of these variables is attained from curricula which embody and emphasize the cultural uniqueness of individuals.