Periodontal Effects of the Reversible Dipeptidyl Peptidase 1 Inhibitor Brensocatib in Bronchiectasis

AIMS

Brensocatib is a reversible inhibitor of dipeptidyl peptidase 1 (cathepsin C), in development to treat chronic non-cystic fibrosis bronchiectasis. The phase 2, randomized, placebo-controlled WILLOW trial (NCT03218917) was conducted to examine whether brensocatib reduced the incidence of pulmonary exacerbations. Brensocatib prolonged the time to the first exacerbation and led to fewer exacerbations than placebo. Because brensocatib potentially affects oral tissues due to its action on neutrophil-mediated inflammation, we analyzed periodontal outcomes in the trial participants.

MATERIALS AND METHODS

Patients with bronchiectasis were randomized 1:1:1 to receive once-daily oral brensocatib 10 or 25 mg or placebo. Periodontal status was monitored throughout the 24-week trial in a prespecified safety analysis. Periodontal pocket depth (PPD) at screening, week 8, and week 24 was evaluated. Gingival inflammation was evaluated by a combination of assessing bleeding upon probing and monitoring the Löe-Silness Gingival Index on 3 facial surfaces and the mid-lingual surface.

RESULTS

At week 24, mean ± SE PPD reductions were similar across treatment groups: -0.07 ± 0.007, -0.06 ± 0.007, and -0.15 ± 0.007 mm with brensocatib 10 mg, brensocatib 25 mg, and placebo, respectively. The distribution of changes in PPD and the number of patients with multiple increased PPD sites were similar across treatment groups at weeks 8 and 24. The frequencies of gingival index values were generally similar across treatment groups at each assessment. An increase in index values 0-1 and a decrease in index values 2-3 over time and at the end of the study were observed in all groups, indicating improved oral health.

CONCLUSIONS

In patients with non-cystic fibrosis bronchiectasis, brensocatib 10 or 25 mg had an acceptable safety profile after 6 months' treatment, with no changes in periodontal status noted. Improvement in oral health at end of the study may be due to regular dental care during the trial and independent of brensocatib treatment.

KNOWLEDGE TRANSFER STATEMENT

The results of this study suggest that 24 weeks of treatment with brensocatib does not affect periodontal disease progression. This information can be used by clinicians when considering treatment approaches for bronchiectasis and suggests that the use of brensocatib will not be limited by periodontal disease risks. Nevertheless, routine dental/periodontal care should be provided to patients irrespective of brensocatib treatment.

Oral Sciences PhD Program Enrollment, Graduates, and Placement: 1994 to 2016

For decades, dental schools in the United States have endured a significant faculty shortage. Studies have determined that the top 2 sources of dental faculty are advanced education programs and private practice. Those who have completed both DDS and PhD training are considered prime candidates for dental faculty positions. However, there is no national database to track those trainees and no evidence to indicate that they entered academia upon graduation. The objective of this study was to assess outcomes of dental school-affiliated oral sciences PhD program enrollment, graduates, and placement between 1994 and 2016. Using the American Dental Association annual survey of advanced dental education programs not accredited by the Commission on Dental Accreditation and data obtained from 22 oral sciences PhD programs, we assessed student demographics, enrollment, graduation, and placement. Based on the data provided by program directors, the average new enrollment was 33, and graduation was 26 per year. A total of 605 graduated; 39 did not complete; and 168 were still in training. Among those 605 graduates, 211 were faculty in U.S. academic institutions, and 77 were faculty in foreign institutions. Given that vacant budgeted full-time faculty positions averaged 257 per year during this period, graduates from those oral sciences PhD programs who entered academia in the United States would have filled 9 (3.6%) vacant faculty positions per year. Therefore, PhD programs have consistently generated only a small pipeline of dental school faculty. Better mentoring to retain talent in academia is necessary. Stronger support and creative funding plans are essential to sustain the PhD program. Furthermore, the oral sciences PhD program database should be established and maintained by dental professional organizations to allow assessments of training models, trends of enrollment, graduation, and placement outcomes.

Activation of the TREM-1 pathway in human monocytes by periodontal pathogens and oral commensal bacteria

Periodontitis is a highly prevalent disease caused in part by an aberrant host response to the oral multi-species biofilm. A balance between the oral bacteria and host immunity is essential for oral health. Imbalances in the oral microbiome lead to an uncontrolled host inflammatory response and subsequent periodontal disease (i.e. gingivitis and periodontitis). TREM-1 is a signaling receptor present on myeloid cells capable of acting synergistically with other pattern recognition receptors leading to amplification of inflammatory responses. The aim of this study was to investigate the activation of the TREM-1 pathway in the human monocyte-like cell line THP-1 exposed to both oral pathogens and commensals. The relative expression of the genes encoding TREM-1 and its adapter protein DAP12 were determined by quantitative real-time polymerase chain reaction. The surface expression of TREM-1 was determined by flow cytometry. Soluble TREM-1 and cytokines were measured by enzyme-linked immunosorbent assay. The results demonstrate that both commensal and pathogenic oral bacteria activate the TREM-1 pathway, resulting in a proinflammatory TREM-1 activity-dependent increase in proinflammatory cytokine production.

Oral biology in middle age: a history of the University at Buffalo Oral Biology PhD Program

In 1960, the first Department of Oral Biology in the United States dedicated to the conduct of research, graduate biomedical research education, and the provision of basic oral science education for the DDS curriculum was established at the University at Buffalo. In 1963, the Department organized the first PhD Program in Oral Biology in the United States. This PhD program has produced a large cadre of oral health researchers, many of whom have gone on to make major contributions to dental research and education. This article provides a brief history of the program, the context within which the program was organized and developed, and a description of some of the many faculty, students, and fellows associated with the program. Additionally, to celebrate the 50th anniversary of this program, a symposium, entitled "The Oral Microbiome, Immunity and Chronic Disease", was held on June 12-14, 2013, in Buffalo, New York. The proceedings are published online in Advances in Dental Research (2014, Vol. 26).

Streptococcus mutans out-competes Streptococcus gordonii in vivo

Streptococcus gordonii and Streptococcus mutans avidly colonize teeth. S. gordonii glucosyltransferase (GtfG) and amylase-binding proteins (AbpA/AbpB), and S. mutans glucosyltransferase (GtfB), affect their respective oral colonization abilities. We investigated their interrelationships and caries association in a rat model of human caries, examining the sequence of colonization and non- vs. high-sucrose diets, the latter being associated with aggressive decay in humans and rats. Virulence-characterized wild-types of both species and well-defined mutants of S. gordonii with interrupted abpA and gtfG genes were studied. While both S. gordonii and S. mutans were abundant colonizers of rat's teeth in the presence of either diet, if inoculated singly, S. mutans always out-competed S. gordonii on the teeth, independent of diet, strain of S. mutans, simultaneous or sequential inoculation, or presence/absence of mutations of S. gordonii's abpA and gtfG genes known to negatively or positively affect its colonization and to interact in vitro with S. mutans GtfB. S. mutans out-competed S. gordonii in in vivo plaque biofilm. Caries induction reflected S. mutans or S. gordonii colonization abundance: the former highly cariogenic, the latter not. S. gordonii does not appear to be a good candidate for replacement therapy. These results are consistent with human data.

Novel iron-regulated and Fur-regulated small regulatory RNAs in Aggregatibacter actinomycetemcomitans

Iron can regulate biofilm formation via non-coding small RNA (sRNA). To determine if iron-regulated sRNAs are involved in biofilm formation by the periodontopathogen Aggregatibacter actinomycetemcomitans, total RNA was isolated from bacteria cultured with iron supplementation or chelation. Transcriptional analysis demonstrated that the expression of four sRNA molecules (JA01-JA04) identified by bioinformatics was significantly upregulated in iron-limited medium compared with iron-rich medium. A DNA fragment encoding each sRNA promoter was able to titrate Escherichia coli ferric uptake regulator (Fur) from a Fur-repressible reporter fusion in an iron uptake regulator titration assay. Cell lysates containing recombinant AaFur shifted the mobility of sRNA-specific DNAs in a gel shift assay. Potential targets of these sRNAs, determined in silico, included genes involved in biofilm formation. The A. actinomycetemcomitans overexpressing JA03 sRNA maintained a rough phenotype on agar, but no longer adhered to uncoated polystyrene or glass, although biofilm determinant gene expression was only modestly decreased. In summary, these sRNAs have the ability to modulate biofilm formation, but their functional target genes remain to be confirmed.

Effect of starch and amylase on the expression of amylase-binding protein A in Streptococcus gordonii

Streptococcus gordonii is a common oral commensal bacterial species in tooth biofilm (dental plaque) and specifically binds to salivary amylase through the surface exposed amylase-binding protein A (AbpA). When S. gordonii cells are pretreated with amylase, amylase bound to AbpA facilitates growth with starch as a primary nutrition source. The goal of this study was to explore possible regulatory effects of starch, starch metabolites and amylase on the expression of S. gordonii AbpA. An amylase ligand-binding assay was used to assess the expression of AbpA in culture supernatants and on bacterial cells from S. gordonii grown in defined medium supplemented with 1% starch, 0.5 mg ml(-1) amylase, with starch and amylase together, or with various linear malto-oligosaccharides. Transcription of abpA was determined by reverse transcription quantitative polymerase chain reaction. AbpA was not detectable in culture supernatants containing either starch alone or amylase alone. In contrast, the amount of AbpA was notably increased when starch and amylase were both present in the medium. The expression of abpA was significantly increased (P < 0.05) following 40 min of incubation in defined medium supplemented with starch and amylase. Similar results were obtained in the presence of maltose and other short-chain malto-oligosacchrides. These results suggest that the products of starch hydrolysis produced from the action of salivary α-amylase, particularly maltose and maltotriose, up-regulate AbpA expression in S. gordonii.

The Influence of Salivary Proteins on the Growth, Aggregation and Surface Properties of Hydroxyapatite Particles

The adsorption and crystal growth effects of salivary cystatin SA-II and non-glycosylated amylase on hydroxyapatite have been compared to the effects of the salivary cystatins SA-I and SA-III. Amylase was the least active HAP crystal growth inhibitor and adsorbed weakly to HAP. Although the three cystatins were active inhibitors of hydroxyapatite crystal growth in supersaturated solution, their affinities showed marked differences.

Identification and characterization of amylase-binding protein C from Streptococcus mitis NS51

A substantial proportion of the streptococcal species found in dental plaque biofilms are able to interact with the abundant salivary enzyme alpha-amylase. These streptococci produce proteins that specifically bind amylase. An important plaque species, Streptococcus mitis, secretes a 36-kDa amylase-binding protein into the extracellular milieu. Proteins precipitated from S. mitis NS51 cell culture supernatant by the addition of purified salivary amylase were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, transferred to a membrane, and a prominent 36-kDa band was cut from the membrane and sequenced to yield the N-terminal amino acid sequence DSQAQYSNGV. Searching the S. mitis genome sequence database revealed a single open reading frame containing this sequence, and the gene was amplified by the S. mitis genomic DNA polymerase chain reaction. The coding region of this open reading frame, designated amylase-binding protein C (AbpC), was cloned into an Escherichia coli expression vector and the recombinant AbpC (rAbpC) was purified from the soluble fraction of the E. coli cell lysate. Purified AbpC was found to interact with immobilized amylase, confirming AbpC as a new streptococcal amylase-binding protein.

Oral biofilms, periodontitis, and pulmonary infections

Bacteria from the oral biofilms may be aspirated into the respiratory tract to influence the initiation and progression of systemic infectious conditions such as pneumonia. Oral bacteria, poor oral hygiene, and periodontitis seem to influence the incidence of pulmonary infections, especially nosocomial pneumonia episodes in high-risk subjects. Improved oral hygiene has been shown to reduce the occurrence of nosocomial pneumonia, both in mechanically-ventilated hospital patients and non-ventilated nursing home residents. It appears that oral colonization by potential respiratory pathogens, possibly fostered by periodontitis, and possibly by bacteria specific to the oral cavity or to periodontal diseases contribute to pulmonary infections. Thus, oral hygiene will assume an even more important role in the care of high-risk subjects--patients in the hospital intensive care and the elderly. The present paper critically reviews the recent literature on the effect of oral biofilms and periodontitis on pneumonia.

Oral biofilms, periodontitis, and pulmonary infections

Bacteria from the oral biofilms may be aspirated into the respiratory tract to influence the initiation and progression of systemic infectious conditions such as pneumonia. Oral bacteria, poor oral hygiene, and periodontitis seem to influence the incidence of pulmonary infections, especially nosocomial pneumonia episodes in high-risk subjects. Improved oral hygiene has been shown to reduce the occurrence of nosocomial pneumonia, both in mechanically-ventilated hospital patients and non-ventilated nursing home residents. It appears that oral colonization by potential respiratory pathogens, possibly fostered by periodontitis, and possibly by bacteria specific to the oral cavity or to periodontal diseases contribute to pulmonary infections. Thus, oral hygiene will assume an even more important role in the care of high-risk subjects--patients in the hospital intensive care and the elderly. The present paper critically reviews the recent literature on the effect of oral biofilms and periodontitis on pneumonia.

Streptococcus gordonii's sequenced strain CH1 glucosyltransferase determines persistent but not initial colonization of teeth of rats

OBJECTIVE

Extracellular glucan synthesis from sucrose by Streptococcus gordonii, a major dental plaque biofilm bacterium, is assumed important for colonization of teeth; but this hypothesis is un-tested in vivo.

METHODS

To do so, we studied an isogenic glucosyltransferase (Gtf)-negative mutant (strain AMS12, gtfG(-)) of S. gordonii sequenced wild type (WT, strain Challis CH1, gtfG(+)), comparing their in vitro abilities to grow in the presence of glucose and sucrose and, in vivo, to colonize and persist on teeth and induce caries in rats. Weanling rats of two breeding colonies, TAN:SPFOM(OM)BR and TAN:SPFOM(OMASF)BR, eating high sucrose diet, were inoculated with either the WT (gtfG(+)), its isogenic gtfG(-) mutant, or reference strains of Streptococcus mutans. Control animals were not inoculated.

RESULTS

In vitro, the gtfG(-) strain grew at least as rapidly in the presence of sucrose as its WT gtfG(+) progenitor, but formed soft colonies on sucrose agar, consistent with its lack of insoluble glucan synthesis. It also had a higher growth yield due apparently to its inability to channel carbon flow into extracellular glucan. In vivo, the gtfG(-) mutant initially colonized as did the WT but, unlike the WT, failed to persist on the teeth as shown over time. By comparison to three S. mutans strains, S. gordonii WT, despite its comparable ecological success on the teeth, was associated with only modest caries induction. Failure of the gtfG(-) mutant to persistently colonize was associated with slight diminution of caries scores by comparison with its gtfG(+) WT.

CONCLUSIONS

Initial S. gordonii colonization does not depend on Gtf-G synthesis; rather, Gtf-G production determines S. gordonii's ability to persist on the teeth of sucrose-fed rats. S. gordonii appears weakly cariogenic by comparison with S. mutans reference strains.

Salivary biomarkers associated with alveolar bone loss

A longitudinal case-control study was performed to measure the association of salivary biomarkers with alveolar bone loss from a sub-sample of 1,256 post-menopausal women enrolled in the Buffalo Women's Health Initiative. From this cohort, 40 subjects with significant alveolar bone loss over a 5-year period were compared to 40 age-matched control subjects having no alveolar bone loss. Several biomarkers were quantitated in saliva collected at baseline by immunoassay. A positive association was noted between alveolar bone loss and salivary concentrations of hepatocyte growth factor, and interleukin-1 beta, while a negative association was noted for alveolar bone loss and salivary osteonectin. This study provides preliminary evidence that several salivary biomarkers measured at baseline may serve to predict future alveolar bone loss.

Amylase-binding proteins A (AbpA) and B (AbpB) differentially affect colonization of rats' teeth by Streptococcus gordonii

Streptococcus gordonii produces two alpha-amylase-binding proteins, AbpA and AbpB, that have been extensively studied in vitro. Little is known, however, about their significance in oral colonization and cariogenicity (virulence). To clarify these issues, weanling specific pathogen-free Osborne-Mendel rats, TAN : SPFOM(OM)BR, were inoculated either with wild-type strains FAS4-S or Challis-S or with strains having isogenic mutations of abpA, abpB, or both, to compare their colonization abilities and persistence on the teeth. Experiments were done with rats fed a sucrose-rich diet containing low amounts of starch or containing only starch. The mutants and wild-types were quantified in vivo and carious lesions were scored. In 11 experiments, S. gordonii was a prolific colonizer of the teeth when rats were fed the sucrose (with low starch)-supplemented diet, often dominating the flora. Sucrose-fed rats had several-fold higher recoveries of inoculants than those eating the sucrose-free, starch-supplemented diet, regardless of inoculant type. The strain defective in AbpB could not colonize teeth of starch-only-eating rats, but could colonize rats if sucrose was added to the diet. Strains defective in AbpA surprisingly colonized better than their wild-types. A double mutant deficient in both AbpA and AbpB (abpA/abpB) colonized like its wild-type. Wild-types FAS4-S and Challis-S had no more than marginal cariogenicity. Notably, in the absence of AbpA, cariogenicity was slightly augmented. Both the rescue of colonization by the AbpB- mutant and the augmentation of colonization by AbpA- mutant in the presence of dietary sucrose suggested additional amylase-binding protein interactions relevant to colonization. Glucosyltransferase activity was greater in mutants defective in abpA and modestly increased in the abpB mutant. It was concluded that AbpB is required for colonization of teeth of starch-eating rats and its deletion is partially masked if rats eat a sucrose-starch diet. AbpA appears to inhibit colonization of the plaque biofilm in vivo. This unexpected effect in vivo may be associated with interaction of AbpA with glucosyltransferase or with other colonization factors of these cells. These data illustrate that the complex nature of the oral environment may not be adequately modelled by in vitro systems.

Oral bacteria and respiratory infection: effects on respiratory pathogen adhesion and epithelial cell proinflammatory cytokine production

Several microbiologic and epidemiologic studies have suggested an association between dental plaque, poor oral health, and respiratory diseases such as nosocomial pneumonia and chronic obstructive pulmonary disease (COPD). A number of hypotheses are suggested to help explain how oral bacteria may participate in the pathogenesis of respiratory infection. Resident bacteria in oral secretions are likely aspirated along with respiratory pathogens and may affect the adhesion of the later organisms to the respiratory epithelium. Preliminary studies performed in our laboratory suggest that oral bacteria may modulate the adhesion of respiratory pathogens to epithelial cell lines. In addition, oral bacterial products or cytokines in oral/pharyngeal aspirates may stimulate cytokine production from respiratory epithelial cells, resulting in recruitment of inflammatory cells. The resulting inflamed epithelium may be more susceptible to respiratory infection. Further preliminary data are presented that some species of oral bacteria may induce the release of proinflammatory cytokines from epithelial cell lines to an extent similar to that seen for respiratory pathogens.

Role of Streptococcus gordonii amylase-binding protein A in adhesion to hydroxyapatite, starch metabolism, and biofilm formation

Interactions between bacteria and salivary components are thought to be important in the establishment and ecology of the oral microflora. alpha-Amylase, the predominant salivary enzyme in humans, binds to Streptococcus gordonii, a primary colonizer of the tooth. Previous studies have implicated this interaction in adhesion of the bacteria to salivary pellicles, catabolism of dietary starches, and biofilm formation. Amylase binding is mediated at least in part by the amylase-binding protein A (AbpA). To study the function of this protein, an erythromycin resistance determinant [erm(AM)] was inserted within the abpA gene of S. gordonii strains Challis and FAS4 by allelic exchange, resulting in abpA mutant strains Challis-E1 and FAS4-E1. Comparison of the wild-type and mutant strains did not reveal any significant differences in colony morphology, biochemical metabolic profiles, growth in complex or defined media, surface hydrophobicity, or coaggregation properties. Scatchard analysis of adhesion isotherms demonstrated that the wild-type strains adhered better to human parotid-saliva- and amylase-coated hydroxyapatite than did the AbpA mutants. In contrast, the mutant strains bound to whole-saliva-coated hydroxyapatite to a greater extent than did the wild-type strains. While the wild-type strains preincubated with purified salivary amylase grew well in defined medium with potato starch as the sole carbohydrate source, the AbpA mutants did not grow under the same conditions even after preincubation with amylase. In addition, the wild-type strain produced large microcolonies in a flow cell biofilm model, while the abpA mutant strains grew much more poorly and produced relatively small microcolonies. Taken together, these results suggest that AbpA of S. gordonii functions as an adhesin to amylase-coated hydroxyapatite, in salivary-amylase-mediated catabolism of dietary starches and in human saliva-supported biofilm formation by S. gordonii.

RegG, a CcpA homolog, participates in regulation of amylase-binding protein A gene (abpA) expression in Streptococcus gordonii

The amylase-binding protein A (AbpA) of Streptococcus gordonii was found to be undetectable in supernatants of mid-log-phase cultures containing >1% glucose but abundant in supernatants of cultures made with brain heart infusion (BHI), which contains 0.2% glucose. A 10-fold decrease in the level of abpA mRNA in S. gordonii cells cultured in BHI was noted after the addition of glucose to 1%. Analysis of the abpA sequence revealed a potential catabolite responsive element CRE 153 bp downstream of the putative translational start site. A catabolite control protein A gene (ccpA) homolog from S. gordonii, designated regG, was cloned. A regG mutant strain demonstrated moderately less repression of abpA transcription in the presence of 1% glucose. Diauxic growth with glucose and lactose was not affected in the RegG mutant compared to the wild-type parental strain. These results suggest that while RegG plays a role in abpA expression, other mechanisms of catabolite repression are present.

Oral colonization and cariogenicity of Streptococcus gordonii in specific pathogen-free TAN:SPFOM(OM)BR rats consuming starch or sucrose diets

The significance of Streptococcus gordonii in dental caries is undefined, as is that of other alpha-amylase-binding bacteria (ABB) commonly found in the mouth. To clarify the ecological and cariological roles of S. gordonii our specific pathogen-free Osborne-Mendel rats, TAN:SPFOM(OM)BR, were fed either diet 2000 (containing 56% confectioner's sugar, most of which is sucrose) or diet 2000CS (containing 56% cornstarch, in lieu of confectioner's sugar) and inoculated with S. gordonii strains. Uninoculated rats were free of both indigenous mutans streptococci (MS) and ABB, including S. gordonii, as shown by culture on mitis salivarius and blood agars of swabs and sonicates of dentitions after weanlings had consumed these diets for 26 days. ABB were detected by radiochemical assay using [125I]-amylase reactive to alpha-amylase-binding protein characteristic of the surface of S. gordonii and other ABB. No ABB were detected (detection limit < 1 colony-forming units in 10(6) colony-forming units). Thus the TAN:SPFOM(OM)BR colony presents a 'clean animal model' for subsequent study. Consequently, S. gordonii strains Challis or G9B were used to inoculate weanling rat groups consuming either the high-sucrose diet 2000 or the cornstarch diet 2000CS. Two additional groups fed each of these diets remained unioculated. Recoveries of inoculants were tested 12 and 26 days later by oral swabs and sonication of the molars of one hemimandible of each animal, respectively. Uninoculated animals were reconfirmed to be free of ABB and mutans streptococci, but inoculated ones eating diet 2000CS had S. gordonii recoveries of 1-10% or, if eating diet 2000, 10-30% of total colony-farming units in sonicates. There were no statistically significant differences among the inoculated and uninoculated animal groups' caries scores when they ate the cornstarch diet. Lesion scores for sucrose-eating rats were, however, from 2.4-5.1-fold higher than for cornstarch-eating rats, P < 0.001, and were still higher if animals had been inoculated with either Challis (1.41-fold) or G9B (1.64-fold), than if uninoculated, both P < 0.001, so long as the rats ate the sucrose diet. Therefore, TAN:SPFOM(OM)BR rats do not harbour ABB or S. gordonii but can be colonized by S. gordonii. Colonization levels of S. gordonii on the teeth are higher in the presence of high sucrose than with high starch-containing diets. Caries scores are augmented by sucrose compared with starch, and are further augmented by S gordonii colonization. S. gordonii is thus cariologically significant in the presence of sucrose, at least in this rat.

Potential associations between chronic respiratory disease and periodontal disease: analysis of National Health and Nutrition Examination Survey III

BACKGROUND

Associations between poor oral health and chronic lung disease have recently been reported. The present study evaluated these potential associations by analyzing data from the National Health and Nutrition Examination Survey III (NHANES III), which documents the general health and nutritional status of randomly selected United States subjects from 1988 to 1994.

METHODS

This cross-sectional, retrospective study of the NHANES III database included a study population of 13,792 subjects > or = 20 years of age with at least 6 natural teeth. A history of bronchitis and/or emphysema was recorded from the medical questionnaire, and a dichotomized variable combined those with either chronic bronchitis and/or emphysema, together considered as chronic obstructive pulmonary disease (COPD). Subject lung function was estimated by calculating the ratio of forced expiratory volume (FEV) after 1 second (FEV1)/forced vital capacity (FVC). Oral health status was assessed from the DMFS/T index (summary of cumulative caries experience), gingival bleeding, gingival recession, gingival probing depth, and periodontal attachment level. Unweighted analyses were used for initial examination of the data, and a weighted analysis was performed in a final logistic regression model adjusting for age, gender, race and ethnicity, education, income, frequency of dental visits, diabetes mellitus, smoking, and alcohol use.

RESULTS

The mean age of all subjects was 44.4 +/- 17.8 years (mean +/- SD): COPD = 51.2 +/- 17.9 years and subjects without COPD = 43.9 +/- 17.7 years. Subjects with a history of COPD had more periodontal attachment loss than subjects without COPD (1.48 +/- 1.35 mm versus 1.17 +/- 1.09 mm, P = 0.0001). Subjects with mean attachment loss (MAL) > or = 3.0 mm had a higher risk of COPD than those having MAL < 3.0 mm (odds ratio, 1.45; 95% CI, 1.02 to 2.05). A trend was noted in that lung function appeared to diminish with increasing periodontal attachment loss.

CONCLUSIONS

The findings of the present analysis support recently published reports that suggest an association between periodontal disease and COPD.

The risk of nosocomial pneumonia is not increased during partial liquid ventilation

OBJECTIVE

To determine whether partial liquid ventilation (PLV) affects the risk of nosocomial pneumonia.

STUDY DESIGN

To assess in vitro bacterial adhesion and viability after liquid perfluorocarbon exposure and to assess bacterial recovery after partial liquid ventilation in vivo in rabbits.

SETTING

University animal research facility.

SUBJECTS

Thirty-six New Zealand White rabbits.

INTERVENTIONS

To assess adhesions, radiolabeled Escherichia coli were exposed to perfluorocarbon, incubated against artificial biosurfaces, and compared with nonexposed controls. Bacterial viability in vitro was assessed by exposing broth suspensions of Pasteurella multocida to perflubron for various times. Controls were run in parallel without exposure. Quantitative cultures were performed to determine viability. We undertook short-term and recovery in vivo investigations. The lungs of treated animals were filled with perflubron (approximately 18 mL/kg), and the control rabbits were ventilated without perflubron in an identical fashion. Cryopreserved aliquots of P. multocida were administered via an endotracheal tube. The short-term study animals were ventilated for 6 hrs before being killed. The recovery animals were ventilated for 2-4 hrs, extubated, and killed 20 hrs later. The lungs were removed, aseptically minced, and homogenized. Serial dilutions of the homogenate were quantitatively cultured by manual counting of colonies on agar plates. The recovered organisms were typed for species by the clinical microbiology laboratory.

MEASUREMENTS AND MAIN RESULTS

The adhesion of bacteria to immobilized bronchoalveolar lavage and human saliva, respectively, was reduced by 65%+/-7% and 66%+/-1% (p < .05; n = 5) after exposure to perflubron and by 63%+/-9% and 68%+/-6% after exposure to FC-77 (p < .05; n = 5); however, adhesion was not affected by exposure to Rimar. There was no difference in bacterial viability between the control and perflubron-exposed bacteria (n = 5). The in vivo study demonstrated a ten-fold or greater reduction in the number of recovered bacteria in the partial liquid ventilated group compared with the control group.

CONCLUSIONS

This study suggests that different perfluorocarbons affect adhesions differently. Perflubron and FC-77 appear to decrease bacterial adhesion, whereas Rimar does not. Rerflubron does not have a direct bactericidal effect. Furthermore, PLV with perflubron decreased the number of viable bacteria per gram of tissue after an intentional inoculation of the airway, suggesting that the risk of nosocomial pneumonia is unlikely to be increased during PLV and may, in fact, be reduced in patients supported with PLV.

Prevalence of the amylase-binding protein A gene (abpA) in oral streptococci

Salivary amylase binds specifically to a number of oral streptococcal species. This interaction may play an important role in dental plaque formation. Recently, a 585-bp gene was cloned and sequenced from Streptococcus gordonii Challis encoding a 20.5-kDa amylase-binding protein (AbpA). The goal of this study was to determine if related genes are present in other species of oral streptococci. Biotinylated abpA was used in Southern blot analysis to screen genomic DNA from several strains representing eight species of oral streptococci. This probe hybridized with a 4.0-kb HindIII restriction fragment from all 13 strains of S. gordonii tested. The probe did not appear to bind to any restriction fragments from other species of amylase-binding oral streptococci including Streptococcus mitis (with the exception of 1 of 14 strains), Streptococcus crista (3 strains), Streptococcus anginosus (1 strain), and Streptococcus parasanguinis (1 strain), or to non-amylase-binding oral streptococci including Streptococcus sanguinis (3 strains), Streptococcus oralis (4 strains), and Streptococcus mutans (1 strain). Primers homologous to sequences within the 3' and 5' ends of abpA yielded products of 400 bp following PCR of genomic DNA from the Southern blot-positive strains. Several of these PCR products were cloned and sequenced. The levels of similarity of these cloned products to the abpA of S. gordonii Challis ranged from 91 to 96%. These studies reveal that the abpA gene appears to be specific to S. gordonii and differs from genes encoding amylase-binding proteins from other species of amylase-binding streptococci.

Association of periodontal infections with atherosclerotic and pulmonary diseases

Chronic infections may influence the severity and/or course of a number of systemic diseases. Periodontal diseases are localized chronic inflammatory conditions of the gingiva and underlying bone and connective tissues induced by bacteria and bacterial products of dental plaque. This paper will discuss the evidence for the role of periodontal disease in the pathogenesis of 2 important systemic diseases, atherosclerosis and pulmonary infections. Both epidemiological and laboratory studies are reviewed to assess the biological basis for the association of periodontal infections and these important diseases. Several potential mechanisms by which periodontal diseases may influence these conditions are also discussed.

Role of oral bacteria in respiratory infection

An association between oral conditions such as periodontal disease and several respiratory conditions has been noted. For example, recent evidence has suggested a central role for the oral cavity in the process of respiratory infection. Oral periodontopathic bacteria can be aspirated into the lung to cause aspiration pneumonia. The teeth may also serve as a reservoir for respiratory pathogen colonization and subsequent nosocomial pneumonia. Typical respiratory pathogens have been shown to colonize the dental plaque of hospitalized intensive care and nursing home patients. Once established in the mouth, these pathogens may be aspirated into the lung to cause infection. Other epidemiologic studies have noted a relationship between poor oral hygiene or periodontal bone loss and chronic obstructive pulmonary disease. Several mechanisms are proposed to explain the potential role of oral bacteria in the pathogenesis of respiratory infection: 1. aspiration of oral pathogens (such as Porphyromonas gingivalis, Actinobacillus actinomycetemcomitans, etc.) into the lung to cause infection; 2. periodontal disease-associated enzymes in saliva may modify mucosal surfaces to promote adhesion and colonization by respiratory pathogens, which are then aspirated into the lung; 3. periodontal disease-associated enzymes may destroy salivary pellicles on pathogenic bacteria to hinder their clearance from the mucosal surface; and 4. cytokines originating from periodontal tissues may alter respiratory epithelium to promote infection by respiratory pathogens.

Identification and molecular analysis of rough-colony-specific outer membrane proteins of Actinobacillus actinomycetemcomitans

Actinobacillus actinomycetemcomitans, a gram-negative bacterium isolated from the human mouth, has been implicated in the pathogenesis of early-onset periodontitis. Primary isolates cultured from subgingival plaque exhibit an adherent, rough colony phenotype which spontaneously converts to a nonadherent, smooth phenotype upon in vitro subculture. The rough colony variant produces abundant fimbriae and autoaggregates, while the smooth colony variant is planktonic and produces scant fimbriae. To begin to understand the significance of colony variation in biofilm formation by A. actinomycetemcomitans, outer membrane protein profiles of four isogenic rough and smooth colony variants were compared by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Two proteins with relative molecular masses of 43 and 20 kDa were expressed by the rough colony variants exclusively. Expression of these proteins was not found to be dependent on growth phase, oxygen tension, or type of complex medium. N-terminal amino acid sequences of these proteins obtained by Edman degradation were compared with sequences from the University of Oklahoma A. actinomycetemcomitans genome database. Two contiguous open reading frames (ORFs) encoding proteins having sequence homology with these proteins were identified. The 43-kDa protein (RcpA [rough colony protein A]) was similar to precursor protein D of the general secretion pathway of gram-negative bacilli, while the 20-kDa protein (RcpB [rough colony protein B]) appeared to be unique. The genes encoding these proteins have been cloned from A. actinomycetemcomitans 283 and sequenced. A BLASTX (gapped BLAST) search of the surrounding ORFs revealed homology with other fimbria-related proteins. These data suggest that the genes encoding the 43-kDa (rcpA) and 20-kDa (rcpB) proteins may be functionally related to each other and to genes that may encode fimbria-associated proteins.

Respiratory pathogen colonization of the dental plaque of institutionalized elders

Although it has been established that aspiration of pharyngeal bacteria is the major route of infection in the development of nosocomial pneumonia, colonization of the pharyngeal mucosa by respiratory pathogens has been shown to be a transient phenomenon. It has been suggested that the dental plaque may constitute an additional, possibly more stable, reservoir of respiratory pathogens. The purpose of this study was to assess the prevalence of oral colonization by potential respiratory pathogens in a group of elderly (mean age = 75.9 yrs) chronic-care-facility residents (n = 28) and a group of age-, gender-, and race-matched outpatient control subjects (n = 30), with specific attention to plaque present on tooth, denture, and oral mucosal surfaces. Plaque scores on teeth and dentures were significantly higher in the chronic-care-facility (CCF) subjects than in the dental outpatient control (DOC) subjects (PII 2.3 vs. 1.2 and denture plaque 1.4 vs. 0.3). While no subjects in the DOC group were found to be colonized with respiratory pathogens (> 1.0% of the cultivable aerobic flora), 14.3% (4/28) of the CCF subjects were found to be colonized. Oral colonization with respiratory pathogens in CCF subjects was associated with the presence of chronic obstructive pulmonary disease (COPD) and higher plaque scores. These results suggest that deficient dental plaque control and the presence of COPD may be related to respiratory pathogen colonization of dental plaque in chronic-care-facility residents.

Associations between oral conditions and respiratory disease in a national sample survey population

Respiratory infectious diseases such as bacterial pneumonia and bronchitis are common and costly, especially in institutionalized and elderly inpatients. Respiratory infection is thought to rely in part on the aspiration of oropharyngeal flora into the lower respiratory tract and failure of host defense mechanisms to eliminate the contaminating bacteria, which then multiply to cause infection. It has been suggested that dental plaque may act as a reservoir of respiratory pathogens, especially in patients with periodontal disease. However, the impact of poor oral health on oral respiratory pathogen colonization and lung infection is uncertain, especially in ambulatory, non-institutionalized populations. To begin to assess potential associations between respiratory diseases and oral health, data from the National Health and Nutrition Examination Survey I (NHANES I) were analyzed. This database contains information on the general health status of 23,808 individual Of these, 386 individuals reported a suspected respiratory condition that was further assessed by a physician. These subjects were categorized as having a confirmed chronic respiratory disease (chronic bronchitis or emphysema) or an acute respiratory disease (influenza, pneumonia, acute bronchitis). They were compared to those not having a respiratory disease. Initial non-parametric analysis noted that individuals with a confirmed chronic respiratory disease (n = 41) had significantly greater oral hygiene index scores than subjects without respiratory disease (n = 193; P = 0.0441). Logistic regression analysis of data from these subjects, which considered age, race, gender, smoking status, and simplified oral hygiene index (OHI), suggested that subjects having the median OHI value were 1.3 times more likely to have a chronic respiratory disease relative to those with and OHI of O. Similarly, subjects with the maximum OHI value were 4.5 times more likely to have a chronic respiratory disease than those with an OHI of O. No evidence was found to support an association between the periodontal index and any respiratory disease. These results suggest OHI to have a residual effect on chronic respiratory disease of both practical and statistical significance.

Position paper of The American Academy of Periodontology: periodontal disease as a potential risk factor for systemic diseases

This paper on periodontal disease as a potential risk factor for systemic diseases was prepared by the Research, Science and Therapy Committee of The American Academy of Periodontology. It is intended to provide information regarding the role of periodontal disease in systemic diseases, including bacteremia, infective endocarditis, cardiovascular disease and atherosclerosis, prosthetic device infection, diabetes mellitus, respiratory diseases, and adverse pregnancy outcomes.

The microbial ecology and immunology of the adenoid: implications for otitis media

The nasopharyngeal tonsil, or adenoid, is a major inductive site for the synthesis of J-chain-positive B cells that may migrate to other areas of the upper respiratory tract, such as the nasal mucosa, the parotid gland, the lacrimal gland, and the middle ear during inflammation. The production of secretory IgA by both the nasopharyngeal tonsil and the nasal mucosa plays a major role in local immune protection against bacteria and viruses. The release of cytokines from Th1 and Th2 lymphocytes must be appropriate for B cells to produce IgA. The factors or mechanisms responsible for this are not, at present, known, but it appears that there is a difference in the profiles of cytokine secretion by Th1 and Th2 lymphocytes in the adenoids in both otitis-prone, as well as nonotitis-prone children. We have suggested that if this specific immune system does not protect the host from invasion by potential pathogens, there are other modalities of therapy to protect the nasopharynx from colonization with pathogenic bacteria or viruses. These include the production of specific antibodies against bacterial surface proteins that have been identified as mucin-binding proteins. Alteration of the microbial flora with commensal organisms such as viridans streptococci can be utilized. These alpha-hemolytic streptococci probably function by producing an acid environment that prevents colonization of organisms such as nontypeable H. influenzae. Finally, the induction of specific SIgA by conserved outer membrane protein antigens of potential pathogens may be another strategy in the prevention of colonization of potential bacterial pathogens in the nasopharynx.

Relationships between periodontal disease and bacterial pneumonia

Bacterial pneumonia is a prevalent and costly infection that is a significant cause of morbidity and mortality in patients of all ages. The continuing emergence of antibiotic-resistant bacteria (e.g., penicillin-resistant pneumococci) suggests that bacterial pneumonia will assume increasing importance in the coming years. Thus, knowledge of the pathogenesis of, and risk factors for, bacterial pneumonia is critical to the development of strategies for prevention and treatment of these infections. Bacterial pneumonia in adults is the result of aspiration of oropharyngeal flora into the lower respiratory tract and failure of host defense mechanisms to eliminate the contaminating bacteria, which multiply in the lung and cause infection. It is recognized that community-acquired pneumonia and lung abscesses can be the result of infection by anaerobic bacteria; dental plaque would seem to be a logical source of these bacteria, especially in patients with periodontal disease. It is also possible that patients with high risk for pneumonia, such as hospitalized patients and nursing home residents, are likely to pay less attention to personal hygiene than healthy patients. One important dimension of this personal neglect may be diminished attention to oral hygiene. Poor oral hygiene and periodontal disease may promote oropharyngeal colonization by potential respiratory pathogens (PRPs) including Enterobacteriaceae (Klebsiella pneumoniae, Escherichia coli, Enterobacter species, etc.), Pseudomonas aeruginosa, and Staphylococcus aureus. This paper provides the rationale for the development of this hypothesis especially as it pertains to mechanically ventilated intensive care unit patients and nursing home residents, two patient groups with a high risk for bacterial pneumonia.

Role of type 1 fimbriae in the adhesion of Escherichia coli to salivary mucin and secretory immunoglobulin A

Saliva is known to modulate the adhesion of bacteria in the oral cavity. The present work was performed to assess the effect of salivary components on the adhesion of Escherichia coli to a model oral surface. Several genetically engineered E. coli strains were used to examine the role of type 1 fimbriation in the interaction of these strains with salivary components in solution or adsorbed to hydroxyapatite. High (MG1) and low (MG2) molecular weight salivary mucins, and secretory immunoglobulin A (sIgA), were found to interact with the surface of E. coli, and these interactions were independent of the expression of fimbriae or capsule. In contrast, fimbriated strains of E. coli adhered to a greater extent to saliva-coated synthetic hydroxyapatite (HAP) than did nonfimbriated strains. Testing of salivary components separated by gel filtration chromatography revealed that only high-molecular-weight components promoted adhesion of E. coli to HAP. Additional studies found that purified MG2 and sIgA promoted the adhesion of E. coli to HAP. Expression of type 1 fimbriae enhanced adhesion, while mannose inhibited adhesion of fimbriated strains, to saliva-coated HAP and to HAP coated with MG2 and sIgA. We conclude that salivary MG2 and sIgA may provide receptors for the adhesion of type 1 fimbriated E. coli to oral surfaces.

Experimental salivary pellicles formed on titanium surfaces mediate adhesion of streptococci

The goal of this study was to characterize salivary components of titanium pellicles and to determine how experimental pellicles affect adhesion of several strains of streptococci to titanium surfaces. Titanium experimental pellicles were formed by incubation of fresh human parotid or human submandibular-sublingual saliva on pure titanium beads. Pellicle was recovered from the beads using sodium dodecyl sulfate buffer and was subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting to identify adsorbed salivary components. Streptococcus anginosus, S. oralis, and S. salivarius recovered from in vivo titanium plaque and five reference strains of streptococci were used in adhesion assays to titanium beads with and without experimental salivary pellicles. The experimental pellicle formed on titanium was found to be composed of selected proteins from human parotid and human submandibular-sublingual saliva. Salivary alpha-amylase and proline-rich proteins were found in all experimental pellicles, while sIgA, high-molecular weight mucin, and proline-rich glycoproteins were detected in one of the experimental pellicles examined. Adhesion of fresh isolates and reference stains of S. anginosus, S. oralis, and S. salivarius to saliva-coated titanium was reduced compared to that of titanium without saliva coating. However, adhesion of laboratory strains of S. gordonii and S. sanguis was found to be significantly greater to experimental pellicles of human submandibular-sublingual saliva than was the adhesion of the fresh isolates, suggesting that streptococci-colonizing implant surfaces may be inherently less adhesive than other bacterial strains. This study found that salivary pellicles are selectively formed on titanium and mediate in vitro adhesion of streptococci.

Salivary amylase promotes adhesion of oral streptococci to hydroxyapatite

Recent studies have demonstrated that several species of oral streptococci, such as Streptococcus gordonii, bind soluble salivary alpha-amylase. The goal of the present study was to determine if amylase immobilized onto a surface such as hydroxyapatite can serve as an adhesion receptor for S. gordonii. Initially, human parotid saliva was fractionated on Bio-Gel P60, and fractions were screened for their ability to promote adhesion of S. gordonii to hydroxyapatite. Fractions containing alpha-amylase and proline-rich proteins promoted the adhesion of [3H]-labeled S. gordonii to hydroxyapatite. Similar findings were obtained with purified amylase and acidic proline-rich protein 1 (PRP1). Incubation of S. gordonii G9B in the presence of starch and maltotriose increased the binding of this strain to amylase-coated hydroxyapatite, while the adhesion of S. sanguis 10556 to amylase-coated hydroxyapatite was not affected by these saccharides. These results suggest that amylase may serve as a hydroxyapatite pellicle receptor for amylase-binding streptococci. Furthermore, starch and starch metabolites may enhance the adhesion of amylase-binding streptococci to amylase in dental pellicles to augment the formation of dental plaque.

Emergence in human dental plaque and host distribution of amylase-binding streptococci

Salivary amylase is known to bind specifically to several species of oral streptococci. To assess the importance of this interaction in bacterial colonization of the oral cavity, we determined the proportion and identity of amylase-binding bacteria (ABB) in dental plaque of humans and various salivary amylase-secreting and non-secreting mammalian species. The numbers of ABB in undisturbed plaque collected over time from tooth surfaces of six human volunteers or from 14 other mammalian species were determined by means of a replicating assay. The mean proportion of ABB cultured aerobically from human teeth at 2 h was 10.5% (SD 10), at 8 h 7.9% (8), at 24 h 13% (11), and at 48 h 12% (9). The mean proportion of anaerobically cultured ABB found at 2 h was 3% (SD 4), at 8 h 5% (5), at 24 h 12% (9), and at 48 h 16% (12). Amylase-binding bacteria cultured from these samples resembled Streptococcus mitis, Streptococcus gordonii, Streptococcus salivarius, Streptococcus crista, or unidentified streptococci. In addition, only animals exhibiting salivary amylase activity in their saliva harbored ABB (ranging from 2 to 31% of the total flora), with the exception of the pig, where no ABB were found to colonize, despite considerable amylase activity in saliva. Only strains resembling S. mitis and S. salivarius and unspeciated strains were isolated from these mammals. These results suggest that amylase-binding streptococci are the predominant ABB in human plaque, and their numbers generally increase as plaque develops. Since ABB colonized only the oral cavities of hosts demonstrating salivary amylase activity, the ability to bind amylase may play an important role in oral colonization by these bacteria.

Saliva-bacterium interactions in oral microbial ecology

Saliva is thought to have a significant impact on the colonization of microorganisms in the oral cavity. Salivary components may participate in this process by one of four general mechanisms: binding to microorganisms to facilitate their clearance from the oral cavity, serving as receptors in oral pellicles for microbial adhesion to host surfaces, inhibiting microbial growth or mediating microbial killing, and serving as microbial nutritional substrates. This article reviews information pertinent to the molecular interaction of salivary components with bacteria (primarily the oral streptococci and Actinomyces) and explores the implications of these interactions for oral bacterial colonization and dental plaque formation. Knowledge of the molecular mechanisms controlling bacterial colonization of the oral cavity may suggest methods to prevent not only dental plaque formation but also serious medical infections that may follow microbial colonization of the oral cavity.

Human submandibular-sublingual saliva promotes adhesion of Candida albicans to polymethylmethacrylate

The purpose of this study was to identify components of saliva that interact with Candida albicans in solution and that may modulate adhesion to dental acrylic (polymethylmethacrylate [PMMA]) surfaces. Saliva-derived pellicles extracted from C. albicans blastoconidia and hyphal-form cells mixed with fresh human submandibular-sublingual saliva (HSMSL) contained predominantly high- and low-molecular-weight mucins (MG1 and MG2, respectively). In contrast, few components from fresh human parotid saliva were adsorbed to yeast cells. Coating PMMA beads with HSMSL significantly enhanced (10-fold) adhesion of both growth forms of C. albicans compared with human parotid saliva (2-fold), suggesting a role for mucins in adhesion. HSMSL-enhanced adhesion was completely abolished by preadsorbing HSMSL with either blastoconidia or hyphal-form cells prior to coating PMMA. However, coating PMMA with purified salivary mucins or the addition of mucin to preadsorbed saliva did not enhance or restore adhesion to levels found with fresh HSMSL. Adhesion assays employing guanidine-treated fresh HSMSL showed a complete lack of Candida binding, suggesting that subjecting HSMSL to dissociating conditions may alter a property of salivary mucins crucial for C. albicans adhesion. Protease and glycosidase treatment of yeast cells significantly reduced adhesion to HSMSL-coated PMMA. In addition, preincubation of C. albicans with mannose and galactose inhibited adhesion to HSMSL-coated PMMA. These results suggest that mucins may play a role in C. albicans adhesion to saliva-coated PMMA and that a glycoprotein on the yeast surface may be involved in these events.

Salivary alpha-amylase: role in dental plaque and caries formation

Salivary alpha-amylase, one of the most plentiful components in human saliva, has at least three distinct biological functions. The enzymatic activity of alpha-amylase undoubtedly plays a role in carbohydrate digestion. Amylase in solution binds with high affinity to a selected group of oral streptococci, a function that may contribute to bacterial clearance and nutrition. The fact that alpha-amylase is also found in acquired enamel pellicle suggests a role in the adhesion of alpha-amylase-binding bacteria. All of these biological activities seem to depend on an intact enzyme conformation. Binding of alpha-amylase to bacteria and teeth may have important implications for dental plaque and caries formation. alpha-Amylase bound to bacteria in plaque may facilitate dietary starch hydrolysis to provide additional glucose for metabolism by plaque microorganisms in close proximity to the tooth surface. The resulting lactic acid produced may be added to the pool of acid in plaque to contribute to tooth demineralization.

Characterization of an amylase-binding component of Streptococcus gordonii G9B

The goal of the present study was to begin characterizing the amylase-binding component(s) on the surface of Streptococcus gordonii G9B. Alkali extracts but not phenol-water extracts of this bacterium inhibited 125I-amylase binding to S. gordonii G9B. To identify the bacterial components involved in amylase binding, the alkali extract was subjected to affinity chromatography on amylase-Sepharose. Immunoblotting with a rabbit antiserum against S. gordonii G9B revealed that a 20-kDa streptococcal component was eluted from the amylase-Sepharose with 1% sodium dodecyl sulfate (SDS), 2 M KSCN, or 0.1 M sodium citrate buffer, pH 4.5. Subsequently, the 20-kDa component was prepared from alkali extracts by electroelution from preparative SDS electrophoresis or by gel filtration chromatography. This component was trypsin sensitive, and an antibody raised against it inhibited the binding of 125I-amylase to S. gordonii G9B. Indirect immunofluorescence microscopy and immunogold electron microscopy demonstrated that both bound amylase and the 20-kDa component were localized to the cell division septum on dividing cells or to polar zones on single cells. In addition, exponentially growing bacteria bound more 125I-amylase than stationary-phase cells did. Collectively, these results suggest that a 20-kDa amylase-binding component is present on the surface of the nascent streptococcal cell wall.

Formation of salivary-mucosal pellicle: the role of transglutaminase

The present investigation was carried out to identify salivary components of mucosal pellicles in vivo and explore further the mechanism of interaction between salivary molecules and buccal epithelial cells. By using specific antisera and immunoprotein blotting, high-(MG1) and low-(MG2) molecular-mass salivary mucins, amylase, salivary cystatins and proline-rich proteins were detected within mucosal pellicle in vivo. In addition, the data indicated that the mucins and proline-rich proteins could be cleaved into lower-molecular-mass products, whereas the proline-rich proteins could also be cross-linked into higher-molecular-mass complexes. The role of buccal epithelial cell transglutaminase in these interactions was further studied by utilizing purified iodinated amylase, neutral cystatin SN and acidic proline-rich proteins 1 and 3 (APRP1 and 3). After incubation with buccal epithelial cells in vitro 125I-labelled APRPs appeared to undergo a greater degree of cross-linking than 125I-labelled cystatin SN, as determined by SDS/PAGE/autoradiography. Amylase did not appear to be cross-linked at all. Recovery of 125I-labelled APRPs and 125I-labelled cystatin SN with epithelial cell envelopes after repeated extraction suggested that both molecules were cross-linked to envelope proteins, but that 125I-labelled APRPs were cross-linked to a greater degree than 125I-labelled cystatin SN. Cross-linking in buccal epithelial cell preparations was inhibited by an excess of methylamine hydrochloride, a transglutaminase substrate. In a further assessment of amylase, cystatin and APRPs as transglutaminase substrates, only APRP3 and a partially purified preparation of APRPs acted as an amine acceptor for the cross-linking of [14C]methylamine by purified transglutaminase, as determined by SDS/PAGE/fluorography. This reaction was completely inhibited by excess EDTA. The combined data from this study suggest that during mucosal pellicle formation multiple components of saliva adsorb to buccal epithelial cell surfaces, and that, within this group, selected components are enzymically cross-linked by an epithelial transglutaminase and/or proteolytically cleaved into smaller fragments.

Colonization of dental plaque by respiratory pathogens in medical intensive care patients

OBJECTIVE

To assess the prevalence of oral colonization by respiratory pathogens in a group of ICU patients, with specific attention to dental plaque and the oral mucosa.

DESIGN

Prospective, nonrandomized study with age-matched controls.

SETTINGS

Medical ICU in a tertiary-care Veterans Affairs Medical Center and a dental school outpatient preventive dentistry clinic.

PATIENTS

Nonconsecutive, unselected patients admitted to the medical ICU during a 2-month period; controls were age-matched patients seen for the first time in the preventive dentistry clinic.

INTERVENTIONS

None.

MEASUREMENTS

Oral hygienic status was assessed in both groups using a semiquantitative system. Quantitative cultures of dental plaque and buccal mucosa were done within 12 hrs of medical ICU admission and every third day thereafter until discharge/death from the medical ICU. In controls, cultures of plaque and buccal mucosa were done on the initial visit only. Severity of illness of medical ICU patients was quantitated using the Acute Physiology and Chronic Health Evaluation (APACHE II) system and McCabe-Jackson criteria.

MAIN RESULTS

Oral hygiene of medical ICU patients was poor. These patients had a mean plaque score (1.9 +/- 0.2) that was significantly greater than that same score seen in outpatients of the preventive dentistry clinic (1.4 +/- 0.1; p less than .005). Plaque and/or oral mucosa of 22 (65%) of 34 medical ICU patients were colonized by respiratory pathogens, in contrast to only four (16%) of 25 preventive dentistry clinic patients (p less than .005). The potential respiratory pathogens cultured from medical ICU patients included methicillin-resistant Staphylococcus aureus, Pseudomonas aeruginosa, and ten genera of Gram-negative bacilli. Colonization by respiratory pathogens was statistically associated with concomitant antibiotic therapy within the medical ICU group of patients, but not with severity of illness. Although medical ICU patients tended to have more dental plaque than preventive dentistry clinic patients, there was no statistically significant association noted between the presence of dental plaque and respiratory pathogen colonization.

CONCLUSIONS

These findings suggest that bacteria commonly causing nosocomial pneumonia colonize the dental plaque and oral mucosa of intensive care patients. In many cases, this colonization occurs by large numbers of bacteria. Dental plaque may be an important reservoir of these pathogens in medical ICU patients. Efforts to improve oral hygiene in medical ICU patients could reduce plaque load and possibly reduce oropharyngeal colonization.

Use of a replica-plate assay for the rapid assessment of salivary protein-bacteria interactions

A replica-plate assay was used to screen for the interaction of salivary molecules with dental plaque bacteria. Bacterial colonies cultured from supragingival plaque on sheep-blood (SB) agar were replica-plated onto nitrocellulose membranes overlaying SB or mitis-salivarius agar. Membranes with attached colonies were removed and incubated with 125I-amylase or 125I-proline-rich glycoprotein (PRG). Positive interactions were detected by autoradiography. Only strains of Streptococcus gordonii and Actinomyces viscosus bound amylase, and strains of A. viscosus bound PRG. The results suggest that amylase and PRG bind to selected species of aerobic dental plaque bacteria.

Crystallization and preliminary X-ray diffraction studies of human salivary alpha-amylase

Nonglycosylated alpha-amylase, a major component of human parotid saliva, has been crystallized by the vapor diffusion technique using 2-methyl-2,4-pentanediol as the precipitant in the presence of CaCl2 at pH 9.0. The crystals are orthorhombic, space group P2(1)2(1)2(1) with unit cell dimensions of a = 53.3, b = 75.8, and c = 138.1 A. The asymmetric unit contains one amylase molecule. The solvent content is 54%. The crystals are stable to X-rays and diffract up to 2.8 A and appear to be suitable for X-ray diffraction studies.

Structural relationship between the enzymatic and streptococcal binding sites of human salivary alpha-amylase

Previous studies have demonstrated that human salivary alpha-amylase specifically binds to the oral bacterium Streptococcus gordonii. This interaction is inhibited by substrates such as starch and maltotriose suggesting that bacterial binding may involve the enzymatic site of amylase. Experiments were performed to determine if amylase bound to the bacterial surface possessed enzymatic activity. It was found that over one-half of the bound amylase was enzymatically active. In addition, bacterial-bound amylase hydrolyzed starch to glucose which was then metabolized to lactic acid by the bacteria. In further studies, the role of amylase's histidine residues in streptococcal binding and enzymatic function was assessed after their selective modification with diethyl pyrocarbonate. DEP-modified amylase showed a marked reduction in both enzymatic and streptococcal binding activities. These effects were diminished when DEP modification occurred in the presence of maltotriose. DEP-modified amylase had a significantly altered secondary structure when compared with native enzyme or amylase modified in the presence of maltotriose. Collectively, these results suggest that human salivary alpha-amylase may possess multiple sites for bacterial binding and enzymatic activity which share structural similarities.

Characterization of salivary alpha-amylase binding to Streptococcus sanguis

The purpose of this study was to identify the major salivary components which interact with oral bacteria and to determine the mechanism(s) responsible for their binding to the bacterial surface. Strains of Streptococcus sanguis, Streptococcus mitis, Streptococcus mutans, and Actinomyces viscosus were incubated for 2 h in freshly collected human submandibular-sublingual saliva (HSMSL) or parotid saliva (HPS), and bound salivary components were eluted with 2% sodium dodecyl sulfate. By sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western transfer, alpha-amylase (EC 3.2.1.1) was the prominent salivary component eluted from S. sanguis. Studies with 125I-labeled HSMSL or 125I-labeled HPS also demonstrated a component with an electrophoretic mobility identical to that of alpha-amylase which bound to S. sanguis. Purified alpha-amylase from human parotid saliva was radiolabeled and found to bind to strains of S. sanguis genotypes 1 and 3 and S. mitis genotype 2, but not to strains of other species of oral bacteria. Binding of [125I]alpha-amylase to streptococci was saturable, calcium independent, and inhibitable by excess unlabeled alpha-amylases from a variety of sources, but not by secretory immunoglobulin A and the proline-rich glycoprotein from HPS. Reduced and alkylated alpha-amylase lost enzymatic and bacterial binding activities. Binding was inhibited by incubation with maltotriose, maltooligosaccharides, limit dextrins, and starch.

Lubrication of selected salivary molecules and artificial salivas

The lubrication regime displayed by human salivas (parotid and submandibular-sublingual), purified salivary molecules (the mucins MG1 and MG2 and alpha-amylases), and selected artificial salivas (Oracare D, Saliva Substitute, and Orthana) was assessed in vitro using a friction-testing device. Thin-film (boundary) lubrication was observed for all of the salivary samples and two of the artificial salivas examined. Oracare D, a glycerol-based artificial saliva, was the exception since it lubricated by a thick-film (hydrodynamic) regime. On a molar basis, the best lubricants of the purified salivary molecules were MG1 greater than MG2 approximately nonglycosylated alpha-amylases approximately glycosylated alpha-amylases.

Effect of anaerobiosis on the surface ultrastructure and surface proteins of Actinobacillus actinomycetemcomitans (Haemophilus actinomycetemcomitans)

The ultrastructures and surface protein profiles of aerobically cultured Actinobacillus actinomycetemcomitans (Haemophilus actinomycetemcomitans) differed from those of cells cultured anaerobically. Similar ultrastructural differences were also observed when aerobic and anaerobic cultures of a strain of Escherichia coli were compared. These results suggest that oxygen-related variations in the bacterial cell surface may play a role in the adaptation of oral bacteria to different host environments.