Effects of fibronectin and other salivary macromolecules on the adherence of Escherichia coli to buccal epithelial cells

Evaluation of possible biomarkers for caries risk in children 6 to 12 years of age

Background: Electrolytes, proteins, and other salivary molecules play an important role in tooth integrity and can serve as biomarkers associated with caries. Objective: To determine the concentration of potential biomarkers in children without caries (CF) and children with caries (CA). Methods: Unstimulated saliva was collected, and the biomarkers quantified in duplicate, using commercial Enzyme Linked Immunosorbent Assay (ELISA) kits to determine IgA, fibronectin, cathelicidin LL-37, and statherin levels, as well as colorimetric tests to detect formate and phosphate. Results: Significantly higher concentrations of statherin was detected in the CF group (Median: 94,734.6; IQR: 92,934.6-95,113.7) compared to the CA2 group (90,875.0; IQR: 83,580.2-94,633.4) (p = 0.03). Slightly higher median IgA (48,250.0; IQR: 31,461.9-67,418.8) and LL-37 levels (56.1; IQR 43.6-116.2) and a lower concentration of formate were detected in the CF group (0.02; IQR 0.0034-0.15) compared to the group with caries (IgA: 37,776.42; IQR: 33,383.9-44,128.5; LL-37: 46.3; IQR: 40.1011-67.7; formate: 0.10; IQR: 0.01-0.18), but these differences were not statistically significant. Conclusion: The fact that these compounds have been identified as good markers for caries among European adults highlights the difficulty of identifying universal biomarkers that are applicable to all ages or to different populations.

Role of salivary function in patients with globus pharyngeus

BACKGROUND

Our aim was to investigate the prevalence and the clinical role of salivary hypofunction in patients with globus sensation.

METHODS

We conducted a prospective observational study in 340 patients with globus pharyngeus. A standard questionnaire and (99m)Tc-pertechnate salivary scintigraphy were used to evaluate salivary hypofunction, with a full examination from the nasal cavity to the larynx (N = 303). We also investigated the effect of xerostomia management on globus symptoms (N = 252).

RESULTS

The symptom scores for xerostomia were higher in patients with severe globus (p < .05). Objective salivary hypofunction was noted in 57.4% of the patients, based on the reference values from control groups. Globus symptoms were more severe in the subgroup with salivary hypofunction (p = .0447). Conservative management of xerostomia significantly reduced the severity of globus at 1 and 3 months (p = .0002) regardless of salivary function.

CONCLUSIONS

Salivary hypofunction seems to be an aggravating factor in globus pharyngeus, but not a direct cause. Conservative management of xerostomia improves globus symptoms.

Inadequate salivary flow and poor oral mucosal status in intubated intensive care unit patients

OBJECTIVE

To investigate salivary flow and frequency of oral mucositis in intensive care unit patients compared with patients admitted because of elective coronary artery bypass graft (CABG) surgery. In addition, the pattern of oropharyngeal colonization was investigated in these patients.

DESIGN

Prospective study.

SETTING

Mixed intensive care unit and cardiosurgical ward.

PATIENTS

In this study, 24 ventilated intensive care unit patients and 20 CABG patients were included.

MEASUREMENTS AND MAIN RESULTS

Two dental hygienists examined intensive care unit patients for the presence of periodontal disease and mucositis at admission and subsequently every week during their stay in the intensive care unit. At the same time, stimulated salivary flow and salivary total immunoglobulin A output were measured. Oropharyngeal cultures were obtained as well. CABG patients were examined the day before the operation, 1 day, 1 wk, and 2 wks after the operation. The following results were obtained: a) temporarily reduced postoperative stimulated salivary flow and total salivary immunoglobulin A output in CABG patients and nearly absent stimulated salivary flow in intensive care unit patients; b) oropharyngeal colonization with potentially pathogenic microorganisms in intensive care unit and not in CABG patients; and c) the increase in mucositis index in intensive care unit patients paralleled the increase in potentially pathogenic microorganism oropharyngeal colonization, especially and.

CONCLUSIONS

Absence of adequate salivary flow in intubated intensive care unit patients causes severe xerostomia, which may contribute to the development of mucositis and oropharyngeal colonization with Gram-negative bacteria.

Porphyromonas gingivalis fimbrillin is one of the fibronectin-binding proteins

In this study, we demonstrate that Porphyromonas gingivalis fimbrillin, a major component of bacterial fimbriae, is one of the fibronectin-binding proteins and that fibronectin is a potent inhibitor of the adherence of the bacteria to host cells and of the pathogenesis of the bacterium that acts by binding to the fimbriae. A Western blotting (immunoblotting) assay showed that fibronectin binds strongly to P. gingivalis fimbrillin. The fimbrial binding to fibronectin was also evidenced by a binding assay involving 125I-labeled fimbriae. Furthermore, fibronectin markedly inhibited the fimbria-induced expression of interleukin-1beta and neutrophil-specific chemoattractant KC genes in macrophages. The inhibitory action depended on the fimbrial interaction with heparin-binding and cell attachment domains in the fibronectin structure. The binding of P.gingivalis to mouse peritoneal macrophages via its fimbriae was inhibited by fibronectin. Fibronectin also inhibited the bacterial cell-induced expression of interleukin-1beta and KC genes in the macrophages. These results demonstrate the importance of fibronectin as a modulator of the pathogenic mechanism of P. gingivalis, a pathogen that causes adult periodontal disease.

Problems and priorities for controlling opportunistic pathogens with new antimicrobial strategies; an overview of current literature

An International Study Group on New Antimicrobial Strategies (ISGNAS) has been formed in response to the recognition that development of microbial resistance to antibiotics is becoming a serious, world-wide problem. The group met in 1993 for the first time to discuss the feasibility of developing rational alternatives to the use of antibiotics and prepared, as a result, a comprehensive overview of normal (physiological) mechanisms involved in the control of potentially pathogenic (oppotunistic) microorganisms. One objective of ISGNAS is to understand the conditions which allow opportunistic microbes present among the symbionts to cause an infection. There is a need for more coherent information concerning the habitat, growth requirements and host and pathogen properties which allow opportunistic pathogens to cause life-threatening infections. In particular, information is urgently being sought to understand the complexity of the interactions between the vast number of microbial species, and the interactions between the microbes and their host. Another goal is to inspire and enable basic and clinical research that will lead to the development of new therapies for regulating colonization, translocation and infection by opportunistic micro-organisms in patients during periods of decreased resistance. With a sufficient amount of knowledge of how healthy individuals keep opportunistic micro-organisms under control, it may become feasible for physicians to maintain host resistance and inter-microbial factors involved in the containment of opportunistic microbes. Therapies aimed at boostering natural resistance mechanisms will be of critical importance to individuals whose resistance has been compromised as a result of another clinical condition.

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.

The effect of indigenous bacterial populations on buccal epithelial cells on subsequent microbial adhesion in vitro

Despite the numerous investigations on the adhesion of microorganisms to buccal epithelial cells, it is difficult to correlate different results, as disparate adherence values have been reported for a given organism. As one reason for this disparity may be the indigenous or natural bacterial populations on human buccal epithelial cells, the effect of the latter on subsequent microbial adherence in vitro was examined. There was a highly significant correlation between the degree of natural bacterial colonization on pooled buccal epithelial cells from 8 healthy donors and the adhesion of a single isolate each of Streptococcus mitis, Escherichia coli and Actinomyces naeslundii. However, no such relationship could be established for Candida albicans, Streptococcus milleri and another isolate of Streptococcus mitis. As in previous studies, variation in adherence values was found, both between samples from different donors, and from the same donor over time, but to a far lesser degree in pooled samples from different donors. These results imply that natural bacterial populations on buccal epithelial cells may affect the adhesion values derived from laboratory experimentation, and hence such data should be interpreted with caution.

M protein mediates streptococcal adhesion to HEp-2 cells

Streptococcus pyogenes adheres to human epithelial cells in vitro and in vivo. To identify adhesins, cell wall components were extracted from S. pyogenes M6 with alkali or by treatment with mutanolysin and lysozyme. HEp-2 cells were incubated with extracts of S. pyogenes M6 and then analyzed by Western blot (immunoblot) assays, using antibodies to S. pyogenes. Only one streptococcal component (62 kDa) was bound to HEp-2 cells and was identified serologically as M6 protein. Experiments with pepsin-cleaved fragments of M protein indicated that the binding site was located at the N-terminal half of the molecule. M protein was bound selectively to two trypsin-sensitive surface components, 97 and 205 kDa, of HEp-2 cells on nitrocellulose blots of sodium dodecyl sulfate-polyacrylamide gels. Tritium-labeled lipoteichoic acid bound to different HEp-2 cell components, 34 and 35 kDa, in a parallel experiment, indicating that lipoteichoic acid was not complexed with M protein and does not mediate M-protein binding. The four HEp-2 components were unrelated to fibronectin since they did not react with specific antibodies. An M-protein-deficient (M-) strain of streptococcus (JRS75), grown in chemically defined medium, showed 73% less adhesion activity to HEp-2 monolayers than an M+ strain (JRS4). Streptococcal adhesion was insensitive to competitive inhibition by selected monosaccharides. These results indicate that M protein binds directly to certain HEp-2 cell membrane components and mediates streptococcal adhesion.

Three types of binding by Porphyromonas gingivalis and oral bacteria to fibronectin, buccal epithelial cells and erythrocytes

This study showed that the interaction of oral bacteria with fibronectin differed with the type of organism examined. Significant binding of fibronectin was found with Porphyromonas gingivalis non-fimbriated (F-) strain in comparison with the fimbriated strain (F+). However, the F+ strain adhered to buccal epithelial cells in significantly larger numbers than the F- strain. Fibronectin binding and epithelial cell adherence were not associated with haemagglutinating activity. These assays clearly define at least three distinct types of binding by oral bacteria: to fibronectin, buccal epithelial cells and erythrocytes.

Aggregation of group A streptococci by human saliva and effect of saliva on streptococcal adherence to host cells

The aggregation of group A streptococci by whole, stimulated human saliva (WHS) and the effect of saliva on streptococcal adherence to host cells was investigated. WHS samples from 11 individuals were found to aggregate both M+ and M- group A streptococci to various degrees. The aggregating activity was sensitive to heat, EDTA, EGTA [ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid], sodium dodecyl sulfate, and lipoteichoic acid. None of the simple sugars tested, mercaptoethanol, albumin, or nonionic detergents had any effect on aggregation. The aggregating activity of EDTA-treated saliva was restored by 0.1 mM Ca2+ and 1.0 mM Mn2+ but not by up to 5 mM Mg2+. Only streptococci from the stationary phase were aggregated. Hyaluronidase treatment of streptococci from the exponential phase of growth restored their ability to be aggregated, suggesting that the hyaluronic acid capsule interferes with agglutination. Adsorption of WHS by one strain of Streptococcus pyogenes removed aggregating activity for other strains of S. pyogenes and Streptococcus sanguis but not agglutinins for Escherichia coli, suggesting that the agglutinin is specific for certain gram-positive bacteria. Molecular sieve chromatography of WHS and identification of streptococcus-binding components of saliva suggest that either a glycoprotein of approximately 360 kDa or a mucin of saliva of greater than 1,000 kDa mediates aggregation of streptococci. WHS also inhibited adherence of S. pyogenes to buccal epithelial cells.

In vitro effect of chlorhexidine and amikacin on oral gram-negative bacilli from bone marrow transplant recipients

Prophylactic use of chlorhexidine (CHX) mouthrinses has been shown to benefit the oral health status of bone marrow transplant recipients and other immunosuppressed persons and to reduce systemic complications of oral origin. However, a problem that often emerges with these patients is oropharyngeal and lower respiratory tract colonization by opportunistic aerobic or facultative gram-negative bacilli (GNB). Trends in four studies indicated that CHX rinses may predispose these persons to oral colonization by GNB such as the enterobacteria, Klebsiella pneumoniae and Enterobacter cloacae. Since GNB are generally susceptible to broad-spectrum aminoglycoside antibiotics such as amikacin, the in vitro sensitivities of K. pneumoniae, E. cloacae, Pseudomonas aeruginosa, and Escherichia coli ATCC reference strains and K. pneumoniae and E. cloacae oral clinical isolates to combinations of CHX and amikacin were determined by means of a disk diffusion sensitivity assay on Mueller-Hinton agar. The amikacin minimum inhibitory concentrations for all GNB tested were much lower (less than or equal to 4.69 to less than or equal to 9.37 micrograms/ml) than those for CHX (less than or equal to 18.75 to less than or equal to 300 micrograms/ml), and combinations of CHX and amikacin gave larger growth inhibition zones than CHX alone. No antibacterial antagonism between CHX and amikacin was found, and their solubilities were compatible. Therefore use of topical amikacin in conjunction with CHX rinses may reduce oral colonization by GNB in severely immunocompromised patient populations.

Binding of staphylococci to mucus in vivo and in vitro

The association of Staphylococcus aureus, Staphylococcus epidermidis, and Staphylococcus saprophyticus with tissues of the upper respiratory tract were compared by using an in vivo ferret model. Ferrets were challenged intranasally with a 1-ml volume of radiolabeled staphylococci (3 mg [dry weight]), were allowed to clear the bacteria in vivo for 90 min, and were sacrificed. Tissues from the right nasal fossa were harvested and processed for radioassay or histology. Of the recoverable staphylococci, greater than or equal to 96% was associated with mucus gel overlaying mucosa of the turbinates. A quantitative radioassay was developed to study the binding of labeled staphylococci to immobilized crude ferret nasal mucin (FM) and bovine submaxillary gland mucin (BM). Binding showed saturation kinetics and was blocked specifically by BM but not by human Tamm-Horsfall glycoprotein nor orosomucoid. Binding to both FM and BM was significantly inhibited (P less than or equal to 0.01) when cocci were pretreated with trypsin but not when treated with beta-galactosidase or sodium metaperiodate (except for binding of S. saprophyticus to FM). These results suggest that mucin-binding receptors of the cocci may have protein components. The staphylococcus-binding receptors of both FM and BM appear to contain protein components, based on sensitivity to pretreatment with trypsin.

Gingival crevicular fluid fibronectin degradation in periodontal health and disease

The molecular forms of fibronectin (FN) in gingival crevicular fluid of five subjects with at least two sites exhibiting clinical signs of inflammation and pockets of at least 4 mm (test group) and five subjects with clinically healthy periodontium (control group) were investigated. Samples were collected with standard filter paper strips. In the test group samples from both diseased and healthy sites were collected. After collection the test group received one episode of periodontal treatment (scaling and root planning). The sampling and clinical recording were repeated for the diseased sites after about 2 wk. The crevicular fluid FN was analyzed using sodium dodecyl sulphate gel electrophoresis followed by western blotting with polyclonal antibodies against FN. Both intact FN and FN fragments were found in all samples. A larger proportion of FN was in degraded form in the diseased sites than in the healthy or the treated sites. FN was also degraded into smaller peptide fragments in the diseased than in the treated sites. These results suggest that crevicular fluid FN is partially degraded both in periodontal health and disease and that the degree of degradation of FN increases with periodontal inflammation and decreases with periodontal treatment.

Oral gram-negative bacilli in bone marrow transplant patients given chlorhexidine rinses

Fifteen bone marrow transplant (BMT) patients who received three 0.12% chlorhexidine digluconate (CHX) mouthrinses daily for eight weeks were monitored weekly for the occurrence of oral opportunistic Gram-negative bacilli (GNB). Tongue and buccal mucosa were sampled with use of Culturette swabs that were streaked on plates containing selective MacConkey agar. After incubation, colony-forming units were scored and putative GNB classified with use of the API 20E rapid identification system and supplemental biochemical tests. After identification, the susceptibilities of all GNB to CHX were determined by means of a disk diffusion sensitivity assay. Sixty-seven percent (10) of the BMT subjects had at least one GNB-positive tongue culture, and 53% (8) had GNB in samples taken from the buccal mucosa. Of 218 samples taken, 26% and 24% from the tongue and buccal mucosa, respectively, were GNB-positive. The predominant clinical GNB isolates were Enterobacter cloacae (46%) and Klebsiella pneumoniac (30%). Their respective CHX minimum inhibitory concentrations (MICs) were similar to those of ATCC reference strains. Although the CHX MIC values of the clinical GNB isolates were high (less than or equal to 37.5 to less than or equal to 300 micrograms/mL), they were not dependent upon length of exposure to the agent. Therefore, changes in sensitivity or resistance to CHX did not appear to occur. The results suggest that the mouths of BMT patients--and perhaps of other immunosuppressed individuals--should be routinely monitored for GNB, as are other clinically important sites, such as the throat and the urinary and gastro-intestinal tracts.

Localization and characterization of fibronectin-binding to group A streptococci. An electron microscopic study using protein-gold-complexes

The location and nature of the binding sites for fibronectin (Fn) and its N-terminal 29 K fragment (FnF) on group A streptococci were studied by electron microscopy using these proteins labelled with colloidal gold. The investigated strains exhibited a different labelling intensity as well as a different labelling pattern varying from a strong regular distribution to a weak focal binding. Binding of Fn and FnF was inhibited by itself as well as by lipoteichoic acid (LTA), anti-LTA and concanavalin A. Simultaneous labelling of the bacteria with marker complexes of FnF, human serum albumin and fibrinogen revealed separate receptor sites for each protein. Our results confirmed LTA to be mainly responsible for the binding of Fn on group A streptococci.