Comparison of the plaque microflora in immunodeficient and immunocompetent dental patients

Transplantation-associated long-term immunosuppression promotes oral colonization by potentially opportunistic pathogens without impacting other members of the salivary bacteriome

Solid-organ transplant recipients rely on pharmacological immunosuppression to prevent allograft rejection. The effect of such chronic immunosuppression on the microflora at mucosal surfaces is not known. We evaluated the salivary bacterial microbiome of 20 transplant recipients and 19 nonimmunosuppressed controls via 454 pyrosequencing of 16S rRNA gene amplicons. Alpha-diversity and global community structure did not differ between transplant and control subjects. However, principal coordinate analysis showed differences in community membership. Taxa more prevalent in transplant subjects included operational taxonomic units (OTUs) of potentially opportunistic Gammaproteobacteria such as Klebsiella pneumoniae, Pseudomonas fluorescens, Acinetobacter species, Vibrio species, Enterobacteriaceae species, and the genera Acinetobacter and Klebsiella. Transplant subjects also had increased proportions of Pseudomonas aeruginosa, Acinetobacter species, Enterobacteriaceae species, and Enterococcus faecalis, among other OTUs, while genera with increased proportions included Klebsiella, Acinetobacter, Staphylococcus, and Enterococcus. Furthermore, in transplant subjects, the dose of the immunosuppressant prednisone positively correlated with bacterial richness, while prednisone and mycophenolate mofetil doses positively correlated with the prevalence and proportions of transplant-associated taxa. Correlation network analysis of OTU relative abundance revealed a cluster containing potentially opportunistic pathogens as transplant associated. This cluster positively correlated with serum levels of C-reactive protein, suggesting a link between the resident flora at mucosal compartments and systemic inflammation. Network connectivity analysis revealed opportunistic pathogens as highly connected to each other and to common oral commensals, pointing to bacterial interactions that may influence colonization. This work demonstrates that immunosuppression aimed at limiting T-cell-mediated responses creates a more permissive oral environment for potentially opportunistic pathogens without affecting other members of the salivary bacteriome.

Oral manifestations in selective IgA deficiency

Selective immunoglobulin A (IgA) deficiency is the most common of the primary immunodeficiencies with a frequency of 1/300-1/3000, depending on the screened population. As secretory IgA (SIgA) has a protective role in mucosal surfaces from invasion of microorganisms, it is thought that IgA-deficient subjects are susceptible to periodontal diseases and oral manifestations. Previous studies show contradictory results, concerning the involvement of the individuals' periodontium with IgA deficiency. The aim of this study was to investigate and compare the oral manifestations in IgA-deficient subjects with controls. Eleven selective IgA-deficient subjects aged 3-18 years with serum IgA levels <10 mg dl(-1) and 11 age-sex-matched healthy children as the controls entered the study. Oral mucosal investigation, dental caries, plaque accumulation and periodontal status were assessed. Serum immunoglobulin levels were measured by single radial immunodiffusion (SRID) method. Saliva immunoglobulins and secretory component levels were measured by enzyme linked immunosorbent assay (ELISA) methods. IgA-deficient patients had serum and saliva IgA levels less than 10 mg dl(-1) and 10 microg ml(-1), respectively, but other serum immunoglobulin levels were normal and saliva immunoglobulin M (IgM) levels were increased, compared with controls. There were no significant differences in oral manifestations between IgA-deficient subjects and controls, which may be a result of compensatory increase of saliva IgM or other non-immunological defence factors in saliva. Thus, it is not necessary to evaluate IgA and SIgA in all the patients with oral and dental lesions and it is thought that it is better to investigate other factors.

Dose-dependent modulation of octacalcium phosphate crystal habit by amelogenins

In vitro studies on interactions between amelogenins and calcium phosphate crystals are critical for elucidating biomineralization mechanisms of tooth enamel. This work was aimed at investigating the effects of native porcine amelogenins on octacalcium phosphate (OCP) crystal growth in a gelatin gel. We prepared OCP mineral discs by circulating calcium and phosphate solutions on the opposite ends of the gels loaded with 0-2% amelogenin for one week. A dose-dependent modulation of OCP crystal habit by amelogenins was observed by scanning electron microscopy. While the incorporation of 0.125, 0.25, or 0.5% amelogenins showed no significant effect on the crystal morphology, in the presence of 1 and 2% amelogenins, the crystals were remarkably longer, having an average aspect ratio 3-5 times greater than that of those formed in the control gels. Transmission electron microscopy and atomic force microscopy suggested that amelogenin assemblies selectively blocked b-axial development, resulting in the c-axial elongation of OCP crystals.

Antimicrobial function of human saliva--how important is it for oral health?

Human saliva contains a number of physical physicochemical, and chemical agents that protect oral tissues against noxious compounds, in particular those produced by various microorganisms. Among such protective factors, the flushing effect of saliva flow is the most important one, not only because it so effectively removes exogenous and endogenous microorganisms and their products into the gut but also because a steady supply of saliva guarantees continuous presence of both non-immune and immune factors in the mouth. A great number of studies with controversial results have been published regarding various individual agents and their possible association to oral health, particularly to dental caries. It appears that no single chemical agent is far more important than the others. For example, patients with selective IgA deficiency have normal levels of non-immune defense factors and often display a compensatory increase in the other immunoglobulin isotypes. The concerted action of all agents in whole saliva, both saliva- and serum-derived, provides a multifunctional protective network that is collapsed only if salivary flow rate is substantially reduced. In this mixture of defense factors, many show additive or even synergistic interactions against oral pathogens. Increased knowledge of the molecular functions of various agents has made it possible to prepare oral hygiene product that include host-derived antimicrobial agents instead of synthetic agents. Although the clinical efficacy of such products is still unsatisfactory and poorly described, new technologies, for example in the production of specific antibodies against oral pathogens, may considerably improve the antimicrobial power of these products.

Oral microbial ecology and the role of salivary immunoglobulin A

In the oral cavity, indigenous bacteria are often associated with two major oral diseases, caries and periodontal diseases. These diseases seem to appear following an imbalance in the oral resident microbiota, leading to the emergence of potentially pathogenic bacteria. To define the process involved in caries and periodontal diseases, it is necessary to understand the ecology of the oral cavity and to identify the factors responsible for the transition of the oral microbiota from a commensal to a pathogenic relationship with the host. The regulatory forces influencing the oral ecosystem can be divided into three major categories: host related, microbe related, and external factors. Among host factors, secretory immunoglobulin A (SIgA) constitutes the main specific immune defense mechanism in saliva and may play an important role in the homeostasis of the oral microbiota. Naturally occurring SIgA antibodies that are reactive against a variety of indigenous bacteria are detectable in saliva. These antibodies may control the oral microbiota by reducing the adherence of bacteria to the oral mucosa and teeth. It is thought that protection against bacterial etiologic agents of caries and periodontal diseases could be conferred by the induction of SIgA antibodies via the stimulation of the mucosal immune system. However, elucidation of the role of the SIgA immune system in controlling the oral indigenous microbiota is a prerequisite for the development of effective vaccines against these diseases. The role of SIgA antibodies in the acquisition and the regulation of the indigenous microbiota is still controversial. Our review discusses the importance of SIgA among the multiple factors that control the oral microbiota. It describes the oral ecosystems, the principal factors that may control the oral microbiota, a basic knowledge of the secretory immune system, the biological functions of SIgA, and, finally, experiments related to the role of SIgA in oral microbial ecology.

Colonization of Candida albicans on cleaned human dental hard tissues

Candida albicans is a fungus that commonly infects oral mucosal surfaces. Limited data exist on biofilm formation by C. albicans on dental surfaces. Human premolar teeth were infected with C. albicans for 10 days and hard-tissue surfaces were examined with a scanning electron microscope. Enamel, cementum and dentine, in the absence or presence of a smear layer, were readily colonized by this micro-organism. Hyphae penetrated into cracks, followed the ridges of the cavities and migrated into dentinal tubules. Blastospores and hyphae were embedded in an extracellular material. These findings suggest that dental hard tissues may be invaded by C. albicans and thus can potentially present a reservoir for disseminating candidal infections.

No apparent influence of immunoglobulins on indigenous oral and intestinal microbiota of mice

The role of secretory immunoglobulin A (sIgA) in the control of the indigenous microbiota is not well understood. In this study, we compared the oral and intestinal microbiota of transgenic B-cell-deficient (microMT) mice with their heterozygous (microMT/+) normal littermates. The levels of salivary IgA and serum IgA and IgG were normal in microMT/+ mice, while no immunoglobulins were detected in microMT/microMT mice. The acquisition and proportions of the different species of the oral and intestinal indigenous bacterial populations were not significantly different between the two groups of mice. Our results thus suggest that secretory IgA does not play a major role in the regulation of the indigenous microbiota of mice.

Relationship of oral microflora with oral health status in Parkinson's disease

Parkinson's disease (PD) patients report an increased craving for sweets, which may have an effect on microflora. We compared patients of PD who crave sweets with PD patients who do not. Age- and sex-matched control subjects were used, with 14 subjects in each group. A plaque sample was taken from tooth #18 with a curette and placed into RTF, homogenized, and plated onto selective and non-selective media. Microflora were expressed as % CFU's of total anaerobes. Statistical analysis was performed by ANOVA and Newman-Keuls on log-transformed data. No statistical difference was observed among the three groups for lactobacilli, bacteroides, fusobacteria, veillonella, and actinomyces. S. mutans was lower in controls than in PD patients. Apparently, the craving for sweets in PD patients does not result in a significant increase in % of total anaerobes of certain microflora. PD patients showed a significant increase in mucositis compared with the control groups.

Salivary defense factors and oral health in patients with common variable immunodeficiency

Studies of oral health in patients with common variable immunodeficiency have given controversial results. Obviously, one major factor modifying the oral health of these patients is saliva, in which the antibody-mediated defense is remarkably impaired compared to that of healthy subjects. However, the occurrence of nonimmunoglobulin (innate) antimicrobial agents in saliva of these patients is virtually unknown. Therefore, we analyzed both immune (total IgA, IgG, IgM, anti-Streptococcus mutans IgA, IgG, and IgM antibodies) and nonimmune (lysozyme, lactoferrin, salivary peroxidase, myeloperoxidase, hypothiocyanite, thiocyanate, and agglutinins) factors in whole saliva of 15 patients with common variable immunodeficiency. All patients were on Ig-replacement therapy (median duration, 10 years; range, 2-25 years), which had normalized their IgG but not their IgA or IgM levels both in serum and in saliva. Also, comprehensive clinical and microbiological analyses were made. The control group comprised 15 age- and sex-matched immunologically healthy subjects. The results showed no notable differences in dental caries, periodontal diseases, or salivary microorganisms but the patients had a history of more frequent oral mucosal lesions and respiratory infections. All innate, nonimmune salivary defense factors were equally abundant in the patients as in the controls, in many cases even at somewhat higher concentrations. These findings suggest that in spite of immunodeficiency, patients with common variable immunodeficiency display normal, perhaps even slightly elevated, levels of nonimmunoglobulin defense factors in whole saliva.(ABSTRACT TRUNCATED AT 250 WORDS)

Local radiation and systemic chemotherapy: preventing and managing the oral complications

About 50 percent of cancer patients develop acute or chronic oral side effects from their treatments. Pretreatment strategies, oral care during treatment and close follow-ups can control these complications.

Periodontal disease and dental caries in relation to primary IgG subclass and other humoral immunodeficiencies

22 females and 3 males with primary hypogammaglobulinaemia (n = 6) or IgG subclass deficiencies with (n = 3) or without (n = 16) concomitant IgA deficiency were examined for periodontal disease and dental caries. Only 1 patient showed more tooth loss than that found in the normal Swedish population. 1 patient demonstrated advanced periodontal disease. No patient exhibited more severe dental caries than that of comparable normal Swedes. Microbiological samples from periodontal pockets and saliva showed recovery of potential periodontopathic and cariogenic bacteria within normal ranges. This study could not support the notion that immunodeficient subjects exhibit an increased risk of developing periodontal disease or dental caries.

Gram-negative enteric bacteria in the oral cavity of leukemia patients

We examined changes in the bacterial flora in hospitalized patients with leukemia. This study placed special emphasis on enteric microorganisms and their relation to the general status of the patient. One hundred thirty bacterial cultures from 16 leukemia patients and 16 control subjects, were obtained. The organisms were isolated on MacConkey agar and identified by the API-20E system. Enteric microorganisms were isolated from 62.2% of the leukemia patients as compared with 28% from the control group (p < 0.001). The enteric positive cultures were identified as Klebsiella (42.7%), Enterobacter (18.8%), and Pseudomonas (15.6%). In contrast to the negative cultures (1342), enteric microorganisms were cultured from 2948 specimens (p < 0.005).

Microbiological testing in the diagnosis of periodontal disease

The oral microbiota plays a primary role in the initiation and progression of the most common forms of periodontal disease. Because of the multiplicity of factors that control the establishment and long-term evolution of the oral microbiota, a great deal of heterogeneity exists in the composition of the periodontal microbiota among individual subjects. Despite these individual differences and the complex interactions between bacteria and the host and among bacteria, an association has been demonstrated between certain species and various forms of periodontal disease. However, the predictive value of either positive or negative tests for selected bacterial species has not proved to be high enough for routine use in clinical practice. Nevertheless, bacteriological tests have been of value in the management of patients with juvenile periodontitis and refractory forms of periodontal disease. The increasing availability of diagnostic laboratory services and diagnostic kits for office use will make it easier for the practitioner to select appropriate antimicrobial treatments and monitor patients undergoing antimicrobial therapy.

Cardiac transplantation: dental considerations

The same basic principles of dental management of the immunocompromised patient apply to patients receiving cardiac transplants: preimmunosuppressive therapy examination and elimination of all existing and potential sources of infection; counseling regarding the importance of meticulous oral hygiene obviating further medical complications; and frequent oral health assessments for interception of emerging oral problems, maintenance, and reinforcement of good oral care. Dental practitioners familiar with the more numerous patients with renal transplants will find differing therapy complications secondary to immunosuppression and maintenance drug regimens. The dental approach to the candidate for a cardiac transplant will differ in degree of morbidity and complexity of delivering necessary oral care before transplantation.

Oral manifestations of systemic chemotherapy and their management

Many antineoplastic drugs in use now have cytotoxic side effects that also manifest in the oral cavity or influence dental management. Chemotherapeutic agents that have a high potential for precipitating oral mucosal damage and bone marrow depression are methotrexate, cyclophosphamide, daunorubicin, doxorubicin hydrochloride, 5-fluorouracil, bleomycin, nitrogen mustard, cytosine-arabinoside, 6-mercaptopurine, busulfan, and L-phenylalanine mustard. Mucositis may lead to neglected oral hygiene, which in turn may cause a chain reaction of local infections, bleeding, and septicemia in myelosuppressed patients. Preventive oral care before chemotherapy and active oral care during therapy are necessary for compromised patients. A protocol for oral care is described.