Oral and oropharyngeal prevalence of Enterobacteriaceae in humans: a review

Chitosan nanoparticles efficiently enhance the dispersibility, stability and selective antibacterial activity of insoluble isoflavonoids

Natural isoflavonoids have attracted much attention in the treatment of oral bacterial infections and other diseases due to their excellent antibacterial activity and safety. However, their poor water solubility, instability and low bioavailability seriously limited the practical application. In this study, licoricidin-loaded chitosan nanoparticles (LC-CSNPs) were synthesized by self-assembly for improving the dispersion of licoricidin (LC) and strengthening antibacterial and anti-biofilm performance. Compared to free LC, the minimum inhibitory concentration of LC-CSNPs against Streptococcus mutans decreased >2-fold to 26 μg/mL, and LC-CSNPs could ablate 70 % biofilms at this concentration. The enhanced antibacterial activity was mainly attributed to the spontaneous surface adsorption of LC-CSNPs on cell membranes through electrostatic interactions. More valuably, LC-CSNPs had no inhibitory effect on the growth of probiotic. Mechanism study indicated that LC-CSNPs altered the transmembrane potential to cause bacterial cells in a hyperpolarized state, generating ROS to cause cells damage and eventually apoptosis. This work demonstrated that the chitosan-based nanoparticles have great potential in enhancing the dispersibility and antibacterial activity of insoluble isoflavonoids, offering a promising therapeutic strategy for oral infections.

Influence of Nonnutritive Sucking Habits on the Oral Carriage of Escherichia coli

OBJECTIVES

This study aimed to evaluate the impact of nonnutritive sucking habits on the presence of oral Escherichia coli.

METHODS

One hundred and twenty children aged 3-5 years old were enrolled in the present case-control study, as follows: 60 children with continuous pacifier and thumb sucking habits (study group) and 60 children without any sucking habits (control group). The children in the two groups were matched in terms of age and gender. Information was gathered from the parents concerning their children using a special sheet. Sterile swabs were taken from both groups and cultured on agar plates. Then, they were subjected to further biochemical tests to identify E. coli species. The mean of the E. coli count was determined for each child. Descriptive, independent t-test and chi-square test statistics were used. The level of significance was set at p < 0.05.

RESULTS

The presence of nonnutritive sucking habits was related to a higher carriage of E. coli among children.

CONCLUSION

Nonnutritive sucking habits may act as a predisposing factor that enhances the colonization of oral E. coli.

Prevalence and antimicrobial susceptibility of Gram-negative bacilli in subgingival biofilm associated with periodontal diseases

BACKGROUND

This cross-sectional study aimed to determine the prevalence and antimicrobial susceptibility of Gram-negative bacilli (GNB) isolated from subgingival biofilm of individuals with different periodontal conditions.

METHODS

Subgingival biofilm was obtained from 362 individuals with periodontal health (PH) (n = 83), gingivitis (n = 74), and periodontitis (n = 205), cultivated in broth and selective media. Isolated strains were identified by mass spectrometry. Antimicrobial susceptibility was determined by the Clinical and Laboratory Standards Institute disk diffusion guidelines. Production of extended-spectrum beta-lactamase (ESBL) and carbapenemases were evaluated by double disk synergy test and spectrophotometric detection of imipenem hydrolysis, respectively. ESBL and carbapenemase encoding genes were surveyed by Polymerase chain reaction (PCR). Differences among groups were examined by Chi-square, Kruskal-Wallis or Mann-Whitney tests.

RESULTS

GNB were isolated from 36.2% of all subgingival biofilm samples, with a significantly greater prevalence and species diversity (P < 0.001) in patients with periodontitis (45.9%) compared with individuals with PH (24.1%) and gingivitis (22.9%). Pseudomonas aeruginosa (27.5%), Enterobacter cloacae (16.8%), and Enterobacter asburiae (10.7%) were the most predominant species. Resistance/reduced sensitivity to at least 1 antimicrobial was detected in 60% of the strains, but only 4.6% were multidrug resistant. Serratia marcescens, E. cloacae, and Enterobacter kobei presented high rates of intrinsic resistance (>40%) to amoxicillin-clavulanate and first/second-generations of cephalosporins. One strain of Klebsiella pneumoniae isolated from periodontitis was resistant to imipenem, but no ESBL encoding genes or ESBL phenotype was detected.

CONCLUSION

High prevalence and diversity of GNB, with low susceptibility to β-lactams are observed in the subgingival microbiota associated with periodontitis.

Applying Pb2+ to probe the dissolution of carbonated hydroxylapatite by Enterobacter sp.: A new insight into the bioerosion of tooth mineral

Dental caries is one of the most common disorders in dentistry. Typically, it is caused by the dissolution of the tooth mineral due to cariogenic organisms. Bioapatite is vulnerable to acid-etching ascribed to a variety of substitutions. This study applied Pb²⁺ cations to probe the dissolution of synthetic carbonated hydroxylapatite (CHAp) in the acidic environment induced by Enterobacter sp. It indicated a decreasing tendency of crystallite size (from ∼400 nm to 10-20 nm) during gradual incorporation of carbonate (from 2.5 to 13.8 wt %). Meanwhile, the shape of CHAp crystals was transformed from elongated to plate-like. Addition of Enterobacter sp. enhanced P release from CHAp (especially for the CHAp with ∼8 wt % CO₃ ) around 10 times. Moreover, the bacterium provided a moderately acidic environment to cause more formation of stable pyromorphite over other Pb-minerals, for example, Pb₃ (PO₄ )₂ , and PbCO₃ . Then, transmission electron microscopy-energy dispersive X-Ray spectroscopy mapping successfully confirmed the Pb labeling on the newly formed phosphate mineral as Pb (with high-atomic weight) has strong signal under electron microscopy. This study therefore elucidated that Pb labeling has a bright future to explore the degradation of tooth mineral by microorganisms, as well as to evaluate the resistance of calcium phosphate dental restorative materials.

Potential effect of Allium sativum bulb for the treatment of biofilm forming clinical pathogens recovered from periodontal and dental caries

Biofilm producing clinical bacterial isolates were isolated from periodontal and dental caries samples and identified as, Lactobacillus acidophilus, Streptococcus sanguis, S. salivarius, S. mutansand Staphylococcus aureus. Among the identified bacterial species, S. aureus and S. mutansshowed strong biofilm producing capacity. The other isolated bacteria, Streptococcus sanguis, S. salivarius showed moderate biofilm formation. These pathogens were subjected for the production of extracellular polysaccharides (EPS) in nutrient broth medium and the strain S. aureus synthesized more amounts of EPS (610 ± 11.2 µg/ml) than S. sanguis (480 ± 5.8 µg/ml).EPS production was found to be less in S. salivarius (52 ± 3.8 µg/ml).The solvent extract of A. sativum bulb showed the phytochemicals such as, carbohydrate, total protein, alkaloids, saponins, flavonoids, tannins and sterioids. The solvent extract of A. sativum bulb showed wide ranges of activity against the selected dental pathogens. The difference in antibacterial activity of the solvent extract revealed differences in solubility of phytochemicals in organic solvents. Ethanol extract was highly active againstS. aureus (25 ± 2 mm). The Minimum Inhibitory Concentration (MIC) of crude garlic bulb varied widely and this clearly showed that bacteria exhibits different level of susceptibility to secondary metabolites. MIC value ranged between 20 ± 2 mg/ml and 120 ± 6 mg/ml and Minimum Bactericidal Concentration (MBC) value ranged from 60 ± 5 mg/l to 215 ± 7 mg/ml. To conclude, A. sativum bulb can be effectively used to treat periodontal and dental caries infections.

Chronic nail biting, orthodontic treatment and Enterobacteriaceae in the oral cavity

Background

Chronic nail biting is common in children and young adults. Auto inoculation of environmental pathogens can manifest as infection in distant organs. Multi-drug resistance gram negative bacteria are on the rise globally. Several of the foodborne bacteria fall within the Enterobacteriaceae family but very few studies have explored these microbes in the oral cavity of children with chronic nail-biting habit or orthodontic treatment. The study aims to investigate oral load of Enterobacteriaceae in children with chronic nail-biting habit and or those undergoing orthodontic treatment.

Material and Methods

150 children (no nail-biting n=30, nail biting n=60, fixed orthodontic treatment n =30 and a combination of fixed orthodontic appliance use and nail-biting habit n =30) were assessed for culture based microbiological investigation. The concentrated oral rinse technique was used. The rinse was inoculated in MacConkey’s and Blood Agar. The gram stained culture was subjected to biochemical tests for sub-species identification using Biomerieux Vitek 2 Compact Automated Microbiological Analyzer. Fisher’s exact and Kruskal Wallis with post hoc analysis using Dunn method was performed to test association and difference between groups.

Results

Enterobacteriaceae was positive for 72% of the children. Of them, nail biting or orthodontic treatment group comprised 89%. Those with a combination of nail biting and undergoing orthodontic treatment exhibited highest CFU/ml and those without nail biting or orthodontic treatment exhibited the lowest. Three of the four organisms isolated tested positive in the orthodontic treatment group. E. coli was positive in 38% of the children while Klebsiella and E. cloacae were isolated exclusively in the orthodontic treatment group.

Conclusions

Chronic nail biting or the use of fixed orthodontic appliances is associated with higher incidence of Enterobacteriaceae in the oral cavity. Oral health professionals play an important role in preventing multi drug resistance infectious diseases.

Key words:Enterobacteriaceae, nail-biting, Onychophagia, orthodontic treatment.

Subgingival prevalence rate of enteric rods in subjects with periodontal health and disease

BACKGROUND

The prevalence of enteric rods and their association with chronic periodontitis has gained prominence recently. Although the prevalence of these organisms from the subgingival plaque sample was reported in the literature, the carriage rate of these rods in our population is lacking. The present study was undertaken to know the carriage rate of enteric rods from our population in patients with periodontal health and disease.

MATERIALS AND METHODS

Eighty-four systemically healthy participants, inclusive of 46 males and 38 females, were selected for the study. The selected participants were subjected to a periodontal examination and were categorized into chronic periodontitis and healthy group. Subgingival plaque samples were taken from all the participants, plated onto McConkey agar plates, and incubated overnight at 37° C to check for the growth of organisms. The grown organisms were then cultured according to the standard procedures.

RESULTS

Prevalence of 71% and 83% of enteric rods in subjects with periodontal health and disease, respectively, was found in our study which was not statistically significant.

CONCLUSION

Although no significant differences exist in the prevalence of enteric rods between healthy and patients with chronic periodontitis, the prevalence rate of enteric rods in subgingival plaque samples is considerably high in our population.

Periodontal-disease-associated biofilm: A reservoir for pathogens of medical importance

The ecological diversity of the periodontal microenvironment may provide suitable conditions for the colonization of species not usually considered members of the oral microbiota. In this investigation, we aimed to determine the prevalence and levels of pathogenic species of medical relevance in the microbiota of individuals with distinct periodontal clinical status. Subgingival biofilm was obtained from patients with periodontal health (H, n = 81), gingivitis (G, n = 55), generalized aggressive (AgP, n = 36) or chronic periodontitis (CP, n = 98), and analyzed for 39 microbial taxa using a checkerboard DNA-DNA hybridization technique. Microbial differences among groups, as well as associations between clinical and microbiological parameters were sought by non-parametric and univariate correlation tests. Neisseria spp., Peptostreptococus anaerobius, Candida albicans, enterobacteria, Pseudomonas aeruginosa, Eubacterium saphenum, Clostridium difficile and Olsenella uli were detected in high mean prevalence and counts in the subgingival microbiota of the study population. Species that were more related to periodontal inflammation and tissue destruction at the patient and site levels included enterobacteria, C. albicans, Neisseria spp., P. aeruginosa, O. uli, Hafnia alvei, Serratia marcescens and Filifactor alocis (p < 0.05). In contrast, Fusobacterium necrophorum, Lactobacillus acidophilus, Staphylococcus aureus and Streptococcus pneumoniae were associated with periodontal health (p < 0.05). Pathogenic species of medical importance may be detected in high prevalence and levels in the periodontal microbiota. Regardless of their role in periodontal health or disease, the periodontal biofilm may be a source for dissemination and development of systemic infections by these pathogenic microorganisms.

Influence of nail biting and finger sucking habits on the oral carriage of Enterobacteriaceae

BACKGROUND

Oral habits like thumb sucking and nail biting are pernicious habits that act as an adaptive function in obtaining pleasure and subduing anxiety. These habits may also act as carriers of numerous microorganisms into the oral cavity, of which, Enterobacteriaceae members are transient pathogens, which might result in debilitating systemic conditions.

AIM

To study the oral carriage of Enterobacteriaceae in children having habit of nail biting and thumb sucking. And to study the association of the organism with the individual's respective plaque indices.

SUBJECTS AND METHODS

Totally, 40 chronic nail biters, 40 chronic thumb suckers, and 20 controls (no habit) (8-15 years old) were enrolled in the study. Appropriate history and their plaque indices recorded. Sterile containers were used to collect the salivary samples and later cultured on Agar plates. Biochemical tests categorized the organisms into subspecies.

STATISTICAL ANALYSIS USED

ANNOVA, Student's t-test.

RESULTS

Presence of a nail biting habit indicated a higher plaque index, which in turn showed a higher carriage of Enterobacteria spps, predominantly Escherichia coli.

CONCLUSIONS

Oral surgical intervention in individuals with pernicious oral habits need to be counseled and educated on the possible complications, which might otherwise provide an environment that disseminates these microorganisms resulting in a broad range of local and systemic infections.

Enterobacteriaceae isolates from the oral cavity of workers in a Brazilian oncology hospital

The evaluation of workers as potential reservoirs and disseminators of pathogenic bacteria has been described as a strategy for the prevention and control of healthcare-associated infections (HAIs). The aim of this study was to evaluate the presence of Enterobacteriaceae in the oral cavity of workers at an oncology hospital in the Midwest region of Brazil, as well as to characterize the phenotypic profile of the isolates. Saliva samples of 294 workers from the hospital's healthcare and support teams were collected. Microbiological procedures were performed according to standard techniques. Among the participants, 55 (18.7%) were colonized by Enterobacteriaceae in the oral cavity. A total of 64 bacteria were isolated, including potentially pathogenic species. The most prevalent species was Enterobacter gergoviae (17.2%). The highest rates of resistance were observed for β-lactams, and 48.4% of the isolates were considered multiresistant. Regarding the enterobacteria isolated, the production of ESBL and KPC was negative. Nevertheless, among the 43 isolates of the CESP group, 51.2% were considered AmpC β-lactamase producers by induction, and 48.8% were hyper-producing mutants. The significant prevalence of carriers of Enterobacteriaceae and the phenotypic profile of the isolates represents a concern, especially due to the multiresistance and production of AmpC β-lactamases.

The saliva microbiome of Pan and Homo

Background

It is increasingly recognized that the bacteria that live in and on the human body (the microbiome) can play an important role in health and disease. The composition of the microbiome is potentially influenced by both internal factors (such as phylogeny and host physiology) and external factors (such as diet and local environment), and interspecific comparisons can aid in understanding the importance of these factors.

Results

To gain insights into the relative importance of these factors on saliva microbiome diversity, we here analyze the saliva microbiomes of chimpanzees (Pan troglodytes) and bonobos (Pan paniscus) from two sanctuaries in Africa, and from human workers at each sanctuary. The saliva microbiomes of the two Pan species are more similar to one another, and the saliva microbiomes of the two human groups are more similar to one another, than are the saliva microbiomes of human workers and apes from the same sanctuary. We also looked for the existence of a core microbiome and find no evidence for a taxon-based core saliva microbiome for Homo or Pan. In addition, we studied the saliva microbiome from apes from the Leipzig Zoo, and found an extraordinary diversity in the zoo ape saliva microbiomes that is not found in the saliva microbiomes of the sanctuary animals.

Conclusions

The greater similarity of the saliva microbiomes of the two Pan species to one another, and of the two human groups to one another, are in accordance with both the phylogenetic relationships of the hosts as well as with host physiology. Moreover, the results from the zoo animals suggest that novel environments can have a large impact on the microbiome, and that microbiome analyses based on captive animals should be viewed with caution as they may not reflect the microbiome of animals in the wild.

Effect of oral hygiene interventions on opportunistic pathogens in patients after stroke

BACKGROUND

Despite the role of the oral cavity as a reservoir of opportunistic pathogens for infection in patients following stroke, the evaluation of the effects of oral hygiene interventions has been largely neglected.

METHODS

This randomized clinical trial included 102 patients undergoing hospital-based rehabilitation for stroke. Patients were randomized to one of 3 groups: oral hygiene instruction (OHI) only; OHI and 0.2% chlorhexidine mouth rinse twice daily; or OHI, 0.2% chlorhexidine mouth rinse twice daily, and assisted brushing twice weekly. Oral samples were obtained at baseline and after 3 weeks for detection of Staphylococcus aureus, aerobic and facultatively anaerobic gram-negative bacilli, and yeasts.

RESULTS

Almost three-quarters (72.8%) of the patients harbored oral anaerobic gram-negative bacilli at baseline, and more than half had detectable S aureus (56.8%) and yeasts (59.3%). Percentage frequencies and viable counts of pathogens remained relatively stable during the course of the clinical trial, and no significant differences were observed among the 3 patient groups.

CONCLUSIONS

In our study cohort, there was no significant difference in the effectiveness of the 3 different oral hygiene interventions on the prevalence or viable counts of oral opportunistic pathogens.

Enterobacteriaceae and pseudomonadaceae on the dorsum of the human tongue

OBJECTIVE

The aim of this study was to correlate the presence of Enterobacteriaceae, Pseudomonadaceae, Moraxellaceae and Xanthomonadaceae on the posterior dorsum of the human tongue with the presence of tongue coating, gender, age, smoking habit and denture use.

MATERIAL AND METHODS

Bacteria were isolated from the posterior tongue dorsum of 100 individuals in MacConkey agar medium and were identified by the API 20E system (Biolab-Mérieux).

RESULTS

43% of the individuals, presented the target microorganisms on the tongue dorsum, with greater prevalence among individuals between 40 and 50 years of age (p = 0.001) and non-smokers (p=0.0485).

CONCLUSIONS

A higher prevalence of Enterobacteriaceae and Pseudomonadaceae was observed on the tongue dorsum of the individuals evaluated. There was no correlation between these species and the presence and thickness of tongue coating, gender and presence of dentures.

Oral carriage of yeasts and coliforms in stroke sufferers: a prospective longitudinal study

AIM

To investigate prospectively the qualitative and quantitative changes in oral carriage of yeasts and coliforms in southern Chinese people suffering from stroke.

MATERIALS AND METHODS

In 56 elderly people suffering from stroke in a rehabilitation unit of a general medical hospital in Hong Kong, oral microbiological sampling using a combined imprint culture, oral rinse approach and clinical assessment was made during the acute stroke phase, on hospital discharge and 6 months later.

RESULTS

The oral carriage of yeasts increased significantly during acute stroke (P<0.05), whereas coliform carriage did not. A reduction in oral carriage of yeasts was found on hospital discharge and 6 months later and in coliforms at the 6-month assessment (P<0.05). Candida albicans and Klebsiella pneumoniae were the predominant yeast and coliform respectively. Stroke-related difficulty in tooth brushing and denture wearing were associated with higher oral yeast carriage (P<0.05). We also report here for the first time that the use of aspirin was associated with lower oral yeast carriage in people suffering from stroke.

CONCLUSION

Oral yeast carriage was closely linked to the level of stroke-related functional disability that improved over time but had not totally resolved 6 months after hospital discharge. The oral reservoir of yeasts and coliforms in people suffering from stroke is noteworthy by care providers as K. pneumoniae may cause aspiration pneumonia.

Occurrence of Periodontopathic and Superinfecting Bacteria in Chronic and Aggressive Periodontitis Subjects in a Colombian Population

BACKGROUND

Differences in the composition of subgingival microbiota in periodontitis have been observed in different geographic locations. Some of these microbial differences could have clinical significance. This study describes clinical parameters and the composition of the subgingival microbiota in chronic periodontitis (CP) and aggressive periodontitis (AgP) patients in a Colombian population.

METHODS

Clinical parameters (probing depth, clinical attachment level, bleeding on probing, and plaque index) and plaque samples from 68 CP, 12 AgP, and 30 periodontally healthy subjects were analyzed. Subgingival samples were processed using culture, biochemical tests, and polymerase chain reaction for the detection of periodontal and superinfecting pathogens. The analysis of variance, chi(2), and Kruskal-Wallis tests were used to evaluate differences between groups for clinical parameters and microbiologic composition (P <or=0.05).

RESULTS

Clinical parameters were significantly increased in CP and AgP patients compared to healthy subjects (P <0.001), but no differences were found between periodontitis groups. Porphyromonas gingivalis, Tannerella forsythensis, and Eikenella corrodens showed higher frequencies in AgP compared to CP and healthy subjects (P <0.05). Extension (localized and generalized) of the periodontal destruction had no effect on the composition of the subgingival microbiota. Gram-negative enteric rods were more frequent in AgP patients (P <0.01).

CONCLUSIONS

This study demonstrated a high prevalence of P. gingivalis, T. forsythensis, and E. corrodens in AgP patients. Gram-negative enteric rods were frequent in AgP and CP patients. Differences in the composition of subgingival microbiota in periodontitis patients need to be taken into account when considering the best therapeutic approach for each individual, including the use of antibiotics.

Effect of a chronic nail-biting habit on the oral carriage of Enterobacteriaceae

BACKGROUND/AIMS

Nail biting is a common oral habit in children and young adults. However, its effect on the oral carriage of Enterobacteriaceae is unclear. The purpose of the study was to evaluate the differences in prevalence of Enterobacteriaceae in saliva samples from subjects with and without a nail-biting habit.

METHODS

Saliva samples were taken from 25 subjects who were nail-biters and 34 subjects with no oral habit. The mean chronological age for all subjects was 13.5 +/- 1.9 years. The saliva samples were studied microbiologically. A Pearson chi-squared test was performed to compare the prevalence of Enterobacteriaceae in the saliva samples of the subjects with and without nail-biting habits.

RESULTS

Statistically significant differences were found in the prevalence of Escherichia coli and total Enterobacteriaceae between both groups (P < 0.001). E. coli, Enterobacter aerogenes, Enterobacter cloacae and Enterobacter gergoviae were found in the saliva samples of 19 of the 25 nail-biting subjects (76%), whereas E. coli, E. aerogenes and E. cloacae were detected in the saliva samples of only nine of the 34 subjects who were not nail-biters (26.5%).

CONCLUSION

According to the results of the present study, the Enterobacteriaceae were more prevalent in the oral cavities of children with nail-biting habits than in children with no oral habit.

Oral infections and systemic diseases

An association between periodontal infection and CVD has been revealed in some epidemiologic studies, whereas other studies were unable to demonstrate such an association. A link between the two diseases may be explained by shared established or nonestablished risk factors. Future studies with extended control of confounding factors and intervention studies may add to the understanding of a possible relationship between the diseases. In some cases, IE is caused by dental plaque bacteria. Several studies are suggestive of oral bacteria causing respiratory infection. The pathogenesis and course of a number of other diseases including DM and rheumatoid arthritis have been associated wish periodontitis, but more research is necessary to elucidate possible pathogenic interactions.

Oral colonization of aerobic and facultatively anaerobic gram-negative rods and cocci in irradiated, dentate, xerostomic individuals

This study aimed at investigating the oral colonization of aerobic and facultatively anaerobic gram-negative rods and cocci in head- and neck-irradiated, dentate, xerostomic individuals. Subjects were recruited from a nasopharyngeal carcinoma clinic and were segregated into group A: <60 years (n=25, 48+/-6 years, 5+/-5 years post-irradiation) and group B: >or=60 years (n=8, 67+/-4 years, 2+/-2 years post-irradiation) and were compared with age- and sex-matched normal individuals, group C: <60 years (n=20, 44+/-12 years) and group D: >or=60 years (n=10, 70+/-3 years). Selective culture of the oral rinse samples was carried out to isolate, quantify and speciate (using API 20E kit) aerobic and facultatively anaerobic gram-negative rods and cocci recovery. All test subjects were put under comprehensive oral and preventive care for 3 months, and 12 group A and 5 group B subjects were recalled for reassessment of aerobic and facultatively anaerobic gram-negative rods and cocci colonization. All identical isolates, pre- and post-hygienic care, were phenotypically (Vitek, Hazelwood, MA and antibiogram profile) and genotypically (pulsed-field gel electrophoresis) evaluated. The aerobic and facultatively anaerobic gram-negative rods and cocci isolated from the first round oral rinse samples included: Acinetobacter, Neisseria, Chryseomonas, Flavimonas, Pseudomonas, Citrobacter, Enterobacter, Escherichia, Klebsiella, Flavobacterium and Weeksella species. The aerobic and facultatively anaerobic gram-negative rods and cocci isolation rate was high for irradiated individuals, and they were 64/25% and 100/80% for groups A/C and B/D, respectively. Recovery of aerobic and facultatively anaerobic gram-negative rods and cocci and Klebsiella pneumoniae subsp. pneumoniae in oral rinse samples were found to be significantly more prevalent in the irradiated subjects (groups A and B). Enterobacteriaceae were more frequently isolated from oral rinse samples of aged irradiated subjects (group B vs D, P<0.05), where the quantity of Citrobacter freundii (colony-forming units/ml oral rinse) was also significantly elevated. The isolation rate of aerobic and facultatively anaerobic gram-negative rods and cocci after hygienic care remained unchanged; 3 of 12 and 3 of 5 of the recalled subjects from groups A and B, respectively, harbored same aerobic and facultatively anaerobic gram-negative rods and cocci species. However, only two pairs of K. pneumoniae subsp. pneumoniae, sequentially isolated from same patients in group B, were found to be identical by pulsed-field gel electrophoresis. This may be due to reinfection of the microbes from the same source or permanent colonization. In conclusion, irradiation-induced xerostomia seems to favor frequent, repeated, transient intraoral colonization of aerobic and facultatively anaerobic gram-negative rods and cocci.

Early-onset periodontitis

In 1993, the 1st European Workshop on Periodontology explicitly recognized that there was insufficient knowledge to differentiate truly different forms of periodontal disease from differences in the presentation/severity of the same disease. In spite of recent progress in our understanding of periodontal diseases, the issue is far from having been resolved. Classification of periodontal diseases, therefore, remains based upon the definition of specific clinical syndromes. Early-onset periodontitis (EOP) is one such syndrome and comprises a group of pathological conditions leading to loss of periodontal tissues early in life. The notion that classifies periodontitis syndromes as "early-onset" or "adult" is primarily epidemiological in nature and is based on the observation that periodontitis is rather infrequent in children and young adults. Nevertheless, considerable epidemiological evidence indicates that periodontitis does affect children and young adults to a level of severity that may lead to premature exfoliation of primary and/or permanent teeth. Clinical presentation of periodontitis early in the life of an individual is thought to indicate that the etiologic agents have been able to cause considerable tissue damage over a relatively short period of time. It also implies either infection with highly virulent bacteria and/or a highly susceptible subject. The purpose of this review is to discuss the criteria generally utilized to classify EOP, provide the rationale to designate EOP as a distinct disease entity, and to review the evidence justifying a subclassification into particular subgroups of EOP.

Oral health and microflora in an institutionalised elderly population in Canada

A cross-sectional study was undertaken to assess the oral health of a group of elderly, long-term care, institutionalised residents in a facility in Edmonton, Canada. In addition, the oral occurrence of Candida and coliform micro-organisms was evaluated to examine the relationship between oral health status and oral prevalence of these opportunistic pathogens. The mean age of 63 examined individuals was 83.4 (+/- 17.6) years; 28.6 per cent were dentate with a DMF score of 22.4; 4.5 per cent of teeth exhibited root caries. Of the edentate, 55.5 per cent were wearing complete maxillary and mandibular dentures; 59 per cent of the maxillary dentures and 20 per cent of mandibular dentures were found to exhibit good retention and stability while the remaining prostheses were deemed to be poor; 17 per cent of individuals had neither teeth or dentures. Denture stomatitis was the most common mucosal lesion and was found amongst one third of the denture wearers. Three quarters of the residents harboured oral yeasts, 30 per cent coliforms and a significant number exhibited poor oral hygiene and oral pathoses for which remedial treatment was readily available in the form of subsidised dental care.

Antimicrobial susceptibility of oral isolates of Enterobacter cloacae and Klebsiella pneumoniae from a southern Chinese population

The antibiotic susceptibilities of 59 Enterobacter cloacae and 39 Klebsiella pneumoniae human oral isolates collected from a southern Chinese population in Hong Kong were investigated for their susceptibility to eight antibiotics: ampicillin, cephalothin, cefuroxime, ceftazidime, ciprofloxacin, gentamicin, tetracycline and trimethoprim/sulfamethoxazole using the E-Test method for direct quantification of minimum inhibitory concentrations. Most strains were sensitive to all antibiotics except ampicillin and cephalothin. Ampicillin resistance was exhibited by 82% of K. pneumoniae and 69% of E. cloacae isolates. Eighty-eight percent of E. cloacae isolates were resistant to cephalothin. Several strains fell within the intermediate category of sensitivity for ampicillin (E. cloacae and K. pneumoniae), cefuroxime (E. cloacae) and tetracycline (K. pneumoniae). Comparison with other Hong Kong data suggests that resistance rates to cefuroxime, ceftazidime, ciprofloxacin, gentamicin, tetracycline and trimethoprim/sulfamethoxazole exhibited by the oral isolates are generally lower than in enterobacters and Klebsiella spp. isolated from urine, skin and soft tissues in Hong Kong populations.

Implications of oral infections on systemic diseases in the institutionalized elderly with a special focus on pneumonia

Systemic infection in the elderly patient living in a chronic care setting presents a significant burden to the health care system. The extent to which oral organisms cause systemic infections through hematogenous dissemination in the institutionalized elderly is still unknown. A more likely and common route of systemic infection by oral microorganisms is through aspiration of oropharyngeal fluids containing oral pathogenic microorganisms, which colonize the lower respiratory tract and cause pneumonia. Respiratory pathogens emerge in the dental plaque of elderly patients with very poor oral hygiene and severe periodontal disease. In the chronic care setting, aspiration of oropharyngeal fluids contaminated with these bacteria occurs in patients with diminished host defenses, resulting in bacterial pneumonia. This is also a problem in intensive care units in the hospital setting. In one study, pre-rinsing with a 0.12% chlorhexidine gluconate mouthwash significantly lowered the mortality rate from postsurgical pneumonia in patients undergoing open heart surgery. Selective digestive decontamination, a technique involving the topical application of antimicrobials to reduce the risk of colonization of the respiratory tract, has been used to reduce the incidence of nosocomial pneumonia in the acute care setting of hospitals. This technique has not been employed in the nursing home setting. Whether improving oral hygiene would also lower the risk in either of these settings has not been studied. A number of obstacles must be overcome in designing studies to investigate the relationship between oral infections and lung infections in the institutionalized elderly. Ethical issues must be addressed, and full collaboration of the medical team is required. Future studies should establish whether reducing the risk for pneumonia in the institutionalized elderly is possible through improved oral health.

A 4-year longitudinal study of the oral prevalence of enteric gram-negative rods and yeasts in Chinese children

A 4-year longitudinal study of the oral prevalence of enteric gram-negative rods and yeasts in 116 Chinese primary school children in Hong Kong was conducted. The oral prevalence of enteric gram-negative rods for each consecutive year was 25.3%, 37.0%, 24.0% and 25.8% respectively, with a weighted mean of 27.9%. Enterobacteriaceae, which comprised 57% of all enteric gram-negative rods, were more common in children with no caries experience. The oral prevalence of yeasts for each consecutive year was 7.7%, 12.0%, 14.4% and 15.5% respectively, with a weighted mean of 12.5%. Candida albicans comprised 84% of all yeasts isolated. Oral yeast carriage was significantly associated with caries prevalence. While the oral prevalence of enteric gram-negative rods in primary school children in Hong Kong may be higher than in other parts of the world, repeated isolation of either enteric gram-negative rods or Candida spp. from individual children over the 4-year study period was rare, suggesting that carriage of these organisms is transient.

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.

The influence of incubation conditions on the adherence of oral Enterobacteriaceae to HeLa cells

The adherence of 12 oral isolates and 4 type strains of Enterobacteriaceae (equally representing Enterobacter cloacae, Klebsiella pneumoniae, Escherichia coli and Citrobacter freundii) to HeLa cell monolayers following five different incubation conditions (sucrose, D-mannose, serum, MEM and Candida albicans GDH 1957) was investigated. Incubation with sucrose and D-mannose resulted in the greatest and least adherence, respectively. The presence of preadherent C. albicans GDH 1957 on the HeLa cells tended to enhance the adherence of certain strains of E. cloacae and C. freundii, but had no overall impact on Enterobacteriaceae adherence. While heterogeneity of behaviour existed between strains within species, E. cloacae was the most, and K. pneumoniae the least, adherent species irrespective of incubation conditions. Haemagglutination assays indicated the presence of mannose-resistant type 1 fimbriae associated with all Enterobacteriaceae. In clinical terms, the variations in adherence properties observed in vitro may contribute to an understanding of the different prevalence rates of oral Enterobacteriaceae reported in the literature.

The oral prevalence of aerobic and facultatively anaerobic gram-negative rods and yeasts in semi-recluse human vegetarians

Limited data exist on the oral ecology of vegetarians. Hence the dental and periodontal status, and the oral prevalence of aerobic and facultatively anaerobic Gram-negative rods (AGNR) and yeasts, were studied in 36 semi-recluse, vegetarian, Buddhist monks and nuns in Hong Kong. The oral prevalence of AGNR and yeasts was 61.1% and 33.3%. There was no correlation between the prevalence of AGNR and/or yeasts and the incidence of carious or filled teeth and the health status of the periodontium. Rather, the results of this study combined with those of previous studies suggest that increasing age and the consumption of food prepared in communal kitchens might be more important contributory factors in the oral prevalence of AGNR than the nature of the diet itself or the health of the dentition and periodontium.