Low prevalence of multi-resistant bacteria in undergraduate dental students; an observational case-control multi-centre study in Europe.

Objective: This study assessed the prevalence of MRSA, ESBL and VRE in students from four dental schools in Europe. Methods: The hand, tongue and nostrils of the students who treated patients (study group) and who did not treat patients (control group) were sampled. After incubation in TSB and subculturing in the presence of 4 µg/ml oxacillin, positive cultures were identified for Staphylococcus aureus by Mannitol salt agar and agglutination tests. The presence of MRSA was confirmed by specific PCR on the species and on the SSCmec genes. ESBL and VRE were isolated using specific CHROMagar and confirmed using antibiotic sensitivity tests. Results: Of the 879 students who participated in this study (454 students which treated patients, 425 controls) a total of 50 students (5.7%) tested positive for a multi-drug resistant bacterium (MDRB); 13 (1.5%) students tested positive for MRSA, 26 (3.0%) for ESBL and 12 (1.4%) for VRE. No statistically significant differences were found between the students who treated patients compared to the control group for any of the MDRB and study centres, excluding MRSA carriage in the Italian student population. The use of antibiotics the year before sampling, was positively associated with the presence of an MDRB (OR 2.0; 95% Confidence Interval 1.10-3.68; p = 0.02). Conclusion: The risk for MDRB carriage and sequential transmission of MDRB for dental health care students and their patients were acceptably low.

Immediate clinical and microbiological evaluation of the effectiveness of 0.5% versus 3% sodium hypochlorite in root canal treatment: A quasi-randomized controlled trial.

AIM: To test the hypothesis that in the daily routine of a specialist clinic in endodontics that irrigation during root canal preparation with 3.0% NaOCl will result in fewer postoperative samples with cultivable bacteria than irrigation with 0.5% buffered NaOCl but, at the same time, will not result in a higher frequency of postoperative pain nor swelling. METHODOLOGY: Two hundred ninety-eight patients were enrolled in the study and were randomly assigned into two groups - 0.5% NaOCl and 3% NaOCl. All endodontic diagnoses were included. Root canal treatment was performed, and bacterial sampling was carried out prior to root filling. The patients were requested to complete a form regarding pain and swelling seven days postoperatively. Fisher's exact test, Mann-Whitney U-test, Mantel-Haenszel chi-squared and the chi-squared test with a significance level of P < 0.05 were used for statistical analysis. Multivariable logistic regression was used to adjust for confounders. RESULTS: In the 0.5% NaOCl group, 18 (13.4%) of the root canal samples were positive; in the 3% NaOCl group, the corresponding number was 24 (18.6%). The mean difference of -5.2% (95% CI: -14.8 to 4.4) was not significant (P = 0.33). In the 0.5% NaOCl group, 57 (53.8%) patients reported some pain; in the 3% group, the corresponding number was 56 (53.3%). The mean difference of 0.4 (95% CI: -14.0 to 14.8) was not significant (P = 1.0). In the 0.5% NaOCl group, 5 (5.1%) patients reported swelling; in the 3% NaOCl group, the corresponding number was 18 (17.8%). The mean difference was 12.7 (95% CI: 3.1-22.4), which was significant (P = 0.0084). CONCLUSIONS: The difference in the concentration of NaOCl (0.5% vs 3%) had no significant impact on the number of positive cultures and did not influence either the frequency or the magnitude of postoperative pain. A significantly higher incidence of postoperative swelling was recorded for patients who received a greater concentration of NaOCl (3%).

Warm perineal compresses during the second stage of labor for reducing perineal trauma: A meta-analysis.

OBJECTIVE: Perineal trauma may have a negative impact on women's lives as it has been associated with perineal pain, urinary incontinence and sexual dysfunction. The aim of this systematic review and meta-analysis of randomized controlled trials was to evaluate the effectiveness of warm compresses during the second stage of labor in reducing perineal trauma. METHODS: Electronic databases were searched from inception of each database to May 2019. Inclusion criteria were randomized trials comparing warm compresses (i.e. intervention group) with no warm compresses (i.e. control group) during the second stage of labor. Types of participants included pregnant women planning to have a spontaneous vaginal birth at term with a singleton in a cephalic presentation. The primary outcome was the incidence of intact perineum. Meta-analysis was performed using the Cochrane Collaboration methodology with results being reported as relative risk (RR) with 95% confidence interval (CI). RESULTS: Seven trials, including 2103 participants, were included in this meta-analysis. Women assigned to the intervention group received warm compresses made from clean washcloths or perineal pads immersed in warm tap water. These were held against the woman's perineum during and in between pushes in second stage. Warm compresses usually started when the baby's head began to distend the perineum or when there was active fetal descent in the second stage of labor. We found a higher rate of intact perineum in the intervention group compared to the control group (22.4% vs 15.4%; RR 1.46, 95% CI 1.22 to 1.74); a lower rate of third degree tears (1.9% vs 5.0%; RR 0.38, 95% CI 0.22 to 0.64), fourth degree tears (0.0% vs 0.9%; RR 0.11, 95% CI 0.01 to 0.86) third and fourth degree tears combined (1.9% vs 5.8%; RR 0.34, 95% CI 0.20 to 0.56) and episiotomy (10.4% vs 17.1%; RR 0.61, 95% CI 0.51 to 0.74). CONCLUSION: Warm compresses applied during the second stage of labor increase the incidence of intact perineum and lower the risk of episiotomy and severe perineal trauma.

Salivary microbial profiles in 5-year old children with oral clefts: a comparative study.

AIM: To compare the salivary microbial profile in children with oral clefts to matched non-cleft controls in a cross-sectional study. METHODS: The cleft group consisted of 80 children aged 5 years and 144 age-matched non-cleft children were recruited as a control group. Stimulated whole saliva samples were collected and analysed with checkerboard DNA-DNA hybridisation using 12 pre-determined bacterial probes. Background data on caries, oral hygiene, dietary habits and fluoride exposure were collected from clinical examinations and questionnaires. RESULTS: Children in the cleft group had a significantly higher prevalence of dental caries but only minor differences in the salivary microbial profile were found. In general, the cleft-children displayed a lower prevalence of common commensal species (e.g. Streptococcus, Fusobacterium) when compared with the non-cleft controls. The differences were statistically significant (p < 0.05) but the clinical significance was unclear. CONCLUSIONS: The profile of the salivary microflora in 5-year-old children with and without oral clefts was basically similar and displayed only marginal differences with respect to commensal bacteria.

Low antibiotic resistance among anaerobic Gram-negative bacteria in periodontitis 5 years following metronidazole therapy.

The objective of this study was to assess antibiotic susceptibility among predominant Gram-negative anaerobic bacteria isolated from periodontitis patients who 5 years prior had been subject to mechanical therapy with or without adjunctive metronidazole. One pooled sample was taken from the 5 deepest sites of each of 161 patients that completed the 5 year follow-up after therapy. The samples were analyzed by culture. A total number of 85 anaerobic strains were isolated from the predominant subgingival flora of 65/161 patient samples, identified, and tested for antibiotic susceptibility by MIC determination. E-tests against metronidazole, penicillin, amoxicillin, amoxicillin + clavulanic acid and clindamycin were employed. The 73/85 strains were Gram-negative rods (21 Porphyromonas spp., 22 Prevotella/Bacteroides spp., 23 Fusobacterium/Filifactor spp., 3 Campylobacter spp. and 4 Tannerella forsythia). These were all isolated from the treated patients irrespective of therapy procedures (+/-metronidazole) 5 years prior. Three strains (Bifidobacterium spp., Propionibacterium propionicum, Parvimonas micra) showed MIC values for metronidazole over the European Committee on Antimicrobial Susceptibility Testing break point of >4 µg/mL. All Porphyromonas and Tannerella strains were highly susceptible. Metronidazole resistant Gram-negative strains were not found, while a few showed resistance against beta-lactam antibiotics. In this population of 161 patients who had been subject to mechanical periodontal therapy with or without adjunct metronidazole 5 years prior, no cultivable antibiotic resistant anaerobes were found in the predominant subgingival microbiota.

Site-specific dental plaque pH in 13-year-old Thai schoolchildren.

OBJECTIVE: The aim of this paper was to study pH conditions between dental sites, taking account the presence of caries, calculus, and microbial composition and alkali production. MATERIALS AND METHODS: One hundred 13-year-old Thai schoolchildren were recorded for caries experience (DMFT, DT), calculus, plaque, and gingivitis. Ex vivo urease activity was measured on 11, 26, 31, and 46 (distal aspect) with the rapid urease test and pH at baseline and after rinse with 0.25 % urea solution on mesial site in vivo. Interproximal plaque from contralateral teeth was microbiological analysed with the checkerboard technique. RESULTS: Thirty-four children were caries free. Plaque and calculus were abundant; all children showed a high resting plaque pH and the mandibular incisor showed significantly (p < 0.01) higher pH at baseline, max pH and AOC7.0 after urea challenge, ex vivo urease activity and calculus but lower caries experience than other teeth. A significant inverse correlation (p < 0.02) was found between caries frequency and ex vivo urease activity for tooth 11. Anaerobes predominated over streptococci, but no significant differences between dental sites were found. CONCLUSIONS: The study group had a high baseline plaque pH, in vivo and ex vivo urease activity, and calculus but low caries experience, which was best reflected in the lower incisor region. CLINICAL RELEVANCE: Urease activity and pH on site level may be important determinants for individuals at caries risk.

Methodological issues in the quantification of subgingival microorganisms using the checkerboard technique.

The reproducibility and reliability of quantitative microbiological assessments using the DNA-DNA hybridization "checkerboard method" (CKB) were assessed. The data originated from 180 chronic periodontitis patients, who were enrolled in a clinical trial and sampled at baseline, and 3 and 12m post-therapy. The samples were divided into two portions allowing evaluation of reproducibility. In total, 531 samples were analyzed in a first run, using standard bacterial preparations of cells and 513 samples were accessible for analysis in the second, using standards based on purified DNA from the species. The microbial probe panel consisted of periodontitis marker bacteria as well as non-oral microorganisms. Three different ways of quantifying and presenting data; the visual scoring method, VSM, the standard curve method, SCM, and the percent method, PM, were compared. The second set of analyses based on the use of standard preparations of pure DNA was shown to be more consistent than the first set using standards based on cells, while the effect of storage time per se up to 2.5y seemed to be marginal. The best reproducibility was found for Tannerella forsythia, irrespective of quantification technique (Spearman's rho=0.587, Pearson's r≥0.540). The percent method (PM) based on percent of High Standard (10(6) cells) was more reliable than SCM based on a linear calibration of the High Standard and a Low Standard (10(5) cells). It was concluded that the reproducibility of the CBK method varied between different bacteria. High quality and pure specific DNA whole genomic probes and standards may have a stronger impact on the precision of the data than storage time and conditions.

Hydrogen sulfide production from subgingival plaque samples.

Periodontitis is a polymicrobial anaerobe infection. Little is known about the dysbiotic microbiota and the role of bacterial metabolites in the disease process. It is suggested that the production of certain waste products in the proteolytic metabolism may work as markers for disease severity. Hydrogen sulfide (H2S) is a gas produced by degradation of proteins in the subgingival pocket. It is highly toxic and believed to have pro-inflammatory properties. We aimed to study H2S production from subgingival plaque samples in relation to disease severity in subjects with natural development of the disease, using a colorimetric method based on bismuth precipitation. In remote areas of northern Thailand, adults with poor oral hygiene habits and a natural development of periodontal disease were examined for their oral health status. H2S production was measured with the bismuth method and subgingival plaque samples were analyzed for the presence of 20 bacterial species with the checkerboard DNA-DNA hybridization technique. In total, 43 subjects were examined (age 40-60 years, mean PI 95 ± 6.6%). Fifty-six percent had moderate periodontal breakdown (CAL > 3 < 7 mm) and 35% had severe periodontal breakdown (CAL > 7 mm) on at least one site. Parvimonas micra, Filifactor alocis, Porphyromonas endodontalis and Fusobacterium nucleatum were frequently detected. H2S production could not be correlated to periodontal disease severity (PPD or CAL at sampled sites) or to a specific bacterial composition. Site 21 had statistically lower production of H2S (p = 0.02) compared to 16 and 46. Betel nut chewers had statistically significant lower H2S production (p = 0.01) than non-chewers. Rapid detection and estimation of subgingival H2S production capacity was easily and reliably tested by the colorimetric bismuth sulfide precipitation method. H2S may be a valuable clinical marker for degradation of proteins in the subgingival pocket.

Caries risk assessment. A systematic review.

OBJECTIVE: To assess the ability of multivariate models and single factors to correctly identify future caries development in pre-school children and schoolchildren/adolescents. STUDY DESIGN: A systematic literature search for relevant papers was conducted with pre-determined inclusion criteria. Abstracts and full-text articles were assessed independently by two reviewers. The quality of studies was graded according to the QUADAS tool. The quality of evidence of models and single predictors was assessed using the GRADE approach. RESULTS: Ninety original articles fulfilled the inclusion criteria. Seven studies had high quality, 35 moderate and the rest poor quality. The accuracy of multivariate models was higher for pre-school children than for schoolchildren/adolescents. However, the models had seldom been validated in independent populations, making their accuracy uncertain. Of the single predictors, baseline caries experience had moderate/good accuracy in pre-school children and limited accuracy in schoolchildren/adolescents. The period of highest risk for caries incidence in permanent teeth was the first few years after tooth eruption. In general, the quality of evidence was limited. CONCLUSIONS: Multivariate models and baseline caries prevalence performed better in pre-school children than in schoolchildren/adolescents. Baseline caries prevalence was the most accurate single predictor in all age groups. The heterogeneity of populations, models, outcome criteria, measures and reporting hampered the synthesis of results. There is a great need to standardize study design, outcome measures and reporting of data in studies on caries risk assessment. The accuracy of prediction models should be validated in at least one independent population.

Bacterial flora of the human oral cavity, and the upper and lower esophagus.

This reference study aims to survey the bacterial flora of the healthy lower human esophagus and to compare it with that of the upper esophagus and oral mucosa. The use of biopsies, in addition to brush samples, allows inclusion of not only transient bacteria present on the surface but also bacteria residing in the epithelia, and the yield of the two methods can be compared. Forty patients scheduled for surgery for reasons with no known influence on esophageal flora and with no symptoms or endoscopic signs of esophageal disease were included. Samples were collected from the oral, upper esophageal, and lower esophageal mucosa using sealed brushes and biopsy forceps. Colonies cultivated on agar plates were classified and semiquantified. Twenty-three different bacterial species were identified, with similar strains present at the three sites. The most common group of bacteria was viridans streptococci, with an occurrence rate in brush samples and biopsies of 98% and 95%, respectively. The median number of species occurring in the oral cavity, upper esophagus, and lower esophagus was between 3 and 4 (range 0-7). The total number of species in the oral cavity was significantly higher when compared with either level in the esophagus, while the yields obtained by brush and biopsy sampling were highly correlated. Hence, the normal human esophagus is colonized with a resident bacterial flora of its own, which has similarities to that of the oral mucosa. There are diverse species that make up this flora, although in relatively low amounts. The most frequent inhabitants of the esophagus are streptococci, with an occurrence rate in brush samples and biopsies of 95-98%. Comparative studies of patients with eosinophilic esophagitis and gastroesophageal reflux disease are warranted.

Probiotic supplements (Lactobacillus reuteri DSM 17938 and ATCC PTA 5289) do not affect regrowth of mutans streptococci after full-mouth disinfection with chlorhexidine: a randomized controlled multicenter trial.

The aim of this study was to investigate the effectiveness of tablets containing two probiotic Lactobacillus reuteri strains in inhibiting regrowth of salivary mutans streptococci (MS) after full-mouth disinfection (FMD) with chlorhexidine. The null hypothesis was that the levels of MS would not differ in comparison with a placebo protocol. The study population was comprised of 62 young adults (mean age 23 years) with moderate or high counts of salivary MS who volunteered after informed consent. The study was a double-blinded randomized controlled trial with two parallel groups. After a 3-day chlorhexidine regimen, the subjects were randomly assigned to a test group (n = 32) with probiotic lozenges (2/day) or a placebo group (n = 30). The intervention period was 6 weeks, and stimulated whole saliva was collected at baseline and after 1, 6, and 12 weeks. The samples were processed for MS by a chair-side test and DNA-DNA hybridization as an estimate of 19 bacterial strains associated with oral health and disease. There was no significant difference between the groups at inclusion, and FMD reduced the salivary MS levels significantly in both groups. The MS suppression lasted less than 6 weeks and there were no statistical differences in salivary MS regrowth between the test and control groups at any of the follow-ups. Likewise, there were no major differences in the regrowth patterns of the checkerboard panel between the two groups. We conclude that daily oral administration of L. reuteri did not seem to affect or delay the regrowth of salivary MS after FMD with chlorhexidine.

Acupuncture as a therapeutic treatment option for threatened miscarriage.

BACKGROUND: Threatened miscarriage involves vaginal bleeding in a pregnancy that remains viable. This is a common early pregnancy complication with increased risk factors for early pregnancy loss, preterm premature rupture of membranes (PPROM), preterm delivery, low birth weight babies and maternal antepartum haemorrhage. Currently there are no recommended medical treatment options, rather women receive advice that centres on a 'wait and see' approach. For women with a history of unexplained recurrent miscarriage providing supportive care in a subsequent pregnancy improves live birthing outcomes, but the provision of supportive care to women experiencing threatened miscarriage has to date not been examined. DISCUSSION: While it is known that 50-70% of miscarriages occur due to chromosomal abnormalities, the potential for therapeutic intervention amongst the remaining percentage of women remains unknown. Complementary and alternative medicine (CAM) therapies have the potential to provide supportive care for women presenting with threatened miscarriage. Within fertility research, acupuncture demonstrates beneficial hormonal responses with decreased miscarriage rates, raising the possibility acupuncture may promote specific beneficial effects in early pregnancy. With the lack of current medical options for women presenting with threatened miscarriage it is timely to examine the possible treatment benefits of providing CAM therapies such as acupuncture. SUMMARY: Despite vaginal bleeding being a common complication of early pregnancy there is often reluctance from practitioners to discuss with women and medical personal how and why CAM may be beneficial. In this debate article, the physiological processes of early pregnancy together with the concept of providing supportive care and acupuncture are examined. The aim is to raise awareness and promote discussion as to the beneficial role CAM may have for women presenting with threatened miscarriage.

Predominant bacterial species in subgingival plaque in dogs.

BACKGROUND AND OBJECTIVE: The dog has been used extensively for experimental and microbiological studies on periodontitis and peri-implantitis without detailed knowledge about the predominant flora of the subgingival plaque. This study was designed to evaluate the predominant cultivable bacterial species in dogs and compare them phenotypically and genotypically with corresponding human species. MATERIAL AND METHODS: Four subgingival samples were taken from two upper premolars in each of six Labrador retrievers. The samples from each dog were processed for anaerobic culture. From the samples of each dog, the five or six predominating bacteria based on colony morphology were selected and pure cultured. Each of the strains was characterized by Gram stain, anaerobic/aerobic growth and API-ZYM test. Eighteen strains showing clear-cut phenotypic differences were further classified based on DNA sequencing technology. Cross-reactions of DNA probes from human and dog strains were also tested against a panel of both human and dog bacterial species. RESULTS: Thirty-one strains in the dogs were isolated and characterized. They represented 21 different species, of which six belonged to the genus Porphyromonas. No species was found consistently in the predominant flora of all six dogs. Porphyromonas crevioricanis and Fusobacterium canifelinum were the two most prevalent species in predominant flora in dogs. DNA probes from human and dog species cross-reacted to some extent with related strains from humans and dogs; however, distinct exceptions were found. CONCLUSION: The predominant cultural subgingival flora in dogs shows great similarities with the subgingival bacteria from humans at the genus level, but distinct differences at the species level; however, a genetic relatedness could be disclosed for most strains investigated.

Clinical and microbiological characteristics of peri-implantitis cases: a retrospective multicentre study.

OBJECTIVES: The aim of this study was to follow patient cases retrospectively in a longitudinal manner from the time of implant placement to the time they were diagnosed with peri-implant disease, and to identify associated clinical and microbiological features of peri-implant disease. MATERIAL AND METHODS: A total of 281 patient cases were chosen from the archives of the Oral Microbiological Diagnostic Laboratory, Gothenburg, Sweden, based on bacterial samples taken from diseased implants. A form was designed and filled in separately for each case including data on patient, implant and disease profile. RESULTS: Most cases were severe peri-implantitis cases (91.4%). In 41.3% of the patients, peri-implantitis was developed early, already after having implants in function less than 4 years. The type of implant surface was significantly associated with the time in years implants were in function, before disease was developed (P < 0.05). The microbiological results by both culture and checkerboard analysis, although failed to fully correspond to the severity of the disease in terms of magnitude, proved to show that peri-implantitis is a polymicrobial anaerobic infection with increased number of AGNB (aerobic Gram-negative bacilli) in 18.6% of the patients. CONCLUSIONS: Peri-implantitis is a biological complication of implants in function that poses a threat to their long-term survival. It may develop earlier around implants with rough surfaces and it may represent a true infection. Microbiological sampling methods should be improved and uniformed so as to fully unveil the microbiological profile of the disease.

Inhibitory effect of oral Lactobacillus against oral pathogens.

AIMS: To determine the inhibitory effect of oral Lactobacillus against putative oral pathogens. METHODS AND RESULTS: Total 357 strains comprising 10 species of oral Lactobacillus, Lactobacillus fermentum (195), Lactobacillus salivarius (53), Lactobacillus casei (20), Lactobacillus gasseri (18), Lactobacillus rhamnosus (14), Lactobacillus paracasei (12), Lactobacillus mucosae (12), Lactobacillus oris (12), Lactobacillus plantarum (11) and Lactobacillus vaginalis (10) were used as producer strains. Inhibitory effect against a panel of indicators, periodontitis- and caries-related pathogens, was assessed. Most oral Lactobacillus was able to inhibit the growth of both periodontitis- and caries-related pathogens. The strongest inhibitory activity was associated with Lact. paracasei, Lact. plantarum, Lact. rhamnosus, Lact. casei and Lact. salivarius. Lactobacillus SD1-SD6, representing the six species with the strong inhibitory effect, inhibited growth of Streptococcus mutans ATCC 25175 in the biofilm model. Also, it was demonstrated that growth of Strep. mutans was inhibited in a mixture with Lact. paracasei SD1. The inhibition was enhanced in acidic condition and 5% glucose. CONCLUSIONS: The results have shown that oral Lactobacillus SD1-SD6 showed a strong inhibitory effect against Strep. mutans and Streptococcus sobrinus, as well as, Gram-negative periodontal pathogens Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans. SIGNIFICANCE AND IMPACT OF THE STUDY: The results indicated that Lactobacillus may be of benefit as probiotics for the prevention of oral diseases.

Metal-ion susceptibility of oral bacterial species.

AIMS: This study aimed to evaluate the effect of lead (Pb) on growth of bacterial species related to dental diseases in vitro. METHODS AND RESULTS: The effects of lead acetate on representative species of the oral flora were examined at 0.1-10 mmol l(-1) and compared with the effect of silver nitrate and ferrous sulfate. The minimal inhibitory concentration of lead acetate was between 0.15 and 5 mmol l(-1) for the bacterial strains tested. The minimal bactericidal concentration of lead acetate for most oral species was detected in the range of 5-10 mmol l(-1). Silver nitrate at a concentration of 1.25 mmol l(-1) was sufficient to exhibit antibacterial activity against almost all bacteria tested. Ferrous sulfate had the lowest effect. CONCLUSIONS: The study indicated a general antimicrobial effect of lead on oral bacterial species in the range of 0.15-10 mmol l(-1). The toxicity of silver nitrate was the highest, whereas that of ferrous sulfate was the lowest. Gram-positive species had a tendency to be less susceptible for metals than Gram-negatives. SIGNIFICANCE AND IMPACT OF THE STUDY: The study shows that it is possible that microbiological changes may occur in the dental plaque in children because of toxic exposure of environmental lead.

Lactobacillus species and genotypes associated with dental caries in Thai preschool children.

Lactobacilli have been associated with the presence and progression of dental caries. Nevertheless, the relation between certain species or genotypes of Lactobacillus and caries is unclear and there are no data available for the Thai population. This study aimed to examine the distribution of species and genotypes of oral Lactobacillus among children with rather high caries prevalence, and to investigate whether certain species or genotypes were more related to caries activity than others. One hundred and sixty-five children were examined for caries status. Saliva samples were collected and the numbers of lactobacilli were counted. A total of 357 Lactobacillus isolates from 59 children were identified to species level by 16S ribosomal RNA genes polymerase chain reaction (PCR) -restriction fragment length polymorphism and 16S ribosomal RNA gene sequencing. Furthermore, 304 isolates from 56 children were genotyped using arbitrarily primed PCR. Significant correlation was found between levels of lactobacilli and dental caries (P < 0.001). Among the 10 identified species of Lactobacillus, L. salivarius was more prevalent in children with moderate to high caries prevalence compared with children with low caries prevalence, while L. fermentum was the most predominant species in all study groups. Moreover, a genetic heterogeneity of Lactobacillus species was found among the children and those with high caries prevalence tended to be colonized with more than one clonal type. In summary, L. salivarius may be a putative caries pathogen among preschool Thai children.

Lactobacillus and Bifidobacterium species do not secrete protease that cleaves the MUC2 mucin which organises the colon mucus.

The colon epithelium is covered by two layers of mucus built around the MUC2 mucin. An inner dense and attached mucus layer does not allow bacteria to penetrate, thus keeping the epithelial cell surface free from bacteria. An outer loose mucus layer is the habitat for the commensal bacterial microbiota. The inner mucus layer is renewed from the epithelial side and gets converted into the outer layer due to proteolytic cleavages by host proteases. We have now analysed if potential probiotic bacteria, namely Lactobacillus brevis, Lactobacillus plantarum, Lactobacillus bulgaricus and Bifidobacterium lactis, can secrete protease that cleaves the MUC2 mucin. We found that none of the potential probiotic bacteria Lactobacillus and Bifidobacterium could cleave the MUC2 core protein in the form of recombinant MUC2 N and C-termini although they secreted active proteases. This was in contrast to crude mixtures of oral and faecal bacteria that cleaved the MUC2 mucin. This observation further supports the view that these potential probiotic bacteria are of no harm to the host, as these bacteria cannot disrupt the mucin organised mucus as long as they are covered by glycans.

Oral Lactobacillus species in type 2 diabetic patients living in southern Thailand.

Although lactobacilli are part of normal oral, gastrointestinal and genitourinary flora, they are an uncommon cause of infections in human. Lactobacillus-associated infections have generally occurred in patients with serious underlying conditions e.g. diabetes and cancer that might favour certain microorganisms. The aim of this study was to characterize species and genotypes of lactobacilli isolated from diabetic patients and non-diabetic subjects. One hundred and five type 2 diabetic patients and 103 non-diabetic subjects were recruited in this study. A total of 170 isolates of Lactobacillus were identified using 16S rRNA gene PCR-RFLP and genotyping were performed using AP-PCR by ERIC primers. It was found that type 2 diabetic patients had a significantly higher prevalence (p = 0.008) and level of lactobacilli than non-diabetic controls (p = 0.030). The most frequently isolated Lactobacillus spp. were L. casei/paracasei and L. fermentum in both the diabetic and non-diabetic groups. Strains of L. casei/paracasei and L. fermentum from between and within individuals were genotyped, and the genotyping of Lactobacillus strains showed diversity between individuals. One up to three genotypes of these two species could be found in the same subject. Interestingly, fewer genotypes were found in the diabetic patients than in the non-diabetic subjects.