In vitro evaluation of yoghurt starter lactobacilli and Lactobacillus rhamnosus GG adhesion to saliva-coated surfaces

Aim:  The aim of the study was to evaluate the adhesion of Lactobacillus delbrueckii subsp . bulgaricus and Lactobacillus rhamnosus strain GG to saliva-coated surfaces in vitro .
Methods:  Fifteen radiolabeled dairy L. delbrueckii subsp . bulgaricus strains and L. rhamnosus GG were tested for their ability to adhere to saliva-coated hydroxyapatite beads and polystyrene microtiter plates and the radioactivity was measured by liquid scintillation counter. The effects of lysozyme on the adhesion of lactobacilli and of pretreatment with lactobacilli on the adhesion of Streptococcus sanguinis were also assessed.
Results:  All strains tested adhered to saliva-coated surfaces but with significantly different binding frequencies. The adhesion of the L. delbrueckii subsp . bulgaricus strains remained lower in comparison to L. rhamnosus strain GG. One L. delbrueckii subsp . bulgaricus strain showed binding frequency comparable to S. sanguinis . Lysozyme pretreatment of the samples significantly increased lactobacillus adhesion to saliva-coated surfaces.
Conclusion:  The present results showed significant variations in the adhesion capacity of the Lactobacillus strains studied. Adhesion to oral surfaces is of primary importance for bacterial colonization in the mouth. Only one of the L. delbrueckii subsp . bulgaricus dairy starter culture strains investigated had a high adhesion percentage. This strain might then be considered for further investigations in the oral environment.     

口腔生物膜动态研究模型的建立和应用评价

目的:模拟口腔菌斑生态环境,建立能够对生物膜形成过程连续观察的动态研究模型.方法:自制发酵罐和多出口连续培养室.以变形链球菌、血链球菌、乳酸杆菌、内氏放线菌为实验菌株,将羟磷灰石片、玻片等置于连续培养室中,通过调节温度、氧分压、pH值、清除率、循环流速及代谢底物等参数建立模型.以25 mM蔗糖和蒸馏水进行系统测试.观察系统中实验菌CFU计数、pH动态变化等各项反应及不同环境下所形成生物膜的微结构变化.所得数据采用SPSS 10.0软件包进行统计学分析,选用单因素方差分析的Dunnet t双侧检验.在α=0.05的情况下比较蔗糖加入组与对照组之间的差异.结果:随着蔗糖的给予,连续培养室中pH表现出相似于天然口腔的致龋环境,蒸馏水组pH值始终维持在7.5左右.而蔗糖组pH值呈明显的周期性波动,最低在4.5以下,但4～5h后,其pH值仍能逐步恢复到6.5左右.观察到细菌计数、生物膜形态的时间依赖性.随着处理液的加入.2组生物膜的活菌计数均明显增加,约72h趋于稳定.对120h生物膜,蔗糖组变形链球菌、乳酸杆菌的细菌计数显著高于蒸馏水组(P＜0.05);蔗糖组变形链球菌计数最高,而蒸馏水组血链球菌计数最高.荧光显微镜观察发现.蔗糖组大量的胞外多糖基质和细菌成团、成片分布;蒸馏水组虽然也存在细菌和基质增多的时间依赖性.但膜细菌基质团块仍清晰可见.结论:本研究建立的体外模型能稳定控制有关参数,各观察指标均具有良好的重复性.模型的建立,实现了生物膜形成过程的动态观察.     

Surface properties of lactobacilli isolated from healthy subjects

OBJECTIVE: Lactobacilli are considered cariogenic micro-organisms. As oral species of lactobacilli have not been thoroughly described, the aim of this work was to isolated and identify these organisms from teeth, tongue, saliva and gum of healthy patients and to describe some of their surface properties. SUBJECTS: Forty-four subjects from Tucumán, Argentina, with D, d and M, m indices equal to 0. MATERIALS AND METHODS: Samples were obtained from different areas of the oral cavity. Microorganisms were cultured in lactobacilli selected media (LBS) and identified morphologically and biochemically. Hydrophobicity was analysed by partition in organic solvents, acidity by affinity with chloroform and basicity with ethyl acetate (MATH method), aggregation and coaggregation in presence of (NH4)2SO4, and haemagglutination with ABO erythrocytes in microplates. RESULTS: Eighty-five lactobacilli were isolated; 29.4% were homofermenter, 44.7% facultative heterofermenter and 25.9% obligate heterofermenter. Predominant species were L. fermentum, L. plantarum, L. salivarius, and L. rhamnosus. Most of the strains showed moderate to high hydrophobicity and demonstrated high acid and basic surface charges with almost 40% showing salt aggregation. Few strains haemagglutinated. CONCLUSIONS: A variety of Lactobacillus species were isolated from healthy mouths, some of whom showed adhesion-related properties such as high hydrophobicity and charged surfaces. Probable mechanisms related to the ecological behaviour of lactobacilli in the oral cavity are discussed.     

Characterization of oral lactobacilli as potential probiotics for oral health

INTRODUCTION: Intestinal lactobacilli have been successfully used as probiotics to treat gastrointestinal disorders, but only limited data are available for the probiotic properties of oral lactobacilli to combat oral diseases. We aimed to characterize oral lactobacilli for their potential probiotic properties according to the international guidelines for the evaluation of probiotics, and to select potential probiotic strains for oral health. METHODS: The study included 67 salivary and subgingival lactobacilli of 10 species, isolated from healthy humans. All strains were identified using amplified ribosomal DNA restriction analysis, tested for antimicrobial activity against oral pathogens, tolerance of low pH and bile content. Thereafter, the lysozyme tolerance and antibiotic susceptibility of 22 potential probiotic strains were assessed. RESULTS: The majority of strains suppressed the growth of Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, and Streptococcus mutans, but none inhibited Candida albicans. The lowest pH tolerated by lactobacilli following 4 h of incubation was pH 2.5, but none of the strains grew at this pH. All strains tolerated a high concentration of lysozyme (10 mg/ml) and half of the strains tolerated a high concentration of human bile [5% volume/volume (V/V)]. Four Lactobacillus plantarum and two Lactobacillus oris strains expressed resistance to tetracycline and/or doxycycline. CONCLUSIONS: Strains of L. plantarum, Lactobacillus paracasei, Lactobacillus salivarius, and Lactobacillus rhamnosus expressed both high antimicrobial activity and high tolerance of environmental stress. The absence of transferable antibiotic-resistance genes in L. plantarum strains remains to be confirmed. These results suggest a potential for oral lactobacilli to be used as probiotics for oral health.     

Use of polymerase chain reaction techniques and sodium dodecyl sulfate-polyacrylamide gel electrophoresis for differentiation of oral Lactobacillus species

BACKGROUND/AIMS: The genus Lactobacillus has been associated with dental caries in humans, although it is seldom speciated due to lack of simple and nonlaborious identification methods. A considerable heterogeneity among Lactobacillus species has been demonstrated. The purpose of this study was to develop simple methods combining restriction fragment length polymorphism analysis of polymerase chain reaction (PCR)-amplified 16S rRNA (16S rRNA gene PCR-RFLP) and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) for the identification of 13 reference strains of Lactobacillus. METHODS: The 16S rRNA gene sequences were amplified by PCR using universal primers and digestion of PCR products with the restriction endonucleases, HpaII and HaeIII. The 16S rRNA gene PCR-RFLP is reproducible and has been proved to be useful for differentiating Lactobacillus strains to species level. Seventy-seven Lactobacillus isolates from a Thai population were used to show the applicability of the identification test. RESULTS: PCR-RFLP alone had limitations, because the RFLP patterns of Lactobacillus casei and Lactobacillus rhamnosus and of Lactobacillus acidophilus and Lactobacillus crispatus showed similar patterns; however, these could be differentiated by SDS-PAGE. Of the 77 isolates, 38 were identified as Lactobacillus fermentum, 25 as L. rhamnosus, 5 as Lactobacillus salivarius, 5 as L. casei, 3 as L. acidophilus and 1 as Lactobacillus plantarum. CONCLUSION: 16S rRNA gene PCR-RFLP, using HpaII and HaeIII, together with SDS-PAGE protein profiles could be an alternative method for the identification of oral Lactobacillus strains to species level, and may be applicable for large-scale studies on the association of Lactobacillus to dental caries.     

Oral lactobacilli in chronic periodontitis and periodontal health: species composition and antimicrobial activity

BACKGROUND/AIMS: Lactobacilli are known to play an important role in the maintenance of health by stimulating natural immunity and contributing to the balance of microflora. However, their role in chronic periodontitis is unclear. We aimed to identify oral lactobacilli in chronic periodontitis and periodontally healthy subjects, and to determine their antimicrobial activity against putative oral pathogens. METHODS: A total of 238 Lactobacillus isolates from the saliva and subgingival sites of 20 chronic periodontitis and 15 healthy subjects were collected. In all, 115 strains were identified using rapid amplified ribosomal DNA restriction analysis. Antimicrobial activity against Streptococcus mutans, Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, and Prevotella intermedia was assessed. RESULTS: Lactobacilli belonging to 10 species were identified. The most prevalent strains in healthy persons were Lactobacillus gasseri and Lactobacillus fermentum and in chronic periodontitis patients, Lactobacillus plantarum. Obligately homofermentatives, particularly L. gasseri, were less prevalent in chronic periodontitis patients compared with healthy subjects (8% vs. 64% for L. gasseri, P < 0.01). Sixty-nine percent of tested lactobacilli inhibited S. mutans, 88% A. actinomycetemcomitans, 82% P. gingivalis and 65% P. intermedia. The strongest antimicrobial activity was associated with Lactobacillus paracasei, L. plantarum, Lactobacillus rhamnosus, and Lactobacillus salivarius. The strains from periodontally healthy patients showed a lower antimicrobial activity against S. mutans than the strains from chronic periodontitis patients. CONCLUSION: The composition of oral lactoflora in chronic periodontitis and healthy subjects differs, with a higher prevalence of homofermentative lactobacilli, particularly L. gasseri, in the latter group. Both homo- and heterofermentative oral lactobacilli suppress the growth of periodontal pathogens, but the antimicrobial properties are strain, species and origin specific.     

Treatment with probiotics in experimental oral colonization by Candida albicans in murine model (DBA/2)

The aim of this study is to evaluate the oral colonization by Candida albicans in experimental murine immunosuppressed DBA/2 and treatment with probiotic bacteria. To achieve these objectives, 152 DBA/2-immunosuppressed mice were orally inoculated with a suspension of C. albicans containing 10(8) viable yeast cells, the animals were treated with nystatin or with the probiotics (Lactobacillus acidophilus and Lactobacillus rhamnosus). Evaluations were performed by Candida count from oral mucosa swabbing. The oral mucosa colonization by C. albicans started at day 1 after inoculation, remained maximal from day 3 until day 7, and then decreased significantly. Probiotics reduced the C. albicans colonization significantly on the oral mucosa in comparison with the untreated animal group. In the group treated with L. rhamnosus, the reduction in yeast colonization was significantly higher compared with that of the group receiving nystatin. Immunosuppressed animal model DBA/2 is a relevant model for experimental Candida oral colonization, and the treatment with probiotics in this model may be an effective alternative to prevent it.     

婴儿口腔早期定植菌群的一年动态观察

目的　观察婴儿口腔早期定植细菌的动态变化。方法　收集12例健康新生儿出生后第1天和1、3、6、9、 12个月的口腔样本,选择适当稀释度接种于BA、MSA、BHI培养基,经需氧、微需氧及厌氧条件培养后行细菌形态学及生化鉴定。结果　婴儿口腔中检出率最高的细菌为S.salivarius,其次为S.mitis;乳牙萌出后S.sanguis,S.gordo- nii和S.mutans有一定的检出;Veillonella spp.在出生后1月的新生儿口腔即有一定的检出,A.odontolyticus在3个月时开始有8.3%的检出;L.acidophilus在婴儿口腔一直维持在较低的检出水平;少数有部分乳牙萌出的婴儿口腔中检出L.buccalis与Capnocytophaga spp.的存在。结论　S.salivarius与S.mitis是新生儿及婴儿口腔的优势细菌,Veil- lonella是最早、最常检出的厌氧菌,A.odontolyticus是最早检出的放线菌,随着婴儿月龄的增加,其口腔中检出细菌的种类和数量均明显增加。     

同一口腔中c血清型变形链球菌高、低毒力株的筛选

目的：由同一高龋者口腔中分离出c血清型变形链球菌高致龋毒力的菌株和低致龋毒力的菌株，为变形链球菌的比较基因组研究奠定基础。方法：从4个方面比较24株c血清型变形链球菌临床分离株对唾液包被羟基磷灰石的黏附能力、产酸和耐酸能力以及合成胞外多糖的能力。结果：筛选出位于同一口腔中的高、低毒力株。结论：同一口腔中存在着2株或2株以上致龋能力不同的c血清型变形链球菌。     

Biofilm growth of Lactobacillus species is promoted by Actinomyces species and Streptococcus mutans

The ability of oral bacteria to integrate within a biofilm is pivotal to their survival. A dependence on the amount of biofilm growth by noncoaggregating Lactobacillus rhamnosus and Lactobacillus plantarum on coculture with Actinomyces naeslundii, Actinomyces gerencseriae, Streptococcus mutans and Veillonella parvula was investigated using an artificial-mouth culture system. Biofilm formation by the lactobacilli in mono-culture was poor. In coculture with Actinomyces species the amount of L. rhamnosus increased 7-20 times and L. plantarum 4-7 times compared to its mono-culture biofilm. S. mutans also promoted substantial biofilm growth of lactobacilli but V. parvula had no effect. We conclude that these Actinomyces species promoted growth of key Lactobacillus species in a biofilm, as did S. mutans to a smaller extent, and that the ability of individual bacteria to form mono-culture biofilms is not necessarily an indicator of their survival and pathogenic potential in a complex multispecies biofilm community.     

Colonization of Lactobacillus rhamnosus GG in the oral cavity

BACKGROUND/AIMS: Lactobacillus rhamnosus GG (LGG) is one of the most widely studied probiotic bacterial strain. The benefits of LGG treatment in gastrointestinal disorders are well documented. The aim of the present study was to investigate whether LGG can be detected in the oral cavity after discontinuation of administration of a product prepared with this bacterium. MATERIAL AND METHODS: 56 volunteers consumed Gefilus juice (Valio Ltd, Helsinki, Finland) containing LGG during a 14-day trial period. Saliva samples were collected and cultured onto MRS agar after a clearance period and then daily after a 2-week intervention period for as long as LGG was found. LGG-like colonies were analyzed in saliva samples, identified by characteristic colony morphology, a lactose fermentation test, and PCR with specific primers. RESULTS: LGG was not able to colonize the oral cavity. It could only be temporarily detected. In one female subject, however, whose medical history revealed use of LGG in childhood, the bacterium was detected in all saliva samples taken up to 5 months. (She was excluded from the intervention trial). CONCLUSION: Permanent colonization of LGG in the oral cavity is improbable but seems possible in individual cases.     

Molecular and biochemical characterizations of human oral lactobacilli as putative probiotic candidates

INTRODUCTION: The objective of this study was to characterize the lactobacilli from the human oral cavity as a potential source of probiotic strains. METHODS: Samples were collected from four different locations within the oral cavity: surface of healthy tooth, oral mucous membrane, surface of tooth decay and deep tooth decay. On the basis of morphological and biochemical properties eight categories were formed and 26 isolates were selected for further characterization. The isolates were determined as Lactobacillus sp. using primers specific for 16S rDNA. Sequencing of 16S rDNA genes and repetitive sequence-based polymerase chain reactions were used for determination to species and subspecies levels. RESULTS: Predominant species were Lactobacillus fermentum, Lactobacillus plantarum, Lactobacillus salivarius and Lactobacillus paracasei subsp. paracasei, while Lactobacillus acidophilus, Lactobacillus cellobiosus, Lactobacillus delbrueckii subsp. lactis and Lactobacillus gasseri were also present. The isolates Lactobacillus salivarius BGHO1, Lactobacillus fermentum BGHO36 and BGHO64, Lactobacillus gasseri BGHO89 and Lactobacillus delbrueckii subsp. lactis BGHO99 exhibited antagonistic action on the growth of Staphylococcus aureus, Enterococcus faecalis, Micrococcus flavus, Salmonella enteritidis, Streptococcus pneumoniae and Streptococcus mutans, but not on growth of Candida albicans. Moreover, the isolates L. salivarius BGHO1 and L. gasseri BGHO89 were tolerant to low pH and high concentration of bile salts. CONCLUSION: Taken together, these findings imply that L. salivarius BGHO1 and L. gasseri BGHO89 might be subjects for additional investigation as potential probiotic strains.     

Development of multi-species consortia biofilms of oral bacteria as an enamel and root caries model system

The aim was to establish defined-species consortium plaque biofilms to investigate enamel and root caries in an artificial mouth. Strains of the putative enamel and root caries pathogens, Streptococcus mutans, Strep. sobrinus, Actinomyces naeslundii and Lactobacillus rhamnosus, were screened in batch culture for potential cariogenic properties: a low terminal pH, ability to aggregate, and catabolic diversity. The strains selected were grown as monoculture biofilms and as consortium plaque biofilms in a multiplaque artificial mouth. The biofilms were supplied with a constant flow of a simulated oral fluid and were given periodic sucrose (and in some instances glucose) to simulate meals. All the bacteria except L. rhamnosus formed large, monospecies biofilms with resting pH in the range 5.3-5.8. The consortia biofilms were larger and had a resting pH of 4.9-5.3. The consortia biofilms supplied with 8-hourly carbohydrate comprised mainly 'mutans' streptococci (58, SD 5.5%) and L. rhamnosus (42, SD 5.7%). A. naeslundii characteristically was absent or present in a low percentage (up to 4% colony-forming units). All biofilms demineralized polished bovine enamel and dentine blocks, as assessed by microradiography and enamel-surface microhardness measurement. The consortia also demineralized intact enamel and tooth roots; they were more cariogenic to enamel than any of the monoculture biofilms, as measured by enamel-surface softening, but variation in lesion depth was proportional to biofilm wet weight irrespective of acidogen composition (r = 0.93, p < 0.05). Enamel lesions had a well-mineralized intact surface and a zone of subsurface demineralization, typical of early natural lesions. Dentine and root lesions showed extensive demineralization but lacked a pronounced surface mineralized zone. Substitution of glucose for sucrose had no effect on the cariogenicity of the consortium to bovine enamel or human roots and had no major effect on the plaque composition. Continuously supplied fluoride (19 parts/10(6)) resulted in a substantially reduced enamel surface softening and subsurface demineralization of intact roots. It was concluded that consortia biofilms of selected caries pathogens generate realistic caries lesions in all tooth hard tissues under controlled growth conditions in the artificial mouth. This in vitro caries experimental model may prove useful for the study of interrelations between the plaque biofilm, tooth tissues and the oral environment, and for the development of procedures to modify the course of caries development.     

Lactobacillus plantarum for oral peptide delivery

AIMS: To evaluate strains of lactobacilli for their ability to persist and secrete heterologous protein in the oral cavity. METHODS AND RESULTS: Four different strains of common oral lactobacilli, Lactobacillus brevis, Lactobacillus johnsonii, Lactobacillus murinus and Lactobacillus plantarum, were transformed with the plasmid pKTH2121, which contains a secretion cassette for beta-lactamase. Lactobacilli isolated from the mouth of host mice were also transformed with pKTH2121 for later feeding. Lactococcus lactis, transformed with pKTH2121, was also fed to mice as a negative control. All transformed isolates were fed to C57Black mice in varying schedules. The number of transformed bacteria persisting in the mouth was reported as a percentage of total oral bacteria recovered by swabbing. CONCLUSIONS: The transformed L. lactis, L. brevis, L. johnsonii, L. murinus, and the endogenous murine lactobacillus strain failed to persist in the mouth. Transformed L. plantarum, however, persisted in the mouth and comprised up to 25% of the total lactobacilli at 18 h and 10% at 24 h after feeding. L. plantarum recovered after feeding retained its ability to secrete beta-lactamase into culture medium efficiently. Beta-lactamase activity could be detected in oral secretions at 8 h after feedings. After repeated feedings, however, the L. plantarum containing pKTH2121 gradually lost its ability to persist after feedings. This experiment demonstrates that L. plantarum can transiently colonize the oral mucosa in large numbers, while continuously secreting foreign proteins, raising the possibility of using lactobacilli as a vector for delivery of oral mucosal peptides.     

Effect of acetate on sorbitol fermentation by oral lactobacilli

The rate of acid production and end-products from sorbitol were measured under anaerobic conditions in washed-cell suspensions of oral strains of Lactobacillus casei subsp, casei and Lactobacillus casei subsp, rhamnosus . The enzymatic activities were assayed in cell extracts of these strains. The cells fermented sorbitol to lactate, formate, ethanol and acetate under anaerobic conditions. Exposure of the cells to air (oxygen) led to inactivation of pyruvate formatelyase and inhibition of anaerobic sorbitol fermentation. In the presence of acetate, air-exposed cells fermented sorbitol with a concomitant consumption of acetate and production of ethanol and lactate. Acetate also enhanced acid production from sorbitol in cells kept under anaerobic conditions and resulted in formation of lactate and ethanol. Cell extracts of all the strains had NADH-coupled acetate-reducing activity, which consisted of sequential reactions of acetate kinase, phosphotrans-acetylase, acylating aldehyde dehydrogenase and alcohol dehydrogenase. These findings indicate that oral lactobacilli can utilize acetate as an electron acceptor for maintaining their intracellular redox balance during anaerobic sorbitol fermentation in the absence of pyruvate formate-lyase activity.     

Ecological and immunopathological implications of oral bacteria in Helicobacter pylori-infected disease

Increasing evidence has linked colonization by Helicobacter pylori with the development of gastritis and peptic ulcer disease. H. pylori resides primarily in the gastric mucosa without invading the gastric epithelium, causing persistent mild gastric inflammation. There are many reports examining the relationship between colonization by microorganisms in the stomach and oral cavity. We found that some oral bacteria are able to trap H. pylori cells, but oral bacteria inhibit H. pylori growth in vitro. In cases where H. pylori was detected in oral cavity samples, including oral cancer surface samples, we suggested that this species had colonized the stomach and were present in the oral cavity only as a transient organism. We demonstrated that periodontopathic Campylobacter rectus strains posses proteinaceous antigens, including heat shock proteins that share antigenicity with antigens of H. pylori strains. These cross-reactive antigens between H. pylori and C. rectus may be related to the induction of immunopathological responses in periodontal tissues and the stomach. We concluded that H. pylori could not survive in the human oral cavity; however, there would be an interrelationship between periodontal disease due to C rectus and stomach diseases due to H. pylori.     

口腔多菌种生物膜对防龋中药敏感性的实验研究

目的采用MBECTM-Device研究防龋中药五倍予多酚性化合物(GCE)、五倍子B(GCE-B)、蜂房95%组分(NVEI)对多菌种生物膜细菌的生长抑制作用,建立防龋中药药效学的药物敏感实验方法,为临床实验提供客观的药物作用的浓度范围。方法选择与龋病发生密切相关的4种口腔细菌形成多菌种生物膜,药物为GCE、GCE-B、NVEl,扫描电镜观察口腔细菌在MBEC州一Device上形成细菌生物膜的能力和形成情况;采用MBECn._HTP_Assav测定药物对口腔细菌的最小抑菌浓度(MIC)和对细菌生物膜的最小生物膜清除浓度(MBEC)。结果在MBFCm_Device提供的桩钉表面上I]腔细菌能形成良好的生物膜结构,从不同时段取出酌样本可以观察到细菌从定植粘附到生物膜形成以及生物膜成熟结构。GCE. GCE-B、NVEl对口腔细菌均有良好的抑制作用。GCE、GCE-B对口腔生物膜细菌有很好的抑制作用,但是NVEI对口腔生物膜细菌的抑制作用较差。药物对口腔生物膜细菌的MBEC是MIC的2-16倍。结论中药五倍子多酚性化合物和五倍子B对口腔生物膜细菌有很好的抑制和清除效应,MBEC比MIC能更客观地反映药物作用的浓度范围     

The ability of selected oral microorganisms to emit red fluorescence

Some novel caries detection and excavation devices rely on the ability of bacteria to produce red fluorescing compounds. The aim of this study was to examine the ability of selected oral microorganisms to emit red fluorescence. Streptococcus mutans, S. oralis, S. salivarius, S. sobrinus, Lactobacillus fermentans, L. casei, L. rhamnosus, Actinomyces naeslundi, A. israelii, Prevotella intermedia, and Fusobacterium nucleatum were inoculated onto Columbia agar with haemin and vitamin K and incubated anaerobically for up to 7 days in the dark. The resulting bacterial colonies were excited using filtered xenon light (405 +/- 20 nm) and digitally photographed through a 530-nm high-pass filter. The red and green portions of the colony fluorescence were analyzed using a computer program and the red/green ratio was calculated. All colonies emitted both red and green fluorescence. The green outweighed the red portion for the following species (in descending order) S. oralis, S. salivarius, S. mutans, F. nucleatum and S. sobrinus. The red portion was higher for the following species (in descending order) P. intermedia, A. naeslundi, A. israelii, L. fermentans, L. rhamnosus and L. casei. With all the bacteria examined, one color portion generally outweighed the other, giving the visual impression of either red or green fluorescence. We conclude that red fluorescence is well suited to detection of the bacteria which cause dentin caries but it is not suitable as an indicator of the presence and activity of the streptococci involved in initial caries.     

Helicobacter pylori adheres selectively to Fusobacterium spp

Helicobacter pylori strains ATCC 43504 and ATCC 43629 were tested for their ability to coaggregate with 79 strains of bacteria representing 16 genera. All except two of the strains were of human origin, and most of the strains were isolated from the oral cavity. The helicobacters failed to coaggregate with all strains except the fusobacteria. Several coaggregations were partially or completely inhibited by lactose. Strong coaggregation was seen with each of four subspecies of Fusobacterium nucleatum and with Fusobacterium periodonticum ATCC 33693, all of human dental plaque origin. In contrast, the helicobacters failed to coaggregate with non-plaque isolates, Fusobacterium mortiferum ATCC 25557 and Fusobacterium ulcerans ATCC 49185. Heat treatment of the fusobacteria inactivated their ability to coaggregate, whereas heating of the helicobacter partners had no effect, suggesting the presence of an adhesin on the fusobacteria and a corresponding receptor on the helicobacters. The potential ability of H. pylori to colonize the oral cavity by adhering selectively to the ubiquitous fusobacteria gives credence to the possibility that dental plaque may serve as a reservoir for this pathogen outside of the stomach.     

口腔鳞癌患者血清催乳素的变化对预后的影响

目的 研究血清催乳素(PRL)水平的变化对口腔鳞癌患者预后的影响。方法 采用放射免疫分析(RIA)检测68例口腔鳞癌患者手术前后血清PRL水平的改变。结果 26例口腔鳞癌患者术前血清PRL水平升高(P<0.01);30例术后血清PRL值>17.1μg/L的患者中有28例术后发生复发或转移(P<0.01)。结论 血清PRL升高提示可能与口腔鳞癌的发生发展有关。