Involvement ofN-Acetyl-D-galactosamine-specific Lectin in Biofilm Formation by the Periodontopathogenic Bacterium,Eikenella corrodens

Eikenella corrodens is known not only as one of the periodontopathogenic bacteria but also as a pathogen associated with many infectious diseases of humans. Dental plaque is a complex biofilm community comprised of many bacterial species. E. corrodens has a lectin on its cell surface that is thought to be involved in its pathogenicity. In this study, we found that E. corrodens forms a biofilm on a polystyrene surface. A biofilm was formed at the bottom of the wells in microtiter plates after 24 h. Microcolonies were observed as the amount of biofilm became larger. When anaerobic respiration was repressed due to nitrate limitation, the biofilm formed only at the air-water interface. Strain 1073 and HU, which have higher lectin activity, formed a biofilm more effectively than other strains. Biofilm formation was repressed by the addition of N-acetyl-D-galactosamine. These results suggest that the lectin on the surface of E. corrodens might be involved in biofilm formation.

Caries-related plaque microcosm biofilms developed in microplates

In vivo dental plaque biofilms consist of complex communities of oral bacteria that are a challenge to replicate in vitro. The aim of this investigation was to establish human dental plaque microcosms in microplates to reflect conditions that are relevant to dental caries. Microcosm plaque biofilms were initiated from the saliva of two different donors, grown for up to 10 days in 24-welled microplates on Thermanox coverslips in various types of artificial saliva with and without sucrose, which were replaced daily. Microbiota composition of 40 species associated with oral health and dental caries was monitored in the plaques using Checkerboard DNA-DNA hybridization analysis. pH was measured as an indicator of cariogenic potential. The composition of the saliva inocula was different, and yielded plaque microcosms with different composition and growth responses to sucrose. Artificial saliva type and presence of sucrose, and the resulting growth and pH conditions, modified the growth of individual species and hence the ecological profile of the microplate plaques during development. Complex population shifts were observed during development, and older plaques comprised predominantly facultative anaerobic species. Sucrose supplementation limited the decline of Streptococci over time but did not increase the abundance of mutans Streptococci. Sucrose at 0.15% increased levels of caries-associated species including Lactobacillus fermentum, Lactobacillus acidophilus and Actinomyces gerensceriae; these were further increased with sucrose at 0.5%, in addition to Actinomyces israelii, Rothia dentocariosa and Capnocytophaga gingivalis. The microplate plaques demonstrated complex community dynamics that appeared to reflect the maturation of natural plaques, and sucrose induced a cariogenic plaque composition and pH.

Plasmid-mediated genomic recombination at the pilin gene locus enhances the N-acetyl-d-galactosamine-specific haemagglutination activity and the growth rate of Eikenella corrodens

Eikenella corrodens belongs to a group of periodontopathogenic bacteria and forms unique corroding colonies on solid medium due to twitching motility. It is believed that an N-acetyl-d-galactosamine (GalNAc)-specific lectin on the cell surface contributes significantly to its pathogenicity and can be estimated by its haemagglutination (HA) activity. Recently, a plasmid, pMU1, from strain 1073 has been found; this plasmid affects pilus formation and colony morphology. To identify the gene involved in these phenomena, ORF 4 and ORFs 5–6 on pMU1 were separately subcloned into a shuttle vector, and the resultant plasmids were introduced into E. corrodens 23834. Transformants with the ORF 4 gene, which is identified to be a homologous gene of the type IV pilin gene-specific recombinase, lost their pilus structure and formed non-corroding colonies on a solid medium, whereas transformants with ORFs 5–6 exhibited the same phenotype as the host strain 23834. Southern analysis showed that the introduction of the ORF 4 gene into strain 23834 resulted in genomic recombination at the type IV pilin gene locus. The hybridization pattern of these transformants was similar to that of strain 1073. These results suggest that ORF 4 on pMU1 encodes a site-specific recombinase and causes genomic recombination of the type IV pilin gene locus. Furthermore, the introduction of ORF 4 into strain 23834 increased GalNAc-specific HA activity to a level equivalent to that of strain 1073. Although the morphological colony changes and loss of pilus structure are also observed in phase variation, genomic recombination of the type IV pilin gene locus did not occur in these variants. Moreover, an increase was not observed in the GalNAc-specific HA activity of these variants. These results suggested that the loss of pilus structure, the morphological change in colonies and the increase in HA activity due to plasmid pMU1 might be caused by a mechanism that differs from phase variation, such as a genomic recombination of the type IV pilin gene locus.

[Eikenella corrodens infective endocarditis]

The HACEK microorganisms (Haemophilus spp, Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, and Kingella kingae) account for 3% of the cases of endocarditis. They have the following similar clinical and microbiological properties: are Gram-negative bacilli, more easily isolated in aerobic media; their cultures require prolonged incubation time for growing (mean, 3.3 days); and may be considered part of normal flora of upper respiratory tract and oropharynx. The following characteristics have been identified in endocarditis caused by the HACEK microorganisms: insidious clinical findings; difficult diagnosis due to the fastidious nature of the microorganisms; and negative cultures. The Eikenella corrodens endocarditis was first described in 1972. That microorganism continues to be a rare etiological agent. We report the case of a female patient with native valve, who had Eikenella corrodens infective endocarditis.

Isolation and characterization of a plasmid DNA from periodontopathogenic bacterium, Eikenella corrodens 1073, which affects pilus formation and colony morphology

Eikenella corrodens (Ec) is one of a group of periodontopathogenic bacteria. A plasmid DNA (8.7 kb) isolated from Ec 1073 was designated pMU1. Agarose gel electrophoresis and Southern analysis suggested that pMU1-like plasmids were carried in 2 Ec strains, including 1073, with higher hemagglutination (HA) activity than other strains. We determined the nucleotide sequence of this plasmid and identified 7 ORFs. A homology search revealed that 4 ORFs of pMU1 were homologous to ORFs in pJTPS1, found in a spontaneous avirulent mutant of the phytopathogenic bacterium, Ralstonia solanacearum. pJTPS1 is a putative hypovirulent plasmid, which is thought to control the virulence of R. solanacearum. We also found the ORF to be homologous to the recombinase specific to the type IV pilin gene. We introduced a part of pMU1 into the Ec 23834 strain, which has a pilus structure on its cell surface and forms corroding colonies on solid medium. No pilus structure was observed on the surface of transformants, most of which formed non-corroding colonies. When such transformants (or Ec 1073) were cured of pMU1 with acridine orange, they remained non-foliated and non-corroding. The results suggest that pMU1 might irreversibly affect pilus formation and colony morphology, and might be involved in the pathogenicity and virulence of Ec.

Microbial profile on metallic and ceramic bracket materials

The placement of orthodontic appliances creates a favorable environment for the accumulation of a microbiota and food residues, which, in time, may cause caries or exacerbate any pre-existing periodontal disease. The purpose of the present study was to compare the total bacterial counts present on metallic and ceramic orthodontic brackets in order to clarify which bracket type has a higher plaque retaining capacity and to determine the levels of Streptococcus mutans and Lactobacillus spp on both types of brackets. Thirty-two metallic brackets and 24 ceramic brackets were collected from orthodontic patients at the day of debonding. Two brackets were collected from each patient; one from a maxillary central incisor and another from a maxillary second premolar. Sixteen patients who used metallic brackets and 12 patients who used ceramic brackets were sampled. Bacterial populations were studied using "checkerboard" DNA-DNA hybridization, which uses DNA probes to identify species in complex microbial samples. The significance of differences between groups was determined using the Mann-Whitney U-test. Results showed no significant differences between metallic and ceramic brackets with respect to the caries-inducing S mutans and L acidophilus spp counts. Mean counts of 8 of 35 additional species differed significantly between metallic and ceramic brackets with no obvious pattern favoring one bracket type over the other. This study showed higher mean counts of Treponema denticola, Actinobacillus actinomycetemcomitans, Fusobacterium nucleatum ss vincentii, Streptococcus anginosus, and Eubacterium nodatum on metallic brackets while higher counts of Eikenella corrodens, Campylobacter showae, and Selenomonas noxia were found on ceramic brackets.

Contamination of interdental brushes by periodontopathogens

Experimental studies have shown that intraoral transmission of bacteria can occur. Of course, the question arises as to how this transmission may happen. In this study, the contamination of interdental brushes by periodontopathogens is examined and compared to the microbial load of the periodontal pockets. In ten untreated chronic periodontitis patients, four interdental sites were professionally brushed with one interdental brush per patient. Subsequently, samples from the depths of the pockets (of the specific interdental sites) were obtained with paper-points. The interdental brush samples and the samples of the subgingival plaque, obtained by the pooled paper-points, were processed for dark-field microscopy examination as well as anaerobic culturing. The results showed that, although significant differences could be found between the brushes and paper-points with direct microscopy, the culturing did not uncover many differences. On the contrary, the detection frequencies of specific bacterial species were almost the same between the two. The total anaerobic colony-forming units (CFU), P. gingivalis, F. nucleatum, and E. corrodens found on the brushes showed a significant correlation with the subgingival plaque samples (P<0.005). These results suggest that, in untreated situations, interdental brushes are contaminated relatively easily by putative periodontopathogens in numbers comparable to their presence in periodontal pockets. This contamination could be a factor in the intraoral spread of bacteria.

Salivary microbiota levels in relation to periodontal status, experience of caries and miswak use in Sudanese adults

OBJECTIVES

The purpose of the present investigation was to assess the salivary levels of 25 oral bacteria in relation to periodontal status and experience of caries, and to compare the levels of these bacteria between habitual miswak and toothbrush users in adult Sudanese subjects.

MATERIAL AND METHODS

The study subjects consisted of 56 individuals with age range 19-53 years (mean 35.2 years) and included 30 miswak and 26 toothbrush users. The periodontal status and presence of dental caries were assessed clinically. Whole saliva was collected from all subjects, and the levels of 25 selected bacterial species in saliva were assessed by the checkerboard DNA-DNA hybridization method using whole genomic DNA probes.

RESULTS

A high percentage of the subjects had detectable levels (> or = 105 bacterial cells) of several bacterial species in saliva. Between 12% and 16% of the subjects showed high (> or = 106 cells) salivary levels of the periodontitis-associated bacteria A. actinomycetemcomitans, P. melaninogenica, P. intermedia, C. rectus and E. corrodens, whereas only two (3.6%) and four (7.1%) subjects had high levels of P. gingivalis and F. nucleatum, respectively. There were no significant differences in the levels of all or most bacterial species by age group, gender or periodontal status. Presence of > or = 105 L. acidophilus bacterial cells in saliva was associated with high caries scores (p = 0.02). There were significantly higher levels of A. actinomycetemcomitans, P. melaninogenica, C. rectus, P. micros, V. parvula, S. mutans, S. anginosus, A. israelii, C. sputigena, and C. gingivalis, and significantly lower levels of P. intermedia, F. nucleatum, S. sputigena, E. corrodens, L. acidophilus, S. sanguis, S. salivarius, S. oralis, and S. mitis in the miswak than in the toothbrush group.

CONCLUSIONS

: The findings suggest that miswak may have a selective inhibitory effect on the level of certain bacteria in saliva, particularly several oral streptococci species. This is the first report that the checkerboard DNA-DNA hybridization method can be useful for assessing the levels of a wide range of bacterial taxa in saliva.

The characterization of a (nutritionally important) proline iminopeptidase from Eikenella corrodens

Eikenella corrodens generates energy primarily through the oxidative deamination of specific amino acids, a process that is coupled to dissimilatory nitrate reduction to nitrite. Cell yields resulting from chemostat-growth of the organism in simple, chemically defined media containing varying amounts of proline confirm that this amino acid is a likely source of energy for E. corrodens in the oral environment. The importance of proline in ATP generation by the organism is reflected in molar growth yields, which showed that biomass production per mole of this amino acid was significantly higher than that for other amino acids. The organism was found to express, constitutively, the enzyme proline iminopeptidase, which releases proline from the N-terminus of small peptides. The enzyme was partially purified and characterized and found to exist in the cytoplasm as a 35 kDa monomer. Inhibition studies showed that the enzyme, although classified as a serine protease, also appears to require thiol groups for activity, a finding which is consistent with previous reports. The enzyme obeyed Michaelis-Menten kinetics and was found to have a Km value of 0.223 mM for the substrate proline-p-nitroanilide.

The localization of periodontal-disease-associated bacteria in human periodontal pockets

Some Gram-negative anaerobes are associated with the incidence and progression of periodontal disease. In periodontal pockets, however, the localization of those bacteria is unknown. We investigated the localization of 5 bacterial species in human periodontal pockets. Fifteen teeth with a part of periodontal pockets from 10 adult periodontitis patients were obtained, and the localization of bacteria was examined immunohistochemically. Positive reactions with anti-Prevotella nigrescens antibody were located at the epithelium-associated plaque area in the middle pocket zones. In the middle and deep pocket zones, Fusobacterium nucleatum and Treponema denticola were especially localized in the unattached plaque area, but Eikenella corrodens was observed in the tooth-attached plaque area. Actinobacillus actinomycetemcomitans, detected in 2 of 15 samples examined, was found in the unattached plaque area, in the middle pocket zone. The present findings indicated that the 5 bacterial species examined localized at distinct regions in human periodontal pockets.

Antimicrobial effect of acidified nitrite on periodontal bacteria

The antimicrobial agent nitric oxide (NO) is formed in the mouth and its concentration is directly related to salivary nitrite, which in turn is related to dietary nitrate intake. The aim of this study was to determine whether nitrite under acidic conditions will have an inhibitory effect, possibly occurring through NO production, on the periodontal disease pathogens Fusobacterium nucleatum, Eikenella corrodens and Porphyromonas gingivalis. Whereas the growth of these organisms was inhibited by a more acid pH, the addition of nitrite caused a marked, further dose-dependent reduction in bacterial numbers after exposure. The ability of these bacteria to recover from nitrite exposure was also affected by pH and nitrite concentration. At acidity levels below pH 5.0, low concentrations of nitrite (0.2 mM) caused effective complete killing of the periodontal bacteria. Addition of sodium thiocyanate did not increase the bacteriostatic or bacteriocidal activity of acidified nitrite against any of the 3 bacteria. These results demonstrate the possibility that nitrite in saliva, under appropriate conditions, may have an effect on the growth and survival of the bacteria implicated in periodontal disease.

Relationship of periodontopathic bacteria with early-onset periodontitis in Down's syndrome

BACKGROUND

Down's syndrome (DS) patients often develop severe early-onset marginal periodontitis in early adulthood; however, there is little information available on the microbiology of DS periodontitis.

METHODS

Subgingival plaque specimens were taken from 67 DS young adults and 41 age-matched systemically healthy individuals with mental disabilities (MD). The prevalence of 10 possible periodontopathic bacterial species, Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Bacteroides forsythus, Treponema denticola, Prevotella intermedia, Prevotella nigrescens, Capnocytophaga ochracea, Capnocytophaga sputigena, Campylobacter rectus, and Eikenella corrodens, were investigated in their subgingival plaque samples using a polymerase chain reaction method. The detection of P. gingivalis fimA genotypes was also performed in P. gingivalis-positive samples.

RESULTS

Although DS subjects generally develop an earlier and more extensive periodontal breakdown than those with MD, no significant differences were observed in the bacterial profiles. The profiles of subjects with periodontitis were significant in DS, but not in MD. The prevalence of P. gingivalis, B. forsythus, and P. intermedia were significant in the DS periodontitis group, compared to DS gingivitis group. Moreover, the occurrence of P. gingivalis with the type II fimA gene was significantly related to periodontitis in both DS and MD, with odds ratios of 6.32 and 12.03, respectively.

CONCLUSIONS

These results suggest that early-onset periodontitis in DS is mainly due to the more susceptible host for the causative microbial agents including P. gingivalis with type II fimA.

"Checkerboard" assessments of periodontal microbiota and serum antibody responses: a case-control study

BACKGROUND

We explored the association between subgingival microbial profiles and serum IgG responses to periodontal microbiota in relation to clinical periodontal status.

METHODS

One hundred thirty-one (131) periodontitis patients aged 29 to 74 years (mean 51.8) were age- and gender-matched with 74 periodontally intact controls (range 26 to 77, mean 49.3). Smoking habits and health history were recorded and assessments of plaque, bleeding on probing, probing depth, and attachment level were performed at 6 sites per tooth on all present teeth, excluding third molars. Subgingival plaque samples were obtained from each tooth in one upper and one lower quadrant (maximum 14 samples/subject; 2,440 samples total) and analyzed with respect to 19 species by means of whole genomic DNA probes. Serum IgG antibodies against the same 19 species were assessed by an immunoassay.

RESULTS

Cases displayed an average of 22.7 teeth, 20.3 sites with probing depth > or =6 mm, and 18.9 sites with attachment loss > or =6 mm. Corresponding figures for controls were 27.1, 0.1, and 1.0, respectively. Heavy smoking was 3 times more frequent among cases than controls (32.1% versus 9.6%). Higher levels of Porphyromonas gingivalis, Porphyromonas endodontalis, Prevotella intermedia, Prevotella nigrescens, Prevotella melaninogenica, Bacteroides forsythus, Fusobacterium nucleatum, Treponema denticola, Eubacterium nodatum, Peptostreptococcus micros, and Campylobacter rectus were found in cases and higher levels of Eikenella corrodens, Veillonella parvula, and Actinomyces naeslundii in controls. Cases displayed higher IgG levels against P. gingivalis and Actinobacillus actinomycetemcomitans, while controls displayed higher levels against F. nucleatum, T. denticola, E. nodatum, and Capnocytophaga ochracea. Positive correlations between bacterial colonization and antibody responses were identified for 9 species in controls. In cases, however, statistically significant correlations were observed for only 3 species out of which only one was positive (V. parvula). Both bacterial levels and antibody responses declined in ages over 55 years. A logistic regression employing selected elements of bacterial colonization and antibody responses as independent variables resulted in 81.1% correct diagnosis, with sensitivity of 83.1%, specificity of 77.8%, positive predictability of 86%, and negative predictability of 73.7%. Smoking did not reach statistical significance in this model.

CONCLUSION

A combined microbial colonization/antibody response profile can effectively discriminate between periodontitis patients and periodontally intact controls.

The prevalence of pathogenic periodontal microflora in healthy young adult smokers

BACKGROUND

Smoking is a major risk factor in periodontitis, although the mechanisms of its effects are not well understood. The overall goal of this clinical study was to determine if smoking enhances the colonization of the oral cavity by pathogenic bacteria in a periodontitis-free population. The prevalence of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Fusobacterium nucleatum, Campylobacter rectus, Eikenella corrodens, Bacteroides forsythus, and Treponema denticola was investigated in 25 smokers and 25 non-smokers by using DNA probes.

METHODS

The subjects were 21 to 35 years of age with a healthy periodontium or slight gingivitis and were systemically healthy. The test group included subjects who had a minimum of a 1.5 pack-year history of smoking, while the control subjects never smoked. Subgingival plaque samples were taken by paper point following the assessment of multiple clinical parameters.

RESULTS

This investigation showed: 1) no statistically significant differences were noted in any clinical parameter measured between the groups; 2) of the 8 subjects who were infected by at least 1 tested pathogen, seven were smokers (P= 0.02); 3) infected smokers had a 15.7+/-3.5 pack-year history and smoked a mean of 27+/-5 cigarettes/day versus 4.4+/-0.8 pack years and 15+/-1 cigarettes/day for the non-infected smokers (P = 0.0001 and P = 0.004); and 4) smokers were 18 times more likely to exhibit the presence of pathogens than non-smokers.

CONCLUSIONS

These data indicate that the prevalence of colonization of the sulcus by pathogenic bacterial species in periodontitis-free individuals is related to the quantity and duration of cigarette smoking.

Eikenella corrodens phase variation involves a posttranslational event in pilus formation

The human pathogen Eikenella corrodens synthesizes type IV pili and exhibits a phase variation involving the irreversible transition from piliated to nonpiliated variants. On solid medium, piliated variants form small (S-phase), corroding colonies whereas nonpiliated variants form large (L-phase), noncorroding colonies. We are studying the molecular basis of this phase variation in the clinical isolate E. corrodens VA1. A genomic fragment encoding the major type IV pilin was cloned from the S-phase variant of strain VA1. Sequence analysis of the fragment revealed four tandemly arranged potential open reading frames (ORFs), designated pilA1, pilA2, pilB, and hagA. Both pilA1 and pilA2 predict a type IV pilin. The protein predicted by pilB shares sequence identity with the Dichelobacter nodosus FimB fimbrial assembly protein. The protein predicted by hagA resembles a hemagglutinin. The region containing these four ORFs was designated the pilA locus. DNA hybridization and sequence analysis showed that the pilA locus of an L-phase variant of strain VA1 was identical to that of the S-phase variant. An abundant pilA1 transcript initiating upstream of pilA1 and terminating at a predicted hairpin structure between pilA1 and pilA2 was detected by several assays, as was a less abundant read-through transcript encompassing pilA1, pilA2, and pilB. Transcription from the pilA locus was nearly indistinguishable between S- and L-phase variants. Electron microscopy and immunochemical analysis showed that S-phase variants synthesize, export, and assemble pilin into pili. In contrast, L-phase variants synthesize pilin but do not export and assemble it into pili. These data suggest that a posttranslational event, possibly involving an alteration in pilin export and assembly, is responsible for phase variation in E. corrodens.

Periodontal bacteria in adult twins

BACKGROUND

Both environmental and genetic factors are known to influence clinical measures of periodontal disease. The purpose of this study was to determine whether genetic factors similarly influence the presence of specific periodontal bacteria in subgingival plaque.

METHODS

Reared-together and reared-apart monozygous (MZ) and dizygous (DZ) adult twins were examined clinically. Demographic and behavioral information was obtained from each subject by questionnaire. Subgingival plaque samples were obtained from the index teeth, and the presence of P. intermedia, P. gingivalis, A. actinomycetemcomitans, E. corrodens, and F. nucleatum was determined using an immunoassay.

RESULTS

Microbiological and clinical data were available for 169 twin pairs. The subject-based prevalences of the bacteria in the twin groups ranged from 11% for Porphyromonas gingivalis to 40% for F. nucleatum. For all species examined, the concordance rates were not significantly different (P > 0.05) between MZ and DZ twin groups. These findings were apparent despite similar smoking histories, self-reported oral hygiene practices, and antibiotic use in the twin groups. Furthermore, MZ twins reared together were not more similar than MZ reared-apart twins with respect to any bacterial species examined.

CONCLUSIONS

These findings suggest that in a population with access to routine dental care, any effects that host genes and the early family environment have on the presence of specific bacteria in subgingival plaque are not apparent in adulthood. Most twins with disease in this study had early periodontitis. Results from this study may not necessarily be extrapolated to more advanced disease states.

Microbiological features and crevicular fluid aspartate aminotransferase enzyme activity in early onset periodontitis patients

Gingival crevicular fluid (GCF) reflects the immune and inflammatory reactions and the specific host-microbe interactions that lead to periodontal diseases. Aspartate aminotransferase enzyme (AST) is one of the components of GCF that is released as a result of cell death. In this study, periodontal sites (4 sites/patient) with a probing depth of > or =5 mm in early onset periodontitis (EOP) patients were first examined for the AST levels in GCF by the Periogard periodontal tissue monitor. To be eligible for the study, each of the patients had at least 1 AST positive site with clinical inflammatory changes (AST+, CIC+) and 1 AST negative site with no or minimum clinical inflammatory changes (AST-, CIC-). In 15 EOP patients who met the entry criteria, 30 AST+, CIC+ sites (1st group) and 19 AST-, CIC- sites (2nd group) were evaluated for microbiological variables. Certain microbial species, including Porphyromonas gingivalis, Actinobacillus actinomycetemcomitans and Prevotella intermedia were detected more frequently (p<0.001, p<0.001 and p<0.05, respectively) in the 1st group, while gram-positive facultative organisms such as Actinomyces species were found more often (p<0.001) in the 2nd group. Parallel to the AST levels, the 2nd group had a lower number of total bacteria and proportion of obligate anaerobic and capnophilic micro-organisms than the first group (p<0.05 and p<0.05, respectively). Within the scope of this study, AST activity and microbiological data were found in agreement in the examined groups. These findings are encouraging and indicate the need for further studies to evaluate the ability of the AST test to differentiate the microbial flora of progressing sites and those that are inflamed, but not progressing.

Neutrophil response and microbiological findings around teeth and dental implants

The aim of this study was to compare the neutrophil response, measured as both functional and antigenic elastase, around teeth and titanium implants and to relate these findings to the microbiota. The 31 patients included in the study had been treated successfully for total or partial edentulism with titanium implants. Crevicular fluid and microbiological samples were taken from 3 sites: 1) crevices around teeth and 2) implants in 16 partially edentulous patients and 3) crevices around implants in 15 edentulous patients. All sites sampled showed similar degrees of inflammation assessed by gingival index and total protein concentration. The samples were analyzed for elastase activity and immunoreactive elastase. The elastase activity was significantly higher in crevices surrounding implants in partially edentulous patients compared with implants in edentulous patients. The antigenic elastase showed no difference among the 3 sites. Gram-positive cocci were the main bacterial species in all 3 groups. Edentulous patients tended to have lower frequency of black pigmenting anaerobes. No correlation of analyzed bacteria and elastase activity was found between the 3 sites. This study indicates that, despite a similar appearance of clinical parameters and absence of significant differences in the microbiota, the inflammation around implants in partially edentulous patients induces a stronger neutrophil response than does the inflammation around implants in edentulous patients.

Comparison of broth microdilution method using Haemophilus test medium and agar dilution method for susceptibility testing of Eikenella corrodens

Susceptibility testing of Eikenella corrodens is usually performed by a Mueller-Hinton sheep blood agar dilution (AD) method. However, this method is impractical for testing only a few strains. We compared AD with the broth microdilution method using Haemophilus test medium (HTM) in order to determine the susceptibility of 36 clinical isolates of E. corrodens to eight antimicrobial agents. MICs obtained by the HTM method yielded 95.5 and 84% agreement (within 2 and 1 log2 dilutions, respectively) with those obtained by AD. The HTM method with incubation in CO2 for 48 h was highly reproducible and constitutes an easy alternative for antimicrobial susceptibility testing of E. corrodens.

Subgingival distribution of periodontopathic bacteria in adult periodontitis and their susceptibility to minocycline-HCl

The purpose of this study was to investigate the distribution of several periodontopathic bacteria in adult periodontitis, their in vitro susceptibility to minocycline-HCl, and whether the efficacy of the drug changes with a decrease in bacterial susceptibility. Twenty-one patients (43 to 75 years old) with 62 periodontal lesions from pockets > or =4 mm participated in the study. After subgingival sampling, an ointment containing 2% minocycline-HCl was applied locally to the selected pockets once a week for 4 weeks. The lesions were clinically examined after 1 and 4 weeks of administration. The distribution of the subgingival microorganisms included Capnocytophaga sputigena (37.1%), Prevotella intermedia (22.6%), Porphyromonas gingivalis (22.6%), Fusobacterium nucleatum (20.1%), Actinobacillus actinomycetemcomitans (9.7%), and Eikenella corrodens (4.8%). The distribution was complex, with 76.8% of the sites containing 1 to 3 bacterial spieces. The minimum inhibitory concentration (MIC) of minocycline-HCl for each organism showed that most were inhibited by a minocycline-HCl concentration equal to or less than the MIC for reference strains. However, some clinical strains of Prevotella intermedia seemed to exihibit low susceptibility to minocycline-HCl. There were no significant differences among sites with strains exhibiting low or normal susceptibility to minocycline-HCl. The concentration of the drug applied to deep periodontal pockets inhibited the growth of most of the microorganisms investigated in this study.

Some observations on the nutritional requirements of Eikenella corrodens ATCC 23834T grown in continuous culture

The type strain, ATCC 23834, of Eikenella corrodens was grown anaerobically in continuous culture in chemically defined media. Initial experiments showed that glucose was not utilized and it was subsequently omitted from all media. The initial chemically defined medium contained varying levels of 14 amino acids and 20 mM potassium nitrate, an essential nutrient for growth under these conditions. In this medium, the doubling time was 2.1 h, the optimum growth temperature 34 degrees C and the pH 7.2. The key growth-promoting amino acids were glutamate and serine, and the culture appeared to be nitrate limited. By growing the organism in a series of chemically defined media containing 40 mM nitrate and varying levels of these amino acids, glutamate was found to be the major contributor to biomass increase. Its catabolism may be linked to a respiratory chain involving nitrate as the ultimate electron acceptor.

Synergistic effect of pyrophosphate and sodium dodecyl sulfate on periodontal pathogens

Our previous studies have shown that pyrophosphate (PPi), the anticalculus component of tartar-control dentifrices, inhibits the growth of organisms associated with coronal and root surface caries. The purposes of this investigation were to: 1) determine if periodontal pathogens are similarly susceptible to the growth-inhibitory properties of PPi; and 2) determine if combinations of pyrophosphate-sodium dodecyl sulfate (PPi-SDS) inhibit growth synergistically. Porphyromonas gingivalis, Actinobacillus actinomycetemcomitans, Fusobacterium nucleatum, Eikenella corrodens, and Campylobacter rectus (formerly Wolinella recta) were cultured in appropriate enriched media under anaerobic conditions. Inhibition assays were performed in tubes containing media supplemented with PPi and/or SDS. A range of concentrations of PPi and SDS in 2-fold increments was employed, with each concentration assayed in triplicate. Minimal inhibitory concentration (MIC) analyses revealed all of the bacteria were susceptible to PPi and SDS, with MICs of 0.67% (25 mM) and 0.01% w/v respectively. Combination studies with PPi-SDS showed much greater growth inhibition against P. gingivalis and A. actinomycetemcomitans than achieved with the agents individually. Determination of fractional inhibitory concentration indices indicated a synergistic growth-inhibitory effect. Under the constraints of the conditions employed, these studies demonstrate the efficacy of PPi-SDS combinations in inhibiting the growth of periodontal pathogens. It is conceivable that these compounds may have clinical benefit as a subgingival irrigant.

Outer membrane protein and lipopolysaccharide heterogeneity among Eikenella corrodens isolates

Outer membrane protein (OMP) and lipopolysaccharide (LPS) phenotypic diversity among 27 oral and extraoral strains of Eikenella corrodens was assessed by SDS-PAGE. Each strain exhibited one to three major protein bands in the 35- to 41.5-kDa range and one or two protein bands of lesser density in the 24.5- to 28-kDa range. Eleven OMP patterns were distinguished among the strains. While oral strains obtained from periodontally healthy and diseased subjects exhibited diverse OMP patterns, five of six strains from extraoral sites of infection expressed an identical OMP pattern. Comparison of the electrophoretic mobilities of LPS from these same strains revealed that E. corrodens LPS consists primarily of low apparent molecular mass forms. Sixteen different LPS phenotypes were differentiated among the strains, with no apparent correlation between LPS phenotype and clinical setting. Strains expressing the same OMP pattern frequently expressed variable LPS phenotypes and vice versa. Analysis of OMP or LPS pattern by SDS-PAGE may be useful in taxonomic and epidemiologic studies of E. corrodens. Additional studies assessing the potential influence of OMP composition on invasiveness of this organism appear warranted.

Deoxyribonucleic acid relatedness and phenotypic variation among human isolates of Eikenella corrodens

The type strain of Eikenella corrodens (Eiken 1958) Jackson and Goodman 1972 and eleven epidemiologically independent clinical isolates recovered from periodontal locations, putrid wounds, abscesses, and bacteraemias were investigated for their genomic relationships by DNA-DNA hybridization with the renaturation method, genome molecular complexity, DNA base composition and some phenotypic features. The bacterial strains studied were interrelated at or above the 80% DNA binding level, their chromosomal DNAs exhibiting a mean molecular mass of 1.7 x 10(9) daltons and a mean guanine plus cytosine content of 55.1 mol%. Variations in colonial morphology, hemolytic activity on sheep blood agar, reduction of nitrates, oxidation of carbohydrates, lipase, leucine, valine, and cystine aminopeptidase and acid phosphatase activities occurred among closely interrelated strains. The definition of the species and current identification keys must be emended accordingly.

Eikenella corrodens as a cause of brain abscess

A case of brain abscess due to Eikenella corrodens in a 67-year-old woman is reported. To our knowledge, this is the first case in which the causative organism has been isolated from the occipital lobe. E. corrodens may be the cause of apparently sterile brain abscesses encountered in neurosurgery and should be considered in the differential etiology of brain abscess.

Early microbial colonization of permucosal implants in edentulous patients

In edentulous patients, the microbial colonization of permucosal implants of sintered hydroxyapatite was studied. Samples were taken from mucosa and dentures before insertion of implants and from supra- and subgingival sites two to 10 weeks after insertion. In total, five patients and 10 implants with clinically healthy peri-implant tissues were studied. The samples were investigated by dark-field microscopy and anaerobic culture. The supragingival plaque of the implants was dominated by Gram-positive cocci and rods, the subgingival plaque by Haemophilus spp. and Veillonella parvula. A group of bacteria was found specifically related to the implants: Actinomyces odontolyticus, Peptostreptococcus micros, Haemophilus actinomycetemcomitans, Eikenella corrodens, Capnocytophaga sputigena, and Leptotrichia buccalis. Black-pigmented Bacteroides was not found in any of the examined samples. Spirochetes were observed in denture plaque samples and in supragingival plaque of the implants. It is concluded that bacteria known as potential periodontal pathogens colonize the permucosal implants in the first weeks after insertion. The presence of these species seems to be dependent on the ecological factors provided by the artificial gingival crevice of the permucosal implants in the edentulous mouth.

Oral implantation of Bacteroides asaccharolyticus and Eikenella corrodens in conventional hamsters

Oral implantation of Bacteroides asaccharolyticus 381-R' and Eikenella corrodens 1073S-R, which are highly resistant to streptomycin, was examined in conventional hamsters. The hamsters' first molars were ligatured with cotton threads preimmersed in bacterial suspensions. Bacterial inoculation was performed daily for 1 week, followed by a single weekly inoculation for 7 more weeks. Hamsters were fed Keyes' diet no. 2000 or ordinary powdered diet. Bacterial recovery, gingival histological changes, and immunological response were checked 2, 5, and 8 weeks after the daily serial inoculation. B. asaccharolyticus 381-R' was recovered from all hamsters during the experiment (6.7 X 10(6) to 6.3 X 10(8) colony-forming units). E. corrodens 10735-R was recovered from the hamsters fed Keyes' diet no. 2000 throughout the experimental period (2.4 X 10(5) to 1.2 X 10(6) colony-forming units), but not in the group fed the ordinary powdered diet. The histological changes in gingival tissues at the second week showed no differences among the control group, the B. asaccharolyticus-inoculated group, and the E. corrodens-inoculated group. However, by the eighth week, the inflammation persisted only in the bacteria-inoculated groups, especially in the B. asaccharolyticus-inoculated group. A relatively increased serum antibody titer was also observed in the B. asaccharolyticus-inoculated group, but not in the E. corrodens-inoculated group. These findings indicate that B. asaccharolyticus 381-R' and E. corrodens 1073S-R can be implanted in hamsters' oral cavity with the aid of cotton thread ligature. It was also suggested that B. asaccharolyticus may have some pathogenic role in the destruction of periodontal tissue in hamsters.

Comparative growth of Eikenella corrodens on 15 media in three atmospheres of incubation

The abundance of growth and size of colonies of 10 isolates of Eikenella corrodens were studied using 15 commonly available media in aerobic, 5% CO2, and anaerobic atmospheres of incubation. Chocolate agar was the best medium for overall growth in all three atmospheres. Growth on Mueller-Hinton agar supplemented with 5% blood and on Brucella agar supplemented with 5% blood was equivalent to that on chocolate agar in 5% CO2 and anaerobic environments but not in an aerobic atmosphere. Strains of E. corrodens did not grow on the selective media studied. Growth on media without blood or hemin supplements occurred in anaerobic but not in aerobic or 5% CO2 environments, and was consistently poorer than growth on the same media with these supplements.