Eikenella corrodens in human oral and non-oral infections: a review

Pyoderma gangrenosum following anti-TNF therapy in chronic recurrent multifocal osteomyelitis: drug reaction or cutaneous manifestation of the disease? A critical review on the topic with an emblematic case report

Chronic recurrent multifocal osteomyelitis (CRMO) is a rare autoinflammatory disease, clinically characterized by chronic and recurrent episodes of osteoarticular inflammation, that generally presents in children and adolescents. From a dermatological point-of-view, CMRO can be associated with skin rashes mainly including psoriasis, palmoplantar pustulosis and acne. Pyoderma gangrenosum (PG) is a rare immune-mediated inflammatory skin disease classified within the spectrum of neutrophilic dermatoses that, in some cases, has been reported as cutaneous manifestation in CMRO patients. This paper presents a 16-year female patient diagnosed with CMRO, who presented PG lesions located on the lower leg, that arose after the administration of the tumour necrosis factor (TNF)-α inhibitor adalimumab. Cases of PG have been reported in patients being treated with certain medications, including TNF-α antagonists, leading to classified them in a setting aptly termed "drug-induced PG." In this paper, we discuss the co-occurrence of PG and CRMO, in the light of recent evidence on the pathogenesis of both diseases and giving ample space to a literature review on drug induced PG. In our case, it is plausible that PG could be considered a cutaneous manifestation of CRMO, although the mechanisms underlying this intriguingly relationship remain to be fully unraveled.

Oral Microbiome Community Composition in Head and Neck Squamous Cell Carcinoma

The impact of the oral microbiome on head and neck cancer pathogenesis and outcomes requires further study. 16s rRNA was isolated and amplified from pre-treatment oral wash samples for 52 cases and 102 controls. The sequences were binned into operational taxonomic units (OTUs) at the genus level. Diversity metrics and significant associations between OTUs and case status were assessed. The samples were binned into community types using Dirichlet multinomial models, and survival outcomes were assessed by community type. Twelve OTUs from the phyla Firmicutes, Proteobacteria, and Acinetobacter were found to differ significantly between the cases and the controls. Beta-diversity was significantly higher between the cases than between the controls (p < 0.01). Two community types were identified based on the predominant sets of OTUs within our study population. The community type with a higher abundance of periodontitis-associated bacteria was more likely to be present in the cases (p < 0.01), in older patients (p < 0.01), and in smokers (p < 0.01). Significant differences between the cases and the controls in community type, beta-diversity, and OTUs indicate that the oral microbiome may play a role in HNSCC.

Analysis of the fecal and oral microbiota in chronic recurrent multifocal osteomyelitis

BACKGROUND

Chronic recurrent multifocal osteomyelitis (CRMO) is a rare autoinflammatory bone disease for which a lack of bacterial involvement is a key diagnostic feature to distinguish it from other symptomatically related diseases. However, the growing evidence suggesting an involvement of the host-associated microbiota in rheumatic disorders together with the now wide accessibility of modern culture-independent methods warrant a closer examination of CRMO.

METHODS

In this study, we show through bacterial 16S rRNA gene profiling that numerous features of the oral- and fecal microbial communities differentiate children with and without CRMO.

RESULTS

Notably, communities in diseased children are characterized by a lack of potential probiotic bacteria in the fecal community and an overabundance of known pathobionts in the oral microbial communities. Of special interest is the HACEK group, a set of commonly known oral pathogens that are implicated in the development of several acute and chronic diseases such as osteitis and rheumatoid arthritis. Furthermore, we observe that gut bacterial communities in the diseased children appear to reflect an altered host physiology more strongly than the oral community, which could suggest an oral disease origin followed by propagation and/or responses beyond the oral cavity.

CONCLUSIONS

Bacterial communities, in particular the oral microbiota, may serve as an indicator of underlying susceptibility to CRMO, or play a yet undefined role in its development.

Eikenella Corrodens Vertebral Osteomyelitis in a Young Patient With Type I Diabetes Mellitus

Vertebral osteomyelitis is an uncommon variant of osteomyelitis. Although Staphylococcus and/or Streptococcus are commonly associated, alternate pathogens have been implicated in vertebral osteomyelitis, especially in endemic areas and/or immunocompromised patients. Here, we present a case of a young African American female with type I diabetes mellitus who presented to us with worsening back pain. The MRI lumbar spine was suggestive of vertebral osteomyelitis involving the right facet joint of the fifth lumbar (L5) and the first spinal (S1) joint and a significant narrowing of the thecal sac at the L4-L5 vertebral level with an anterior epidural abscess. The patient was started on empirical antibiotics, and surgical intervention was performed with L4-L5 laminectomy and extraction of the epidural abscess. Her pus culture showed Eikenella corrodens as a possible cause of vertebral osteomyelitis. She had an uneventful recovery after two weeks of antibiotics (intravenous ceftriaxone) therapy.

Comparison of bacterial maxillary sinus cultures between odontogenic sinusitis and chronic rhinosinusitis

BACKGROUND

Bacterial odontogenic sinusitis (ODS) is distinct from other forms of rhinosinusitis. Diagnosing ODS can be challenging because of nonspecific clinical presentations and underrepresentation in the literature. The purpose of this study was to compare maxillary sinus bacterial cultures between patients with ODS and chronic rhinosinusitis (CRS), to determine whether certain bacteria are associated with ODS.

METHODS

This was a retrospective case-control study of 276 consecutive patients from August 2015 to August 2019 who underwent endoscopic sinus surgery (ESS) for bacterial ODS, CRS without nasal polyps (CRSsNP), or CRS with nasal polyps (CRSwNP). When present, pus was sterilely cultured from maxillary sinuses after maxillary antrostomy, and aerobic and anaerobic cultures were immediately sent for processing. Demographics and culture results were compared between ODS and CRS patients, and then separately between ODS and CRSsNP, and ODS and CRSwNP. ODS culture results were also compared between different dental pathologies (endodontic vs oroantral fistula).

RESULTS

The following bacteria were significantly more likely in ODS compared to CRS: mixed anaerobes, Fusobacterium spp., Eikenella corrodens, Streptococcus intermedius, Streptococcus anginosus, and Streptococcus constellatus. Staphylococcus aureus and Pseudomonas aeruginosa were inversely related to ODS. There were no significant differences in cultures between the different dental pathologies.

CONCLUSION

Certain bacteria were more likely to be associated with ODS compared to CRS when purulence was cultured from the maxillary sinus. Physicians should evaluate for an odontogenic source of sinusitis when these ODS-associated bacteria are identified in maxillary sinus cultures.

Electrospun PLA Fibers Containing Metronidazole for Periodontal Disease

Purpose

Electrospun PLA fiber devices were investigated in the form of fiber mats and disks. Metronidazole was used as an active agent; its concentration was 12.2 and 25.7 wt% in the devices.

Methods

The structure was studied by X-ray diffraction and scanning electron microscopy, drug release by dissolution measurements, while the antimicrobial efficiency was tested on five bacterial strains.

Results

The XRD study showed that the polymer was partially crystalline in both devices, but a part of metronidazole precipitated and was in the form of crystals among and within the fibers. Liquid penetration and dissolution were different in the two devices, they were faster in disks and slower in fiber mats, due to the morphology of the device and the action of capillary forces. Disks released the drug much faster than fiber mats. Although the release study indicated fast drug dissolution, the concentration achieved a plateau value in 24 hrs for the disks; the inhibition effect lasted much longer, 13 days for bacteria sensitive to metronidazole. The longer inhibition period could be explained by the slower diffusion of metronidazole located inside the fibers of the device.

Conclusion

The results suggest that the devices may be effective in the treatment of periodontitis.

Combination of Zinc Hyaluronate and Metronidazole in a Lipid-Based Drug Delivery System for the Treatment of Periodontitis

BACKGROUND

Despite being a highly prevalent disease and a possible contributor to adult tooth loss, periodontitis possesses no well-established therapy. The aim of the recent study was the development and evaluation of a mucoadhesive monophase lipid formulation for the sustained local delivery of amoxicillin, metronidazole, and/or zinc hyaluronate or gluconate.

METHODS

To investigate our formulations, differential scanning calorimetry, X-ray diffraction, swelling, erosion, mucoadhesivity, drug release, and antimicrobial measurements were performed.

RESULTS

Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) results show that the loaded drugs are in a suspended form, the softening of the formulations starts at body temperature, but a part remains solid, providing sustained release. Swelling of the lipid compositions is affected by the hydrophilic components, their concentration, and the strength of the coherent lipid structure, while their erosion is impacted by the emulsification of melted lipid components.

CONCLUSIONS

Results of drug release and antimicrobial effectiveness measurements show that a sustained release may be obtained. Amoxicillin had higher effectiveness against oral pathogens than metronidazole or zinc hyaluronate alone, but the combination of the two latter could provide similar effectiveness to amoxicillin. The applied mucoadhesive polymer may affect adhesivity, drug release through the swelling mechanism, and antimicrobial effect as well.

The oral microbiome-the relevant reservoir for acute pediatric appendicitis?

PURPOSE

The oral microbiome has been related to numerous extra oral diseases. Recent studies detected a high abundance of oral bacteria in inflamed appendices in pediatric patients. To elucidate the role of oral bacteria in acute pediatric appendicitis, we studied the oral and appendiceal microbiome of affected children compared to healthy controls.

METHODS

Between January and June 2015, 21 children undergoing appendectomy for acute appendicitis and 28 healthy controls were prospectively enrolled in the study. All individuals underwent thorough dental examination and laboratory for inflammatory parameters. Samples of inflamed appendices and the gingival sulcus were taken for 16S rDNA sequencing. RT-qPCR of Fusobacterium nucleatum, Peptostreptococcus stomatis, and Eikenella corrodens was performed and their viability was tested under acidic conditions to mimic gastric transfer.

RESULTS

In phlegmonous appendices, Bacteroidetes and Porphyromonas were discovered as dominant phylum and genus. In sulcus samples, Firmicutes and Streptococcus were detected predominantly. P. stomatis, E. corrodens, and F. nucleatum were identified in each group. Viable amounts of P. stomatis were increased in sulci of children with acute appendicitis compared to sulci of healthy controls. In inflamed appendices, viable amounts of E. corrodens and F. nucleatum were decreased compared to sulci of children with appendicitis. Postprandial viability could be demonstrated for all tested bacteria.

CONCLUSION

In children with acute appendicitis, we identified several oral bacterial pathogens. Based on postprandial viability of selected species, a viable migration from the oral cavity through the stomach to the appendix seems possible. Thus, the oral cavity could be a relevant reservoir for acute appendicitis.

Structural analysis of haemoglobin binding by HpuA from the Neisseriaceae family

The Neisseriaceae family of bacteria causes a range of diseases including meningitis, septicaemia, gonorrhoea and endocarditis, and extracts haem from haemoglobin as an important iron source within the iron-limited environment of its human host. Herein we report crystal structures of apo- and haemoglobin-bound HpuA, an essential component of this haem import system. The interface involves long loops on the bacterial receptor that present hydrophobic side chains for packing against the surface of haemoglobin. Interestingly, our structural and biochemical analyses of Kingella denitrificans and Neisseria gonorrhoeae HpuA mutants, although validating the interactions observed in the crystal structure, show how Neisseriaceae have the fascinating ability to diversify functional sequences and yet retain the haemoglobin binding function. Our results present the first description of HpuA's role in direct binding of haemoglobin.

The Neisseriaceae bacteria family extract heame from the haemoglobin of its host, the HpuA protein is part of this system. Here, the authors report crystal structures of apo- and haemoglobin-bound HpuA and analyse mutants to examine the interaction between HpuA and haemoglobin.

Morphological plasticity of Streptococcus oralis isolates for biofilm production, invasiveness, and architectural patterns

OBJECTIVE

Streptococcus oralis is an early coloniser of the oral cavity that contributes to dental plaque formation. Many different genotypes can coexist in the same individual and cause opportunistic infections such as bacterial endocarditis. However, little is known about virulence factors involved in those processes. The aim was to analyze the evolving growth of S. oralis colony/biofilm to find out potentially pathogenic features.

DESIGN

Thirty-three S. oralis isolates were analyzed for: (1) biofilm production, by spectrophotometric microtiter plate assay; (2) colonial internal architecture, by histological methods and light and electron microscopy; (3) agar invasion, by a new colony-biofilm assay.

RESULTS

S. oralis colonies showed two different growth patterns: (1) fast growth rate without invasion or minimally invasive; (2) slow growth rate, but high invasion ability. 12.1% of strains were biofilm non-producers and 24.2% not invasive, compared to 51.5% biofilm high-producers and 39.4% very invasive. Both phenotypic characteristics tended to be mutually exclusive. However, a limited number of strains (15%) co-expressed these features at the highest level.

CONCLUSIONS

Morphological plasticity of S. oralis highlighted in this study may have important ecological and clinical implications. Coexistence of strains with different growth patterns could produce a synergic effect in the formation and development of subgingival dental plaque. Moreover, invasiveness might regulate dissemination and colonisation mechanisms. Simultaneous co-expression of high-invasive and high-biofilm phenotypes gives a fitness advantage during colonisation and may confer higher pathogenic potential.

Qualitative and quantitative agar invasion test based on bacterial colony/biofilm

Invasion of the culture medium is a feature frequently studied in yeasts, in which it has been related to a greater virulence, but it is practically unknown in bacteria. Recently, it has been demonstrated that several clinically relevant bacterial species were also able of invading agar media, so it was necessary to design a microbiological assay to study the expression of this character in bacteria. Accordingly, a bacterial agar invasion test based on colony/biofilm development was designed, which allows qualitative and quantitative characterization of bacterial growth into the agar culture medium. Once the culture conditions were optimized, the test was applied to 90 strains from nine bacterial species, validating its usefulness for differentiating invasive strains (positive) from those non invasive (negative). The test also allows sorting invasive strains according to agar invasion intensity (low, moderate, high) and topographic invasion pattern (peripheral, homogeneous, mixed). Moreover, an image analysis routine to quantify the invasion was developed. Implemented method enables direct measuring of two invasion parameters (invasion area and number of invasion dots), automated calculation of three relative variables (invasion relative area, invasion dots relative density, and invasion dot average area), and the establishment of strain specific frequency histograms. This new methodology is simple, fast, reproducible, objective, inexpensive and can be used to study a great number of specimens simultaneously, all of which make it suitable for incorporation to the routine of any microbiology laboratory. It could also be a useful tool for additional studies related to clinical aspects of bacterial isolates such as virulence and antimicrobial response.

Delayed Eikenella corrodens orbital infection after fracture repair

Orbital cellulitis and abscess after fracture repair are rare. Ophthalmic infection with Eikenella species is even more unusual, but can be severe. We report a case of Eikenella corrodens infection in a 28-year-old man who underwent zygomaticomaxillary and orbital floor blowout fracture surgery 4 years before presentation. Eikenella species are often resistant to frequently used empiric antibiotics, and because of specific growth conditions, easily missed on standard cultures. Appropriate efforts should be made to identify and treat E. corrodens in atypical orbital and periocular infections.

Microbiologic changes in subgingival plaque after removal of fixed orthodontic appliances

OBJECTIVE

To evaluate changes that occur in the subgingival microbiota after removal of fixed orthodontic appliances using polymerase chain reaction (PCR).

MATERIALS AND METHODS

Thirty orthodontic patients (11 males and 19 females; aged 20 +/- 7.3 yr) were included in this study. Subgingival plaque samplings were gathered from the disto-buccal gingival crevice of the left upper central incisors and the left lower central incisors, and from the mesio-buccal gingival crevice of the left upper first molars and the left lower first molars, at two different times: 2 weeks before appliance removal (T1), and 3 months after appliance removal (T2). DNA was extracted from the samples and the 16S rRNA-based PCR detection method was used to determine the prevalence of Actinobacillus actinomycetemcomitans , Tannerella forsythia , Campylobacter rectus , Eikenella corrodens , Porphyromonas gingivalis , Prevotella intermedia , Prevotella nigrescens , and Treponema denticola , which are considered as putative periodontopathogens.

RESULTS

The frequency of positive sites at T1 and T2 was 65% and 43.3% for C. rectus , and 53.3% and 30.8% for E. corrodens , respectively. For the other bacteria, the frequency tended to be reduced between times.

CONCLUSION

Periodontopathogens during orthodontic treatment were significantly reduced within 3 months of appliance removal. However, how long it takes to return to the preorthodontic composition of the subgingival microbiota and whether it happens at all remain to be seen.

Prevalence of periodontal pathogens in coronary atherosclerotic plaque of patients undergoing coronary artery bypass graft surgery

BACKGROUND

Chronic bacterial infections have been associated with an increased risk for atherosclerosis and coronary artery disease. The ability of oral pathogens to colonize in coronary atheromatous plaque is well known. The aim of our study was to detect the presence of four common periodontal pathogens in coronary plaques. We detected the presence of 16S rRNA of Treponema denticola, Eikenella Corrodens, Porphyromonas gingivalis and Campylobacter rectus in subgingival and atherosclerotic plaques of CABG surgery by using Polymerase Chain Reaction.

METHODS

51 patients in the age group of 40 to 80 years with chronic periodontitis were recruited for the study. These patients were suffering from Coronary Artery Disease (CAD) and underwent Coronary Artery Bypass Grafting (CABG). DNA was extracted from the subgingival plaque and coronary atheromatous plaque samples. Universal Primer for the general detection of bacterial DNA and the primers for T.denticola, E. Corrodens, C.rectus and P.gingivalis were used to amplify part of 16SrRNA gene by Polymerase Chain Reaction.

RESULTS

T.denticola, E.corrodens, C.rectus and P.gingivalis were detected in 49.01 %, 27.45 %, 21.51% and 45.10% of atherosclerotic plaque samples. In both subgingival and coronary plaque samples, T. denticola was detected in 39.21% of the cases, E.corrodens in 19.60%, C.rectus in 11.76% and P.gingivalis in 39.22% of the cases respectively.

CONCLUSION

Our study revealed the presence of significant bacterial DNA of oral pathogens in coronary plaques. This suggests possible relationship between periodontal infection and atherosclerosis and can help devise preventive treatment strategies.

Purification and partial characterization of a bacteriocin produced by Eikenella corrodens

AIMS

The purpose of this study was to purify and characterize a bacteriocin produced by Eikenella corrodens A32E2.

METHODS AND RESULTS

Peptostreptococcus anaerobius ATCC27337 was used as indicator strain in antagonistic assays for bacteriocin-producing E. corrodens A32E2. Protein extraction was influenced by pH and buffer composition. The protein was active in the pH range 6-8. Inhibitory activity was lost by both heating and treatment with proteolytic enzymes and decreased with organic solvents. The substance is rather unstable but maintains 100% of its activity after being exposed to acetone and when stored at -70 degrees C. The antagonistic substance was first precipitated by ammonium sulfate and further partially purified by Mono-Q FPLC and C-18 HPLC. Mass spectrometry analysis showed that the molecular mass was 23 625 Da, and the sequence obtained for the N-terminus was: Met-Asn-Phe-Asp-Glu-Lys-Val-Gly-Lys-Val-X-Phe-Lys-Val-Gly-Asp.

CONCLUSIONS

The evidence presented in this study supports the idea that an antagonistic substance produced by E. corrodens A32E2 isolated from a periodontal diseased site is a novel bacteriocin, which we designate corrodecin.

SIGNIFICANCE AND IMPACT OF THE STUDY

We anticipated that corrodecin might play an important role at the periodontal site. This compound could also be attractive in biotechnological applications as an interesting tool for oral ecosystem control.

Culture-independent detection of Eikenella corrodens and Veillonella parvula in primary endodontic infections

Eikenella corrodens and Veillonella parvula are normal cultivable inhabitants of the oral cavity but their presence in endodontic infections has not been as common as it could be anticipated. This might have been because of shortcomings of culture techniques when it comes to bacterial isolation or identification. The present study intended to survey samples from primary endodontic infections for the presence of E. corrodens and V. parvula using a culture-independent 16S rRNA gene-based nested PCR protocol. Genomic DNA was isolated directly from samples taken from different forms of periradicular lesions, and the presence of E. corrodens and V. parvula was determined by nested PCR. Specificity for each primer pair was confirmed by sequence analysis of PCR products from positive clinical samples. V. parvula and E. corrodens were, respectively, detected in 33% and 14% of the root canals associated with chronic apical periodontitis. Both V. parvula and E. corrodens were found in 10% of the cases diagnosed as acute apical periodontitis. V. parvula and E. corrodens were detected in 21% and 26% of the samples from acute apical abscesses, respectively. In general, species-specific nPCR allowed the detection of V. parvula in 24% and E. corrodens in 18% of the samples taken from primary endodontic infections. Findings confirmed that V. parvula and E. corrodens can take part in the microbiota of primary endodontic infections, but in prevalence values somewhat higher when compared to most of the previous culture studies that had reported recovery of these species.

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.

Enteropathogens associated with cases of gastroenteritis in a rural population in Jordan

Stool specimens were collected from 180 patients belonging to a population of recently settled Bedouins in Jordan who presented with acute or persistent diarrhoea and other symptoms, and from 100 non-diarrhoeal controls. All samples were examined for parasites and bacterial pathogens by culture and PCR. Bacterial isolates were tested for their susceptibility to common antimicrobial agents. Pathogens and potential enteropathogens were identified from 140 (77.8%) of the patients, with more than one pathogen being recovered from 67 (37.2%) patients. Potentially pathogenic parasites were observed in 90 (50%) patients; those that were associated significantly with diarrhoea were Giardia lamblia, Blastocystis hominis, Cryptosporidium spp., Entamoeba histolytica and Cyclospora cayetanensis. Pathogenic bacteria were isolated from 72 (40%) patients, and, of these, 62.5% were resistant to at least one antibiotic, and 30.6% of these were multiresistant. Diarrhoeagenic Escherichia coli strains were found in 14.3% of the patients and 2.9% of the control subjects (not statistically significant). The most common enteropathogenic bacteria found were Shigella spp., Campylobacter jejuni and Yersinia enterocolitica. Unusual bacterial species were the predominant organisms recovered in a few cases and could represent a possible cause of diarrhoea. Overall, there was a high endemicity of diarrhoeal disease in the area studied. Risk factors that correlated significantly with contracting diarrhoea were socio-economic status, education, use of unchlorinated well or tank water, and a low level of personal hygiene.

Clonal diversity and stability of subgingival Eikenella corrodens

Eikenella corrodens is a commensal subgingival bacterium commonly found in both periodontally nondiseased and diseased subjects. The present study examined the clonal diversity and stability of subgingival E. corrodens over time. Ninety-five subjects were enrolled at the baseline examination, including 44 periodontally nondiseased subjects and 51 subjects with aggressive periodontitis. Twenty-two nondiseased subjects and 11 subjects with aggressive periodontitis were subsequently reexamined after an average interval of 14 months. Two subgingival plaque samples were obtained from each subject to determine the total cultivable bacteria. In addition, multiple E. corrodens isolates from each sample were recovered for clonal analysis by arbitrarily primed PCR. The mean numbers of distinct E. corrodens clones harbored by nondiseased subjects and subjects with aggressive periodontitis were 1.3 and 3.0, respectively. Thirty-nine percent of the nondiseased subjects and 63% of the subjects with aggressive periodontitis harbored multiple clones of E. corrodens. The numbers of distinct E. corrodens clones increased significantly (Mann-Whitney ranking test, P < 0.05) in sites from patients with aggressive periodontitis, in sites with pocket depths of 4 mm or greater, in sites with a clinical attachment loss of 2 mm or greater, and in sites coinfected with Porphyromonas gingivalis. Comparison of E. corrodens clones recovered at the baseline and those recovered at the follow-up examination showed that E. corrodens colonization was not stable. Thirty-eight of the 66 follow-up samples (58%) showed a complete change (including de novo colonization of the sites or complete elimination of the organism from the sites) of the subgingival E. corrodens clonal types between the baseline and the follow-up examinations. Our results suggest a complexity of subgingival microbiota not seen previously.

Microbiological shifts in intra- and extraoral habitats following mechanical periodontal therapy

OBJECTIVES

The aim of the present study was to analyze the intra- and extraoral colonization dynamics of periodontal pathogens following supra- and subgingival debridement.

MATERIAL AND METHODS

Thirty five patients with chronic periodontitis were enrolled in the study. Supra- and subgingival plaque samples, saliva, and swab samples from mucosa and extraoral sites were taken at baseline and 6 weeks, 3 months and 6 months after mechanical periodontal therapy. Actinobacillus actinomycetemcomitans (Aa), Porphyromonas gingivalis (Pg), Eikenella corrodens (Ec), Tannerella forsythensis (Tf), Prevotella intermedia (Pi), Prevotella nigrescens (Pn), and Treponema denticola (Td) were identified by PCR.

RESULTS

Supra- and subgingival debridement decreased the number of subgingival sites infected with the analyzed pathogens only transiently, if at all. However, the detection frequencies of Tf, Td, Ec, Pi, and Pn in the supragingival region, of Pg, Td, and Pn at the oral mucosa sites (mostly the tongue), and of all pathogens except Aa in saliva increased over the 6-month observation period. Td was the only pathogen recorded in notable quantities in the extraoral habitat (external ear canal).

CONCLUSION

The results indicate that supra- and subgingival debridement results in a dissemination of periodontal pathogens within the oral cavity.

Characterization and expression of adjacent proline iminopeptidase and aspartase genes from Eikenella corrodens

Two adjacent genes involved in nitrogen metabolism from Eikenella corrodens, with a potential role in pathogenesis, were studied. Proline iminopeptidase (Pip) activity, which may be essential for energy production and protection against host immune mechanisms, is exhibited by E. corrodens. Analysis of Pip-expressing clones revealed an ORF of 939 bases with a predicted amino acid sequence identity of 67% to the Pip of Neisseria gonorrhoea. 200 bp downstream from pip, an ORF of 1395 bases, encoding a protein with 87% identity to a putative aspartase from the Neisseria meningitidis genome sequence, was identified. Enzymatic function was confirmed with a complemented Escherichia coli aspartase deficient mutant. The E. corrodens aspartase was found to be 77% identical to the Haemophilus influenzae aspartase sequence, which was originally identified on the basis of its ability to bind plasminogen. However, the E. corrodens aspartase had no such activity. Southern hybridization indicated both genes to be single copy and conserved within the genomes of a diverse panel of E. corrodens isolates from health and disease.

In vitro activities of tigecycline (GAR-936) and 12 other antimicrobial agents against 90 Eikenella corrodens clinical isolates

The activity of tigecycline was compared with those of other antimicrobials against 90 isolates of Eikenella corrodens. The MIC at which 90% of the isolates were inhibited was 2 micro g/ml for tigecycline and 1, </=0.5/0.25, 0.5, </=0.12, </=2, and 0.5 micro g/ml for ampicillin, amoxicillin-clavulanate, cefotaxime, imipenem, chloramphenicol, and ciprofloxacin, respectively.

N-acetyl-D-galactosamine specific lectin of Eikenella corrodens induces intercellular adhesion molecule-1 (ICAM-1) production by human oral epithelial cells

During the acute inflammatory response in periodontitis, gingival epithelial cells are considered to play important roles in the recruitment of inflammatory cells to the site of infection through the secretion of chemokines. However, little is known about the expression of molecules that are involved in the interaction between the epithelium and neutrophils following bacterial attachment. Earlier work reported that periodontopathogenic Eikenella corrodens strain 1,073 up-regulated the expression and secretion of chemokines such as interleukin-8 (IL-8) from KB cells (a human oral epithelial cell line derived from a human oral epidermoid carcinoma). To elucidate the mechanism of the transmigration of neutrophils through the epithelium, the present study investigated the expression of adhesion molecules on KB cells in response to E. corrodens attachment. Adhesion molecule gene expression was assessed by RT-PCR and adhesion proteins expressed on KB cell surfaces were determined by cell-based ELISA and FACS. In RT-PCR, ICAM-1 mRNA levels were significantly increased within 1 h in response to exposure to E. corrodens and continued to increase over the 12-h period of study. In ELISA, increased surface ICAM-1 expression was paralleled by increased ICAM-1 mRNA levels. Furthermore, the increases in ICAM-1 expression on epithelial cells infected with E. corrodens were observed to be due to the N-acetyl-D-galactosamine (GalNAc) specific bacterial lectin-like substance of E. corrodens (EcLS), which was one of the adhesins of E. corrodens. This is the first study to report that a bacterial lectin-like substance increased the expression of ICAM-1 on gingival epithelial cells.

The aerobic electron transport system of Eikenella corrodens

The respiratory system of the fastidious beta-proteobacterium Eikenella corrodens grown with limited oxygen was studied. Membranes showed the highest oxidase activity with ascorbate plus N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) or succinate and the lowest activity with NADH and formate. The presence of a bc1-type complex was suggested by the inhibition exerted by 2-heptyl-4-hydroxyquinoline-N-oxide (HOQNO), myxothiazol, and antimycin A on respiration with succinate and by the effect of the latter two inhibitors on the succinate-reduced difference spectra. Respiration with succinate or ascorbate-TMPD was abolished by low KCN concentrations, suggesting the presence of a KCN-sensitive terminal oxidase. Cytochromes b and c were spectroscopically detected after reduction with physiological or artificial electron donors, whereas type a and d cytochromes were not detected. The CO difference spectrum of membranes reduced by dithionite and its photodissociation spectrum (77 K) suggested the presence of a single CO compound that had the spectral features of a cytochrome o-like pigment. High-pressure liquid chromatography analysis of membrane haems confirmed the presence of haem B; in contrast, haems A and O were not detected. Peroxidase staining of membrane type c cytochromes using SDS-PAGE revealed the presence of five bands with apparent molecular masses of 44, 33, 30, 26, and 14 kDa. Based on our results, a tentative scheme of the respiratory chain in E. corrodens, comprising (i) dehydrogenases for succinate, NADH, and formate, (ii) a ubiquinone, (iii) a cytochrome bc1, and (iv) a type-cbb' cytochrome c oxidase, is proposed.

Eikenella corrodens in subgingival plaque: relationship to age and periodontal condition

BACKGROUND

The purpose of this study was to determine the prevalence and distribution of Eikenella corrodens (E. corrodens) in subgingival plaque in different age and periodontitis groups and to examine whether its presence is related to periodontal diseases.

METHODS

A total of 273 subgingival plaque samples from 213 periodontitis patients and 60 healthy subjects were assessed. Smears from each plaque sample were made and E. corrodens was detected by means of indirect immunofluorescent technique. Mean percentage of E. corrodens per total bacteria (distribution) was calculated in each sample. The prevalence (% of positive samples) and distribution of E. corrodens were statistically analyzed based on age or diagnosis by means of Fisher's exact test and analysis of variance (ANOVA).

RESULTS

Prevalence of E. corrodens decreased by age in the healthy control group; however, prevalence did not change in periodontitis groups. Distribution of E. corrodens was highest in juvenile periodontitis (JP) (2.3 +/- 1.5%) followed by post-JP (1.7 +/- 2.1%), prepubertal periodontitis (1.4 +/- 1.1%), rapidly progressive periodontitis (0.8 +/- 0.7%), adult periodontitis (0.7 +/- 0.6%), and healthy subjects (0.3 +/- 0.3%) (ANOVA, P<0.0001). The <20-year-old age group with periodontitis showed the highest distribution of E. corrodens (2.2 +/- 1.6%) compared to the older age groups who were either healthy or had periodontitis (ANOVA, P<0.0001).

CONCLUSIONS

Since the distribution of E. corrodens is significantly higher in JP, post-JP, and PP, E. corrodens might play an important role in the occurrence or progression of periodontitis in young patients.

In vitro activities of a new des-fluoroquinolone, BMS 284756, and seven other antimicrobial agents against 151 isolates of Eikenella corrodens

The des-fluoroquinolone BMS 284756 was active in vitro against all 151 clinical strains of Eikenella corrodens at a MIC of < or = 0.25 microg/ml and was comparable in activity to moxifloxacin and levofloxacin. The MIC at which 90% of the isolates were inhibited by penicillin G was 2 microg/ml; MICs for 8.6% of the strains (13 of 151) were > or = 4 microg/ml, including for two beta-lactamase-producing isolates. Amoxicillin-clavulanate and ampicillin-sulbactam inhibited all strains at a MIC of < or = 1 microg/ml.

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.

Susceptibilities of Eikenella corrodens, Prevotella intermedia, and Prevotella nigrescens clinical isolates to amoxicillin and tetracycline

The AB Biodisk Etest showed that 106 (100%) and 98 (92%) isolates of Eikenella corrodens were susceptible to amoxicillin and tetracycline, respectively. Twenty-three (68%) Prevotella intermedia isolates and 14 (67%) Prevotella nigrescens isolates were susceptible to amoxicillin. Seventy-nine percent of the P. intermedia isolates and 67% of the P. nigrescens isolates were susceptible to tetracycline. A higher percentage of beta-lactamase-producing isolates of P. intermedia and P. nigrescens were identified with selective agar containing amoxicillin than with nonselective agar.

Soluble products from Eikenella corrodens stimulate oral epithelial cells to induce inflammatory mediators

In the inflammatory response elicited by bacterial colonization in periodontal pockets, pocket epithelial cells not only serve as a barrier to isolate the pocket microenvironment from external stimuli but also regulate the functions of neighboring cells including fibroblasts and inflammatory cells. To elucidate this mechanism, we characterized the effects of periodontopathic bacterium Eikenella corrodens 1073 components on the production of some inflammatory mediators in a human oral epithelial cell line (KB). In enzyme-linked immunosorbent assay (ELISA), the E. corrodens supernatant induced interleukin-6 (IL-6), IL-8 and prostaglandin E2 but not interferon-gamma (IFN-gamma) production by KB cells. After incubation with E. corrodens supernatant, KB cells showed a marked increase in the levels of IL-6, IL-8 and PG G/H synthase (cyclooxygenase)-2, but not IFN-gamma, gene expression by reverse-transcriptase polymerase chain reaction. All these E. corrodens products responsible for production of these inflammatory mediators resisted freezing and boiling and were present in a 10-kDa filtrate. These results imply that these soluble small-molecular-mass products from E. corrodens stimulate various inflammatory mediator productions by human oral epithelial cells and may play a role in the initiation of periodontal inflammation and subsequently perpetuate the inflammatory response during chronic infection.

Role of the Eikenella corrodens pilA locus in pilus function and phase variation

The human pathogen Eikenella corrodens expresses 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 pilus structure and function in the clinical isolate E. corrodens VA1. Earlier work defined the pilA locus which includes pilA1, pilA2, pilB, and hagA. Both pilA1 and pilA2 predict a type IV pilin, whereas pilB predicts a putative pilus assembly protein. The role of hagA has not been clearly established. That work also confirmed that pilA1 encodes the major pilus protein in this strain and showed that the phase variation involves a posttranslational event in pilus formation. In this study, the function of the individual genes comprising the pilA locus was examined using a recently developed protocol for targeted interposon mutagenesis of S-phase variant VA1-S1. Different pilA mutants were compared to S-phase and L-phase variants for several distinct aspects of phase variation and type IV pilus biosynthesis and function. S-phase cells were characterized by surface pili, competence for natural transformation, and twitching motility, whereas L-phase cells lacked these features. Inactivation of pilA1 yielded a mutant that was phenotypically indistinguishable from L-phase variants, showing that native biosynthesis of the type IV pilus in strain VA1 is dependent on expression of pilA1 and proper export and assembly of PilA1. Inactivation of pilA2 yielded a mutant that was phenotypically indistinguishable from S-phase variants, indicating that pilA2 is not essential for biosynthesis of functionally normal pili. A mutant inactivated for pilB was deficient for twitching motility, suggesting a role for PilB in this pilus-related phenomenon. Inactivation of hagA, which may encode a tellurite resistance protein, had no effect on pilus structure or function.

Profile of subgingival microbiota in children with mixed dentition

A diversity of microbial species has been detected in children's oral flora at an early age. To investigate the composition of the subgingival microbiota of different groups of teeth in children with mixed dentition, 40 systemically healthy children, aged 7-8 years, randomly chosen, were examined. Subgingival plaque samples were taken from the mesiobuccal sites of 21, 41, 16 and 36 permanent teeth and 53, 73, 64 and 84 deciduous teeth. The samples were cultured for bacterial isolation anaerobically and in 10% CO2 plus air using selective and nonselective media. Forty-five different microbial species were isolated from both permanent and deciduous teeth. Streptococcus sanguis (79-70%), Streptococcus mitis (66-65%), Prevotella melaninogenica (51-57%), Eikenella corrodens (51-52%), Capnocytophaga gingivalis (46-34%), Capnocytophaga ochracea (45-45%), Actinomyces naeslundii (39-60%) and Prevotella intermedia (42-35%) were among the most frequently detected species in permanent and deciduous teeth respectively. Several suspected periodontal pathogens, such as Porphyromonas gingivalis, Prevotella loescheii, Campylobacter gracilis, Bacteroides forsythus, Campylobacter concisus, Peptostreptococcus micros and Selenomonas sputigena, albeit less frequently detected, were present in the microbiota of these children. The bacterial species Streptococcus constellatus, Peptostreptococcus micros, Pseudoramibacter alactolyticus, E. corrodens and Fusobacterium nucleatum were associated with non-bleeding permanent and deciduous teeth whereas Streptococcus intermedius, C. concisus, P. intermedia and P. loescheii were associated with bleeding.

Oral flora and pathogenic organisms

Oral microbial flora consist of numerous bacterial taxa, ranging from aerobes through fastidious anaerobes, and fungi, viruses, and protozoa. Many of these bacteria are unique to the oral cavity. The organisms exist in a complex interrelationship that is regulated and maintained by physical and metabolic microbial interactions, and by environmental factors, such as saliva and diet. Many of these organisms are relatively harmless, although others are significant pathogens, producing local and systemic diseases in healthy and compromised individuals.

Microbiological response of localized sites with recurrent periodontitis in maintenance patients treated with tetracycline fibers

BACKGROUND

Whether adjunctive tetracycline fibers can provide an additive effect to scaling and root planing in treating non-responsive sites in maintenance subjects is still controversial. Recolonization of the bacteria from untreated sites or from the extracrevicular region may explain the insignificant response to local therapy. The purpose of the present study was to evaluate the microbiological response of sites treated with tetracycline fibers combined with scaling and root planing.

METHODS

The study was conducted in a split-mouth design. Thirty patients on maintenance therapy having at least 2 non-adjacent sites in separate quadrants with probing depths between 4 to 8 mm with bleeding on probing, or aspartate aminotransferase enzyme levels > 800 microIU in the gingival crevicular fluid, were treated with scaling and root planing plus tetracycline fibers or with scaling and root planing only. Subgingival plaque samples were collected at baseline, and 1, 3, and 6 months following treatment. A. actino-mycetemcomitans, C. rectus, B. forsythus, E. corrodens, F. nucleatum, P. gingivalis, and P. intermedia were detected by culture, immunofluorescence, or PCR technique.

RESULTS

There was a reduction of total bacterial cell count, as well as of certain periodontal pathogens, following treatment. The prevalence of A. actinomycetemcomitans, B. forsythus, and P. gingivalis and the mean proportions of C. rectus, P. intermedia, F. nucleatum, and P. gingivalis decreased after therapy, but there was no statistically significant difference between the 2 treatment groups with respect to bacterial proportions or the number of positive sites. Besides, the pathogens could not be eliminated from the periodontal pocket, and recolonization of the pocket was noted at 3 months post-treatment.

CONCLUSIONS

Bacteria located within the cheek, tongue mucosa, saliva, or untreated sites may contribute to reinfection of the pockets and explain the insignificant response to local tetracycline therapy.

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.

Interleukin-6 (IL-6) and IL-8 are induced in human oral epithelial cells in response to exposure to periodontopathic Eikenella corrodens

Periodontitis is the inflammatory response in periodontal tissues elicited by bacterial colonization in periodontal pockets. In this response, pocket epithelial cells are the first cells to come into contact with bacteria. To elucidate this mechanism, we determined the adherence of the periodontopathic bacterium Eikenella corrodens 1073, which has a GalNAc-sensitive lectin-like adhesin (EcLS), to a human oral epithelial carcinoma cell line (KB) and the induction of proinflammatory cytokine production in the cells following exposure to this bacterium in vitro. In the adherence assay, EcLS played a role as the adhesin of this bacterium in adherence to KB cells. In a reverse transcriptase PCR, significant interleukin-8 (IL-8) and IL-6 mRNA levels were induced in response to exposure to this bacterium. In an enzyme-linked immunosorbent assay after an 8-h bacterial exposure, the IL-8 and IL-6 protein levels were 13.5- and 8.3-fold higher than those in the nonexposed controls, respectively. These protein responses were time dependent. Interestingly, when E. corrodens was separated from KB cells by cell culture inserts, a slight stimulation of the IL-6 and IL-8 mRNA and secreted protein levels was seen. These results imply that the direct contact of E. corrodens 1073 with oral epithelial cells is not necessarily required for the stimulation of IL-6 and IL-8 secretion. We suggest that E. corrodens induces the epithelial cells to secrete proinflammatory cytokines which serve as an early signaling system to host immune and inflammatory cells in underlying connective tissues.

Variable serum immunoglobulin G immune response to genetically distinct Eikenella corrodens strains coexisting in the human oral cavity

This study examined the variable serum immunoglobulin G (IgG) levels to genetically distinct autologous Eikenella corrodens strains by enzyme-linked immunosorbent assay (ELISA). Twenty subjects, including 10 adult periodontitis patients, 5 juvenile periodontitis patients and 5 periodontally healthy subjects were examined. Each subject was colonized by 2-8 genetically distinct E. corrodens strains. The serum IgG levels to autologous E. corrodens within individuals were significantly different in 7 adult periodontitis patients, 4 juvenile periodontitis patients and a periodontally healthy subject. Poor correlation was found in diseased subjects between serum IgG levels to autologous strains and to reference strains ATCC 23834 or FDC 373. Four adult periodontitis patients and two juvenile periodontitis patients exhibited significant serum IgG levels to autologous E. corrodens strains (two standard deviations above the mean for periodontally healthy subjects); two of these six diseased subjects exhibited low serum IgG levels to reference strains and would have been classified as low immune responders if only reference strains had been used in ELISA. This study showed the importance of using autologous E. corrodens strains in the assessment of serum IgG immune responses to this organism.

Oral food consumption and subgingival microorganisms: subgingival microbiota of gastrostomy tube-fed children and healthy controls

This study examined the effect of oral food consumption on the prevalence and levels of subgingival bacteria and yeasts in 20 gastrostomy tube-fed children and 24 healthy controls. Microbial identification was carried out using anaerobic culture and 16S rRNA-based PCR identification methods. Streptococcal and Actinomyces species were recovered from 100% and 76% of all subjects and averaged 66% and 11% of total cultivable organisms, respectively. In decreasing order of prevalence, Fusobacterium, enteric rods, Prevotella intermedia/Prevotella nigrescens, Capnocytophaga, Propionibacterium, yeasts, Actinobacillus actinomycetemcomitans, coagulase-negative Staphylococcus, Campylobacter rectus, Bacteroides forsythus, and Porphyromonas gingivalis were detected in 48% to 2% of the study subjects. The cultivable levels of these species varied widely among subjects. PCR detection showed C. rectus and Eikenella corrodens both to occur in 93% of the study subjects and to be the most prevalent putative periodontal pathogens examined. In decreasing order of prevalence, PCR identified Treponema denticola, A. actinomycetemcomitans, P. nigrescens, P. intermedia, B. forsythus, and P. gingivalis in 38% to 21% of the subjects studied. Tube-fed children and healthy controls exhibited similar subgingival microbial compositions. It appears from this study that oral food consumption is not a major determinant for the establishment of subgingival microbiota in children.

Microbial ecology of Actinobacillus actinomycetemcomitans, Eikenella corrodens and Capnocytophaga spp. in adult periodontitis

Information on intraoral distribution of putative periodontal pathogens might be essential for controlling different forms of periodontal disease. Colonization may be either promoted or impeded by other bacteria competing in the subgingival ecosystem. In recent investigations microbial associations between dental organisms have been determined in a multitude of subgingival plaque samples within multiple patients and described by odds ratios, in most circumstances without taking into account the correlated structure of the observations within a single individual. The present investigation had 3 major objectives: (i) to describe the intraoral distribution of some facultatively anaerobic, Gram-negative rods, i.e. Actinobacillus actinomycetemcomitans, Eikenella corrodens-like organisms and Capnocytophaga spp., in a multitude of subgingival and extracrevicular samples of 10 adult subjects with A. actinomycetemcomitans-associated periodontitis; (ii) to analyse possible inconsistencies of microbial associations between these periodontal organisms; and (iii) to determine factors increasing the likelihood of isolating these bacteria in a given subgingival site by employing Generalized Estimation Equation (GEE) methods. Clinical examinations were carried out at 6 sites of every tooth present. In each subject, 13 extracrevicular (2 cheek mucosa, 3 tongue, 4 gingival, 2 tonsillar samples, 1 palatinal, 1 saliva sample) and between 22 and 44 subgingival samples from deepest sites of every tooth present (n = 296) were selectively cultivated for A. actinomycetemcomitans, E. corrodens and Capnocytophaga spp. In extracrevicular material, A. actinomycetemcomitans, Capnocytophaga spp. and E. corrodens were isolated in 9, 10 and 6 patients, and from 65, 82 and 15% samples, respectively. The organisms were recovered from 51, 62 and 27% subgingival plaque samples, respectively. Heterogeneity tests did not reveal significant inconsistencies of microbial associations between bacteria in subgingival plaque. Mantel-Haenszel's odds ratios ranged between 2.0 for A. actinomycetemcomitans and Capnocytophaga spp. and 18.7 for Capnocytophaga spp. and E. corrodens. An exchangeable working dependence structure was employed in the GEE approach. The odds of isolating A. actinomycetemcomitans was increased by factor 3.7 in 4-6 mm deep pockets, and 9.5 in > or = 7 mm deep pockets. The odds of presence of E. corrodens was increased by factor 10.8 in the case of presence of Capnocytophaga spp. and 2.1 in the case of presence of A. actinomycetemcomitans. Capnocytophaga spp. were associated with bleeding on probing and molar sites. Presence of E. corrodens was associated with clinical attachment loss but not periodontal probing depth. Results of the present study indicated an association of A. actinomycetemcomitans with periodontal pathology. Whereas this organism and Capnocytophagae were widely distributed in extracrevicular ecosystems of the mouth, E. corrodens only occasionally appeared in saliva or on mucous membranes of the oral cavity. In general, GEE methods seem to allow to determine factors associated with the presence of periodontal organisms in a multivariate approach and considering the correlated structure of the data.

Clonal diversity of oral Eikenella corrodens within individual subjects by arbitrarily primed PCR

The genetic diversity of 205 Eikenella corrodens isolates recovered from dental plaque, mucosal surfaces, and saliva of 24 subjects was examined by arbitrarily primed PCR. Twenty-two subjects were colonized by multiple clones (range, two to eight; mean, 3.7). This study demonstrates the utility of arbitrarily primed PCR for clonal analysis of E. corrodens and the multiclonal colonization of E. corrodens in the oral cavity.

Energy production and peptidase activity in Eikenella corrodens

Eikenella corrodens 33EK(L), a clinical isolate, was assayed for its ability to utilise amino acids as substrates in the reduction of nitrate to nitrite. The metabolism of proline, glutamate, serine and glutamine was found to result in relatively high rates of nitrate reduction. The ability of cells to metabolise these amino acids from a variety of small peptides was also determined. E. corrodens was found to possess a relatively specific proline aminopeptidase as well as a putative carboxypeptidase activity for glutamate. Energy production in this organism appears to be via oxidative deamination of these key amino acids linked to a respiratory chain, with nitrate acting as the ultimate electron acceptor.

An Eikenella corrodens toxin detected by plaque toxin-neutralizing monoclonal antibodies

Bacterial plaque from the gingival region of teeth contains cytotoxic agents which lyse undifferentiated human HL60 cells. A small panel of monoclonal antibodies (MAbs) was found to abrogate much of this activity and to detect antigens in certain strains of Streptococcus mitis and Eikenella corrodens. The aim of this study was to determine whether these bacterial antigens might be involved in HL60 cells cytolysis. Saline extracts were obtained by homogenizing washed, stationary-phase cells in 65 mM NaCl with a tight-fitting Potter-Elvehjem homogenizer. The extracts of E. corrodens were toxic to HL60 cells, whereas similar extracts of S. mitis were nontoxic. Adding plaque toxin-neutralizing MAb 3hE5 blocked the toxic effect of E. corrodens extract S. mitis extracts contained a single, strongly reactive antigen of 140 kDa (s140K antigen) detected on Western blots (immunoblots) by three MAbs from the panel. Rabbit antibodies raised to this antigen excised from the gel (anti-s140K serum) detected larger antigens in addition to s140K. E. corrodens extracts contained a number of antigens detected by the MAbs. Immunoglobulin G (IgG) was purified from anti-s140K serum by passage through DE52 cellulose. A 100-fold excess (by weight) of the purified IgG to E. corrodens protein specifically cross-precipitated an 80-kDa antigen plus a nonantigenic 16-kDa protein, presumably attached noncovalently. The remaining supernatant fraction had no toxic activity. A similar ratio of control IgG (from nonimmunized rabbits) did not precipitate these proteins, and the supernatant fraction had the same activity as the extract not treated with IgG. The proteins of 80 and 16 kDa were also detected in the anti-s140K immunoprecipitate by rabbit IgG antibodies to E. corrodens whole cells. The 80-kDa antigen, alone or complexed with the 16-kDa protein, may be involved in mediating the toxic activity in E. corrodens and plaque extracts.

Purification and characterization of Eikenella corrodens type IV pilin

Eikenella corrodens is a gram-negative human pathogen associated with periodontal diseases and soft-tissue infections. Pilin was purified by association-dissociation and fast protein liquid chromatography; it had an apparent molecular mass of about 14.8 kDa and an N-terminal amino acid sequence reflective of type IV pilins. Antibodies to the purified protein reacted with pili on whole cells. This is the first report of purification of type IV pili/pilin from this organism. Other type IV pili are important virulence factors; we are currently investigating the biological role of pili in E. corrodens.

Actinobacillus actinomycetemcomitans genotypes in relation to serotypes and periodontal status

Actinobacillus actinomycetemcomitans is prevalent in periodontitis but is found in some periodontally healthy individuals as well. The arbitrarily primed polymerase chain reaction (AP-PCR) was used to fingerprint clinical A. actinomycetemcomitans isolates of different serotypes to determine the association between individual clonal types and periodontal conditions. Fifteen different AP-PCR genotypes were distinguished among 93 A. actinomycetemcomitans isolates from 86 uncohabiting individuals with adult periodontitis, localized juvenile periodontitis or no periodontal destruction. The 3 most common AP-PCR genotypes accounted for 68% of the isolates. Seven of the remaining AP-PCR genotypes were found only in periodontitis. The isolates of a given AP-PCR genotype usually belonged to the same serotype. The distribution of the AP-PCR genotypes among serotype b isolates seemed to differ among the subject groups. The results revealed a major genetic dissimilarity between A. actinomycetemcomitans serotypes and suggested a relationship between some A. actinomycetemcomitans clones and periodontal disease.