An evaluation of bacterial contamination of barriers used in periapical tissue regeneration: Part 1--Bacterial adherence

OBJECTIVE

To compare the adherence of Prevotella melaninogenica and Enterococcus faecalis to 3 guided tissue regeneration membranes: Atrisorb, Lambone, and OsseoQuest. It was hypothesized that OsseoQuest would show increased bacterial adherence compared to Lambone and Atrisorb.

METHOD AND MATERIALS

The barriers were suspended in trypticase soy broth containing an inoculum of either P melaninogenica or E faecalis. The samples were incubated under appropriate conditions for 6, 24, and 48 hours. Following incubation, each membrane was mixed in fresh media in a vortex machine to dislodge adherent bacteria. The vortexed media was quantitatively assessed using serial dilutions for viable cell count.

RESULTS

E faecalis exhibited higher adherence compared to P melaninogenica with time. Of the membranes tested, Lambone displayed the least bacterial adherence.

CONCLUSION

An analysis of the results indicated that bacterial adherence was time-dependent for all membranes. Membrane structure, chemical configuration, hydrophobicity, and bacterial cell surface structure were suggested as factors contributing to variance in bacterial adherence.

Mechanism of oxidative DNA damage induction in a strict anaerobe, Prevotella melaninogenica

We investigated the mechanism of the oxidative DNA damage induction by exposure to O(2) in Prevotella melaninogenica, a strict anaerobe. Flow cytometry with hydroethidine and dichlorofluorescein diacetate showed that O(2) exposure generated O(2)*-) and H(2)O(2). Results of electron spin resonance with alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone and ethanol showed that O(2) exposure also induced *OH radical generation in P. melaninogenica loaded with FeCl(2) but not in samples without FeCl(2) loading. In P. melaninogenica, O(2) exposure increased 8-hydroxydeoxyguanosine (8OHdG), typical of oxidative DNA damage. Catalase inhibited the increase, but the *OH radical scavengers did not. Phenanthroline, a membrane-permeable Fe and Cu chelator, increased the 8OHdG induction. In FeCl(2)-loaded samples, induction of 8OHdG decreased. Addition of H(2)O(2) markedly increased 8OHdG levels. These results indicate that in P. melaninogenica, exposure to O(2) generated and accumulated O(2)* and H(2)O(2), and that a crypto-OH radical generated through H(2)O(2) was the active species in the 8OHdG induction.

A hemagglutinating variant of Prevotella melaninogenica isolated from the oral cavity

Strains resembling Prevotella melaninogenica were isolated from healthy subjects and patients with periodontal disease and were identified using: a 5-test phenotypic screen; commercial identification kits; and a 16S rRNA-based polymerase chain reaction (PCR) method. Eleven clinical isolates closely resembling P. melaninogenica, and all from patients with periodontitis, were able to agglutinate erythrocytes. In the electron microscope, hemagglutinating isolates showed fimbria-like structures, that were not seen on non-hemagglutinating isolates. Some strains were further classified with PCR-restriction fragment-length polymorphism (RFLP) of 16S rRNA genes. Amplified 16S rDNA was digested using five different endonucleases, separated with agarose gel electrophoresis, stained and photographed. Photographs were then scanned, digitized and a distance matrix calculated using Dice coefficient, where the presence or absence of a band was used as a character. The distance matrix was plotted as a phenogram. At 70% similarity six clusters were seen. Type strains of separate Prevotella species did not fall into any cluster. Hemagglutinating isolates fell into three clusters: four clustered with the type strains of P. melaninogenica and Prevotella veroralis; four with other P. melaninogenica isolates and two hemagglutinating isolates clustered together Prevotella loescheii. The PCR-RFLP results showed that the hemagglutinating strains did not form a homogenous group inside the Prevotella genus.

Periodontal bone loss in mice induced by different periodontopathic organisms

Periodontal bone loss in mice orally inoculated with Peptostreptococcus anaerobius, Pept. magnus and Actinobacillus actinomycetemcomitans was compared to that in sham-inoculated mice. Six-to-8-week-old BALB/c mice were inoculated with 1 x 10(5), 1 x 10(7) or 1 x 10(9) colony-forming units (c.f.u.) of bacteria in 50 microliters of medium. Ten mice received each concentration of bacteria and 10 sham-inoculated mice acted as controls. Five mice from each of the groups were killed 6 weeks after inoculation and the remaining five mice at 12 weeks. Right hemimandibles were defleshed, stained and bone loss was measured using an image analyser. All the organisms tested were associated with bone loss. Animals that had received Pept. anaerobius and Pept. magnus had up to 18% more bone loss than those sham inoculated. In contrast, mice inoculated with A. actinomycetemcomitans had up to 38% more bone loss than the sham-inoculated animals, this amount of loss occurring at the lowest inoculation of 1 x 10(5) c.f.u. These data demonstrate a differential ability of micro-organisms to cause periodontal bone loss in mice.

Infectious oral necrosis (cancrum oris) in Nigerian children: a review

The devastating orofacial gangrenous disease known as cancrum oris (noma) is still commonly seen in underprivileged Nigerian children. These children are usually victims of such stressors as chronic malnutrition, numerous endemic communicable diseases and severe adverse physical conditions which may lead to depletion of their adaptive resources or produce physiological maladaptation to additional stressors. Measles is the most common infection preceding the development of noma in Nigerian children. Acquired immunodeficiency as well as the impaired endocrine balance of the chronically malnourished permits, for example, widespread infection with the measles virus. Anergy resulting from the combination of malnutrition and measles virus infection promotes selective overgrowth and invasion by an infective consortium consisting of anaerobic organisms and other species capable of elaborating necessary growth factors for the former. Because of the pre-existing depletion of adaptive physiologic resources in the malnourished child, the infection is not readily contained locally as necrotizing ulcerative gingivitis but instead spreads rapidly to the next naturally occurring anatomical barriers. This is then followed by continuing necrosis and possible sequestration as exemplified by noma.

Significance of encapsulated Bacteroides melaninogenicus and Bacteroides fragilis groups in mixed infections

Organisms of the Bacteroides melaninogenicus and Bacteroides fragilis groups are often found mixed with facultatively anaerobic organisms in infections. The relative importance of these Bacteroides groups and facultative anaerobic pathogens in mixed infections was investigated in a subcutaneous abscess model in mice. This was determined by observing the effect of antimicrobial therapy directed against one or both organisms present in the abscess. Clindamycin or metronidazole was used for treatment of infections caused by Bacteroides species, and either gentamicin, penicillin, ampicillin, or oxacillin was used for treatment of infections caused by facultative flora. In almost all instances the aerobic counterparts in the infection were more important than the unencapsulated Bacteroides species. On the other hand, encapsulated B. melaninogenicus group organisms were found to be more important in abscess formation than were group A streptococci, Streptococcus pneumoniae, Klebsiella pneumoniae, Haemophilus influenzae, and Staphylococcus aureus. Encapsulated B. fragilis group organisms were found to be more important than or as important as Escherichia coli and group D streptococci and less important than S. aureus, group A streptococci, and K. pneumoniae in induction of subcutaneous abscesses. This study demonstrates that encapsulated Bacteroides species are a factor that should be considered in the treatment of mixed infections with antibiotics.

Effect of anaerobic bacteria on killing of Proteus mirabilis by human polymorphonuclear leukocytes

Killing of Proteus mirabilis by human polymorphonuclear leukocytes was tested in the presence of different Bacteroides species. In vitro experiments showed that anaerobic bacteria interfered with the killing of aerobic bacteria. However, this inhibitory effect was not a property of all Bacteroides species. Bacteroides gingivalis W83 showed the greatest inhibitory effect of the five Bacteroides strains tested. Killing of P. mirabilis was inhibited by the culture supernatant of B. gingivalis but not by washed cells. Two factors were found in the supernatant of B. gingivalis to account for the inhibitory effect. One was heat stable with a molecular weight of less than 3,500 and inhibited the killing activity of leukocytes, and the other was heat labile and partly inactivated the complement system. The killing experiments paralleled chemiluminescence measurements.

Bactericidal effect of pooled human serum on Bacteroides melaninogenicus, Bacteroides asaccharolyticus and Actinobacillus actinomycetemcomitans

Bacteria belonging to the species B. melaninogenicus ss. melaninogenicus (two strains), B. melaninogenicus ss. intermedius (five strains), B. asaccharolyticus (seven strains), and Actinobacillus actinomycetemcomitans (four strains) were tested under anaerobic conditions for their sensitivity to the bactericidal effect of pooled human serum. The A. actinomycetemcomitans strains were not killed to any extent by the serum. Both B. melaninogenicus ss. melaninogenicus strains were killed by serum. The sensitivity to serum among the strains of B. asaccharolyticus and B. melaninogenicus ss. intermedius was diverse. There was no correlation between the sensitivity to serum among the strains and the levels of specific antibodies in the serum. The bactericidal activity of serum was only effective if the complement system was present in serum. All strains initiated activation of complement and binding of a C3 component to the cell surface both in normal and MgEGTA chelated serum. The possible role of serum bactericidal activity in the pathogenesis of oral infections is unclear.

Penicillin-resistant bacteroides melaninogenicus infection of the mandible

Oral infections caused by gram-negative anaerobes are now recognized more frequently than in the past because of improved culturing techniques. A case of B melaninogenicus infection secondary to a fractured mandible, in which the organisms were both clinically resistant and insensitive on culture to penicillin, is presented. The organism was also shown to produce beta-lactamase. Clindamycin is appropriate dosage resulted in diarrhea, which precluded its continuation. Erythromycin therapy was curative in this case. In all cases in which the clinical course does not reflect the expected reasonable response to the appropriate antibiotic therapy, bacterial resistance to a drug should be considered, and laboratory testing for resistance and sensitivities should be performed.

Characterization of Bacteroides asaccharolyticus and B. melaninogenicus oral isolates

Experiments were designed to characterize a number of oral "pigmented" Bacteroides isolates with regard to their pathogenicity in an experimental model system and a number of other properties. T these include fatty acid determination, hemagglutination studies, collagenase and protease activities, and vitamin K dependency. Oral B, asaccharolyticus and B, melaninogenicus isolates differed from one another in phenylacetic acid production, hemagglutination, collagenase activity, and pathogenicity. All B. asaccharolyticus were found to be pathogenic in the vivo mixed infection model and this property could be correlated with biochemical enzymatic activities.

In vitro inhibition of Neisseria gonorrhoeae growth by strict anaerobes

Thirty two anaerobic bacterial strains were screened for their in vitro inhibitory activity toward 21 Neisseria gonorrhoeae strains, including two penicillin-resistant strains. From this screening, six anaerobic bacteria belonging to the genera Bacteroides, Peptostreptococcus, and Eubacterium were selected for their large antigonococcal spectrum of activity. The inhibitory activity of these six strains appears to be specific to the gonococcus as a variety of anaerobes and aerobes were not generally inhibited by these strains. The antigonococcal effect was not due to pH change or nutrient depletion of the media.

Neutrophil chemotaxis induced by anaerobic bacteria isolated from necrotic dental pulps

Anaerobic bacteria belonging to the species Bacteroides melaninogenicus, Bacteroides asaccharolyticus, Fusobacterium nucleatum, Peptostreptococcus anaerobius and Eubacterium alactolyticum, isolated from necrotic dental pulps, were tested for their capacity to induce neutrophil leukocyte chemotaxis. Generation of chemotactic factors in serum by whole bacterial cells and chemotaxis induced by bacterial extracts were studied in vitro by the Boyden technique. Subcutaneously implanted wound chambers in guinea pigs were used for testing leukocyte migration in vivo. All bacterial strains had a similar high capacity to induce neutrophil chemotaxis. The heavy accumulation of polymorhponuclear neutrophil leukocytes associated with clinical and experimental infections by B. melaninogenicus or B. asaccharolyticus cannot be ascribed to any extreme ability of these organisms to generate chemotactic factors.

Attachment of Bacteroides melaninogenicus subsp. asaccharolyticus to oral surfaces and its possible role in colonization of the mouth and of periodontal pockets

This investigation examined the ability of cells of Bacteroides melaninogenicus subsp. asaccharolyticus 381 to adhere to surfaces that might be important for its initial colonization of the mouth and its subsequent colonization in periodontal pockets. Of 48 asaccharolytic strains of B. melaninogenicus, 47 agglutinated human erythrocytes, whereas none of 20 fermentative strains, which included reference cultures of the subspecies intermedius and melaninogenicus, were active. Electron microscopy indicated that both asaccharolytic and fermentative strains possessed pili; hence, the presence of pili did not correlate with the hemagglutinating activities of B. melaninogenicus strains. Both asaccharolytic and fermentative B. melaninogenicus strains suspended in phosphate-buffered saline adhered in high numbers to buccal epithelial cells and to the surfaces of several gram-positive bacteria tested, including Actinomyces viscosus, A. naeslundii, A. israelii, Streptococcus sanguis, and S. mitis. B. melaninogenicus subsp. asaccharolyticus 381 also attached, but in comparatively low numbers, to untreated and to saliva-treated hydroxyapatite. Addition of clarified whole saliva to suspensions of strain 381 almost completely eliminated adherence to buccal epithelial cells and to hydroxyapatite surfaces, but saliva had no detectable effect on attachment to gram-positive plaque bacteria. Both fermentative and nonfermentative strains of B. melaninogenicus also attached in high numbers to crevicular epithelial cells derived from human periodontal pockets, but normal human serum strongly inhibited attachment. Serum also inhibited attachment of strain 381 to saliva- and serum-treated hydroxyapatite, but it had little effect upon attachment to gram-positive bacteria. These observations suggested that salivary and serum components would strongly inhibit the attachment of B. melaninogenicus cells to several oral surfaces, but not to the surfaces of certain gram-positive bacteria commonly present in human dental plaque. This was confirmed by an in vivo experiment in which streptomycin-labeled cells of B. melaninogenicus 381-R were introduced into the mouths of two volunteers. After 10 min, several hundred-fold higher numbers of the organism were recovered from preformed bacterial plaque present on teeth than from clean tooth surfaces or from the buccal mucosa and tongue dorsum. High numbers of B. melaninogenicus cells were also recovered from preformed plaque after 150 min, but virtually no cells of the organism were recovered from the other surfaces studied. These data suggest that the presence of dental plaque containing Actinomyces and other gram-positive bacteria may be essential for the attachment and colonization of B. melaninogenicus cells after their initial introduction into the mouth. Similarly, the presence of subgingival plaque containing gram-positive bacteria may be necessary for its secondary colonization in periodontal pockets.

Clotting and fibrinolytic activities of Bacteroides melaninogenicus

106 strains of Bacteroides melaninogenicus ss. asaccharolyticus, intermedius and melaninogenicus were tested for production of extracellular blood clotting and fibrinolytic factors. 78.3% of tested strains caused clotting of rabbit plasma and 79.2% activated human plasminogen. Strains producing the clotting or fibrinolytic factor only were isolated. Both factors were quite active, as positive results for most strains were detected within one hour of incubation in controlled test system.

Bacterial interference by oropharynegeal and clinical isolates of anaerobic bacteria

Anaerobic isolates were tested for bacterial inhibitory activity. Of 144 isolates, 102 were from oropharynegeal washings, and 42 were from clinical specimens. Thirteen facultative bacterial species (seven members of the Enterobacteriaceae and six species of gram-positive cocci) were used as indicators of inhibition. Eleven anaerobic species were isolated from oral secretions. All isolates of Bacteroides melaninogenicus, the most commonly recovered species, consistently inhibited several species of indicator bacteria. Bacteroides fragilis, Bacteroides oralis, and Peptostreptococcus anaerobius had unprecictable inhibitory activity, whereas most of the other oral anaerobes were noninhibitory. The 42 clinical species were generally noninhibitory.