Viral infections in the mouth

Oral hairy leukoplakia (OHL) and Kaposi's sarcoma (KS) are commonly encountered in the HIV-infected patient. A unique feature of OHL is non-cytolytic high level of replication of Epstein–Barr virus (EBV) in the glossal epithelium. The expression of viral-encoded anti-apoptotic proteins concomitant to replicative proteins probably underlies this phenomenon. The question of whether OHL arises from activation of EBV latent in the tongue, or from superinfection by endogenous EBV shed via non-glossal sites or by exogenous EBV remains unresolved. Human herpesvirus 8 (HHV8) is now seen as necessary but not sufficient cause of KS. Expression of HHV8-encoded oncogenic proteins in endothelial cells probably explains the aberrant proliferation of these cells in KS lesions. Studies into why KS is so commonly observed at the palate in HIV-infected patients may provide important clues to its pathogenesis.     

Glycosaminoglycan-depolymerizing enzymes produced by anaerobic bacteria isolated from the human mouth

A number of obligately anaerobic bacteria, some implicated in periodontal disease, were screened for their ability to produce enzymes capable of degrading hyaluronic acid and chondroitin-4-sulphate. Two screening methods were used following anaerobic incubation at 37 degrees C for 7 days. One involved incorporating the respective substrates and bovine-serum albumin into agar plates and, after incubation, flooding the plates with 2 M acetic acid. Clear zones were produced around colonies which produced enzymes capable of depolymerizing the substrates. The second was a sensitive spectrophotometric procedure based on the ability of certain bacteria to produce eliminase enzymes, which degrade the substrates to unsaturated products having a characteristic u.v. absorption at 232 nm. Strains of Bacteroides gingivalis and Bacteroides melaninogenicus degraded both substrates whereas Bacteroides asaccharolyticus degraded neither substrate by either method. Some bacteria gave negative results with the plate method whereas the more sensitive spectrophotometric assay proved positive. The number of anaerobic bacteria capable of degrading hyaluronic acid and chondroitin-4-sulphate in vitro may therefore have been underestimated in previous studies.     

Antigenic variation in populations of Streptococcus salivarius isolated from the human mouth.

Populations of Streptococcus salivarius CM6 exhibited antigenic variation while colonizing the mouth and intestinal canal of gnotobiotic rats. Variants which no longer produced detectable levels of one or more of 5 antigenic components discernible by immunoelectrophoresis were isolated in low proportions as early as 3 days after mono-infection of germ-free rats; almost all isolates obtained 2 weeks after infection were variants. Oral and faecal isolates attached less well than the parent strain to human or rat buccal epithelial cells. Variants altered with respect to 2 of the 5 components emerged first and such variants were the most common. These 2 components could not be detected in Strep. salivarius cells following treatment with trypsin. There were no variants of laboratory stock cultures of strain CM6 over a 3-yr period. The relative predictability of the emergence of variants in gnotobiotic rats suggests that a specific selection pressure was responsible, part of which was due to an immune response of the animals suggested by the emergence of variants more quickly in animals previously immunized with formalin-killed CM6 cells. Emergence of variants was less in animals pretreated with cyclophosphamide, an immunosuppressant, or fed diets supplemented with large numbers of killed Strep. salivarius. Populations of Strep. salivarius colonizing papillae on the tongue dorsum, and of Streptococcus mutans colonizing approximal molar tooth surfaces in man, were antigenically heterogenous; in some instances, the proportions of antigenic subtypes appeared to fluctuate with time.     

Characterization of haemolytic enterococci isolated from oral infections

Ninetytwo strains of haemolytic enterococci were isolated from patients with different oral infections — apical periodontitis and pulpitis — and identified by physiological, biochemical and serological tests. AH strains produced at least one haemolytic toxin which lysed rabbit erythrocytes. Most strains produced extracellular esterase, protease, and a bacteriolytic enzyme. No lecithinase, lipase, DNAse, amylase or staphylolytic enzyme were observed in the strains investigated.     

Antibiotic suseptibility of bacteria isolated from oral infections.

Exudates from bacterial infections of oral soft tissues were cultured and tested for antiobiotic susceptibility. Of 74 specimens tested, 68 were cultivable on blood agar; 56 of the cultivable exudates were pure cultures and 12 were mixed cultures. Strepococci and staphylococci accounted for 57% and 34%, respectively, of the pure cultures. Anaerobic bacteria were found in nearly 15% of the pure culture exudates. Gramnegative organisms accounted for about 4% of the pure cultures. Virtually all of the pure and mixed streptococcal cultures were sensitive or moderately susceptible to ampicillin, cephalothin, and penicillin; however, approximately 50% of the streptococal and staphylocococcal isolates were resistant to demeclocycline hydrochloride and erythromycin.     

The effect of a disinfectant/ coolant irrigant on microbes isolated from dental unit water lines

The purpose of this study was to assess water samples from a hospital dental clinic to determine whether a disinfectant/coolant irrigant containing chlorhexidine (Lines, ^tm Micrylium Laborator-ies) affects the presence of microbial organisms in dental unit waterlines. Water samples from three hospital dental operatories were collected at baseline and after overnight treatment with a disinfectant-containing irrigant followed by sterile water irrigation. Saliva of treated patients and sterile water rinse specimens were collected from the waterlines of these operatories for three consecutive days, then weekly for eight weeks after treatment. Specimens were cultured to identify total heterotrophic plate counts as well as presence of Pseudomonas aeruginosa and Candida species. Baseline organism counts varied from 10³ to 10⁵ colony-forming units per milliliter. After treatment, no organisms were detected in waterline discharge. Decontamination of dental unit waterlines is possible using a disinfectant/irrigant followed by sterile water irrigation. The potential for contamination of the lines from patients' saliva may have been reduced due to use of anti-retraction valves and the disinfectant/sterile water irrigation, as conducted in this study.     

Morphological changes in the bacterium Bacteroides melaninogenicus subspecies melaninogenicus isolated from the human mouth and grown in culture without added blood components

Striking polymorphism in the cellular morphology could be induced by removal of blood components from the liquid growth medium, but the cells of Bacteroides gingivalis and B. melaninogenicus subspecies intermedius did not exhibit polymorphism when grown under these conditions. The major changes observed with light microscopy were an increase in cell size and extreme polymorphism. Electron microscopy of the polymorphic forms of B. melaninogenicus subspecies melaninogenicus strains showed that such cells lacked both the outer cell membrane and peptidoglycan layer. Serum promoted the growth of these strains, suggesting that some blood component is either conducive to the synthesis of the cell wall or masks an unknown inhibitor for cell-wall synthesis contained in the medium.