Identification of Candida dubliniensis in a HIV-positive South African population

Candida dubliniensis was identified as a distinctly separate species of the genus Candida in 1995. Since then the yeast has attracted considerable interest due to its prevalence in HIV/AIDS patients and its ability to develop fluconazole resistance in HIV-seropositive individuals. Although C. dubliniensis has been identified in many centres around the world it has not yet been isolated in Africa. The purpose of this study was to identify C. dubliniensis in an HIV-positive population in the Western Cape, South Africa. A cohort of 50 tuberculosis patients co-infected with HIV was selected on admission to the Brooklyn Chest Hospital, Western Cape. The inclusion criteria for patients accepted for the study were: confirmed HIV seroconversion with a diagnosis of tuberculosis obtained from chest X-rays and sputum microscopy. C. dubliniensis was identified in 6 of the 50 patients accepted onto the study. The prevalence of C. dubliniensis in our study population was lower than that reported in similar North American and European studies. These results confirm the presence of C. dubliniensis in the South African HIV/AIDS population and indicate the urgent need for further investigations into the prevalence and pathogenesis of this clinically important species in both adult and paediatric HIV-positive patients.

Effectiveness of three root canal medicaments to eliminate Actinomyces israelii from infected dentinal tubules in vitro

The persistence of anaerobic bacteria in the root canal system often leads to treatment failure. One possible reason for this may be the retention of micro-organisms in the dentinal tubules of root canal walls. This study was performed to compare the effectiveness of two root canal medicaments and a chlorhexidine solution in disinfecting Actinomyces israelii-infected root canal walls and dentinal tubules in vitro. Dentinal tubules of root canal walls of human teeth were experimentally infected with A. israelii. The root canals were exposed to either iodine potassium iodide, calcium hydroxide or 2% chlorhexidine for periods of 3, 7 and 60 days. At the end of the medication periods samples were removed at different depths and tested for A. israelii viability. Chlorhexidine was the only disinfectant that was able to eliminate A. israelii from all the samples after 3, 7 as well as 60 days while 25% of the specimens treated with iodine potassium iodide and 50% of the specimens treated with calcium hydroxide still had viable A. israelii after treatment. It is clear from this study that 2% chlorhexidine is superior to iodine potassium iodide and calcium hydroxide in its ability to remove A. israelii from infected dentinal tubules. However, in vivo trials need to be undertaken before its clinical use can be recommended.

Competition for glucose between Candida albicans and oral bacteria grown in mixed culture in a chemostat

The competition for glucose as a growth-limiting substrate between Candida albicans and a mixed community of oral bacteria was investigated. A chemostat was operated under glucose-limiting and glucose excess conditions at a dilution rate of 0.05/h. A mixed population of oral bacteria was established and after a steady state had been reached the chemostat was inoculated with C. albicans. Seven bacterial species Streptococcus sanguis, S. sobrinus, S. mitis, Lactobacillus casei, Veillonella dispar, Eubacterium saburreum and Fusobacterium nucleatum - were able to establish stable populations under glucose-limiting conditions. The yeast was unable to grow with the bacteria under glucose limitation. Only three bacterial species, S. sobrinus, L. casei and E. saburreum, became established under glucose-excess conditions. C. albicans was also able to become established in the glucose-excess chemostat and could grow and maintain a steady state in a mixed culture with these organisms. L. casei, S. mitis and S. sobrinus had faster glucose consumption rates than C. albicans. All the bacteria, except for E nucleatum, had maximum specific growth rates higher than C. albicans. The results suggest that glucose may act as a growth-limiting substrate for C. albicans in the establishment and growth of the yeast in a mixed community of oral bacteria.

External bacterial contamination of local anaesthetic cartridges

In this study external bacterial contamination of local anaesthetic cartridges from newly opened and open containers was examined. Colonies of mainly Gram-positive cocci and Gram-positive rods were grown from cartridges from both the freshly opened and open containers. However, the total number of colonies grown from open containers was significantly higher than that from freshly opened ones. It was concluded that where local anaesthetic cartridges are bulk-packed in containers, strict infection control measures are to be instituted in clinical practice. We suggest that these include keeping containers tightly capped, removing cartridges only when needed, using forceps to handle cartridges and swabbing cartridges with alcohol prior to loading into syringes.

The effect of areca nut on salivary and selected oral microorganisms

The aim of this study was to investigate the effect on the growth of salivary and selected oral microorganisms of areca nut, aqueous extracts of the nut, its major alkaloid arecoline and the components tannic acid and catechin of its tannin fraction. The antibacterial properties of the above were tested on Streptococcus mutans, Streptococcus salivarius, Candida albicans and Fusobacterium nucleatum and, as a control, Staphylococcus aureus. This was followed by investigating its effect on salivary organisms cultured from the saliva after chewing boiled areca nut. Extracts inhibited the growth of the selected organisms in a concentration dependent manner, baked and boiled nuts being significantly more potent than raw nut. Growth of C. albicans was the least affected by the nut extracts. Tannic acid was strongly antibacterial but not catechin or arecoline. No antibacterial effect could be demonstrated on salivary organisms after chewing the nut for 5 minutes but exposure of saliva to the cud for 1 hour caused a significant depression of bacterial growth. It is concluded that the hydrolysable tannins in the tannin fraction, which include tannic acid, are responsible for the antibacterial properties of the nut and that prolonged intraoral exposure to the nut can suppress bacteria in the mouth.

Induced candidosis in mice with artificially established oral flora

The aim of this study was to gauge the effect of an artificially established flora, unnatural for mice, on the induction of oral candidosis in mice. Four groups of BALB/c mice were compared; conventional Candida albicans-free mice, "germ-free" mice which had been inoculated with Candida-free human saliva, germ-free mice which had been exposed to a cocktail of Streptococcus mitis, S. sobrinus and S. sanguis, and uncontaminated germ-free mice. After exposure to C. albicans via drinking water, the four groups of mice were killed and their oral cavities examined for candidal growth and oral lesions. Conventional mice yielded significantly less candidal growth and exhibited significantly fewer oral lesions than the other three groups. Candidal lesions in the two groups of contaminated germ-free mice were significantly fewer than in the uncontaminated germ-free mice. The latter exhibited extensive candidal lesions with little inflammatory infiltrate. It is concluded that mice with human oral micro-organisms have some resistance against candidal infection albeit at a reduced level, that mice with natural oral flora are highly resistant, and that germ-free mice are extremely susceptible to C. albicans infection.

The establishment of a community of oral bacteria that controls the growth of Candida albicans in a chemostat

The purpose of this study was to establish and identify a community of oral bacteria that controls the growth of Candida albicans in the chemostat. The chemostat was operated under glucose-limiting conditions at a dilution rate of 0.05 h-1 and inoculated with a yeast-free suspension of a tongue scraping. After a steady state had been reached, it was inoculated with C. albicans to establish the yeast and determine whether its growth could be contained. The steady-state community comprised the species Streptococcus sanguis, Streptococcus sobrinus, Streptococcus mitis, Lactobacillus casei, Eubacterium saburreum, Veillonella dispar and Fusobacterium nucleatum. Bacteroides gracilus and Haemophilus segnis were also detected but infrequently. Yeast growth was suppressed and yeast cells were lost at the same rate as the theoretical washout rate. It is concluded that this mixed community of oral bacteria can be used to identify the parameters that maintain the equilibrium between oral bacteria and C. albicans in the oral cavity.

Shear bond strength, microleakage and antimicrobial properties of AElitebond

PURPOSE

To evaluate the shear bond strength (SBS) and microleakage (ML) to dentin as well as the antimicrobial action against five strains of oral bacteria of AElitebond single primer restorative system.

MATERIALS AND METHODS

Fifteen molars were tested to failure for each of the four time periods: 15 minutes, 24 hours, 7 days and 30 days, after final cure. The test specimens were prepared on the dentin surfaces of the extracted molars ground on 600 grit SiC paper. The bonded cylinders were removed from the assembly apparatus after cure, stored in physiological saline at 37 degrees C for the four different time periods and subjected to a shear bond load at 0.5 mm/minute until fractured. For the microleakage determination, Class V cavity preparations were done on the facial surfaces of the roots of 15 canines below the cemento-enamel junction and the specimens thermocycled (500x) between 8 degrees C and 15 degrees C in 2% methylene blue. The teeth were cut into 6 mm thick sections and the sections which included the restorations were separately dissolved in acid. The color intensities of the dissolved sections were measured at a wavelength of 590 nm against a standard curve which was constructed from the dye. The modified model cavity method of Meryon & Johnson (1989) was used to assess the antimicrobial properties of the restorative system.

RESULTS

The mean SBS values (in MPa) were found to be 10.3, 9.8, 11.47 and 9.9 after 15 minutes, 24 hours, 7 days, and 30 days, respectively. There was no significant increase (P < 5%) in the SBS after 15 minutes. The ML of 0.76 micrograms dye/ restoration was relatively low in comparison to the SBS values. The restorative system significantly (P < 5%) inhibited the growth of Actinomyces naeslundii with 88%, Streptococcus mutans with 42%, Streptococcus sanguis with 39% and Streptococcus oralis with 9%. However, the growth of Veillonella parvula was stimulated with 49%.

Antibacterial action of honey on oral streptococci

The antibacterial properties of honey against medically important bacteria have been well documented but this information is not available for the oral bacteria and specifically for the oral streptococci. We determined the minimal inhibitory concentration (MIC) of honey for oral streptococci. Honey had a MIC of 25 per cent (vol/vol) for the bacteria tested with the exception of Streptococcus anginosus and Streptococcus oralis which were inhibited by 17 per cent (vol/vol) and 12 per cent (vol/vol) honey respectively. The hypertonic sugar control had a MIC of 25 per cent (vol/vol) for all the bacteria tested. Although the results of this study indicate that there could be other antibacterial agents present in the honey, it may be assumed that the hypertonic sugar concentration played an important role in this activity.

Some "sealants" seal--a scanning electron microscopy (SEM) investigation

White spot lesions of enamel around orthodontic brackets as a result of demineralization have been well documented in the orthodontic literature. Various methods of treatment have been attempted to reduce or eliminate this danger. The purpose of this study was to evaluate, by means of scanning electron microscopy, the polymerization of the sealant layer around orthodontic brackets with direct and indirect methods of bonding. Twenty-four sound human lateral maxillary incisor teeth were collected, cleaned, divided equally into four groups A through D, and stored in 70% ethyl alcohol. Their buccal surfaces were pumiced, etched with 37% phosphoric acid for 1 minute, and washed under running water for 30 seconds. Metal brackets were bonded with the chemically cured BIS-GMA resin, Ortho Concise, as follows: group A, indirectly bonded with coping; group B, indirectly bonded without coping; and group C, directly bonded; light activated Transbond was used in group D, directly bonded brackets. After washing in alcohol for 20 seconds, all teeth were dried, and sectioned longitudinally, through the middle of the bracket. All were subjected to 5% hydrochloric acid for 30 seconds and then washed under running water for 30 seconds. After drying and sputter coating, the teeth were viewed under scanning electron microscopy. Groups A and D showed a sealant layer surrounding the brackets and covering the buccal enamel. Groups B and C showed total absence of a cured sealant layer around the brackets or surrounding enamel.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of honey on human tooth enamel in vitro observed by electron microscopy and microhardness measurements

Various fruit juices with relatively low pH are known to have erosive effects on human tooth enamel in a reasonably short time. Honey, also with a relatively low pH, could do the same, but scanning electron microscopy showed no erosion of enamel by honey over a period of 30 min, neither did Knoop microhardness tests show any deterioration of enamel structure. The absence of any effect could be only partially attributed to the calcium, phosphorus and fluoride levels in honey.

Porphyromonas gingivalis as putative pathogen in ovine periodontitis

Ovine periodontitis has clinical features similar to early onset periodontitis in man. Porphyromonas gingivalis has been implicated as a putative pathogen in this disease and its role in periodontitis in 107 sheep was investigated. The organism was recovered from most diseased sites at a significant percentage level of the total bacterial count. Antibody assays of 107 animals using an ELISA did not distinguish between diseased (46) and control adult (33) sheep for either P. gingivalis or any of the other putative periodontopathogens tested, but did differentiate adult sheep from healthy lambs (28) for all bacteria except one. It is suggested that sheep rather than human bacterial strains should be used in antibody studies of ovine periodontitis.

Household products as sanitising agents in denture cleansing

Since a large percentage of denture wearers in South Africa make use of household products as denture cleansers, it was considered desirable to find a household product which can be used as a satisfactory sanitising agent in denture cleansing routines. Six subjects, each wearing an acrylic plate with removable plugs of a standard surface area, used a different solution in rotation as a disinfectant. The following solutions were tested: a 0.04 per cent hypochlorite + 0.66 per cent NaCl (4 per cent Milton), 0.012 per cent hypochlorite + 0.19 per cent NaCl (1.2 per cent Milton), 20 per cent NaCl, undiluted vinegar and 50 per cent diluted vinegar solutions. On completion of each experimental period the plugs were removed, visually inspected and viable bacterial counts were made. All solutions resulted in a significant (p < 0.01) reduction of viable bacteria compared to the tap water control. The sodium hypochlorite solutions were more effective sanitising solutions.

Orthodontic microabrasive reproximation

Reproximation (enamel stripping) is described in the literature as a clinical procedure for correction of tooth size deviations. The objective of this study was to qualitatively assess, by means of scanning electron microscopy, (1) the differences exhibited on enamel with mechanical and chemical methods of stripping, and (2) the effect of a synthetic calcifying solution on the etched enamel. Part 1. Sixty human anterior teeth (10 complete sets) that were previously stored in 70% ethanol were subdivided into groups I and II. The teeth in group I were divided into five sets of six teeth mounted in a plaster block in the anterior arch form. Each set was stripped with one of the following mechanical abrasive methods: garnet disks, tungsten carbide and fine diamonds burs, coarse and fine diamond burs, diamond wheel and 3M strips, diamond-coated metal and 3M strips. The teeth in group II were similarly treated, except each set was subjected to a further microabrasive chemical stripping with 37% phosphoric acid used in conjunction with 3M strips. The teeth were then prepared for scanning electron microscopy, viewed, and photographed under magnification. Part 2. Ten human central incisor teeth were etched and used to study the effect of remineralization solutions at various time intervals. The results showed that teeth stripped by routine mechanical abrasive methods exhibited deep furrows and roughness. The teeth that received mechanical and chemical abrasive treatments showed a flattened, etched surface free of furrows. These etched surfaces showed marked crystal growth at 5 and 10 hours after remineralization suggesting the possibility of repair of the chemically altered enamel surface.

Growth interaction between Candida albicans and Streptococcus salivarius: in vitro and in vivo studies

Suppression of Candida albicans in the mouth by oral flora has been proposed as one of the mechanisms preventing candidal overgrowth. According to Liljemark and Gibbons (1973), Streptococcus salivarius plays a significant role in this process. The aim of this investigation was to study the growth interaction between C. albicans and S. salivarius in vitro and in vivo. An aerobic continuous-flow system was used for the in vitro study. Pure and mixed cultures of C. albicans (NCPF 3118) and S. salivarius (NCTC 8618) were inoculated into a buffered medium containing either 0.1 per cent or 0.001 per cent glucose concentrations and incubated at 37 degrees C for 55 hours. Two in vivo investigations were undertaken using inbred germfree C3H mice. In the first, mice were exposed to a mixed suspension of S. salivarius and C. albicans for 48 hours. In the second the mice were exposed to S. salivarius for 48 hours. Fourteen days later they were contaminated with C. albicans. A comparison of growth curves showed no growth inhibition between the species. The in vivo studies showed that oral lesions from candidal infestation occurred in all mice. We were therefore unable to demonstrate in vitro or in vivo suppression of C. albicans in the presence of S. salivarius.

Evaluation of inbred germ-free Fischer 344 albino rats as an experimental model for oral candidiasis

Inbred germ-free Fischer 344 albino rats were evaluated as models for experimental candidiasis in order to investigate bacterial interaction with Candida albicans. Female rats were exposed to C. albicans in their drinking water and killed at intervals from 2 to 22 days after initial contact with the contaminant. C. albicans was cultured from their mouths from day 2 but from day 12 the number of colonies decreased. From day 2 to 9 all rats showed oral histological signs of candidal infestation, but after 9 days the number declined to 3 out of 9 at 22 days. The dorsal surface of the tongue was the best histological indicator of candidal infestation. All the rats had tongue lesions from day 4 to 9, and from day 6 there was also a concomitant localized loss of filiform papillae. The number of rats with all forms of tongue involvement also decreased after 9 days with only 3 out of 9 affected at 22 days. It is concluded that Fischer 344 inbred germ-free rats can be used on a limited scale as a model for candidiasis and bacterial interaction with C. albicans, the dorsal surface of the tongue would be the best site for studying candidal experimental lesions and it is probable that better results can be achieved with complete standardization of contamination and preparation procedures.

Hypohidrotic ectodermal dysplasia: a genealogic, stereomicroscope, and scanning electron microscope study

This is a report of three patients with hypohidrotic ectodermal dysplasia, or Christ-Siemens-Touraine syndrome, their genealogic backgrounds and the stereomicroscope and scanning electron microscopic appearances of the hair, the skin of their fingertips and palms as well as skin studies of members of their families. The skin morphology was recorded by means of silicone monomer rubber impressions and epoxy resin dyes. In two of the patients the disease was acquired by X-linked inheritance, while in the third, a boy, it appeared to follow an autosomal dominant pattern. Defects of the skin of the fingertips and palms of the propositi and members of the families included abnormalities of the morphology and pattern of the epidermal ridges, reduction of sweat pores varying from 13 to 87% of normal, and changed anatomy of the openings of the sweat glands. The openings were shallow and with less whorling compared to the normal, funnel-shaped sweat pores. Among the sweat pores, micropores, or openings with an average diameter of 5.3 micrometers, were observed. One of the propositi and the affected father of another had orifices on their fingertips resembling hair sheaths. Two propositi and the affected father of one exhibited grooving of the hair. The findings confirm the necessity for genealogic investigations in patients with or suspected of having the disease in order to advise parents or prospective parents. They also illustrate the usefulness of stereomicroscopy and scanning electron microscopy in observing skin and hair abnormalities.