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Biomedical subjects

L P Samaranayake

Publications and source records attributed to L P Samaranayake.

At least 127 records · Page 7Linked to original sources
PubMed1997

A 4-year longitudinal study of the oral prevalence of enteric gram-negative rods and yeasts in Chinese children.

A 4-year longitudinal study of the oral prevalence of enteric gram-negative rods and yeasts in 116 Chinese primary school children in Hong Kong was conducted. The oral prevalence of enteric gram-negative rods for each consecutive year was 25.3%, 37.0%, 24.0% and 25.8% respectively, with a weighted mean of 27.9%. Enterobacteriaceae, which comprised 57% of all enteric gram-negative rods, were more common in children with no caries experience. The oral prevalence of yeasts for each consecutive year was 7.7%, 12.0%, 14.4% and 15.5% respectively, with a weighted mean of 12.5%. Candida albicans comprised 84% of all yeasts isolated. Oral yeast carriage was significantly associated with caries prevalence. While the oral prevalence of enteric gram-negative rods in primary school children in Hong Kong may be higher than in other parts of the world, repeated isolation of either enteric gram-negative rods or Candida spp. from individual children over the 4-year study period was rare, suggesting that carriage of these organisms is transient.

Candida↗
PubMed1997

Association between carriage of oral yeasts, malnutrition and HIV-1 infection among Tanzanian children aged 18 months to 5 years.

The objective was to determine whether there is an association between carriage of oral yeasts, malnutrition and HIV-1 infection among Tanzanian children. A case-control study design within a cross-sectional study was used, and the outcome was carriage of oral yeasts. The exposure variables were malnutrition and HIV-1 antibody, and confounders to be adjusted for were age, sex, and breastfeeding. The study was carried out in Dar-es-Salaam, Tanzania, in two maternal and child health (MCH) clinics that offer routine medical checkups to all expectant mothers and children aged between 0 and 5 years in the catchment area. A total of 882 children aged between 18 months and 5 years participated. Smears from the tongue and buccal mucosa were examined for oral yeasts. Malnutrition was categorized according to standards on the MCH chart and World Health Organization/Centers for Disease Control (WHO/CDC) standards as weight-for-height (wasted), weight-for-age (underweight), and height-for-age (stunted). HIV-1 infection was determined by an enzyme-linked immunosorbent assay. Reactive sera were confirmed by Western Blot. About 27% of the children were slightly or severely malnourished according to standards on the MCH chart. According to WHO/CDC standards, 2.6% were wasted, 16.3% were underweight, and 29.6% were stunted. Fourteen (1.6%) were seropositive for HIV-1 antibody. Hyphal forms and blastospores were much more frequent among children infected with HIV-1 with odds ratios ranging from 3.8 (95% CI: 1.3;11.2) to 6.2 (95% CI: 2.1;18.4) depending on categorization of malnutrition. Malnutrition was a risk factor, too, albeit to a much lesser and insignificant degree. The study supports our previous findings that malnutrition may predispose to carriage of oral yeasts and subsequent infection. However, in this study population HIV infection was clearly the predominant risk factor.

AIDS-Related Opportunistic Infections↗
PubMed1997

Candida krusei infections and fluconazole therapy.

Candida species are by far the most common agents of mucosal fungal infection in man. While Candida albicans is the most notorious pathogen in this group, non-albicans species such as Candida krusei are gradually emerging as pathogens of concern, especially in compromised hosts. It is thought that the wide use of the newer triazole drug, fluconazole, in HIV-infected individuals is contributing to this phenomenon. Studies in both humans and animals have now demonstrated prophylactic and therapeutic failure of fluconazole against C. krusei due to increasing resistance of the organism to this azole. Thus, the indiscriminate use of fluconazole, a drug with relatively minimal toxicity and excellent pharmacokinetics, may lead to the development of widespread resistance to this azole among Candida species.

Journal Article↗
PubMed1997

The antifungal effect of lactoferrin and lysozyme on Candida krusei and Candida albicans.

Lactoferrin and lysozyme (muramidase) are non-immune defence factors present in various exocrine secretions, including saliva. Previous studies have shown that both proteins, either singly or in combination, are bactericidal in nature and their combined activity is synergistic. As little is known of their interactions with Candida species, 20 oral isolates of C. krusei and 5 isolates of C. albicans were studied for their susceptibility to human apo-lactoferrin and lysozyme, either singly or in combination, using an in vitro assay system. The two species exhibited significant interspecies differences in susceptibility to lactoferrin (p < 0.05), but not for lysozyme; C. krusei being more sensitive to lactoferrin (c 1.4 times) than C. albicans. Both species revealed significant intraspecies differences in their susceptibility to lysozyme (p < 0.05), but not for lactoferrin. No synergistic antifungal activity of the two proteins on either Candida species was noted. The results imply that the variable expression of the fungicidal activity of lactoferrin and lysozyme on Candida species may modulate the oral carriage of yeasts in a complex manner.

Antifungal Agents↗
PubMed1997

Nutritional status of under fives attending maternal and child health clinics in Dar es Salaam, Tanzania.

We designed a study to assess the nutritional status of children under five years of age attending MCH clinics in Dar es Salaam. This was a cross-sectional anthropometric study involving children 6-24 months who from July to August 1993 were attending Magomeni MCH clinic and those aged 18 months to five years who were attending Lugalo and Mwananyamala MCH clinics for routine growth monitoring and for vaccination between May to August 1994. The data collected included age, birthweight, sex, weight, height, breastfeeding status and HIV-1 serostatus. Of the 1854 children enrolled (961 boys and 893 girls) 31.6% were stunted, 14.6% were underweight and 2.9% were wasted. The highest percentage of stunting and wasting was observed between 11 and 25 months and 36 to 40 months. Of the 849 children tested for HIV-1, 14 (1.7%) were seropositive and two out of 770 (0.3%) were born with low weight. HIV seropositivity and low birthweight were both associated with stunting and wasting. We conclude that malnutrition is still a sizeable problem among children attending urban MCH clinics in Dar es Salaam especially among those aged less than three years, to whom special malnutrition control strategies should be targeted. There is also a need to identify factors responsible for the observed decline in MCH attendance with age and correct the situation.

Age Distribution↗
PubMed1996

Ebola virus infection: an overview.

The current outbreak of the Ebola virus infection in Africa has yet again proven that highly dangerous diseases that are transmitted via the blood-borne route may be endemic in some parts of the world and may emerge as sporadic outbreaks causing worldwide concern. Health care professionals are at the forefront of combatting these diseases and treating infected individuals. Though dental professionals are unlikely to be directly involved in the management of such acute infections, with very high mortality rates, they may encounter patients seeking dental treatment who are either from, or who have recently toured the endemic disease areas. This overview, therefore, is a thumb nail sketch of the Ebola virus infection and its implications for dentistry.

Africa↗
PubMed1996

The oral prevalence of aerobic and facultatively anaerobic gram-negative rods and yeasts in semi-recluse human vegetarians.

Limited data exist on the oral ecology of vegetarians. Hence the dental and periodontal status, and the oral prevalence of aerobic and facultatively anaerobic Gram-negative rods (AGNR) and yeasts, were studied in 36 semi-recluse, vegetarian, Buddhist monks and nuns in Hong Kong. The oral prevalence of AGNR and yeasts was 61.1% and 33.3%. There was no correlation between the prevalence of AGNR and/or yeasts and the incidence of carious or filled teeth and the health status of the periodontium. Rather, the results of this study combined with those of previous studies suggest that increasing age and the consumption of food prepared in communal kitchens might be more important contributory factors in the oral prevalence of AGNR than the nature of the diet itself or the health of the dentition and periodontium.

Adult↗
PubMed1996

Predominant cultivable microflora of supragingival dental plaque in Chinese individuals.

The aim of this study was to determine the predominant supragingival cultivable bacterial flora in Chinese individuals, using the experimental gingivitis model. A total of 11 healthy dental students, mean age 22.5 years (range 20-25) were recruited. All were provided with once-a-week dental prophylaxis and oral hygiene reinforcement for 3 weeks to ensure gingival health. In the fourth week, after prophylaxis, the participants entered a 14-day period without any plaque control. A plaque sample was collected at days 1, 3, 7 and 14 from the buccal surface of the upper right canine, second premolar, first premolar and first molar, respectively. Each sample was then dispensed in tryptic soy-broth transport medium and grown anaerobically to obtain pure cultures, which were subsequently identified. Results showed that Gram-positive cocci and rods were the predominant cultivatable species (51-61%) in the samples throughout the 14-day period; with time there was a decreasing percentage of cocci and an increasing percentage of rods. Gram-negative cocci and rods increased in proportion with the plaque age (11-37%). Streptococcus spp. were the predominant Gram-positive cocci while Actinomyces were the predominant Gram-positive rods isolated. Fusobacterium and Capnocytophaga spp. were the two most frequent Gram-negative anaerobic rods cultured. The results compared with those from other analogous studies from the West suggest the possibility of interracial differences in supragingival plaque flora.

Adult↗
PubMed1996

In-vitro proteinase production by oral Candida albicans isolates from individuals with and without HIV infection and its attenuation by antimycotic agents.

In-vitro proteinase production by oral Candida albicans isolates from patients with and without HIV infection (18 isolates from each group) was assessed by image analysis of a plate assay, with bovine serum albumin (BSA) as a substrate. The effect of sub-minimal inhibitory concentrations (sub-MICs) of nystatin, amphotericin B, clotrimazole and miconazole on in-vitro proteinase production by these yeast isolates was also investigated. Proteinase production by C. albicans isolates from patients with HIV infection was significantly greater than production by those from individuals without infection. All 18 isolates from HIV-infected individuals produced proteinase, in comparison to 56% of isolates from uninfected individuals. Pre-exposure of C. albicans isolates (seven proteinase producers from each group) to 1/4 and 1/16 MICs of nystatin, amphotericin B, clotrimazole and miconazole resulted in decreased proteinase production in all isolates tested. However, after exposure to the four antimycotic agents, proteinase production was decreased to a significantly greater extent in isolates from uninfected individuals than in those with HIV disease. Furthermore, when the relative concentration effect of antimycotic agents on proteinase production was compared, C. albicans isolates from the HIV-free group demonstrated a salient dose-response relationship compared with the HIV-infected group. These results indicate that C. albicans from patients with HIV infection are significantly more proteolytic than those from individuals without the infection, and that polyenes and imidazoles curtail the proteolytic activity of all C. albicans isolates, albeit to a lesser extent in those from HIV-infected patients. It appears that HIV disease favours oral colonisation by more proteolytic C. albicans isolates, with resilient proteolytic activity.

AIDS-Related Opportunistic Infections↗
PubMed1996

The effect of oral commensal bacteria on candidal adhesion to human buccal epithelial cells in vitro.

The effect of Streptococcus sanguis, S. salivarius, Escherichia coli and Porphyromonas gingivalis on the adhesion of Candida albicans and C. krusei to human buccal epithelial cells (BEC) was investigated with a modified membrane filter system. The filters (12 microns diameter pores) acted as a support for the BEC which were pre-exposed to known concentrations of bacterial suspensions (for 45 min-1 h), and then re-incubated with standardised concentrations of yeast suspensions for various periods. The BEC with adherent yeasts were then transferred on to a glass slide, gram-stained and counted by light microscopy. Three of the four bacterial species significantly suppressed adhesion of C. albicans to BEC; S. sanguis had no effect. Both S. sanguis and S. salivarius suppressed adhesion of C. krusei to BEC pre-exposed to three different bacterial concentrations, although variable results were obtained with P. gingivalis and E. coli. Significant differences in the relative adhesion of C. albicans and C. krusei to BEC were also recorded. These results indicate that the adhesion of yeasts to BEC is modulated both by the composition and the quantity of the pre-existing bacterial flora on the BEC.

Adult↗
PubMed1996

Predominant cultivable supragingival plaque in Chinese "rapid" and "slow" plaque formers.

The aim of this study was to compare the predominant cultivable bacterial flora in supragingival plaque samples of Chinese "rapid" and "slow" plaque formers, using the experimental gingivitis model. 11 Chinese subjects (5 "rapid" and 6 "slow" plaque formers) were selected from 49 healthy young adults. The selection was based on the plaque index on the buccal surfaces of all the canines, premolars and 1st molars after 3-days without plaque control. The 11 subjects began a 14-day on oral hygiene period after prophylaxis. Plaque samples were collected on day 1, day 3, day 7 and day 14 from the buccal surface of upper right canine, 2nd premolar, 1st premolar and 1st molar, respectively. The samples were then dispensed into a tryptic soy broth, and cultured anaerobically to obtain pure isolates which were then identified by conventional means. Results showed similar trends in plaque development in the two groups; gram-positive bacteria were the predominant cultivable species ("rapid": 71-37%; "slow": 53-63%) and gram-negative species increased in proportion to the plaque age ("rapid": 9-47%, "slow": 13-28%). "Rapid" plaque formers showed a statistically significant higher percentage of gram-negative rods (38%) than the "slow" group (17%) in the 14-day samples. The difference in the proportions of other groups of bacteria between the "rapid" and "slow" plaque formers were also found to be statistically significant using the MANOVA test (p = 0.0162). Most of the cultivable gram-negative rods belonged to Fusobacterium and Capnocytophaga species. Besides the quantitative difference observed clinically, there seems to be a qualitative difference in the cultivable flora between subjects with different rates of plaque formation.

Adult↗
PubMed1996

Bacterial morphotypes of 3-day old plaque in Chinese. A pilot study.

The aim of the this study was to estimate the % distribution of bacterial morphotypes of supragingival plaque in Chinese subjects after 3 days of no oral hygiene. 36 dental students, hygienists or dental surgery assistants (mean age: 24.3 years) were recruited. Prophylaxis and oral hygiene reinforcement were given 1 x a week for 3 weeks to obtain gingival health and a 3-day period without any plaque control started afterwards. At the end of the 3-day period, the plaque along the gingival margin of the upper right central incisor was removed and direct Gram stained smears were prepared for light microscopy. Bacteria were classified as gram-positive or gram-negative cocci, rods, filaments, fusiform organisms, spirilla or spirochetes. A differential count of 200 organisms from 3-6 microscopic fields was performed and the results expressed as a % of the organisms counted. Results from the 36 direct smears showed approximately 83% (range: 52%-96%) of the organisms to be gram-negative while gram-positive bacteria comprised only a minority of about 12% (range: 0.7%-43%). This result is remarkably different from previous reports from the West where gram-positive bacteria were the predominant bacterial types noted in early supragingival plaque. Further longitudinal studies involving both microscopy and bacteriological culture will be necessary to confirm this finding.

Adult↗
PubMed1996

The effect of oral commensal bacteria on candidal adhesion to denture acrylic surfaces. An in vitro study.

The effect of four different species of oral bacteria (Streptococci (X 2); Escherichia; Porphyromonas) on the adhesion of Candida albicans and Candida krusei to denture acrylic surfaces was studied using a previously described in vitro adhesion assay. Clear acrylic strips immersed in known concentrations of bacterial suspensions and incubated for 45 min to 1 h, at 37 degrees C, were transferred to yeast suspensions of known concentrations and incubated for a similar period, and the adherent yeasts were quantified using an image analysis system. Pre-exposure to different bacterial concentrations resulted in suppression of candidal adhesion to varying degrees. Of three selected concentrations, exposure to the highest bacterial concentration (10(6) organisms/ml) resulted in a consistent reduction in candidal adhesion, except for E. coli-C. albicans and S. salivarius-C. albicans combinations. Candidal adhesion was significantly reduced on pre-exposure to S. sanguis and P. gingivalis, but not E. coli. There were also significant differences in relative adhesion between C. albicans and C. krusei. Taken together, these results indicate that the adhesion of yeasts to acrylic strips is modulated both by the quantity and the quality of pre-existing bacterial flora on acrylic surfaces.

Acrylic Resins↗
PubMed1996

The adherence of oral isolates of Enterobacteriaceae to HeLa cells. An in vitro method using image analysis.

An in vitro model and an image analysis were designed to improve on existing quantification methods in the assessment of the adherence of Enterobacteriaceae to human epithelial cell monolayers. Adherence to HeLa cell monolayers of three oral isolates and one type strain from each of four species of Enterobacteriaceae over two incubation time periods was examined. Correction for actual cell area and a cube root transformation of the data to stabilize variance were applied. While behaviour varied between strains within species, E. cloacae was the most, and K. pneumoniae the least, adherent species irrespective of the incubation period. Increasing the incubation period from 30 min to 60 min resulted in greater adherence for E. cloacae, E. coli, and C. freundii, but not K. pneumoniae strains. The method permits the reliable measurement and valid analysis of the adherence of Enterobacteriaceae to cultured epithelial cell monolayers.

Cell Adhesion↗
PubMed1996

Prevalence of oral lesions in a selected Vietnamese population.

Clinical examination of the oral and peri-oral regions of a cohort of 550 Vietnamese living in a refugee camp in Hong Kong was conducted. They comprised 216 (39 per cent) males and 334 (61 per cent) females and their age ranged from 2 to 60 years. A positive clinical finding was observed in 14 per cent, 35 males and 43 females. The most common condition observed was periapical infection (36 per cent), either with an abscess or a sinus. Other lesions noted include mucocele (10 per cent), traumatic ulcers (9 per cent), tori, either palatal (6 per cent) or mandibular (3 per cent), lymph node enlargement (7 per cent), pulp polyp (6 per cent), angular cheilitis (4 per cent), papillomas (3 per cent), cellulitis (3 per cent) and herpes lesions (2 per cent), 7 out of 9 (78 per cent) mucoceles were found in females. No malignant lesions were noted.

Adolescent↗
PubMed1996

Detection of anti-HIV-1 IgG antibodies in whole saliva by GACELISA and Western blot assays.

The present study, based on 158 HIV seropositives and 167 HIV seronegatives, demonstrates that saliva collected with the Omni-SAL device and tested with GACELISA (an IgG antibody capture ELISA) is an effective non-invasive alternative to serum for anti-HIV IgG antibody screening. The study also shows that a conventional serum Western blot kit can be used, with slight modifications, for confirmatory testing of saliva specimens. Collecting saliva with the Omni-SAL device had a very good acceptance rate among Tanzanian subjects, and although this diagnostic method is not yet known by the general public, 65% of the study participants preferred to give saliva instead of blood for HIV testing.

Adult↗
PubMed1996

Biotypes of oral Candida albicans isolates in a Tanzanian child population.

Although biotypes of Candida albicans from adult populations, especially in the West, have been described, there are no data either from a child population, or from the African continent. Hence a total of 200 oral C. albicans isolates from Tanzanian children aged 6-24 months were biotyped using two commercially available API micromethod kit systems and a boric acid resistance test. The predominant biotypes, which comprised two thirds of the organisms isolated, were J1S (19.5%), A1S (16.0%), J1R (14.5%), A1R (9.5%) and P1R (7.5%). In total, 16 new biotypes comprising 44 (22%) isolates which have not hitherto been described were found in this Tanzanian population and, of these, the P1R biotype predominated with 15 (7.5%) isolates. There was no significant association between predominant biotypes (with clusters > or = 15 isolates) and age, gender, breast feeding and malnutrition. These data indicate that the biotype profile of C. albicans isolates may differ in paediatric and adult populations, and/or global distribution of various subtypes of this common opportunistic pathogen.

Candida albicans↗