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L P Samaranayake

Publications and source records attributed to L P Samaranayake.

At least 37 records · Page 2Linked to original sources
PubMed2004

Glass fibre-reinforced composite laced with chlorhexidine digluconate and yeast adhesion.

The aim of this study was to lace dental glass fibre reinforced composite (FRC) prepreg with chlorhexidine digluconate and to examine the adherence of common oral fungal pathogen Candida albicans to FRC made of the prepreg. Four different test and control material groups each comprising 16 test specimens ((5.0 x 5.0 x 0.8) mm3) each were used as substrates for C. albicans adherence. A porous polymer pre-impregnated woven glass fibre prepreg was laced with solution of chlorhexidine gluconate and it was used with autopolymerized denture base polymer to fabricate FRC test specimens. Control group (Group 1) consisted of FRC test specimens stored in water. In Group 2, the test specimens were stored in 10% chlorhexidine digluconate solution for 24 h. Group 3 consisted of specimens fabricated using such fibre reinforcements which were pre-soaked in 20% chlorhexidine digluconate and dried before preparation with denture base resin, and followed by storage of the specimens in water. Group 4 was similar to Group 3 but instead of water storage the specimens were immersed in 10% chlorhexidine digluconate for 24 h. For the candidal adhesion assay the test and control specimens were incubated in standardized suspensions of four different strains of C. albicans, rinsed and prepared for light-microscopy. The mean number of adherent cells in each group was counted microscopically and analysed statistically. There were significantly (P < 0.05) more adherent C. albicans cells found in Group 1 than in the other three groups which did not differ significantly from each other. The lowest numbers of adherent cells were found in Group 3. Pretreating the porous polymer pre-impregnated glass fibre reinforcement with chlorhexidine digluconate result in reduction in the number of adherent yeast cells on the surface FRC material.

Aerosols↗
PubMed2004

The effect of fixed orthodontic appliances on the oral carriage of Candida species and Enterobacteriaceae.

The aim of this investigation was to evaluate the prevalence of Candida and Enterobacteriaceae in a group of adolescents during fixed orthodontic appliance (FOA) therapy. The experimental group was recruited from a larger sample of orthodontic patients who were clinically examined once to obtain baseline data before active treatment. The group comprised 27 subjects; 13 males, 14 females (mean age 15.5 +/- 2.3 years). Thereafter, the experimental group was examined three times during a 3 month follow-up period after insertion of the FOA. The whole mouth plaque score was obtained, and the oral cavity was then sampled for Candida species and Enterobacteriaceae using three different microbiological culture techniques, namely the oral rinse, pooled plaque and the imprint culture.A significant increase in candidal numbers was observed after FOA insertion when the imprint technique was used (P < 0.001), although the overall candidal prevalence rates obtained using the oral rinse and pooled plaque techniques did not demonstrate such a change. The predominant Candida species isolated was C. albicans and the number of coliform carriers significantly increased after the insertion of a FOA, as detected by the oral rinse (P < 0.05) and the pooled plaque (P < 0.05) techniques. In total, eight coliform species were isolated following FOA therapy compared with the three species isolated before insertion of the appliance. The results also revealed a significant increase in plaque index due to the introduction of a FOA. Taken together, these data imply that insertion of a FOA is likely to promote oral carriage of Candida and coliform species. Furthermore, it appears that routine oral hygiene instruction and information on appliance hygiene given to these patients may not necessarily reduce plaque accumulation and possible attendant effects. Further work with a larger cohort is required to confirm these findings.

Adolescent↗
PubMed2004

Genotypic diversity of oral Actinomyces naeslundii genospecies 1 and 2 in caries-active preschool children.

A total of 991 isolates of Actinomyces naeslundii were obtained from sound approximal tooth sites in either caries-active (n = 35) or caries-free (n = 20) preschool children. From this group of isolates, 101 strains were chosen to study the genotypic diversity of A. naeslundii genospecies 1 (n = 30), catalase-positive (n = 30), and catalase-negative genospecies 2 (n = 41). Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), with a pair of primers targeting the 16S ribosome RNA gene (16S rDNA), and MnlI digestion together with randomly amplified polymorphic DNA (RAPD) with eight arbitrary, single 10-mer primers were performed to generate genetic profiles of selected Actinomyces isolates. The hierarchic relationships of genetic profiles were finally analyzed using computerized dendrograms. There was no significant difference in the prevalence rates and proportions of either genospecies 1 or 2 between the caries-free and caries-active groups, although a higher prevalence of genospecies 2 was noted in the total population. Dendrogram analyses of the 16S rDNA PCR-RFLP profiles revealed that all strains belonging to A. naeslundii genospecies 1 could be subgrouped into three genotypes (T7, T18, and T19), with a single predominant genotype, T18 (27/30). Catalase-positive strains for genospecies 2 fell into three subtypes (T4, T7, and T17), whereas the catalase-negative counterparts were distributed amongst 16 subtypes. No specific genotype was significantly associated with caries activity. We conclude that heterogeneous subgroups of A. naeslundii genospecies 1 and 2, particularly the latter, are the constituent flora of dental plaque in children and may contribute to the pathogenesis of childhood caries.

Actinomyces↗
PubMed2004

Oral candidosis and associated Candida species in HIV-infected Cambodians exposed to antimycotics.

Although human immundeficiency virus (HIV) infection is endemic in Southeast Asia, data on oral mycotic flora in this disease in Asians are sparse. The aim of this study was to determine the prevalence of Candida species in HIV-infected Cambodians with oral candidosis, unexposed (group 1) and exposed to antimycotics (group 2) and a healthy population (group 3). In 161 HIV patients with oral candidosis (group 1: 121 pts; group 2: 40 pts) and in 81 controls (group 3) swab samples of tongue and palate were obtained. Oral candidosis was detected in 100 and 70% of groups 1 and 2 respectively. Candida spp. were isolated from 91 and 100% of groups 1 and 2, respectively, and from 79% of controls. Candida albicans was the most common, with non-albicans species such as C. tropicalis and C. krusei being notable. Our data indicate that variants of oral candidal infections in HIV disease are similar to those seen in the pre-HAART era. The particularly high rate of C. krusei isolation in all groups is noteworthy.

AIDS-Related Opportunistic Infections↗
PubMed2004

Fungicidal effect of three new synthetic cationic peptides against Candida albicans.

OBJECTIVE: Peptide antibiotics are considered a new class of antifungal agents. Of these, an alpha-helical, cationic peptide termed Dhvar 4, a relative of salivary histatin has been shown to be an antifungal of relatively high potency. Similarly, lactoferricin B (LFB) and a derivative thereof, LFB(17-30), disrupts the fungal cell membrane and acts against Candida albicans. As Dhvar 4 and LFB(17-30), exhibit almost identical amino acid sequences at their C-terminal, we hypothesized that laboratory synthesis of peptides with an alpha-helical structure and having similar amphipathic properties could lead to products with candidacidal activity. Hence, three such peptides - JH8194, JH8195 and JH 8944, were synthesized and their antifungal properties compared with recognized antifungals LFB, LFB(17-30), human lactoferricin (LFH), Histatin-5 and Dhvar 4, against two isolates of C. albicans. MATERIALS AND METHODS: The antifungal agents were synthesized and their secondary structures evaluated according to a previously described protocol of Situ and Bobek (2000)Antimicrob Agents Chemother44: 1485-1493. The C. albicans strains were oral isolates from a human immunodeficiency virus-infected (isolate A2) and a healthy (A6) individual. A standard concentration of yeasts was exposed to a range of dilutions of the agents for a specific duration and the cell death (viability) in terms of the resultant colony forming units ml(-1) was quantified. RESULTS: Dhvar 4, showed the most alpha-helical propensity, and was the least fungicidal while LFB and LFB(17-30) showed the highest antifungal potential, and demonstrated total kill of A6, and A2 at 5 and 10 microM concentrations, respectively whilst LFH killed both isolates at a l0 microM concentration. Of the three new synthetic peptides, JH 8194 was the most potent (total kill of A6/A2 strains at 1.25/2.5 microM), followed by JH 8195 (total kill of A6/A2 strains at 5/10 microM while JH 8944 was the least potent as a 25 microM concentration was required to kill either strain of Candida. On further analyses of the relationship between pI value of the peptides and their anticandicidal activity, a significant positive correlation was noted. In order to rule out a cytotoxic effect of the new synthetic peptides we compared the fungicidal and hemolytic activities under similar incubation conditions using freshly isolated erythrocytes and all three peptides exhibited no detectable hemolysis upto an concentration of 100 microM in contrast to the polyene antifungal amphotericin B that elicited significant initiation of hemolysis at a concentration of 5.0 microM. CONCLUSION: Our data suggest that laboratory synthesis of agents with an alpha-helical structure and having amphipathic properties similar to known, natural antifungal agents may be a promising avenue to generate products with improved antifungal activity.

Amino Acid Sequence↗
PubMed2004

Molecular evaluation of residual endodontic microorganisms after instrumentation, irrigation and medication with either calcium hydroxide or Septomixine.

BACKGROUND AND OBJECTIVE: The correct choice of antimicrobial agents as inter-appointment medicaments is as important as the instrumentation and irrigation to remove pathogens from infected root canals. Calcium hydroxide [Ca(OH)2] and framycetin sulfate (Septomixine) are common endodontic medicaments. Therefore, we evaluated the efficacy of either calcium hydroxide or Septomixine in eliminating residual intra-canal bacteria, particularly Actinomyces spp., during inter-appointment interval in endodontic therapy using molecular methods. METHODS: A total of 31 single-rooted teeth with primary root canal infections were studied immediately after opening the canals and subsequently after instrumentation, irrigation with sterile saline and 1-week medication with either Ca(OH)2 (n = 25) or Septomixine (n = 6). Whole bacterial genomic DNA was isolated directly from samples and PCR with universal primers performed to detect total intra-canal bacteria. The variable regions of 16S rDNA of bacteria were amplified and labeled with digoxigenin for further hybridization to detect Actinomyces spp. A total of seven oligonucleotide probes specific for A. bovis, A. gerencseriae, A. israelii, A. meyeri, catalase-negative A. naeslundii (genospecies 1 and 2), catalase-positive A. naeslundii genospecies 2 and A. odontolyticus were used to detect Actinomyces spp. in 22 of 31 medicated root canals [Ca(OH)2: n = 17; Septomixine: n = 5]. RESULTS: The PCR results showed that 25 of 31 examined canals were positively detected with residual microorganisms after instrumentation, irrigation with sterile saline and 1-week medication with either Ca(OH)2 (n = 20) or Septomixine (n = 5). Thus, only six canals [Ca(OH)2: n = 5, Septomixine: n = 1] were aseptic after treatment. Hybridization results showed higher detection frequency of both A. odontolyticus and A. gerencseriae after treatment. Significant correlation was found between exposed pulp before treatment and positive detection of Actinomyces spp., particularly A. odontolyticus on the second visit (P < 0.05). CONCLUSION: The conventional, 1-week medication of either Ca(OH)2 or Septomixine in endodontic therapy may not effectively inhibit residual bacterial growth in all root canals during inter-appointment intervals. Further investigations using, for instance quantitative real-time PCR analyses, are required to substantiate the present findings.

Actinomycosis↗
PubMed2003

Oral colonisation by aerobic and facultatively anaerobic Gram-negative rods and yeast in Tibetans living in Lhasa.

Sample groups of children (n=50) and adults (n=38) were selected from pools of 207 children, (11-13-year olds from two primary schools) and 94 adults (25-44-year olds from four governmental agencies) who were the subjects of an oral health survey among Tibetans living in Lhasa, Tibet Autonomous Region. Mean ages of the study groups of children (38% females) and adults (61% females) were 11.6+/-0.9 and 37.1+/-6.1 years, respectively. All had lived in Tibet since birth. Oral rinse samples were selective cultured to isolate, quantify and speciate aerobic and facultatively anaerobic Gram-negative rods (using the API 20E kit) and yeasts (using API 20C AUX and API ZYM kits). For children, the isolation rates for oral coliform bacteria and yeasts were 84 and 14%, respectively, for adults, the respective rates were 26 and 40%. The corresponding quantities of coliforms/yeasts for children and adults were 0.4+/-1.6 x 10(3)c.f.u./15.8+/-72.3 and 0.2+/-0.6 x 10(3)c.f.u./57.2+/-137.5c.f.u. per millilitre oral rinse, respectively. Aerobic and facultatively anaerobic Gram-negative rods and Stenotrophomonas maltophilia, a free-living saprophytic and ubiquitous bacterial species of wide geographic distribution, were significantly more frequently recovered from the children's oral rinses. The isolation rates of facultatively anaerobic Gram-negative rods in adults and yeasts in both groups were similar to those found in similar cohorts from southern China in earlier studies. Randomly amplified polymeric DNA analysis showed that the S. maltophilia spp. isolated from children were of several different clonal types and were school specific. This study shows that the colonisation rate of facultatively anaerobic Gram-negative rods in adults and yeasts in both groups are similar to those in populations living at lower altitudes, the native young, urban Tibetans appear to exhibit a high oral carriage rate of S. maltophilia spp.

Adolescent↗
PubMed2003

Phenotypic diversity of oral C. albicans isolated on single and sequential visits in an HIV-infected Chinese cohort.

HIV-infected individuals maintain multiple oral C. albicans strains over time that are thought to undergo microevolution in terms of both phenotypic and genotypic features. To study this phenomenon, a 12-month prospective study was conducted in a cohort of 16 HIV-infected ethnic Chinese individuals with (A) and without (B) symptoms of oropharyngeal candidiasis to evaluate the phenotype distribution among oral C. albicans isolates during disease progression. Oral rinse samples were obtained and up to five C. albicans colony-forming units were selected per each visit, during the one year period of multiple visits. The isolates were phenotyped using two commercially available biotyping kits, the API 20C system, API ZYM system, and a plate test for resistance to boric acid. A total of 261 C. albicans strains in group A were differentiated into 67 biotypes, while 42 biotypes were seen amongst the 182 isolates from group B. The major biotypes in the two groups were similar and were in decreasing order of prevalence J1R, J1S, J6S, J6R, J2S, K1S, J10R, K1R, and K6R; 48 different biotypes were seen in group A and 24 in group B, with some uniquely represented in each group, leading to a significant association between the prevalence of the biotypes J1S and J2S and symptomatic candidiasis (p<0.05). Taken together this study illustrates the wide phenotypic spectrum of oral C. albicans associated with HIV-infection.

Adult↗
PubMed2003

Development of novel oligonucleotide probes for seven Actinomyces species and their utility in supragingival plaque analysis.

OBJECTIVE: The traditional, biochemical and enzymatic methods of identifying Actinomyces species are frequently confounded by the similar phenotypic characteristics shared by the different members of this genus. Therefore, we developed novel species-specific oligonucleotide probes to accurately speciate seven pathogenic Actinomyces species, namely, Actinomyces bovis, A. gerencseriae, A. israelii, A. meyeri, A. naeslundii, A. odontolyticus and A. viscosus. METHODS: A pair of universal primers and seven 15- to 19-base oligonucleotide probes with a tail of 20 thymidines on the 5' end were developed. The variable regions of 16S ribosomal DNA of 36 strains of Actinomyces belonging to the above species were amplified and labeled with digoxigenin, and an oligonucleotide-DNA hybridization assay was performed to examine the specificity and sensitivity of these probes. RESULTS: All seven, newly developed probes were specific and sensitive, and accurately detected 36 reference and wild type strains belonging to Actinomyces species, without cross-reactions. The probe for A. naeslundii detected all strains belonging to the genospecies 1 (12 strains) and catalase-negative genospecies 2 (four strains); it failed to detect catalase-positive A. naeslundii genospecies 2 (previous A. viscosus serotype II) (two strains). However, the latter strains of catalase-positive A. naeslundii genospecies 2 were correctly detected by the probe developed for A. viscosus. The new probes were then field tested using supragingival plaque samples from 28 healthy preschool children. Whilst A. odontolyticus was detected in almost all samples (96.4%), A. gerencseriae, A. meyeri, catalase-negative A. naeslundii and catalase-positive A. naeslundii genospecies 2 were detected in < 50% samples. CONCLUSION: We conclude that the developed oligonucleotide probes, complementary to the variable regions of 16S rDNA, would be of potential value for differentiating Actinomyces spp. in clinical samples from the oral cavity and other ecosystems where such species may abound.

5' Flanking Region↗
PubMed2003

Adhesion and cell-surface-hydrophobicity of sequentially isolated genetic isotypes of Candida albicans in an HIV-infected Southern Chinese cohort.

Objectives of the study were to investigate the variability in yeast adhesion and cell-surface-hydrophobicity (CSH) during human immunodeficiency virus (HIV) disease progression, using a total of 60 sequential Candida albicans isolated from oral rinse samples of seven HIV-infected individuals with (4) and without (3) clinical symptoms of oropharyngeal candidosis. Significant differences in the adhesion to buccal epithelial cells (BECs) during sequential visits were observed for all genetic isotypes in five of the seven individuals and three isotypes belonging to the sixth individual. A single isotype of patient HK1 and another of HK4 (genotype I) demonstrated significant variations in their CSH during sequential visits whereas no such differences were noted for the remaining genotypes. On Spearman correlation analysis an isotype from HK1 demonstrated a significant increased adherence to BECs and CSH during HIV disease progression whereas no such correlation was noted for the remaining isotypes studied. No significant differences in adherence to BECs or CSH values were observed between the symptomatic oral candidosis and the asymptomatic carrier group. Further, on regression analysis only the single isotype of HK1 demonstrated a significant positive correlation between adherence to BECs and CSH whereas no such correlation was observed when all tested Candida isolates were pooled and evaluated as a single, large group.

AIDS-Related Opportunistic Infections↗
PubMed2003

Amplification-based nucleic acid scanning techniques to assess genetic polymorphism in Candida.

Opportunistic pathogen Candida causes common fungal infections that manifest both superficially and systemically, especially in compromised patients. Although C. albicans is by far the main etiological agent of candidosis, the frequency of isolation of other non-albicans species such as C. glabrata and C. krusei is increasing at an alarming rate. Therefore, the epidemiology, pathogenicity, and diagnosis of infections due to these organisms are of great importance. Of a variety of genotyping methods utilized for strain delineation of these Candida species, amplification-based techniques such as randomly amplified polymorphic DNA (RAPD), amplified fragment length polymorphism (AFLP), restriction digestion-mediated PCR (RFLP-PCR), and single-stranded conformational polymorphism (SSCP) and microsatellite PCR (interrepeat PCR, IR-PCR) are the most popular and widely used. In the last decade or so these techniques have helped unravel the clinical epidemiological features of pathogenicity, diversity, microevolution, and natural heterozygosity in Candida species. Here we review in detail the basic principles of RAPD, the nature of the primer and factors influencing its selection, and the limitations of RAPD assays as well as analysis and interpretation of banding profiles generated using the software programs. In addition, the principles of other RAPD-based amplification techniques (AFLP, RFLP-PCR, SSCP, and IR-PCR) and their application in molecular epidemiologic studies of Candida species in particular and other fungi in general are also reviewed. It is concluded that these methods have wide applicability in genotyping fungi, although they differ greatly in their resolution and have advantages and drawbacks depending on the task in question.

Candida↗
PubMed2003

'Genotypic shuffling' of sequential clones of Candida albicans in HIV-infected individuals with and without symptomatic oral candidiasis.

Although HIV-infected individuals harbour multiple strains of oral Candida albicans, little is known of their micro-evolution over time. Therefore, a prospective study was conducted with 16 HIV-infected ethnic Chinese individuals with and without symptoms of oropharyngeal candidiasis to evaluate the genotype distribution of oral C. albicans isolates during HIV disease progression. Oral-rinse samples were obtained from all individuals and up to five C. albicans colonies were selected for each visit, over a 12 month period of multiple visits. After identification of isolates using standard mycological criteria, the genetic similarities of yeast isolates within and between sequential clones of C. albicans were assessed by DNA fingerprinting through random amplification of polymorphic DNA (RAPD). The results of RAPD gel profiles and the lineage of each isolate were further analysed using commercially available software. RAPD studies revealed the prevalence of up to 14 different genotypes per individual during the study period, with multiple genotypes isolated simultaneously from a single oral rinse. Computer analysis of RAPD profiles revealed that yeasts isolated over sequential visits from symptomatic individuals demonstrated a striking level of relatedness compared with isolates from asymptomatic individuals. Genetically identical C. albicans strains also formed 'loosely' connected subclusters that overlapped multiple visits, implying genetic 'shuffling' in these isolates during disease progression. These data point to varying evolutionary genetic trends in C. albicans associated with symptomatic oral candidiasis and asymptomatic carriage in HIV disease.

AIDS-Related Opportunistic Infections↗
PubMed2003

Biofilm-forming ability of Candida albicans is unlikely to contribute to high levels of oral yeast carriage in cases of human immunodeficiency virus infection.

An increased prevalence of candidal carriage and oral candidiasis is common in cases of human immunodeficiency virus (HIV) infection, and the reasons for this may include the enhanced ability of colonizing yeasts to produce biofilms on mucosal surfaces. The aim of the present study was therefore to examine the differences, if any, in the biofilm-forming abilities of 26 Candida albicans yeast isolates from HIV-infected individuals and 20 isolates from HIV-free individuals, as this attribute of yeast isolates from patients with HIV disease has not been examined before. Biofilm formation in microtiter plate wells was quantitatively determined by both the 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino) carbonyl]-2H-tetrazolium hydroxide (XTT) reduction method and the crystal violet method. Although candidal biofilm formation could be quantitatively evaluated by either technique, the better reproducibility (P < 0.05) of the XTT reduction assay compared with that of the crystal violet method led us to conclude that the former is more reliable. There were no significant quantitative differences in biofilm formation between C. albicans isolates from HIV-infected patients and isolates from HIV-free individuals during in vitro incubation in a multiwell culture system over a period of 66 h. Three of eight host factors in the HIV-infected group were found to be associated with candidal biofilm formation. Thus, yeasts isolated from older individuals and those with higher CD4-cell counts exhibited decreased biofilm formation, while the findings for yeasts from individuals receiving zidovudine showed the reverse (P < 0.05 for all comparison). Our data indicate that attributes other than biofilm formation may contribute to the increased oral yeast carriage rates in cases of HIV infection.

AIDS-Related Opportunistic Infections↗
PubMed2003

Brief exposure to antimycotics reduces the extracellular phospholipase activity of Candida albicans and Candida tropicalis.

BACKGROUND: Although the phospholipase activity is considered a potential virulence determinant of the pathogenic Candida species, the effect of antimycotics on this attribute is not known. Hence we evaluated the phospholipase activity in 10 isolates each of Candida albicans and Candida tropicalis, after their exposure to antifungals. METHODS: The impact of antimycotics on phospholipase activity was also assessed after exposure of the isolates to sub-minimum inhibitory concentrations of nystatin, amphotericin B and fluconazole. RESULTS: All Candida isolates investigated exhibited phospholipase activity (Pz). In general C. ALBICANS showed relatively higher P(z) activity than C. tropicalis , and exposure of the isolates to antimycotics led to a significant (p < 0.05) reduction in the phospholipase activity. Nystatin and amphotericin B, but not fluconazole, significantly reduced the phospholipase activity of both Candida species. CONCLUSION: These observations, while confirming the higher virulence of C. albicans relative to C. tropicalis, demonstrate for the first time the effect of antifungal agents on extracellular phospholipases of these common opportunistic pathogens.

AIDS-Related Opportunistic Infections↗
PubMed2003

Chronic hyperplastic candidosis/candidiasis (candidal leukoplakia).

Chronic hyperplastic candidosis/candidiasis (CHC; syn. candidal leukoplakia) is a variant of oral candidosis that typically presents as a white patch on the commissures of the oral mucosa. The major etiologic agent of the disease is the oral fungal pathogen Candida predominantly belonging to Candida albicans, although other systemic co-factors, such as vitamin deficiency and generalized immune suppression, may play a contributory role. Clinically, the lesions are symptomless and regress after appropriate antifungal therapy and correction of underlying nutritional or other deficiencies. If the lesions are untreated, a minor proportion may demonstrate dysplasia and develop into carcinomas. This review outlines the demographic features, etiopathogenesis, immunological features, histopathology, and the role of Candida in the disease process. In the final part of the review, newer molecular biological aspects of the disease are considered together with the management protocols that are currently available, and directions for future research.

Antifungal Agents↗
PubMed2002

Characterization, heterologous expression and functional analysis of mevalonate diphosphate decarboxylase gene (MVD) of Candida albicans.

Mevalonate diphosphate decarboxylase (MVD) catalyzes the conversion of mevalonate diphosphate to isopentenyl diphosphate, a key building block for a large family of functionally important biomolecules. We have cloned the gene encoding MVD from Candida albicans, and report the first characterization of such a gene from an opportunistic fungal pathogen. Sequence analysis revealed that the MVD comprises 362 amino acid residues with a predicted molecular weight of 39.5 kDa, sharing minimal identity with the human analogue. Analysis of the genomic sequence indicated that the coding frame is interrupted by a small intron of 51 bp. Southern analysis of genomic DNA demonstrated that MVD is a single-copy gene. Furthermore, Southern analysis of electrophoretic karyotypes of C. albicans obtained by pulsed-field gel electrophoresis showed that MVD is located on chromosome 1. Northern analysis revealed that the level of MVD expression is affected by (1) the carbon source in the growth medium, (2) the growth phase, and (3) the growth form of the fungus (yeast-like or hyphal). To demonstrate the biological function of C. albicans MVD, complementation experiments were carried out with an S. cerevisiae strain (erg19(ts)) that is temperature-sensitive for MVD activity. A single copy of the C. albicans MVD gene, under the control of the NOP1 promoter, was able fully to complement the erg19(ts) phenotype, and expression of the epitope-tagged C. albicans MVD was detectable by Western analysis. Furthermore, the low degree of sequence identity between C. albicans MVD and its human analogue raises the possibility that fungal-specific inhibitors can be developed for the enzyme. Thus, C. albicans MVD appears to be an interesting candidate that could be targeted for the development of anti-fungal agents.

Amino Acid Sequence↗
PubMed2002

The impact of polyene, azole, and DNA analogue antimycotics on the cell surface hydrophobicity of Candida albicans and Candida tropicalis in HIV infection.

Oral candidiasis is the most common opportunistic infection in individuals infected with the human immunodeficiency virus. Though Candida albicans is the major aetiological agent, non-albicans species such Candida tropicalis are now emerging as important agents of such infection. The Candida cell surface hydrophobicity (CSH) is considered a critical factor contributing to its colonization potential and virulence. It is also known that brief exposure to sub-cidal concentrations of antifungal agents is a likely scenario in the oral environment where the administered drugs are diluted continuously due to the flushing action of saliva. Hence the objective of the present study was to compare the CSH of 10 isolates each of C. albicans and C. tropicalis from HIV-infected individuals following brief exposure (1 hour) of isolates to sub-therapeutic concentrations of nystatin, amphotericin B, ketoconazole, fluconazole and 5-flurocytosine. The CSH was assessed by a previously described biphasic aqueous-hydrocarbon assay. The mean percentage reduction of CSH of C. albicans following brief exposure to nystatin, amphotericin B, ketoconazole, fluconazole and 5-flurocytosine was 27.33 (p < 0.001), 21.34 (p < 0.05), 11.74 (p > 0.05), 18.4 (p > 0.05) and 14.64 (p > 0.05) respectively. The mean percentage reduction of CSH of C. tropicalis following brief exposure to nystatin, amphotericin B, ketoconazole, fluconazole and 5-flurocytosine was 33.81 (p < 0.01), 28.88 (p < 0.01), 12.6 (p > 0.05), 21.53 (p > 0.05) and 17.68 (p > 0.05) respectively. A significant interspecies variation in CSH was observed for nystatin and amphoterecin B. Overall the results reveal that the CSH of C. albicans is affected to a significantly lesser degree compared with C. tropicalis when exposed to the antifungals. These data further illustrate another mode of action of antifungals on Candida leading to a reduction in the CSH and thereby the yeast adherence to host tissues.

AIDS-Related Opportunistic Infections↗