Relative Cell Surface Hydrophobicity Research Articles

The Influence of Urinary Catheter Materials on Forming Biofilms of Microorganisms

Biofilms are commonly associated with an increased risk of catheter-associated infection. To study the efficacy of materials designed to reduce biofilm formation, microbial biofilms on clinically used urinary catheter were examined. We performed 2, 3-bis (2-methyoxy-4-nitro-5-sulfo-phenyl)-2H-tetrazolium-5-carboxanilide (XTT) reduction assay to determine of biofilm formation ability and observed with scanning electron microscopy (SEM) to analyze biofilm architecture. Additionally, we calculated relative cell surface hydrophobicity (CSH) to measure hydrophobicity of microorganisms. On SEM, catheter surfaces made of latex or anti-infective (IC)-latex were rough but those of silicone, hydrogel-coated silicone (HCS), or silver-alloy-coated silicone (SCS) were relatively smoother. According to XTT reduction assay, biofilm formation was reduced on the surface of smooth silicone-based catheters compared to rough latex-based catheters. The greatest to lowest formation of microbial biofilm were as follows for these material types: silicone-elastomer- coated (SEC) latex > latex > silicone > IC-latex > HCS > SCS. Catheter materials can affect the microbial biofilm formations. First, rougher surfaces on the catheter made the microbial attachment easier and a greater amount of biofilm was formed. Second, when chemicals that inhibit growth and attachment of microorganisms on the inner and outer surfaces of the catheters were applied, the biofilm formation was inhibited. SCS was found to be the most effective in reducing the microbial biofilm formation. These results indicate that microbial biofilm formation may be closely related to the surface roughness and microbial CSH.

In vitro postantifungal effect, adhesion traits and haemolysin production of Candida dubliniensis isolates following exposure to 5-fluorocytosine.

The phenomenon of postantifungal effect (PAFE), which is the suppression of candidal growth following brief exposure to antifungal agents, is linked with candidal pathogenicity. Adhesion to buccal epithelial cells (BEC), germ tube (GT) formation and relative cell surface hydrophobicity (CSH) are all adhesion traits of candidal pathogenicity. Ability to produce haemolysin by Candida species is also a determinant of its pathogenicity. There is no information on either the PAFE or its impact on adhesion traits and haemolysin production of oral Candida dubliniensis isolates following exposure to 5-fluorocytosine (5-FC). Hence, the focus of this investigation was to research the in vitro PAFE, adhesion to BEC, GT formation, relative CSH and haemolysin production on 20 C. dubliniensis isolates following exposure to 5-FC. Following obtaining the minimum inhibitory concentration (MIC) of 5-FC, isolates of C. dubliniensis were exposed to sub-lethal concentrations (×3 MIC) of 5-FC for 1 h. After this brief exposure, the antimycotic was removed and PAFE, adhesion to BEC, GT formation, relative CSH and haemolysin production was determined by formerly described in vitro methods. MIC (μg/ml) of C. dubliniensis isolates to 5-FC ranged from 0.002 to 0.125. The mean PAFE (hours) elicited by 5-FC on C. dubliniensis isolates was approximately 1 h. Exposure to 5-FC suppressed the ability of C. dubliniensis isolates to adhere BEC, GT formation, relative CSH and haemolysin activity by a mean percentage reduction in 50.98%, 29.51%, 36.79% and 12.75% (P < 0.001 for all) respectively. Therefore, brief exposure of C. dubliniensis isolates to 5-FC appears to exert an antifungal effect by subduing its growth, adhesion traits as well as haemolysin production.

Distribution of Candida albicans and non-albicans Candida species in oral candidiasis patients: Correlation between cell surface hydrophobicity and biofilm forming activities

ObjectivesThe purposes of this investigation were to study the prevalence of Candida albicans and non-albicans Candida (NAC) species from oral candidiasis patients and evaluate the cell surface hydrophobicity (CSH) and biofilm forming capacity of the clinical isolates Candida species from oral cavity. DesignThis study identified a total of 250 Candida strains isolated from 207 oral candidiasis patients with PCR-RFLP technique. CSH value, total biomass of biofilm and biofilm forming ability of 117 oral Candida isolates were evaluated. ResultsC. albicans (61.6%) was still the predominant species in oral candidiasis patients with and without denture wearer, respectively, followed by C. glabrata (15.2%), C. tropicalis (10.4%), C. parapsilosis (3.2%), C. kefyr (3.6%), C. dubliniensis (2%), C. lusitaniae (2%), C. krusei (1.6%), and C. guilliermondii (0.4%). The proportion of mixed colonization with more than one Candida species was 18% from total cases. The relative CSH value and biofilm biomass of NAC species were greater than C. albicans (p<0.001). Ninety-two percent of oral isolates NAC species had biofilm forming ability, whereas 78% of C. albicans were biofilm formers. Furthermore, the significant difference of relative CSH values between biofilm formers and non-biofilm formers was observed in the NAC species (p<0.005), whereas the difference was not statistically significant in C. albicans. ConclusionThe frequency of the NAC species colonization in oral cavity was gradually increasing. The possible contributing factors might be high cell surface hydrophobicity and biofilm forming ability. The relative CSH value could be a putative factor for determining biofilm formation ability of the non-albicans Candida species.

Hydrophobic properties of Candida spp. under the influence of selected essential oils.

Processes of colonization of biotic and abiotic surfaces and biofilm formation depend inter alia on hydrophobic properties of Candida spp. The aim of this research was to determine the effect of tea tree, thyme and clove essential oils on hydrophobic properties of environmental and clinical Candida isolates. The relative cell surface hydrophobicity of strains tested was high, and ranged from 68.7% to 91.2%, with the highest value for a C. rugosa food-borne strain. The effectiveness of essential oils was diversified and depended on the type of essential oil, concentration and yeast strain. Statistically significant decrease of hydrophobicity indexes was observed after application of tea tree oil for C. krusei, clove oil for C. albicans reference strain, and all essential oils tested for C. rugosa. Only in the case of C. famata food-borne strain and C. albicans clinical isolate, solely used essential oils did not affect their hydrophobic properties. To determine the interactions of essential oils, their mixtures (1 MIC:1 MIC, 1 MIC:2 MIC and 2 MIC:1 MIC) were applied. Generally, essential oils used in combinations influenced yeast's hydrophobic properties much more than applied separately. The essential oils' mixtures reduced hydrophobicity of Candida yeasts in the range of 8.2 to 45.1%, depending on combination and strain. The interaction indexes of essential oils used in combinations predominantly indicate their additive effect. The application of tea tree, thyme and clove essential oils, especially in combinations, decreases hydrophobicity of the tested Candida isolates with implications of a probable advantageous limitation of their ability to colonize the food production industry environment.

Impact of brief and sequential exposure to nystatin, amphotericin B, ketoconazole, and fluconazole in modulating adhesion traits of oral Candida dubliniensis isolates.

Candida adherence is implicated in the pathogenesis of oral candidosis. Adhesion to buccal epithelial cells (BEC), germ tube (GT) formation, and relative cell surface hydrophobicity (CSH) are colonization attributes of candidal pathogenicity. Candida dubliniensis (C.dubliniensis) is allied with recurrent oral candidosis, which can be treated with nystatin, amphotericin B, ketoconazole, and fluconazole. Due to the diluent effect of saliva and the cleansing effect of the oral musculature in the oral cavity C.dubliniensis isolates undergo brief and sequential exposure to antifungal agents during therapy. Thus, in the present study, we evaluated the adhesion to BEC, GT formation, and the CSH of oral isolates of C.dubliniensis following brief and sequential exposure to nystatin, amphotericin B, ketoconazole, and fluconazole. After determining the minimum inhibitory concentration (MIC) of the aforementioned drugs, 20 oral isolates of C.dubliniensis were briefly (1h), and sequentially (10days) exposed to subcidal concentrations of these drugs. Following drug removal, adhesion to BEC, GT formation, and CSH of these isolates were determined. The percentage reduction of adhesion to BEC, GT formation, and CSH of the isolates following exposure to antifungal agents were as follows: nystatin: 53.55%, 33.98%, and 29.83% (P<0.001); amphotericin B: 53.84%, 36.23%, and 28.97% (P<0.001); ketoconazole: 37.43%, 20.51%, and 16.49% (P<0.001); and fluconazole: 8.93% (P<0.001), 1.6%, and 0.63% (P>0.05). Brief and sequential exposure of C.dubliniensis to antifungal agents would continue to wield an antifungal effect by altering its adhesion attributes, and elucidate possible pharmacodynamics by which antifungal agents might operate in modulating candidal adherence.

The postantifungal effect of nystatin and its impact on adhesion attributes of oral Candida dubliniensis isolates

The postantifungal effect (PAFE) has an impact on candidal pathogenicity. However, there is no information on either the PAFE or its impact on adhesion traits of oral Candida dubliniensis isolates. Oral candidosis can be treated topically with nystatin. Adhesion to buccal epithelial cells (BEC), germ tube (GT) formation and relative cell surface hydrophobicity (CSH) are all colonisation attributes of candidal pathogenicity. Hence, the main objective of this study was to investigate the in vitro PAFE on 20 C. dubliniensis isolates following exposure to nystatin. In addition, the impact of nystatin-induced PAFE on adhesion to BEC, GT formation and relative CSH of C. dubliniensis isolates were also evaluated. After determining the minimum inhibitory concentration (MIC) of nystatin, C. dubliniensis isolates were exposed to sublethal concentrations of nystatin for 1h. Following this exposure, the drug was removed and PAFE, adhesion to BEC, GT formation and relative CSH were determined by a previously described turbidometric method, adhesion assay, germ tube induction assay and biphasic aqueous-hydrocarbon assay respectively. MIC (μg/ml) of C. dubliniensis isolates to nystatin ranged from 0.09 to 0.78. The nystatin-induced mean PAFE (hours) on C. dubliniensis isolates was 2.17. Compared with the controls, exposure to nystatin suppressed the ability of C. dubliniensis isolates to adhere BEC, GT formation and relative CSH by a mean percentage reduction of 74.45% (P<0.0001), 95.92% (P<0.0001) and 34.81 (P<0.05) respectively. Hence, brief exposure of C. dubliniensis isolates to nystatin would continue to wield an antifungal effect by suppressing growth as well as its adhesion attributes.

English

Pongamia pinnata&nbsp;is used in Sri Lankan traditional medicinal systems to cure diseases including microbial infections. Different parts of this plant were investigated for&nbsp;in vitro&nbsp;anti-candidal activity. Extracts of bark, roots and leaves of&nbsp;P. pinnata&nbsp;were examined for their activity on different&nbsp;Candida&nbsp;spp. using well diffusion assay. The extract with best activity was evaluated for its minimum inhibitory concentrations (MIC) using agar dilution method. Its effects on germ tube formation, germ tube elongation and relative cell surface hydrophobicity were determined. The best activity was shown by the root extract of&nbsp;P. pinnata. Neither bark nor leaf showed positive activity. MICs of the root extracts ranged from 1.6 to 12.8 mg/ml. The treatment with root extract of&nbsp;P. pinnata&nbsp;inhibited the germ tube formation, germ tube elongation and relative cell surface hydrophobicity in a dose dependent manner. The results reveal the significant anti-candidal activity of root extracts of&nbsp;P. pinnata. &nbsp; Key words:&nbsp;Anti-candidal,&nbsp;Pongamia pinnata,&nbsp;Candida, germ tube, cell surface hydrophobicity.

Changes in germ tube formation and cell-surface hydrophobicity of oralCandida dubliniensisisolates following brief exposure to sub-cidal concentrations of polyene and azole antifungal agents

Adherence of Candida has been implicated as the initial process in the pathogenesis of oral candidosis. Candidal germ tubes and its relative cell-surface hydrophobicity (CSH) are contributory attributes. Candida dubliniensis is currently documented as an opportunistic pathogen allied with recurrent oral candidosis. Oral candidosis can be treated with polyene and azole antifungals such as amphotericin B, ketoconazole and fluconazole. However, the intraoral concentration of these drugs fluctuates and becomes sub-therapeutic because of the diluent effect of saliva and cleansing effect of the oral musculature. Hence, intraorally, the pathogenic yeast may undergo a brief exposure to antifungal drugs. The objective of this study was to investigate the effect of brief exposure to sub-lethal concentrations of these antifungals on the germ tube formation and CSH of C. dubliniensis. After determining the minimum inhibitory concentration of the drugs, 20 oral isolates of C. dubliniensis were exposed to sub-lethal concentrations of these antifungals for 1h. Following this brief exposure, the drugs were removed, and following subsequent incubation in a germ tube inducing medium and exposure to bi-phasic hydrocarbon assay, the germ tube formation and CSH of these isolates was quantified respectively. Compared with controls, exposure to amphotericin B almost completely suppressed the ability to form germ tubes with a mean percentage reduction of 95.91% (P<0.0001), whereas ketoconazole and fluconazole also significantly inhibited germ tube formation but to a lesser degree with a mean percentage reduction of 18.73% and 12.01% respectively (P<0.05). Compared with controls, exposure to amphotericin B and ketoconazole elicited a significant suppression on CSH with a mean percentage reduction of 33.09% and 21.42%, respectively (P<0.001), whereas exposure to fluconazole did not elicit a significant suppression on CSH (9.21%; P>0.05). In clinical terms it appears that, even a short exposure to sub-lethal concentrations of these drugs, a situation all too familiar in the oral environment, would continue to exert an antifungal effect by suppressing the pathogenic potency of C. dubliniensis.

Cell surface hydrophobicity of oral Candida dubliniensis isolates following limited exposure to sub‐therapeutic concentrations of chlorhexidine gluconate

Candidal adhesion has been implicated as the initial step in the pathogenesis of oral candidiasis and cell surface hydrophobicity (CSH) has been implicated in adhesion to mucosal surfaces. Candida dubliniensis is an opportunistic pathogen associated with recurrent oral candidiasis. Chlorhexidine gluconate is by far the commonest antiseptic mouth wash prescribed in dentistry. At dosage intervals the intraoral concentration of this antiseptic fluctuates considerably and reaches sub-therapeutic levels due to the dynamics of the oral cavity. Hence, the organisms undergo only a limited exposure to the antiseptic during treatment. The impact of this antiseptic following such exposure on CSH of C. dubliniensis isolates has not been investigated. Hence, the main objective of this study was to investigate the effect of brief exposure to sub-therapeutic concentrations of chlorhexidine gluconate on the CSH of C. dubliniensis isolates. Twelve oral isolates of C. dubliniensis were briefly exposed to three sub-therapeutic concentrations of 0.005%, 0.0025% and 0.00125% chlorhexidine gluconate for 30 min. Following subsequent removal of the drug, the CSH of the isolates was determined by a biphasic aqueous-hydrocarbon assay. Compared with the controls, exposure to 0.005% and 0.0025% chlorhexidine gluconate suppressed the relative CSH of the total sample tested by 44.49% (P < 0.001) and 21.82% (P < 0.018), respectively, with all isolates being significantly affected. Although exposure to 0.00125% of chlorhexidine gluconate did not elicit a significant suppression on the total sample tested (7.01%; P > 0.05), four isolates of the group were significantly affected. These findings imply that exposure to sub-therapeutic concentrations of chlorhexidine gluconate may suppress CSH of C. dublinienis isolates, thereby reducing its pathogenicity and highlights further the pharmacodynamics of chlorhexidine gluconate.

Oxidative stress response and virulence factors in Candida glabrata clinical isolates

We determined the susceptibility to oxidative stress and assessed the four virulence factors of the 38 Candida glabrata clinical isolates originating from two teaching hospitals in Slovakia. All the isolates were susceptible to hydrogen peroxide, diamide, and 7-chlorotetrazolo[5,1-c]benzo[1,2,4]triazine (CTBT) inducing an increased formation of reactive oxygen species in fungal cells. The mean relative cell surface hydrophobicity (CSH) of isolates was 21.9, ranging from 1.92 to 56.96. All isolates showed biofilm formation. A high biofilm formation was observed among 60.5% of isolates. Positive correlations were observed between biofilm formation and moderate values of CSHs. The 76.3% and 84.2% of isolates displayed varying degrees of proteinase and phospholipase activity, respectively. These results demonstrate a differential distribution of factors contributing to virulence of C. glabrata clinical isolates and point to their significance in pathogenesis that would be targeted by novel antifungals.

Intergeneric coaggregation of non-flocculating Acinetobacter spp. isolates with other sludge-constituting bacteria

The ability of non-flocculating Acinetobacter spp. isolates (A. johnsonii S35 and A. junii S33) to coaggregate with other sludge-constituting bacteria obtained from a sewage sludge sample was assessed by a spectrophotometric assay. A. johnsonii S35 showed significant coaggregation (aggregation index (AI)=70 to 99%) with 7 strains, Bacillus cereus, Blastomonas natatoria, Mycobacterium sp., Thermomonas brevis, and Enterobacteriaceae family, identified by sequencing of 16S rRNA genes. A. junii S33 coaggregated with 4 strains, which were also coaggregating partners of A. johnsonii S35, as indicated by AI values of 59-93%. The microbial adhesion to hydrocarbon (MATH) assay showed that both A. johnsonii S35 and A. junii S33 possess a hydrophobic character as indicated by their relative cell surface hydrophobicity (RCSH), 88 and 61%, respectively. A good correlation was observed between the degree of coaggregation of the Acinetobacter spp. isolates and the RCSH of their partner strains. The cells of an A. johnsonii S35 spontaneous mutant and A. johnsonii IAM1517, which had a hydrophilic cell surface, did not coaggregate with the other examined isolates. These results demonstrated that hydrophobic interaction plays an important role in the intergeneric coaggregation of Acinetobacter spp. isolates with other sludge-constituting bacteria.

Evaluation of relative yeast cell surface hydrophobicity measured by flow cytometry.

OBJECTIVE: To develop an efficient method for evaluating cell surface hydrophobicity and to apply the method to demonstrate the effects of fungal growth conditions on cell surface properties. METHODS: Yeast isolates were suspended in phosphate-buffered saline and mixed with deep blue-dyed polystyrene microspheres. Flow cytometry was used to detect the degree of microsphere binding to yeast cells. Different strains of yeast were compared for intrinsic microsphere binding activity and changes in growth conditions were invoked to modify the relative surface hydrophobicity. RESULTS: Commercially available blue-dyed polystyrene microspheres showed strong fluorescence in the FL3 channel, whereas yeast cells did not show appreciable FL3 fluorescence. Microspheres and yeast were generally distinguishable on the basis of size revealed by forward light scatter. This method showed a wide variation in intrinsic cell surface hydrophobicity among Candida albicans strains. Likewise, variation in hydrophobicity of non-albicans yeast species was observed. Growth on solid media, incubation at 25 degrees C, or 250 mg/dl glucose concentration increased hydrophobicity compared with growth in liquid media, incubation at 37 degrees C, or 50 mg/dl glucose, respectively. Growth in 1 x 10(-9) M estradiol had no appreciable effect on hydrophobicity. CONCLUSIONS: Stained latex microspheres fluoresced in the FL3 channel of the flow cytometer and bound to yeast cells to an extent related to the surface hydrophobicity of the yeast. Binding detected by flow cytometry showed that clinical yeast isolates varied in intrinsic binding capacity and this binding ability was altered by different growth conditions. The implications for virulence regulation among yeast isolates are discussed.

Evaluation of Relative Yeast Cell Surface Hydrophobicity Measured by Flow Cytometry

Objective: To develop an efficient method for evaluating cell surface hydrophobicity and to apply the method to demonstrate the effects of fungal growth conditions on cell surface properties.Methods: Yeast isolates were suspended in phosphate‐buffered saline and mixed with deep blue‐dyed polystyrene microspheres. Flow cytometry was used to detect the degree of microsphere binding to yeast cells. Different strains of yeast were compared for intrinsic microsphere binding activity and changes in growth conditions were invoked to modify the relative surface hydrophobicity.Results: Commercially available blue‐dyed polystyrene microspheres showed strong fluorescence in the FL3 channel, whereas yeast cells did not show appreciable FL3 fluorescence. Microspheres and yeast were generally distinguishable on the basis of size revealed by forward light scatter. This method showed a wide variation in intrinsic cell surface hydrophobicity among Candida albicans strains. Likewise, variation in hydrophobicity of non‐albicans yeast species was observed. Growth on solid media, incubation at 25°C, or 250 mg/dl glucose concentration increased hydrophobicity compared with growth in liquid media, incubation at 37°C, or 50 mg/dl glucose, respectively. Growth in 1 × 10−9 M estradiol had no appreciable effect on hydrophobicity.Conclusions: Stained latex microspheres fluoresced in the FL3 channel of the flow cytometer and bound to yeast cells to an extent related to the surface hydrophobicity of the yeast. Binding detected by flow cytometry showed that clinical yeast isolates varied in intrinsic binding capacity and this binding ability was altered by different growth conditions. The implications for virulence regulation among yeast isolates are discussed.

Effect of subinhibitory concentration of piperacillin/tazobactam on Pseudomonas aeruginosa.

Subinhibitory concentrations (sub-MICs) of antibiotics, although not able to kill bacteria, can modify their physico-chemical characteristics and the architecture of their outermost surface and may interfere with some bacterial functions. This study investigated the ability of sub-MIC piperacillin/tazobactam (P/T) to interfere with the bacterial virulence parameters of adhesiveness, cell-surface hydrophobicity, motility, biofilm formation and sensitivity to oxidative stress. Antimicrobial activity against five Pseudomonas aeruginosa clinical isolates, representative of clonal lineages of 96 strains of nosocomial origin, and six control strains (ATCC 27853, PAO1, AK1, MT1562, PT623, PAO1algC) was evaluated in vitro using the NCCLS microdilution method. The effects of sub-MIC on bacterial adhesion and biofilm formation were studied using a modified microtitre plate assay. The relative cell-surface hydrophobicity of P. aeruginosa strains was determined by measuring their ability to adhere to n-hexadecane. P. aeruginosa that had been exposed overnight to P/T and incubated with P/T in the plate were also screened for their ability to swim using flagella and to twitch and for their sensitivity to oxidative stress. The results obtained showed that the impact of sub-MIC P/T on bacterial characteristics was different for the various strains of P. aeruginosa. There was a change in bacterial morphology and hydrophobicity that could explain a significant decrease in adhesion values in all clinical isolates and controls tested, a decrease in biofilm formation, a significant increase in sensitivity to oxidative stress, a significant decrease in flagellum-mediated swimming and a decrease in type IV fimbriae-mediated twitching. The results obtained indicate that sub-MIC P/T interferes with the pathogenic potential of P. aeruginosa.

Hydrophobicity and surface electrostatic charge of conidia of the mycoparasitic Trichoderma species

The present investigation was done to understand the fungal-fungal interactions mechanisms based on level of nonspecific adhesion of a potential fungal mycoparasite (Trichoderma) to their fungal host (Macrophomina phaseolina). The relative cell surface hydrophobicity (CSH) and cell surface electrostatic charge (CSEC) of 29 isolates of Trichoderma species, analyzed by bacterial adhesion to hydrocarbon (BATH), hydrophobic interaction chromatography (HIC), microelectrophoresis and contact angle, revealed a large degree of variability. CSH and CSEC of conidia depended on culture age, pH and temperature. Maximum CSH and CSEC were recorded in 25–28 °C range, and both declined significantly with increasing temperature. Isolate Trichoderma hazianum (Th)-23/98 expressed surface hydrophobicity at 25–28 °C and hydrophilicity at 40 °C. Surface hydrophobicity of the isolate was susceptible to various proteases (trypsin, pepsin, proteinase k and a-chymotrypsin) and inhibitors (SDS, mercaptoethanol and Triton X-100) and a significant reduction in CSH was recorded in hydrophobic conidia. Hydrophilic conidia remained more or less unaffected by such treatments. SDS-PAGE analysis of the hydrophobic and hydrophilic conidia exhibited several protein bands in the 25 to 61 kDa range. However, each protein population contained one protein that was not observed in the other population. For hydrophobic conidia, the unique protein had an apparent molecular mass of 49 kDa, while the unique protein associated with hydrophilic conidia had a molecular mass of 61 kDa. Our findings suggest that CSH and CSEC of mycoparasitic Trichoderma may contribute to non-specific adhesion on to the sclerotial surfaces of Macrophomina phaseolina that may be influenced by growth and environmental conditions.

The impact of chlorhexidine gluconate on the relative cell surface hydrophobicity of oral Candida albicans

Adherence of Candida albicans has been implicated as the first step in the pathogenesis of oral candidosis, and its relative cell surface hydrophobicity (CSH) a contributory physical force. Chlorhexidine gluconate is by far the commonest antiseptic mouthwash prescribed in dentistry. The intra-oral concentrations of the retained chlorhexidine mouthwash fluctuate considerably due to the dilution effect of saliva and the cleansing action of the oral musculature. Hence the objective of the present study was to investigate the effect of brief exposure to sub-therapeutic concentrations of chlorhexidine gluconate on the relative CSH of C. albicans. The CSH of the isolates was assessed by a biphasic aqueous-hydrocarbon assay. A statistically significant reduction in CSH was observed following the exposure of Candida isolates to 0.005 and 0.0025% chlorhexidine gluconate. These results elucidate additional mechanisms by which chlorhexidine gluconate suppress candidal pathogenicity despite a brief period of transient exposure within the oral environment.

The impact of chlorhexidine gluconate on the relative cell surface hydrophobicity of oral Candida albicans

OBJECTIVES: Adherence of Candida albicans has been implicated as the first step in the pathogenesis of oral candidosis, and its relative cell surface hydrophobicity (CSH) a contributory physical force. Chlorhexidine gluconate is by far the commonest antiseptic mouthwash prescribed in dentistry. The intra-oral concentrations of the retained chlorhexidine mouthwash fluctuate considerably due to the dilution effect of saliva and the cleansing action of the oral musculature. Hence the objective of the present study was to investigate the effect of brief exposure to sub-therapeutic concentrations of chlorhexidine gluconate on the relative CSH of C. albicans. DESIGN: The CSH of the isolates was assessed by a biphasic aqueous-hydrocarbon assay. RESULTS: A statistically significant reduction in CSH was observed following the exposure of Candida isolates to 0.005 and 0.0025% chlorhexidine gluconate. CONCLUSIONS: These results elucidate additional mechanisms by which chlorhexidine gluconate suppress candidal pathogenicity despite a brief period of transient exposure within the oral environment.

Adhesion of Candida parapsilosis to epithelial and acrylic surfaces correlates with cell surface hydrophobicity.

We investigated in vitro adherence of 24 isolates of Candida parapsilosis and 12 isolates of Candida albicans with regard to their relative cell-surface hydrophobicity (CSH), adherence to human buccal epithelial cells (BEC) and acrylic surfaces. There was no significant interspecies difference in the relative adherence of C. parapsilosis and C. albicans isolates to BEC, although the former demonstrated a tendency for increased adherence. However, a significant intra-species variation in adherence among isolates of C. parapsilosis (P < 0.0001) to BEC, but not of C. albicans was noted. The superficial isolates of C. parapsilosis demonstrated a higher avidity (33%) to BEC than the systemic isolates. On regression analysis a significant positive correlation between C. parapsilosis adherence to BEC and denture acrylic surfaces was noted (r = 0.45, P = 0.02). Similarly, buccal cell adherence correlated strongly with CSH of C. parapsilosis (r = 0.63, P = 0.0008). These results shed further light on the intimate relationship between adherence and CSH in candidal colonization and imply that both C. parapsilosis and C. albicans are equally potent in colonizing mucosal surfaces with respect to the attributes investigated.

Influence of growth and environmental conditions on cell surface hydrophobicity ofPseudomonas fluorescensin non-specific adhesion

The relative cell surface hydrophobicity (CSH) of 18 soil isolates of Pseudomonas fluorescens, determined by phase exclusion, hydrophobic interaction chromatography (HIC), electrostatic interaction chromatography (ESIC), and contact angle, revealed large degrees of variability. Variation in the adhesion efficiency to Macrophomina phaseolina of the hyphae/sclerotia of these isolates was also examined. Two such isolates with maximum (32.8%; isolate 12-94) and minimum (12%; isolate 30-94) CSH were selected for further study. Early- to mid-log exponential cells of these isolates were more hydrophobic than those in stationary phase, and the CSH of these isolates was also influenced by fluctuations in temperatures and pH. Isolate 12-94 exhibited high CSH (32.3%) at 30 degrees C, compared to lower values (28-24%) in the higher temperature range (35-40 degrees C). Increasing concentrations of either Zn2+, Fe3+, K+, and Mg2+ in the growth medium were associated with the increased CSH. Trypsin, pepsin, and proteinase K (75 to 150 micrograms.mL-1) reduced the CSH of isolate 12-94 cells. CSH was reduced, following exposure to DTT, SDS, Triton X-100, or Tween 80. Prolonged exposure of cells to starvation (60 days) also caused a significant decline in CSH. Several protein bands (18, 21, 23, 26 kDa) of the outer cell membrane were absent in 60-day starved cells compared to unstarved cells. In conclusion, our findings demonstrate that CSH of P. fluorescens isolates may contribute to nonspecific attachment/adhesion onto M. phaseolina hyphae/sclerotia, and the efficiency of adhesion is regulated by growth and other environmental conditions.

The effect of limited exposure to antimycotics on the relative cell-surface hydrophobicity and the adhesion of oral Candida albicans to buccal epithelial cells

Candida albicans is the major aetiological agent of oral candidosis. Adhesion to oral mucosal surfaces is considered a prerequisite for its successful colonization and subsequent infection, and its relative cell-surface hydrophobicity (CSH) is a contributory physical force. Thus, the main aim here was to determine the CSH of 10 isolates of oral C. albicans after a short exposure to sublethal concentrations of four antifungal agents and to correlate these findings with their adhesion to human buccal epithelial cells (BEC). The yeasts were exposed to sublethal concentrations of nystatin [×6 minimal inhibitary concentration (MIC)], 5-fluorocytosine (×8 MIC), ketoconazole (×4 MIC) and fluconazole (×4 MIC) for 1 h. The drug was then removed, and the CSH and BEC adhesion assessed by a biphasic aqueous–hydrocarbon assay and a microscopic method, respectively. The mean percentage reductions of CSH after exposure to nystatin, 5-fluorocytosine, ketoconazole and fluconazole were 27.14% ( p=0.01), 9.46% ( p=0.43), 19.47% ( p=0.04) and 6.16% ( p=0.59). Similarly, exposure to all the drugs except 5-fluorocytosine resulted in a significant inhibition of yeast adhesion to BEC, with nystatin eliciting the highest and fluconazole the least inhibition. Further, on regression analysis a strong positive correlation was observed between CSH and adhesion to BEC after limited exposure to 5-fluorocytosine ( r=0.48, p<0.0001), ketoconazole ( r=0.48, p<0.0001), fluconazole ( r=0.55, p<0.0001) as well as in the unexposed controls ( r=0.41, p=0.001), although nystatin was an exception ( r=0.09, p=0.44). Taken together, these data elucidate further mechanisms by which antimycotics may operate in vivo to suppress candidal pathogenicity.