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Anti-Candida and mode of action of two newly synthesized polymers: a modified poly (methylmethacrylate-co-vinylbenzoylchloride) and a modified linear poly (chloroethylvinylether-co-vinylbenzoylchloride) with special reference to Candida albicans and Candida tropicalis.

Polymeric antimicrobial agents represent a new and important direction that is developing in the field of antimicrobial agents. Antimicrobial activity of two newly synthesized polymers: a modified poly (methylmethacrylate-co-vinylbenzoylchloride) and a modified linear poly (chloroethylvinylether-co-vinylbenzoylchloride) have been investigated and found to be active. Both polymers have showed a broad antimicrobial activity against C. albicans and C. tropicalis. Minimal inhibitory concentrations (MIC's) for poly (methylmethacrylate-co-vinylbenzoyl chloride) were 100, 75 and 100 microg/ml in case of C. albicans (ATCC 2091), C. albicans (SC5314) and C. tropicalis, respectively. However, polycholoroethylvinylether-covinylbenzoylchloride inhibited C. albicans (ATCC 2091), C. albicans (SC5314) and C. tropicalis with minimum inhibitory concentration values (MIC's) of 150 microg/ml against the three tested Candida strains. Mode of action studies of both polymers on the medically important yeasts, C. albicans and C. tropicalis revealed that poly (methylmethacrylate-co-vinylbenzoylchloride) induced cytotoxicity, DNA damage, and altered cell permeability and morphology, which was manifested as aggregated and swollen yeast cells (C. albicans ATCC 2091) by fluorescent microscopy examination. Poly (chloroethylvinylether-co-vinylbenzoylchloride) increased cell permeability, and respiration for C. albicans and C. tropicalis. The tested polymers at 50 microg/ml had pronounced effects on C. albicans and C. tropicalis cell wall phosphopeptidomannane, proteins, sugars and phosphorus. Generally, the two polymers proved effective against the tested microorganisms, but growth inhibitory effect varied according to the composition of the polymer active group. Many investigators consider polymeric antimicrobial agents as a potential new approach for enhancing the efficiency of some existing antimicrobial agents, including prolonged activity, reduce their toxicity, as well as reduce the environmental issues associated with product use.

Antifungal Agents↗

Characterizing the effects of caspofungin on Candida albicans, Candida parapsilosis, and Candida glabrata isolates by simultaneous time-kill and postantifungal-effect experiments.

We measured time-kills and postantifungal effects (PAFEs) of caspofungin against Candida albicans, C. parapsilosis, and C. glabrata isolates. One-hour exposure to caspofungin during PAFE experiments accounted for the majority of killing during time-kill experiments. Regrowth of all isolates was inhibited for at least 24 h following drug washout.

Antifungal Agents↗

Candida albicans and Candida stellatoidea, in contrast to other Candida species, bind iC3b and C3d but not C3b.

It was demonstrated that complement-coated sheep erythrocytes bind to Candida albicans cells grown in serum-free RPMI 1640 medium. Testing of purified complement components proved that iC3b and C3d were responsible for the reaction, whereas C3b and C3b-H reacted only slightly if at all. Binding occurred only to C. albicans and C. stellatoidea, not to other species pathogenic to humans. There was evidence of a lectinlike nature of the effect.

Animals↗

Species differentiation by internally transcribed spacer PCR and HhaI digestion of fluconazole-resistant Candida krusei, Candida inconspicua, and Candida norvegensis strains.

PCR amplification of the regions containing the internally transcribed spacers and 5.8S rRNA gene of Candida krusei, C. inconspicua, and C. norvegensis yielded fragments of 510, 460, and 500 bp, respectively. HhaI digestion of these fragments yielded species-specific bands. Random amplification of polymorphic DNA with primer R108 showed interspecific discriminatory band patterns. Susceptibilities to fluconazole and amphotericin B were determined.

Antifungal Agents↗

Candida orthopsilosis and Candida metapsilosis spp. nov. to replace Candida parapsilosis groups II and III.

Two new species, Candida orthopsilosis and C. metapsilosis, are proposed to replace the existing designations of C. parapsilosis groups II and III, respectively. The species C. parapsilosis is retained for group I isolates. Attempts to construct a multilocus sequence typing scheme to differentiate individual strains of C. parapsilosis instead revealed fixed DNA sequence differences between pairs of subgroups in four genes: COX3, L1A1, SADH, and SYA1. PCR amplicons for sequencing were obtained for these four plus a further seven genes from 21 group I isolates. For nine group II isolates, PCR products were obtained from only 5 of the 11 genes, and for two group III isolates PCR products were obtained from a different set of 5 genes. Three of the PCR products from group II and III isolates differed in size from the group I products. Cluster analysis of sequence polymorphisms from COX3, SADH, and SYA1, which were common to the three groups, consistently separated the isolates into three distinct sets. All of these differences, together with DNA sequence similarities <90% in the ITS1 sequence, suggest the subgroups should be afforded species status. The near absence of DNA sequence variability among isolates of C. parapsilosis and relatively high levels of sequence variability among isolates of C. orthopsilosis suggest that the former species may have evolved very recently from the latter.

Base Sequence↗

Sterol content and polyene antibiotic resistance in isolates of Candida krusei, Candida parakrusei, and Candida tropicalis.

Three isolates, one from each species of Candida krusei, C. parakrusei, and C. tropicalis, obtained from infected patients, were more tolerant of significantly higher concentrations of polyene antibiotics than the corresponding reference wild types. The resistant strains isolated had the same sterols as their wild-type counterparts but in lower concentrations.

Amphotericin B↗

Structure-based specificity mapping of secreted aspartic proteases of Candida parapsilosis, Candida albicans, and Candida tropicalis using peptidomimetic inhibitors and homology modeling.

Secreted aspartic proteases (Saps) of pathogenic Candida spp. represent a specific target for antifungal drug development. We synthesized a series of peptidomimetic inhibitors with different isosteric groups and modifications at individual positions and tested them with purified Saps from C. albicans (Sap2p), C. tropicalis (Sapt1p), and C. parapsilosis (Sapp1p). The kinetic parameters indicated that all three proteases prefer binding of inhibitors containing bulky hydrophobic residues between positions P3 and P3'. The most divergent specificity was found for Sapp1p. The sequence alignment of Sap2p, Sapt1p, and Sapp1p, and homology modeling of Sapp1p with the crystal structure of Sapt1p and the complex of Sap2p with a peptidomimetic inhibitor showed that the overall folds of Sap2p, Sapt1p, and Sapp1p are similar. However, the N- and C-terminal loops formed by disulfide bonds between residues 47-53 and 258-292 are significantly shorter in Sapp1p, and a unique insertion following Tyr 129 in Sapp1p results in the formation of a loop that can interact with inhibitor residues. These Sapp1p structural differences might lead to its altered susceptibility to inhibition.

Amino Acid Sequence↗

Expansion of the Candida tanzawaensis yeast clade: 16 novel Candida species from basidiocarp-feeding beetles.

A major clade of new yeast taxa from the digestive tract of basidiocarp-feeding beetles is recognized based on rRNA gene sequence analyses. Almost 30 % of 650 gut isolates formed a statistically well-supported clade that included Candida tanzawaensis. The yeasts in the clade were isolated from 11 families of beetles, of which Tenebrionidae and Erotylidae were most commonly sampled. Repeated isolation of certain yeasts from the same beetle species at different times and places indicated strong host associations. Sexual reproduction was never observed in the yeasts. Based on comparisons of small- and large-subunit rRNA gene sequences and morphological and physiological traits, the yeasts were placed in Candida ambrosiae and in 16 other undescribed taxa. In this report, the novel species in the genus Candida are described and their relationships with other taxa in the Saccharomycetes are discussed. The novel species and their type strains are as follows: Candida guaymorum (NRRL Y-27568(T)=CBS 9823(T)), Candida bokatorum (NRRL Y-27571(T)=CBS 9824(T)), Candida kunorum (NRRL Y-27580(T)=CBS 9825(T)), Candida terraborum (NRRL Y-27573(T)=CBS 9826(T)), Candida emberorum (NRRL Y-27606(T)=CBS 9827(T)), Candida wounanorum (NRRL Y-27574(T)=CBS 9828(T)), Candida yuchorum (NRRL Y-27569(T)=CBS 9829(T)), Candida chickasaworum (NRRL Y-27566(T)=CBS 9830(T)), Candida choctaworum (NRRL Y-27584(T)=CBS 9831(T)), Candida bolitotheri (NRRL Y-27587(T)=CBS 9832(T)), Candida atakaporum (NRRL Y-27570(T)=CBS 9833(T)), Candida panamericana (NRRL Y-27567(T)=CBS 9834(T)), Candida bribrorum (NRRL Y-27572(T)=CBS 9835(T)), Candida maxii (NRRL Y-27588(T)=CBS 9836(T)), Candida anneliseae (NRRL Y-27563(T)=CBS 9837(T)) and Candida taliae (NRRL Y-27589(T)=CBS 9838(T)).

Animals↗

Rapid and unequivocal differentiation of Candida dubliniensis from other Candida species using species-specific DNA probes: comparison with phenotypic identification methods.

Candida dubliniensis is a recently described opportunistic pathogen which shares many phenotypic characteristics with Candida albicans but which has been reported to rapidly acquire resistance to azole antifungal drugs. Therefore, differentiation of C. dubliniensis from C. albicans becomes important to better understand the clinical significance and epidemiologic role of C. dubliniensis in candidiasis. We compared phenotypic methods for the differentiation of C. dubliniensis from C. albicans (i.e. the ability to grow at elevated temperatures, colony color on CHROMagar Candida medium, and carbohydrate assimilation patterns) to amplify the results of a polymerase chain reaction (PCR) assay using universal fungal primers to the internal transcribed spacer 2 (ITS2) region of rDNA and species-specific DNA probes in an enzyme immunoassay format (PCR-EIA). DNA sequencing of the ITS1 rDNA region was also conducted. The C. dubliniensis ITS2 probe correctly identified all C. dubliniensis isolates without cross-reaction with any other Candida species tested (mean A(650 nm) +/- SE, C. dubliniensis probe with C. dubliniensis DNA, 0.372 +/- 0.01, n = 22; C. dubliniensis probe with other Candida species DNA, 0.001 +/- 0.02 n = 16, P < 0.001). All other Candida species tested (C. albicans, Candida glabrata, Candida krusei, Candida parapsilosis, and Candida tropicalis) were also correctly identified by the PCR-EIA without any detectable cross-reactions among species. Phenotypically, C. dubliniensis isolates demonstrated an increased sensitivity to heat compared to C. albicans isolates. At 42 degrees C, only 50% of C. dubliniensis isolates grew compared to 73% of C. albicans isolates and, at 45 degrees C, 91% of C. dubliniensis isolates failed to grow compared to 64% of C. albicans isolates. C. albicans was more likely to demonstrate a dark green or blue green colony color on CHROMagar Candida medium obtained from Becton Dickinson (i.e. 100% of C. albicans isolates were dark green or blue green versus 64% of C. dubliniensis isolates) whereas no difference in the percentage of C. albicans or C. dubliniensis isolates producing dark green or blue green colony color was detected using CHROMagar Candida medium from Hardy Diagnostics (82% for both species). The API 20C AUX carbohydrate assimilation system incorrectly identified C. dubliniensis as C. albicans in all but three cases: remaining isolates were misidentified as C. albicans/C. tropicalis, C. tropicalis/C. albicans, and Candida lusitaniae/C. albicans. In all, 82% of C. albicans isolates and 100% of C. dubliniensis isolates assimilated trehalose; the latter finding was opposite to that reported for C. dubliniensis in the API 20C AUX profile index. Xylose and alpha-methyl-D-glucoside assimilation, respectively, were negative for 100 and 95% of C. dubliniensis isolates and positive for 100 and 91% of C. albicans isolates, confirming earlier reports that assimilation results for xylose and alpha-methyl-D-glucoside may be helpful in the discrimination of these two species. However, conventional phenotypic species identification tests required days for completion, whereas the PCR-EIA could be completed in a matter of hours. In addition, identification of Candida species by ITS1 rDNA sequencing gave 100% correspondence to the results obtained by the PCR-EIA, confirming the specificity of the PCR-EIA method. These data indicate that although a combination of phenotypic methods may help differentiate C. dubliniensis from C. albicans to some extent, the PCR-EIA can provide a simple, rapid, and unequivocal identification of the most medically important Candida species in a single test.

Candida↗

Usefulness of Candida ID2 agar for the presumptive identification of Candida dubliniensis.

CHROMagar Candida and Candida ID2 are widely used for the isolation and presumptive identification of Candida spp. based on the color of the colonies on these two media. We have studied the usefulness of these chromogenic media for differentiating Candida dubliniensis from Candida albicans isolates. One hundred isolates of C. dubliniensis and 100 C. albicans isolates were tested on Candida ID2, CHROMagar Candida (CHROMagar), and CHROMagar Candida reformulated by BBL. CHROMagar Candida and CHROMagar Candida BBL did not allow a clear differentiation of the two species based upon the shade of the green color of C. dubliniensis colonies. However, on Candida ID2, all C. dubliniensis isolates produced turquoise blue colonies whereas 91% of C. albicans colonies were cobalt blue. The sensitivity and the specificity for differentiating between C. dubliniensis fromC. albicans on Candida ID2 were 100% and 91%, respectively; whereas on CHROMagar Candida these values were 63% and 89% and on CHROMagar Candida BBL they were 18% and 98%. Candida ID2 agar provides a simple and accurate laboratory approach for the identification and differentiation of C. dubliniensis on the basis of the colony color.

Agar↗

[Evaluation of a new chromogenic medium (Candida ID) for the isolation and presumptive identification of Candida albicans and other medically important yeasts].

Candidiasis is a frequent human infection caused mainly by Candida albicans. However, other species are emerging as important pathogens, as Candida glabrata, Candida parapsilosis, Candida tropicalis, Candida krusei or Candida guilliermondii. Rapid identification of clinical isolates could facilitate diagnosis and treatment. Candida ID (bioMerieux, Spain) is a new medium for the isolation and presumptive identification of yeasts: C. albicans grows as blue colonies, and C. tropicalis, C. guilliermondii, Candida kefyr and Candida lusitaniae as pink ones. The utility of Candida ID was evaluated with more than 700 clinical isolates and type culture collection strains from different genera including Candida, Cryptococcus, Saccharomyces, and Rhodotorula. Presumptive identification was confirmed by germ tube test, microscopic morphology and chlamydoconidia production on corn meal agar and carbohydrate assimilation on API-ATB ID 32C or Vitek (bioMerieux). Growth on Candida ID was rapid (18-24 h) for most of the yeast strains tested. Sensitivity and specificity of identification of C. albicans was significantly high (>98%), since a very low number of isolates were found to be false negative or false positive. A better result was obtained for species growing as pink colonies (>99.5%). Detection of different species of medical important yeasts was easy with Candida ID, as perfectly distinct colors and textures of colonies were observed on this medium. Candida ID allowed the discrimination between C. glabrata (creamy and smooth) and C. krusei (rough and white) colonies. Other species showed different colony textures and colours, white being the predominant colour. Candida ID was very useful for the presumptive identification C. albicans isolates.

English Abstract↗

Direct isolation of Candida spp. from blood cultures on the chromogenic medium CHROMagar Candida.

CHROMagar Candida is a selective and differential chromogenic medium that has been shown to be useful for identification of Candida albicans, Candida krusei, Candida tropicalis, and perhaps Candida glabrata. Colony morphology and color have been well defined when CHROMagar Candida has been used to isolate yeast directly from clinical specimens, including stool, urine, respiratory, vaginal, oropharyngeal, and esophageal sources. Direct isolation of yeast on CHROMagar Candida from blood cultures has not been evaluated. We evaluated whether the color and colony characteristics produced by Candida spp. on CHROMagar Candida were altered when yeasts were isolated directly from blood cultures. Fifty clinical isolates of Candida were inoculated into aerobic and anaerobic blood culture bottles and incubated at 35 degrees C in an automated blood culture system. When growth was detected, an aliquot was removed and plated onto CHROMagar Candida. As a control, CHROMagar Candida plates were inoculated with the same isolate of yeast grown on Sabouraud dextrose agar simultaneously. No significant difference was detected in color or colony morphology between the blood and control isolates in any of the tested organisms. All C. albicans (n = 12), C. tropicalis (n = 12), C. glabrata (n = 9), and C. krusei (n = 5) isolates exhibited the expected species-specific colony characteristics and color, whether isolated directly from blood or from control cultures. CHROMagar Candida can be reliably used for direct isolation of yeast from blood cultures. Direct isolation could allow mycology laboratories to more rapidly identify Candida spp., enable clinicians to more quickly make antifungal agent selections, and potentially decrease patient morbidity and mortality.

Aerobiosis↗

Mixed oropharyngeal candidiasis due to Candida albicans and non-albicans Candida strains in HIV-infected patients.

In order to determine the clinical significance of mixed oropharyngeal candidiasis (Candida albicans plus a non-albicans strain of Candida) in patients infected with HIV-1, a retrospective chart review was done in 12 HIV-1-infected patients with a clinical episode of oropharyngeal candidiasis, in whom a mixed culture of Candida albicans (found to be fluconazole-sensitive) plus a non-albicans species of Candida was obtained from their oral cavities. This group was compared with 26 HIV-positive patients (control group) with oropharyngeal candidiasis due to Candida albicans (found to be fluconazole-sensitive). Antifungal susceptibility testing was performed by a broth microdilution test with RPMI-2% glucose. A fungal strain was considered fluconazole-sensitive if its MIC was < 0.5 micrograms/ml. Both the study and control groups had similar clinical and demographic characteristics. All the patients were severely immunocompromised, with a mean CD4+ lymphocyte count of 63/mm3 (95% CI 41-84) and 80/mm3 (95% CI 25-135) in the study and control groups, respectively. In the study group, seven patients had Candida albicans and Candida krusei in their oral cavity, four had Candida albicans and Candida glabrata, and one had Candida albicans and Candida tropicalis. Antifungal therapy consisted of ketoconazole (5 patients in the study group, 14 in the control group) or fluconazole (7 patients in the study group, 12 in the control group); no statistically significant difference in clinical outcome was observed. Fungal strain persistence after therapy was frequently observed in both groups. It is concluded that non-albicans strains of Candida, less sensitive to azole drugs than their Candida albicans counterparts, are not clinically relevant in episodes of mixed oropharyngeal candidiasis in HIV-1-infected patients.

AIDS-Related Opportunistic Infections↗

Analysis of the Candida albicans - specific T-cell response and oropharyngeal Candida colonization in a cohort of HIV-1-infected patients.

To investigate Candida epidemiology and immunologic correlates of protection in HIV-1 infected patients, we analyzed oral Candida colonization in correlation to the Candida-specific T-cell response measured by g-IFN ELISPOT using different Candida (C.) albicans strains. In 16/46 patients (13 asymptomatic, 3 with oral thrush), but in 0/28 controls, Candida (13 C. albicans, 1 C. lusitaniae, 1 C. krusei, 1 C. parapsilosis) was isolated. Candida specific T-cells were detected more frequently in controls (20/28) than in HIV-1+ subjects (16/46, p= 0.03). We observed a significant association of higher CD4 cell numbers with both detection of Candida specific T-cells and lack of oral Candida colonization, but there was no significant correlation of oral Candida colonization to the detection of Candida specific T-cells, viral load or antiretroviral therapy. Thus, local mucosal immunity seems to be more important in the pathogenesis of Candida colonization than circulating Candida specific T-cells. The pathogenic C. albicans strain K24122 was less frequently recognized by patients (6/46) than the laboratory adapted strain SC5314 (14/46, p= 0.03), whereas a similar recognition of both strains was observed in healthy controls. This indicates an impaired Candida-specific T-cell repertoire in HIV+ patients that could increase the risk of immune evasion by C. albicans.

AIDS-Related Opportunistic Infections↗

The effect of sodium hypochlorite on potential pathogenic traits of Candida albicans and other Candida species.

Strains of Candida albicans, Candida krusei, Candida kefyr, Candida tropicalis, Candida parapsilosis and Candida guilliermondii were grown in the presence or absence of concentrations of sodium hypochlorite below the minimal inhibitory concentration and tested for a range of characteristics that may be associated with pathogenicity. Sodium hypochlorite is used routinely in hospitals in Australia for disinfection procedures, and these experiments were designed to assess the efficacy of hypochlorite as a sterilizing agent for acrylic dentures. Candida showed varying abilities to adhere to surfaces that may be present in the oral cavity. Sodium hypochlorite reduced the adhesion of all C. albicans strains and most other Candida species to both polystyrene and buccal epithelial cells. A biofilm of Streptococcus gordonii reduced the adhesion of most C. albicans strains and most other Candida species to polystyrene. However, Candida species were able to coaggregate with S. gordonii in suspension, with one strain of C. albicans, GDH 2346, showing greater coaggregating ability than the other strains or species. Sodium hypochlorite increased coaggregation of all C. albicans strains and most other Candida species. Examination of cell wall proteins from strains of C. albicans and a strain of C. parapsilosis showed that growth in hypochlorite increased the amount of protein in some existing bands and, in one strain of C. albicans, increased the number of detectable protein bands ranging from 56 to 26 kDa. Only 4 strains of C. albicans were able to produce hyphae, and 3 of these same strains and C. parapsilosis were able to produce proteinase. Hypochlorite increased the rate of blastospore to hyphal transition but had no effect on proteinase production or activity. It is concluded that hypochlorite at a concentration below the minimal inhibitory concentration may function as an anti-adhesin for Candida species but may not affect their more pathogenic characteristics.

Acrylic Resins↗

[Distribution of Candida species in vaginal specimens and evaluation of CHROMagar Candida medium].

Identification of Candida species is important to guide treatment in vulvovaginal candidiasis which is seen frequently and needs long-term therapy due to recurrence. The aim of this study was to determine the species distribution of Candida isolated from vaginal specimens and evaluation of CHROMagar Candida medium in the laboratory diagnosis. Samples from 80 patients who were clinically diagnosed as vaginitis have been analysed in our laboratory. Colonies appeared on CHROMagar Candida media after 48 hours of incubation at 35 degrees C were evaluated for their colors and characteristics. Candida strains were identified by germ tube test, growth on corn meal Tween 80 agar and when necessary also by API 20 C AUX commercial kit. A total of 84 Candida strains were isolated from 80 patients. Two different Candida species have been isolated from four (5%) of the samples. Among Candida strains isolated, 45 (53.6%) were C. albicans, 29 (34.5%) C. glabrata, 7 (8.3%) C. krusei, and 3 (3.6%) C. kefyr. All of the C. albicans and six of the seven C. krusei isolates have been identified correctly by CHROMagar Candida medium. These results showed that C. albicans is still the most frequently isolated species from vaginal samples. It was concluded that CHROMagar Candida medium is useful for identification of colonies due to frequently seen Candida species and also in differentiation of multiple Candida species grown on the same culture.

Candida↗