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ABSTRACTUrinary tract infections (UTIs) are the most common type of nosocomial infection, and Candida albicansis the most frequent organism causing fungal UTIs. Presence of an indwelling urinary catheter represents a significant risk factor for UTIs. Furthermore, these infections are frequently associated with the formation of biofilms on the surface of these catheters. Here, we describe the characterization of C. albicansbiofilms formed in vitro using synthetic urine (SU) medium and the frequently used RPMI medium and compare the results. Biofilms of C. albicansstrain SC5314 were formed in 96-well microtiter plates and on silicon elastomer pieces using both SU and RPMI media. Biofilm formation was monitored by microscopy and a colorimetric XTT [2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide] reduction assay. As in biofilms grown in RPMI medium, time course studies revealed that biofilm formation using SU medium occurred after an initial adherence phase, followed by growth, proliferation, and maturation. However, microscopy techniques revealed that the architectural complexity of biofilms formed in SU medium was lower than that observed for those formed using RPMI medium. In particular, the level of filamentation of cells within the biofilms formed in SU medium was diminished compared to those in the biofilms grown in RPMI medium. This observation was also corroborated by expression profiling of five filamentation-associated genes using quantitative real-time reverse transcriptase PCR. Sessile C. albicanscells were resistant to fluconazole and amphotericin B, irrespective of the medium used to form the biofilms. However, caspofungin exhibited potent in vitro activity at therapeutic levels against C. albicansbiofilms grown in both SU and RPMI media.

ABSTRACTOral yeast carriage was studied in 312 Mexican subjects. Candida albicanswas the most frequent species, but other Candidaspp. were isolated from 16.5 to 38.5% of patients. Colonization did not correlate with CD4+number or viral load, but highly active antiretroviral therapy reduced the frequency of candidiasis. Most isolates were susceptible to fluconazole, but 10.8% were resistant to one or more azoles.

ABSTRACTCandida glabratahas emerged in recent years as a significant cause of systemic fungal infection. We have previously reported on the first three patients receiving radiation for head and neck cancer to develop oropharyngeal candidiasis due to C. glabrata. The goal of this study was to track the development of increased fluconazole resistance in C. glabrataisolates and to evaluate previously described genetic mechanisms associated with this resistance from one of these three patients. The patient was a 52-year-old man with squamous cell carcinoma treated with radiation. At week 7 of his radiation, he developed oropharyngeal candidiasis, which was treated with 200 mg of fluconazole daily for 2 weeks. Serial cultures from this and three subsequent time points yielded C. glabrata. Isolates from these cultures were subjected to antifungal susceptibility testing, DNA karyotyping, and evaluation of the expression of genes previously associated with C. glabrataresistance to fluconazole, CgCDR1, CgCDR2, and CgERG11. Two strains (A and B) of C. glabratawere identified and found to display different patterns of resistance development and gene expression. Strain A developed resistance over a 2-week period and showed no overexpression of these genes. In contrast, strain B first showed resistance 6 weeks after fluconazole therapy was discontinued but showed overexpression of all three genes. In conclusion, development of resistance to fluconazole by C. glabratais a highly varied process involving multiple molecular mechanisms.

ABSTRACTOral mucosal colonization and infection with Candidaare common in patients receiving radiation therapy for head and neck cancer. Infection is marked by oral pain and/or burning and can lead to significant patient morbidity. The purpose of this study was to identify Candidastrain diversity in this population by using a chromogenic medium, subculturing, molecular typing, and antifungal susceptibility testing of clinical isolates. These results were then correlated with clinical outcome in patients treated with fluconazole for infection. Specimens from 30 patients receiving radiation therapy for head and neck cancer were cultured weekly forCandida. Patients exhibiting clinical infection were treated with oral fluconazole. All isolates were plated on CHROMagar Candida and RPMI medium, subcultured, and submitted for antifungal susceptibility testing and molecular typing. Infections occurred in 27% of the patients and were predominantly due to Candida albicans(78%). Candidacarriage occurred in 73% of patients and at 51% of patient visits. Yeasts other than C. albicanspredominated in carriage, as they were isolated from 59% of patients and at 52% of patient visits. All infections responded clinically, and all isolates were susceptible to fluconazole. Molecular typing showed that most patients had similar strains throughout their radiation treatment. One patient, however, did show the acquisition of a new strain. With this high rate of infection (27%), prophylaxis to prevent infection should be evaluated for these patients.

ABSTRACTCandida dubliniensishas been associated with oropharyngeal candidiasis in patients infected with human immunodeficiency virus (HIV). C. dubliniensisisolates may have been improperly characterized as atypical Candida albicansdue to the phenotypic similarity between the two species. Prospective screening of oral rinses from 63 HIV-infected patients detected atypical dark green isolates on CHROMagar Candida compared to typical C. albicansisolates, which are light green. Forty-eight atypical isolates and three control strains were characterized by germ tube formation, differential growth at 37, 42, and 45°C, identification by API 20C, fluorescence, chlamydoconidium production, and fingerprinting by Ca3 probe DNA hybridization patterns. All isolates were germ tube positive. Very poor or no growth occurred at 42°C with 22 of 51 isolates. All 22 poorly growing isolates at 42°C and one isolate with growth at 42°C showed weak hybridization of the Ca3 probe with genomic DNA, consistent with C. dubliniensisidentification. No C. dubliniensisisolate but only 18 of 28 C. albicansisolates grew at 45°C. Other phenotypic or morphologic tests were less reliable in differentiating C. dubliniensisfrom C. albicans. Antifungal susceptibility testing showed fluconazole MICs ranging from =0.125 to 64 µg/ml. Two isolates were resistant to fluconazole (MIC, 64 µg/ml) and one strain was dose dependent susceptible (MIC, 16 µg/ml). MICs of other azoles, including voriconazole, itraconazole, and SCH 56592, for these isolates were lower. C. dubliniensiswas identified in 11 of 63 (17%) serially evaluated patients. Variability in phenotypic characteristics dictates the use of molecular and biochemical techniques to identifyC. dubliniensis. This study identifies C. dubliniensisin HIV-infected patients from San Antonio, Tex., and shows that C. dubliniensisis frequently detected in those patients by using a primary CHROMagar screen.