In vitro activity of fluconazole, voriconazole and caspofungin against clinical yeast isolates.

Predicting the clinical outcome of a systemic mycosis is often a difficult task, especially when microbiological resistance is one of the factors contributing to therapeutic failure. Some of these factors are host-related--e.g. immune state, site and severity of infection, poor compliance to therapy--while others are associated with the drug's characteristics--e.g. dosage, type of compound (fungistatic/fungicidal), pharmacokinetic properties and drug-drug interactions. In the last few years, clinicians have been confronted with the problem of selecting the most appropriate antifungal therapy for systemic infections and have highlighted the need for a reliable method to assay the in vitro susceptibility of yeasts and molds to different antifungal agents, which would allow them to institute a tailored therapy. Using the CLSI micromethod--the reference method for clinically relevant yeast testing--we assayed 70 clinical yeast isolates ( Candida spp., collected from patients with systemic mycosis) for susceptibility against fluconazole, voriconazole and caspofungin. Data obtained from our in vitro susceptibility assays revealed good activity of azoles against the majority of Candida spp. In particular, 88.6% of the assayed isolates were susceptible to fluconazole, with minimum inhibitory concentrations (MICs) ranging from =0.125 microg/mL to 8 microg/mL; 97.1% of the isolates were susceptible to voriconazole, with MICs ranging from 0.008 microg/mL to 1 microg/mL; regarding caspofungin 72.9% of the isolates had MICs ranging from 0.25 microg/mL to 1 microg/mL.

Identification of Candida dubliniensis among oral yeast isolates from an Italian population of human immunodeficiency virus-infected (HIV+) subjects.

Candida dubliniensis, an emerging oral pathogen, phenotypically resembles Candida albicans so closely that it is easily misidentified as such. The aim of the present study was to evaluate the usefulness of two phenotypic methods, growth at 45 degrees C and 2,3,5-triphenyltetrazolium chloride (TTC) reduction, for confirming presumptive identification of C. dubliniensis and C. albicans by colony color on CHROMagar Candida (CAC) medium. A combination of these methods was used to establish the prevalence of oral C. dubliniensis in an Italian population of 45 human immunodeficiency virus (HIV)-infected subjects. Twenty-two samples (48.9%) were positive for yeasts on CAC medium producing a total of 37 fungal isolates. The colony color and 45 degrees C growth ability test correctly identified all C. dubliniensis and C. albicans isolates (5/37, 13.5%, and 16/37, 43.2%, respectively), while assessment of TTC reduction misidentified one C. albicans isolate. The isolation rate of C. dubliniensis was 11.1% (5/45 patients). All of the C. dubliniensis isolates were highly susceptible to fluconazole (MIC = 0.5 microg/ml). The combination of CAC medium screening with growth at 45 degrees C and TTC reduction tests may represent a simple, reliable and inexpensive identification protocol for C. dubliniensis.

Genotyping and antifungal susceptibility of human subgingival Candida albicans isolates.

Subgingival colonization by Candida albicans has been described in human immunodeficiency virus (HIV)-infected individuals, but subgingival isolates have scarcely been characterized, particularly with respect to genotype and antifungal susceptibility. A series of 29 subgingival strains of C. albicans isolated from nine HIV-infected individuals was typed by electrophoretic karyotyping and tested for susceptibility to fluconazole, itraconazole, the new investigational triazole posaconazole and amphotericin B. DNA typing showed genetic heterogeneity within subgingival isolates, as almost every individual harbored his/her own specific isolate. Genetic identity was usually demonstrated within oral and subgingival isolates simultaneously collected from the same individual, but a number of DNA types were found to be unique to subgingival strains. These findings suggest that colonization is not just the result of Candida spreading from oral surfaces, and that subgingivally adapted strains could be involved. All isolates were susceptible to all the triazole drugs tested and amphotericin B. Additional studies on subgingival Candida colonization and further characterization of subgingival isolates are now required to clarify the role of Candida as opportunistic periodontal pathogen.

Fluconazole susceptibility of Italian Candida dubliniensis clinical isolates determined by reference and simplified tests.

Candida dubliniensis ia an opportunistic pathogen mainly associated with oral candidiasis in human immunodeficiency virus (HIV)-infected individuals. We recently recovered the first Italian clinical isolates of C. dubliniensis from the oral cavities of seven HIV-seropositive subjects. The in vitro susceptibility to fluconazole (FLCZ) of these isolates was determined according to the National Committee for Clinical Laboratory Standards (NCCLS) M27-A broth microdilution method for yeasts. All seven isolates of C. dubliniensis were susceptible to FLCZ (MICs < or =0.5 microg/ml). Results of this reference method were compared to those obtained with simplified tests, more adapted to routine evaluation in hospital laboratories. Fungitest and Sensititre YeastOne colorimetric microplate-based methods have been evaluated. The agar disk diffusion method has also been tested on two different media: RPMI 1640-2% glucose and High Resolution-2% glucose-0.5 microg/ml methylene blue. All of the simplified methods tested were able to correctly identify FLCZ-susceptibility of this group of Italian C. dubliniensis isolates.

Effect of antimicrobial mouthrinses on the in vitro adhesion of Candida albicans to human buccal epithelial cells.

Adhesion to epithelial cells is a critical step in successful oral colonization and infection by Candida albicans. Therefore, three mouthrinse products, containing chlorhexidine 0.2% (CHX), cetylpyridinium chloride 0.05% (CPC) or triclosan 0.045% (TRN), were compared for their effects on the in vitro adhesion of C. albicans to human buccal epithelial cells (BEC). Candidal adhesion appeared to be significantly reduced by oral rinsing with the CHX-containing mouthrinse (P<0.0001). In vivo exposure of BEC to the CPC mouthrinse also inhibited adhesion of C. albicans (P<0.0001). Both CHX and CPC products suppressed adhesion to the same extent (P>0.01). On the other hand, the TRN mouthrinse did not significantly affect epithelial adhesion of C. albicans (P>0.01). These findings suggest that mouthrinses containing CHX or CPC could be of value in the control of candidal colonization and infection. Clinical trials are warranted on the effectiveness of these products in reducing oral Candida carriage.

Effect of dietary carbohydrates on the in vitro epithelial adhesion of Candida albicans, Candida tropicalis, and Candida krusei.

Adhesion to epithelial surfaces is considered as a critical step in the pathogenesis of oral candidosis. Therefore, the effects of the most commonly consumed dietary carbohydrates on the adhesion of Candida albicans, Candida tropicalis, and Candida krusei to monolayered HeLa cells were investigated. Adherence of C. albicans and C. tropicalis appeared significantly promoted by incubation in defined medium containing a high concentration (500 mM) of fructose, glucose, maltose, and sucrose (p < 0.001). C. albicans organisms grown in sucrose elicited maximal increase in adhesion, whereas adhesion of C. tropicalis and C. krusei was enhanced to the greatest extent when cultured in glucose. Maltose and fructose also promoted adherence of C. albicans and C. tropicalis (p < 0.001), but to a lesser extent than sucrose and glucose. On the other hand, sorbitol-grown yeasts demonstrated a marginal increase in adhesion (p > 0.01). Xylitol only significantly reduced adherence of C. albicans (p < 0.001). These results suggest that the frequent consumption of carbohydrates, such as sucrose, glucose, maltose, or fructose, might represent a risk factor for oral candidosis. The limitation of their consumption by substituting xylitol or sorbitol could be of value in the control of oral Candida colonization and infection.

In vitro activities of antimicrobial agents against Candida species.

OBJECTIVE: Antimicrobial mouthrinses may represent a valid alternative to topical antifungal agents. However, the action of antimicrobials could be affected by the different ingredients incorporated into mouthrinse products. The purpose of the present study was to investigate the in vitro antifungal and fungicidal activities of antimicrobials alone. STUDY DESIGN: A broth macrodilution method was used to determine the minimum inhibitory concentration of 4 antimicrobial agents against Candida species. Minimum fungicidal concentration was also determined. RESULTS: All antimicrobials showed antifungal activity against all tested organisms, but cetylpyridinium chloride received significantly lower minimum inhibitory concentrations (P < .005). Cetylpyridinium chloride also showed a greater fungicidal activity than chlorhexidine digluconate and hexetidine (P< .005), whereas sanguinarine chloride appeared to be less fungicidal against most of the isolates tested. CONCLUSIONS: These findings suggest that cetylpyridinium chloride may be used as a topical antifungal agent. Clinical trials are now required to assess its value in the management of oral candidosis.

In vitro antifungal properties of mouthrinses containing antimicrobial agents.

The purpose of this study was to investigate the in vitro antifungal properties of seven commercial mouthrinses containing antimicrobial agents. These included cetylpyridinium chloride (CPC), chlorhexidine digluconate (CHX), hexetidine (HEX), sanguinarine (SNG), and triclosan (TRN). The minimum fungicidal concentration (MFC) against six species of yeasts was determined by a broth macrodilution method. The kill-time of mouthrinses at half the concentration of the commercial formulations was also determined. MFCs were achieved with each mouthrinse, except the SNG-containing mouthrinse, against all the organisms being tested. However, the CPC-containing mouthrinse appeared more active than the other products (P < 0.001). There were no significant differences in MFC values among CHX mouthrinse products, once adjusted for initial concentration differences (P = 0.1). Kill-times of mouthrinses containing either CHX or CPC were less than or equal to 180 seconds with all the species of yeasts, and no significant differences were found among these products (P = 0.18). On the other hand, mouthrinses containing either TRN or HEX did not show a lethal effect on Candida albicans, Candida parapsilosis, or Candida guilliermondii. No kill-times were achieved with the SNG-containing mouthrinse. These results suggest that mouthrinses containing antimicrobial agents might represent an appropriate alternative to conventional antifungal drugs in the management of oral candidiasis. However, the effectiveness of antimicrobial mouthrinses as antifungal agents needs to be evaluated in further clinical trials.