Fluconazole susceptibilities of Candida species and distribution of species recovered from blood cultures over a 5-year period

Fluconazole. An update of its pharmacodynamic and pharmacokinetic properties and therapeutic use in major superficial and systemic mycoses in immunocompromised patients

Fluconazole is a triazole antifungal agent which is now an established part of therapy in patients with immune deficiencies. It is effective against oropharyngeal/oesophageal candidiasis (candidosis) when used orally once daily either as treatment or secondary prophylaxis in patients with AIDS or as treatment or primary prophylaxis in neutropenia associated with cancer therapy. Fluconazole also resolves symptoms in up to 60% of patients with cryptococcal meningitis and AIDS. However, in this infection its efficacy as treatment relative to that of amphotericin B is equivocal, and its major role is as the drug of choice for maintenance therapy following amphotericin B induction. In this regard, fluconazole has been proven superior to amphotericin B and to itraconazole 200 mg/day. Comparisons with other drugs used for the treatment of mucosal candidiasis in patients with AIDS show fluconazole to be superior to nystatin, similar to itraconazole and at least as effective as clotrimazole and ketoconazole; it was more so than the latter azole in 1 study. In patients undergoing chemotherapy or bone marrow transplantation, fluconazole as primary prophylaxis has produced greater clinical benefit than a clotrimazole regimen. The incidence of adverse events appears to be somewhat higher in patients with AIDS compared with HIV-negative cohorts, but the qualitative pattern of events is similar. The most frequent events are gastrointestinal complaints, headache and skin rash: rare exfoliative skin reactions and isolated instances of clinically overt hepatic dysfunction have occurred in patients with AIDS. Issues yet to be clarified include: the use of fluconazole in children with AIDS, in whom results have been promising; its efficacy against other fungal infections encountered in immunocompromised patients; whether the drug influences mortality, as has been suggested by one placebo-controlled trial in patients undergoing bone marrow transplant; and the appropriateness of its potential for use as primary prophylaxis against cryptococcal meningitis in patients with AIDS, where it shows efficacy but there is concern over increasing risk of development of secondary resistance. Notwithstanding these undefined aspects of its clinical profile, fluconazole is now confirmed as an important antifungal drug in the management of fungal infections in patients with immune deficiencies. In patients with AIDS it is the present drug of choice as maintenance therapy against cryptococcal meningitis and is a preferred agent for secondary prophylaxis against candidal infections; it is also a favoured agent for primary prophylaxis in patients at risk because of neutropenia associated with chemotherapy or bone marrow transplantation .

Torulopsis glabrata: azole susceptibilities by microdilution colorimetric and macrodilution broth assays

Fluconazole and itraconazole MICs were determined by both the standard macrodilution method of the National Committee for Clinical Laboratory Standards and a colorimetric broth microdilution method for 140 isolates of Torulopsis (Candida) glabrata obtained over a 15-year period. Using the method of the National Committee for Clinical Laboratory Standards the MICs at which 90% of isolates are inhibited (MIC50) for all isolates were 32 and 1.6 micrograms/ml for fluconazole and itraconazole, respectively. For fluconazole, the MIC90 rose from 16 to > 64 micrograms/ml when the MIC90s for isolates collected from July 1980 to June 1991 were compared with those for isolates collected from July 1991 to March 1995. For itraconazole, the MIC90s for isolates from the same time periods were 0.8 and 3.2 micrograms/ml, respectively. Although for isolates from some non-human immunodeficiency virus-infected patients the MICs rose, most of the high MICs were found for isolates from human immunodeficiency virus-infected patients who had been extensively treated with azole drugs for thrush. The colorimetric method yielded endpoints that were more definitive; concordances within 2 dilutions for the two methods were 87% for fluconazole and 86% for itraconazole.

New and emerging yeast pathogens

The most common yeast species that act as agents of human disease are Candida albicans, Candida tropicalis, Candida glabrata, Candida parapsilosis, and Cryptococcus neoformans. The incidence of infections by other yeasts has increased during the past decade. The most evident emerging pathogens are Malassezia furfur, Trichosporon beigelii, Rhodotorula species, Hansenula anomala, Candida lusitaniae, and Candida krusei. Organisms once considered environmental contaminants or only industrially important, such as Candida utilis and Candida lipolytica, have now been implicated as agents of fungemia, onychomycosis, and systemic disease. The unusual yeasts primarily infect immunocompromised patients, newborns, and the elderly. The role of central venous catheter removal and antifungal therapy in patient management is controversial. The antibiograms of the unusual yeasts range from resistant to the most recent azoles and amphotericin B to highly susceptible to all antifungal agents. Current routine methods for yeast identification may be insufficient to identify the unusual yeasts within 2 days after isolation. The recognition of unusual yeasts as agents of sometimes life-threatening infection and their unpredictable antifungal susceptibilities increase the burden on the clinical mycology laboratory to pursue complete species identification and MIC determinations. Given the current and evolving medical practices for management of seriously ill patients, further evaluations of the clinically important data about these yeasts are needed.

Antifungal susceptibility testing of yeasts: evaluation of technical variables for test automation

The technical parameters for antifungal susceptibility testing with Candida species were reexamined to determine the optimal conditions for testing with semiautomated preparations of broth microdilution cultures, automated spectrophotometric readings of the cultures, and dose-response and endpoint determinations by means of a computer spreadsheet. Tests were based on proposed standard method M27P of the National Committee for Clinical Laboratory Standards for antifungal agents. RPMI 1640 broth with extra glucose to a final concentration of 2% gave higher and more reproducible drug-free control readings without affecting susceptibility endpoint readings. An inoculum of 8 x 10(4) yeasts per ml prepared from a carbon-limiting broth culture without further standardization was found to give optimal control readings after 48 h of incubation at 37 degrees C. For flucytosine, fluconazole, itraconazole, and ketoconazole, endpoints based on 50% growth inhibition (50% inhibitory concentration) gave the minimum variation with inoculum size and the fewest endpoint differences with RPMI 1640 medium obtained from two different suppliers. The 50% inhibitory concentration was also the optimal endpoint for fluconazole and ketoconazole susceptibilities in comparison with broth macrodilution MICs determined by the method of the National Committee for Clinical Laboratory Standards. Intralaboratory reproducibility was determined by retrospective analysis of replicate results for isolates retested at random over a 2-year period. This approach showed less favorable reproducibility than has been reported from purpose-designed, prospective antifungal susceptibility studies, but it may better reflect real-life test reproducibility. Susceptibility data for 616 clinical isolates of yeasts, representing 16 Candida and Saccharomyces spp., confirmed the tendency of Candida lusitaniae isolates to show relatively low susceptibilities to amphotericin B, the tendency of Candida krusei isolates to show low flucytosine and fluconazole susceptibilities, and the presence of some isolates in the species Candida albicans, Candida glabrata, and Candida tropicalis with low susceptibilities to azole derivative antifungal agents. The study demonstrates the value of automation and standardization in all stages of yeast susceptibility testing, from plate preparation to data analysis.

Epidemiology of candidiasis

The increase in infections due to Candida over the past decade is significant. This is particularly true for hospitalized patients where the rate of blood-stream infection due to Candida spp. has increased by almost 500% over the decade of the 1980s. This increase is accompanied by a significant excess mortality and a prolonged length of stay in the hospital. This trend continues into the 1990s where in the US Candida spp. remains the fourth most common blood-stream pathogen, accounting for 8% of all hospital-acquired blood-stream infections. Notably, more than one-third of candidal blood-stream infections are caused by species other than C. albicans. The majority of these infections arise from an endogenous focus of colonization; however, the documentation of nosocomial transmission or 'cross-infection' and the recognition of resistance to antifungal agents pose new and significant problems. Recent studies indicate that Candida may be isolated from the hands of 15-54% of health care workers in the intensive care unit setting and that the strain of Candida carried on the hands may be shared by infected patients. These studies are facilitated by molecular typing and careful epidemiological investigation and suggest that cross-infection is an important and preventable feature of candidal blood-stream infection. Both endogenous and exogenous sources of infection are now well-documented and such information should help direct measures to prevent infections in high risk individuals.

Fluconazole. An update of its antimicrobial activity, pharmacokinetic properties, and therapeutic use in vaginal candidiasis

Fluconazole is a bis-triazole antifungal drug which has a pharmacokinetic profile characterised by its high water solubility, low affinity for plasma proteins, and metabolic stability. After a single 150 mg oral dose, therapeutic concentrations in vaginal secretions are rapidly achieved and are sustained for a duration sufficient to produce high clinical and mycological responses in nonimmunocompromised patients with vaginal candidiasis (candidosis). At this dosage, clinical and mycological responses have compared favourably with responses achieved after multiple dose regimens of other oral and intravaginal antifungal agents. Clinical efficacy rates have ranged between 92 and 99% at short term evaluation (5 days post-treatment). At 80 to 100 days post-treatment clinical efficacy rates of 91% have been reported. In addition, limited data indicate that fluconazole is more effective than placebo as prophylactic treatment of frequently recurring vaginal candidiasis. Single oral doses of fluconazole 150 mg are well tolerated. Most frequently observed adverse events are gastrointestinal symptoms, which are generally mild and transient in nature. Thus, fluconazole is a valuable alternative to established systemic and intravaginal azole antifungal drugs which are used to treat vaginal candidiasis. Moreover, in view of its favourable patient acceptability and compliance profile compared with alternative treatments, single-dose oral fluconazole should be considered as a first-line therapeutic choice for the treatment of women with vaginal candidiasis.

Comparison of visual and spectrophotometric methods of MIC endpoint determinations by using broth microdilution methods to test five antifungal agents, including the new triazole D0870

A study to compare three different methods for reading MIC endpoints tested by the broth microdilution modification of the National Committee for Clinical Laboratory Standards (Villanova, Pa.) reference method was conducted. MICs of amphotericin B, flucytosine, fluconazole, itraconazole, and a new triazole, D0870, were determined for five reference yeast strains and 100 clinical isolates of Candida spp. MICs were read visually according to National Committee for Clinical Laboratory Standards guidelines from microdilution trays that had been (VS) and had not been (V) shaken. MICs were also determined spectrophotometrically (SP) at 492 nm. SP endpoints were determined as the concentrations resulting in a > or = 50% inhibition of growth (flucytosine and azoles) and a > or = 90% inhibition of growth (amphotericin B) relative to control growth. The five reference strains were tested nine times each against all five antifungal agents, and the MIC results for each reading method were compared with a 3-log2 dilution reference range determined by the macrodilution (M27-P) method. Overall, 84 to 100% of the MICs determined by V, 93 to 100% of those determined by VS, and 89 to 100% of those determined by SP fell within the 3-log2 dilution reference range for each reference strain and antifungal agent. Reproducibility was 99% for V and SP and 98% for VS. Agreement among the three methods of reading ranged from 97 to 99%. Excellent agreement among reading methods was also observed for all antifungal agents when tested against 100 clinical isolates. Agreement between the standard V method (no agitation) and VS ranged from 99 to 100%, and that between V and SP ranged from 89 to 99%. The VS and SP reading methods provided more definitive endpoints than the V method, which does not involve shaking.

Fungemia: An increasing problem in a Danish university hospital 1989 to 1994

OBJECTIVE: To present data on episodes of fungemia in a Danish tertiary-care university hospital admitting all types of patients and to compare the data with previous findings from the same hospital. METHODS: Retrospective identification of episodes of fungemia from 1989 to 1994 and collection of data from computerized files at the Clinical Microbiology Department at Rigshospitalet and the Mycology Reference Laboratory at Statens Seruminstitut. RESULTS: The incidence of fungemia increased gradually from 19 episodes in 1989 to 57 episodes in 1994. An earlier report from the same hospital showed 20 to 25 episodes of fungemia per year between 1984 and 1988. Candida albicans was the dominating species during both periods, accounting for 73% of isolates during 1984 to 1988 and 67% during 1989 to 1994. However, in the hematology department where fluconazole has been used extensively, C. albicans constituted 47% of isolates with Candida krusei and Candida glabrata comprising 25%. CONCLUSIONS: The incidence of fungemia in our tertiary-care hospital has increased threefold from 1989 to 1994. Candida albicans was the dominating cause of fungemia but, in the hematology department, this yeast accounted for less than half of the isolates during the same time period.