Treatment of disseminated candidiasis with 5-fluorocytosine

Hybrid Molecules Development: A Versatile Landscape for the Control of Antifungal Drug Resistance: A Review

Hybrid molecule approach of drug design has become popular due to advantages such as delayed resistance, reduced toxicity, ease of treatment of co-infection and lower cost of preclinical evaluation. Antifungal drugs currently available for the treatment of fungal diseases suffer a major side effect of drug resistance. Hybrid drugs development is one of the approaches that has been employed to control microbial resistance. Their antifungal activity is influenced by their design. This review is focused on hybrid molecules exhibiting antifungal properties to guide scientists in search of more efficient drugs for the treatment of fungal diseases.

5-fluorocytosine-related bone-marrow depression and conversion to fluorouracil: a pilot study

The aim of this study is to investigate whether fluorouracil (5-FU) could be responsible for bone-marrow depression occurring in fluorocytosine (5-FC) treated patients. Six 5-FC treated patients were included in this pilot study. Toxicity was monitored by means of thrombocyte and leucocyte counts. 5-FC and 5-FU serum levels were measured using a high-performance liquid chromatography (HPLC) assay that allows simultaneous determination of both compounds. The amounts of 5-FU in the 34 available serum samples remained below the limit of quantitation (< 0.05 mg/L), whereas 5-FC levels could be detected in all samples. Instead, low levels of the 5-FU catabolite alpha-fluoro-beta-alanine (FBAL) were detected in several of the investigated serum samples. In case of three patients thrombocyte counts remained within the normal range during 5-FC treatment, whereas one patient developed thrombocytopenia (50 x 10(9) thrombocytes/L) during therapy. Furthermore, one patient developed leucocytopenia (2.6 x 10(9) leucocytes/L) during 5-FC therapy, whereas the remaining five patients were suffering from leucocytosis prior to 5-FC therapy. In conclusion, we found nondetectable 5-FU serum concentrations (< 0.05 mg/L) in ICU patients treated with intravenous 5-FC, making it unlikely that 5-FC-associated toxicity results from 5-FU exposure in patients receiving intravenous 5-FC therapy. These findings may be explained by the fact that our patients received 5-FC intravenously instead of orally, therefore not allowing active conversion of 5-FC to 5-FU by the human intestinal microflora.

Population pharmacokinetics of flucytosine: comparison and validation of three models using STS, NPEM, and NONMEM

The objective of this study is to compare and validate three models of flucytosine (5-FC) population pharmacokinetics using three methods of analysis to elucidate which model describes 5-FC pharmacokinetics most accurately and which method is the most suitable for this purpose. Retrospectively, demographic and clinical data of two similar sets of a total of 88 intensive care unit (ICU) patients were gathered for calculation and validation of 5-FC pharmacokinetics respectively. Three pharmacokinetic models were analyzed: a one-compartment with renal elimination (renal model), a one-compartment with renal and metabolic elimination (mixed model), and a two-compartment with renal elimination (two-compartment model). Population pharmacokinetic parameters were calculated using the standard two-stage method (STS), NONMEM, and NPEM. Furthermore, a covariate model was built by NONMEM. Validation of the 10 calculated pharmacokinetic models showed that NONMEM is most suitable for predicting 5-FC population pharmacokinetics. Based upon AIC values, bias and precision, the best results are obtained using a two-compartment model with renal elimination (k(elr) = 0.000858 +/- 0.000143 l/h per mL per min, k12 = 0.0313 +/- 0.0168 h(-1), k21 = 0.0353 +/- 0.0145 h(-1), and Vd = 0.541 +/- 0.084 L/kg; bias = -13.16; 95% CI = -16.77; -9.55; precision = 30.50; 95% CI = 27.47; 33.26) or a two-compartment covariate model as built by NONMEM [Vd (L) = 0.572 x WT, Cl(5FC) (L/h) = 1.69 + 0.0273 x (Cl(cr) (mL/min) - 52.5), k12 = 0.0235 +/- 0.0107 h(-1), and k21 = 0.0375 +/- 0.0147 h(-1); bias = -8.29; 95% CI = -11.63; -4.95; precision = 26.77; 95% CI = 24.24; 29.07]. In conclusion, this study shows that a two-compartment model with renal elimination best describes 5-FC population pharmacokinetics and NONMEM is able to build a two-compartment covariate model that predicts 5-FC levels equally well in our population of ICU patients. Furthermore, NONMEM appeared to be the most suitable method of population pharmacokinetics in our population and for this purpose it offers more reliable and accurate results than NPEM or the STS method.

Isolation of fungi in blood cultures. A review of fungal infections in the western part of Sweden 1970-1982

Relevant data were analysed from 185 patients treated for various diseases in the Göteborg area, Sweden, between 1970 and 1982 and in whom fungi were isolated in blood cultures. The increase in isolations during the first part of the study seemed to coincide with extended use of central venous catheters. However, with greater awareness of factors contributing to yeast colonization, the annual incidence fell during the latter part of the period. A disseminated fungal infection was found in 45% of cases, with a mortality of 58%. 4/42 patients with transient fungemia died; 3 from concomitant bacterial septicemia. The mortality rate was 30% in patients with antimycotic treatment because of disseminated infection. Candida albicans, followed by C. glabrata, were the most commonly isolated strains (70% and 13%, respectively). C. albicans predominated in patients with fungal endophthalmitis (100%) and in neonatal infections (95%).

Disseminated candidiasis: a comparison of two immunologic techniques in the diagnosis

Eighty-five subjects were tested for the presence of circulating candidal antigen (CAg) and anti-candidal antibody (CAb) using both an enzyme immunoassay (ELISA) and counterimmunoelectrophoresis (CIE). The 72 studied controls included laboratory volunteers; hospitalized patients without evidence of infection; febrile hospitalized patients without evidence of candidiasis; and patients with superficial candidiasis and candiduria. The control subjects were compared with 13 patients with proven disseminated candidal infection (disease prevalence = 15%). The ELISA CAb test was of greater individual sensitivity (92%) in separating patients with systemic candidiasis from all controls combined than the ELISA CAg, CIE CAg, or CIE CAb test (61%, 15%, 69%, respectively). The CIE CAg test, though specific (100%), was insensitive. Sensitivity, specificity, and predictive values were generally enhanced by employing combinations of tests. Sera from patients with disseminated candidiasis were much more likely to yield a positive result by two or more serologic tests than were control sera (p = less than 0.0004). The sensitivity of combinations ranged from 15% to 92%. The specificity of combinations ranged from 21% to 100%. The predictive value positive of combinations test ranged from 40% to 100%. Predictive value negative of combinations ranged from 69% to 98%. Patients with a variety of superficial and deep candidal infections apparently have detectable circulating CAb and/or CAg. The ELISA CAb test was superior to the other tests in identifying patients with disseminated candidiasis. Combinations of serologic tests may be superior to individual tests in the diagnosis or exclusion of serious disease due to Candida albicans.

Pathogenicity in mice of strains of Candida albicans with different in vitro sensitivity to 5-fluorocytosine

The pathogenicity in mice of 7 strains of Candida albicans with different in vitro susceptibility to 5-fluorocytosine (5-FC) was investigated. Resistant strains were not less virulent than susceptible strains. This is contradictory to findings reported for candida strains resistant to polyene antibiotics, which were less pathogenic than susceptible strains. The implications of these findings are discussed.

Genitourinary fungal infections

Although fungal urinary tract infections occur less frequently than bacterial urinary tract infections their incidence has increased during the last several decades and their clinical importance to the urologist should not be underestimated. Herein the pertinent literature on fungal urinary tract infections is reviewed, with emphasis on the predisposing factors, pathogenesis, host defense mechanisms and the clinical spectrum of the disease. An approach to the evaluation of positive cultures and therapy is presented.

Rapid, simple bioassay for 5-fluorocytosine in the presence of amphotericin B

It is important that serum levels of 5-fluorocytosine (5FC) be measured to insure therapeutic levels while avoiding toxicity. This is particularly true in patients with renal insufficiency. The concurrent use of amphotericin B and 5FC complicates the measurement of 5FC in the serum, since fungi used in conventional bioassay systems are uniformly susceptible to amphotericin B. This paper describes the development of a simple, reliable, 6-h bioassay for 5FC in the presence of amphotericin B. The assay is based upon the fact that 5FC diffuses readily through yeast nitrogen base agar, whereas amphotericin B apparently does not. This assay allows rapid adjustments in therapy of patients receiving both 5FC and amphotericin B and has permitted us to maintain 5FC serum levels between limits of 25 and 120 mug/ml in patients with altered renal function.