Isolation of a human serum protein that inhibits the growth of Cryptococcus neoformans

Determination of voriconazole serum concentration by bioassay, a valid method for therapeutic drug monitoring for clinical laboratories

We describe here a simple, fast, and reliable bioassay method for therapeutic drug monitoring of voriconazole. Fifty-eight clinical and external quality control samples were evaluated with this microbiological assay, and results were compared with those obtained with a previously validated chromatographic method. A good correlation between both assays was observed. This particular microbiological method was demonstrated to be simple and offers enough precision and accuracy to perform voriconazole therapeutic drug monitoring in laboratories without specialized equipment.

HPLC/UV or bioassay: two valid methods for posaconazole quantification in human serum samples

In this paper we report on the development and validation of two different methods for posaconazole quantification from serum samples, HPLC/UV and bioassay. Both methods have been validated according to international guidelines and were also applied to the analysis of 61 trough serum samples from treated patients. A good correlation between both methods was observed. The HPLC method, more laborious and expensive, was demonstrated to be more accurate, precise and faster (analytical range 0.125-16 μg/mL, accuracy between -2.48 and 3.70% and precision between 2.77 and 5.93%, with an analytical run time of 11 min), making it a valuable tool for reference laboratories that centralize high numbers of samples. The microbiological method, however, is simple and offers sufficient precision and accuracy (analytical range 0.125-16 μg/mL, accuracy between -8.10 and 3.77% and a precision between 4.52 and 10.07%), to be used to monitor posaconazole. It may be a valid alternative to chromatographic methods in clinical laboratories without specialized facilities.

Extracellular enzymatic activity and serotype of Cryptococcus neoformans strains isolated from AIDS patients in Brazil

One hundred and fifty-one Cryptococcus neoformans strains isolated from AIDS patients in Brazil and maintained in the Adolfo Lutz Institute (São Paulo, Brazil) were tested for phospholipase, protease and other extracellular enzymatic activities and their serotypes determined. Production of extracellular phospholipase and protease was tested by the agar plate methods. Determination of extracellular enzyme profile of the strains was performed by using the API-ZYM kit system, which can test 19 different enzymes. The serotypes were determined by cell agglutination using the Crypto-check method. Among the 151 strains, 147 were identified as serotype A and four strains were serotype AD. Production of extracellular phospholipase and protease was extensive and observable at early stages of incubation. All of the tested strains were positive for the production of both enzymes. In the API-ZYM tests, more than 90 % of the 151 tested strains were positive for esterase C4 (No. 3), esterase lipase C8 (No. 4), leucine arylamidase (No. 6), phosphatase acid (No. 11), naphtol-AS-BI-phosphohydrolase (No. 12), alpha-glucosidase (No. 16) and beta-glucosidase (No. 17). Differences in enzymatic activities between the Brazilian strains and strains isolated in other countries were observed. The phospholipase, protease and other enzyme activities may play a role in host tissue invasion by C. neoformans.

Pathogenicity and virulence of Candida dubliniensis: comparison with C. albicans

Candida dubliniensis is a newly described fungus that is frequently isolated from the oral cavities of HIV-positive patients. Although extensive studies have been performed on the phylogeny of C. dubliniensis, little is known about the pathogenic ecology of this yeast. Here we examined aspects related to C. dubliniensis in comparison with those of C. albicans. When injected intravenously into mice, C. dubliniensis had a higher survival rate than C. albicans. Histopathological analysis disclosed that C. dubliniensis remained mostly in the yeast form in the infected organs, whereas C. albicans changed into the mycelial form. The host inflammatory reaction was aggressive with C. dubliniensis infection and mild with C. albicans infection. Co-culture of the yeasts with human polymorphonuclear leukocytes disclosed that C. dubliniensis is more vulnerable to the fungicidal activity of leukocytes than C. albicans. C. dubliniensis was also more susceptible to the toxic effect of hydrogen peroxide. When cultured in vitro, C. dubliniensis grew more slowly than C. albicans, but the formation of germ tubes was faster. When the fungi were cultured in RPMI 1640, a fetal bovine serum supplement suppressed the growth of C. dubliniensis but enhanced that of C. albicans. These results clearly indicated that C. dubliniensis is less virulence than C. albicans.

Transferrin independent serum inhibition of Blastomyces dermatitidis

Human serum has been reported to inhibit the growth of several fungal pathogens. Serum inhibitory activity has predominantly been associated with transferrin-mediated iron binding. We found that serum from several animal species (human, dog, mouse and fetal bovine) inhibited the growth of the dimorphic fungal pathogen, Blastomyces dermatitidisin vitro. In initial studies, we found no correlation between the total iron-binding capacity of various sera and their inhibitory activity against B. dermatitidis yeast. In addition, we were unable to abrogate the inhibitory activity of human serum against B. dermatitidis yeast by the addition of ferric chloride (10-200 microM). We found that apo-transferrin had little or no inhibitory activity against B. dermatitidis yeast. Furthermore, serum from hypotransferrinemic mice (hpx/hpx) had inhibitory activity against B. dermatitidis yeast that was equivalent to that of normal mouse serum. These findings are consistent with our initial findings and suggest that serum inhibitory activity against B. dermatitidis yeast is transferrin independent. Although high concentrations (3.5-5 mg/ml) of lactoferrin did have inhibitory activity against B. dermatitidis yeast, these concentrations were orders of magnitude greater than those found in serum under normal physiological conditions, suggesting that lactoferrin was not likely to contribute to serum inhibitory activity against B. dermatitidis yeast. Our findings suggest that host iron-binding proteins may be relatively ineffective in innate host defense against infection with B. dermatitidis yeast.

Characterization of an anticryptococcal protein isolated from human serum

Human serum at low concentrations inhibits the growth of Cryptococcus neoformans in vitro. Fractionation of serum yielded a purified inhibitory protein with a molecular mass of approximately 81.8 kDa, a pI of approximately 6.2, and an amino acid sequence that matched that of human transferrin. The inhibitory activity and that of apotransferrin and 5% human serum were reversed by 10 microM freshly prepared FeCl(3).