Fungal infections of the immunocompromised host: clinical and laboratory aspects

Evolutionary trends in antifungal resistance: a meta-analysis

The present paper includes a meta-analysis of literature data on 318 species of fungi belonging to 34 orders in their response to 8 antifungal agents (amphotericin B, caspofungin, fluconazole, itraconazole, ketoconazole, posaconazole, terbinafine, and voriconazole). Main trends of MIC results at the ordinal level were visualized. European Committee on Antimicrobial Susceptibility Testing and Clinical & Laboratory Standards Institute (CLSI) clinical breakpoints were used as the staff gauge to evaluate MIC values ranging from resistance to susceptibility, which were subsequently compared with a phylogenetic tree of the fungal kingdom. Several orders (Hypocreales, Microascales, and Mucorales) invariably showed resistance. Also the basidiomycetous orders Agaricales, Polyporales, Sporidiales, Tremellales, and Trichosporonales showed relatively high degrees of azole multi-resistance, while elsewhere in the fungal kingdom, including orders with numerous pathogenic and opportunistic species, that is, Onygenales, Chaetothyiales, Sordariales, and Malasseziales, in general were susceptible to azoles. In most cases, resistance vs susceptibility was consistently associated with phylogenetic distance, members of the same order showing similar behavior.

IMPORTANCE

A kingdom-wide the largest set of published wild-type antifungal data comparison were analyzed. Trends in resistance in taxonomic groups (monophyletic clades) can be compared with the phylogeny of the fungal kingdom, eventual relationships between fungus-drug interaction and evolution can be described.

Surge of mucormycosis during the COVID-19 pandemic

Patients with respiratory viral infections are more likely to develop co-infections leading to increased fatality. Mucormycosis is an epidemic amidst the COVID-19 pandemic that conveys a 'double threat' to the global health fraternity. Mucormycosis is caused by the Mucorales group of fungi and exhibits acute angioinvasion generally in immunocompromised patients. The most familiar foci of infections are sinuses (39%), lungs (24%), and skin tissues (19%) where the overall dissemination occurs in 23% of cases. The mortality rate in the case of disseminated mucormycosis is found to be 96%. Symptoms are mostly nonspecific and often resemble other common bacterial or fungal infections. Currently, COVID-19-associated mucormycosis (CAM) is being reported from a number of countries such as the USA, Turkey, France, Mexico, Iran, Austria, UK, Brazil, and Italy, while India is the hotspot for this deadly co-infection, accounting for approximately 28,252 cases up to June 8, 2021. It strikes patients within 12-18 days after COVID-19 recovery, and nearly 80% require surgery. Nevertheless, the mortality rate can reach 94% if the diagnosis is delayed or remains untreated. Sometimes COVID-19 is the sole predisposing factor for CAM. Therefore, this study may provide a comprehensive resource for clinicians and researchers dealing with fungal infections, intending to link the potential translational knowledge and prospective therapeutic challenges to counter this opportunistic pathogen.

Invasive Fungal Infection Complicating Treatment With Ibrutinib

Ibrutinib is a selective Bruton's tyrosine kinase inhibitor (BTKi) approved for the treatment of chronic lymphocytic leukemia (CLL) and other B-cell malignancies. Invasive fungal infections (IFIs) have recently been reported in patients on BTKis despite the absence of significant immunocompromise raising great interest among oncologists regarding the mechanism by which BTKi's permit fungal infections. Here, we describe a fatal case of cerebral aspergillosis in a patient with relapsed CLL while on treatment with ibrutinib. There are few hypotheses on the mechanism by which ibrutinib permits fungal infections. As it becomes more widely used in B-cell cancers, clinicians should be aware of the potential for decreased anti-fungal immunity with this drug.

Fungal pneumonia in kidney transplant recipients

Fungal pneumonia is a dreaded complication encountered after kidney transplantation, complicated by increased mortality and often associated with graft failure. Diagnosis can be challenging because the clinical presentation is non-specific and diagnostic tools have limited sensitivity and specificity in kidney transplant recipients and must be interpreted in the context of the clinical setting. Management is difficult due to the increased risk of dissemination and severity, multiple comorbidities, drug interactions and reduced immunosuppression which should be applied as an important adjunct to therapy. This review will focus on the main causes of fungal pneumonia in kidney transplant recipients including Pneumocystis, Aspergillus, Cryptococcus, mucormycetes and Histoplasma. Epidemiology, clinical presentation, laboratory and radiographic features, specific characteristics will be discussed with an update on diagnostic procedures and treatment.

Fungal infections in children with haematologic malignancies and stem cell transplant recipients

Children with haematologic malignancies and haematopoietic stem cell transplant recipients are at high risk for invasive fungal diseases (IFD). There has been an increased number of at-risk children over the past two decades due to improvements in cancer therapies resulting in improved survival of children with high-risk and refractory malignancies. The predominant organisms that cause IFD include Candida spp., Aspergillus spp. and the Mucorales molds. Clinical presentations of IFD vary based on host immune status and the causative organism. Though serum biomarkers such as the galactomannan assay and beta-D-glucan assay have been validated in adults, there are limited data regarding their diagnostic value in children. Thus, the gold standard for IFD diagnosis remains tissue biopsy with histopathological and microbiological evaluation. Treatment of IFD is multimodal and involves antifungal drugs, correction of immune dysfunction and surgical resection when feasible. Paediatric practice regarding IFD is largely extrapolated from data generated in adult patients; in this review, we evaluate both primary paediatric studies and guidelines intended for adult patients that are applied to paediatric patients. There remain significant knowledge gaps with respect to the prevention, diagnosis and treatment of IFD in immunocompromised children, and further research is needed to help guide management decisions.

Pediatric Mucormycosis: A 10-Year Systematic Review of Reported Cases and Review of the Literature

Mucormycosis is a severe infection that affects a variety of patients, including immunocompromised children and neonates. Given improved survival rates from advances in the treatment of malignancies, the population at risk for mucormycosis is increasing. We conducted a systematic review of cases of mucormycosis in children in the English-language literature reported between August 2008 and June 2017 and analyzed the clinical characteristics, diagnosis, management, and outcome of those infections. The most common underlying diagnoses included neutropenia (41%), hematologic malignancy (39%), prematurity (13%), and hematopoietic stem cell transplant (11%). Sinus disease (28%) and disseminated disease (24%) were the most common presentations. Rhizopus spp were the most common organisms isolated (22%). Amphotericin B remains the backbone of treatment and was prescribed in 86% of these cases. The resulting mortality rate remains high (32%). We provide here the results of a literature review of mucormycosis in children, including its epidemiology and clinical manifestations, and describe current advances in its diagnosis and treatment.

Histoplasmosis and multicentric lymphoma in a Nubian goat

Following treatment for pneumonia, a 1-y-old female Nubian goat was presented because of a persistent fever for 3 mo and peripheral lymphadenopathy for 1 mo. Cytology and histology of the superficial cervical and prefemoral lymph nodes demonstrated a moderate-to-marked "left-shifted" lymphoid population, suggestive of lymphoma, and extremely rare extracellular, 2-4 µm, oval, basophilic yeast, consistent with Histoplasma capsulatum. On immunohistochemistry, >95% of the lymphocytes demonstrated positive cytoplasmic and membranous immunoreactivity for CD3. Histoplasma spp. urine antigen and serum antibody testing were positive and negative, respectively. Panfungal PCR and sequencing of DNA extracted from scrolls of formalin-fixed, paraffin-embedded tissue yielded matches to H. capsulatum with 99-100% identity. Given the poor prognosis and persistent pyrexia, the animal was euthanized. Postmortem examination confirmed concurrent multicentric, intermediate-size, T-cell, lymphoblastic lymphoma and histoplasmosis; lesions consistent with intestinal coccidiosis and suspected pulmonary Rhodococcus equi were also noted. Although dimorphic fungi have been described previously in goats, lesions of Histoplasma spp. had not been documented in this species, to our knowledge. Given the low disease burden, it is suspected that the lymphoma was primary, leading to an immunocompromised state and development of secondary, opportunistic infections.

Candida albicans Factor H Binding Molecule Hgt1p - A Low Glucose-Induced Transmembrane Protein Is Trafficked to the Cell Wall and Impairs Phagocytosis and Killing by Human Neutrophils

Complement is a tightly controlled arm of the innate immune system, facilitating phagocytosis and killing of invading pathogens. Factor H (FH) is the main fluid-phase inhibitor of the alternative pathway. Many pathogens can hijack FH from the host and protect themselves from complement-dependent killing. Candida albicans is a clinically important opportunistic yeast, expressing different FH binding molecules on its cell surface, which allow complement evasion. One such FH binding molecule is the transmembrane protein "High affinity glucose transporter 1" (Hgt1p), involved in glucose metabolism. This study demonstrated that Hgt1p transcription and expression is induced and highest at the low, but physiological glucose concentration of 0.1%. Thus, this concentration was used throughout the study. We also demonstrated the transport of Hgt1p to the fungal cell wall surface by vesicle trafficking and its release by exosomes containing Hgt1p integrated in the vesicular membrane. We corroborated Hgt1p as FH binding molecule. A polyclonal anti-Hgt1p antibody was created which interfered with the binding of FH, present in normal human serum to the fungal cell wall. A chimeric molecule consisting of FH domains 6 and 7 fused to human IgG1 Fc (FH6.7/Fc) even more comprehensively blocked FH binding, likely because FH6.7/Fc diverted FH away from fungal FH ligands other than Hgt1p. Reduced FH binding to the yeast was associated with a concomitant increase in C3b/iC3b deposition and resulted in significantly increased in vitro phagocytosis and killing by human neutrophils. In conclusion, Hgt1p also exhibits non-canonical functions such as binding FH after its export to the cell wall. Blocking Hgt1p-FH interactions may represent a tool to enhance complement activation on the fungal surface to promote phagocytosis and killing of C. albicans.

In Vitro and In Vivo Assessment of FK506 Analogs as Novel Antifungal Drug Candidates

FK506 (tacrolimus) is an FDA-approved immunosuppressant indicated for the prevention of allograft rejections in patients undergoing organ transplants. In mammals, FK506 inhibits the calcineurin-nuclear factor of activated T cells (NFAT) pathway to prevent T-cell proliferation by forming a ternary complex with its binding protein, FKBP12, and calcineurin. FK506 also exerts antifungal activity by inhibiting calcineurin, which is essential for the virulence of human-pathogenic fungi. Nevertheless, FK506 cannot be used directly as an antifungal drug due to its immunosuppressive action. In this study, we analyzed the cytotoxicity, immunosuppressive activity, and antifungal activity of four FK506 analogs, 31-O-demethyl-FK506, 9-deoxo-FK506, 9-deoxo-31-O-demethyl-FK506, and 9-deoxo-prolyl-FK506, in comparison with that of FK506. The four FK506 analogs generally possessed lower cytotoxicity and immunosuppressive activity than FK506. The FK506 analogs, except for 9-deoxo-prolyl-FK506, had strong antifungal activity against Cryptococcus neoformans and Candida albicans, which are two major invasive pathogenic yeasts, due to the inhibition of the calcineurin pathway. Furthermore, the FK506 analogs, except for 9-deoxo-prolyl-FK506, had strong antifungal activity against the invasive filamentous fungus Aspergillus fumigatus Notably, 9-deoxo-31-O-demethyl-FK506 and 31-O-demethyl-FK506 exhibited robust synergistic antifungal activity with fluconazole, similar to FK506. Considering the antifungal efficacy, cytotoxicity, immunosuppressive activity, and synergistic effect with commercial antifungal drugs, we selected 9-deoxo-31-O-demethyl-FK506 for further evaluation of its in vivo antifungal efficacy in a murine model of systemic cryptococcosis. Although 9-deoxo-31-O-demethyl-FK506 alone was not sufficient to treat the cryptococcal infection, when it was used in combination with fluconazole, it significantly extended the survival of C. neoformans-infected mice, confirming the synergistic in vivo antifungal efficacy between these two agents.

Role of microglia in fungal infections of the central nervous system

Most fungi are capable of disseminating into the central nervous system (CNS) commonly being observed in immunocompromised hosts. Microglia play a critical role in responding to these infections regulating inflammatory processes proficient at controlling CNS colonization by these eukaryotic microorganisms. Nonetheless, it is this inflammatory state that paradoxically yields cerebral mycotic meningoencephalitis and abscess formation. As peripheral macrophages and fungi have been investigated aiding our understanding of peripheral disease, ascertaining the key interactions between fungi and microglia may uncover greater abilities to treat invasive fungal infections of the brain. Here, we present the current knowledge of microglial physiology. Due to the existing literature, we have described to greater extent the opportunistic mycotic interactions with these surveillance cells of the CNS, highlighting the need for greater efforts to study other cerebral fungal infections such as those caused by geographically restricted dimorphic and rare fungi.

Rechargeable anticandidal denture material with sustained release in saliva

OBJECTIVE

Candida-induced denture stomatitis is a common debilitating problem among denture wearers. Previously, we described the fabrication of a new denture material that released antifungal drugs when immersed in phosphate buffered saline. Here, we use more clinically relevant immersion conditions (human saliva; 37°C) and measure miconazole release and bioactivity.

MATERIALS AND METHODS

Disks were prepared by grafting PNVP [poly(N-vinyl-2-pyrrolidinone)] onto PMMA [poly(methylmethacrylate)] using plasma initiation (PMMA-g-PNVP) and then loaded with miconazole. Drug-loaded disks were immersed in 10-100% human saliva (1-30 days). Miconazole release was measured and then tested for bioactivity vs miconazole-sensitive and miconazole-resistant Candida isolates.

RESULTS

HPLC was used to quantify miconazole levels in saliva. Miconazole-loaded disks released antifungal drug for up to 30 days. Higher drug release was found with higher concentrations of saliva, and, interestingly, miconazole solubility was increased with higher saliva concentrations. The released miconazole retained its anticandidal activity. After immersion, the residual miconazole could be quenched and the disks recharged. Freshly recharged disks displayed the same release kinetics and bioactivity as the original disks. Quenched disks could also be charged with chlorhexidine that displayed anticandidal activity.

CONCLUSIONS

These results suggest that PMMA-g-PNVP is a promising new denture material for long-term management of denture stomatitis.

Urinary Tract Infection (UTI) Caused by Fusarium proliferatum in an Agranulocytosis Patient and a Review of Published Reports

Infections caused by Fusarium species are increasing in frequency among immunocompromised hosts, but urinary tract infection (UTI) due to Fusarium proliferatum has not been reported in the literature so far. We describe a case of UTI caused by F. proliferatum in a 47-year-old man who was diagnosed with rectal cancer and metastasis. He underwent radical resection of rectal carcinoma and local resection of hepatic metastases. After the first adjuvant chemotherapy, the patient presented the obvious high fever, severely diarrhea and progressive decline of the white blood cell count. The direct microscopic examination of fungi in urine was positive, and the fungal cultures showed white, cotton-like colony. After the DNA sequencing, it was identified as F. proliferatum. We gave the patient itraconazole and other antibiotics to fight the infection. A month later, the temperature dropped to normal and the results of the direct microscopic examination and culture of fungi in urine turn negative. The itraconazole is effective against F. proliferatum.

Attritional extensor tendon rupture in a patient with Phialophora verrucosa tenosynovitis: case report

Deep tissue fungal infections of the hand are exceedingly uncommon. We present a case of fungal tenosynovitis caused by Phialophora verrucosa that led to extensor tendon rupture in a patient who was on chronic immunosuppressive therapy. Indolent fungal cysts can elude clinical diagnosis until excision is performed with definitive pathologic examination. In immunocompromised patients, antifungal therapy may be warranted after cyst excision even in the absence of acute infection to prevent subsequent progression to tenosynovitis.

In Vitro Antifungal Activity of Ankaferd Blood Stopper Against Candida albicans

BACKGROUND

Candida albicans is a memeber of the oral flora that can lead to various complications in immunosupresive patients after oral surgery processes. Ankaferd Blood Stopper® (ABS) is a medical plant extract that is safe to use in patients with dental surgery bleedings in Turkey.

OBJECTIVE

The study evaluated the antifungal activity of ABS medicinal plant extract against C albicans using the agar diffusion and broth microdilution methods.

METHODS

The plant extract antifungal activity was assessed in vitro either by applying the ABS extract directly and by applying different concentrations of ABS onto Candida culture. For these experiments, an agar diffusion method was used. To determine the minimum inhibitory concentration (MIC), a broth microdilution method was used.

RESULTS

Different volumes of the active substance (10, 20, 30, and 40 μL) were applied onto Candida (0.5 McFarland solution) cultivated plate; Candida growth was inhibited in accordance with the volumes of ABS. However, when various dilutions of ABS (1:2, 1:20, 1:40, and 1:80) were added as drops containing 20 μL, no antifungal effects were found. No MIC values were identified using broth microdilution. When different dilutions of ABS containing 100 μL of 0.5 McFarland solution of C albicans were cultured depending on the time (10, 20, 30, and 40 minutes), the effect of the duration was not significant.

CONCLUSION

The various tests were carried out to investigate antifungal effects of ABS on Candida, but none were found.

Successful management of sequential pulmonary infections in a cardiac transplant recipient

A case of a cardiac allograft recipient who had an initial combined pulmonary infection with cytomegalovirus, Aspergillus fumigatus and Nocardia asteroides, successfully treated with liposomal amphotericin B and sulfisoxazole and followed by an episode of respiratory syncytial virus pneumonitis, is presented. This case illustrates the role of computed tomographic imaging in the recognition, diagnosis and monitoring of complex opportunistic pulmonary infections and the benefits of liposomal amphotericin B in the treatment of aspergillosis.

Screening of Tanzanian medicinal plants for anti-Candida activity

Background

Candida albicans has become resistant to the already limited, toxic and expensive anti-Candida agents available in the market. These factors necessitate the search for new anti-fungal agents.

Methods

Sixty-three plant extracts, from 56 Tanzanian plant species obtained through the literature and interviews with traditional healers, were evaluated for anti-Candida activity. Aqueous methanolic extracts were screened for anti-Candida activity by bioautography agar overlay method, using a standard strain of Candida albicans (ATCC 90028).

Results

Twenty- seven (48%) out of the 56 plants were found to be active. Extracts of the root barks of Albizia anthelmintica and Balanites aegyptiaca, and roots of Plectranthus barbatus showed strong activity.

Conclusion

The extracts that showed strong anti-Candida activity are worth of further investigation in order to isolate and identify the active compounds.

Mutations in Aspergillus fumigatus resulting in reduced susceptibility to posaconazole appear to be restricted to a single amino acid in the cytochrome P450 14alpha-demethylase

To better understand the molecular basis of posaconazole (POS) resistance in Aspergillus fumigatus, resistant laboratory isolates were selected. Spontaneous mutants arose at a frequency of 1 in 10(8) and fell into two susceptibility groups, moderately resistant and highly resistant. Azole resistance in A. fumigatus was previously associated with decreased drug accumulation. We therefore analyzed the mutants for changes in levels of transcripts of genes encoding efflux pumps (mdr1 and mdr2) and/or alterations in accumulation of [(14)C]POS. No changes in either pump expression or drug accumulation were detected. Similarly, there was no change in expression of cyp51A or cyp51B, which encode the presumed target site for POS, cytochrome P450 14alpha-demethylase. DNA sequencing revealed that each resistant isolate carried a single point mutation in residue 54 of cyp51A. Mutations at the same locus were identified in three clinical A. fumigatus isolates exhibiting reduced POS susceptibility but not in susceptible clinical strains. To verify that these mutations were responsible for the resistance phenotype, we introduced them into the chromosome of a POS-susceptible A. fumigatus strain under the control of the glyceraldehyde phosphate dehydrogenase promoter. The transformants exhibited reductions in susceptibility to POS comparable to those exhibited by the original mutants, confirming that point mutations in the cyp51A gene in A. fumigatus can confer reduced susceptibility to POS.

Evaluation of a polymerase chain reaction reverse hybridization line probe assay for the detection and identification of medically important fungi in bronchoalveolar lavage fluids

An assay system in which polymerase chain reaction (PCR) amplification of the ITS-1 region of ribosomal DNA (rDNA) is combined with a reverse-hybridization line probe assay (LiPA) was used for the identification of six Candida species and four Aspergillus species in pure cultures of clinical isolates, as well as in bronchoalveolar lavage (BAL) fluid samples from 42 patients with various underlying diseases. The results were compared with the results obtained with conventional routine identification methods as well as with a commercial enzyme-linked immunosorbent assay (ELISA) galactomannan detection assay and an Aspergillus-specific PCR. No discrepancies between the PCR-LiPA system and routine methods were found for pure cultures of Candida and Aspergillus species except in the case of Aspergillus versicolor. In BAL fluid samples in which Candida species were cultured, the PCR-LiPA system identified more species than did the routine methods. When routine analyses of patient samples were supplemented by adding data obtained by repurifying and re-identifying cultures and by taking isolates obtained from other body sites into account, the results agreed with PCR-LiPA system results in 81% of the cases (34/42). Most of the remaining discrepancies (6/8) involved cases in which such supplementary data were not available. In BAL fluid samples from which A. fumigatus was cultured, the agreement between the PCR-LiPA system and the routine methods was low. Only 2 of 11 BAL samples shown to contain A. fumigatus in ELISA and genus-specific PCR assays were positive in PCR-LiPA system. The PCR-LiPA system enables the simultaneous detection and identification of different fungal species present in pure or mixed populations within 6 h in a single assay. Optimization is required, however, before it is useful as a diagnostic tool in the clinical microbiology laboratory.

PKSP-dependent reduction of phagolysosome fusion and intracellular kill of Aspergillus fumigatus conidia by human monocyte-derived macrophages

Previously, we described the isolation of an Aspergillus fumigatus mutant producing non-pigmented conidia, as a result of a defective polyketide synthase gene, pksP (polyketide synthase involved in pigment biosynthesis). The virulence of the pksP mutant was attenuated in a murine animal infection model and its conidia showed enhanced susceptibility towards damage by monocytes in vitro. Because macrophage-mediated killing is critical for host resistance to aspergillosis, the interaction of both grey-green wild-type conidia and white pksP mutant conidia with human monocyte-derived macrophages (MDM) was studied with respect to intracellular processing of ingested conidia. After phagocytosis, the percentage of wild-type conidia residing in an acidic environment was approximately fivefold lower than that observed for non-pigmented pksP mutant conidia. The phagolysosome formation, as assessed by co-localization of LAMP-1 and cathepsin D with ingested conidia, was significantly lower for wild-type conidia compared with pksP mutant conidia. Furthermore, the intracellular kill of pksP mutant conidia was significantly higher than of wild-type conidia, which was markedly increased by chloroquine, a known enhancer of phagolysosome fusion. Taken together, these findings suggest that the presence of a functional pksP gene in A. fumigatus conidia is associated with an inhibition of phagolysosome fusion in human MDM. These data show for the first time that a fungus has the capability to inhibit the fusion of the phagosome with the lysosome. This finding might help explain the attenuated virulence of pksP mutant strains in a murine animal model and provides a conceptual frame to understand the virulence of A. fumigatus.

In vitro activity of a new antifungal azolyl-substituted indole against Aspergillus fumigatus

A new 2-(alpha-azolylbenzyl)indole derivative exhibited high in vitro activity against 10 strains of Aspergillus fumigatus. This active compound, MT18n, had MIC of 2 microg/mL and is slightly less active than itraconazole and amphotericin B. The mechanism of action of this compound was evaluated through scanning electron microscopy, ergosterol biosynthesis inhibition and phospholipase A2-like activity inhibition studies. Scanning electron microscopy allowed observation of the membrane perturbations caused by MT18n and inference of a critical role of MT18n in membrane synthesis inhibition. Like other azole derivatives MT18n inhibits ergosterol biosynthesis, with a minimal inhibitory concentration of 6 microM. On the other hand, MT18n (10 microM) decreased the secreted phospholipase A2-like activity of Aspergillus fumigatus, an enzyme involved in the invasion process of the host. These results show the high in vitro activity of MT18n against Aspergillus fumigatus and suggest that this compound disturbs the membrane structure via ergosterol biosynthesis inhibition and exhibits phospholipase activity inhibition.

[Nosocomial fungemias in a general hospital. Epidemiology and prognostic factors. Prospective study 1993-1998]

BACKGROUND

Nosocomial fungemias are infections with a high mortality rate. In last years the incidence of these infections has increased probably because of the growing population of immunocompromised patients who undergo aggressive diagnostic and therapeutic techniques.

OBJECTIVE

To know the epidemiologic characteristics, risk factors, clinical features and prognosis of fungemia.

PATIENTS AND METHODS

We prospectively evaluated all the patients with proven fungemia in our center during a 5 year-period. After finishing antifungal treatment a minimum follow-up of 1 month was carried out. Fungal isolation and identification were performed by standard tests.

RESULTS

During the period of study we evaluated 81 patients with an episode of nosocomial fungemia. Global incidence was 0,9 episodes per thousand admitted patients. Candida albicans was the more frequently isolated species (n=53), followed by C. parapsilosis (n=11), C. tropicalis (n=6) and C. glabrata (n=5). Most of the patients had a central intravenous line and were on parenteral nutrition therapy. All of them previously received at least one course of broad-spectrum antibiotics. Overall mortality was 49,6%. A worst prognosis was significantly associated with: age over 65 years, surgical procedures during present admission, leucocytosis, shock, and delay in antifungal treatment.

CONCLUSIONS

Fungal bloodstream infection incidence is high in our environment. It is associated with a high mortality rate, specially in patients in whom the beginning of antifungal treatment was delayed. A higher clinical suspicion index may improve the poor outcome in these patients.

Candidacidal activities of human lactoferrin peptides derived from the N terminus

In light of the need for new antifungal agents, the candidacidal activities of human lactoferrin (hLF) and synthetic peptides representing the first, hLF(1-11), and second, hLF(21-31), cationic domains of its N terminus were compared. The results revealed that hLF(1-11) was more effective in killing fluconazole-resistant Candida albicans than hLF(21-31) and much more effective than lactoferrin, as determined microbiologically and by propidium iodide (PI) staining. By using hLF(1-11) and various derivatives, it was found that the second and third residues of the N terminus of hLF(1-11) were critical for its candidacidal activity. Detailed investigation to elucidate the mechanism of action of hLF(1-11) revealed a dose-dependent release of ATP by Candida upon exposure to hLF(1-11). Our observations that sodium azide reduced the PI uptake and candidacidal activity of hLF(1-11) and that, upon exposure to hLF(1-11), the fluorescent dye rhodamine 123 first accumulated inside the mitochondria and later was released into the cytoplasm indicate that the peptide triggers the energized mitochondrion. Furthermore, oxidized ATP, which interferes with the interaction of ATP with its extracellular receptors, blocked the candidacidal action of hLF(1-11), as measured microbiologically and by PI staining. Addition of ATP (or analogues) was not a sufficient stimulus to kill C. albicans or to act synergistically with suboptimal concentrations of the peptide. The main conclusions are that the first two arginines at the N terminus of hLF are critical in the candidacidal activity of hLF(1-11) and that extracellular ATP is essential but not sufficient for the peptide to exert its candidacidal activity.

Fine-resolution physical mapping of genomic diversity in Candida albicans

It has been suggested that Candida albicans, a diploid asexual fungus, achieves genetic diversity by genomic rearrangement. This important human pathogen may provide a system in which to analyze alternate routes to genomic diversity. C. albicans has a highly variable karyotype; its chromosomes contain a middle repeated DNA sequence called the Major Repeat Sequence (MRS), composed of subrepeats HOK, RPS, and RB2. RPS is tandemly repeated while the other subrepeats occur once in each MRS. Chromosome 7, the smallest of the eight chromosomes, has been previously mapped. The complete physical map of this chromosome was used to analyze chromosome 7 diversity in six strains, including two well-characterized laboratory strains (1006 and WO-1) and four clinical ones. We found four types of events to explain the genomic diversity: 1) Chromosome length polymorphism (CLP) results from expansion and contraction of the RPS; 2) reciprocal translocation occurs at the MRS loci; 3) chromosomal deletion; and (4) trisomy of individual chromosomes. These four phenomena play an important role in generating genomic diversity in C. albicans.

The incidence of opportunistic fungi in patients suspected of tuberculosis

The incidence of opportunistic fungi in bronchoalveolar lavage specimens from patients suspected of tuberculosis in Isfahan, Iran, was determined. From 200 patients 36 yeasts (18%) and seven filamentous fungi (3.5%) were isolated. Out of 44 patients who had fungal infections, 12 cases were affected with definite tuberculosis.

Purification, reconstitution, and inhibition of cytochrome P-450 sterol delta22-desaturase from the pathogenic fungus Candida glabrata

Sterol delta22-desaturase has been purified from a strain of Candida glabrata with a disruption in the gene encoding sterol 14alpha-demethylase (cytochrome P-45051; CYP51). The purified cytochrome P-450 exhibited sterol delta22-desaturase activity in a reconstituted system with NADPH-cytochrome P-450 reductase in dilaurylphosphatidylcholine, with the enzyme kinetic studies revealing a Km for ergosta-5,7-dienol of 12.5 microM and a Vmax of 0. 59 nmol of this substrate metabolized/min/nmol of P-450. This enzyme is encoded by CYP61 (ERG5) in Saccharomyces cerevisiae, and homologues have been shown in the Candida albicans and Schizosaccharomyces pombe genome projects. Ketoconazole, itraconazole, and fluconazole formed low-spin complexes with the ferric cytochrome and exhibited type II spectra, which are indicative of an interaction between the azole moiety and the cytochrome heme. The azole antifungal compounds inhibited reconstituted sterol delta22-desaturase activity by binding to the cytochrome with a one-to-one stoichiometry, with total inhibition of enzyme activity occurring when equimolar amounts of azole and cytochrome P-450 were added. These results reveal the potential for sterol delta22-desaturase to be an antifungal target and to contribute to the binding of drugs within the fungal cell.

Accumulation of amphotericin B in human macrophages enhances activity against Aspergillus fumigatus conidia: quantification of conidial kill at the single-cell level

A cytofluorometric assay that allowed assessment of damage to phagocytosed Aspergillus fumigatus conidia at the single-cell level was developed. After ingestion by monocyte-derived macrophages (MDMs), conidia were reisolated by treatment of the cells with streptolysin O, a pore-forming toxin with lytic properties on mammalian cells but not on fungi. The counts obtained by staining of damaged conidia with propidium iodide and quantification by cytofluorometry correlated with colony counts. By the use of this method, we demonstrate that MDMs differentiated in vitro by low-dose granulocyte-macrophage colony-stimulating factor and gamma interferon have only a limited capacity to damage Aspergillus conidia in vitro. The killing rate 12 h after phagocytosis was found to be only 10 to 15%. However, intracellular loading of the phagocytes with amphotericin B (AmB) dose dependently enhanced the anticonidial activity. Preincubation of macrophages with only 1 microg of AmB per ml resulted in an uptake of 18 fg of AmB/cell, leading to killing rates of 50 to 60%. The experimental protocol provides a new tool for the rapid quantification of anticonidial activity against A. fumigatus in vitro. Intracellular accumulation of AmB may represent an important factor underlying the efficacy of this antifungal drug in the prophylaxis and treatment of Aspergillus infections.

Diagnosis of fungal infections

Fungal infections become more and more important due to their increasing incidence in immunocompromised patients. In these patients opportunistic fungi (Candida, Aspergillus, Cryptococcus) can cause life-threatening infections. Diagnosis of fungal infections is difficult. Clinical symptoms are uncharacteristic, and laboratory diagnosis is confronted with many problems and requires expert interpretation.

The Role of Recombinant Murine IL-12 and IFN-γ in the Pathogenesis of a Murine Systemic Candida albicans Infection

Studies on murine candidiasis suggest that resistance to disease is linked to a Th1 response and production of IFN-γ, while failure to elicit protection is associated with a Th2 response and production of IL-4 and IL-10. Experimental infection of C57BL/6 mice, IL-12 treatment of these mice, or both infection and IL-12 treatment resulted in a characteristic Th1 cytokine mRNA profile as measured by quantitative competitive PCR. Specifically, little or no IL-4 transcripts were detected, while IFN-γ message was elevated, particularly with IL-12 treatment. Despite its role in driving increased IFN-γ expression and production, IL-12 treatment, paradoxically, promoted disease progression in our model. Therefore, we examined the effect of IFN-γ neutralization on IL-12-induced susceptibility to infection. None of the systemically infected mice receiving IL-12 alone survived, while IL-12- and anti-IFN-γ-treated mice had a 70% survival rate, similar to that after infection alone. These results suggested that IFN-γ induced by IL-12 treatment contributed to lethality. However, in separate studies, IFN-γ knockout mice were more susceptible to infection than their wild-type counterparts, suggesting that IFN-γ is required for resistance. Nonetheless, infected IFN-γ knockout mice treated with recombinant murine IL-12 exhibited enhanced resistance, suggesting that the toxicities observed with IL-12 are directly attributable to IFN-γ and that an optimal immune response to Candida infections necessitates a finely tuned balance of IFN-γ production. Thus, we propose that although IFN-γ can drive resistance, the overproduction of IFN-γ during candidiasis, mediated by IL-12 administration, leads to enhanced susceptibility.

Isolation and characterization of a pigmentless-conidium mutant of Aspergillus fumigatus with altered conidial surface and reduced virulence

Aspergillus fumigatus is an important pathogen of immunocompromised hosts, causing pneumonia and invasive disseminated disease with high mortality. The factors contributing to the predominance of A. fumigatus as an opportunistic pathogen are largely unknown. Since the survival of conidia in the host is a prerequisite for establishing disease, we have been attempting to identify factors which are associated with conidia and, simultaneously, important for infection. Therefore, an A. fumigatus mutant strain (white [W]) lacking conidial pigmentation was isolated. Scanning electron microscopy revealed that conidia of the W mutant also differed in their surface morphology from those of the wild type (WT). Mutant (W) and WT conidia were compared with respect to their capacities to stimulate an oxidative response in human phagocytes, their intracellular survival in human monocytes, and virulence in a murine animal model. Luminol-dependent chemiluminescence was 10-fold higher when human neutrophils or monocytes were challenged with W conidia compared with WT conidia. Furthermore, mutant conidia were more susceptible to killing by oxidants in vitro and were more efficiently damaged by human monocytes in vitro than WT conidia. In a murine animal model, the W mutant strain showed reduced virulence compared with the WT. A reversion analysis of the W mutant demonstrated that all phenotypes associated with the W mutant, i.e., altered conidial surface, amount of reactive oxygen species release, susceptibility to hydrogen peroxide, and reduced virulence in an murine animal model, coreverted in revertants which had regained the ability to produce green spores. This finding strongly suggests that the A. fumigatus mutant described here carries a single mutation which caused all of the observed phenotypes. Our results suggest that the conidium pigment or a structural feature related to it contributes to fungal resistance against host defense mechanisms in A. fumigatus infections.

Molecular cloning and expression of the Candida albicans TOP2 gene allows study of fungal DNA topoisomerase II inhibitors in yeast

Candida albicans topoisomerase II, encoded by the TOP2 gene, mediates chromosome segregation by a double-strand DNA break mechanism and is a potential target for anti-fungal therapy. In this paper, we report the characterization of the C. albicans TOP2 gene and its use to develop a yeast system that allows the identification and study of anti-fungal topoisomerase II inhibitors in vivo. The gene, specifying a 1461-residue polypeptide with only 40% identity with human topoisomerase IIalpha and beta isoforms, was isolated from C. albicans on a 6.3 kb EcoRI fragment that mapped to chromosome 4. It was used to construct a plasmid in which TOP2 expresses a recombinant enzyme (residues 57-1461 of C. albicans topoisomerase II fused to the first five residues of Saccharomyces cerevisiae topoisomerase II) under the control of a galactose-inducible promoter. The plasmid rescued the lethal phenotype of a temperature-sensitive S. cerevisiae DNA topoisomerase II mutant allowing growth at 35 degrees C. Yeast cells, bearing ISE2 permeability and rad52 double-strand-break-repair mutations the growth of which at 35 degrees C was dependent on C. albicans topoisomerase II, were killed by the known topoisomerase II inhibitors amsacrine and doxorubicin. Parallel experiments in yeast expressing human topoisomerase IIalpha allowed the relative sensitivities of the fungal and host topoisomerases to be examined in the same genetic background. To compare the killing in vivo with drug inhibition in vitro, the recombinant C. albicans topoisomerase II protein was expressed and purified to near-homogeneity from S. cerevisiae yielding a 160 kDa polypeptide that displayed the expected ATP-dependent DNA-relaxation and DNA-decatenation activities. The enzyme, whether examined in vitro or complementing in S. cerevisiae, was comparably sensitive to amsacrine and doxorubicin. Our results suggest that potential topoisomerase II-targeting anti-fungal inhibitors can be identified and studied in S. cerevisiae.

Preparation of mycobacterial DNA from blood culture fluids by simple alkali wash and heat lysis method for PCR detection

A sodium iodide-isopropanol (NI) method was compared with an alkali wash and heat lysis (AH) procedure for the preparation and extraction of DNA from BACTEC 13A blood culture fluid samples from AIDS patients for use in a PCR for the detection and identification of mycobacteria. The sensitivity and efficiency of the DNA extraction methods were assessed by a multiplex PCR which detected the members of the genus Mycobacterium and differentiated between M. intracellulare, M. tuberculosis, and M. avium isolates with a limit of detection of between 0.28 pg (67 cells) and 120 pg (28,571 cells) of standard mycobacterial DNA. The PCR amplified mycobacterial DNA prepared by the AH procedure from 40 acid-fast bacillus-positive blood cultures with growth index values of > 20 U but not from 48 blood cultures with growth index values of < 21 U. The AH method was about 10 times more sensitive than the NI method for extracting DNA from 13 acid-fast bacillus-positive BACTEC fluid samples for PCR analysis. The study shows that the AH procedure in combination with the multiplex PCR is a simple, specific, and sensitive method which can be used in the routine diagnostic laboratory to detect and identify different members of the genus Mycobacterium in blood culture fluid samples from AIDS patients.

New model of oropharyngeal and gastrointestinal colonization by Candida albicans in CD4+ T-cell-deficient mice for evaluation of antifungal agents

A new model for the evaluation of antifungal compounds against oropharyngeal and gastrointestinal mucosal colonization by Candida albicans was developed. To simulate the immune deficiency observed in AIDS patients, mice were depleted of CD4+ T lymphocytes by the injection of either GK1.5 hybridoma cells or purified anti-CD4+ T lymphocytes by the injection of either GK1.5 hybridoma cells or purified anti-CD4+ monoclonal antibody derived from GK1.5 hybridoma cells in tissue culture. Fluorescence-activated cell sorter analysis of splenic lymphocytes confirmed the elimination of the CD4+ T-cell population. Gentamicin, a broad-spectrum, nonabsorbable aminoglycoside antibiotic, was given via the drinking water to reduce the normal gastrointestinal microflora, allowing less competition for colonization of the gastrointestinal tract by the C. albicans isolates. Mice were challenged by gavage and swabbing their oral mucosae with a pure culture of C. albicans. Gentamicin was withdrawn 3 days postchallenge, and antifungal compounds were administered via the drinking water ad libitum at concentrations ranging from 25 to 400 micrograms/ml. L-693989, a water-soluble phosphorylated cyclic lipopeptide prodrug of pneumocandin Bo, and L-733560, a semisynthetic derivative of pneumocandin Bo, are inhibitors of 1,3-beta-D-glucan synthesis that exhibit potent in vivo anti-Candida spp. and anti-Pneumocystis carinii activities. The efficacies of L-693989, L-733560, fluconazole, ketoconazole, and nystatin were evaluated in this new oropharyngeal and gastrointestinal model of mucosal colonization. L-693989, L-733560, fluconazole, and ketoconazole showed superior efficacies in reducing the numbers of C. albicans CFU per gram of feces and the numbers of oral CFU relative to those in sham-treated controls in this model, while nystatin was moderately effective in reducing oral and fecal colonization by C. albicans in this model.

Isolation of opportunistic fungi from bronchoalveolar lavage of compromised hosts in Isfahan, Iran

In this study, bronchoalveolar lavage (BAL) specimens from 247 immunocompromised patients were investigated for the incidence of opportunistic fungi. In the direct examination and culture of the specimens, 5 (2.02%) of filamentous fungi and 55 (22.26%) yeasts were isolated and identified as follows: Aspergillus fumigatus (2), A. terreus (1), A. nidulans (1), Mucor sp. (1), Candida albicans (29), C. glabrata (3), C. Parapsilosis (1), Trichosporon beigelii (1), Candida sp. (13) and unknown yeasts (8). In addition, one strain of Nocardia asteroides and two strains of Streptomyces sp. were isolated.

Mechanisms of resistance to azole antifungal agents in Candida albicans isolates from AIDS patients involve specific multidrug transporters

Azole antifungal agents, and especially fluconazole, have been used widely to treat oropharyngeal candidiasis in patients with AIDS. An increasing number of cases of clinical resistance against fluconazole, often correlating with in vitro resistance, have been reported. To investigate the mechanisms of resistance toward azole antifungal agents at the molecular level in clinical C. albicans isolates, we focused on resistance mechanisms related to the cellular target of azoles, i.e., cytochrome P450(14DM) (14DM) and those regulating the transport or accumulation of fluconazole. The analysis of sequential isogenic C. albicans isolates with increasing levels of resistance to fluconazole from five AIDS patients showed that overexpression of the gene encoding 14DM either by gene amplification or by gene deregulation was not the major cause of resistance among these clinical isolates. We found, however, that fluconazole-resistant C. albicans isolates failed to accumulate 3H-labelled fluconazole. This phenomenon was reversed in resistant cells by inhibiting the cellular energy supply with azide, suggesting that resistance could be mediated by energy-requiring efflux pumps such as those described as ATP-binding cassette (ABC) multidrug transporters. In fact, some but not all fluconazole-resistant clinical C. albicans isolates exhibited up to a 10-fold relative increase in mRNA levels for a recently cloned ABC transporter gene called CDR1. In an azole-resistant C. albicans isolate not overexpressing CDR1, the gene for another efflux pump named BENr was massively overexpressed. This gene was cloned from C. albicans for conferring benomyl resistance in Saccharomyces cerevisiae. Therefore, at least the overexpression or the deregulation of these two genes potentially mediates resistance to azoles in C. albicans clinical isolates from AIDS patients with oropharyngeal candidiasis. Involvement of ABC transporters in azole resistance was further evidenced with S. cerevisiae mutants lacking specific multidrug transporters which were rendered hypersusceptible to azole derivatives including fluconazole, itraconazole, and ketoconazole.

Cerebral Pseudallescheria mycosis after near-drowning

Scedosporium apiospermum, an anamorph of Pseudallescheria boydii, is a hyalohyphomycete which can be mistaken, histologically, for Aspergillus. S. apiospermum is clinically distinguished by resistance to most antifungals and its ability to cause invasive mycoses in immunocompetent patients. Here we present a typical case of lethal cerebral Pseudallescheria mycosis in a child after near-drowning.

Rapid detection and identification of pathogenic fungi by polymerase chain reaction amplification of large subunit ribosomal DNA

We describe a polymerase chain reaction (PCR) based approach to the detection and identification of pathogenic fungi which has potential for the diagnosis of systemic mycoses. Primers to sequences of the large subunit ribosomal DNA genes, which are universally conserved within the fungal kingdom, were capable of amplifying DNA from 43 strains representing 20 species (12 genera) of medically important fungi. Sequence analysis of the products obtained from Aspergillus fumigatus, Candida albicans and Cryptococcus neoformans allowed us to design species-specific primers which only amplified homologous DNA. The use of these two PCRs in tandem allows the detection (universal PCR) and identification (species-specific PCR) of a fungal pathogen within 8 h from simulated clinical specimens.

Unusual effect of myo-inositol on phospholipid biosynthesis in Cryptococcus neoformans

Cryptococcus neoformans is an opportunistic fungal pathogen which preferentially localizes to the inositol-rich environment of the central nervous system. One of its distinguishing traits is its capacity to catabolize inositol. Inositol is a precursor for the synthesis of phosphatidylinositol (PI). This study demonstrated that C. neoformans synthesizes inositol. Three inositol-containing sphingolipids were identified in C. neoformans: ceramide-(P-inositol)2mannose, mannose, ceramide-P-inositol-mannose, and ceramide-P-inositol. These inositol-containing sphingolipids are typical of fungi but not higher eukaryotes. The effect of inositol on the membrane lipid composition of C. neoformans was also examined. In contrast to the nonpathogenic yeast Saccharomyces cerevisiae, neither the PI composition nor the synthesis of methylated phospholipids was altered by exogenous inositol. Hence, C. neoformans appears to have a metabolic mechanism for maintaining a steady lipid composition regardless of the inositol in its environment.

Growth and detection of filamentous fungi in the BacT/Alert blood culture system

Little is known about the behaviour of filamentous fungi in most blood culture systems, despite their increasingly recognised role in infections of immunocompromised hosts. The ability of the BacT/Alert system (Organon Teknika, Durham, North Carolina, USA) to detect the growth of 19 such fungi was examined. Eleven species grew and were detected rapidly; two species did not grow. Six species grew slowly, and were generally only recovered with terminal subculture after prolonged incubation. The CO2 production graph for some of these fungi showed a slow but steady rise, insufficient to cause the apparatus to signal positive. These results show that the BacT/Alert system may miss some fungi, either because of no growth in the medium or undetected slow growth. The latter problem could be overcome by prolonged incubation and terminal subculture when fungal infection is considered likely. Alteration of the signalling mechanism might permit earlier detection of some slow growing fungi.

[Laboratory diagnostic peculiarities of mycoses in immunosuppressed patients]

Domestic invasive mycoses are typically present as secondary diseases in patients definitely immunocompromised. This truth should not obscure the fact that a transient overload of the immune system, e.g. in the polytrauma patients, may likewise favour the development of mycoses. The two groups of patients show a comparable course of infection and, to some extent, diagnostic signs: surveillance cultures and monitoring of antibodies are more helpful with trauma patients and less reliable in the typically immunocompromised patients. In the latter, however, antigen tests may yield more reliable results than in the trauma patients. The different functional capacities of the immune system in the two groups of patients may also affect the appearance of fungal elements, particularly of aspergilli, in secretions and biopsies.

Susceptibility testing of Candida albicans and Aspergillus species by a simple microtiter menadione-augmented 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide assay

We describe a simple microtiter method for determining the susceptibility of Candida albicans and hyphal forms of Aspergillus fumigatus against antifungal agents. The assay measures mitochondrial respiration by determining reduction of 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) to formazan, a process that is enhanced in the presence of menadione. C. albicans or conidial suspensions of A. fumigatus are seeded into microtiter plates. Hyphal outgrowth of Aspergillus spp. was achieved by a 12 to 14-h culture at 30 degrees C. Antifungal agents (amphotericin B, fluconazole, itraconazole) were added to the cultures for 24 h. Thereafter, incubations were continued for 3 h in the presence of MTT plus 0.1 mM menadione. Formazan formation was quantified photometrically after extraction of the formazan with acid isopropanol. Well-defined dose-response curves reflecting impairment of mitochondrial function by the antifungal agents were obtained. With C. albicans, the results correlated excellently with the MIC determinations performed according to the standard macrodilution procedure. In confirmation of a recent report, it was found that fluconazole was unable to exert its fungistatic action on a sensitive C. albicans strain in the presence of serum. The presented method can easily be integrated in the standard repertoire of a diagnostic microbiology laboratory and should prove useful as a means to assess the antifungal action of various agents on yeasts and filamentous fungi in the presence and absence of serum proteins or body fluids.

Orointestinal yeast colonization of paediatric oncologic patients during antifungal prophylaxis: results of quantitative culture and Candida serology and comparison of three polyenes

The orointestinal yeast colonization of 46 children with newly diagnosed malignancies was studied prospectively and longitudinally with quantitative cultures during remission induction chemotherapy. The initial colonization rate was 24%; only 28% of the patients remained free of yeasts during their entire treatment although all of them continuously received oral polyenes as antifungal prophylaxis. A randomized comparison of natamycin (suspension, lozenges), nystatin (suspension) and amphotericin B (suspension, lozenges) failed due to serious problems with patient compliance. Natamycin was best accepted by the patients and natamycin lozenges were the most efficacious drug in the oral cavity. The effectivity of the suspensions of nystatin and amphotericin B was similar; both were equally efficacious in the oral cavity and the gut. Assessment of faecal polyene concentrations by HPLC showed the highest results for amphotericin B (mean 6808 microgram(-1)). Regularly performed Candida serology (indirect haemagglutination, indirect immunofluorescence and immunodiffusion precipitation) revealed significant titre increases in 63% of the patients. In six cases, the synopsis of clinical picture, culture and serology strongly suggested systemic yeast invasion.

Murine yeast gut flora affected by tetracycline, metronidazole and norfloxacin

Three-month old, male Crl:CD1(ICR) BR mice, were fed food containing Candida albicans, while other mice of the same type were fed regular food. Both groups of mice were subsequently given orally either antibiotics or normal saline for a 10-day period. The stools of all mice were cultured before, at the end, and one week after the end of the antibiotic treatment, to determine the level of gut colonization by the yeast. The mice fed Candida and treated with antibiotics had substantially higher Candida counts in their stools than control mice fed C. albicans and treated with saline. The concentrations of Candida in the stools of mice treated with tetracycline were much higher when compared to those of mice treated with metronidazole and norfloxacin. Tetracycline was associated with a statistically significant increase of gastrointestinal Candida colonization. Yeast was not found in the stools of mice fed regular food and treated with antibiotics or saline. Histopathologic examination did not reveal dissemination of Candida in the visceral organs of any mouse.

Molecular and functional analysis of the LYS1 gene of Candida albicans

The LYS1 gene of Candida albicans has been localized to a 1.8-kb DNA fragment present on the plasmid YpBRG2. YpBRG2 has been shown to complement the saccharopine dehydrogenase mutant Stx4-4A of Saccharomyces cerevisiae. Transformants of S. cerevisiae Stx4-4A exhibited significant saccharopine dehydrogenase activity, and cells that had lost YpBRG2 after nonselective growth had no enzyme activity. The DNA sequence of the LYS1 gene has been determined. The LYS1 DNA contains typical yeast upstream regulatory sequences, including the GCN4 motif and candidate sequences responsible for transcription termination within the 3' noncoding region. The fragment contained an open reading frame of 1,146 nucleotides coding for a putative protein of 382 amino acids. The open reading frame has 60% identity at the nucleotide level and 71% similarity at the amino acid level to the LYS5 gene of Yarrowia lipolytica, which is believed to code for saccharopine dehydrogenase. A peptide of 11 amino acids has been found, which is present in S. cerevisiae, Y. lipolytica, and C. albicans. This peptide can be expanded to 16 amino acids when the sequences from Y. lipolytica and C. albicans are compared. A motif responsible for the binding of the adenosine residue of NADH has been described previously and is very similar to this peptide, which may be the site of NADH binding in the saccharopine dehydrogenase of C. albicans.

Aspergillosis in immunocompromised children with acute myeloid leukemia and bone marrow aplasia. Report of two cases

Two cases of Aspergillosis in immunocompromised children are reported. Both were caused by Aspergillus flavus. Early diagnosis and treatment led to the remission of the process. One patient had acute myeloid leukemia; the fungus was isolated from the blood. The other patient with bone marrow aplasia, presented an invasive aspergillosis of the paranasal sinuses with dissemination of fungal infection; the diagnosis was obtained by histology and culture of biopsied tissue from a palatal ulceration.

Rapid detection and identification of Candida albicans and Torulopsis (Candida) glabrata in clinical specimens by species-specific nested PCR amplification of a cytochrome P-450 lanosterol-alpha-demethylase (L1A1) gene fragment

PCR of a Candida albicans cytochrome P-450 lanosterol-alpha-demethylase (P450-L1A1) gene segment is a rapid and sensitive method of detection in clinical specimens. This enzyme is a target for azole antifungal action. In order to directly detect and identify the clinically most important species of Candida, we cloned and sequenced 1.3-kbp fragments of the cytochrome P450-L1A1 genes from Torulopsis (Candida) glabrata and from Candida krusei. These segments were compared with the published sequences from C. albicans and Candida tropicalis. Amplimers for gene sequences highly conserved throughout the fungal kingdom were first used; positive PCR results were obtained for C. albicans, T. glabrata, C. krusei, Candida parapsilosis, C. tropicalis, Cryptococcus neoformans, and Trichosporon beigelii DNA extracts. Primers were then selected for a highly variable region of the gene, allowing the species-specific detection from purified DNA of C. albicans, T. glabrata, C. krusei, and C. tropicalis. The assay sensitivity as tested for C. albicans in seeded clinical specimens such as blood, peritoneal fluid, or urine was 10 to 20 cells per 0.1 ml. Compared with results obtained by culture, the sensitivity, specificity, and efficiency of the species-specific nested PCR tested with 80 clinical specimens were 71, 95, and 83% for C. albicans and 100, 97, and 98% for T. glabrata, respectively.