Clinical applications of non-culture based methods for the diagnosis and management of opportunistic and endemic mycoses

Immunomodulatory therapy in yeast infections

Invasive yeast infections are a significant cause of morbidity and mortality in patients with defective immune response, such as those with cancer-related immunosuppression, organ transplantation or other immunodeficiencies, and neonates. Hospitalization in the intensive care unit may increase the risk for such infections. Despite the advent of new antifungal agents, the problem is escalating as the number of susceptible hosts increase and virulent, more resistant fungal strains emerge. Over the past few years, advances in immunology and molecular biology have greatly contributed to a better understanding of the pathogenesis of yeast infections. There is evidence that reconstitution of the host immune function is a major contributor to the resolution of yeast infections. Strategies aiming to increase the phagocyte number (e.g., granulocyte transfusions), to stimulate immune response (e.g., administration of hematopoietic growth factors and other proinflammatory cytokines) and to stimulate antigen-specific immunity (e.g., antibody therapy or vaccination) benefit patients at risk of, or suffering from, yeast infections. Further preclinical and clinical studies, as well as improving our understanding of immune system functions and dysfunctions, remain a future challenge.

Detection of a molecular biomarker for zygomycetes by quantitative PCR assays of plasma, bronchoalveolar lavage, and lung tissue in a rabbit model of experimental pulmonary zygomycosis

We developed two real-time quantitative PCR (qPCR) assays, targeting the 28S rRNA gene, for the diagnosis of zygomycosis caused by the most common, clinically significant Zygomycetes. The amplicons of the first qPCR assay (qPCR-1) from Rhizopus, Mucor, and Rhizomucor species were distinguished through melt curve analysis. The second qPCR assay (qPCR-2) detected Cunninghamella species using a different primer/probe set. For both assays, the analytic sensitivity for the detection of hyphal elements from germinating sporangiospores in bronchoalveolar lavage (BAL) fluid and lung tissue homogenates from rabbits was 1 to 10 sporangiospores/ml. Four unique and clinically applicable models of invasive pulmonary zygomycosis served as surrogates of human infections, facilitating the validation of these assays for potential diagnostic utility. For qPCR-1, 5 of 98 infarcted lung specimens were positive by qPCR and negative by quantitative culture (qCx). None were qCx positive only. Among 23 BAL fluid samples, all were positive by qPCR, while 22 were positive by qCx. qPCR-1 detected Rhizopus and Mucor DNA in 20 (39%) of 51 serial plasma samples as early as day 1 postinoculation. Similar properties were observed for qPCR-2, which showed greater sensitivity than qCx for BAL fluid (100% versus 67%; P = 0.04; n = 15). The assay detected Cunninghamella DNA in 18 (58%) of 31 serial plasma samples as early as day 1 postinoculation. These qPCR assays are sensitive and specific for the detection of Rhizopus, Mucor, Rhizomucor, and Cunninghamella species and can be used for the study and detection of infections caused by these life-threatening pathogens.

Candida albicans metabolite affects the cytoskeleton and phagocytic activity of murine macrophages

Candida albicans is the most common opportunistic fungal pathogen of humans, causing systemic disease in immunocompromised patients. Host resistance to C. albicans infections is mediated predominantly by neutrophils and monocytes/macrophages. We have previously shown that exposure of a human epithelial cell line (HEp2) to C. albicans or to a culture filtrate of C. albicans caused actin rearrangement in the HEp2 cells. Since shifting of actin from the filamentous to the globular form may be crucial to the activity of phagocytes, we assessed in the present study the effect of the C. albicans metabolite (lyophilized culture filtrate) on the cytoskeleton of murine peritoneal macrophages and on their phagocytic activity. Our results showed a significant decrease in phagocytosis of C. albicans, ranging from 53-63% and a 25% reduction for C. glabrata cells. Using confocal laser scanning microscopy an actin rearrangement in the macrophages could be demonstrated that may be associated with the decrease of phagocytosis. We also tested the effect of mannan and of the secreted aspartic proteinase (Sap) inhibitor--pepstatin, on the activity of the metabolite in order to define the putative component and found no influence. In conclusion, our data indicate that a C. albicans metabolite affects phagocytic activity of macrophages, probably by alterations in their cytoskeleton.

Elevation of activated platelet-dependent chemokines and soluble cell adhesion molecules in patients with hematologic malignancies and high levels of beta-D-glucan

Most invasive fungal infections such as candidemia are frequent in patients with hematologic malignancies. We measured cytokines/chemokines (IL-6, IL-8, monocytic chemoattractant protein 1, RANTES and epithelial neutrophil-activating peptide 78), soluble molecules (sFas, sE-selectin and soluble vascular cell adhesion molecule 1) and platelet activation markers (soluble CD40 ligand, sP-selectin and platelet-derived microparticles) in patients with hematologic malignancies under prophylactic treatment with an antifungal drug (fosfluconazole). We classified patients into 2 groups by the level of beta-D-glucan. The level of C-reactive protein was higher in the high beta-D-glucan group (>5 pg/ml) than in the low beta-D-glucan group. However, there were no differences in the levels of other parameters (peripheral blood cells, glutamic-oxaloacetic transaminase, glutamic-pyruvic transaminase, lactate dehydrogenase, blood urea nitrogen and creatinine). Patients in the high beta-D-glucan group exhibited a significant elevation of several chemokines, soluble molecules and platelet activation markers compared with those in the low beta-D-glucan group, but the levels of IL-8, monocytic chemoattractant protein 1 and sFas did not differ significantly. The levels of C-reactive protein and IL-6 increased significantly after 1 or 2 weeks on fosfluconazole in both groups. In contrast, the high beta-D-glucan group exhibited a significant decrease in chemokines, soluble markers and platelet-derived microparticles compared with the low beta-D-glucan group after treatment with fosfluconazole, although the patients in the low beta-D-glucan group exhibited no significant changes. Furthermore, the levels of RANTES, epithelial neutrophil-activating peptide 78, soluble vascular cell adhesion molecule 1 and sE-selectin correlated positively with platelet-derived microparticles in the high beta-D-glucan group. These findings suggest that fungal infection may modulate the vascular events in which some platelet-related chemokines are involved.

Assessment of the clinical utility of serial β-d-glucan concentrations in patients with persistent neutropenic fever

The performance of the Fungitell assay was investigated in 100 patients with haematological malignancy undergoing chemotherapy who developed antibiotic-unresponsive neutropenic fever (AUNF). Serum β-d-glucan (BG) concentrations were significantly elevated on the first day of AUNF and all subsequent alternate days to day 10 in 38 patients who developed an invasive fungal infection (IFI) compared to 42 patients remaining free of such infections. The mean and median values of BG were 171.9±29.6 and 95.8 pg ml−1, respectively, for patients with IFI and 64.4±17.1 and 32.9 pg ml−1 for patients with only AUNF (P<0.0001). The differences remained significant over the 10 days despite antifungal therapy. The occurrence of ≥2 sequential concentrations of ≥80 pg ml−1 (‘positive’ test) was found to give the best overall option for diagnosis, with an accuracy of 81.3 %, sensitivity of 86.8 %, positive predictive value of 76.7 % and negative predictive value of 86.5 %. Of the patients with an IFI, 78 % developed a positive test at or before the clinical diagnosis was made – this occurred at a mean (range) of 1.25 (−14 to +14) days prior to the IFI diagnosis. By starting sampling of blood from the first day of neutropenia rather than from the first day of AUNF, 50 % of the patients with subsequent IFI would have been identified 5 days earlier. Increasing sampling to daily from alternate-day frequency did not further improve this earlier timing of an IFI diagnosis. A greater proportion of patients with persistent high levels of BG without overt IFI had severe enterocyte damage or mucositis than those with lower levels of BG without IFI (P=0.002). If the results of the initial BG test had been acted on to change antifungal therapy, discontinuation would have been inappropriate in 30 % of patients and would have delayed definitive antifungal therapy. Although the findings for the cohort of patients studied are very useful, there is inter-patient variability in the test's performance. An holistic diagnostic approach is therefore necessary to interpret the test results optimally. Future studies should address this in further detail as well as the impact of empirical antifungal drug use and patient outcome.

Compartmentalized intrapulmonary pharmacokinetics of amphotericin B and its lipid formulations

We investigated the compartmentalized intrapulmonary pharmacokinetics of amphotericin B and its lipid formulations in healthy rabbits. Cohorts of three to seven noninfected, catheterized rabbits received 1 mg of amphotericin B deoxycholate (DAMB) per kg of body weight or 5 mg of either amphotericin B colloidal dispersion (ABCD), amphotericin B lipid complex (ABLC), or liposomal amphotericin B (LAMB) per kg once daily for a total of 8 days. Following sparse serial plasma sampling, rabbits were sacrificed 24 h after the last dose, and epithelial lining fluid (ELF), pulmonary alveolar macrophages (PAM), and lung tissue were obtained. Pharmacokinetic parameters in plasma were derived by model-independent techniques, and concentrations in ELF and PAM were calculated based on the urea dilution method and macrophage cell volume, respectively. Mean amphotericin B concentrations +/- standard deviations (SD) in lung tissue and PAM were highest in ABLC-treated animals, exceeding concurrent plasma levels by 70- and 375-fold, respectively (in lung tissue, 16.24 +/- 1.62 versus 2.71 +/- 1.22, 6.29 +/- 1.17, and 6.32 +/- 0.57 microg/g for DAMB-, ABCD-, and LAMB-treated animals, respectively [P = 0.0029]; in PAM, 89.1 +/- 37.0 versus 8.92 +/- 2.89, 5.43 +/- 1.75, and 7.52 +/- 2.50 mug/ml for DAMB-, ABCD-, and LAMB-treated animals, respectively [P = 0.0246]). By comparison, drug concentrations in ELF were much lower than those achieved in lung tissue and PAM. Among the different cohorts, the highest ELF concentrations were found in LAMB-treated animals (2.28 +/- 1.43 versus 0.44 +/- 0.13, 0.68 +/- 0.27, and 0.90 +/- 0.28 microg/ml in DAMB-, ABCD-, and ABLC-treated animals, respectively [P = 0.0070]). In conclusion, amphotericin B and its lipid formulations displayed strikingly different patterns of disposition in lungs 24 h after dosing. Whereas the disposition of ABCD was overall not fundamentally different from that of DAMB, ABLC showed prominent accumulation in lung tissue and PAM, while LAMB achieved the highest concentrations in ELF.

Management of intracranial fungal infections in patients with haematological malignancies

The incidence of, and mortality associated with, invasive fungal infections remains far higher than hoped. As a consequence of the overall increase in the incidence of such infections over time, the incidence of central nervous system (CNS) fungal infections is also increasing and, despite improvements in diagnostic techniques and the introduction of novel antifungal agents, therapy for CNS infections is still associated with discouragingly poor results. In patients with haematological malignancies, opportunistic infections with Candida or Aspergillus remain the most common infections affecting the CNS; however, opportunistic infections with less well-known fungi are becoming more common and must be considered in the differential diagnosis. New techniques for the early diagnosis of invasive fungal infections are emerging. Pharmacologic options for treating invasive fungal infections have also improved during the past few years, with new drugs becoming available that have broader antifungal spectra and better safety profiles. Other novel treatment approaches, such as combination therapy, are also being explored. Early investigations have produced encouraging results; however, large, prospective studies involving many patients are necessary to validate the widespread use of these approaches. This review analyses the existing guidelines for treatment of CNS fungal infections and the literature available on the use of new drugs to generate sets of recommendations for treatment of these life-threatening infections in patients with haematological malignancies.

Comparison of non-culture-based methods for detection of systemic fungal infections, with an emphasis on invasive Candida infections

The accepted limitations associated with classic culture techniques for the diagnosis of invasive fungal infections have lead to the emergence of many non-culture-based methods. With superior sensitivities and quicker turnaround times, non-culture-based methods may aid the diagnosis of invasive fungal infections. In this review of the diagnostic service, we assessed the performances of two antigen detection techniques (enzyme-linked immunosorbent assay [ELISA] and latex agglutination) with a molecular method for the detection of invasive Candida infection and invasive aspergillosis. The specificities for all three assays were high (> or = 97%), although the Candida PCR method had enhanced sensitivity over both ELISA and latex agglutination with values of 95%, 75%, and 25%, respectively. However, calculating significant sensitivity values for the Aspergillus detection methods was not feasible due to a low number of proven/probable cases. Despite enhanced sensitivity, the PCR method failed to detect nucleic acid in a probable case of invasive Candida infection that was detected by ELISA. In conclusion, both PCR and ELISA techniques should be used in unison to aid the detection of invasive fungal infections.

Interferon-gamma and colony-stimulating factors as adjuvant therapy for refractory fungal infections in children

A human immunodeficiency virus-infected boy with Scedosporium apiospermum otomastoiditis and a girl with diabetes mellitus and Mucor sinusitis and orbital cellulitis had life-threatening disease progression despite antifungal treatment. Interferon-gamma and granulocyte-macrophage or granulocyte colony-stimulating factor were added, with good functional outcome in both children. Adjunctive therapy with interferon-gamma, granulocyte-macrophage colony-stimulating factor and granulocyte colony-stimulating factor can be considered for refractory invasive fungal infections.

Laboratory diagnosis of invasive mycoses

Rising numbers of immunocompromised patients have led to an ever-increasing population at risk of invasive fungal disease. Much has been achieved in the laboratory diagnosis of these infections, such as advances in blood culture systems, and the development of new biochemical, antigen detection assays, and molecular methodologies. More standardized susceptibility testing guidelines provide for better therapeutic interventions. In an era of economic cutbacks in health care, future challenges include the development of cost-effective and technically simplified systems, which provide early detection and identification of common and emerging fungal pathogens. It will, however, take some time to establish the clinical relevance of these new methodologies in different patient populations.

Adjunctive immune therapy for fungal infections

Fungal infections in immunocompromised patients can pose difficult problems in clinical management, because the available antifungal chemotherapy is often unable to eradicate the infection in these people. Hence, the use of immune modulating therapy to augment impaired host immune responses--and thus enhance the efficacy of antifungal drugs--is a reasonable approach to improve the prognosis of fungal infections. Advances in biotechnology have produced a variety of biological response modifiers with the potential to serve as adjunctive immune therapy for the treatment of fungal infections, including cytokines, monoclonal antibodies, and cell growth factors. In recent years, immune-modulating therapies have been studied in an effort to define their potential use for the treatment of fungal infections. Much of the available information on the use of this approach is encouraging and invites further investigation--with the caveats that the information is mostly anecdotal and that immune-modulating therapy occasionally has produced adverse effects.