Utilidad de los marcadores biológicos en el diagnóstico de la candidiasis invasora

[Invasive fungal disease: conventional or molecular mycological diagnosis?]

Diagnosis of invasive mycoses is a difficult challenge due to the limitations and low sensitivity of traditional microbiology methods which lead to diagnostic and therapeutic delays. The aim of this review is to summarise the state of the art of the molecular diagnosis of invasive fungal disease and to clarify its current role in the clinical practice. Conventional microbiological methods could be complemented with molecular methods in the rapid and definitive identification of fungal isolates. Biomarkers (β-glucan, galactomannan) are very useful in immunocompromised patients and have been included as probable invasive mycoses by the EORTC/MSG. Nucleic acid detection is currently used as a complementary tool for diagnosis. However, PCR can be very useful in mould invasive mycoses. Finally, the combined detection using biomarkers can improve the diagnosis. However, their applicability in the microbiology laboratory is not so easy and further studies are required for the appropriate evaluation of its clinical usefulness.

Candida colonization index in patients admitted to an ICU

Multiple-site colonization with Candida spp. is commonly recognized as a risk factor for invasive fungal infection in critically ill patients. We carried out a study to determine the relationship between Candida colonization and invasive infection in neurological patients admitted to an ICU. At admission (T0) and every three days for two weeks, different samples (pharynx swab, tracheal secretions, stomach contents, etc.) were collected for mycological surveillance. Candida mannan antigen and Candida anti-mannan antibodies were assayed. The Colonization Index (CI) and Corrected Colonization Index were calculated for each time point. Of all patients 70% was already colonized by Candida spp. at T0 and six of them had CI ≥ 0.5. Three patients developed candidemia; they had CI ≥ 0.5 before infection. Positive values of Candida mannan antigen and anti-mannan antibodies were found only in the patients with candidemia. The sensitivity and specificity of the Candida mannan test were 66.6% and 100%, respectively, while the sensitivity and specificity of the anti-mannan antibody test were 100%. In accordance with other authors, we find the surveillance cultures are useful to monitor the Candida colonization in ICU patients. In addition, the sequential observation of anti-mannan antibodies could contribute to early diagnosis of candidiasis more than Candida mannan antigen in immunocompetent patients.

Fungal infections in severe acute pancreatitis

Severe acute pancreatitis (SAP) is associated with significant morbidity and mortality. The majority of deaths related to SAP are the result of infectious complications. Although bacterial infections are most commonly encountered, fungal infections are increasingly being recognized. Candida is the most common fungal infection. The occurrence of fungal infection in patients with acute pancreatitis adversely affects the clinical course, leading to a higher incidence of systemic complications, and possibly mortality as well. Important risk factors for fungal infection in patients with acute pancreatitis include broad-spectrum antibiotics, prolonged hospitalization and surgical/endoscopic interventions, use of total parenteral nutrition, and mechanical ventilation. Patients with higher severity of pancreatitis are at a greater risk. The pathogenesis of fungal infection in patients with acute pancreatitis is multifactorial. Translocation of microorganisms across the gut epithelium, lymphocyte dysfunction, and the virulence of the invading microorganisms play important roles. Histological demonstration of fungi remains the gold standard of diagnosis, but a positive biopsy is rarely obtained. The role of biomarkers in the diagnosis is being investigated. As early diagnosis and treatment can lead to improved outcome, a high index of suspicion is required for prompt diagnosis. Limiting the use of broad-spectrum antibiotics, early introduction of enteral nutrition, and timely change of vascular catheters are important preventive strategies. The role of antifungal prophylaxis remains controversial. Surgical necrosectomy with antifungal therapy is the most widely used treatment approach. Clinical trials on antifungal prophylaxis are needed, and indications for surgical intervention need to be clearly defined.

Fungal infection in a patient with multiple sclerosis

Multiple sclerosis (MS) is a chronic, inflammatory disease of the central nervous system, whose causes are still unknown. We have proposed that MS, as well as some ophthalmologic diseases, are associated with fungal infection. In the present study, we closely monitored a patient with MS over a three-year period. Antibodies against different Candida spp. were detected in peripheral blood serum, although the titer of these antibodies fluctuated. The presence of fungal macromolecules, such as proteins, polysaccharides, and DNA, was also tested. In several sera samples, antigens related to C. famata were evidenced by the slot-blot test using a rabbit polyclonal antibody against these species, while high levels of β-1,3 glucan were detected with the commercial Fungitell assay. Despite the variations by sample, we concluded that all fungal macromolecules, that is, proteins, polysaccharides, and DNA, were present in blood from the MS patient which was analyzed. Several fungal species were identified using polymerase chain reaction (PCR) followed by sequencing. Antibodies against Candida spp. as well as C. famata-related antigens were also detected in cerebrospinal fluid (CSF). Our findings provide support for the notion that disseminated mycosis is present in this patient.

Potential of anti-Candida antibodies in immunoprophylaxis

The need for new options for the treatment of invasive candidiasis has fuelled the use of antibodies in combination with conventional antifungal therapy. After a long period of time in which antibodies were considered irrelevant in the resistance against invasive candidiasis, it was demonstrated that a number of antibodies or their engineered derivatives directed against Candida albicans cell-wall polysaccharides and glycopeptides, as well as against some protein epitopes, confer protection against invasive candidiasis. This has confirmed this approach as a new strategy for the prophylaxis of invasive candidiasis. Of particular interest is Mycograb, a human recombinant monoclonal antibody that inhibits heat shock protein 90, and has been administrated in combination with lipid-associated amphotericin B to patients with invasive candidiasis, and the fungicidal anti-beta-glucan antibodies induced by the glycoconjugate vaccine composed of a beta-glucan polysaccharide conjugated with the diphtheria toxoid CRM 197. However, despite the promising data obtained in vitro and in animal models, at present there is very little clinical experience on the use of antibodies in Candida immunoprophylaxis.