Positive Result of the Aspergillus Galactomannan Antigen Assay Using Bronchoalveolar Lavage Fluid from a Patient with an Invasive Infection Due to Lichtheimia ramosa

Abstract

ᰔPositive galactomannan antigen (GM) test results with serum by the Platelia Aspergillus assay (Bio-Rad, Marnes-LaCoquette, France) have been reported to occur during invasive fungal infections caused by Penicillium marneffei (8), Cryptococcus neoformans (2), Geotrichum capitatum (3), or Histoplasma capsulatum (1,6, 11). We report on a case of a positive GM result in bronchoalveolar lavage fluid (BAL fluid) in the clinical setting of a possibly invasive infection caused by Lichtheimia ramosa. The patient was a 10-year-old girl with acute myeloblastic leukemia in second relapse who presented with fever (101°F), cough, and dyspnea. A chest X ray showed diffuse reticular changes, and a blood count revealed severe neutropenia (200 leukocytes/l). The patient began empirical treatment with ceftazidime and amikacin. Vancomycin was later added on the basis of Gram stain results from a positive blood culture. A computed tomography (CT) scan was performed 48 h after admission. A nodular lesion in the right upper lobe compatible with invasive aspergillosis was observed. Voriconazole therapy was then initiated. Worsening of the patient's clinical condition prompted the addition of meropenem and caspofungin to the antibiotic regimen. Fiberoptic bronchoscopy was performed (14 days after admission), and BAL fluid in saline solution was submitted to the Microbiology Service for microscopic examination, culture, and GM testing. Nonseptate hyphae with irregular branching were seen by calcofluor white staining of a direct smear. Lichtheimia ramosa (deposited in the Spanish Type Culture Collection) was isolated on Sabouraud glucose medium within 48 h of plating. Microbial identification was confirmed by direct sequencing of the internal transcribed spacer 2 (ITS2) region of the ribosomal DNA gene (9). The antifungal susceptibility profile as determined by a conventional microdilution method was as follows: the isolate was susceptible to amphotericin B (0.25 g/ml) and posaconazole (0.5 g/ml) and resistant to the echinocandins (Ͼ8 g/ml). The BAL fluid (two different aliquots) tested positive by the GM assay (index value, 2.9). The positive results were reproduced in a second analysis of samples. Aspergillus species DNA was not detected in BAL fluid by realtime PCR (FXG:RESP Asp ϩ test kit and Cepheid SmartCycler; Myconostica Ltd., Manchester, United Kingdom). The patient was admitted to the intensive care unit and died shortly thereafter. Serial serum samples obtained at hospital admission until 16 h prior to death (n ϭ 3) tested negative by the GM assay (index values of 0.103, 0.104, and 0.107).A mycelial extract antigen from the isolated organism was prepared (4) and tested at a 1:100 dilution in phosphate-buffered saline by the GM assay, yielding a positive result (index value, 1.23). Extracellular polysaccharide antigens produced by Zygomycetes, such as Rhizopus oryzae, Lichtheimia corymbifera, and Cunninghamella bertholletiae (but not by Lichtheimia ramosa), have been shown previously to test negative (index values Յ 0.5) in the...

Using Immunohistochemistry to Assess the Accuracy of Histomorphologic Diagnosis of Aspergillosis and Mucormycosis

“…Another possible explanation could be crossreaction between the mucormycosis antigen and GM. This hypothesis is supported by a report of positive BAL GM results in patients with invasive mucormycosis [19], although no crossreactivity has been observed with culture supernatants of agents of mucormycosis [20,21]. Alternatively, Aspergillus may colonize damaged bronchi in patients with mucormycosis.…”

Mucormycoses caused byLichtheimiaspecies

“…Inhalation of asexual spores (sporangiospores) is believed to be the main route of infection with mucormycetes and thus, infection commonly manifests in the respiratory tract . Pulmonary infections with L. corymbifera have been reported in patients with different underlying diseases, including bone marrow and solid organ transplantation, uncontrolled diabetes and leukaemia . The observed symptoms are generally unspecific, such as dyspnoea, pulmonary inflammation and occasionally pleuritis.…”

“…2,3 Pulmonary infections with L. corymbifera have been reported in patients with different underlying diseases, including bone marrow and solid organ transplantation, uncontrolled diabetes and leukaemia. [26][27][28][29][30][31][32] The observed symptoms are generally unspecific, such as dyspnoea, pulmonary inflammation and occasionally pleuritis. Endobronchial bleeding is typical for pulmonary mucormycosis but not specific for Lichtheimia infections.…”

Diagnostic performance of immunohistochemistry for the aspergillosis and mucormycosis

“…However, distinguishing between mucormycosis and aspergillosis is challenging due to the low sensitivity of conventional fungal culture methods and the morphological similarities between several fungal genera that hinder histomorphologic diagnosis . Moreover, non‐culture‐based method such as galactomannan (GM) assay, developed for the diagnosis of invasive aspergillosis, occasionally produced false‐positive results for invasive mucormycosis diagnosis …”

“…4 Moreover, non-culture-based method such as galactomannan (GM) assay, developed for the diagnosis of invasive aspergillosis, occasionally produced false-positive results for invasive mucormycosis diagnosis. 5,6 An early study 7 using monoclonal antibody for immunohistochemistry (IHC) tests on formalin-fixed tissue specimens showed generic identification of Aspergillus. Our previous study 8 also showed that IHC tests on formalin-fixed tissue specimens have sufficiently high sensitivity and specificity for differentiating between aspergillosis and mucormycosis; however, the small number of cases limited the interpretation and application of the results.…”