Misidentification of Neosartorya pseudofischeri as Aspergillus fumigatus in a Lung Transplant Patient

Abstract

We present a case of disseminated Neosartorya pseudofischeri infection in a bilateral lung transplant patient with cystic fibrosis. The organism was originally misidentified from respiratory specimens as Aspergillus fumigatus using colonial and microscopic morphology. DNA sequencing subsequently identified the organism correctly as N. pseudofischeri. CASE REPORTA 36-year-old female with cystic fibrosis underwent bilateral lung transplantation in October 2011. Prior to her transplant, she had frequent respiratory exacerbations and her airways were chronically colonized with Aspergillus fumigatus and Pseudomonas aeruginosa. Posttransplant, she was placed on an immunosuppressive regimen of tacrolimus, azathioprine, and prednisone together with antibiotic prophylaxis with trimethoprim-sulfamethoxazole, itraconazole, and valganciclovir. The patient's postoperative course was complicated by tracheobronchitis caused by Pseudomonas aeruginosa and multiple episodes of steroid-responsive acute cellular rejection (International Society for Heart and Lung Transplantation [ISHLT] grade A3), requiring frequent adjustment of her immunosuppressive regimen. In January 2012, she developed areas of focal consolidation in her right lung but bronchoalveolar lavage (BAL) fluid cultures were negative for bacterial and fungal pathogens. She was empirically switched from itraconazole to posaconazole and was given a course of intravenous (i.v.) ceftazidime and oral levofloxacin. In February 2012, the patient was diagnosed with a paratracheal abscess, which was surgically debrided. The intraoperative cultures were positive for multidrug-resistant P. aeruginosa, which was treated with i.v. colistin, ciprofloxacin, and inhaled tobramycin. Subsequent evaluation showed the persistence of the abscess, and the patient was placed on long-term therapy with inhaled tobramycin alternating with colistin, i.v. piperacillin-tazobactam, and ciprofloxacin in July 2012. Spirometry showed a continued decline in lung function. Repeat bronchoscopy by BAL in September 2012 yielded multiple colonies of A. fumigatus, despite the patient being on oral posaconazole prophylaxis.The A. fumigatus isolate was identified using colonial and microscopic morphology. White or greenish-gray fluffy colonies with white edges were observed after 2 to 3 days of growth on Czapek Dox agar (CZA) and inhibitory mold agar (IMA). Using a lactophenol aniline blue-based dye, a tape mount was prepared from each isolate, and columnar heads with phialides covering the upper two-thirds of the vesicle were observed consistent with A. fumigatus. Aspergillus antigen (Platelia Aspergillus enzyme immunoassay; Bio-Rad, Redmond, WA,) tests performed on serum were negative (index Ͻ 0.5). The Aspergillus antigen test performed on the BAL specimen was positive at an index of Ն3.75 in September 2012 but then reverted to negative in October 2012.Liposomal amphotericin B was initiated in addition to posaconazole. Due to worsening renal function, the dosage of amphotericin was lowered and caspofungin ...

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