The basidiomycetous yeast Trichosporon may cause severe lung exacerbation in cystic fibrosis patients – clinical analysis of Trichosporonpositive patients in a Munich cohort

Trichosporon species (T. spp.) belong to the genus of basidiomycetous yeast and are widely distributed in nature. They are found in soil and water and are known to colonize skin and gastrointestinal tract of humans [1, 2]. Numerous Trichosporon spp. have been characterized [3], while only a few cause human disease including T. asahii, T. inkin, T. asteroides, T. cutaneum, T. mucoides, T. ovoides (formerly subsumed as a single species: T. beigelii[4, 5]) and two more recently described species: T. louberi and japonicum[6]. The most relevant disease entities caused by Trichosporon spp. are white piedra, a mycosis of the hair (T. inkin, T. ovoides) [4], summer-type hypersensitivity pneumonitis in Japan (T. asahii, T. mucoides and T. dermatis) [4] and invasive trichosporonosis (local and disseminated; most often caused by T. asahii) [4]. Risk factors for invasive trichosporonosis are immunosuppression, including prolonged corticosteroid treatment, impaired granulocyte function, neutropenia, malignancies, especially leukemia [7], renal disease, extensive burns and HIV [7, 8]. Invasive Trichosporon infections are the second most common yeast fungaemia in humans [4, 9], especially in patients with haematological malignancies [10]. Symptoms of invasive trichosporonosis range from pulmonary infiltrates, skin lesions and renal failure to local organ infections, such as hepatitis [4].

The significance of Trichosporon spp. for CF patients has so far not been widely recognized. Only three case reports are available in literature: One 11-year old CF patient suffered from a non-aspergillus allergic bronchopulmonary mycosis due to T. beigelii and recovered within 2 months under intensive steroid and antifungal therapy [11]. One 20-year old, male CF patient died within a few days from admission due to a fulminant pneumonia with T. mycotoxinivorans[12] and one 35-year old CF patient died due to a disseminated fatal infection with T. mycotoxinivorans 29 days after lung transplantation [13]. Aim of this study was to investigate the detection rate of Trichosporon spp. in a German CF cohort and to describe the clinical course of patients positive for Trichosporon.

All respiratory samples of 360 CF patients (mean age 2010 18.11 years, range 0 – 52.4; mean FEV1 81.4% pred; range 16 – 136% pred; 12.5% with associated diabetes mellitus) who attended the CF Center at the Children’s University Hospital in Munich were studied between January 1st, 2003 and December 31st, 2010 for the presence of bacterial and/or fungal pathogens. Other detected fungi included Aspergillus species (approximately 16% of the cohort, >90% Aspergillus fumigatus) and Candida species (approximately 40% of the cohort, >90% Candida albicans). 15% of the patients exhibited intermittent Pseudomonas aeruginosa colonization, 48% chronic colonization. Patient visits took place on average every three months, if indicated more often. At each visit, sputum samples or throat smears were taken and the patients were investigated clinically; routine laboratory examinations including inflammatory parameters and lung-function tests were performed. On average 4 respiratory samples/patient/year were analysed, approximately 70% of the samples were throat swabs, 30% expectorated sputum. The clinical course of Trichosporon positive patients was analysed retrospectively based on forced expiratory volume in one second (FEV1,%pred), body mass index (BMI) and the inflammatory markers CRP (mg/l) and immunoglobulin G (IgG, g/l), the latter known to be associated with chronic inflammation and inversely correlated with lung function and long-term prognosis [14, 15]. The erythrocyte sedimentation rate 1 h (ESR, mm) was also recorded; however, insufficient data was available for analysis. Decline in FEV1 was defined as a drop of the yearly mean FEV1 of >1%pred/year from first detection to the end of the observation period of the individual patient, based on the average yearly drop of FEV1 values of 1% in large CF registries [16]. Any change in BMI was recorded, increase in CRP was defined as an increase by >5 mg/l and an increase in IgG was defined as an increase by >3 g/l from first detection to the end of the observation period. Informed consent was obtained from all participants and the study was approved by the institutional review board of the University of Munich.

Trichosporon spp. were detected in 8 of 360 patients (i.e. 2.2%; 3 male; mean age: 21.8 years, range: 8 – 41.1; Table 1). Two Trichosporon spp. were specified by MALDI-TOF MS and by DNA sequencing: T. mycotoxinivorans and T. inkin. T. asahii was identified by microscopy, biochemical testing and MALDI-TOF MS. All but one patient were colonized with further CF typical microorganisms at first detection as depicted in Table 1. 5 patients had a history of ABPA 0–5 years prior to first detection. 5 patients had a history of treatment with nebulized steroids and/or steroid inhalers, 3 of whom had received additional systemic steroid treatment, one patient had received systemic steroid treatment only. 2 patients had CF associated diabetes at first detection. No patient underwent lung transplantation. All 8 patients had a dF508 mutation, 3 patients an additional stop mutation (2 patients R553X and one patient S466X) (Table 1).

The relevance of fungal colonization in CF patients has only recently been recognized [22]. Colonization with C. albicans and A. fumigatus –also in non-ABPA patients- has for example been associated with a decline in lung function and a negative effect on the clinical outcome [23, 24]. A. fumigatus in particular was demonstrated to have a pro-inflammatory effect on the CF epithelium [25]. However, the available studies are limited by important confounders, such as the lack of standardized detection methods or co-infection with other microorganisms. The contribution of fungi to CF lung disease thus remains controversial as does the indication to a non-risk free antifungal therapy.

The prevalence and the relevance of Trichosporon spp. in CF has to date not been investigated. In the present study Trichosporon spp. was found in respiratory samples of 2.2% of the cohort over an eight year period. Colonization rates of Trichosporon spp. in non-CF patients range between 0.8% in throat cultures and 3.1% in stool cultures of patients in a large Veterans hospital [26] and 3.7% in stool, skin or urine of 317 immunosuppressed hosts [27].

Risk factors for colonization and/or infection with Trichosporon in CF are also unknown. Invasive trichosporonosis in non-CF patients has been associated with mucosal disruption and general immune dysfunction due to HIV or malignancies [28], however, the exact pathophysiology of Trichosporon infections is unknown. It is possible that mucosal disruption in CF also predisposes for Trichosporon colonization. Our data suggest that age, prior systemic or inhaled steroid treatment, ABPA and possibly CF associated diabetes might predispose for Trichosporon colonization. 3 of 8 patients carried a stop mutation in addition to dF508, which is higher than the general frequency of stop mutations in German CF population (1.8% for R553X; <1% for S466X) [29]. Our data further indicate that longer Trichosporon detection periods may be associated with a decline in lung function and BMI, and increased inflammation. Chronic airway colonization with Trichosporon may harbour the risk of clinically relevant infection leading to unstable lung disease. Further studies will have to corroborate these findings.

Up to now three case reports of CF patients have demonstrated the potential of exacerbation and in two cases of a fatal, disseminated infection due to Trichosporon spp.[11‐13]. Here we add another patient (3) whose course was significantly affected by infection with T. inkin. This conclusion is based on the unexplained failure of intensive antibacterial and supportive therapy and the clear improvement and stabilization of the clinical status after the initiation of antifugal therapy. Repeated detection of Trichosporon spp. may indicate CF patients at risk for deterioration; preemptive treatment may be considered.