Distribution of filamentous fungi causing invasive fungal disease at the haematological unit, Hospital de Clínicas de Porto Alegre, Brazil

ORIGINAL ARTICLE

Distribution of filamentous fungi causing invasive fungal disease at the haematological unit, Hospital de Clínicas de Porto Alegre, Brazil

Valério Rodrigues Aquino^I,II; Emanuelle Bergonsi Verçosa^III; Gustavo Falhauber^IV; Luciano Werle Lunardi^IV; Lucia Silla^III,V; Alessandro Comarú Pasqualotto^II,VI

^IMicrobiology Unit Section, Clinical Patology Services, Hospital de Clínicas de Porto Alegre (HCPA), Porto Alegre, Brazil

^IIPost-Graduation Program in Pulmonary Sciences, Federal University of Rio Grande do Sul (UFRGS), Porto Alegre, Brazil

^IIIMedical School, UFRGS, Porto Alegre, Brazil

^IVInternal Medicine Department, HCPA, Porto Alegre, Brazil

^VClinical Haematology Unit, HCPA, Porto Alegre, Brazil

^VIMolecular Biology Laboratory, Santa Casa Complexo Hospitalar, Porto Alegre, Brazil

^{Correspondence to}

ABSTRACT

Very limited data are available in the literature to elucidate the aetiology of invasive mould infections in Latin America. Here we report that Aspergillus species caused only half of such cases in a cohort study conducted over 21 months in a university hospital in Porto Alegre, Southern Brazil. Fusarium spp. were the second most prevalent moulds (20.7%), followed by Zygomycetes (13.8%). The importance of obtaining local epidemiological data for adequately guiding empirical antifungal therapy is reinforced.

Keywords: Aspergillus, Fusarium, mold infections, epidemiology, zygomycosis.

INTRODUCTION

Several authors have reported an increasing incidence of invasive fungal diseases (IFDs), especially in patients with haematological malignancies and in those undergoing haematological stem cell transplantation (HSCT).^1-6 Since these are difficult to diagnose conditions, with an associated high mortality rate, empirical antifungal therapy is widely used for patients with a suspected IFD. However, the effectiveness of any empirical treatment depends on knowledge of causative agents. Candida species are by far the most common fungi causing IFDs in humans.⁷ However, many centres over the past decade have reported a marked reduction in the incidence of Candida bloodstream infections as a result of fluconazole prophylaxis.⁸ In contrast, there has been an increment in the incidence of invasive mould infections,^9,10 particularly due to species of Aspergillus, Fusarium, and Zygomycetes.^2,3,9,10

The purpose of this study was to describe the fungal agents isolated from patients admmitted to a haematological unit in Brazil. All cases included in this cohort occurred before the installation of High-Efficiency Particulate Air (HEPA) filtration in the haematological unit.

MATERIAL AND METHODS

This was a retrospective cohort study conducted to assess the distribution of filamentous fungi causing IFD in patients with haematological malignancies and those who had undergone HSCT. The study was performed at the Hospital de Clínicas de Porto Alegre (HCPA), a 750-bed tertiary-care university hospital located in Porto Alegre, Southern Brazil. The files from the Mycology Laboratory were hand searched from February 2004 to December 2006, in an attempt to select for cases of IFD caused by moulds. Medical records from these patients were reviewed. Patients with endemic mycoses or yeast infections were not included in the study, as well as those in whom the agent was not identified in culture. All IFDs were classified according to the revised EORTC/MSG consensus criteria,¹¹ and only cases of proven/probable infections were studied.

Standard mycological procedures were performed for the analysis of clinical samples, including microscopy and culture. Descriptive statistics were used to summarise the data. Statistical analysis was performed with SPSS 16.0. Normally distributed quantitative data were analysed with Student's t-test, while the non-parametric Mann-Whitney test was used for variables with asymmetric distribution. Categorical data were evaluated with chi-square or Fisher's exact test. Survival analyses were performed 6 weeks after IFD was diagnosed using Kaplan-Meyer analysis and the log rank test. P-values of < 0.05 were considered statistically significant. This article is part of a more comprehensive project submitted to and approved by the Ethics Committee of Hospital de Clínicas de Porto Alegre (GPPG 07068).

During the study period, HSCT patients received antifungal prophylaxis with fluconazole at 200 mg daily. Patients on high doses of chemotherapy for acute myeloid leukaemia, acute lymphoblastic leukaemia, or high risk myelodisplasic syndrome received itraconazole capsules (200 mg once a day with an acid drink).

RESULTS

A total of 29 patients with IFD caused by moulds were identified. Patients were mostly female (n = 15) and mean age was 31.7 year-old. Sixteen patients (55.2%) had been submitted to HSCT, including allogeneic (n = 12; 41.4%) and autologous (n = 4; 13.8%) recipients. Only 24.1% (n = 7) of patients were not neutropenic at the time of IFD diagnosis.

As shown in Table 1, only 58.6% of cases were caused by Aspergillus species (n = 17). Fusarium spp. were the second most prevalent filamentous fungi (n = 6; 20.7%), followed by Zygomycetes (n = 4; 13.8%). Other fungi included species of Curvularia and Trichoderma (one case each; 3.4%). Most fungal infections were classified as proven IFD (n = 20, 69.0%) and 9 cases were probable (31.0%). Most IFDs occurred in the context of febrile neutropenia (n = 22; 75.9%). Clinical samples were paranasal sinus biopsy (n = 15; 51.7%), respiratory tract specimen (bronchoalveolar lavage/sputum) (n = 9; 31%), blood culture (n = 2; 6.9%), skin biopsy (n = 2; 6.9%), and lung biopsy (n = 1; 3.4%). Aspergillus species were recovered in 60% of cases of invasive fungal sinusitis (9/15), followed in frequency by Zygomycetes (n = 3; 20%), Fusarium species (n = 2; 13.3%), and Curvularia spp. (n = 1; 6.7%). Surgical debridement of paranasal sinuses was performed for most patients with invasive fungal rhinosinusitis (93.3%).

Overall mortality 6 weeks after the diagnosis of IFD was 41.9%. Similar mortality rates were observed for patients with invasive aspergillosis (35.3%), fusariosis (50.0%), and zygomycosis (50.0%) (p = 0.283). Mortality was 50.6% for patients with proven IFD and 21.4% for those with probable IFD (p = 0.127).

DISCUSSION

The medical importance of IFDs has markedly increased in the last decades. The causes for that are multifactorial. In special, there has been an increment in the proportion of individuals at risk as a result of immunosuppression, particularly amongst haematological patients. In addition, aggressive medical interventions have allowed critically ill patients to survive longer, increasing their overall risk to acquire fungal infections.^5,12

In the present study, we showed the distribution of filamentous fungi causing invasive fungal diseases at the haematology unit of HCPA, a reference medical centre in Southern Brazil. Roughly, half of infections were caused by Aspergillus species, especially A. fumigatus and A. flavus (the latter usually in association with invasive fungal rhinosinusitis). A large proportion (41.4%) of IFDs was associated with fungi other than Aspergilli. Fusarium species caused 20.7% of invasive mould infections, followed in frequency by Zygomycetes (13.8%). Fusarium species are known to cause a broad spectrum of infections in humans, including superficial, locally invasive and disseminated infections, particularly in immunocompromised patients with prolonged neutropenia.¹³ In addition, Fusarium spp. are highly resistant to antifungal drugs.¹⁴ Zygomycosis, which seems to be an emerging problem for many medical centres,^4,6 is also a very difficult to treat infection, usually requiring a combination of surgical debridement and high dose treatment with amphotericin B. Because voriconazole is inactive against the Zygomycetes, the emergence of these fungi might complicate voriconazole use in the empirical setting.

The emergence of mould infections have been documented in several studies. Similarly to our findings, Neofytos et al.⁵ documented that most (59.2%) IFDs in HSCT recipients were caused by Aspergillus species, followed in frequency by Candida spp. (24.8%), Zygomycetes (7.2%), and other moulds (6.8%). In the study by Horn et al.²⁰Aspergillus spp. caused 14.8% of all IFDs in a cohort of 1710 patients enrolled in 22 sites in the United States (PATH Alliance study). A small number of IFDs caused by other fungi was also observed, including species of Paecilomyces, Scedosporium, Alternaria, Acremonium, Fusarium, and Zygomycetes. Garcia-Vidal et al.²¹ observed that Aspergillus species caused 88% of invasive mould infections following allogenic HSCT. Several authors have stressed that IFDs caused by different moulds may require specific strategies in terms of diagnosis, treatment, and prophylaxis. Obtaining local epidemiological data is therefore a crucial step in organising health care units and planning therapeutic interventions.

Although numerous studies in the last 10 years have documented the epidemiology of Candidaemia in Brazil,^15-17 little information is available on invasive aspergillosis (IA) or other invasive mould diseases. A previous study performed in Porto Alegre demonstrated that 82% of cases of IA were not diagnosed before autopsy.¹⁸ This reality seems similar in several other countries: it is estimated that 20-80% of IA cases are not diagnosed before death, frequently because of lack of clinical suspicion.^9,19 Since the frequency of autopsy is at a decrease in the western world, physicians risk ending up with an incorrect perception that invasive mould infections rarely occur in the clinical practice.

To the best of our knowledge, only two cohort studies have so far documented the epidemiology of IFD in Brazil. The distribution of Aspergillus species causing IFD at Hospital de Clínicas da Universidade Federal do Paraná - another referral centre for allogeneic HSCT in Southern Brazil - was recently published.¹² A total of 24 cases of proven/probable IA were detected over a 10-year period in that investigation, including 11 proven IA cases. The reported incidence of 3% was probably underestimated, since galactomannan testing was not available at the time of the study. Overall mortality was 70% after 30 days of follow-up. Non-Aspergillus moulds were recovered from 163 additional patients but no details were provided. Partial results from a multicenter survey study performed in Brazil were recently presented in abstract form.²² Considering patients with proven/probable infections only, the incidence of IFD in HSCT recipients and patients with acute myeloid leukaemia and myelodysplastic syndrome was 6.7% in that investigation. Twenty-five patients (out of 460) had proven IFD. Also, this may also be underestimated, since serum galactomannan testing was not routinely performed. Similarly to our findings, fusariosis was the second leading cause of invasive mould disease, being more common than zygomycosis.

One remarkable finding of our study was the elevated proportion of proven IFD cases (69.0%), in comparison to probable cases. This was achieved due to an aggressive policy of computed tomography imaging of the paranasal sinususes in patients with febrile neutropenia, which frequently triggers the performance of paranasal sinuses biopsies. Accordingly, approximately 50% of patients in the current series had invasive fungal rhinosinusitis. The diagnosis of these conditions is actually dependent on demonstration of tissue invasion by fungi, and the paranasal sinuses are more easily reached for invasive medical procedures than the lungs.

CONCLUSION

In conclusion, here we demonstrated that 41.4% of invasive mould infections were associated with fungi other than those belonging to the Aspergillus genus. Fusarium spp. was the second most frequently recovered fungi. Of concern is the fact that Zygomycetes were the second aetiology of invasive rhinosinusitis in this study. Epidemiological surveillance is necessary in order to monitor the dynamics of these infections.

Submitted on: 11/16/2009

Approved on: 04/19/2010

We declare no conflict of interest.

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Publication Dates

• Publication in this collection
  03 Sept 2010
• Date of issue
  June 2010

History

• Accepted
  19 Apr 2009
• Received
  16 Nov 2009