Invasive forms of Candida and Aspergillus in sputum samples of pulmonary tuberculosis patients attending the tuberculosis reference laboratory in Ghaemshahr, Northern Iran: An analysis of samples collected during the past 10years.

Objective/background: Tuberculosis (TB) continues to be a major public health problem worldwide. This is especially true in Northern Iran, which has high TB prevalence. The chronic nature of this disease is further exacerbated if it is accompanied by fungal infection, which usually remains undiagnosed and thus untreated. Thus, mycotic infections add fatal dimensions to pulmonary TB. Our objective was to determine the prevalence of invasive forms of fungal elements in sputum samples collected from patients with pulmonary TB at a reference laboratory in Ghaemshahr, Northern Iran, during the past 10years.

Methods: In this retrospective study, sputum samples collected from 430 patients were examined. Pulmonary TB in patients was confirmed in our laboratory, and samples obtained during the period from March 2006 to February 2016 were analyzed. The sputum samples were subjected to biological (bacterial) staining (Ziehl-Neelsen and fluorochrome) and mycological investigation using KOH Calcofluor White (Sigma-Aldrich, India) by fluorescent microscopy and fungal culture on Sabouraud dextrose agar (Sigma-Aldrich, India) and CHROMagar (Paris, France).

Results: Invasive forms of fungal pathogens were observed as co-infection with Mycobacterium tuberculosis in 28/430 cases (6.51%). The frequency of Aspergillus, both branching and dichotomous infection, accounted for 3.72% (16/430): Aspergillus flavus, 1.63%; Aspergillus fumigatus, 1.16%; Aspergillus niger, 0.69%; and Aspergillus oryzae, 0.23%, respectively. Blastoconidia and pseudohyphae forms of yeast were observed as co-infection with M. tuberculosis in 2.79% (12/430) of the cases: Candida albicans, 1.86%; Candida krusei, 0.46%; and other Candida species, 0.46%, respectively.

Conclusion: Northern Iran is a critical region in the TB world and multidrug-resistant TB is a serious problem in this region. Although it is believed that there exists a commensal relationship between fungus and TB infections, the invasive forms of fungal pathogens and their co-infection can be caused by increasing disability and failure of treatment. Diagnosis of secondary or co-existing fungal infections in TB is most important for reducing the mortality and morbidity of these patients.