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Prevalence of filamentous fungi in respiratory tract infected patients with negative acid-fast bacilli smear test in Lagos, Nigeria

D.E. Kumoye
T.O. Samuel
S.A. Adesida
R.F. Peters


Background: The idea of commensal relationship between fungi and infections of the lungs which is a major organ of the respiratory  system has been suggested in the past. Patients with filamentous fungi in their airways often present with sign and symptoms mimicking  tuberculosis.

Aim: This study aims at determining the prevalence of filamentous fungi in acid-fast bacilli smear negative  sputum from patients with respiratory tract infection in Lagos, Nigeria.

Materials and Methods: A total of 360 sputum samples of  patients with respiratory tract infection were collected. These samples were subjected to mycological investigations using microscopy and  culture. The sputum samples were cultured onto Sabouraud Dextrose Agar (SDA) to obtain fungal isolates. The fungal isolates were  tested for their susceptibility using disk diffusion method and the zones of inhibition were interpreted according to the Clinical and  Laboratory Standard Institute (CLSI) guidelines.

Results: The results revealed a prevalence of 75.48% for Aspergillus species in the samples collected. Aspergillus flavus (36.7%), Aspergillus niger (18.7%), Aspergillus fumigatus (1.4%), Aspergillus wentii (17.64%) and Aspergillus  aculeatus (1.04%) were the predominant species of Aspergillus spp. isolated from the sputum samples collected. Other filamentous fungi  isolated include Rhizopus spp. And Penicillium spp. The study showed the higher prevalence of Aspergillus isolates among females  (58.82%) compared to males (41.18%). The age group 30-39 had the highest percentage of occurrence of filamentous fungi (25.3%)  among the different age groups encountered in the study.

Conclusion: The identified fungal species in this study is a proof of mold- causing infection. It can be concluded that the present study helps in establishing that Aspergillus species are responsible for the  respiratory tract infection in the sputum analyzed