Detection of pathogenic Aspergillus species in drinking jar water from Kathmandu Valley, Nepal

Author:

Ushana Shrestha Khwakhali (NP)

Abstract:

Background:
Aspergillus species are ubiquitous filamentous fungi found in many environments. Fungal contamination of water and the occurrence of pathogenic Aspergillus species in the potable drinking water is a public health threat, particularly for immunocompromised individuals. Aspergillus fumigatus is the main causative agent of invasive aspergillosis (IA) and IA can be a waterborne infection. The objectives of the study were to evaluate the quality of unopened drinking jar water (processed drinking water of 20 L capacity) from Kathmandu Valley, Nepal for water safety and detection of pathogenic species of Aspergillus as well as other pathogenic fungi that could pose a potential threat to human health. According to Department of Food Technology and Quality Control (DFTQC), Nepal, total coliform bacteria must not be detected in 100 mL of processed drinking water whereas yeast and mould count should be zero Colony Forming Units (CFU)/mL of packaged/processed drinking water.
Methods:
One hundred and twenty drinking jar water samples were collected from Kathmandu Valley during March 2022 to May 2023. Membrane filtration technique was employed for isolation of fungi from drinking water according to standard methods of American Public Health Association (2017). For each sample, 100 mL of water was filtered through a sterile membrane filter with 0.45 µm pore size and 47 mm diameter. The membranes were transferred on Sabouraud΄s dextrose agar (SDA) plates with chloramphenicol (50 mg/L) and incubated at 37°C for up to 7 days and examined daily for any visible growth of pathogenic fungal species present in water. The number of colonies was counted and expressed as CFU/100 mL of water sample. The isolates of pathogenic Aspergillus species as well as other pathogenic fungi were identified to species complex level by macroscopic and microscopic morphological characteristics. A Gram stain, germ-tube test and biochemical tests were also performed for identification of yeasts.
Results:
Pathogenic fungi were detected in 94.2% of drinking jar water samples from Kathmandu Valley. Of total fungal isolates from water, 4.3% were filamentous fungi and 95.6% were yeasts with Aspergillus species, the most frequent filamentous fungi contaminating 27.8% of drinking jar water. Total Aspergillus count ranged from 1 to 8 CFU/100 mL, with an average of 2 cfu/100 mL. The predominant genera of filamentous fungi identified were Aspergillus (2.4%) while Fusarium (0.6%), Penicillium (0.2%), Rhizopus (0.3%), Mucor (0.1%), Alternaria (0.1%) and Trichoderma (0.1%) were also isolated. Among yeasts, the genera Rhodotorula (26.9%) and Candida (34.9%) were detected. Pathogenic Aspergillus species recovered from drinking jar water was A. fumigatus (9.5%), A. flavus (23.8%), A. niger (61.9%) and other Aspergilli (4.8%).
Conclusions:
In Kathmandu Valley, the predominant pathogenic filamentous fungi in drinking jar water was Aspergillus species. The presence of pathogenic fungi in drinking jar water reveals the poor quality of drinking water and indicates the health risks to consumers, mainly to immunocompromised patients.

Abstract Number: 20

Conference Year: 2024

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