Microbial Assessment of Solid Waste and Bioaerosol Associated with Open Dumping Sites of the Kathmandu City, Nepal

Abstract

The study aims to isolate and identify bacteria and fungi (mold) present in solid waste and its associated bioaerosol in the Kathmandu city. A total of 10 samples; 5 different solid waste samples and 5 different bioaerosol samples, collected from 5 open dumping sites in the Kathmandu city, were transported to the microbiology laboratory of St. Xavier’s College for processing. Standard microbiological procedures were followed for the identification of isolates. The Kirby-Bauer disk diffusion method was used to determine the antibiotic susceptibility of bacterial isolates following CLSI 2020 standards. In the collected solid waste samples, the bacterial colony count ranged from 1.27 × 108 to 2.8 × 108 CFU/ml, whereas the fungi colony count ranged from 1 × 105 to 4 × 105 CFU/ml. Bacterial colony counts from bioaerosol samples ranged from 116 to >300 CFU/90mm/15 minutes, whereas fungi colony counts were between 2 and 6 CFU/90mm/15 minutes. Out of 48 bacteria and 34 molds identified, Bacillus spp. (27%) and Aspergillus niger (29%) were found to be predominant than other isolates. Citrobacter spp., Salmonella spp., and Escherichia coli isolated from solid waste samples of dump site S3 showed maximum resistance to the different antibiotics used. The common microbial isolates from solid waste samples and bioaerosol samples included 7 different bacteria and 4 different molds. The presence of antibiotic-resistant bacteria and pathogenic fungi in waste dump sites pose public health-related risks.