Investigation of Shiga Toxin-producing Escherichia coli in Different Wastewaters in the Kathmandu Valley, Nepal

摘要

The Kathmandu Valley, Nepal has had numerous microbiological investigations done regarding wastewaters; however, Shiga toxin-producing E. coli (STEC) still lacks studies. This study investigated the incidence, concentration, and pathogenic to nonpathogenic ratio of STEC in wastewaters in the Kathmandu Valley. The genes tested to identify STEC were sfinD, stxl, and stx2. Hospital wastewater (n = 17), wastewater treatment plant (n = 24), sewage treatment plant (n = 4), and not-working wastewater treatment plant (n = 5) samples were collected between September 2014 and April 2018. All the samples were cultured using the Colilert method. The cultured samples were subjected to heat DNA extraction and qPCR for sfmD, stxl, and stx2. Direct qPCR was also done for the wastewater samples. As a result, the incidence of sfmD, stxl, and stx2 using direct qPCR was 90%, 44%, and 56%, respectively, while that by cultured qPCR was 100%, 74%, and 78%, respectively. The concentration of sfmD, stxl, and stx2 was 7-10, 0-7, and 0-7 log copies/ml, respectively, and the pathogenic to nonpathogenic ratio ranged from 0 to 4%. STEC may currently be a problem in the Kathmandu Valley and requires better management and treatment at the plant.