Disease outbreaks attributed to monsoon flood-induced pathogen exposure are frequently reported, especially in developing cities with poor sanitation. Contamination levels have been monitored in past studies, yet the sources, routes, and extents of contamination are not always clear. We evaluated pollution from municipal wastewater (MWW) discharge and investigated fecal contamination by Escherichia coli (E. coli) in three agricultural fields on the outskirts of Hue City, Vietnam. After E. coli concentration was determined in irrigation water (IRW), MWW, soil, vegetables (VEG), and manure, its dispersion from MWW was tracked using multilocus sequence typing (MLST) and phylogenetic analyses during the wet and dry seasons. IRW was severely contaminated; 94% of the samples were positive with E. coli exceeding the stipulated standards, while VEG contamination was very low in both seasons. The confirmed total number of isolates was comparable between the seasons; however, results from MLST and phylogenetic clustering revealed more links between the sites and samples to MWW during the wet season. The wet season had four mixed clusters of E. coli isolates from multiple locations and samples linked to MWW, while only one mixed cluster also linking MWW to IRW was observed during the dry season. The most prevalent sequence type (ST) complex 10 and two others (40 and 155) have been associated with disease outbreaks, while other STs have links to major pathotypes. Irrigation canals are significant routes for E. coli dispersion through direct links to the urban drainage-infested river. This study clarified the genotype of E. coli in Hue city, and the numerous links between the samples and sites revealed MWW discharge as the source of E. coli contamination that was enhanced by flooding.
Rapid diagnosis of pathogenic bacteria in food is closely related to safety. We modified a Culture-based methods for Salmonella sp. which rapidly identified Salmonella enterica serovars Typhi and Salmonella enterica serovars Paratyphi A from chicken meat samples. The World Health Organization method consists of six steps of the test, sequentially pre-enrichment, selective enrichment, selective diagnostic isolation, pick presumptive Salmonella colonies, biochemical and serological confirmation. Modifications made at three stages of pick presumptive Salmonella colonies, biochemical confirmation and serological confirmation into a single stage of molecular testing to detect genes rfbE and, using tyv and prt primer. In summary, from 120 samples, the modified technique successfully identified 39 (32.5%) Salmonella enterica serovars Typhi and one Salmonella enterica serovars Paratyphi A (0, 83%) compare with 13 (10.8%) and negative result with conventional protocol. The modified were faster and more sensitive than conventional techniques.
Wastewater treatment plants are considered to be reservoirs of antibiotic-resistant bacteria (ARB) outside human and animal bodies. To collect the supporting data, we investigated the existence of ARB in the activated sludge process of municipal wastewater treatment by analyzing communities of sludge bacteria that were incubated with high concentrations of antibiotics (ciprofloxacin or tetracycline) , using the next-generation sequencing technique targeting the 16S rRNA gene. Activated sludge samples were taken from aeration tanks at five municipal wastewater treatment plants (MWWTPs) and one university wastewater treatment plant in Thailand and Japan. Bacterial communities in the sludge samples before incubation were similar among the four MWWTPs in Thailand, but obviously different from those in Japan. The composition of sludge bacteria was markedly changed upon incubation. The concentrations of Enterobacteriaceae species in the sludge samples from two MWWTPs in Thailand increased to 71.3 and 81.4% during incubation with ciprofloxacin, indicating high resistance to this antibiotic. No such increases of specific bacteria families were observed during incubation of the sludge samples with tetracycline, but seven of the top ten dominant families of bacteria were common among the samples from three MWWTPs in Thailand, probably owing to the wide range of sludge bacteria resistant to tetracycline.
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