A checklist of the native fishes of the Dhanu River and adjacent waters at Mithamain Upazila under the Kishoreganj district of Bangladesh is prepared with details on their availability, conservation status, habitat preferences, population trends, and threats. Data were collected monthly by field survey, focus group discussions, and personal interviews by using a semi-structured questionnaire and a pictorial check list of fish species. A total of 91 indigenous fish species of 59 genera belonging to 29 families under 11 orders were documented where 17.6%, 27.5%, 31.9%, and 23.1% species were abundantly available, commonly available, moderately available, and rarely available, respectively. Among those, 24 fish species (26.4%) were under the threatened category (3 critically endangered, 11 endangered, and 10 vulnerable) according to the IUCN Bangladesh. Notably, the globally threatened Cirrhinus cirrhosus, Channa orientalis, and Wallago attu were available in the study area. Fish population trends of 24.2% and 59.3% of the entire fish species were found in decreasing trends at the global and national level, respectively. The leading threats to the fish diversity were indiscriminate overfishing followed by fishing by dewatering of wetlands, the katha fishing method, the use of deprecated fishing gears, etc. Minimizing anthropogenic impacts, enacting fishing laws, installing and managing fish sanctuaries, and raising public awareness can be effective for the conservation of existing fisheries resources.

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Colistin (polymyxin E) is widely used in animal and human medicine and is increasingly used as one of the last-resort antibiotics against Gram-negative bacilli. Due to the increased use of colistin in treating infections caused by multidrug-resistant Gram-negative bacteria, resistance to this antibiotic ought to be monitored. The study was undertaken to elucidate the molecular mechanisms, genetic relationships and phenotype correlations of colistin-resistant isolates. Here, we report the detection of the mcr-1 gene in chicken-associated Salmonella isolates in Bangladesh and its in-silico functional analysis. Out of 100 samples, 82 Salmonella spp. were isolated from chicken specimens (liver, intestine). Phenotypic disc diffusion and minimum inhibitory concentration (MIC) assay using different antimicrobial agents were performed. Salmonella isolates were characterized using PCR methods targeting genus-specific invA and mcr-1 genes with validation for the functional analysis. The majority of the tested Salmonella isolates were found resistant to colistin (92.68%), ciprofloxacin (73.17%), tigecycline (62.20%) and trimethoprim/sulfamethoxazole (60.98%). When screened using PCR, five out of ten Salmonella isolates were found to carry the mcr-1 gene. One isolate was confirmed for Salmonella enterica subsp. enterica serovar Enteritidis, and other four isolates were confirmed for Salmonella enterica subsp. enterica serovar Typhimurium. Sequencing and phylogenetic analysis revealed a divergent evolutionary relationship between the catalytic domain of Neisseria meningitidis lipooligosaccharide phosphoethanolamine transferase A (LptA) and MCR proteins, rendering them resistant to colistin. Three-dimensional homology structural analysis of MCR-1 proteins and molecular docking interactions suggested that MCR-1 and LptA share a similar substrate binding cavity, which could be validated for the functional analysis. The comprehensive molecular and in-silico analyses of the colistin resistance mcr-1 gene of Salmonella spp. of chicken origin in the present study highlight the importance of continued monitoring and surveillance for antimicrobial resistance among pathogens in food chain animals.

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