Prevalence and antimicrobial resistance of major foodborne pathogens isolated from pangas and tilapia fish sold in retail markets of Dhaka city, Bangladesh.

Fish sold at retail markets are often contaminated with harmful bacterial pathogens, posing significant health risks. Despite the growing aquaculture industry in Bangladesh to meet high demand, little attention has been paid to ensuring the safety of fish. The objective of this study was to evaluate the microbiological quality of tilapia and pangas fish sold in retail markets across Dhaka city, Bangladesh. Specifically, the study aimed to compare the quality of fish from traditional wet markets and modern supermarkets, as well as fish samples collected during morning and evening hours. A total of 500 raw cut-fish samples (250 tilapia and 250 pangas) were collected at the point of sale from 32 wet markets and 25 supermarkets. All samples were tested for Escherichia coli, extended-spectrum ß-lactamase-producing E. coli (ESBL-Ec), along with the foodborne pathogens Salmonella, Shigella, Vibrio, and Cryptosporidium spp. Bacterial isolates were characterized using antibiotic susceptibility tests (AST) and the presence of common virulence and antibiotic-resistant genes. Fish samples from retail markets had higher prevalence of tested bacteria including E. coli (92 %), V. cholerae (62 %), ESBL-Ec (48 %), and Salmonella spp. (24 %). There was a significant difference in the prevalence of E. coli (97 % vs. 71 %), ESBL-Ec (58 % vs. 8 %) and Salmonella spp. (28 % vs. 8 %) on the wet market samples compared to supermarket samples (p < 0.005). The mean concentration of E. coli on fish from the wet market was 3.0 ± 0.9 log10 CFU/g, while that from supermarkets was 1.6 ± 0.9 log10 CFU/g. The mean concentration of ESBL-Ec in fish from wet markets and supermarkets were 2.3 ± 0.8 log10 CFU/g and 1.6 ± 0.5 log10 CFU/g, respectively. AST revealed that 46 % of E. coli isolates were multi-drug resistant (MDR), while 4 %, 2 % and 5 % of E. coli, Salmonella spp. and Vibrio spp. isolates, respectively, were resistant to carbapenems. At least 3 % of total E. coli isolates were found to be diarrheagenic, while 40 % of Salmonella isolates harbored pathogenic genes (stn, bcfC, ssaQ, avrA and sodC1), and none of the V. cholerae isolates harbored ctxA and tcpA. Our research shows that raw-cut fish samples from retail markets are contaminated with pathogenic and antibiotic-resistant bacteria, which could be a significant food safety concern. Public health interventions should be implemented to improve food safety and hygiene practices in the retail fish markets.

Correction: Effects of chronic exposure to arsenic on the fecal carriage of antibiotic-resistant Escherichia coli among people in rural Bangladesh.

[This corrects the article DOI: 10.1371/journal.ppat.1010952.].

Effects of chronic exposure to arsenic on the fecal carriage of antibiotic-resistant Escherichia coli among people in rural Bangladesh.

Antibiotic resistance is a leading cause of hospitalization and death worldwide. Heavy metals such as arsenic have been shown to drive co-selection of antibiotic resistance, suggesting arsenic-contaminated drinking water is a risk factor for antibiotic resistance carriage. This study aimed to determine the prevalence and abundance of antibiotic-resistant Escherichia coli (AR-Ec) among people and drinking water in high (Hajiganj, >100 µg/L) and low arsenic-contaminated (Matlab, <20 µg/L) areas in Bangladesh. Drinking water and stool from mothers and their children (<1 year) were collected from 50 households per area. AR-Ec was detected via selective culture plating and isolates were tested for antibiotic resistance, arsenic resistance, and diarrheagenic genes by PCR. Whole-genome sequencing (WGS) analysis was done for 30 E. coli isolates from 10 households. Prevalence of AR-Ec was significantly higher in water in Hajiganj (48%) compared to water in Matlab (22%, p <0.05) and among children in Hajiganj (94%) compared to children in Matlab (76%, p <0.05), but not among mothers. A significantly higher proportion of E. coli isolates from Hajiganj were multidrug-resistant (83%) compared to isolates from Matlab (71%, p <0.05). Co-resistance to arsenic and multiple antibiotics (MAR index >0.2) was observed in a higher proportion of water (78%) and child stool (100%) isolates in Hajiganj than in water (57%) and children (89%) in Matlab (p <0.05). The odds of arsenic-resistant bacteria being resistant to third-generation cephalosporin antibiotics were higher compared to arsenic-sensitive bacteria (odds ratios, OR 1.2-7.0, p <0.01). WGS-based phylogenetic analysis of E. coli isolates did not reveal any clustering based on arsenic exposure and no significant difference in resistome was found among the isolates between the two areas. The positive association detected between arsenic exposure and antibiotic resistance carriage among children in arsenic-affected areas in Bangladesh is an important public health concern that warrants redoubling efforts to reduce arsenic exposure.

Antimicrobial resistance, virulence factors and genetic diversity of Escherichia coli isolates from household water supply in Dhaka, Bangladesh.

BACKGROUND: Unsafe water supplies continue to raise public health concerns, especially in urban areas in low resource countries. To understand the extent of public health risk attributed to supply water in Dhaka city, Bangladesh, Escherichia coli isolated from tap water samples collected from different locations of the city were characterized for their antibiotic resistance, pathogenic properties and genetic diversity. METHODOLOGY/PRINCIPAL FINDINGS: A total of 233 E. coli isolates obtained from 175 tap water samples were analysed for susceptibility to 16 different antibiotics and for the presence of genes associated with virulence and antibiotic resistance. Nearly 36% (n = 84) of the isolates were multi-drug(≥ 3 classes of antibiotics) resistant (MDR) and 26% (n = 22) of these were positive for extended spectrum ß-lactamase (ESBL). Of the 22 ESBL-producers, 20 were positive for bla CTX-M-15, 7 for bla OXA-1-group (all had bla OXA-47) and 2 for bla CMY-2. Quinolone resistance genes, qnrS and qnrB were detected in 6 and 2 isolates, respectively. Around 7% (n = 16) of the isolates carried virulence gene(s) characteristic of pathogenic E. coli; 11 of these contained lt and/or st and thus belonged to enterotoxigenic E. coli and 5 contained bfp and eae and thus belonged to enteropathogenic E. coli. All MDR isolates carried multiple plasmids (2 to 8) of varying sizes ranging from 1.2 to >120 MDa. Ampicillin and ceftriaxone resistance were co-transferred in conjugative plasmids of 70 to 100 MDa in size, while ampicillin, trimethoprim-sulfamethoxazole and tetracycline resistance were co-transferred in conjugative plasmids of 50 to 90 MDa. Pulsed-field gel electrophoresis analysis revealed diverse genetic fingerprints of pathogenic isolates. SIGNIFICANCE: Multi-drug resistant E. coli are wide spread in public water supply in Dhaka city, Bangladesh. Transmission of resistant bacteria and plasmids through supply water pose serious threats to public health in urban areas.

Occurrence and characterization of multidrug-resistant New Delhi metallo-ß-lactamase-1-producing bacteria isolated between 2003 and 2010 in Bangladesh.

The purpose of this study was to screen for reduced susceptibility against imipenem and the presence of the New Delhi metallo-ß-lactamase-1 (NDM-1) gene in a collection of Enterobacteriaceae (Escherichia coli, Shigella spp. and Klebsiella pneumoniae) from different surveillance studies between 2003 and 2010 at the International Centre for Diarrhoeal Disease Research, Bangladesh. None of the E. coli (n = 1789) and Shigella spp. (n = 90) isolated between 2009 and 2010 from stool samples was resistant or had intermediate susceptibility to imipenem. Among 127 extended-spectrum ß-lactamase-producing strains isolated during 2003-2009, three Klebsiella pneumoniae isolates (2.4 %) were resistant to imipenem and were positive for bla(NDM-1). All these NDM-1-producing strains were isolated in 2008 and were resistant to all antibiotics tested except for tigecycline and colistin. All three isolates were positive for bla(OXA-1) group, bla(CTX-M-1) group (bla(CTX-M-15)) and bla(SHV) genes, whilst two isolates were positive for 16S rRNA methylase (armA) and qnr (qnrB) genes. One isolate was positive for the bla(CMY) gene and one for the rmtB gene. The bla(NDM-1) gene was located on a conjugative plasmid of ~23-24 MDa. The PFGE patterns of the isolates were different from each other. This study highlights the occurrence of NDM-1-producing organisms in Bangladesh in 2008. The clonal diversity of the isolates and the transferability of bla(NDM-1) plasmids suggest a wider distribution of NDM-1-producing bacteria in Bangladesh.