Vibrio cholerae serogroup O1 is responsible for epidemic and pandemic cholera and remains a global public health threat. This organism has been well established as a resident flora of the aquatic environment that alters its phenotypic and genotypic attributes for better adaptation to the environment. To reveal the diversity of clinical isolates of V. cholerae O1 in the Bay of Bengal, we performed whole-genome sequencing of isolates from Kolkata, India, and Dhaka, Bangladesh, collected between 2009 and 2016. Comparison with global isolates by phylogenetic analysis placed the current isolates in two Asian lineages, with lineages 1 and 2 predominant in Dhaka and Kolkata, respectively. Each lineage possessed different genetic traits in the cholera toxin B subunit gene, Vibrio seventh pandemic island II, integrative and conjugative element, and antibiotic-resistant genes. Thus, although recent global transmission of V. cholerae O1 from South Asia has been attributed only to isolates of lineage 2, another distinct lineage exists in Bengal. IMPORTANCE Cholera continues to be a global concern, as large epidemics have occurred recently in Haiti, Yemen, and countries of sub-Saharan Africa. A single lineage of Vibrio cholerae O1 has been considered to be introduced into these regions from South Asia and to cause the spread of cholera. Using genomic epidemiology, we showed that two distinct lineages exist in Bengal, one of which is linked to the global lineage. The other lineage was found only in Iran, Iraq, and countries in Asia and differed from the global lineage regarding cholera toxin variant and drug resistance profile. Therefore, the potential transmission of this lineage to other regions would likely cause worldwide cholera spread and may result in this lineage replacing the current global lineage.

Vibrio cholerae O1 biotype El Tor (ET), causing the seventh cholera pandemic, was recently replaced in Bangladesh by an altered ET possessing ctxB of the Classical (CL) biotype, which caused the first six cholera pandemics. In the present study, V. cholerae O1 strains associated with endemic cholera in Dhaka between 2006 and 2011 were analysed for major phenotypic and genetic characteristics. Of 54 representative V. cholerae isolates tested, all were phenotypically ET and showed uniform resistance to trimethoprim/sulfamethoxazole (SXT) and furazolidone (FR). Resistance to tetracycline (TE) and erythromycin (E) showed temporal fluctuation, varying from year to year, while all isolates were susceptible to gentamicin (CN) and ciprofloxacin (CIP). Yearwise data revealed erythromycin resistance to be 33.3 % in 2006 and 11 % in 2011, while tetracycline resistance accounted for 33, 78, 0, 100 and 27 %

Shiga toxin-producing Escherichia coli (STEC) and enterotoxigenic E. coli (ETEC) are important causes of diarrhea in humans and animals worldwide. Although ruminant animals are the main source of STEC, diarrhea due to this pathotype is very low in Bangladesh where ETEC remains the predominant group associated with childhood diarrhea. In the present study, E. coli strains (n = 35) isolated from Bangladesh livestock (goats, sheep, and cattle) and poultry (chicken and ducks) were analyzed for the presence of major virulence factors, such as Shiga toxins (STX-1 and STX-2), heat-labile toxin, and heat-stable toxins (STa and STb). Multiplex polymerase chain reaction results revealed 23 (66%) E. coli strains to be virulent possessing either sta (n = 5), stx (stx1, n = 8; stx2, n = 2), or both (n = 8) genes in varying combinations. Thirty-four percent (8/23) of strains from livestock were hybrid type that carried both stx (either stx1 or stx2) and ETEC-specific enterotoxin gene sta. Serotyping results revealed that the ETEC strains belonged to five serotypes, namely O36:H5, O174:H−, O152:H8, O109:H51, and O8:H21, while the STEC-producing strains belonged to serotypes O76:H19 (n = 3), O43:H2 (n = 2), O87:H16 (n = 2), OR:H2 (n = 1), O110:H16 (n = 1), and O152:H8 (n = 1). The STEC–ETEC hybrid strains belonged to serotypes O76:H19 (n = 3), O43:H2 (n = 2), O87:H16, OR:H2, and O152:H8. Forty percent (2/5) of the ETEC and 20% (2/10) of the STEC strains were multidrug resistant with the highest drug resistance (50%) being found in the hybrid strains. Molecular fingerprinting determined by pulsed-field gel electrophoresis and cluster analyses by dendrogram revealed that, genetically, STEC–ETEC hybrid strains were highly heterogeneous. Multidrug-resistant E. coli STEC–ETEC hybrid strains in domesticated animals pose a public health threat for humans in Bangladesh.

Of the 200+ serogroups of Vibrio cholerae, only O1 or O139 strains are reported to cause cholera, and mostly in endemic regions. Cholera outbreaks elsewhere are considered to be via importation of pathogenic strains. Using established animal models, we show that diverse V. cholerae strains indigenous to a non-endemic environment (Sydney, Australia), including non-O1/O139 serogroup strains, are able to both colonize the intestine and result in fluid accumulation despite lacking virulence factors believed to be important. Most strains lacked the type three secretion system considered a mediator of diarrhoea in non-O1/O13 V. cholerae. Multi-locus sequence typing (MLST) showed that the Sydney isolates did not form a single clade and were distinct from O1/O139 toxigenic strains. There was no correlation between genetic relatedness and the profile of virulence-associated factors. Current analyses of diseases mediated by V. cholerae focus on endemic regions, with only those strains that possess particular virulence factors considered pathogenic. Our data suggest that factors other than those previously well described are of potential importance in influencing disease outbreaks.

BackgroundThe gut of human harbors diverse commensal microbiota performing an array of beneficial role for the hosts. In the present study, the major commensal gut bacteria isolated by culturing methods from 15 children of moderate income families, aged between 10 and 24 months, were studied for their response to different antibiotics, and the molecular basis of drug resistance.ResultsOf 122 bacterial colonies primarily selected from Luria–Bertani agar, bacterial genera confirmed by analytical profile index (API) 20E® system included Escherichia as the predominant (52%) organism, followed by Enterobacter (16%), Pseudomonas (12%), Klebsiella (6%), Pantoea (6%), Vibrio (3%), and Citrobacter (3%); while Aeromonas and Raoultella were identified as the infrequently occurring genera. An estimated 11 and 22% of the E. coli isolates carried virulence marker genes stx-2 and eae, respectively. Antimicrobial susceptibility assay revealed 78% of the gut bacteria to be multidrug resistant (MDR) with highest resistance to erythromycin (96%), followed by ampicillin (63%), tetracycline (59%), azithromycin (53%), sulfamethoxazole-trimethoprim (43%), cefixime (39%), and ceftriaxone (33%). PCR assay results revealed 56% of the gut bacteria to possess gene cassette Class 1 integron; while 8, 17.5 and 6% of the strains carried tetracycline resistance-related genes tetA, tetB, and tetD, respectively. The macrolide (erythromycin and azithromycin) resistance marker genes mphA, ereB, and ermB were found in 28, 3 and 5% of bacterial isolates, respectively; while 26, 12, 17, 32, 7, 4 and 3% of the MDR bacterial isolates carried the extended spectrum β-lactamase (ESBL)-related genes e.g., bla TEM, bla SHV, bla CMY-9, bla CTX-M1, bla CTX-M2, bla CMY-2 and bla OXA respectively. Majority of the MDR gut bacteria harbored large plasmids [e.g., 140 MDa (43%), 105 MDa (30%), 90 MDa (14%)] carrying invasion and related antibiotic resistance marker genes.ConclusionsOur results suggest gut of young Bangladeshi children to be an important reservoir for multi-drug resistant pathogenic bacteria carrying ESBL related genes.

Background: One of the most significant public health concerns in today's world is the persistent upsurge of infections caused by multidrug resistant bacteria. As a result, clinicians are being forced to intervene with either less effective backup drugs or ones with substantial side-effects. Colistin is a last resort antimicrobial agent for the treatment of infections caused by multi-drug resistant gram-negative bacteria.Methods: Escherichia coli (n = 65) isolated from street food (n = 20), hand rinse (n = 15), surface water (n = 10), and healthy human stool (n = 20) were tested for colistin resistance gene mcr-1 and response to antimicrobial agents. Antimicrobial resistance genes and virulence genes were detected by employing polymerase chain reaction. DNA fingerprinting of the strains were determined by pulsed-field gel electrophoresis. Results:Screening of E. coli allowed us to confirm colistin resistance marker gene mcr-1 in 13 strains (street food, n = 4; hand rinse, n = 2; surface water, n = 4; and stool, n = 3); and two of these E. coli strains carrying mcr-1 harbored bla TEM gene encoding extended spectrum beta lactamase. Antibiotic assay results revealed all 13 E. coli strains carrying mcr-1 to be multi-drug resistant (MDR), including to colistin. The minimum inhibitory concentration (MIC) for colistin ranged from 2 to 6 μg/ml. DNA sequencing confirmed homogeneity of the nucleotide sequence for mcr-1, but the E. coli strains were heterogenous, as confirmed by pulsed-field gel electrophoresis suggesting horizontal transmission of colistin resistance in Bangladesh. Conclusion:Widespread dissemination of E. coli strains carrying mcr-1 encoding resistance to colistin in the present study is alarming as this is the last resort drug for the treatment of infections caused by MDR gram-negative bacteria resistant to almost all drugs used commonly.

An outbreak of cholera occurred in 1991 in Mexico, where it had not been reported for more than a century and is now endemic. Vibrio cholerae O1 prototype El Tor and classical strains coexist with altered El Tor strains (1991 to 1997). Nontoxigenic (CTX−) V. cholerae El Tor dominated toxigenic (CTX+) strains (2001 to 2003), but V. cholerae CTX+ variant El Tor was isolated during 2004 to 2008, outcompeting CTX− V. cholerae. Genomes of six Mexican V. cholerae O1 strains isolated during 1991 to 2008 were sequenced and compared with both contemporary and archived strains of V. cholerae. Three were CTX+ El Tor, two were CTX− El Tor, and the remaining strain was a CTX+ classical isolate. Whole-genome sequence analysis showed the six isolates belonged to five distinct phylogenetic clades. One CTX− isolate is ancestral to the 6th and 7th pandemic CTX+ V. cholerae isolates. The other CTX− isolate joined with CTX− non-O1/O139 isolates from Haiti and seroconverted O1 isolates from Brazil and Amazonia. One CTX+ isolate was phylogenetically placed with the sixth pandemic classical clade and the V. cholerae O395 classical reference strain. Two CTX+ El Tor isolates possessing intact Vibrio seventh pandemic island II (VSP-II) are related to hybrid El Tor isolates from Mozambique and Bangladesh. The third CTX+ El Tor isolate contained West African-South American (WASA) recombination in VSP-II and showed relatedness to isolates from Peru and Brazil. Except for one isolate, all Mexican isolates lack SXT/R391 integrative conjugative elements (ICEs) and sensitivity to selected antibiotics, with one isolate resistant to streptomycin. No isolates were related to contemporary isolates from Asia, Africa, or Haiti, indicating phylogenetic diversity.

Poor food hygiene practices, child feces not being disposed of in a latrine, child mouthing of contaminated fomites, and poor hand hygiene of caregivers have been associated with diarrheal diseases, environmental enteropathy, and impaired growth in young children. Mobile health (mHealth) programs present a low-cost approach to delivering water, sanitation, and hygiene (WASH) programs. We conducted a theory-driven and evidence-based approach to formative research and intervention development to design and pilot test a Baby WASH mHealth program targeting food hygiene, child mouthing, and child feces disposal behaviors in urban Dhaka, Bangladesh. Formative research activities included 31 semi-structured interviews, five group discussions, six mHealth workshops, and a threephase iterative pilot study among 102 households. Findings from semi-structured interviews and group discussions indicate that caregivers of young children have relatively high awareness of the need for safer food hygiene, child mouthing, and child feces disposal practices, but are limited by existing household responsibilities and restricted access to enabling technology that would facilitate practicing recommended behaviors. The piloted Baby WASH mHealth program was well-received by households. This study presents a theory-driven and evidence-based approach for intervention development that can be implemented for the development of future WASH mHealth programs in low-resource settings.