Impact of Rapid Urbanization on the Rates of Infection by Vibrio cholerae O1 and Enterotoxigenic Escherichia coli in Dhaka, Bangladesh

Bangladesh is a country where acute dehydrating diarrhea or cholera is common and is seen at least two times every year and additionally in natural disasters. In addition cholera cases have increased in the country, especially in urban settings such as in the capital city, Dhaka, where the number of hospitalized patients with more severe disease has tremendously increased. In the present observation, we have concentrated on determining the occurrence of diarrhoea caused by the two most common bacterial agents V. cholerae O1 and enterotoxigenic Escherichia coli (ETEC) in a densely populated, disease prone area Mirpur in Dhaka for two years from March 2008 to February 2010. Stool or rectal specimens from diarrheal patients coming to the ICDDR,B hospital from Mirpur were tested for the two bacterial pathogens. We found that V. cholerae O1 was the major bacterial pathogen and a cause of severe cholera disease in 23% of patients (2,647 of a total of 11,395 patients) from Mirpur. We surmise that cholera vaccines, as well as other public health tools that can target such high risk groups in the country, will be able to reduce the disease morbidity and the transmission of pathogens to improve the quality of life in urban settings

Shift in Phenotypic Characteristics of Enterotoxigenic <i>Escherichia coli</i> (ETEC) Isolated from Diarrheal Patients in Bangladesh

<div><p>Background</p><p>Enterotoxigenic <i>Escherichia coli</i> (ETEC) is one of the most common causes of bacterial diarrhea. Over the last decade, from 1996 to 2012, changes in the virulence antigen properties of ETEC such as heat labile (LT) and heat stable (ST) toxins, colonization factors (CFs), and ‘O’-serogroups have been observed. The aim of this prospective study was to compare changes in antigenic profiles of ETEC strains isolated from a 2% surveillance system at the icddr,b hospital in Dhaka, Bangladesh between 2007–2012 and an earlier time period of 1996–1998 conducted at the same surveillance site.</p><p>Methodology</p><p>In the surveillance system every 50^th patient attending the hospital was screened for major enteric pathogens including ETEC, <i>Vibrio cholerae</i>, <i>Shigella</i> spp. and <i>Salmonella</i> spp. from January 2007 to December 2012.</p><p>Principal Findings</p><p>Of the 15,152 diarrheal specimens tested between 2007–2012, the overall rate of ETEC isolation was 11%; of these, 43% were LT/ST, 27% LT and 30% ST positive. Isolation rate of ST-ETEC (p<0.009) and LT/ST ETEC (p<0.011) during 2007–2012 period differed significantly compared to those seen between 1996–1998. In comparison to the 1996–1998 period, difference in CF profile of ETEC isolates during 2007–2012 was observed particularly for strains expressing CS7 (12.4%), CS14 (9.5%) and CS17 (10.0%). The predominant CF types were CS5+CS6, CFA/I, CS7, CS17, CS1+CS3, CS6 and CS14. The most common serogroups among the CF positive ETEC isolates were O115, O114, O6, O25 and O8. A strong association was found between CFs and ‘O’ serogroups i.e. between CS5+CS6 and (O115 and O126); CS7 and (O114), CFA/I and (O78 and O126), CS17 and (O8 and O167) and CS1/CS2+CS3 and (O6).</p><p>Conclusion</p><p>The analyses show a shift in prevalence of antigenic types of ETEC over the study period; the information is important in designing effective ETEC vaccines with broad protective coverage.</p></div

Relative distribution of colonization factors (CFs) in ETEC isolates from diarrhea cases in Bangladesh according to year of isolation and association of specific CFs with toxin profile.

<p>Relative distribution of colonization factors (CFs) in ETEC isolates from diarrhea cases in Bangladesh according to year of isolation and association of specific CFs with toxin profile.</p

Relationship between toxin profile and dehydration status of ETEC diarrheal patients during 2007–2012.

<p>p value for chi-squared test: 0.046 (2010–2012); indicates LT vs LT/ST ETEC for severe cases.</p>a<p>Degree of dehydration based on World Health Organization guideline.</p

Toxin profile of ETEC strains isolated from diarrheal patients in Bangladesh during two study periods.

<p>*: Qadri <i>et.al</i> 2000.</p><p>NS: Not significant.</p