Prevalence of toxin types and colonization factors in enterotoxigenic Escherichia coli isolated during a 2-year period from diarrheal patients in Bangladesh

The prevalence of toxin types and colonization factors (CFs) of enterotoxig enic Escherichia coli (ETEC) was prospectively studied with fresh samples ( n = 4,662) obtained from a 2% routine surveillance of diarrheal stool sampl es over 2 years, from September 1996 to August 1998, Stool samples were tes ted by enzyme-linked immunoassay techniques and with specific monoclonal an tibodies for the toxins and CFs. The prevalence of ETEC was 14% (n = 662), with over 70% of the strains isolated from children 0 to 5 years of age, of whom 93% were in the 0- to 3-year-old age range. Of the total ETEC isolate s, 49.4% were positive for the heat-stable toxin (ST), 25.4%, were positive for the heat-labile toxin (LT) only, and 25.2% were positive for both LT a nd ST, The rate of ETEC isolation peaked in the hot summer months of May to September and decreased in winter. About 56% of the samples were positive for 1 or more of the 12 CFs that were screened for. The coli surface antige ns CS4, CS5, and/or CS6 of the colonization factor antigen (CFA)ITV complex were most prevalent (incidence, 31%), followed by CPA/I (23.5%) and coli s urface antigens CS1, CS2, and CS3 of CFA/II (21%). In addition, other CFs d etected in decreasing order were CS7 (8%), CS14 (PCFO166) (7%), CS12 (PCFO1 59) (4%), CS17 (3%), and CS8 (CFA/III) (2.7%), The ST- or LT- and ST-positi ve ETEC isolates expressed the CFs known to be the most prevalent (i.e., CF A/I, CFA/II, and CFA/IV), while the strains positive for LT only did not. A mong children who were infected with ETEC as the single pathogen, a trend o f relatively more severe disease in children infected with ST-positive (P < 0.001) or LT- and ST-positive (P < 0.001) ETEC isolates compared to the se verity of the disease in children infected with LT only-positive ETEC isola tes was seen. This study supports the fact that ETEC is still a major cause of childhood diarrhea in Bangladesh, especially in children up to 3 years of age, and that measures to prevent such infections are needed in developi ng countries.