Enterotoxigenic Escherichia coli in Guatemala and Mexico | CDC EID

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Volume 16, Number 1–January 2010
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Enterotoxigenic Escherichia coli Multilocus Sequence Types in Guatemala and Mexico
Matilda Nicklasson, John Klena, Claudia Rodas, August Louis Bourgeois, Olga Torres, Ann-Mari Svennerholm, and Åsa Sjöling
Author affiliations: University of Gothenburg, Gothenburg, Sweden (M. Nicklasson, C. Rodas, A.-M. Svennerholm, Å. Sjöling); United States Naval Medical Research Unit 3, Cairo, Egypt (J. Klena); Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA (A.L. Bourgeois); and Instituto de Nutrición de Centro América y Panamá, Guatemala City, Guatemala (O. Torres)

Suggested citation for this article

Abstract
The genetic backgrounds of 24 enterotoxigenic Escherichia coli (ETEC) strains from Mexico and Guatemala expressing heat-stable toxin (ST) and coli surface antigen 6 (CS6) were analyzed. US travelers to these countries and resident children in Guatemala were infected by ETEC strains of sequence type 398, expressing STp and carrying genetically identical CS6 sequences.

Enterotoxigenic Escherichia coli (ETEC) is one of the most common causes of acute watery diarrhea among children and adults in the developing world, causing ≈400 million diarrheal episodes and 380,000 deaths in children <5 years of age every year (1). The diarrhea is mediated by 1 or 2 plasmid-encoded enterotoxins; the heat-stable toxin (ST) and/or the heat-labile toxin (LT) (1). Approximately one third of all ETEC strains isolated globally reportedly produce ST only, one third produce LT and ST, and one third produce LT only (2). Two genotypes of ST exist in ETEC strains infecting humans: STp and STh (3). Colonization of the small intestine is mediated by adhesion to the epithelial cells by colonization factors (CFs), and one of the most common CFs detected on clinical ETEC isolates from different parts of the world is the plasmid-encoded coli surface antigen 6 (CS6) (4).

In a recent vaccine trial conducted in Mexico and Guatemala involving adult US travelers, ST-only strains expressing only CS6 and no other CF predominated among those infected with CF-positive ETEC; this toxin-CF profile (ST/CS6) was present in 35% of diarrheal cases (5). In other geographic regions, e.g., Egypt and Bangladesh, studies on childhood diarrhea have reported ST/CS6 frequencies of 6.6% and 19%, respectively (6,7). We conducted this study to investigate whether adult travelers in Mexico and Guatemala are infected with certain circulating ST/CS6 ETEC strains and to determine whether ETEC strains with the same E. coli clonal background may be infecting resident children in the same areas.

The Study
Seventeen clinical ST/CS6 isolates collected from adult US travelers, who were either visiting various locations in Guatemala or remaining at least 14 days in Antigua in Guatemala, or in Cuernavaca, Mexico, were included in the study. Isolates were collected from 1998 to 2001 during ETEC vaccine trials (5,8) or in 2002 and 2003 during a study of antimicrobial drug treatment (9). During June 2001–October 2003, clinical stool specimens were collected from children living in Santa María de Jesús in Guatemala as part of an ongoing childhood ETEC study (O. Torres, unpub. data). Seven CS6 isolates obtained from that study, collected in the summer of 2002, were included in the present study. Clinical isolates from both children and adults were shipped to Sweden, where toxin and CF profiles were confirmed as described (10). All strains in the study expressed STp, except for strain E874, which expressed STh.

Isolates were analyzed by multilocus sequence typing (MLST) by using the E. coli MLST scheme (http://mlst.ucc.ie/mlst/dbs/Ecoli), which is based on sequencing of internal regions of the 7 housekeeping genes adk, fumC, gyrB, icd, mdh, purA, and recA (11). PCR was performed as described but by using the same annealing temperature (54°C) for all genes.

Suggested Citation for this Article
Nicklasson M, Klena J, Rodas C, Bourgeois AL, Torres O, Svennerholm A-M, et al. Enterotoxigenic Escherichia coli multilocus sequence types in Guatemala and Mexico. Emerg Infect Dis [serial on the Internet]. 2010 Jan [date cited]. Available from http://www.cdc.gov/EID/content/16/1/143.htm

DOI: 10.3201/eid1601.090979


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