title: Enterotoxigenic Escherichia coli heat-labile toxin seroconversion in US travelers to Mexico.
abstract: OBJECTIVE
  Enterotoxigenic Escherichia coli (ETEC) is the most common bacterial pathogen isolated from travelers suffering of diarrhea. Exposure to heat-labile toxin (LT) produces a high rate of seroconversion. However, the role of LT-producing ETEC (LT-ETEC) as a cause of diarrhea is controversial. We conducted a cohort study in US students traveling to Mexico to assess the ETEC-LT seroconversion rate after natural exposure.
  
  
  METHODS
  Participants provided a serum sample on arrival and departure and a stool sample when ill. ETEC-LT immunoglobulin G antibodies were measured by enzyme-linked immunosorbent assay, and LT-ETEC were detected by means of polymerase chain reaction done on fecal DNA.
  
  
  RESULTS
  A total of 422 participants with a mean age of 34.5 years were followed a mean of 19.9 days; 304 were females (72.0%), and 319 (75.6%) traveled during the summer months. In total, 177 individuals (41.9%) developed travelers' diarrhea and 33.9% had LT-ETEC identified in their stools. Among individuals having an LT-ETEC strain, 74% seroconverted compared to 11% of those not having diarrhea (p < 0.0001). When analyzed with a logistic regression model, the odds of seroconversion were significantly reduced in participants not having LT-ETEC in their stool (odds ratio = 0.1, p < 0.0001) after adjusting for season, length of stay, age, gender, race, and ethnicity.
  
  
  CONCLUSIONS
  In US young adults traveling to Mexico, ETEC-LT seroconversion reliably identifies individuals naturally exposed to ETEC and correlates with symptomatic illness, length and season of travel.
authors.affiliation: Division of Infectious Diseases, University of Texas Medical School at Houston, Houston, TX 77030, USA.
authors.forename: Jose
authors.initials: J
authors.lastname: Flores
authors.forename: Herbert L
authors.initials: HL
authors.lastname: DuPont
authors.forename: Zhi-Dong
authors.initials: ZD
authors.lastname: Jiang
authors.forename: Jaime
authors.initials: J
authors.lastname: Belkind-Gerson
authors.forename: Jamal A
authors.initials: JA
authors.lastname: Mohamed
authors.forename: Lily G
authors.initials: LG
authors.lastname: Carlin
authors.forename: Ranjit S
authors.initials: RS
authors.lastname: Padda
authors.forename: Mercedes
authors.initials: M
authors.lastname: Paredes
authors.forename: Jose Francisco
authors.initials: JF
authors.lastname: Martinez-Sandoval
authors.forename: Nicolas A
authors.initials: NA
authors.lastname: Villa
authors.forename: Pablo C
authors.initials: PC
authors.lastname: Okhuysen
mesh_terms: D000328:Adult; D000367:Age Factors; D001427:Bacterial Toxins / Q000302:isolation & purification*; D003967:Diarrhea / Q000453:epidemiology / Q000382:microbiology*; D004768:Enterotoxins / Q000302:isolation & purification*; D004797:Enzyme-Linked Immunosorbent Assay; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000382:microbiology*; D029968:Escherichia coli Proteins; D005243:Feces / Q000382:microbiology; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D008297:Male; D008800:Mexico; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D012307:Risk Factors; D012621:Seasons; D012698:Serologic Tests; D012737:Sex Factors; D013334:Students / Q000706:statistics & numerical data; D014195:Travel / Q000706:statistics & numerical data*; D014481:United States / Q000453:epidemiology
chemical_list: D001427:Bacterial Toxins; D004768:Enterotoxins; D029968:Escherichia coli Proteins; D007074:Immunoglobulin G; C034151:heat stable toxin (E coli)