Researchers Warn of Bacteria Found in Desserts in Mexico

March 25, 2009

A study to be published in the April issue of the American Journal of Tropical Medicine and Hygiene reports that desserts from restaurants in Mexico are likely to give patients travelers’ diarrhea, and are yet another food to avoid when visiting developing countries where sanitation may not be optimal.

Diarrhea is the most common illness affecting travelers to destinations in developing and subtropical regions. Bacterial causes are most common, especially distinctive strains of E. coli called enterotoxigenic and enteroaggregative (not to be confused with the severe 0157:H7 Shiga toxin producing E. coli (e.g. O157:H7) found in the U.S.).

In this study, investigators obtained a variety of desserts from 35 randomly selected restaurants in Guadalajara, Mexico and from 33 randomly selected restaurants in Houston, Texas. More than 95 percent of the dessert samples from Guadalajara were positive for coliform bacteria (reflecting fecal contamination), with an average coliform count of 58,000 bacteria per gram of dessert. About 20 percent of the Houston samples were positive for coliform bacteria but with a much lower bacterial count: 2000 bacteria per gram of dessert. E. coli was found in 12 percent of the Mexican samples but in none of the Houston samples. Enterotoxigenic E. coli was the most common strain of E. coli found, and enteroaggregative E. coli was found as well. Ice cream was the most common culprit.

When seeking travel advice, travelers are typically warned to avoid all foods that are not served hot, and to personally peel and prepare fruits and vegetables to avoid contracting food-borne illnesses such as traveler’s diarrhea. Other generally safe items include dry bread, syrups, jellies and jam. This study points out that desserts, especially ice cream, are another specific food item to avoid. The authors generalize their findings to ice cream desserts served in other developing countries, not just Mexico.

However, interpretations of the authors’ findings need to be tempered somewhat, since the authors did not specifically test ice cream or other desserts prepared by large manufacturers such as D’Onofrio made by Nestle which are common and popular, particularly in Latin America.

Other contributors to the paper were first author Karen J. Vigil from the University of Texas Medical School at Houston, Zhi-Dong Jiang from the UT School of Public Health at Houston, and Baylor College of Medicine, Houston, Texas.

The American Journal of Tropical Medicine and Hygiene is the official journal of the American Society of Tropical Medicine and Hygiene, a worldwide organization of scientists, clinicians, and program professionals whose mission is to promote global health through the prevention and control of infectious and other diseases that disproportionately afflict the global poor.

Provided by American Society of Tropical Medicine and Hygiene