By Emilio Godoy
In the 1998 medical thriller “Toxin” by U.S. novelist Robin Cook, the ground beef in hamburgers is contaminated with a deadly strain of the Escherichia coli or E. coli bacterium, unleashing a massive epidemic. The novel was inspired by a real outbreak that took place several years earlier.
The appearance of a new strain of E. coli in Germany, which has claimed at least 25 lives and made more than 2,600 people seriously ill since May, might seem like a sequel to the novel, but there is nothing fictional about it. The outbreak has scientists stymied, and its source has still not been definitively pinpointed.
There can be doubt, however, that the industrial production of food contributes to the spread of E. coli.
Most strains of the bacterium are harmless. E. coli is naturally present in the intestines of healthy mammals, including humans, and plays a role in the digestive process. At the end of that process, the bacterium passes into the wastewater system through feces.
E. coli is also used in the development of transgenic food, pharmaceutical and veterinary products, in synthetic biology, and in the creation of transgenic hormones, such as those given to cows to increase milk production.
“The food industry has an impact on the generation and propagation of these bacteria. In the production of meat and crops that grow close to the ground, the probability of contamination is high, since crops like melons, cucumbers, squash and strawberries are most often irrigated with wastewater,” Irma Martínez, a researcher at the Autonomous University of Nuevo León School of Biological Sciences, told Tierramérica.
There are six known pathogenic or disease-causing strains of E. coli. The most deadly are the enterohemorrhagic strains, such as O157:H7, discovered in 1982 in the ground beef in hamburgers in the United States, and O104:H4, the strain responsible for the current E. coli outbreak in Europe.
Martínez and six other researchers found traces of O157:H7 in two of 40 samples of beef from large supermarkets in the northwestern Mexican city of Monterrey. The results of their study were published in the June 2009 issue of the journal Salud Pública y Nutrición (Public Health and Nutrition).
“Through evolution and evolutive pressure (the inappropriate use of antibiotics, genome mutations and other causes), different strains have developed that can cause illness and outbreaks like the one that appeared in Germany,” Adrián Canizález-Román, a molecular biology researcher at the Autonomous University of Sinaloa School of Medicine, told Tierramérica.
E. coli infections are a common occurrence in many developing countries.
For many years, Argentina, with a population of 40 million, has had the highest incidence in the Latin American region of hemolytic uremic syndrome (HUS) caused by enterohemorrhagic E. coli.
The main source of infection is undercooked beef, and the most frequent victims are children under the age of five. Argentina produces over three million tons of beef a year, of which 480,000 tons are exported in accordance with strict health standards.
However, these standards are often not met in the local production chain, according to the League Against Hemolytic Uremic Syndrome, an organization made up of the families of HUS victims.
The symptoms of HUS include bloody diarrhea, vomiting, irritability, difficulty urinating and sometimes convulsions. It can be fatal and frequently results in complications such as kidney failure and neurological problems. Kidney transplants are often needed to correct the damage it causes.
The number of cases in Argentina is relatively stable, “between 400 and 500 infected,” and roughly 15 out of every 100,000 children under five, said Marta Rivas, head of the Physiopathology Service at the National Institute of Infectious Diseases.
The E. coli outbreak in Germany is totally unrelated to the situation in Argentina because “a different strain is predominant here,” she told Tierramérica. Rivas met with Ministry of Health officials in early June to establish guidelines to prevent the possible entry of the German strain.
“The idea is to reinforce prevention and strengthen vigilance in the laboratories and in the description of cases,” she explained.
In Mexico, a country with a population of 112 million, pathogenic strains of E. coli are responsible for 20 percent of cases of childhood diarrhea, according to the Ministry of Health.
The research study “Biochemical and Genetic Diversity of Enterotoxigenic Escherichia coli Associated with Diarrhea in United States Students in Cuernavaca and Guadalajara, Mexico, 2004–2007” found a small number of strains that could be endemic to the country and several that are specific to these two cities, located in central and northwestern Mexico, respectively.
The samples for the study, published June 2010 in The Journal of Infectious Diseases, came from 213 U.S. students who were living in Cuernavaca and Guadalajara.
But simple preventive measures such as hand washing, cooking food thoroughly and more effectively purifying drinking water have reduced the incidence of the bacterium. “Little by little, practices have improved,” commented Martínez.
Ten percent of the Mexican population has no access to running water and 13.6 percent lacks basic sanitation services, according to the National Water Commission. There are more than 250 facilities run by the National Service for Agro-Alimentary Health, Safety and Quality which are responsible for enforcing health standards for fruits, vegetables and animal products.
But “the main problem in the dissemination and proliferation of the bacteria is the international movement of food and people,” said Canizález-Román.
On Jun. 9 the Ministry of Health in Peru issued an “epidemiological alert” to all health services aimed at the “timely” detection of any cases of HUS “in patients who have come from Europe.” The ministry has also called on the public to step up hygienic measures “in all food production systems.”
Sources at the National Service for Agricultural Health told Tierramérica that “there is no risk of anything” because “Peru doesn’t import cucumbers, on the contrary, we export them.” However, by late May it had been determined that cucumbers imported from Spain were not the source of the German E. coli outbreak, as had earlier been suspected.
In Peru it is quite common for people suffering from diarrhea or other infections caused by E. coli to self-medicate, which contributes to the development of antibiotic-resistant strains.
The director of Access and Appropriate Use of Medicines at the General Directorate of Medicines, Medical Supplies and Drugs in Peru, Pedro Yarasca, warned that 34 percent of E. coli infections have shown resistance to two types of antibiotics in the country’s hospitals.
In Brazil, a research study published in February looked at 4,372 urinary tract infections caused by E. coli recorded in 2002 in two outpatient clinics in the southern Brazilian city of São Paulo, and found that 723 proved to be resistant to treatment with ciprofloxacin.
* * Additional reporting by Marcela Valente (Buenos Aires) and Milagros Salazar (Lima).