In 1885, a 28-year-old German-Austrian physician named Theodor Escherich wanted to understand why infants and small children were prone to diarrhea. So he started studying his young patients’ stool specimens under a microscope.
Escherich found himself gazing through the lenses at countless millions of tiny, rod-shaped bacteria that zipped across his field of view, propelled by spinning, propeller-like flagella. He had discovered a new and important species of bacteria that lives in the lower intestines and colons of humans and other warm-blooded animals. That discovery proved to be an important advance in microbiology, and his bacteria eventually was named Escherichia coli….
Better known as E. coli.
Over the decades, E. coli became a focus for medical and scientific research. Scientists learned that humans are home to countless millions of the bugs, which play crucial roles in digestion, the immune system and more. In 1997, the E. coli genome became one of the first to be mapped. And those amazing, spinning flagella became an issue in the debate over evolution theory.
But, as Escherich suspected, certain strains of pathogenic E. coli — shed in the feces of healthy ruminants — can contaminate food and make people very sick.
Now, 126 years after his original discovery, Escherich’s home country is caught up in an epidemic of enterohemorrhagic E. coli (EHEC) poisoning with more than 400 suspected cases and three or four fatalities. There are reports of 140 life-threatening cases of hemolytic-uremic syndrome (HUS), which can lead to kidney failure. That puts the epidemic in the same frightening statistical league as the American Jack in the Box outbreak of 1993.
And Escherich’s scientific descendants, German health authorities and microbiologists, have been gazing through their own lenses, groping for clues to the source of the outbreak — one or more foods that might have been consumed by each of those victims.
Following another death on Wednesday, health authorities at the Robert Koch Institute (RKI), the German equivalent of the U.S. Centers for Disease Control and Prevention, advised against eating tomatoes, cucumbers or lettuce from the north part of the country. But on Thursday, the state health minister for Hamburg, Cornelia Pruefer-Storcks, said the Hamburg Institute for Hygiene and the Environment had identified contaminated cucumbers imported from Spain as a possible source of the outbreak. The suspect vegetables might have been contaminated by cow manure used as fertilizer.
The outbreak began to get attention a week ago, May 19, when health authorities learned that several people in Hamburg were being treated for HUS, a potentially lethal syndrome frequently linked with E. coli poisoning.
HUS cases are relatively rare; only 65 cases were reported in Germany in all of 2010.
There are other alarming aspects to the German outbreak that have attracted the interest of public health officials around the world. In most E. coli outbreaks, the victims are mostly children, because their immune systems are unable to resist the toxins carried by certain E. coli strains.
This time, most of the German victims are adults, and most are women.
Also unusual is the specific strain of E. coli that has been detected as the cause of the outbreak. For the last 20 years, many but not all E. coli illnesses have been traced to E. coli O157:H7, which carries the potentially deadly toxins that cause internal bleeding and kidney damage.
The German outbreak has been preliminarily attributed to E. coli O104, which appears to be a rare EHEC serotype — or at least one identified only in recent years.
In the United States, an outbreak of E. coli O104:H21 in 1994 sickened 18 people in Helena, Montana. A CDC investigation into that outbreak found the median age of the case patients was 36 years and, as in Germany, most were women.
Kai Kupferschmidt, reporting Wednesday in Science Insider, pointed out another notable aspect to the strain detected in Germany: it is eae-negative. “The gene eae codes for the protein intimin, which the bacteria uses to attach to the intestinal wall. Most pathogenic EHEC serogroups are eae-positive,” Kupferschmidt wrote, adding that it’s not clear whether the serotype may explain the strange patterns and rapid spread of infections.
Like other “non-0157” strains, these bacteria are not even officially listed as adulterants – food poisons.
The German outbreak may help change that.
But, for authorities at RKI and across Germany, the first priority is to trace the pathogen to its mysterious source, and that process is ongoing. The essence of fieldwork to trace epidemics is interviews with sick patients, with lengthy questionnaires designed to find common denominators. What is the one food that all or most of the sick Germans have eaten in the last three weeks?
According to one German report, all of the victims in Frankfurt ate at the same cafeteria in that city. That information could lead investigators to the source — even if the contaminated food is long gone.