- Professor: ‘Fecal particles from one person reaching the mouth of another’ are to blame for most infections by the antibiotic-resistant bacteria.
- Study highlights age-old hygiene rule: ‘It’s much more important to wash your hands after going to the toilet.’
NORWICH, England — E. coli can be found within the lower intestines of warm-blooded organisms, humans and animals alike. Normally, this bacterium aids in digestion, but it can also cause all sorts of problems if it infects other areas of the human body. Though perhaps most often associated with transference through undercooked chicken or poorly washed lettuce, a new study conducted at East Anglia University in Norwich, England finds that the antibiotic-resistant E. coli is much more likely to spread from person to person via poor toilet hygiene habits than anything related to food or eating.
E. coli comes in a variety of different strains, some of which cause severe bouts of food poisoning, while others may result in urinary tract infections. In worst case scenarios, E. coli exposure can lead to bacteraemias, or bloodstream infections. Confounding matters is the fact that many strains of the bacteria have developed a resistance to conventional antibiotics over the past 20 years among both humans and animals. Some of the most talked about strains harbor a specific group of enzymes called Extended Spectrum Beta-Lactamases (ESBLs). These enzymes have the ability to destroy many important penicillin and cephalosporin antibiotics.
Up until now, scientists have been unsure whether antibiotic-resistant E. coli strains are typically spread through food and eating or via person-to-person transference. In order to investigate this matter, researchers sequenced resistant E. coli genomes from various sources across the United Kingdom. Such sources included human feces, human sewerage, human bloodstream infections, animal manure, as well as different food types like chicken, beef, pork, fruit, and salad.
Their subsequent findings revealed that all of the “superbug” strains of E. coli stemming from sources like human blood, feces and sewerage samples were all very similar to each other. More specifically, among the aforementioned ESBL strains of E. coli, a strain called “ST131” dominated the findings regarding human samples. Additionally, strains from meat such as chicken and beef, as well as animal waste, were for the most part very different than the strains commonly infecting humans.
All of this led researchers to conclude that it is very rare for an animal strain of the bacteria to infect humans.
“E. coli bacteria normally live in the intestines of healthy people and animals. Most varieties are harmless or cause brief diarrhea,” explains lead author professor David Livermore in a release. “But E. coli is also the most common cause of blood poisoning, with over 40,000 cases each year in England alone. And around 10 per cent of these cases are caused by highly resistant strains with ESBLs. Infections caused by ESBL-E. coli bacteria are difficult to treat. And they are becoming more common in both the community and hospitals. Mortality rates among people infected with these superbug strains are double those of people infected with strains that are susceptible to treatment.”
ESBL-E. coli can be found quite often in grocery store chicken and other types of meat, but just how much these sources actually result in transference to humans has been largely debated up until now.
“We wanted to find out how these superbugs are spread – and whether there is a crossover from the food chain to humans,” professor Livermore continues.
The research team took ESBL-E. coli from infected human blood samples and compared those samples to ESBL-E. coli collected from human waste, sewage, food, dairy farm manure, and animals from five different areas of the U.K. — London, East Anglia, Northwest England, Scotland and Wales.
“We looked at more than 20,000 fecal samples and around nine per cent were positive for ESBL-E. coli across the regions, except for in London, where the carriage rate was almost double – at 17 per cent,” professor Livermore says. “We found ESBL-E. coli in 65 per cent of retail chicken samples – ranging from just over 40 per cent in Scotland to over 80 per cent in Northwest England. But the strains of resistant E. coli, were almost entirely different from the types found in human feces, sewage and bloodstream infections.”
Only a few of the tested pork samples tested positive for E. coli. The bacteria wasn’t detected among over 400 fruit and vegetable samples.
Overall, professor Livermore says that his research indicates that there is a clear distinction between human-based strains of ESBL-E. coli, specifically ST131, and animal strains. Most importantly, this means that there is little crossover between human and animal strains; most human infections are not coming from eating chicken, or any other food substance for that matter.
“Rather – and unpalatably – the likeliest route of transmission for ESBL-E. coli is directly from human to human, with fecal particles from one person reaching the mouth of another,” professor Livermore concludes. “We need to carry on cooking chicken well and never to alternately handle raw meat and salad. There are plenty of important food-poisoning bacteria, including other strains of E. coli, that do go down the food chain. But here – in the case of ESBL-E. coli – it’s much more important to wash your hands after going to the toilet.”
The study is published in The Lancet Infectious Diseases.