By now we should all be familiar with the bacterial species Escherichia coli as it is present among the natural bacteria in the guts of both humans and animals. Known more commonly as E. coli, some strains of this bacteria can be harmful, especially as part of an infection and especially because they have developed resistance to antibiotics.
But even though we know all of this, people can still become infected with dangerous strains of E. coli; and researchers are only really starting to understand this now.
Again, the strain of E. coli that is native to the human gut is not usually dangerous. When ingesting harmless E. coli, the bacteria simply becomes part of the natural bacteria that populates the gut. When the body is introduced to the incompatible E. coli strains it can result in food poisoning, urinary tract infections, and, of course, intestinal infections. And should these infections go untreated (or undiagnosed in some cases) it can leak into the bloodstream, which leads to a condition called bacteremia, which can cause septic shock.
Now, because we know that E. coli naturally populates animal guts, it is easy to determine that animal protein is always a possible source for E. coli infection: it is the main reason why we must cook protein to the appropriate temperature. However, another possible source for E. coli infection is poor hygiene: not washing your hands after using the bathroom, for example.
Until now, though, scientists have not isolated which of these two main sources of E. coli infection is more likely. A new study, then, has investigated just that, by collecting antibiotic resistant E. coli strains from various meat sources as well as animal slurry, salads, and fruit and compared them against strains of E. coli found in the human bloodstream and feces, as well as in municipal sewage.
These samples were collected specifically from National Health Service laboratories in five different regions of the United Kingdom.
The study, perhaps somewhat shockingly, revealed that resistant E. coli strains present in human samples had many similarities. They determined that the dominant strain present among human samples was only ST131. On the other hand, samples in food showed almost no traces of strain ST131. Instead, the found the presence of ST23, ST117, ST602.
The researchers concluded that since there is no crossover between human and non-human strains, even among contaminated foods, most antibiotic resistant E. coli infection is spread by human to human contact.
The results of this study have been published in The Lancet Infectious Diseases.