People who do not wash their hands after they go to the toilet, but not prepared meat, are behind the spread of a key strain of E. coli.  Experts examined thousands of blood, faeces and food samples.
They found that person-to-person transmission was responsible ̵
Public health England said hand washing and good hygiene were key to preventing the spread of infections.
There are many different strains of E. coli. Most are harmless, but some can cause serious illness.
Antibiotic resistant E. coli is becoming more common. Strains that have "enhanced spectral beta-lactamases (ESBLs) – enzymes that destroy penicillin and another antibiotic, cephalosporin – are of particular concern.
E. coli is the most common cause of blood poisoning, accounting for about a third of cases in the UK, with ESBL strains accounting for about 10% of them – about 5000 per year
In a study published in Lancet: Infective Diseases, the team analyzes 20,000 human feces and 300 blood samples plus hundreds of sewage, animal porridge and meat samples, including beef, pork and chicken, as well as fruits and salad.
One strain, ST131, was observed in the majority of human samples from all three sources. It is found in the intestine, but it can usually cause serious infections through urinary tract infections.
However, the strains found in meat, cattle and animal porridge are mostly different.
Prof. David Livermore, of the University of the East Norwich School of Medicine, England, which runs the research, said: "Critically, there are few cross-links between strains of humans, chickens and cattle.
"Rather – and inconveniently – the most likely transmission path for ESBL-E. coli is direct from person to person, with the particles of faeces from one person reaching the mouth of another. "
He said that maintaining food hygiene is still important – people have to deal with raw meat carefully, not least because there are other strains of food, ie poisoning of bacteria that come
But he added: "Here – in the case of ESBL-E. cars – it is much more important to wash your hands after going to the toilet.
" It is especially important to have good hygiene in care homes as most severe E. coli infections occur among the elderly and people may need help going to the toilet. "
Prof. Public Health England's Neil Woodford says: "To tackle antibiotic resistance, we must not only remove inappropriate prescriptions, but first and foremost reduce infections."
"To curb serious, antibiotic-resistant E. infection. coli in the blood, we need to focus on thorough handwashing and good infection control as well as effective management of urinary tract infections. "