A new study has suggested that not washing hands after using the toilet is mainly responsible for the spread of antibiotic-resistant Ecoli superbugs.

Research from the University of East Anglia in the UK says Ecoli is more likely to be spread through poor toilet hygiene than undercooked chicken or other food.

Ecoli has become considerably more antibiotic resistant over the past 20 years - both in humans and animals.

Particularly important are strains with 'Extended Spectrum Beta-Lactamases' (ESBLs) - as these are enzymes that destroy many important penicillin and cephalosporin antibiotics.

Many strains with ESBLs often have other key resistances too.

But until now, it has not been known whether antibiotic-resistant Ecoli that cause bloodstream infections are picked up through the food chain, or passed from person to person.

To answer this question, scientists sequenced the genomes of resistant Ecoli from multiple sources across the UK: including from human bloodstream infections, human faeces, human sewerage, animal slurry and meat.

Their report in The Lancet Infectious Diseases reveals that antibiotic-resistant 'superbug' strains of Ecoli from human blood, faeces and sewerage samples were similar to one another.

Strain 'ST131' dominated among ESBL Ecoli from all these human sample types.

Resistant Ecoli strains from meat - mainly chicken, cattle and animal slurry - were largely different to those infecting humans.

In short, there was little crossover of ESBL-Ecoli from animals to humans.

'Highly resistant strains'

Professor David Livermore from UEA's Norwich Medical School is the lead author.

He said: "Ecoli bacteria normally live in the intestines of healthy people and animals.

"Most varieties are harmless or cause brief diarrhoea.

"But Ecoli is also the most common cause of blood poisoning, with over 40,000 cases each year in England alone.

"And around 10% of these cases are caused by highly resistant strains with ESBLs.

"Infections caused by ESBL-Ecoli 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're susceptible to treatment."

ESBL-Ecoli are widespread in retail chicken meat and food animals too - but until now, the extent of transmission from these sources to humans has been uncertain.

Prof Livermore explained: "We looked at more than 20,000 faecal samples and around 9% were positive for ESBL-Ecoli across the regions, except for in London, where the carriage rate was almost double - at 17%.

"We found ESBL-Ecoli in 65% of retail chicken samples... But the strains of resistant Ecoli, were almost entirely different from the types found in human faeces, sewage and bloodstream infections.

"Only a very few beef and pork samples tested positive, and we didn't detect ESBL-Ecoli at all in 400 fruit and vegetable samples – many of which were imported to the UK.

"In short, what the results show is that there are human-adapted strains of ESBL-Ecoli, principally ST131, which dwell in the gut and which occasionally - usually via UTIs - go on to cause serious infections."

"The great majority of strains of ESBL-Ecoli causing human infections aren't coming from eating chicken, or anything else in the food chain.

"Rather - and unpalatably - the likeliest route of transmission... is directly from human to human, with faecal particles from one person reaching the mouth of another."