The National reports that every sample of rocket salad leaves tested from 64 shops in Dubai and Sharjah was contaminated with high levels of potentially deadly E. coli bacteria, researchers have found.

The leaves – also called jarjeer, or arugula – came from outlets ranging from small stores to large supermarket chains. Millions of faecal coliform cells and hundreds of thousands of E. coli bacteria were found in samples of one gram, about the size of a small leaf.

The samples were analysed by Dr Dennis Russell, a researcher at the American University of Sharjah. After washing the leaves three times he still found hundreds of thousands of viable faecal coliform microorganisms per gram, and thousands of E. coli bacteria.

Washing with diluted chlorine bleach did not remove the bacteria.

Dr Russell’s research is published in the current issue of the Egyptian Academic Journal of Biological Sciences.

Dr Tibor Pal, a professor of microbiology and immunology at United Arab Emirates University, said that although E. coli was not always harmful, high levels indicated faecal contamination and risk of other serious diseases.

Dr Russell said he had been unable to determine where the rocket leaves had been grown – whether they were from UAE farms or imported – but he said he suspected they all came from the same farm or a group of farms that had used liquified raw faeces for fertiliser rather than compost soil.