You might think that your kitchen is sparkling clean, but it’s probably 200 times more germ-infested than your lavatory seat.

The culprits are sponges and dishcloths, which can provide a happy home for millions of the bugs that cause food poisioning, which is on the increase.

American researchers, however, have come up with a devastatingly simple answer to the gastroenteritis threat: zap the little devils in the microwave.

If the evidence is to be believed, our kitchen hygiene borders on the deplorable. Many of us change the kitchen sponge only once a month, or even less frequently. We probably wouldn’t leave the bathroom cleaning equipment so long without being changed.

A team of environmental engineers from the University of Florida has found that two minutes in a microwave can sterilise most household sponges after use, killing more than 99 per cent of the harmful bacteria that cause illness.

In a study published this week in the American Journal of Environmental Health, the researchers soaked sponges and scrubbing pads in dirty water that contained faecal bacteria such as E. coli, viruses, protozoan parasites and bacterial spores. They then used a common household microwave oven to heat up the sponges. It took between four and ten minutes to kill all the spores, but everything else was killed after two minutes, they said.

There are more than nine million cases of gastroenteritis each year in England, caused by eating or drinking products contaminated by micro-organisms or germs. Gastroenteritis describes symptoms affecting the bowel, such as nausea, vomiting, diarrhoea and stomach pain.

Whereas the use of disinfectants is common in bathrooms, kitchen cleaning still relies heavily on soap and water.

Gabriel Bitton, a professor of environmental engineering who led the study, said: “People often put their sponges and scrubbers in the dishwasher, but if they really want to decontaminate them, and not just clean them, they should use the microwave.”

Professor Bitton said that cooks should consider the benefits of microwaving their sponges and dishcloths every other day.

For the entire sponge to get hot enough to kill bacteria, he said that it needed to be damp — not dripping, but damp enough to attract microwaves and transfer heat. It should be left in the microwave oven for two minutes or until it was steaming.

Most bacteria, including E. coli and salmonella, are killed at about 71C (160F).

Professor Bitton said that the technique could also be used to sterilise syringes — but emphasised that it took up to 12 minutes in a microwave oven to kill the bacteria on a needle.

“The microwave is a very powerful and an inexpensive tool for sterilisation,” he said.

Last year a poll by the Food and Drink Federation found that many people failed to replace their kitchen sponges regularly.

Enemy within

10,000 Number of bacteria that a germ-laden kitchen sponge may contain per square inch, including E. coli, salmonella, pseudomonas and staphylococcus

49 Number of microbes per square inch on the average lavatory seat

20,961 Number of microbes per square inch in the average office workspace

25,127 The key offenders are telephone receivers, which harbour up to 25,127 microbes per square inch, keyboards (3,295) and computer mice (1,676)

Source: University of Arizona/Times Database

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