BEWARE Montezuma鈥檚 revenge. In Mexico鈥檚 restaurants and eateries there is more in the salsa to assault your digestion than just the hot peppers. Popular spicy condiments such as salsa, jalape帽o sauces and guacamole are contaminated with the bacteria that cause travellers鈥� diarrhoea.
Researchers from the University of Texas found E. coli in two-thirds of the condiments they tested from Mexico, and on average the levels of contamination were 1000 times what they measured in restaurants in Houston. What鈥檚 more, they repeatedly found two particularly virulent strains of E. coli that together account for half of all cases of traveller鈥檚 diarrhoea.
The bugs come from human faeces and contaminate the sauces via unwashed hands, says Herbert DuPont, an expert in infectious diseases and Chief of Internal Medicine at St Luke鈥檚 Episcopal Hospital in Houston.
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Travellers鈥� diarrhoea is a major health problem for tourists in developing countries. Every year about 20 million visitors to Latin America, South-East Asia and India get a bout of the runs due to contaminated food. 鈥淢ost people think it鈥檚 the water, but it鈥檚 not,鈥� says DuPont, who鈥檚 been testing food in Mexico and elsewhere for nearly three decades. He has found that bad food is responsible for about 90 per cent of travellers鈥� diarrhoea.
DuPont鈥檚 team collected tablespoon-sized samples of 71 sauces from 36 restaurants in Guadalajara and compared them with 25 sauces served in 12 Mexican-style restaurants in Houston. They cultured the samples and identified any microbes that grew. Of the many bugs that can cause food poisoning, they only found E. coli, but it was present in 66 per cent of the sauces from Guadalajara and 40 per cent of those collected in Houston. 鈥淭his is really surprising because we thought the sauces would be safe, since the acid content is quite high,鈥� says DuPont.
While none of the Houston samples contained dangerous strains of E. coli, sauces from Mexico commonly contained two that wreak havoc in the gut. One releases a toxin, and the latter causes inflammation. DuPont鈥檚 group found that 9 per cent of Mexican samples harboured the first kind, and 44 per cent the second (Annals of Internal Medicine, vol 136, p 884).
The Mexican restaurants in Houston are probably safer because they serve their condiments either freshly made or from the fridge. In Mexico, the same sauces sit on the table all day. Not only are they unrefrigerated, but many consecutive diners may stick their fingers in them, says DuPont.