Health officials say consumers should not eat fresh bagged spinach, after 20 states reported dozens of new cases of E. coli, including one that ended in death.
Here are some guidelines from the Food and Drug Administration and the Centers for Disease Control and Prevention for food preparation to help you reduce the risk of bacterial contamination:
Fresh fruits and vegetables can be contaminated if they are washed or irrigated with water that is contaminated with animal manure or human sewage.
During food processing, other foodborne microbes can be introduced from infected humans who handle the food, or through cross contamination from some other raw agricultural product.
The way that food is handled after it is contaminated can also make a difference in whether an outbreak occurs. Many bacterial microbes need to multiply to a larger number before enough are present in food to cause disease. Given warm moist conditions and an ample supply of nutrients, one bacterium that reproduces by dividing itself every half hour can produce 17 million progeny in 12 hours.
As a result, lightly contaminated food left out overnight can become highly infectious by the next day. If the food were refrigerated promptly, the bacteria would not have multiplied at all. In general, refrigeration or freezing prevents virtually all bacteria from growing but generally preserves them in a state of suspended animation.
Fruits and vegetables consumed raw are a particular concern. Washing can decrease but not eliminate contamination, so the consumers can do little to protect themselves.
What can consumers do to protect themselves from foodborne illness in fruits and vegetables?
For now, the FDA says do not eat any bagged spinach. They say washing alone may not clear off all the E. coli bacteria.
Other vegetables and fruit: Washing is the best bet. Thoroughly wash all fresh fruits and vegetables, especially those that are to be eaten raw, in running tap water to remove visible dirt and grime.
Remove and discard the outermost leaves of a head of lettuce or cabbage. Because bacteria can grow well on the cut surface of fruit or vegetables, be careful not to contaminate these foods while slicing them up on the cutting board, and avoid leaving cut produce at room temperature for hours.
Children under 5 years old, those whose immune systems are compromised, and the elderly should avoid eating alfalfa sprouts until their safety can be assured. Methods to decontaminate alfalfa seeds and sprouts are being investigated.
And don't be a source of foodborne illness yourself. Wash your hands with soap and water before preparing food. (E. coli often spreads through feces.) Avoid preparing food for others if you yourself have a diarrheal illness. Changing a baby's diaper while preparing food is a bad idea that can easily spread illness.
What can you do to prevent an E. coli O157:H7 infection?
Cook all ground beef and hamburger meat thoroughly. Because ground beef can turn brown before disease-causing bacteria are killed, use a digital instant-read meat thermometer to ensure thorough cooking.
Ground beef should be cooked until a thermometer inserted into several parts of the patty, including the thickest part, reads at least 160 degrees. Those who cook ground beef without using a thermometer can decrease their risk of illness by not eating ground beef patties that are still pink in the middle.
If you are served an undercooked hamburger or other ground beef product in a restaurant, send it back for further cooking. You may want to ask for a new bun and a clean plate, too.
Avoid spreading harmful bacteria in your kitchen. Keep raw meat separate from ready-to-eat foods. Wash hands, counters and utensils with hot soapy water after they touch raw meat. Never place cooked hamburgers or ground beef on the unwashed plate that held raw patties. Wash meat thermometers in between tests of patties that require further cooking.
Drink only pasteurized milk, juice or cider. Commercial juice with an extended shelf life that is sold at room temperature (juice in cardboard boxes, vacuum sealed juice in glass containers) has been pasteurized, although this is generally not indicated on the label. Juice concentrates have also been heated sufficiently to kill pathogens.
Drink municipal water that has been treated with chlorine or other effective disinfectants.