Bacteria In General
	By: Audrey Blanco, Registered Technologist, Dept. of Clinical Microbiology, Royal University Hospital Audrey Blanco is a Registered Technologist, Department of Clinical Microbiology at Royal University Hospital, Saskatoon, Saskatchewan

The microscopic world around us is so vast that if every living thing and every non-living object were to suddenly disappear, except for the microscopic life, you would still be able to see the outline of everything that was gone. That's a lot of microscopic life. Without these organisms every other living being would soon die. As human beings we depend on our bacteria to perform many biological functions for us and to protect us from disease. “Protect us from disease?” you may say “I thought bacteria caused disease.” Well some do, but there is a balance that we have to achieve in our bodies. The billions of bacteria that live with us (and our pets) in harmony are called our normal flora. Normal flora are essential to our health in several different ways: They protect us from invasion by disease-causing bacteria by using up the nutrients that disease-causing bacteria need. Their waste products are sometimes toxic to disease-causing bacteria, thus preventing their growth. They stimulate our immune systems to keep them active. They help to digest our food and release the nutrients that our bodies need. They produce vitamin K and certain B vitamins in our intestines. This function is performed by billions of E. coli bacteria in our intestines. Yes, E. coli can be good.

Salmonella

Salmonella organisms are found in the intestines of virtually all animals, including poultry, reptiles, livestock, rodents, birds and humans. Animal-to-animal spread and Salmonella-containing animal feed maintain the reservoir. The most common sources of human infection are poultry, eggs, dairy products, and foods prepared on a contaminated work surface. Humans are exposed to Salmonella bacteria on a regular basis, although most of us have never suffered disease due to exposure. Our main defense against disease with Salmonella is our stomach acid. Salmonella is very sensitive to and dies easily in the presence of acid. A dog's stomach is much more acidic than ours, so they have even more protection. Human beings need to consume a whopping dose of Salmonella in order to get sick, as most organisms are killed in the stomach. The number is somewhere in the order of 100,000,000 Salmonella bacteria. These amounts are not usually present in food that has been handled properly. Purchasing your raw meat from a reputable source should mean that it was kept at appropriate temperatures before delivery to you. Proper storage of meat after purchase should eliminate any further problems.

Campylobacter

Campylobacter infections can be acquired from consuming contaminated food, milk or water. Eating undercooked, contaminated poultry products causes over half of all Campylobacter infections in humans. The disease caused by this organism is not as serious as from Salmonella, and usually resolves without treatment. Once again, the severity of the disease is determined by the number or bacteria consumed. Campylobacter is the most common cause of bacterial food poisoning. Symptoms of the disease include diarrhea, malaise, fever and abdominal pain. Symptoms usually resolve within a week without treatment and long-term complications are extremely rare. I find it interesting that the domestic dog, as well as the chicken, carries Campylobacter in its intestines normally. This means that many of us who share our lives with dogs have in fact been exposed to these bacteria on a day-to-day basis. It is also interesting that I have not heard of a single case of Campylobacter disease contracted from exposure to the family dog, although I understand that they have been reported in the literature.

E. coli 0157-H7

Since the incident in Walkerton, Canada, the mention of E. coli tends to strike fear into people's hearts. There are thousands of strains of E. coli. E. Coli 0157-H7 is only one strain, and a fairly rare strain at that. It is not carried by chickens, but by cattle and other large grass-eating animals. Very few cattle carry these bacteria and then only in their intestinal tract, not in the muscle meat. Slaughterhouses check for these bacteria, which is why there is the occasional recall of ground beef. The reason that ground beef is the major culprit is that sometimes intestinal contents contaminate the muscle meat during the slaughter process. The surface of the muscle meat becomes contaminated. Then during grinding of ground beef, the entire batch can become contaminated. Unpasteurized fruit juices from orchards that may have been contaminated with cattle feces can also be a source.

SOURCES Murray, Rosenthal, Kobayashi, Pfaller, Medical Microbiology, Mosby, Inc. 1998 2. Nester, Roberts, Pearsall, Anderson, Nester, Microbiology-A Human Perspective, McGraw-Hill, 1998