E Coli

Scary stories about E coli outbreaks appear in the news regularly. The most recent occurrence in Germany is worrisome because of the deaths of younger healthier women and the lack of an obvious source.

E coli is a resident bacteria of the human GI tract. One's personal inhabiting specie rarely causes problems. The proximity of the rectum and vagina in women make E coli a common cause of urinary tract infections. E coli may infrequentlt cause pneumonia and meningitis in neonates, long-term care residents and hospitalized patients. The bacteria may infect diabetic and decubitus (pressure sores) ulcers and causes up to 10% of bacterial bone infections in the vertebrae. The newsworthy danger arises when one is exposed to a strain of the bug that produces toxins that cause harm to the human host.

The most familiar of these toxin producing strains of E coli is the enterotoxigenic variety. Euphemisms such as traveler's diarrhea or Montezuma's revenge make the illness seem trivial. Bouts of watery diarrhea are no fun. Treatment however is relatively simple; rehydrate with fluids and Pepto Bismol in large quantities.

STEC/EHEC refers to strains of coliforms that produce a Shiga toxin. Shigella bacteria are another cause of gastrointestinal infection. The shiga toxin invades the lining of the intestinal tract and enters the blood stream. Unrelated species of bacteria may "share" genetic material by exchanging plasmids. Plasmids are packages of genes that may encode for resistance to antibiotics or production of a toxic protein.

Shiga toxin targets the endothelial cells that line blood vessels. The resulting damage is referred to as microangiopathy. The red blood cells and platelets (clotting cells) are injured as they pass through the damaged blood vessels. Hemolytic anemia (low RBC's from lysis or rupture) and TTP (low platelet counts from consumption of the platelets in clotting) cause the life-threatening consequences of HUS, hemolytic uremic syndrome.

The kidneys main function is filtering out toxic products from metabolism. They are highly vascular. In the kidney cells, the Shiga toxin inhibits protein synthesis, eventually leading to apoptosis (cell death). The lysis of RBC's, the direct damage to renal blood vessels and renal cell apoptosis may lead to kidney failure, i.e. HUS. If recognized early, intravenous fluids may prevent renal failure. Once established, renal failure is treated with hemodialysis until the kidneys recover. The kidney failure may be permanent and lead to a life of thrice weekly dialysis while awaiting a kidney transplant.

The early symptoms of STEC/EHEC are bloody stools, fever, lethargy, vomiting and weakness. Diarrhea, vomiting and increased irritability may be the only early symptoms in babies. Later in the course of the illness, patients may have bruising, decreased level of consciousness, low or no urine output, pallor, petechiae (small red or purple skin lesions) and jaundice. HUS is most common at the extremes of age. The very young and the elderly are usually most at risk.

In the USA, outbreaks of HUS from enteroinvasive strains of E coli have come from contaminated meat (especially hamburger) and vegetables contaminated by irrigation water that had been fouled by animal waste. Thoroughly cooking meat eliminates the risk but washing vegetables does not. There have been proposals to irradiate food products to kill the bacteria in and on the food. Irradiation does not make the food radioactive but it may alter the taste or texture of the food.

The most useful thing that we can all do to prevent the spread of food borne illnesses is good hand washing. Fecal-oral spread sounds gross but is all too frequently the source of both viral and bacterial gastroenteritis. Reminding children to wash their hands after going to the bathroom is a must. I have been tempted to expose people that I have seen leaving public bathrooms without washing their hands.

Use warm water, soap, and scrub for at least a minute, use paper towels to dry your hands and also to shut off the water and open the door. Any ground meat must be cooked completely. A hamburger with a red center is a "crap" shoot.