Clostridium Difficile: 1st Place Winner 2010 AMT Technical Writing Contest

Article excerpt

Clostridium difficile is a gram positive, spore forming anaerobic bacillus, which may or may not carry the genes for toxin A-B production, first described by Hall and O'Toole in 1935 as an abundant normal bacterial flora of the intestine in infants. (15) Hall and O'Toole also recognized that this bacterial flora was toxigenic through animal studies. In 1978, they found that the toxins released by Clostridium were seen in the stools of patients with antibiotic-associated pseudomembranous colitis. (10)

The bacterium has two forms: an active infectious form and non-active, non-infectious form known as the spore. The infectious form can survive for a short duration of time in the environment. The spores can survive for a longer period of time in the environment and are not infectious unless and until they are ingested or are transformed into an infectious state. (3)

The spores are usually transmitted by fecal-oral route and are frequently seen in patients who have been staying long-term in a hospital or a nursing home. The spores can also be found in bedpans, furniture, floors, stethoscopes, diaper pails, and even carried by pets. (3)

Risk Factors for Clostridium difficile Associated Disease (CDAD)

According to Bignardi, (4) the risk for disease increases in patients with:

1. Antibiotic Therapy

More than 90% of health care associated C. difficile infections are seen during antibiotic exposure. (4), 6 Except for amino glycosides, most antibiotics have been associated with CDAD. The patients who are found to be at a greater risk are the ones who have drug therapies over a long period.

2. Age greater than 65 years

Older people have a high infection rate. They tend to have more health problems than younger people.

3. Severe underlying illness

Patients whose immune systems have been weakened are at greater risk of having recurrent infections.

4. Longer hospital stays or lives in a nursing home or long term care facility

5. Nasogastric intubation

6. Patients who have abdominal surgeries

7. Chronic colon disease such as inflammatory bowel disease or colorectal cancer

Pathogenesis

More than three million C. difficile infections occur in hospitals in the US each year. (3) The emergence of a new strain of C. difficile appears to be more virulent, and has the ability to produce large amounts of toxin A and B. It is also seen to be resistant to most commonly used antibiotics such as vancomycin, fluoroquinolones and metronidazole. (2) This strain is responsible for nearly all intestinal infections such as colitis that occurs after antibiotic therapy and intestinal infections like pseudomembranous colitis, toxic megacolon, perforation of the colon and sepsis. (1) Nosocomial CDAD is almost always associated with antimicrobial use. One should always try to avoid unnecessary and inappropriate microbial therapy.

As seen in figure 1, the development of CDAD and colitis relies on interaction between various processes. These include: 1) disruption of beneficial flora of the colon when antimicrobials are taken; 2) creation of a favorable environment for Clostridium to proliferate; 3) the bacteria secretion of toxins A and B, that leads to injury and inflammation of the mucosa, (15) although these events may not occur in order. (4) Once these events occur, the patient can become colonized and can develop CDAD. The organism can be ingested in vegetative form or as hardy spores. The vegetative cells could be killed by acid in the stomach, but the spores are resistant to acid and pass through the stomach into the small bowel. Primary bile acid in the small bowel initiates the germination of spores into vegetative forms. The exotoxins A and B, released by the organism, act on the bowel mucosal wall to cause diarrhea and colitis. Toxin A has a greater molecular weight than toxin B. The toxins exert their effect in the cytoplasm of the cell, leading to deregulation of proteins involved in cytoskeleton formation and signal transduction process. …