Superbugs and Antibiotics: A Deadly Dance

Clostridium difficile, a contagious and potentially deadly pathogen, isn't just increasingly resistant to antibiotics. It's often triggered by antibiotic treatment.

An article in the Cleveland Clinic Journal of Medicine describes the bacterium, also known as C-diff, as a gram positive, spore forming bacillus that was first linked to disease in 1978 when it was identified as the cause of antibiotic-associated diarrhea and colitis. The February 2006 article, by Rebecca Sunshine, MD and L. Clifford McDonald, MD, says that more than 90 percent of healthcare associated C-diff cases occur after a patient has received antibiotic treatment for some other illness. The story is posted in the website of the federal Centers for Disease Control and Prevention.

Treatments with antibiotics are likely to disturb the bacteria that normally live in the digestive tract and colon. If a person's exposure to C-diff coincides with that that disruption, the C-diff bacteria flourishes and releases toxins that are harmful to humans.

An April 14 story in The New York Times by Tara Parker Pope reports that health authorities estimate C-diff causes 350,000 infections each year in hospitals alone, with tens of thousands more in nursing homes, and that 15,000 to 20,000 people die annually from the infection. C-diff spores are hardy and live on environmental surfaces and people's hands and clothing. They are not killed by alcohol based hand sanitizers and hospital cleaning agents. It takes bleach to kill them, which increases the difficulty of eradicating them.

A national prevalence study of C-diff conducted by the Association for Professionals in Infection Control and Epidemiology (APIC) indicated 13 of every 1,000 patients in US healthcare institutions are infected or colonized with C-diff. Based on that rate, on any given day at least 7,178 patients are infected or colonized, at a cost that could range from $17.6 million to $51.5 million. The APIC study, released in November 2008, reported the C-diff incidences rate is between 6.5 and 20 times greater than previous incidence estimates indicated. The Times story notes C-diff now rivals MRSA as one of the top emerging disease threats to humans.

While C-diff has become increasingly virulent and increasingly resistant to antibiotics, recent research findings may lead to better treatment. A March 1, 2009 story in ScienceDaily reports that C-diff manufactures different toxins, and that researchers may have focused on the wrong one. Dr. Dale Gerding, a co-author of the study, published in the journal Nature, explained that while researchers have focused on Toxin A, recent research shows the real culprit is Toxin B. Gerding and colleagues found that the organism was fully virulent and caused disease when Toxin A was knocked out, but did not cause disease when Toxin B was eliminated. Researchers think understanding the relative importance of the two toxins could help pave the way for new methods to combat deadly C-diff infections.