Bedside Reading

Maryn McKenna is the author of a new book released yesterday, "Superbug: The Fatal Menace of MRSA," on the hospital, community, and environmental dangers of methicillin-resistant Staphylococcus aureus. McKenna, a science and medical journalist with the University of Minnesota's Center for Infectious Disease Research and Policy, discussed the book yesterday on NPR's Fresh Air with Terry Gross. You can listen to the interview here or read the transcript online.

In the interview, McKenna discusses the increased complication in treating MRSA infections due to crossover between what were originally separate healthcare-associated and community-associated MRSA strains. Now, she says, strains that were typically isolated to the hospital or to community settings (prisons and locker rooms, for example) are showing up in unexpected places and behaving in unexpected ways. As a result, doctors are not sure what the drug-resistance pattern of a given infection is -- and as a result, rely on prescribing the most intense drugs available. She also explains the dangers of low-dose antibiotics in farm animals, and the possibility of MRSA being transferred from animals to humans. Although she acknowledges that preventing the spread of MRSA and the development of resistance in general is difficult given the overprescription and overuse of antibiotics, as well as MRSA's resilience as an organism, McKenna does recommend a few things people can do to protect themselves: wash your hands, make sure your kids shower after sports, and use antibiotics appropriately.

Image courtesy of www.npr.org

World TB Day

March 24 is World TB Day. Tomorrow marks the 128^th anniversary of the discovery of Mycobacterium tuberculosis, the bacterium that causes tuberculosis, by the German physician and microbiologist Robert Koch.

Tuberculosis has largely faded from public consciousness in the United States. Annually there are now fewer than 13,000 cases of TB and fewer than 1,000 deaths in the U.S., less than half of the TB burden 30 years ago. But in developing nations, TB is more dangerous than ever, where multidrug-resistant (MDR) strains drain medical and economic resources and kill millions of people.

Last week, the World Health Organization (WHO) published a new report on multidrug- and extensively drug-resistant TB, reporting 440,000 cases of MDR-TB worldwide in 2008. In total, there were 9.4 million new TB cases and 1.8 million TB deaths in 2008.

MDR-TB is defined as a strain of tuberculosis that is resistant to at least isoniazid and rifampicin, two first-line TB drugs. It can develop in an individual patient when drugs are misused – as is common with TB treatments because they require months of administration – or when a resistant strain is passed between people. MDR-TB takes longer to treat than drug-susceptible infections, and it also costs a lot more to treat: up to $5,000 per case, compared to $20 for susceptible TB. The WHO reports that in some regions MDR-TB makes up more than a quarter of new TB diagnoses, and almost half of all cases come from China and India. Mistreatment of MDR-TB can lead to an even more dangerous and costly condition, extensively drug-resistant (XDR) tuberculosis, which is resistant to both first- and second-line treatments.

With resistant TB strains persisting and representing a growing share of new diagnoses, development of new treatments is essential. Last week, the Global Alliance for TB Drug Development, the Critical Path Institute and the Bill & Melinda Gates Foundation announced a new initiative that aims to make these treatments available sooner. The Critical Path to TB Drug Regimens will test combinations of early development TB drugs from a range of pharmaceutical companies, including Johnson & Johnson, Pfizer and GlaxoSmithKline in an attempt to identify the best possible treatment regimens coming out of the pipeline (read the press release here). This could drastically reduce the time to market for these drug regimens, but in order for new drugs to remain effective they must be used in a way that prevents the development of resistance. The U.S. battle with TB may be winding down, but it is only intensifying worldwide.

See the CDC website for information on World TB Day activities as well as e-Cards to spread TB awareness.

Image courtesy of www.cdc.gov

More on CDIs

If there is a pathogenic face to antibiotic resistance, it's MRSA, or methicillin-resistant Staphylococcus aureus. It can be gross and gory, affects both the elderly in nursing homes and children on athletic teams, and causes more deaths in the U.S. each year than AIDS. But is it the infection you should be most worried about during a hospital stay?

New research suggests that Clostridium difficile infections (CDIs) may be overtaking MRSA as the most threatening of the antibiotic-resistant infections the American healthcare system faces. Scientists affiliated with Duke's Infection Control Outreach Network (DICON) presented a study at last weekend's Fifth Decennial International Conference on Healthcare- Associated Infections that found CDI rates in excess of MRSA infections in community hospitals in the Southeast United States. In this group of 30 hospitals, which were monitored from January 2008 through June 2009, C. difficle was the leading healthcare-associated infection (HAI). C. difficile beat out MRSA, 612 cases (0.26 per 1,000 patient-days) to 505 cases (0.22 per 1,000 patient-days).

Previous studies also suggest that the mortality rate for CDI is higher than MRSA. But it's also possible that CDI is more preventable, because it is so closely linked to previous antibiotic usage in each individual patient, and largely confined to healthcare settings (except in pediatrics - see "CDIs Increasing in Children" below). This is one case where effective infection control and prevention strategies, as well as public education, could go a long way. You can learn more about C. difficile from the CDC and the Mayo Clinic.