Vancomycin Resistant MRSA
Antibiotic Resistant Bacteria Are Getting Difficult To Treat
Since the discovery of penicillin, bacteria have shown increasing resistance to treatment. Now, the future of the few options remaining are in question.
At a New York Academy of Science meeting on emerging and re-emerging microbial diseases in late 2004, Dr. Barry Kreiswirth from the Public Health Research Institute presented information about methicillin-resistant Staphylococcus aureus (MRSA), an antibiotic resistant bacterium. Of particular concern were the first cases of vancomycin-resistant MRSA (VR-MRSA) seen by researchers in 2002.
Methicillin-Resistant Staph
According to a 2007 report from the U.S. Centers for Disease Control (CDC) evaluating infection data from eight metropolitan areas in 2005, there are approximately 19,000 deaths in the U.S each year from MRSA, fifteen percent of which are estimated to be due to a community strain, as opposed to the hospital strain first seen. The agency cautions that the figure may be higher than the actual number of deaths, due to the population density of the monitored areas, but the information suggests that the MRSA-associated death rate doubled in only 5 years.
S. aureus usually colonizes the skin and is present on the surface of one third of all people. Most infections stay confined to the skin, but open wounds and surgical incisions can allow the bacterium to enter and gain access to the internal organs or bloodstream, leading to sepsis. Therefore, MRSA is usually seen in those who have invasive surgery or reduced immunity. Hospital-acquired, or nosocomial, infections tend to be invasive more often than community strains, those that appear with no health care factor. The first community strains were seen in intravenous drug users in 1981 at the same time MRSA was becoming rampant in hospitals, and the first deaths attributed to a community MRSA strain were four schoolchildren in Minnesota in 1997.
Nosocomial Infection Risk
The elderly, and those who stay in the hospital often, are at a higher risk of suffering from antibiotic resistant infections, since the more virulent strains often circulate in the healthcare system. Based on information from the CDC, approximately 65% of hospital-based S. aureus infections were methicillin resistant in 2003 and 8.2% of nosocomial bacteremias, bacterial infections, can be expected to be MRSA. A total of 75% of nosocomial infections are drug resistant and hospital acquired infections result in 100,000 deaths annually. More diligent hand-washing and sterilization may be able to cut the numbers.
Developing Antibiotic Resistance
Since penicillin was identified as an antibiotic in 1941 and gained consistent use, resistance to treatment began to appear. Bacteria acquire DNA sequences from other bacteria with which they come into contact, sharing resistance genes. For example, if methicillin-resistant bacteria come into contact with vancomycin-resistant bacteria (such as Enterococcus faecalis), they can both potentially become double resistant to both antibiotics and replicate into a double resistant strain upon circulation. Today only vancomycin is effective against MRSA strains, but in 2002 VR-MRSA was seen in two U.S. states, and a third instance occurred in a long-term care facility in NY a year later. Some evidence in scientific journals indicates that cocolonization of patients with MRSA and VR-Enterococci is currently occurring, which does not bode well for the future of antibiotics.
Additional sources:
- Furuno, et al. Methicillin-resistant Staphylococcus aureus and Vancomycin-resistant enterococci Co-colonization. Emerging Infectious Diseases 11(10);1539-1544, 2005.
- U.K. Health Protection Agency - CDR weekly news archives
