MRSA, Other Superbugs Continue To Threaten Health
A 50 percent decline in hospital acquired cases of methicillin resistant Staphyloccus aureus (MRSA) in the past year could be seen as encouraging news except for the fact that other superbugs, such as antibiotic-resistant gram negative rods are beginning to emerge in hospital settings. In addition, cases of community-acquired MRSA, especially in children, are reported to be on the rise.
The decline in MRSA infections in the hospital setting can largely be attributed to the more rigid infection control standards that have been implemented over the past year. Handwashing has been emphasized in required infection control courses required by all hospital employees in the United States. Counter surfaces and medical equipment are regularly disinfected and surgery suites are routinely cultured to ensure a sterile environment.
The first cases of MRSA were confined to hospital settings. In 2007, CDC surveillance studies identified MRSA as the cause of more than 94,000 serious infections and close to 19,000 deaths annually. Most deaths were due to infections of central lines and indwelling catheters. Reducing hospital acquired infection rates is a victory but additional measures are needed to control the spread of MRSA in the community. Community acquired infections with MRSA can be more serious because they are frequently not diagnosed until they're life threatening.
MRSA strains identified as community acquired differ from hospital‐acquired MRSA strains in that they are generally susceptible to most other antibiotics. Community acquired strains share the presence of the staphylococcal chromosome mec (SCCmec) type IV in their genomes, are frequently virulent, and predominantly cause skin and soft tissue infections. The genome sequence of the prototypic community acquired MRSA strain, MW2, is accompanied additional virulence factors not commonly present in other S. aureus strains. While not as threatening as infections of the blood, infections of tissue with community acquired MRSA can also be fatal.
Community acquired MRSA infections have been linked to recent hospitalizations in patients or their family members. Studies show that many people are colonized with MRSA although they're not infected. Carriage rates of MRSA in the general population range from 25% to 50%; higher rates than in the general population are observed in injection drug users, persons with insulin-dependent diabetes, patients with dermatologic conditions, patients with long-term indwelling intravascular catheters, and health-care workers. Children are also reported to have higher rates of colonization because of their frequent exposure to respiratory secretions. Risk factors for MRSA are the same as risk factors for S. aureus infection including shared towels, shared exercise equipment and toys, gymnasium and playground settings and crowded living conditions. Fatalities in children and young athletes have been well publicized in recent years although these infections were first reported among drug users in the 1980s.
A recent report from the Infectious Diseases Society of America shows that antibiotic resistant gram negative bacterial infections are also on the rise. Although they're primarily confined to the hospital setting they've also been seen in patients treated in an outpatient setting. Gram negative infections are alarming because, unlike MRSA, they're generally resistant to all available antibiotics, with the exception of Colistin, which can damage the kidneys. The January 2009 death of Brazilian model Mariana Bridi da Costa, after a series of amputations that could not stop the spread of her gram negative bacterial infection, is an example of just how serious this threat is.