Dear Doctor: A friend of mine was diagnosed with methicillin-resistant Staphylococcus aureus, or MRSA. How does a person even contract such a disease -- and what does it do to you?
Dear Reader: Methicillin-resistant Staphylococcus aureus, or MRSA, is a bacterium that is resistant to methicillin and other penicillin-related antibiotics. These drugs normally bind to a specific protein on the bacterium, leaving it unable to produce a cell wall. MRSA, however, has a gene that produces a protein that doesn't bind to methicillin or its cousins, making it harder to defeat.
People can acquire MRSA in two ways. One is through a health care setting, either in a hospital, nursing facility, surgical center or dialysis facility. Infections acquired in those settings can manifest between 48 hours and a year after exposure. They're more likely if a patient is over-prescribed penicillin-related antibiotics (making them more resistant to the drugs); is in a room or setting next to somebody with a MRSA infection; or is on dialysis. Although hospitals take painstaking measures to ensure a sterile environment free from harmful bacteria, MRSA forms a biofilm that attaches to inert objects, such as catheters and breathing tubes. From there, it can more easily invade the body. It can also attach to the hands of health care workers and many surfaces, and, from there, make its way to patients.
The second way to acquire MRSA is within the community. Outbreaks have been noted among sports teams, in childcare centers, among military personnel and in prison populations. Even animals can carry the bacterium and pass it on to a human host. Such cases are predominately skin infections, including cellulitis, folliculitis and abscesses. The bacterium can also be passed among household members. A 2012 study of 148 MRSA-infected patients found that 19 percent of their household contacts had colonized the bacteria.
In humans, MRSA colonizes within the nose, within the throat and upon the skin. That doesn't mean it causes infections, but rather that it's lurking there, ready to cause an infection should a person's immunity be compromised. From there, it can also spread to others, who may be more susceptible. A 2010 study of hospitalized patients found that 7 percent had colonized MRSA. In two 2008 studies of health care workers in the emergency room, between 4 and 15 percent had colonized MRSA within their nose.
MRSA not only causes skin infections, but can lead to pneumonia, infections of the bone and within joints, infections of the heart valves, and urinary tract infections. The infections can seep into the blood and pass to multiple organs. In 2005, MRSA led to an estimated 18,500 deaths in the United States.
All is not lost, however. The spread of MRSA can be controlled in hospitals and outpatient clinics if health care workers wash their hands after seeing patients, and if they use gloves and masks when seeing patients with MRSA. In households with a MRSA-infected family member, residents should be extremely diligent about hand-washing. The antiseptic chlorhexidine is especially effective at removing the bacteria from the skin. Further, those diagnosed with colonized MRSA in the nose can take the nasal antibiotic ointment Mupirocin.
Also, I'll say it again: Limiting the use of antibiotics will decrease the chance of bacterial resistance to them -- and decrease the chance of MRSA.
(Send your questions to firstname.lastname@example.org, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)