Methicillin-Resistant Staphylococcus Aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is a mutation of a very common bacterium that is spread easily by direct person-to-person contact. Once limited to large teaching facilities and tertiary care centers, MRSA is now endemic in nursing homes, long-term care facilities. and even community facilities.

MRSA has become prevalent with the overuse of antibiotics. Over the years, overuse has given oncesusceptible bacteria the chance to develop defenses against antibiotics. This new capability allows resistant strains to flourish when antibiotics knock out their more sensitive cousins.

Causes

MRSA enters a health care facility through an infected or colonized (symptom-free, but infected) patient or colonized health care worker. MRSA has been recovered from environmental surfaces, but it's transmitted mainly on health care workers' hands. Many colonized individuals become silent carriers. The most frequent site of colonization is the anterior nares (40% of adults and most children become transient nasal carriers). The groin, axilla, and gut are less common colonization sites. Typically, MRSA colonization is diagnosed by isolating bacteria from nasal secretions.

If a person's natural defense system breaks down, such as after an invasive procedure, trauma, or chemotherapy, the normally benign bacteria can invade tissue, proliferate, and cause infection. Today, up to 90% of S. aureus isolates or strains are penicillin-resistant, and about 27% of all S. aureus isolates are resistant to methicillin, a penicillin derivative. These strains may also resist cephalosporins, aminoglycosides, erythromycin, tetracycline, and clindamycin.

Patients most at risk for MRSA include immunosuppressed patients, burn patients, intubated patients, and those with central venous catheters, surgical wounds, or dermatitis. Others at risk include those with prosthetic devices, heart valves, and postoperative wound infections. Other risk factors include prolonged facility stays. extended therapy with multiple or broad-spectrum antibiotics, and close proximity to those colonized or infected with MRSA. Also at risk are patients with acute endocarditis, bacteremia, cervicitis, meningitis, pericarditis, and pneumonia.

What are the symptoms of MRSA?

Methicillin-resistant staphylococcus aureus produces symptoms no different from any other type of Staphylococcus aureus bacteria. The skin will appear red and inflamed around wound sites. Symptoms in serious cases may include fever, lethargy, and headache. MRSA can cause urinary tract infections, pneumonia, toxic shock syndrome, and even death.

Diagnostic tests

MRSA infections can be diagnosed when a doctor obtains a sample or specimen from the site of infection and submits it to a laboratory. The laboratory places the specimen on a special "culture" plate containing nutrients, incubates the plate in a warmer and then identifies the bacteria. The final step is for the laboratory to conduct tests using various antibiotics to determine if the bacteria are resistant (able to withstand or tolerate) or sensitive (susceptible to killing) to select antibiotics.

Treatment

To eradicate MRSA colonization in the nares, the doctor may order topical mupirocin applied inside the nostrils. Other protocols use a topical agent in combination with an oral antibiotic. Most facilities keep patients in isolation until cultures are negative.

To attack MRSA infection, vancomycin is the drug of choice. A serious possible adverse effect caused mostly by histamine release is itching ranging to anaphylaxis. Some clinicians also add rifampin, but whether rifampin acts synergistically or antagonistically when given with vancomycin is controversial.

Prevention

There is no vaccine to protect you from MRSA. The most important thing you can do is wash your hands before eating, drinking, smoking or applying personal care products, and after using the toilet. Wash your hands well for at least fifteen seconds using warm water and soap, and use a paper towel to dry your hands.

Bacteria can survive on surfaces like railings, faucets and handles for up to seven days. Routine cleaning of these surfaces with regular household cleaners can also help reduce spread of bacteria.