Antibiotic Resistant "Superbug" on the Rise

A particular variety of common bacterium is becoming ever more resistant to antibiotics, causing potentially serious problems for people who are already at increased risk for infection. Staphylococcus aureus, often referred to simply as "staph" bacteria, are commonly carried on the skin or in the noses of healthy people.

But some Staphylococcus aureus are resistant to the antibiotics - such as methicillin - that are frequently used to treat staph, and thus are called methicillin-resistant Staphylococcus aureus, or MRSA. Currently in the US, there appears to be at least three different strains of staphylococci that can cause MRSA infections. These organisms, which can resist several different antibiotics, are causing problems for a vulnerable population.

Mohammad Almoujahed, MD, Medical College of Wisconsin Assistant Professor of Medicine (Infectious Diseases) notes that it's not difficult to spread antibiotic-resistant bacteria once it's taken hold.

"MRSA can be acquired by direct contact with patients who have the bacteria on their skin, or by droplet spread from a patient who has MRSA in the nose or airways," he explains. "Having the bacteria on the skin or in the nose and airways can occur without symptoms; this is called MRSA colonization and people who experience it are said to be MRSA carriers. Only patients with symptoms are said to be MRSA-infected."

Perhaps the most important issue in regard to MRSA is the overuse of antibiotics. Dr. Almoujahed explains that this is leading to the emergence of resistant bacteria like MRSA. "The genetic makeup of MRSA that made it resistant to multiple antibiotics, gave it a survival advantage over the more drug-susceptible staphylococcus aureus strains that were more efficiently killed by commonly-used antibiotics. That was what made the naturally resistant bacteria (MRSA) become more prevalent."

Dr. Almoujahed recommends that patients don't insist on receiving antibiotics unless their health care provider believes they are definitely called for. Many people feel their doctors are obliged to offer them something to make them feel better, even if their illness is viral. Common colds, for instance, are caused by viruses, not bacteria. Antibiotics will do nothing to relieve cold symptoms, but could provide an environment in the body that encourages future antibiotic resistance.

Symptoms
"The symptoms experienced by MRSA-infected patients vary somewhat depending on the part of the body that's been infected," says Dr. Almoujahed. "Surgical wound infection results in pain, redness and swelling of the surgical site and occasionally the wound may drain pus. MRSA pneumonia causes cough, shortness of breath and chest pain. Fever, chills, and sweats can be present in infection of all sites."

Diagnosis and Treatment
"The routine way of diagnosing MRSA is by culture of material from the infected site, such as pus, sputum, or blood," explains Dr. Almoujahed. Once the staph is growing, the organism is tested to determine which antibiotics will be effective for treating the infection.

Unfortunately, only a limited number of antibiotics are effective against MRSA, according to Dr. Almoujahed. "Intravenous vancomycin is the most common antibiotic used to treat serious MRSA infections. For less severe infections, other antibiotics can be used, depending on the MRSA strain. Often, surgical drainage of formed abscesses is needed in addition to antibiotics."

MRSA infections often start as mild, superficial infections of the skin that can be treated successfully with proper skin care and antibiotics. However, MRSA can progress to life-threatening blood or bone infections because there are fewer effective antibiotics available for treatment.

"MRSA infections must be treated appropriately," Dr. Almoujahed says. "Untreated or inadequately treated MRSA infections can result in severe consequences, relapse of infection, and even death."

Not Just in Hospitals
"MRSA infection is significantly more common in hospitalized patient than in patients who become sick in the community," says Dr. Almoujahed. "And certain hospitalized patients are at even higher risk for MRSA infection; these include patients with prolonged hospitalization, patients in the intensive care unit, patients who undergo surgical procedures, patients with central venous catheters including patients with chronic kidney failure who receive hemodialysis, and patients who receive multiple courses of antibiotics." Patients with weakened immune systems, the elderly, and patients who receive multiple courses of antibiotics may also be at higher risk.

But MRSA is becoming more common in the community too. People who use illegal injection drugs, especially those who share needles, are at higher risk for MRSA infection. Additionally, men who have sex with men, prison inmates, residents of long-term care facilities and children who attend child-care facilities are also at higher risk.

In recent years, MRSA has been seen more often among sports participants. The CDC reports several possible reasons for this transmission. Competitive sports participants might develop abrasions and other skin trauma where bacteria can enter. Even in sports with less direct contact, protective clothing can be hot and might chafe skin, resulting in abrasions and lacerations.

In addition, some sports in which MRSA infections have been reported involve frequent physical contact among players (such as football, wrestling, and rugby). And finally, sports such as fencing have limited skin-to-skin contact but require multiple pieces of protective clothing and equipment, are often shared. The use of shared equipment or other personal items that are not cleaned or laundered between users could be a vehicle for Staphylococcus aureus transmission.

MRSA Prevention
Obviously, MRSA transmission control measures are vital, particularly in environments where bacteria are likely to spread among groups. Preventive measures include:

• improving hand and body hygiene
• covering cuts and abrasions with bandages until healed
• laundering personal items such as towels and athletic supporters after each use
• cleaning or laundering shared athletic equipment such as pads or helmets at least once a week, but ideally after each use
• consulting a health-care provider for wounds that do not heal or appear infected

In addition to these prevention measures, Dr. Almoujahed recommends that if you have a fever and localized symptoms suggestive of infection (i.e. surgical wound redness, swelling and pain) you should consult with your health care provider as soon as possible. Also, hospitalized patients should welcome being discharged from the hospital as soon as they are medically stable, because prolonged hospital stay could increase the risk of MRSA and other infections.

P.J. Early
HealthLink Contributing Writer

This article includes information from the Centers for Disease Control and Prevention.

MCW Health News presents up-to-date information on patient care and medical research by the physicians of the Medical College of Wisconsin.