At any one time, up to 30% of perfectly healthy people carry the bacterium Staphylococcus aureus, which lives in the human nose. In most cases, the bugs are harmless, but an antibiotic-resistant form of S. aureus is becoming more common. Methicillin-resistant S. aureus, or MRSA, can be difficult to treat, but there are ways to avoid infection, reports the November 2008 issue of Harvard Men's Health Watch.

S. aureus can lead to pneumonia if it gets into the lungs. It can cause boils, abscesses, or serious infections of the skin and underlying tissues. It can even invade the bloodstream to cause life-threatening illness. Fortunately, these major infections are uncommon.

When penicillin was discovered in the 1940s, virtually all strains of S. aureus were vulnerable to this new antibiotic. But within a decade, bacterial mutants that could resist penicillin began to emerge. In 1959, scientists developed methicillin, an antibiotic that was able to kill penicillin-resistant S. aureus. Methicillin and its derivatives quickly gained widespread use. And, as with penicillin, staph learned how to resist methicillin and similar drugs, becoming methicillin-resistant S. aureus — or MRSA.

MRSA behaves much like other staph, usually existing in the nose or on the skin without causing disease, sometimes causing mild infections, and occasionally causing life-threatening ones. MRSA is vulnerable to special antibiotics. Doctors usually rely on vancomycin to treat hospitalized patients, but there are other useful drugs.

MRSA is a tough problem, and it shows signs of getting tougher. Here's how you can protect yourself and your family:

• Wash your hands frequently, with soap and water for at least 15 seconds or an alcohol-based rub.
• Don’t share personal items like razors or towels.
• Avoid direct contact with infected individuals.

Notify your doctor if you develop a skin infection or another problem that could signal MRSA.