MRSA

MRSA, or methicillin-resistant Staphylococcus aureus, is a strain of Staphylococcus aureus resistant to most beta-lactam antibiotics, due to the mecA gene encoding an altered penicillin-binding protein (PBP2a). MRSA commonly colonizes the skin and nasal passages without symptoms but can cause infections ranging from skin and soft-tissue infections to pneumonia, bloodstream infections, and surgical wound infections.

MRSA is spread by direct contact and contaminated surfaces. Risk factors include recent hospitalization, surgery, indwelling devices, crowded living conditions, and immune compromise. Two major forms exist: healthcare-associated MRSA (HA-MRSA), seen in hospital or long-term care settings, and community-associated MRSA (CA-MRSA), occurring in otherwise healthy people and often causing skin infections.

Diagnosis relies on culture and susceptibility testing; rapid molecular tests may detect resistance. Treatment depends on severity. Minor skin infections may be treated with incision and drainage plus antibiotics active against MRSA (for example doxycycline, trimethoprim-sulfamethoxazole, or clindamycin, considering resistance). More severe infections may require intravenous agents such as vancomycin, linezolid, or daptomycin, guided by susceptibility. Decolonization is considered only in select cases.

Prevention centers on hand hygiene, proper wound care, and avoiding shared personal items. In healthcare settings, contact precautions and cleaning reduce transmission.