MRSA ST398

Methicillin-resistant Staphylococcus aureus (MRSA)

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Scanning electron micrograph of MRSA bacteria.

Methicillin-resistant Staphylococcus aureus (MRSA) is a bacterium that is resistant to many antibiotics, including methicillin, penicillin, and amoxicillin. MRSA is a type of Staphylococcus aureus, a common bacterium that can cause a range of illnesses, from minor skin infections to life-threatening diseases such as pneumonia, bloodstream infections, and surgical site infections.

History

MRSA was first discovered in 1961 in the United Kingdom, shortly after the introduction of methicillin. It has since become a major public health concern due to its resistance to multiple antibiotics and its ability to cause outbreaks in healthcare settings and the community.

Epidemiology

MRSA infections are more common in hospitals and other healthcare facilities, where they are known as healthcare-associated MRSA (HA-MRSA). Community-associated MRSA (CA-MRSA) infections occur in otherwise healthy individuals who have not been recently hospitalized or undergone medical procedures.

Pathogenesis

MRSA is able to resist methicillin and other beta-lactam antibiotics due to the presence of the mecA gene, which encodes a penicillin-binding protein (PBP2a) that has a low affinity for these antibiotics. This allows the bacterium to continue synthesizing its cell wall in the presence of methicillin.

Clinical Manifestations

MRSA can cause a variety of infections, including:

• Skin and soft tissue infections, such as abscesses, boils, and cellulitis.
• Pneumonia, particularly in patients with underlying lung disease.
• Bacteremia and sepsis, which can lead to endocarditis and other serious complications.
• Surgical site infections, which can complicate recovery from surgery.

Diagnosis

Diagnosis of MRSA is typically made by culturing the bacteria from a sample taken from the infected site and testing for antibiotic susceptibility. Molecular methods, such as PCR, can also be used to detect the presence of the mecA gene.

Treatment

Treatment of MRSA infections depends on the severity and location of the infection. Options include:

• Vancomycin, which is often used for serious infections.
• Linezolid, which can be used for skin infections and pneumonia.
• Daptomycin, which is used for bloodstream infections and right-sided endocarditis.

Prevention

Preventive measures include:

• Hand hygiene and the use of personal protective equipment in healthcare settings.
• Screening and decolonization of patients and healthcare workers who are carriers of MRSA.
• Proper wound care and hygiene in community settings to prevent the spread of CA-MRSA.

Related pages

• Antibiotic resistance
• Staphylococcus aureus
• Infection control
• Healthcare-associated infection