Methicillin Resistant Staphylococcus aureus (MRSA)

Staphylococcus aureus is responsible for a broad range of clinical infections, most notable of which are cases of bacteremia and endocarditis. Staphylococcus aureus is an important cause of serious infections in both hospitals and the community. Methicillin-resistant Staphylococcus aureus (MRSA) were first reported in 1961 and the first hospital outbreak of MRSA was reported in 1963. When MRSA strains first appeared, they occurred predominantly in the healthcare setting. Cases of community-associated MRSA (CA-MRSA) infections were first reported in the late 1980s and early 1990s. Health care-associated MRSA (HA-MRSA) is particularly efficient at developing resistance to antimicrobial agents. Methicillin resistance among staphylococci has steadily increased worldwide, especially among cases acquired in hospitals. It is associated with longer hospital stay and more infections in intensive care units and leads to more antibiotic administration. Asymptomatically colonized patients and health care workers are the major sources of methicillin-resistant Staphylococcus aureus (MRSA) in the hospital environment. MRSA-infected patients in burns units are particularly problematic because the big surface area of denuded skin can produce a large inoculum of organisms that can be easily transmitted to other patients via the hands of health care workers. Extensive skin lesions also result in heavy shedders of MRSA. The commonest site of MRSA carriage is the anterior nares. A significant risk factor for acquisition of MRSA is the duration of hospital stay. Prolonged stay in the hospital is likely with patients in orthopedics and dermatology wards, which may result in high rates of carriage observed in these patients. HACO (Health careassociated MRSA with a community onset) refers to community onset for a person associated with a hospital environment, e.g., a person living in a residential home, a health care worker, a dialysis patient, or an individual with a history of hospitalization within the previous year. Risk factors associated with MRSA bacteremia include the following: residence in an extendedcare facility, prior antibiotic exposure, insulin dependent diabetes, prolonged hospitalization, urinary catheterization, nasogastric tube placement, prior surgery, and having an underlying disease. The elderly population (≥65 years old) is at a significantly higher risk of death due to MRSA bacteremia than are younger populations. MRSA bacteremia has been associated with an increased risk of acute renal failure, longer hospital and intensive-care-unit stays, development of ventilator dependency, and increased hospital costs. Fatality rates for patients that develop MRSA bacteremia are estimated to be between 23% and 54%. Nosocomial MRSA is remarkable for its clonal pattern of spread. Currently, 5 major MRSA clones account for approximately 70% of MRSA isolates in hospitals in the United States, South America, and Europe.