During the past four decades, a type of bacteria has evolved from a controllable nuisance into a serious public health concern. This bacterium is known as methicillin-resistant Staphylococcus aureus, or MRSA. About one-third of people in the world have S. aureus bacteria on their bodies at any given time, primarily in the nose and on the skin. The bacteria can be present without causing an active infection. Of the people with S. aureus present, about 1 percent has MRSA, according to the Centers for Disease Control and Prevention (CDC).
MRSA can be categorized according to where the infection was acquired: hospital-acquired MRSA (HA-MRSA) or community-associated MRSA (CA-MRSA).
Hospital-acquired MRSA (HA-MRSA)
HA-MRSA is acquired in the hospital setting and is one of many hospital-acquired infections exhibiting increased antimicrobial resistance. HA-MRSA has increased during the past decade due to a number of factors including an increased number of immunocompromised and elderly patients; an increase in the number of invasive procedures, e.g., advanced surgical operations and life support treatments; and failures in infection control measures such as hand washing prior to patient contact and removal of non-essential catheters.
Community-associated MRSA (CA-MRSA)
CA-MRSA is caused by newly emerging strains unlike those responsible for HA-MRSA and can cause infections in otherwise healthy persons with no links to healthcare systems. CA-MRSA infections typically occur as skin or soft tissue infections, but can develop into more invasive, life-threatening infections. CA-MRSA is occurring with increasing frequency in the United States and around the world and tends to occur in conditions where people are in close physical contact, such as athletes involved in football and wrestling, soldiers kept in close quarters, inmates, childcare workers, and residents of long-term care facilities.
MRSA has attracted the attention of the medical research community, illustrating the urgent need to develop better ways to diagnose and treat bacterial infections.