MRSA Pathophysiology

Transmission and epidemiology of MRSA: current perspectives
Maggi Banning Abstract
Staphylococcus aureus is a Gram-positive bacterium that developed resistance to the penicillin derivative tnethicillin. Subsequently, methicillin-resistant S. aureus {MRSA) emerged as a bacterium that became less susceptible to the actions of methicillin and thus developed the ability to colonize and cause life-threatening infections. Globally., MRSA continues to cause hospital-acquired infections which are becoming difficult to treat owing to increasing glycopeptide resistance and the increasing development of community-associated MRSA. Nurses caring for patients in both hospital and community settings should be able to acknowledge the importance of MRSA,
Pugliese and Favero (2004) studied 254 patients with or without MRSA between 1997 and 2002. They found that all patients with MRSA bacteraemia during the first 24 hours of hospital admission had had a recent exposure to a healthcare setting; communityacquired MRSA was not detected. Independent risk factors for healthcare-associated MRSA were previous MRSA infection or colonization, cellulitis, presence of a central venous catheter or skin ulcers (Tacconelli et al, 2004), or pressure ulcers {Thomas et al, 2003), Hospital-acquired, also referred to as health care-associated or healthcare-acquired, infections generally involve older people and pertain to surgical wounds and intravenous indwelling catheters (Pugliese et al, 2004). In contrast, community-acquired MRSA infections are increasing in frequency (Shopsin et al, 2000), particularly involving young people. Community-acquired MRSA causes localized disease and predominantly primary skin and soft tissue infections (Vandenesch and Etienne, 2004). This form of MRSA is susceptible to antibiotics and has the same risk factors for acquisition/disease as nietliicillin-susceptibie S. amem (MSSA). Community-acquired MRSA shares similarities with MSSA owing to the presence of mecA; the gene that encodes the methicilliji-resistant penicillin-hinding protein (Buescher, 2005). Community-associated MRSA also carries the staphylococcal-virulence factor PVL. PVL-posidve commiinit)'-associated MRSA is easily transmissible not only between families but also on a larger scale in community settings such as prisons, schools and sports teams. Skin-to-skin contact involving abrasions and indirect contact witli contaminated objects such as towels, sheets, and sport equipment seem to represent a mode of transmission. The PVL loci is found in 10% of all MRSA isolates. Wannet et al (2004) reported that about 75% of isolates are obtained from abscesses,