In the elderly or other people who are predisposed to such infections, specially when their immune function is threatened due to debility or other clinical conditions, these if not prevented immediately would lead to MRSA blood stream infection that can be the cause of significant mortality and morbidity. Significant research has gone into know the epidemiological characteristics of MRSA, mainly to know the microbiological features of these bacteria, and to delineate the risk factors, so the healthcare professionals can assume appropriate measures to control these infections.
Introduction: Methicillin-resistant Staphylococcus aureus, more popularly known as MRSA is a major cause of hospital-acquired infections that are more frequently encountered in clinical practice, and incidence of such infections are concerning due to the fact that they are becoming increasingly more difficult to combat because of emerging resistance to all antibiotic classes in vogue. Historically throughout the antibiotic era, strains of Staphylococcus aureus have developed resistance to the antimicrobial agents employed against them.
Over the last two decades, concerns about resistant strains of S. aureus have reached new heights as these microorganisms have become predominate in hospitals and disseminated into the community. These resistant strains have not only increased in absolute numbers, but they have also acquired resistance to multiple agents, leaving few therapeutic options for some infected patients (Enright, M. C. et al. , 2002). Historically, soon after introduction of penicillin, it was reported that bacteria can synthesize a penicillin inhibitor that permitted penicillin resistance in strains of S.
aureus. This type of resistance, resulting from penicillinase production was initially rare, but then spread rapidly. The investigators tried to solve the problem of epidemics arising from penicillinase producing S. aureus, by synthesizing methicillin. Methicillin was described as semisynthetic penicillinase resistant penicillin. Within 2 years of its introduction, naturally occurring resistant strains of S. aureus was recognized. These strains were called MRSA, and they subsequently proved resistant to the isoxazolyl penicillins such as oxacillin, cloxacillin, and dicloxacillin.
The acquisition of methicillin resistance provided S. aureus with a mechanism that made all members of the largest and most useful family of antimicrobials, the ? -lactam antibiotics, ineffective as therapeutic agents against these bacteria. Since discovery of the first clinical isolate 4 decades ago, MRSA strains have spread rapidly throughout many parts of the world. Its phenomenal dissemination has been ascribed to mainly evolutionary changes in the microorganisms in association with ineffective infection control practices and the intensified selective pressure fomented by increased antimicrobial use (Gemmell, C.
G. et al. , 2006). Clinically, there were reports from the United Kingdom in 1961 of isolates of S. aureus that has acquired resistance against methicillin, and MRSA isolates were soon recovered from other European countries and later from Japan, Australia, and United States. MRSA is now a problem in hospitals, and this is the commonest cause of hospital-acquired infections worldwide and at present is increasingly recovered from nursing homes and from the community.
However, the international spread of MRSA following its original recognition has been and continues to be one of the most difficult challenges to the control and treatment of hospital-acquired infections. Since the initial discovery, MRSA has become endemic in many geographic areas. Initially a problem centered in tertiary care referral hospitals affiliated to medical schools, MRSA has become prevalent now in hospitals of all sizes. The prevalence of methicillin resistance among S. aureus isolates from intensive care unit patients have increased from 2.
1% in 1975 to 55. 3% by 2000. Moreover, it can no longer be assumed that MRSA is almost always a nosocomial pathogen. Community associated and community-acquired strains of MRSA either infecting or colonizing hosts with or without recognized risk factors are increasingly being identified. There are sufficient evidences to conclude that MRSA strains are increasingly prevalent in the community, and they have emerged as important pathogens in this setting (Johnson, A. P. , Pearson, A. , and Duckworth, G. , 2005).