Background

S. aureus is a major human pathogen, causing a wide spectrum of hospital-acquired and community-acquired infections worldwide.[1,2] The use of potent antimicrobials, such as the b-lactam class of antibiotics, for the treatment of severe S. aureus disease has contributed significantly to reduced morbidity and mortality rates.[3] However, of great global concern is the rapid emergence and spread of MRSA strains. Since their first description in 1961 in the UK shortly after the introduction of methicillin into clinical use,[4] MRSA strains have spread to all parts of the world.[1,5-7] Rates of methicillin resistance in S. aureus vary markedly by geographical region, ranging from < 2% in Switzerland and The Netherlands to over 70% in Hong Kong and Japan.[1] Although methicillin is no longer used clinically or for laboratory susceptibility testing (having been replaced by cloxacillin and oxacillin, respectively), strains classified as methicillin-resistant harbor the mecA gene, which, when expressed, renders isolates resistant to all p-lactam agents, including penicillinase-resistant penicillins (e.g., methicillin, oxacillin), cephalosporins, and carbape-nems.[8,9] These strains also have a tendency to carry other antibiotic-resistant genes, resulting in multiple drug resistance.1-1'10'11-1 Although glycopeptides, such as vancomycin, and newer antimicrobials with purported activity against multidrug-resistant MRSA are available for clinical use, patient outcomes have been less than favorable with these agents.[12] Furthermore, the increasing use of vancomycin has contributed to the emergence of vancomycin-resistant enterococci[13] and, more recently, vancomycin-resistant staphylococci.1-14-1 The MRSA epidemic has, until lately, been largely confined to the hospital setting. However, the epidemiology has now expanded into the community, with a number of community-acquired infections caused by newly emerging virulent clones of MRSA being recently described.[7] Nevertheless, MRSA remains a serious hospital infection control problem, whereby strict measures and surveillance activities are required to prevent the intrainstitutional and interinstitutional spread of these strains from colonized or infected patients.[15] To facilitate the institution of appropriate antimicrobial chemotherapy and/or infection control measures for MRSA, rapid and accurate laboratory diagnostic methods are critical. Laboratories have traditionally relied on phenotypic methods, particularly the standard oxacillin salt agar screen recommended by the National Committee for Clinical Laboratory Standards (NCCLS)[8] and also mecA gene product latex agglutination tests,[9,16] for the detection of methicillin resistance in S. aureus. However, mecA expression—and hence methicillin resistance—is variable, being influenced by a complex interplay between mecA and a number of other genes as well as various environmental and in vitro factors.[10,16,17] Phenotypic detection may also be confounded by the common occurrence of heterogeneous MRSA strains composed of susceptible and resistant subclones.[10,18] Additionally, strains of S. aureus lacking the mecA gene may occasionally demonstrate low-level, nonclinically significant, phenotypic resistance to meth-icillin because of other mechanisms, but are not considered to be true MRSA.[9,10,16] Furthermore, some of these phenotypic tests may be labor-intensive and slow (turnaround time >24 hr). Hence an increasing number of laboratories are resorting to the use of more widely available molecular methods, either alone or in combination with these phenotypic assays, for detecting MRSA.

Molecular detection of mecA is now considered the gold standard method for MRSA diagnosis,[16] and a number of genotypic assays based on polymerase chain reaction (PCR) and real-time PCR platforms have been recently described, which allow for easy, rapid (2-5 hr), and precise detection of the mecA gene in clinical isolates of c [19-22]

S. aureus.

Getting Started With Dumbbells

Getting Started With Dumbbells

The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.

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