Drug Topics - January 2009 - (Page 33) COMMUNITY-ACQUIRED MRSA Although most infections caused by CA-MRSA typically involve skin and soft tissue, severe CA-MRSA pulmonary and bloodstream infections have been reported. These can rapidly progress to septic shock and are associated with high mortality due to CA-MRSA virulence factors. The economic burden on society arising from drug resistance is staggering. Domestic expenditures associated with the treatment of drug-resistant pathogens range from $4 billion to $30 billion annually. MRSA infection results in a one- to twofold increase in length of hospital stay and hospitalization costs. Increased hospitalization costs attributable to methicillin resistance are estimated at $5,000 to $40,000 per hospitalization, and these estimates do not include indirect costs such as those linked to time lost from work, the stress of a hospital stay, and the long-term health consequences. AMA PRA Category Credit CE CREDIT: 2.0 EARN CME CREDIT FOR THIS ACTIVITY AT WWW.DRUGTOPICS.COM E DU CATIO NAL O BJ E CTIV E S After participating in this activity, pharmacists should be able to: Distinguish between communityacquired methicillin-resistant Staphylococcus aureus (CA-MRSA) and healthcare-acquired methicillinresistant Staphylococcus aureus (HA-MRSA). Recommend options for the outpatient treatment of CA-MRSA. Choose from the options available for inpatient treatment of CA-MRSA. Identify the methods used for the prevention of CA-MRSA infection. Microbiology S. aureus is part of the normal flora of human beings and typically colonizes the nasal passages, skin, and mucous membranes. Approximately 25 percent to 30 percent of the population is colonized with this organism. S. aureus colonization may represent a benign natural occurrence; however, colonization also is a common first step in disease pathogenesis. Staphylococci are associated with a wide range of infections including but not limited to skin and soft-tissue infections, pneumonia, osteomyelitis, and bacteremia. S. aureus is a gram-positive coccus that typically grows in clusters. A facultative anaerobe, it is both catalase- and coagulase-positive. The production of coagulase is one of the traditional markers for S. aureus in the laboratory and may indicate the presence of this species in preliminary culture reports. Staphylococci are among a unique group of bacteria with the ability to cause serious infections in otherwise healthy individuals. The pathogenic nature of S. aureus is due to the production of a variety of virulence factors such as surface proteins that promote colonization and bacterial spread within host tissues, toxins that cause lysis in cell membranes, and exotoxins that damage host tissues or provoke symptoms of disease. S. aureus also has the ability to form biofilms on implanted devices that can diminish the penetration of some antibiotics to the site of infection. Furthermore, some clinical isolates of S. aureus produce a polysaccharide capsule that can aid in the prevention of phagocytosis. Lastly, treatment of staphylococcal infections can be complicated by expression of inherent or acquired antimicrobial resistance. Resistance patterns HA-MRSA and CA-MRSA possess distinct genotypes, phenotypes, and epidemiological properties. Laboratory identification of bacterial isolates can facilitate the classification of a MRSA strain as community-associated or hospitalassociated. Genotyping of isolates using pulsed-field electrophoresis (PFE) has revealed that HA-MRSA and CA-MRSA are genetically distinct from each other. Most CA-MRSA organisms are of the clone USA300 or USA400, whereas HA-MRSA genotypes are typically clones USA100, USA500, and USA800. This observation underscores the fact that CA-MRSA does not represent the spread of HA-MRSA into the community. Methicillin resistance in S. aureus is encoded by the mecA gene. Expression of this gene results in the production of an altered penicillin-binding protein (PBP) called PBP2a. This low-affinity PBP confers resistance to the beta-lactam classes of antimicrobials. HA-MRSA strains may also express genetic elements such as Tn554 or pT181. These genetic elements result in resistance to macrolides, clindamycin, streptogramin B, or tetracyclines. It is fortunate that, when viewed from a therapeutic standpoint, in comparison to HA-MRSA, CA-MRSA has a broader susceptibility pattern. While W W W.D R U GTO P I C S .C O M The University of Florida College of Pharmacy is accredited by the Accreditation Council for Pharmacy Education as a provider of continuing pharmacy education ACPE # 012-999-08-188-H01-P ACPE # 012-999-08-188-H01-T This lesson is no longer valid for CE credit after 01/31/2011. To obtain immediate CE credit, take the test on-line at www.drugtopics.com. Just click on the “Continuing Education”box on the Drug Topics home page, which will take you to the CE site. Log in, find and click on this lesson, and follow the three simple steps. Test results will be displayed immediately and you can print the certificate showing your earned CE credits. The authors disclose they have no nancial relationship with any manufacturer in this area of medicine. For questions concerning PRINT CEs, call (352) 273-6275. For questions concerning ON-LINE CEs, call (866) 261-3558. Januar y 2009 DRUG TOPICS 33 http://WWW.DRUGTOPICS.COM http://www.drugtopics.com http://WWW.DRUGTOPICS.COM
Table of Contents Feed for the Digital Edition of Drug Topics - January 2009 Drug Topics - January 2009 Contents Letters Up Front Up Front in Depth Community Practice Drug Pipeline: What to Watch in 2009 OTC Community-Aquired MRSA Infections New Products Viewpoint Drug Topics - January 2009 Drug Topics - January 2009 - Drug Topics - January 2009 (Page Cover1) Drug Topics - January 2009 - Drug Topics - January 2009 (Page Cover2) Drug Topics - January 2009 - Drug Topics - January 2009 (Page 1) Drug Topics - January 2009 - Drug Topics - January 2009 (Page 2) Drug Topics - January 2009 - Drug Topics - January 2009 (Page 3) Drug Topics - January 2009 - Contents (Page 4) Drug Topics - January 2009 - Contents (Page 5) Drug Topics - January 2009 - Contents (Page 6) Drug Topics - January 2009 - Contents (Page 7) Drug Topics - January 2009 - Contents (Page 8) Drug Topics - January 2009 - Contents (Page 9) Drug Topics - January 2009 - Contents (Page 10) Drug Topics - January 2009 - Contents (Page H1) Drug Topics - January 2009 - Contents (Page H2) Drug Topics - January 2009 - Contents (Page H1) Drug Topics - January 2009 - Contents (Page H2) Drug Topics - January 2009 - Contents (Page H3) Drug Topics - January 2009 - Contents (Page H4) Drug Topics - January 2009 - Contents (Page H5) Drug Topics - January 2009 - Contents (Page H6) Drug Topics - January 2009 - Contents (Page H7) Drug Topics - January 2009 - Contents (Page H8) Drug Topics - January 2009 - Contents (Page 13) Drug Topics - January 2009 - Up Front (Page 14) Drug Topics - January 2009 - Up Front (Page 15) Drug Topics - January 2009 - Up Front (Page 16) Drug Topics - January 2009 - Up Front (Page 17) Drug Topics - January 2009 - Up Front in Depth (Page 18) Drug Topics - January 2009 - Up Front in Depth (Page 19) Drug Topics - January 2009 - Community Practice (Page 20) Drug Topics - January 2009 - Community Practice (Page 20a) Drug Topics - January 2009 - Community Practice (Page 20b) Drug Topics - January 2009 - Community Practice (Page 21) Drug Topics - January 2009 - Drug Pipeline: What to Watch in 2009 (Page 22) Drug Topics - January 2009 - Drug Pipeline: What to Watch in 2009 (Page 23) Drug Topics - January 2009 - Drug Pipeline: What to Watch in 2009 (Page 24) Drug Topics - January 2009 - Drug Pipeline: What to Watch in 2009 (Page 25) Drug Topics - January 2009 - Drug Pipeline: What to Watch in 2009 (Page 26) Drug Topics - January 2009 - Drug Pipeline: What to Watch in 2009 (Page 27) Drug Topics - January 2009 - OTC (Page 28) Drug Topics - January 2009 - OTC (Page 29) Drug Topics - January 2009 - OTC (Page 30) Drug Topics - January 2009 - OTC (Page 31) Drug Topics - January 2009 - Community-Aquired MRSA Infections (Page 32) Drug Topics - January 2009 - Community-Aquired MRSA Infections (Page 33) Drug Topics - January 2009 - Community-Aquired MRSA Infections (Page 34) Drug Topics - January 2009 - Community-Aquired MRSA Infections (Page 35) Drug Topics - January 2009 - Community-Aquired MRSA Infections (Page 36) Drug Topics - January 2009 - Community-Aquired MRSA Infections (Page 37) Drug Topics - January 2009 - Community-Aquired MRSA Infections (Page 38) Drug Topics - January 2009 - Community-Aquired MRSA Infections (Page 39) Drug Topics - January 2009 - Community-Aquired MRSA Infections (Page 40) Drug Topics - January 2009 - Community-Aquired MRSA Infections (Page 41) Drug Topics - January 2009 - New Products (Page 42) Drug Topics - January 2009 - New Products (Page 43) Drug Topics - January 2009 - New Products (Page 44) Drug Topics - January 2009 - New Products (Page 45) Drug Topics - January 2009 - New Products (Page 46) Drug Topics - January 2009 - New Products (Page 47) Drug Topics - January 2009 - Viewpoint (Page 48) Drug Topics - January 2009 - Viewpoint (Page Cover3) Drug Topics - January 2009 - Viewpoint (Page Cover4)
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