Drug Topics - January 2009 - (Page 35) CONTINUING EDUCATION TABLE 2 HA-MRSA and CA-MRSA: Presentation MRSA type HA-MRSA Presentation Bloodstream infections, respiratory tract infections, urinary tract infections Skin and soft-tissue infections, necrotizing fasciitis, necrotizing pneumonia Patient Population Hospitalized patients, long-term-care residents, chronic illness patients, intravenous drug abusers, and the elderly Children, young adults, athletes CA-MRSA include clindamycin, doxycycline or minocycline, trimethoprim/sulfamethoxazole, and linezolid. Clindamycin A bacteriostatic, time-dependent lincosamide antibiotic, clindamycin acts on the 50S ribosomal subunit to inhibit protein synthesis. It is typically considered a second-line agent to penicillins for the treatment of susceptible gram-positive organisms and is reserved for patients allergic to penicillins. Clindamycin adequately penetrates a variety of tissues, including lung, pleural fluid, wound fluid, bones, and synovial fluid. A caution regarding the use of clindamycin for the treatment of staphylococcal infections is the specter of macrolidelincosamide-streptogramin group B-inducible resistance. Resistance to clindamycin may arise in strains that initially appear to be susceptible. Once susceptibility is determined, clindamycin may be a reasonable option for outpatient or step-down therapy in the treatment of skin and soft-tissue infections. Some case reports have generated speculation that antibiotic drug therapy interfering with PVL production may improve outcomes in patients with necrotizing CA-MRSA infections. Antibiotics that interfere with protein synthesis, such as clindamycin and linezolid, have been shown to suppress PVL production markedly. While the full utility of these agents in preventing PVL production is unclear, clindamycin has been used in combination with intravenous vancomycin to decrease PVL production in CA-MRSA necrotizing infections. CA-MRSA be sufficient. The first line of treatment for soft-tissue infections is incision/drainage of abscess, if present, and localized wound care. In some cases, adequate surgical intervention precludes the necessity for antibiotic treatment. Clinicians are encouraged to collect specimens for culture and antimicrobial susceptibility testing from all patients with suspected CA-MRSA infection. Culture and susceptibility results are useful both for management of individual patients and to help characterize local antimicrobial susceptibility patterns of S. aureus. If available, a local antibiogram can aid in the decision-making process. There are a number of factors to consider in the selection of an antibiotic for the treatment of CA-MRSA infection. First, it is helpful to know the common resistance patterns in the area. A high resistance rate to one antibiotic may preclude its use. Second, the treatment setting (inpatient versus outpatient) may dictate whether intravenous antibiotic preparations can be used. Finally, patient factors must be considered; these include but are not limited to allergies, age, drug-drug interactions, pregnancy, and co-morbidities. Empirical antibiotic treatment of skin and soft-tissue infections is often initiated with antibiotics targeted against S. aureus, such as cephalexin or dicloxacillin. However, MRSA strains are resistant to these and other beta-lactam antibiotics. Fortunately, CA-MRSA strains remain susceptible to many other antibiotic classes, due to the lack of multi-drug resistance associated with the SCCmec type IV element. Unfortunately, there are few outcome and head-to-head clinical trials evaluating which antibiotic may be superior to help guide selection. Even without these data, over the past few years there has been an increase in emergency-room prescription of antibiotics that cover CA-MRSA, especially trimethoprim/sulfamethoxazole. A quick summary of the antibiotics that cover CA-MRSA is available in Table 3. Tetracyclines The tetracyclines are bacteriostatic, time-dependent antibiotics that inhibit bacterial protein synthesis by binding to the 30S ribosomal subunit. Several studies have examined the in vitro susceptibility of various S. aureus isolates to the tetracyclines, specifically doxycycline and minocycline. Both drugs appear active in vitro against CA-MRSA, with susceptibility rates of 80 percent to 95 percent. The tetracyclines are attractive options for the outpatient treatment of mild CA-MRSA skin and softtissue infections. They are generally well tolerated, have easy dosing schedules, and are available generically. Tetracyclines are mainly used for outpatient treatment of skin and soft-tissue infections or for step-down therapy after IV antibiotic use. Data are generally lacking on the use of these agents to treat more severe infections. Two trials were recently conducted to evaluate the effectiveness of using tetracyclines in the outpatient treatment of MRSA-generated skin and soft-tissue infections. The first trial was a retrospective review examining doxycycline and minocycline. Both medications were prescribed at doses of 100 mg twice a day for a minimum of three days. Patients who were CA-MRSA positive experienced a 96 percent success rate when treated with one of these two antibiotics. The authors concluded that the expanded-spectrum tetracyclines are a reasonable oral treatment option for this indication. A second prospective trial confirmed these results. Doxycycline-treated patients demonstrated a 100 percent success rate Januar y 2009 Outpatient treatment options Mild-to-moderate skin and soft-tissue infections caused by CA-MRSA can often be treated on an outpatient basis with oral antibiotics. Empirical outpatient options for treatment of W W W.D R U GTO P I C S .C O M DRUG TOPICS 35 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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