A Sneak Peek at Upcoming IDSA Guidelines on MRSA Infections and UTIs

Highlights of upcoming recommendations of the Infectious Diseases Society of America (IDSA) for the treatment of methicillin-resistant Staphylococcus aureus (MRSA) infections and community-associated urinary tract infections (CA-UTIs) were presented at the joint 48th Annual Interscience Conference of Antimicrobial Agents and Chemotherapy/ IDSA 46th Meeting, which took place in Washington, DC, from October 25 to 28. The recommendations are scheduled to be finalized and officially disseminated in the spring of 2009. Some salient points are summarized here.

MRSA infections
According to Catherine Liu, MD, assistant professor of infectious diseases at the University of California at San Francisco, the IDSA guidelines recommend that incision and drainage be the primary treatment for MRSA abscesses. Antibiotic therapy is probably unnecessary in most patients. Results from observational studies suggest that cure rates are high in persons in whom MRSA abscesses are treated with incision and drainage whether or not they also receive antibiotic therapy. Whether antibiotic therapy provides additional benefit is being addressed by 2 large, randomized clinical trials sponsored by the NIH.

Clindamycin, trimethoprim/sulfamethoxazole, and doxycycline are recommended for empiric therapy in patients who have noncomplicated community-associated MRSA (CAMRSA) skin and soft tissue infections (SSTIs), such as cellulits with purulent drainage. The role of CAMRSA in cellulitis without purulent drainage or associated abscesses is unknown; empiric therapy that covers ?-hemolytic streptococci is recommended, and therapy for CAMRSAinfection may be considered, especially if treatment with a ?-lactam antibiotic has failed or if the patient has a complicated infection. In addition to surgical debridement, patients with complicated SSTIs or necrotizing fasciitis should receive empiric therapy with vancomycin or, alternatively, daptomycin or linezolid. Such therapy also may be considered in patients with pure cellulitis. Clindamycin may be used as an alternative to vancomycin in children in areas where the rate of resistance to clindamycin in low (less than 10%).

A multimodal approach for management of recurrent MRSA SSTIs that includes patient education about hygiene and wound care is recommended. Although the value of decolonization is unknown, the IDSA panel concurs that clinicians may consider decolonization in patients in whom MRSA SSTIs recur and also in settings where recurrent transmission occurs among family members or close contacts despite optimization of hygiene and wound care practices. Although evidence regarding benefit is lacking, strategies to achieve decolonization, such as topical nasal mupirocin and/or chlorhexidine or dilute bleach baths, may be considered. Routine use of oral antibiotics for decolonization, however, is discouraged because of lack of evidence of benefit, potential for adverse effects, and risk of emergence of antibiotic resistance.

The recommended dosage of vancomycin for the general treatment of MRSA infections in persons with normal renal function is 15 to 20 mg/kg every 8 to 12 hours. To optimize vancomycin pharmacodynamics and minimize selection of vancomycin- resistant subpopulations, clinicians should consider targeting higher vancomycin trough levels (15 to 20 ?g/mL) in patients with serious MRSA infections. Because higher vancomycin trough levels may be associated with increased nephrotoxicity, careful monitoring is recommended, particularly in patients who are critically ill, have abnormal renal function, or are receiving nephrotoxic medications concomitantly with vancomycin.

Although there are several alternatives to vancomycin, no agent has clearly demonstrated superiority to it for the treatment of MRSA infections. Daptomycin, linezolid, and tigecycline are FDA-approved alternatives for the treatment of complicated SSTIs. Oral linezolid (600 mg bid) is an alternative to vancomycin for treatment of MRSA pneumonia in adults. Intravenous daptomycin at a dosage of 6 mg/kg daily is an alternative to vancomycin for treatment of MRSA bacteremia or endocarditis. Some experts recommend dosages of 8 to 10 mg/kg. Whether these higher doses are safe and whether they provide increased benefit are under investigation. The addition of gentamicin or rifampin to vancomycin is discouraged; no clear evidence of benefit exists and combined use may increase toxicity.

There are several limitations to currently available susceptibility testing methods. Several of these methods report minimal inhibitory concentration (MIC) value results that are up to 1 dilution higher than the Clinical and Laboratory Standards Institute reference broth microdilution test, making interpretation of these results challenging. Because of the current limitations, management decisions should not be based solely on MIC values, and correlation with clinical and microbiological responses are recommended. If a satisfactory response to vancomycin therapy is seen, even if the MIC is 2 ?g/mL, the existing therapeutic protocol should be continued. If no improvement is seen despite adequate debridement and removal of other foci of infection, vancomycin should be switched to another therapy regardless of the MIC value.

These snippets from the upcoming guidelines are not final and are subject to change before the official document is released. Additional topics covered are bone and joint and CNS infections attributed to MRSA, management of vancomycin treatment failures, and treatment of MRSA infections in children.

Urinary tract infections
Infectious disease specialist Thomas M. Hooten, MD, who is currently affiliated with the University of Miami and is chair of the IDSA/Society for Healthcare Epidemiology of America guidelines on antibiotic stewardship, noted that the upcoming guidelines on catheter-related CA-UTIs will include information on diagnosis, prevention, and treatment.

A diagnosis of CA-UTI is defined as detection of 102 colonyforming units (CFU)/mL or more of a uropathogen in a single urinary catheter specimen in a symptomatic patient. Adiagnosis of community-associated asymptomatic bacteriuria (CA-ASB) is defined as detection of more than 105 CFU/mL of a bacterial pathogen in a urine specimen from an asymptomatic patient. CA-UTI and CAASB often occur in tandem, explained Hooten.

Prevention of catheter-related UTIs demands strict protocols regarding catheter use. It will be recommended that institutions establish their own list of appropriate indications for urinary catheter use that are periodically reviewed in relation to IDSA guidelines and updates. Health care facilities will be encouraged to require orders for urinary catheter insertion that are documented on the patient chart before the procedure occurs. Automatic- stop orders that prompt a nurse or technician to be diligent in removing a patient's catheter according to predetermined instructions will also be advocated.

Intermittent catheterization is recommended over indwelling catheterization, and because no data show that the sterile (singleuse catheter) technique offers any benefit over the clean (multiple-use catheter) technique, either is approved for use in both the outpatient and institutional setting. Whereas condom catheters may be of value in the prevention of UTIs in men who are not cognitively impaired and who require urinary catheterization, the value of hydrophilic urinary catheters, portable bladder scanners, and the no-touch technique in reducing the risk of CA-UTIs is yet to be determined. Meatus cleaning, routine catheter change, and antimicrobial prophylaxis are not indicated.

Silver alloy or antibiotic-coated catheters may help prevent or delay bacteriuria and CA-UTIs in patients in whom indwelling catheters are inserted for a short term; however, more data are required to confirm whether a benefit exists.

Methenamine salts may be effective in preventing UTIs, although use in patients in whom urinary catheterization persists for more than a week is discouraged, in light of findings from a study by Lee and colleagues¹ that appeared in the Cochrane Database of Systematic Reviews in 2007. Treatments of choice for complicated UTIs and acute pyelonephritis are oral or intravenous levofloxacin at a dosage of 750 mg once daily for 5 days, intravenous ciprofloxacin at a dosage of 400 mg bid for 10 days, or oral ciprofloxacin at a dosage of 500 mg bid for 10 days, as suggested by Peterson and colleagues² in a study published in Urology earlier this year. Again, this preview of elements from the upcoming guidelines is not final; the guidelines are subject to change before the official document is released.

References:

• Lee BB, Simpson JM, Craig JC, Bhuta T. Methenamine hippurate for preventing urinary tract infections. Cochrane Database Syst Rev. 2007 Oct 17;(4):CD003265.

• Peterson J, Kaul S, Khashab M, et al. Adoubleblind, randomized comparison of levofloxacin 750 mg once-daily for five days with ciprofloxacin 400/500 mg twice-daily for 10 days for the treatment of complicated urinary tract infections and acute pyelonephritis. Urology. 2008;71:17-22.