MRSA fight rages on with new drugs, time-tested protection

July 1, 2012

Newer drugs are available to combat potentially serious infections including methicillin-resistant Staphylococcus aureus (MRSA), says Kenneth J. Tomecki, M.D., vice-chairman, department of dermatology, Cleveland Clinic. Colonization, mainly of the anterior nares, remains a major risk factor for MRSA.

Key Points

Cleveland - Newer drugs are available to combat potentially serious infections including methicillin-resistant Staphylococcus aureus (MRSA), says Kenneth J. Tomecki, M.D., vice-chairman, department of dermatology, Cleveland Clinic.

Colonization, mainly of the anterior nares, remains a major risk factor for MRSA. "Secondary factors include skin-to-skin and skin-to-fomite contact (Kuehnert MJ, Kruszon-Moran D, Hill HA, et al. J Infect Dis. 2006;193(2):172-179. Epub 2005 Dec 15)," Dr. Tomecki says.

Risk factors for hospital-acquired MRSA (HA-MRSA) include extended hospital stays (especially in an ICU), surgical wounds, prior antibiotic use and invasive devices such as in-dwelling catheters, Dr. Tomecki says. Besides patients with MRSA infections, "MRSA often resides on hospital personnel and inanimate objects."

Community-acquired MRSA (CA-MRSA) typically stems from poor hygiene, overcrowded conditions, contact sports and contact with contaminated items, Dr. Tomecki says. "Children and young adults are especially susceptible, as are inmates, athletes and day care workers."

CA-MRSA typically appears as a "hot lesion" in a young patient, usually an abscess or boil, he says. Abscesses account for 70 percent of CA-MRSA infections.

"The primary treatment for CA-MRSA infections is incision and drainage, plus culture. Culture is the key to patient management and establishing local prevalence," he says. For MRSA/MSSA, a "quick test" is now available, yielding results with 99 percent accuracy.

Most patients with CA-MRSA infections do not require antibiotics, Dr. Tomecki says, except in special cases, such as a large lesion, cellulitis, fever, comorbidities or extremes of age (Paydar KZ, Hansen SL, Charlebois ED, et al. Arch Surg. 2006; 141(9): 850-856).

According to recent guidelines published by the Infectious Diseases Society of America, preferred antibiotics for CA-MRSA infections in outpatient settings include trimethoprim/sulfamethoxazole (TMP-SMX), doxycycline and clindamycin, Dr. Tomecki says.

"TMP-SMX is inexpensive, has good oral bioavailability and is bactericidal in vitro," he says. However, TMP-SMX can cause serious reactions in HIV-infected patients. Other side effects include exanthems, photosensitivity, anorexia, nausea/vomiting, glossitis and stomatitis, he says.

Tetracyclines (ordinarily, doxycycline and minocycline) are a good choice as well, Dr. Tomecki says. They offer good oral bioavailability but have limited efficacy against group A streptococci, and MRSA is slowly developing resistance to tetracyclines.

For serious, extensive infections, especially in hospitalized patients, parenteral therapy includes vancomycin, linezolid, daptomycin, clindamycin, tigecycline and quinupristin/dalfopristin, Dr. Tomecki says. Vancomycin remains the initial drug of choice, despite its drawbacks (slow response time, relapse bacteremia, leukopenia and occasional rash).

Additionally, he says that over time, MRSA infections may develop resistance to vancomycin, often requiring higher doses that can lead to toxicity.

Newer parenteral agents for MRSA infections include ceftaroline, an intravenous cephalosporin which Dr. Tomecki says is comparable to vancomycin and ceftobiprole. On the horizon are dalbavancin, telavancin and oritavancin. These are semi-synthetic lipoglycopeptides, which are bactericidal in vivo, and inhibit cell wall synthesis, he says.

Preventive measures

Dr. Tomecki says physicians must teach patients about proper woundcare and good personal hygiene, which includes regular bathing and hand washing, thorough laundering of clothing and towels and no reuse of personal items (towels, razors) that could carry pathogens. He also recommends regular cleaning and disinfecting of "high-touch" objects and surfaces.

Dr. Tomecki says physicians should consider decolonization if infections continue to recur despite preventive measures. He suggests using mupirocin in the nares twice daily for five to 10 days (which reduces colonization by 50 percent), with or without body decolonization. This can be accomplished with chlorhexidine, triclosan or twice-weekly dilute bleach baths, he says.

For parenteral treatment, physicians can use clindamycin or TMP-SMX with rifampin, which can decrease nasal colonization up to 80 percent. Along with the nares, physicians should consider decolonizing the perineum, axillae, throat, breasts and digital webbed skin, all of which areas of potential colonization.