Interim advice: If you hear 'spider bite,' think CA-MRSA

Interim advice: If you hear 'spider bite,' think CA-MRSA

CDC expert panel advice on emerging bug

Any light shed on resistant staph in the community by the Association for Professionals in Infection Control and Epidemiology's national prevalence survey will be most welcome. The most recent report from a Centers for Disease Control and Prevention expert working group on community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) says, "more data are needed in order to fully understand the epidemiology, microbiology, and pathophysiology of these infections and to identify optimal prevention and treatment strategies."¹

In the interim, the report recommendations include the following strategies for clinical management of CA-MRSA, with a particular focus on skin and soft-tissue (SSTIs) infections:

1. MRSA should be considered in the differential diagnosis of SSTIs compatible with S. aureus infection, such as skin abscesses. A presenting chief complaint of "spider bite" should raise suspicion of a S. aureus infection.
   
   
2. MRSA should be considered in the differential diagnosis of other syndromes compatible with S. aureus infection, including sepsis syndrome, osteomyelitis, septic arthritis, and pneumonia that is severe or follows an influenza-like illness, as well as in the differential diagnosis of some severe syndromes not typically associated with S. aureus, such as necrotizing fasciitis and purpura fulminans.
   
   
3. Clinicians are encouraged to collect specimens for culture and antimicrobial susceptibility testing from all patients with abscesses or purulent skin lesions, particularly those with severe local infections, systemic signs of infection, or history suggesting connection to a cluster or outbreak of infections among epidemiologically linked individuals. Culture and susceptibility results are useful both for management of individual patients and to help determine local prevalence of S. aureus susceptibility to beta-lactam and non-beta-lactam agents.
   
   In an outbreak within a defined cohort, cultures should be obtained from all new onset cases at least until the susceptibility pattern of the outbreak strain has been determined. In a community where empiric therapy for SSTIs has been modified to provide coverage for MRSA, obtaining cultures of purulent SSTIs is still important to monitor trends in susceptibility of S. aureus to non-beta-lactam agents.
   
   
4. At the present time, there is no information to suggest that molecular typing or identification of toxin genes should affect clinical management decisions.
   
   
5. Incision and drainage constitutes a primary therapy for furuncles, other abscesses, and septic joints, and should be performed routinely. If a clinician is unsure whether pus is present in a lesion, an attempt can be made to aspirate fluid from the lesion using an adequate size needle and syringe (e.g., a 16- to 19-gauge needle on a 10 cc syringe). For small furuncles not amenable to incision and drainage or collection of material for culture, moist heat may be satisfactory to promote drainage.
   
   
6. For some patients with purulent skin lesions, empiric antimicrobial therapy may be administered in addition to incision and drainage. Factors that may influence the clinical decision to supplement incision and drainage with antimicrobial therapy include severity and rapidity of progression of the SSTI or the presence of associated cellulitis; signs and symptoms of systemic illness; associated patient comorbidities or immune suppression; extremes of patient age; and location of the abscess in an area that may be difficult to drain.
   
   
7. When empiric antimicrobial therapy is provided for treatment of an SSTI compatible with S. aureus infection, local susceptibility data should be used to guide treatment. A beta-lactam agent (anti-staphylococcal penicillin or cephalosporin) is still a reasonable option for first-line therapy in a patient with mild to moderate illness and no significant comorbidities if the local prevalence of methicillin-resistance among community S. aureus isolates is low. There are no data to determine a specific MRSA prevalence rate that warrants a change in empiric therapy for SSTIs; a prevalence of greater than 10%-15% of community S. aureus isolates has been suggested by some experts.

Reference

1. Gorwitz RJ, Jernigan DB, Powers JH. Strategies for Clinical Management of MRSA in the Community: Summary of an Experts' Meeting Convened by the Centers for Disease Control and Prevention. March 2006. Available on the web at: www.cdc.gov/ncidod/dhqp/ar_mrsa_ca.html