The scenario involves a surgical patient with a purulent abdominal wound culture growing Staphylococcus aureus, a common pathogen in surgical site infections (SSIs). The Certification Board of Infection Control and Epidemiology (CBIC) emphasizes accurate interpretation of culture results and antibiotic therapy in the "Identification of Infectious Disease Processes" and "Prevention and Control of Infectious Diseases" domains, aligning with the Centers for Disease Control and Prevention (CDC) guidelines for managing SSIs. The question requires assessing the sensitivity pattern and current treatment to determine the correct statement.
Option B, "The current therapy is not effective," is true. The wound culture shows Staphylococcus aureus resistant to oxacillin, indicating methicillin-resistant S. aureus (MRSA). The sensitivity pattern lists resistance to penicillin, oxacillin, cephalothin, and erythromycin, with susceptibility to clindamycin and vancomycin. Cefazolin, a first-generation cephalosporin, is ineffective against MRSA because resistance to oxacillin (a penicillinase-resistant penicillin) implies cross-resistance to cephalosporins like cefazolin due to altered penicillin-binding proteins (PBPs). The CDC’s "Guidelines for the Prevention of Surgical Site Infections" (2017) and the Clinical and Laboratory Standards Institute (CLSI) standards confirm that MRSA strains are not susceptible to cefazolin, meaning the current therapy is inappropriate and unlikely to resolve the infection, supporting Option B.
Option A, "The wound is not infected," is incorrect. The presence of purulent drainage, a clinical sign of infection, combined with a positive culture for S. aureus, confirms an active wound infection. The CBIC and CDC define purulent discharge as a key indicator of SSI, ruling out this statement. Option C, "Droplet Precautions should be initiated," is not applicable. Droplet Precautions are recommended for pathogens transmitted via respiratory droplets (e.g., influenza, pertussis), not for S. aureus, which is primarily spread by contact. The CDC’s "Guideline for Isolation Precautions" (2007) specifies Contact Precautions for MRSA, not Droplet Precautions, making this false. Option D, "This is a methicillin-sensitive S. aureus (MSSA) strain," is incorrect. Methicillin sensitivity is determined by susceptibility to oxacillin, and the resistance to oxacillin in the culture result classifies this as MRSA, not MSSA. The CDC and CLSI use oxacillin resistance as the defining criterion for MRSA.
The CBIC Practice Analysis (2022) and CDC guidelines stress the importance of aligning antimicrobial therapy with sensitivity patterns to optimize treatment outcomes. The mismatch between cefazolin and the MRSA sensitivity profile confirms that Option B is the correct statement,indicating ineffective current therapy.
[References:, CBIC Practice Analysis, 2022., CDC Guidelines for the Prevention of Surgical Site Infections, 2017., CDC Guideline for Isolation Precautions, 2007., CLSI Performance Standards for Antimicrobial Susceptibility Testing, 2022., , ]
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