Saturday, September 12, 2015

Penicllin Allergy and MSSA Bacteremia- Time to (at least) Take a Proper Allergy History

At a recent infectious diseases case conference at Virginia Commonwealth University we were discussing the mislabeling of penicillin allergy for patients needing staphylococcal coverage. Many people claim  that they are penicillin allergic, commonly resulting in the reflexive prescription of vancomycin for the management of gram positive infections.

Fortuitously, this article popped up in the literature.

Using mathematical modeling the authors simulated 3 strategies: (1) no allergy evaluation, treat with vancomycin (2) allergy history-guided treatment: if history excludes anaphylactic features treat with cefazolin and (3) complete allergy evaluation with history-appropriate PCN skin testing: if skin test negative, treat with cefazolin . Model outcomes included 12-week MSSA cure, recurrence, and death; allergic reactions and adverse drug reactions.

The use of vancomycin results in the fewest patients achieving MSSA cure and the highest rate of recurrence. In brief- vancomycin yields the poorest outcomes. The exclusion of a true allergy either by history or skin testing is preferred over simply prescribing vancomycin for MSSA bacteremia.

At the very least, when managing invasive staphylococcal infections, when informed of a penicillin allergy, this should be further addressed and not simply accepted as true as it impacts both choice of therapy outcome. 

It all comes back to taking a good history, as were taught in Practice of Medicine 101.