Rash associated with piperacillin/tazobactam administration in infectious mononucleosis

OBJECTIVE: To report a case of piperacillin/tazobactam-induced rash in a patient with infectious mononucleosis. CASE SUMMARY: A 25-year-old white man developed a rash while receiving piperacillin/tazobactam 3.375 g intravenously every 6 hours and gentamicin for osteomyelitis complicating a left femur fracture secondary to a motorcycle accident. Due to progression of the rash following additional doses of piperacillin/tazobactam during hospitalization, the patient's antimicrobial regimen was changed to vancomycin and meropenem. Subsequently, a mononucleosis spot test was positive, and both Epstein-Barr virus (EBV) immunoglobulin (Ig) G and IgM antibodies were positive. The rash rapidly resolved with the discontinuation of piperacillin/tazobactam. DISCUSSION: Although the development of rash following the administration of several different antimicrobials, especially ampicillin, has been previously reported, this is the first report of piperacillin/tazobactam-induced rash in infectious mononucleosis. The rash is generally self-limiting and usually resolves within days of discontinuing the causative antimicrobial agent. An altered drug metabolism or an immune-mediated process has been suggested as the potential mechanism for rash development. CONCLUSIONS: Prior reports of antimicrobial-induced rash in infectious mononucleosis and a positive laboratory diagnosis of EBV in our patient with no history of penicillin allergy support the identification of piperacillin/tazobactam as the inducer of the rash. According to the Naranjo probability scale, the association of piperacillin/tazobactam with the rash was classified as probable.