Dosing impact of cefepime and meropenem on multidrug-resistant Pseudomonas aeruginosa chronic cellulitis: A case...

To describe a case of treatment failure and emergent resistance due to suboptimal antibiotic dosing and demonstrate a practical strategy for optimizing dosing to achieve treatment efficacy.

We report a woman in her 90s with no history of renal disease but with low weight and height. She was treated with a renally adjusted dose of cefepime for cellulitis caused by multidrug resistant (MDR) Pseudomonas aeruginosa, with a minimum inhibitory concentration at the susceptibility borderline. One month later, she was re-admitted for cefepime-resistant P. aeruginosa cellulitis and therapy was switched to meropenem. The meropenem dose was optimized by evaluating both the creatinine clearance (CrCl) calculated by the Cockcroft-Gault equation and the modification of diet in renal disease (MDRD) estimated glomerular filtration rate (eGFR). This approach led to a successful treatment.

This case highlights the challenge of dosing antibiotics in the elderly population for MDR bacteria, where high doses are often required. To prevent treatment failure and the emergence of resistance from suboptimal dosing, we recommend evaluating renal function using MDRD eGFR in addition to CrCl, when a significant discrepancy exists between the 2 values.