Efficacy of ertapenem for consolidation therapy of extended-spectrum β-lactamase-producing gram-negative infections:: A case series report

BACKGROUND: Infections caused by extended-spectrum P-lactamase (ESBL)producing gram-negative organisms are becoming increasingly common and present significant challenges in terms of treatment. Carbapenems is the antibiotic class of choice for treatment of these types of infections. Ertapenem is the newest carbapenem, capable of being dosed once daily, and has some in Vitro but little in vivo evidence supporting its use for the treatment of these resistant infections. OBJECTIVE: To examine the clinical and microbiologic outcomes associated with ertapenem therapy of ESBL-producing Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis infections. METHODS: This was a retrospective case series that examined the clinical and microbiologic outcomes of 22 patients who received ertapenem for treatment of an ESBL infection at Rush University Medical Center in Chicago, IL, during 2003-2005. RESULTS: The majority (16/22) of patients received ertapenem for consolidation rather than initial therapy. Different antibiotics most commonly used were other carbapenems, piperacillin/tazobactam, and aminoglycosides. The most common infections treated were lower urinary tract infections and osteomyelitis. Clinical efficacy was determined in all 22 patients, with 20 (91 %) patients having a positive outcome, defined as either clinical improvement or clinical cure. The best clinical cure rate was seen with wound infections, where all 3 patients examined were found to be clinically cured. Microbiologic efficacy was determined in 7 patients, with 6 (85.7%) defined as microbiologic cure. One patient was found to be both a clinical and microbiologic failure and was also found to have developed an ertapenem-resistant strain of E coli. CONCLUSIONS: These results demonstrate potential microbiologic and clinical efficacy of ertapenem for treatment of ESBL-producing infections and the need for a prospective, randomized study examining its efficacy versus that of other carbapenems.