Beyond Susceptible and Resistant, Part III: Treatment of Infections due to Gram-Negative Organisms Producing Carbapenemases.

Carbapenemases are enzymes that are capable of inactivating all or almost all beta-lactam antimicrobial agents. These enzymes are frequently coexpressed with other resistance mechanisms to non-beta-lactams, leading to extremely drug-resistant pathogens. Once a curiosity, these enzymes have spread into organisms that are among the most common causes of infection, such as Klebsiella pneumoniae and Escherichia coli. Identification of these organisms has proved challenging for clinical microbiology laboratories, leading to revisions in susceptibility standards for carbapenems. Although currently a rare cause of infection in children, these carbapenem-resistant Enterobacteriaceae (CRE) are becoming endemic in a variety of healthcare settings. Management of infections due to CRE is complicated by a lack of effective treatment options and clinical data on their effectiveness. Treatment of CRE infections in children is particularly challenging because therapeutic options for CRE lack adequate data on dosing and safety in children. Use of unconventional combination treatment regimens, including agents to which the organism is resistant in vitro, may provide some benefit in the treatment of severe CRE infection. Fortunately, several agents with the potential for treatment of CRE infections have been recently approved or are in late clinical development, although few data will be available in the short term to inform use in children.