Colistin and Tigecycline Resistance in Carbapenem-Resistant Enterobacteriaceae: Checkmate to Our Last Line Of Defense

Of particular importance are the pathogens of this family that produce metallo-β-lactamases (IMP-type carbapenemases [IMP], New Delhi metallo-β-lactamase, or Verona integron-encoded metallo-β-lactamase [VIM]), non-metallo enzymes (Klebsiella pneumoniae carbapenemase and Oxacillinase [OXA]-48), β-lactamases with a broad profile of substrate activity such as extended-spectrum β-lactamases, or AmpC enzyme with porin loss. [...]recently, carbapenems have been successfully used for the treatment of infections caused by Enterobacteriaceae, including those producing extended-spectrum β-lactamases.1 Antibiotic treatment options for these emerging carbapenem-resistant Enterobacteriaceae (CRE) are becoming limited.2 Colistin and tigecycline have been reported as the remaining armamentarium against the species of Enterobacteriaceae.3,4 In the present study, a total of 210 clinically significant Enterobacteriaceae isolates were collected from various clinical samples of admitted patients (blood, urine, wound, and burn) over a period of 2 years (2013–2015). Susceptibility testing was performed by Clinical and Laboratory Standards Institute broth microdilution method, and isolates with a meropenem or imipenem minimum inhibitory concentration (MIC) of at least 4 mg/L were categorized as CRE. C. freundii, Citrobacter freundii; E. aerogenes, Enterobacter aerogenes; E. cloacae, Enterobacter cloacae; E. coli, Escherichia coli; K. pneumoniae, Klebsiella pneumoniae; P. mirabilis, Proteus mirabilis; P. stuartii, Providencia stuartii; S. marcescens, Serratia marcescens. [...]there is clearly a need for the development and screening of new antimicrobial agents to keep pace with the development and spread of drug resistance mechanisms in the Enterobacteriaceae family.