MIC distribution profile of newer antibiotics among gram-negative bacteria in a tertiary care centre

Worldwide, multi-drug resistant (MDR) gram-negative infections are a growing concern. Majority of the nosocomial infections including pneumonia, urinary tract infections, intra-abdominal infections and bloodstream infections are caused by gram-negative organisms such as Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa and Acinetobacter baumannii complex. These infections are responsible for significant mortality and morbidity. Currently limited numbers of antimicrobials are available for use to treat these multi-drug resistant organisms. Newer antimicrobials have been evaluated and approved for use in few countries. However the efficacy and baseline MIC values of the new antimicrobials against the gram-negative organisms have not been evaluated in other countries including India. Morover, no standard interpretative breakpoints such as CLSI or EUCAST criteria are available for interpretation of the susceptibility results of these antimicrobials. In this study we calculated the MIC50 and MIC90 values for five antibiotics to confirm their efficacy as probable treatment options for MDR gram-negative organisms. MIC50 and MIC90 are statistical percentiles which help surmise the MIC results and reflect the susceptibility patterns of bacteria to specific antimicrobials