Minimum Inhibitory Concentrations of Common Antimicrobials against Gram-negative Bacteria—6 Years’ Experience from a Single Intensive Care Unit: Minimum Inhibitory Concentration Creep or Climb?

different parts of the world in gram-positive organisms. [7][8]8][9] However, the same phenomenon of MIC creep is scantily reported among GNB. [10][11]1][12] The purpose of the current study is to analyze the MIC distribution for GNB isolates from patients admitted to an intensive care unit (ICU) for select antimicrobials over a time period of 6 IntroductIonAntimicrobial resistance (AMR) is a global phenomenon, and it is well-known that AMR negatively impacts patient health outcomes.India is one of the largest consumers of antimicrobials. 1,2Widespread and unsupervised use of broad-spectrum antimicrobial agents has escalated the spread of multidrug-resistant organisms (MDROs).The last resort of treatment options for severe multidrug-resistant gram-negative bacterial (MDR GNB) infections is restricted to one or two classes of antibiotics.Minimum inhibitory concentration (MIC) breakpoint testing for AMR is aimed at providing clinicians information with respect to the potential usefulness of antimicrobial agents, that is, distinguishing between infections that are likely or unlikely to respond to a given treatment, where organisms classified as "resistant" imply a high likelihood of treatment failure. 3,4However, MIC breakpoints have a gray zone due to selective antibiotic pressure leading to constant evolution in bacteria in the form of heteroresistance, and a consistent small undetectable increase in MIC appears to have an independent effect on the reduced efficacy of various antimicrobials."MIC creep" is a phenomenon defined as an increase in the MIC of an organism over time, which is missed in the routine dichotomous laboratory reporting of categorizing microbes as either "sensitive" or "resistant," which sometimes leads to treatment failures, even when isolates are reported susceptible. 5,6everal studies are available on vancomycin MIC "creep" from 1,3,5,