Impact of Antibiotic MIC on Infection Outcome in Patients with Susceptible Gram-negative Bacteria: a Systematic Review and Meta-analysis

The objective of this study was to analyze the impact of MIC values within the susceptible range of antibiotics on the outcomes of patients with Gram-negative infections. The PubMed and Scopus electronic databases were searched. We identified 13 articles (1,469 patients) that studied the impact of antibiotic MICs on the outcomes of infections; β-lactams were studied in 10 of them. Infections due to Salmonella enterica strains with high fluoroquinolone MICs were associated with more treatment failures than those due to strains with low MICs (relative risk [RR], 5.75; 95% confidence interval [CI], 1.77 to 18.71). Among non-Salmonella enterobacteriaceae, there was no difference in treatment failures depending on the MIC value (RR, 1.18; 95% CI, 0.71 to 1.97); however, a higher all-cause mortality was observed for patients infected with strains with high MICs (RR, 2.03; 95% CI, 1.05 to 3.92). More treatment failures were observed for patients infected with nonfermentative Gram-negative bacilli when strains had high MICs (RR, 5.54; 95% CI, 2.72 to 11.27). The mortality rate for patients with infections with Gram-negative nonfermentative bacilli with high MICs was also higher than for those with low MICs (RR, 2.39; 95% CI, 1.19 to 4.81). The limited available data suggest that there is an association between high MICs, within the susceptible range, and adverse outcomes for patients with Gram-negative infections.