Effect of polymicrobial interactions on antimicrobial resistance: an analysis in human ocular infections.

Investigate the effect of polymicrobial interactions on antimicrobial resistance (AMR) of ocular pathogens in polymicrobial settings, compared with monomicrobial infections. Polymicrobial interactions were labeled as antagonistic, synergistic or indifferent based on a reduction, an increase or no change, respectively, in antibiotics' MIC by the Vitek 2 compact system, compared with monomicrobial pathogens. showed antagonistic polymicrobial interactions (22.6%); showed synergistic interactions (62.5%); multidrug-resistant showed increased susceptibility to select antibiotics; (inherently colistin resistant) became colistin-susceptible in polymicrobial combinations. Both antagonistic and synergistic interactions exist among human pathogens in polymicrobial settings. Gram-positive pathogens had significantly higher antagonistic polymicrobial interactions (increased MICs: 20.4%) compared with Gram-negative ones (synergistic: 59.4%).