INFLUENCE OF IRON AVAILABILITY ON ANTIMICROBIAL RESISTANCE OF CORYNEBACTERIUM STRIATUM STRAINS ISOLATED FROM A NOSOCOMIAL OUTBREAK.

Corynebacterium striatum, a Gram-positive rod of the normal human microbiota, has emerged as a virulent, multidrug-resistant (MDR) pathogen, responsible for a growing number of invasive infections and nosocomial outbreaks worldwide. Previously considered a contaminant, its pathogenicity was recognized in the 1980s, with MDR strains frequently isolated in long-term hospitalized patients exposed to broad-spectrum antibiotics and invasive devices. Resistance to multiple antimicrobials has been common, with vancomycin and linezolid being the most effective agents in vitro. Iron is a vital cofactor, and its limited availability in the host is a common defense mechanism in bacterial infections. However, this adverse condition induces the microorganism to modify phenotypically and express virulence factors, with iron regulation being linked to pathogenicity in C. diphtheriae and other genera. Given the limited knowledge about this regulation in C. striatum, this study aimed to evaluate the influence of iron limitation and supplementation on the antimicrobial susceptibility profile of eight clinical strains isolated during and after a hospital outbreak in Rio de Janeiro. Iron limitation and supplementation altered the susceptibility profile of several strains to multiple antimicrobials. Four moxifloxacin-resistant strains became sensitive under iron limitation or supplementation. Conversely, the sensitive strain BR2376/X acquired an MDR profile under both conditions. Only vancomycin and linezolid maintained unchanged efficacy in all strains tested under all conditions. These changes strongly suggest the influence of metal-dependent transcriptional regulators on bacterial metabolism, and the formation of reactive oxygen species induced by changes in metal concentration, indicating that altering iron homeostasis can be considered a strategy to overcome antimicrobial resistance in C. striatum.