Differential drug susceptibility to antibiotics in biofilm-producing Burkholderiales clinical isolates

Biofilm production and antimicrobial resistance in microorganisms of the order Burkholderiales is an emerging issue in nosocomial settings. The aim of this study was to assess the effect of conventional antibiotics on biofilm producer clinical isolates from the order Burkholderiales . Forty-four isolates ( Burkholderia spp ., Alcaligenes spp ., Achromobacter spp . y Ralstonia spp.) were selected during 2019–2023 from a third-level hospital in Mexico. After MALDI-TOF mass spectrometry identification, biofilm production was assessed by crystal violet staining. Drug susceptibility testing was determined by broth microdilution in planktonic cells and biofilm cells. In planktonic cells, low resistance to several antibiotics was observed in all Burkholderiales species, except ceftazidime ( Alcaligenes and Ralstonia ), ciprofloxacin ( Alcaligenes ) and trimethoprim-sulfamethoxazole ( Alcaligenes and Burkholderia ). Up to 75% of the strains were biofilm producers. In biofilm cells, trimethoprim-sulfamethoxazole, minocycline and levofloxacin were the only antibiotics with antibiofilm activity in Burkholderia strains. Drug resistance increased due to biofilm production for some antibiotics (trimethoprim-sulfamethoxazole, meropenem, ceftazidime, and fluoroquinolones), which could not eradicate mature biofilms in most strains. However, in Burkholderia strains, trimethoprim-sulfamethoxazole, minocycline and levofloxacin can eradicate mature biofilms and could be further studied for potential therapy options against biofilm-associated infections. The determination of specific drug concentrations required to eradicate biofilm-associated infections, is not routinely assessed by standard antimicrobial susceptibility testing. This study will provide additional information regarding therapy options against biofilm-associated Burkholderiales infections.