Investigation of ciprofloxacin penetration into Pseudomonas aeruginosa biofilms

TLDR

Bacterial infections on indwelling devices frequently exhibit intrinsic resistance to antimicrobial therapies. The study investigated whether transport limitations affect ciprofloxacin penetration into Pseudomonas aeruginosa biofilms. ATR/FT‑IR spectroscopy was used to monitor biofilm colonization, ciprofloxacin transport to the interface, and antibiotic–biofilm interactions in a flowing system. Ciprofloxacin penetration was significantly impeded by the biofilm, and antibiotic exposure caused chemical changes in biofilm RNA/DNA, indicating transport limitations contribute to biofilm resistance and that ATR/FT‑IR can track antimicrobial action.

Abstract

Bacterial infections associated with indwelling medical devices often demonstrate an intrinsic resistance to antimicrobial therapies. In order to explore the possibility of transport limitation to biofilm bacteria as a contributing factor, the penetration of a fluoroquinolone antibiotic, ciprofloxacin, through Pseudomonas aeruginosa biofilms was investigated. Attenuated total reflection Fourier transform infrared (ATR/FT-IR) spectrometry was employed to monitor bacterial colonization of a germanium substratum, transport of ciprofloxacin to the biofilm-substratum interface, and interaction of biofilm components with the antibiotic in a flowing system. Transport of the antibiotic to the biofilm-substratum interface during the 21-min exposure to 100 micrograms/ml was found to be significantly impeded by the biofilm. Significant changes in IR bands of the biofilm in regions of the spectrum associated with RNA and DNA vibrational modes appeared following exposure to the antibiotic, indicating chemical modification of biofilm components. These results suggest that transport limitations may be an important factor in the antimicrobial resistance of biofilm bacteria and that ATR/FT-IR spectrometry may be used to follow the time course of antimicrobial action in biofilms in situ.