In vitro study of antimicrobial activity on Klebsiella Pneumoniae biofilms in endotracheal tubes.

Effective treatment approaches for biofilms in endotracheal tubes (ETTs) are lacking. In this study, we evaluated the in vitro effects of five antimicrobials against biofilms formed by Klebsiella pneumoniae in ETTs. K. pneumoniae was added to minimal mucin medium prior to inoculation in microtiter plates containing ETT fragments. Biofilm susceptibility was assessed by crystal violet staining. At 24 h, the antimicrobials significantly reduced biofilm formation. At 48 h, all of the antimicrobial agents exhibited significant reductions in biofilm formation, even at concentrations above the minimum inhibitory concentration (MIC). Tigecycline and fosfomycin showed the greatest inhibition capacity, with good activity at concentrations twofold greater than the MIC. K. pneumoniae exhibited excellent biofilm formation ability, with formation in the first 24 h and significantly reduced antimicrobial activity. These results contribute to the establishment of new antibiotic breakpoints for the adequate management of infections associated with biofilm formation. Abbreviations ETT Endotracheal tube MIC Minimum inhibitory concentration MBIC Minimum biofilm inhibitory concentration OD Optical density PBS Phosphate-buffered saline VAP Ventilator-associated pneumonia.