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bioRxiv · 10.1101/2025.09.14.676195

Biofilm Formation by Pseudomonas aeruginosa in Medium Supplemented with Adult Bovine Serum and the Anti-Biofilm Activity of β-Lactam Antibiotics

Mitsuyama, J.·Asano, K.·Morinaga, Y.
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Abstract

Pseudomonas aeruginosa is a major opportunistic pathogen known for its ability to form biofilms in vivo, which contributes significantly to its resistance to antimicrobial treatment. In this study, we examined the biofilm-forming capacity of a clinical isolate cultured in medium supplemented with 30% adult bovine serum (ABS). Under these host-mimicking conditions, mature biofilms developed on microplate surfaces within 8 hours. Among the {beta}-lactam antibiotics evaluated, piperacillin and cefoperazone exhibited potent anti-biofilm activity at concentrations as low as 1/8,192 to 1/256 of their respective minimum inhibitory concentrations (MICs). In contrast, ceftazidime and meropenem required significantly higher concentrations (approximately 1/16 MIC) to produce similar effects. The anti-biofilm activity of piperacillin and cefoperazone was abolished when ABS was defatted with n-hexane or when magnesium sulfate was added to the medium, suggesting that a lipid-dependent membrane permeabilization mechanism may be involved. These findings highlight the utility of host-mimicking conditions in evaluating the activity of antibiotics against biofilms and suggest that certain {beta}-lactam agents may have previously unrecognized anti-biofilm effects mediated through serum-associated components.

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Mitsuyama, J., Asano, K., Morinaga, Y.. 2025-09-17. Biofilm Formation by Pseudomonas aeruginosa in Medium Supplemented with Adult Bovine Serum and the Anti-Biofilm Activity of β-Lactam Antibiotics. https://doi.org/10.1101/2025.09.14.676195

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