This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Biofilms are complex microbial communities that adhere to a surface and encase themselves in a viscous matrix they produce. This structure protects bacteria from antibiotics and the immune system far more effectively than if they lived in a free-floating state, making biofilms one of the most common causes of hard-to-treat chronic infections—such as respiratory infections in people with cystic fibrosis and chronic obstructive pulmonary disease (COPD), chronic wounds, or infections associated with catheters and prosthetic devices.
Added to this is the global rise in antibiotic resistance, which makes it increasingly urgent to have tools capable of predicting which treatment will work in each case. A team at the Institute for Bioengineering of Catalonia (IBEC) has developed XpertBiofilm, a simple and accessible device that allows biofilms to be grown under continuous, controlled liquid flow, similar to what bacteria encounter in the human body—for example, in lung mucus, blood or urine. The study, published in the journal Colloids and Surfaces B: Biointerfaces, was led by Eduard Torrents, principal investigator of the Bacterial Infections and Antimicrobial Therapies group and associate professor at the University of Barcelona, together with Núria Blanco-Cabra, a researcher in the same group and first author of the study.
Most laboratory systems used to study how biofilms form rely on static plates, where the culture medium does not move. In the body, however, bacteria almost never grow in a still environment: The flow of blood, mucus or other fluids constantly generates friction on surfaces, known as shear stress. To use an analogy, shear stress is similar to what a stone experiences in a riverbed: In stagnant water, it barely experiences any friction, but if the water flows strongly, that same stone is subject to constant drag and friction.
This is what the researchers analyze in this work, at a microscopic scale: the shear stress that a moving liquid exerts on any surface it comes into contact with, including the surfaces where bacteria adhere. Devices capable of reproducing this flow in a controlled way already exist, but they tend to be complex, expensive and require specialized microscopy and staff with advanced technical training to analyze the results, which limits their use. To overcome this limitation, the team designed and optimized the geometry of XpertBiofilm's growth chamber to achieve homogeneous flow and controlled shear stress over a small, removable piece (a round coverslip) on which the biofilm forms.
Once the biofilm has grown, this piece can be analyzed directly with a microplate reader, without the need for specialized microscopes, allowing for more accessible and streamlined observation. This finding is especially relevant in the context of cystic fibrosis and COPD, chronic lung diseases in which mucus is thicker and more viscous than usual and which are frequently complicated by Pseudomonas aeruginosa biofilm infections. In the lungs of these patients, shear stress is far below the levels found in a healthy lung (around 80 mPa) or those generated by coughing (up to 170,000 mPa).
The flow range that XpertBiofilm can reproduce in the laboratory—from 0.02 to 0.9 mPa—matches this low-shear-stress environment, which the authors highlight as supporting the device's clinical relevance for modeling lung infections in cystic fibrosis. Precisely within that low flow range, the team showed that the higher the flow, the more biofilm biomass P. aeruginosa forms—an opportunistic pathogen also very common in chronic wounds and infections associated with medical devices. According to the authors, this result helps explain why bacteria manage to adhere strongly to the airways in cystic fibrosis and why, given the very low shear stress present, the airways' ability to sweep away and clear bacteria is greatly reduced in these patients, leading to chronic infections.
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