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Updated: Mar 3, 2026
Targeting Biofilm Associated Staphylococcus aureus Using Resazurin Based Drug-susceptibility Assay
Published on: May 5, 2016
Increased drug resistance of meticillin-resistant Staphylococcus aureus biofilms formed on a mouse dermal chip model
Shiro Jimi1, Motoyasu Miyazaki2, Tohru Takata3
1Central Laboratory for Pathology and Morphology, Faculty of Medicine, Fukuoka University, Fukuoka, Japan.
Purpose:
Meticillin-resistant Staphylococcus aureus (MRSA) biofilm formation in humans is of serious clinical concern. Previous in vitro studies have been performed with biofilms grown only on inorganic substrates; therefore, we investigated the vancomycin (VCM) resistance of MRSA biofilms grown on skin tissue.
Methodology:
We established a novel tissue substrate model, namely MRSA grown on segments of mouse skin tissue (dermal chips, DCs), and compared its resistance capacity against VCM with that of MRSA biofilms grown on plastic chips (PCs).Results/Key findings. For one MRSA isolate, we found that the VCM MIC was identical (1.56 µg ml-1) for planktonic cultures and for biofilms-formed on PCs (PC-BF), although the minimum bactericidal concentration (MBC) increased to 6.25 µg ml-1 in PC-BF. On the contrary, the MIC and MBC for biofilms formed on DCs (DC-BF) significantly increased (25 and 50 µg ml-1, respectively). Furthermore, the minimum biofilm-eradicating concentration was higher for DC-BF (100 µg ml-1) than for PC-BF (25 µg ml-1). Using six MRSA strains, we found that in PC-BF, the c.f.u. number decreased with increasing VCM concentration, whereas in DC-BF, it greatly increased until the MIC was reached, accompanied by the formation of large colonies, thicker bacterial walls and the presence of many mitotic cells.
Conclusion:
Our results indicate that the VCM resistance of MRSA was greater in DC-BF. We conclude that DCs may provide a specific environment for MRSA that enhances bacterial growth under cytotoxic VCM concentrations, and might be useful for the study of skin wound infections and the effects of antimicrobial drugs.
Insights
Meticillin-resistant Staphylococcus aureus (MRSA) biofilms show increased vancomycin (VCM) resistance on skin tissue compared to plastic. This suggests skin provides a unique environment enhancing MRSA growth against VCM.
Area of Science:
- Microbiology
- Infectious Diseases
- Dermatology
Background:
- Meticillin-resistant Staphylococcus aureus (MRSA) biofilm formation poses significant clinical challenges.
- Previous in vitro studies on MRSA biofilms were limited to inorganic substrates.
Purpose of the Study:
- To investigate vancomycin (VCM) resistance of MRSA biofilms grown on skin tissue.
- To compare VCM resistance of MRSA biofilms on dermal chips (DCs) versus plastic chips (PCs).
Main Methods:
- Established a novel model of MRSA biofilms grown on mouse skin tissue (dermal chips).
- Compared VCM resistance (MIC, MBC, MBEC) of MRSA biofilms on DCs with those on PCs.
- Analyzed bacterial growth, colony formation, cell wall thickness, and mitotic activity under VCM exposure.
Main Results:
- MRSA biofilms on DCs exhibited significantly higher VCM MIC and MBC compared to biofilms on PCs.
- The minimum biofilm-eradicating concentration for DC-grown biofilms was substantially higher than for PC-grown biofilms.
- MRSA biofilms on DCs showed increased bacterial growth and colony formation with VCM, unlike PC biofilms.
Conclusions:
- Dermal chips (skin tissue) provide a specific environment that enhances MRSA growth and VCM resistance.
- This model is valuable for studying skin wound infections and antimicrobial drug efficacy.
- MRSA biofilms on skin tissue demonstrate greater resistance to vancomycin than previously observed.
