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Effect of sub-lethal doses of vancomycin and oxacillin on biofilm formation by vancomycin intermediate resistant
Zulfiqar Ali Mirani1, Nusrat Jamil
1Department of Microbiology, University of Karachi, Pakistan.
Abstract:
Biofilms are means of protection to bacteria against antibiotics and antibodies. Catheters and others tube devices used by patients are prone to accumulation of thick layers of biofilms as hiding place for etiologic agents, resulting in substantial morbidity and mortality. Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of hospital-acquired infections. Vancomycin remains the only treatment of choice for MRSA infections. In the present study a vancomycin resistant S. aureus (VRSA) (Labeled as CP2) was isolated from the blood of a post-operative cardiac patient. It harbors a plasmid which carry vanA gene and exhibited low-level vancomycin resistance (MIC 16 μg/ml), high level of oxacillin/methicillin resistance (MIC 500 μg/ml) and was sensitive to teicoplanin. CP2 also found to carry icaA gene on its chromosome. This strain exhibited resistance to triton-X100 induced autolysis under sub-inhibitory concentration of vancomycin and produced some extracellular matrix material that surrounding the cells. These characteristic features have warranted us to study the biofilm formation by CP2 on biomedical indwellings in presence of vancomycin and oxacillin. Our findings suggest that sub-lethal dose of vancomycin induced the biofilm formation by CP2 on nylon and silicon indwellings whereas oxacillin facilitated the biofilm formation on glass surfaces exclusively. This implicates that not only the antibiotics but also the indwelling material influences biofilm formation. Therefore, these implants serve as potential surfaces for bacterial adhesion that lead to biofilm formation, thus provide hiding places for pathogens from the actions of antimicrobials.
Insights
Sub-lethal antibiotic doses can promote bacterial biofilm formation on medical devices. This study shows vancomycin and oxacillin induce biofilms on different materials, highlighting material influence on antimicrobial resistance.
Area of Science:
- Microbiology
- Infectious Diseases
- Biomaterials Science
Background:
- Bacterial biofilms protect microbes from antibiotics and host defenses, causing significant patient morbidity and mortality.
- Methicillin-resistant Staphylococcus aureus (MRSA) is a critical hospital-acquired pathogen, with vancomycin as a primary treatment.
- Emergence of vancomycin-resistant S. aureus (VRSA) poses a significant therapeutic challenge.
Purpose of the Study:
- To investigate biofilm formation by a clinical isolate of vancomycin-resistant S. aureus (VRSA) on biomedical indwelling materials.
- To determine the influence of sub-lethal concentrations of vancomycin and oxacillin on VRSA biofilm development.
- To assess the role of indwelling material type in modulating antibiotic-induced biofilm formation.
Main Methods:
- Isolation and characterization of a VRSA strain (CP2) with vanA and icaA genes from a patient's blood.
- Assessment of antibiotic resistance profiles (vancomycin, oxacillin, teicoplanin) and autolysis.
- In vitro biofilm formation assays using nylon, silicon, and glass surfaces in the presence of sub-inhibitory antibiotic concentrations.
Main Results:
- The isolated VRSA strain exhibited resistance to vancomycin and oxacillin, and produced extracellular matrix.
- Sub-lethal vancomycin significantly induced biofilm formation on nylon and silicon indwellings.
- Oxacillin specifically promoted biofilm formation on glass surfaces, indicating material-specific effects.
Conclusions:
- Sub-inhibitory antibiotic concentrations can paradoxically enhance bacterial biofilm formation on medical devices.
- Both antibiotic type and the biomaterial surface play crucial roles in modulating biofilm development.
- Medical implants can serve as reservoirs for pathogens, facilitating resistance to antimicrobial treatments.
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