Gene expression analysis of biofilm-associated and vancomycin stress-response genes in clinical Staphylococcus aureus

Document Type : Research Paper

Authors

1 Department of Biotechnology, College of Science, University of Baghdad, Iraq.

2 Department of Radiation Techniques, AlSalam University College, Baghdad, Iraq

3 General hospital, Al-Karkh Baghdad Health Directorate, Iraq.

4 Medical Doctor (General Practitioner), Baghdad, Iraq and Graduate of the Faculty of Medicine, Jordan University of Science and Technology, Jordan

10.22103/jab.2026.27221.1906

Abstract

Objective
Regulatory pathways involved in antibiotic resistance and biofilm formation in Staphylococcus aureus are complex and involve multiple genetic systems, including the vraSR stress-response pathway and the icaADBC operon. Understanding the transcriptional response of these genes under vancomycin exposure may provide insight into mechanisms associated with persistence and treatment failure. The study examined how clinical Staphylococcus aureus isolates react to vancomycin. The research also focused on antibiotic susceptibility and the activity of genes linked to biofilm growth (icaA, icaB, icaC, and icaD) and resistance (vra).
Materials and methods
Clinical isolates of Staphylococcus aureus were obtained from burn and wound specimens and confirmed by standard microbiological techniques. Vancomycin susceptibility was preliminarily evaluated using the agar well diffusion method. Total RNA was extracted from S. aureus cultures. Quantitative real-time PCR (qRT-PCR) was carried out using SYBR Green to perform expression analysis to track changes in the bacteria after exposure to the antibiotic.
Results
Testing showed that isolates responded differently to the drug. Several samples had very small or non-existent inhibition zones. These findings may indicate reduced susceptibility to vancomycin; however, confirmation using MIC-based assays is required. The qRT-PCR results showed that the icaADBC operon became more active after treatment. This change was most obvious in isolate 2. The data indicates that exposure to antibiotics might help the bacteria build stronger biofilms. This response is likely to help the bacteria survive and leads to treatment failure. The vra gene also showed strong activity across several isolates. This supports its role in managing cell wall stress. The hpr gene became more active too. This result suggests the gene might not stay stable enough to work as an internal control in these conditions.
Conclusions
The results show a clear connection between drug resistance and biofilm growth in S. aureus. Relying only on vancomycin for MRSA treatment has major drawbacks. Alternative therapeutic strategies targeting biofilm formation and cell wall stress-response pathways may improve treatment outcomes in persistent MRSA infections. These approaches could target the genes that control biofilm production. Another option is to find ways to block the vraSR system.

Keywords

References

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Agricultural Biotechnology Journal
Volume 18, Issue 3
June 2026
Pages 519-534

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