Detection sand Gene Expression of Regulatory Gene (icaR), and Its Control of the Expression of Biofilm Genes (icaA and icaD) in Staphylococcus aureus

Abstract

Introduction: The development of biofilms in Staphylococcus aureus (S. aureus) is heavily influenced by environmental factors and governed by multiple regulatory mechanisms, posing difficulties in the treatment of infections. S. aureus relies on the polysaccharide intercellular adhesin expressed by the icaADBC operon. A gene that influences the ica operon expression is the icaR gene, which is situated next to the icaADBC operon. The icaR gene encodes a negative regulator of icaADBC.

Aim: To investigate the correlation between the regulatory gene icaR and biofilm genes in S. aureus

Methods: Different clinical samples (n = 250) were collected from patients who attended Al-Husain Medical City and Al Imam Al Hassan Al Mujtaba Teaching Hospital in Karbala City from December 2021 to June 2022 for the isolation of S. aureus. The isolates were identified as S. aureus using cultural and biochemical assays. The susceptibility of S. aureus isolates to antibiotics was determined using the Kirby–Bauer disk diffusion method. The potential of S. aureus isolates for biofilm production was quantitatively evaluated using the microtitre plate method. After that, molecular detection of biofilm genes (icaA and icaD) and the regulatory gene (icaR) in bacterial isolates was done using Polymerase Chain Reaction (PCR). Finally, the expression of the biofilm genes and the regulatory gene was assessed using quantitative real-time PCR.

Results: Sixty isolates were identified as S. aureus from the 250 clinical samples. The antibiotic susceptibility of S. aureus isolates indicated multidrug resistance: 100% of isolates were resistant to oxacillin, 98% to penicillin P, 63% to tetracycline, 51% to azithromycin, 43% to doxycycline, 15% to gentamicin, 13.3% to levofloxacin, 13.3% to ciprofloxacin, 11.6% to trimethoprim, 10% to clindamycin, and 3.33% to chloramphenicol. Regarding the ability of S. aureus isolates for biofilm formation, 15 (25%) isolates were strong biofilm producers, 40 (66.6%) were moderate biofilm producers, and 5 (8.3%) were weak biofilm producers. Furthermore, all S. aureus isolates (100%) had biofilm genes (icaA and icaD) and the regulatory gene icaR. The upregulation of regulatory gene icaR was found to be associated with the downregulation of biofilm genes icaA and icaD in the isolates.
Conclusion: There is an inverse relationship between the biofilm ica operon and the regulatory gene icaR in S. aureus isolates.

Keywords: Staphylococcus aureus, Biofilm Formation, Biofilm Genes icaA, icaD, PIA/ica, Regulatory Gene icaR

How to cite this article:
Wannas Z M, Hassani H H. Detection sand Gene Expression of Regulatory Gene (icaR), and Its Control of the Expression of Biofilm Genes (icaA and icaD) in Staphylococcus aureus. J Commun Dis. 2026;58(1):35-46.

DOI: https://doi.org/ 10.24321/0019.5138.202605