Gene expression evaluation of teicoplanin-associated genes in Staphylococcus aureus under glycopeptide antibiotic stress

Background: The Staphylococcus aureus is Gram-positive, is implicated in infections that range in severity from skin disorders to life-threatening conditions like pneumonia and sepsis. Managing these infections has become increasingly difficult due to their rising resistance to multiple antibiotics, especially glycopeptides such as vancomycin. This research was designed to explore the influence of the tcaRAB operon—including the structural Teicoplanin-associated genes tcaA and tcaB, as well as the regulatory gene tcaR—on drug resistance and bacterial pathogenicity. Methods: Among 160 collected clinical samples, 25 isolates (15.6%) were identified as S. aureus through biochemical testing and automated VITEK analysis. The antimicrobial susceptibility profile revealed that all isolates were resistant to β-lactam antibiotics, such as oxacillin and cefoxitin, and that high levels of resistance were also seen for glycopeptides: vancomycin (92%) and teicoplanin (80%). Three isolates that exhibited pronounced multidrug resistance and high vancomycin resistance were selected for molecular analysis. TcaA, B and its regulator TcaR was detected in all Staphylococcus aureus isolates by conventional PCR, In addition, real-time PCR was performed to evaluate the expression level of the TcaR gene using the housekeeping gene gyrB as an internal control. Results: The results showed that Tca genes were detected in all S. aureus isolates with a ratio of 100%. Further, RT-qPCR assays demonstrated that sub-inhibitory concentrations of vancomycin suppressed the expression of tcaR, indicating that glycopeptide-induced stress may downregulate this regulator and possibly influence downstream resistance mechanisms. Conclusions: These findings provide additional support for considering the tcaRAB operon as a target for therapeutic strategies aimed at controlling MDR S. aureus strains.