Bacterial Adaptive Memory in Methicillin-Resistant Staphylococcus aureus from Endotracheal Tubes

To evaluate the expression dynamics of biofilm genes in methicillin-resistant (MRSA) retrieved from endotracheal tubes (ETT) and to determine how gene regulation is attenuated in vitro where host-environmental factors are no longer present. Biofilm was grown (24 h) in tryptic broth soy plus 0.25% glucose for a clinical MRSA isolate in planktonic state and after sessile growth named ETT-MRSA (S2, S3, S4, S5, S6, S7). Gene expression of five biofilm-related genes ( , , , , and ) was assessed consecutively from day 1 to day 4 after ETT growth through real-time PCR. 16S rRNA was used as a control. The MRSA isolates retrieved from ETT were capable of producing biofilms dependent on . The gene expression dynamics of ETT-MRSA changed progressively compared to planktonic MRSA gene expression under both ambient air ( < 0.001) and ambient air with 5% CO2 ( < 0.001). Dynamic assessment of expression in both atmospheric conditions showed progressive downregulation in vitro compared to in vivo ETT biofilms. The expression patterns of and genes were similar to In contrast, the expression of the gene showed progressive upregulation from day 1 to day 4 ( < 0.001). MRSA loses its biofilm gene expression in vitro, by adaptive features across multiple generations, as evidenced by the progressive downregulation of and upregulation of . These findings underscore the significance of host-environment dependence in regulating bacterial biofilm genes, highlighting its importance in diagnostics. Bacterial strains lose their host-specific characteristics as they are cultured in vitro.