The small {RNA} {ErsA} plays a role in the regulatory network of Pseudomonas aeruginosa pathogenicity in airways infection

Bacterial small RNAs play a remarkable role in the regulation of functions involved in host-pathogen interaction. ErsA is a small RNA of Pseudomonas aeruginosa that contributes to the regulation of bacterial virulence traits such as biofilm formation and motility. Shown to take part in a regulatory circuit under the control of the envelope stress response sigma factor σ22, ErsA targets post-transcriptionally the key virulence-associated gene algC. Moreover, ErsA contributes to biofilm development and motility through the post-transcriptional modulation of the transcription factor AmrZ. Intending to evaluate the regulatory relevance of ErsA in the pathogenesis of respiratory infections, we analyzed the impact of ErsA-mediated regulation on the virulence potential of P. aeruginosa and the stimulation of the inflammatory response during the infection of bronchial epithelial cells and a murine model. Furthermore, we assessed ErsA expression in a collection of P. aeruginosa clinical pulmonary isolates and investigated the link of ErsA with acquired antibiotic resistance by generating an ersA gene deletion mutant in a multidrug-resistant P. aeruginosa strain which has long been adapted in the airways of a cystic fibrosis (CF) patient. Our results show that the ErsA-mediated regulation is relevant for the P. aeruginosa pathogenicity during acute infection and contributes to the stimulation of the host inflammatory response. Besides, ErsA could be subjected to selective pressure for P. aeruginosa patho-adaptation and acquirement of resistance to antibiotics commonly used in clinical practice during chronic CF infections. Our findings establish the role of ErsA as an important regulatory element in the host-pathogen interaction.