Correlation between group behavior and quorum sensing in Pseudomonas aeruginosa isolated from patients with hospital-acquired pneumonia

Background

This study investigated the correlation between the expression of the Las and Rhl quorum-sensing (QS) systems and the communal behavior (motility, biofilm formation, and pyocyanin production) of Pseudomonas aeruginosa (P. aeruginosa) isolated from patients with hospital-acquired pneumonia.

Methods

We analyzed 138 P. aeruginosa isolates from 48 patients (30 men and 18 women; age 68.18±15.08 years). P. aeruginosa clinical isolates were assessed for Las and Rhl gene expression and bacterial motility, biofilm formation, and pyocyanin production.

Results

P. aeruginosa swimming, twitching, and swarming motility positively correlated with the expression of LasI, LasR, and RhlI (P<0.05) but not with that of RhlR (P>0.05). At all analyzed time points, a significant positive correlation was found between biofilm formation and the expression of LasI, LasR (P<0.01), and RhlI (P<0.05 for day 1, P<0.01 for days 7 and 14), whereas RhlR expression positively correlated with biofilm formation only on day 14 (P<0.05). On days 1 and 7, positive correlation was observed between pyocyanin production and the levels of LasI and RhlI (P<0.05). In bacterial clearance cases, the expression of QS-related genes and the group behavior of the pathogen did not correlate (P>0.05). However, in cases of persistent P. aeruginosa infection, the changes in LasI and LasR gene expression were positively correlated with those in bacterial motility (P<0.05), and the changes in LasI, LasR, RhlI, and RhlR expression showed a significant positive association with those in biofilm formation (P<0.01).

Conclusions

In patients with hospital-acquired pneumonia, the expression of the Las and Rhl QS genes was associated with bacterial motility, biofilm formation, and pyocyanin production, suggesting an involvement of the QS genes in the clearance of pathogenic P. aeruginosa in patients.