Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen that can cause severe pulmonary infection in immunocompromized individuals. During the infectious process, P. aeruginosa provokes a potent inflammatory response and induces the release of reactive oxygen species (ROS). Cells undergo oxidative stress when cellular antioxidants are unable to effectively scavenge and detoxify ROS, resulting in lung damage. Resveratrol (3,5,4'-trihydroxystilbene) is a natural polyphenolic compound with recognized antioxidant effects. We hypothesized that owing to its antioxidant activities, resveratrol can attenuate an inflammatory response in P. aeruginosa-infected cells. Lung epithelial A549 cells were pre-treated with 100 μmol/L of resveratrol for 5 h, followed by infection with P. aeruginosa. Intracellular ROS generation was used as an indicator of P. aeruginosa-induced oxidative stress, and cell surface expression of Fas receptor and activation of caspases-3 and -7 as indicators of apoptosis. We also measured the surface expression of intercellular adhesion molecule (ICAM)-1 and enzymes related to inflammation and redox signaling. Resveratrol significantly reduced ROS generation, ICAM-1, and human beta-defensin-2 expression, as well as the markers of apoptosis in A549 cells infected with P. aeruginosa, and up-regulated glutathione peroxidase, suggesting its potential therapeutic role in protecting the lungs against the deleterious effects of P. aeruginosa infection.

Pseudomonas aeruginosa is an opportunistic Gram-negative pathogen, which is the major cause of severe chronic lung infection in cystic fibrosis patients. It is also responsible for systemic infections in immunocompromised individuals and those presenting with significant pulmonary conditions in intensive care units. This microorganism has the capacity to initiate severe inflammation in infected lungs resulting in detrimental tissue damage. We have hypothesized that Syk protein tyrosine kinase mediates lung epithelial cellular responses to P. aeruginosa infection, and that a naturally occurring non-toxic Syk inhibitor piceatannol can protect infected human cells against the deleterious effects associated with this infection. We infected Syk-positive H292 or Syk-negative A549 human lung epithelial cell lines with P. aeruginosa and assessed the resulting cellular responses, i.e. production of proinflammatory cytokines, adhesion molecule expression, generation of reactive oxygen species, and apoptosis of infected cells, utilizing a multiplex bead-based immunoassay and flow cytometry. We also studied the internalization of P. aeruginosa using the gentamicin exclusion assay. We found that the piceatannol treatment significantly suppressed inflammation, oxidative stress and apoptosis in H292, but not in A549 cells implicating Syk participation in the regulation of the pathological processes induced by P. aeruginosa infection. Intriguingly, piceatannol was able to down-regulate the internalization of P. aeruginosa by both Syk-positive and Syk-negative cell lines, implying that the mechanisms of action of this compound extend beyond Syk inhibition. As piceatannol can interfere with several mechanisms of bacterial pathogenesis this natural compound deserves further study as a potential therapeutic option in P. aeruginosa infection.

In the post-Haemophilus influenzae serotype b (Hib) vaccine era, invasive H. influenzae serotype a (Hia) disease emerged in Canadian First Nation, Inuit, and Alaskan Indigenous populations. Previous studies by our group found a high incidence of invasive Hia disease in northwestern Ontario. We retrospectively reviewed 24 cases (4 pediatric and 20 adult) of invasive H. influenzae disease hospitalized at the northwestern Ontario regional hospital between August 2011 and June 2018. The objectives were to further document the changing epidemiology of invasive H. influenzae disease in the region and to discuss potential control measures. Twenty-two H. influenzae isolates were serotyped and characterized using molecular-biological methods. Of the serotyped cases, there were 2 Hib, 9 Hia, and 11 non-typeable (NTHi). All Hia isolates belonged to the most common sequence types (ST) found in Canada (ST-23 and ST-929); 8 out of 9 were pan susceptible to antibiotics. One (11%) of 9 Hia and 5 (45%) of 11 NTHi cases were fatal. Our data on the consistent presence of serious invasive H. influenzae disease, with 41% prevalence of Hia (9 out of 22 serotyped isolates) and 50% prevalence of NTHi strains (11 out of 22), emphasize the importance of continued surveillance of H. influenzae in the post-Hib vaccine era and are critical information to inform potential vaccine development.

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