Micro-rheological properties of lung homogenates correlate with infection severity in a mouse model of Pseudomonas aeruginosa lung infection

Abstract

Lung infections caused by Pseudomonas aeruginosa pose a serious threat to patients suffering from, among others, cystic fibrosis, chronic obstructive pulmonary disease, or bronchiectasis, often leading to life-threatening complications. The establishment of a chronic infection is substantially related to communication between bacteria via quorum-sensing networks. In this study, we aimed to assess the role of quorum-sensing signaling molecules of the Pseudomonas quinolone signal (PQS) and to investigate the viscoelastic properties of lung tissue homogenates of PA-infected mice in a prolonged acute murine infection model. Therefore, a murine infection model was successfully established via intra-tracheal infection with alginate-supplemented Pseudomonas aeruginosa NH57388A. Rheological properties of lung homogenates were analyzed with multiple particle tracking (MPT) and quorum-sensing molecules were quantified with LC–MS/MS. Statistical analysis of bacterial load and quorum-sensing molecules showed a strong correlation between these biomarkers in infected lungs. This was accompanied by noticeable changes in the consistency of lung homogenates with increasing infection severity. Furthermore, viscoelastic properties of the lung homogenates strongly correlated with bacterial load and quorum sensing molecules. Considering the strong correlation between the viscoelasticity of lung homogenates and the aforementioned biomarkers, the viscoelastic properties of infected lungs might serve as reliable new biomarker for the evaluation of the severity of P. aeruginosa infections in murine models.

Microrheology of Pseudomonas aeruginosa biofilms grown in wound beds

“…For in vitro biofilms, WT biofilm became more relatively elastic from 24 to 48 h. In vitro, the Δ mucA biofilm had α values identical to those of WT at 24 h but this value did not change with age. It is, therefore, less relatively elastic than the WT at 48 h. This appears to agree with previous findings that increased alginate production results in biofilms that have lower yield moduli both in vitro 28 and in ex vivo samples that were homogenized using mechanical agitation 29 . After 24 h, in vitro ∆pel biofilms were slightly more elastic than WT biofilms, although there was substantial overlap in the confidence bounds.…”

A New PqsR Inverse Agonist Potentiates Tobramycin Efficacy to Eradicate Pseudomonas aeruginosa Biofilms

“…Mice were infected via intratracheal instillation with an inoculum of 5•10 7 CFU/lung of the PA isolate NH57388A possessing functional PQS QS. [16] Animals were immediately treated with QSI 4 co-administered using methyl cellulose (dose = 5 mg kg −1 ) or vehicle (control), followed by further treatments at 24 and 48 h post-infection. The lungs were harvested at 72 h time point, homogenized and extracted using ethyl acetate.…”

“…In order to show in vivo efficacy of pathoblockers in general and QSI in particular, the application of predictive models is key. [16] The anti-virulence active agent does not interfere with bacterial viability. Hence, typical study endpoints like bacterial load do not reflect the inherent mode-of-action.…”

“…This enabled us to determine QS suppression in the lung compartment by quantifying the lev-els of the QS-associated metabolites three days post-infection. [16] These included the main alkylquinolone signal molecules PQS and HHQ (vide supra) as well as a close congener HQNO (2heptyl-4-quinolinol-1-oxide). [10] These outcomes are of clinical relevance, as the aforementioned metabolites were suggested to be prognostic biomarkers for PA infections in CF patients.…”

Pseudomonas aeruginosa in Bronchiectasis

“…94 Given this knowledge, the measurement of sputum viscoelasticity could be useful when personalizing therapy, could affect the virulence of PA biofilms, 49,94 and could be a reliable marker of PA infection status. 95…”