Lactobacilli intra-tracheal administration protects from Pseudomonas aeruginosa pulmonary infection in mice – a proof of concept

Abstract

The spreading of antibiotic resistance is a major public health issue, which requires alternative treatments to antibiotics. Lactobacilli have shown abilities to prevent pneumonia in clinical studies when given by oral route, certainly through the gut-lung axis involvement. Rationally, respiratory administration of lactobacilli has been developed and studied in murine model, to prevent from respiratory pathogens. It allows a direct effect of probiotics into the respiratory system. To our knowledge, no study has ever focused on the effect of probiotic intra-respiratory administration to prevent from Pseudomonas aeruginosa (PA) pneumonia, a major respiratory pathogen associated with high morbidity rates. In this study, we evaluated the beneficial activity of three Lactobacillus strains (Lactobacillus fermentum K.C6.3.1E, Lactobacillus zeae Od.76, Lactobacillus paracasei ES.D.88) previously screened by ourselves and known to be particularly efficient in vitro in inhibiting PAO1 virulence factors. Cytotoxic assays in alveolar epithelial cell line A549 were performed, followed by the comparison of two lactobacilli prophylactic protocols (one or two administrations) by intra-tracheal administration in a C57BL/6 murine model of PA pneumonia. A549 cells viability was improved from 23 to 75% when lactobacilli were administered before PAO1 incubation, demonstrating a protective effect (P<0.001). A significant decrease of 2 log of PAO1 was observed 4 h after PAO1 instillation (3×106 cfu/mouse) in both groups receiving lactobacilli (9×106 cfu/mouse) compared to PAO1 group (P<0.05). One single prophylactic administration of lactobacilli significantly decreased the secretion by 50% in bronchoalveolar lavages of interleukin (IL)-6 and tumour necrosis factor-α compared to PAO1. No difference of secretion was observed for the IL-10 secretion, whatever the prophylactic study design. This is the first study highlighting that direct lung administration of Lactobacillus strains protect against PA pneumonia. Next step will be to decipher the mechanisms involved before developing this novel approach for human applications.

Gut Microbiota Modulation as a Potential Target for the Treatment of Lung Infections

“…In addition, the administration of L. rhamnosus GG induces an anti-inflammatory response by increasing the levels of regulatory T cells (Treg) Foxp3+ and decreasing the production of the proinflammatory cytokine IL-6. This anti-inflammatory profile was also observed in mice infected with P. aeruginosa with intratracheal administration of probiotics L. fermentum K.C6.3.1E, L. zeae Od.76, and L. paracasei ES.D.88, demonstrated by the reduction of lung inflammation and decreased production of IL-6 and tumor necrosis factor (TNF)-α ( Fangous et al, 2019 ).…”

Lung-Directed Bacteriotherapy in Cystic Fibrosis: Could It Be an Option?

“…Inhaled probiotics could directly compete with pathogens for adhesion to lung mucosa, interfere with pathogen growth and virulence, enhance the integrity of the lung mucosal barrier, and stimulate a local immune response while dampening an excessive inflammatory response (Figure 1). This strategy has demonstrated its efficacy in mice in a number of studies focused on bacterial and viral infections of the respiratory tract [58][59][60][61][62][63][64][65]. Among them, intra-tracheal administration of a mixture of three lactobacilli (L. fermentum K.C6.3.1E, L. paracasei ES.D.88, L. zeae Od.76) was recently demonstrated to protect mice from P. aeruginosa pulmonary infection by reducing the bacterial load in the lung and modulating the cytokine levels [64].…”

Perspectives on Probiotics and Bronchopulmonary Dysplasia

“…They consider that L. paracasei simultaneously augments the health status of IAV and influenza-meningococcal infection in mice, by attracting interstitial monocytes and DCs (63). In addition, intratracheal administration of Lactobacillus probably suppresses the PAO1 virulence factor and reduces IL-6 and TNFα activities, affecting lung infection outcome by Pseudomonas aeruginosa in mice (64).…”