Abstract
BackgroundPseudomonas aeruginosa is an opportunistic pathogen that significantly increases morbidity and mortality in nosocomial infections and cystic fibrosis patients. Its pathogenicity especially relies on the production of virulence factors or resistances to many antibiotics. Since multiplication of antibiotic resistance can lead to therapeutic impasses, it becomes necessary to develop new tools for fighting P. aeruginosa infections. The use of probiotics is one of the ways currently being explored. Probiotics are microorganisms that exert a positive effect on the host’s health and some of them are known to possess antibacterial activities. Since most of their effects have been shown in the digestive tract, experimental data compatible with the respiratory environment are strongly needed. The main goal of this study was then to test the capacity of lactobacilli to inhibit major virulence factors (elastolytic activity and biofilm formation) associated with P. aeruginosa pathogenicity.ResultsSixty-seven lactobacilli were isolated from the oral cavities of healthy volunteers. These isolates together with 20 lactobacilli isolated from raw milks, were tested for their capacity to decrease biofilm formation and activity of the elastase produced by P. aeruginosa PAO1. Ten isolates, particularly efficient, were accurately identified using a polyphasic approach (API 50 CHL, mass-spectrometry and 16S/rpoA/pheS genes sequencing) and typed by pulsed-field gel electrophoresis (PFGE). The 8 remaining strains belonging to the L. fermentum (6), L. zeae (1) and L. paracasei (1) species were sensitive to all antibiotics tested with the exception of the intrinsic resistance to vancomycin. The strains were all able to grow in artificial saliva.ConclusionEight strains belonging to L. fermentum, L. zeae and L. paracasei species harbouring anti-elastase and anti-biofilm properties are potential probiotics for fighting P. aeruginosa pulmonary infections. However, further studies are needed in order to test their innocuity and their capacity to behave such as an oropharyngeal barrier against Pseudomonas aeruginosa colonisation in vivo.
Highlights
Pseudomonas aeruginosa is an opportunistic pathogen that significantly increases morbidity and mortality in nosocomial infections and cystic fibrosis patients
They belonged to 9 Lactobacillus species (Table 1), with a strong representativeness of the Lactobacillus reuteri and Lactobacillus casei groups with respectively 40 and 21 isolates
We previously showed in a murine model of P. aeruginosa pneumonia, that elastolytic activity was positively correlated to acute lung injury [5]
Summary
Pseudomonas aeruginosa is an opportunistic pathogen that significantly increases morbidity and mortality in nosocomial infections and cystic fibrosis patients. Probiotics are microorganisms that exert a positive effect on the host’s health and some of them are known to possess antibacterial activities. Since most of their effects have been shown in the digestive tract, experimental data compatible with the respiratory environment are strongly needed. Mortality exclusive use of antibiotics may lead to therapeutic impasses and it is necessary to find new therapeutic options to fight P. aeruginosa pulmonary infections. In this context, the use of probiotic bacteria, either as prophylactic agents for preventing or delaying pulmonary colonisation with P. aeruginosa, or eventually as therapeutic tool to fight P. aeruginosa infections, seems to be attractive. The lack of rational work for the selection of probiotic strains adapted to the respiratory ecosystem may be one of the reasons explaining the poor results obtained in certain studies
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