An Isolate of Streptococcus mitis Displayed In Vitro Antimicrobial Activity and Deleterious Effect in a Preclinical
Elliot Mathieu1,2, Quentin Marquant3,4, Florian Chain1,2
1Micalis Institute, Institut National de Recherche pour L'Agriculture, L'Alimentation et L'Environnement (INRAE), AgroParisTech, Université Paris-Saclay, UMR1319, F-78350 Jouy-en-Josas, France.
Abstract:
Microbiota studies have dramatically increased over these last two decades, and the repertoire of microorganisms with potential health benefits has been considerably enlarged. The development of next generation probiotics from new bacterial candidates is a long-term strategy that may be more efficient and rapid with discriminative in vitro tests. Streptococcus strains have received attention regarding their antimicrobial potential against pathogens of the upper and, more recently, the lower respiratory tracts. Pathogenic bacterial strains, such as non-typable Haemophilus influenzae (NTHi), Pseudomonas aeruginosa (P. aeruginosa) and Staphylococcus aureus (S. aureus), are commonly associated with acute and chronic respiratory diseases, and it could be interesting to fight against pathogens with probiotics. In this study, we show that a Streptococcus mitis (S. mitis) EM-371 strain, isolated from the buccal cavity of a human newborn and previously selected for promising anti-inflammatory effects, displayed in vitro antimicrobial activity against NTHi, P. aeruginosa or S. aureus. However, the anti-pathogenic in vitro activity was not sufficient to predict an efficient protective effect in a preclinical model. Two weeks of treatment with S. mitis EM-371 did not protect against, and even exacerbated, NTHi lung infection.
Insights
A novel probiotic strain, Streptococcus mitis EM-371, showed in vitro antimicrobial activity against respiratory pathogens. However, this strain failed to protect against NTHi lung infection in a preclinical model, even worsening the condition.
Area of Science:
- Microbiology
- Probiotics Research
- Respiratory Pathogen Studies
Background:
- Microbiota research has expanded, identifying new beneficial microorganisms.
- Next-generation probiotics require efficient in vitro screening methods.
- Streptococcus strains show potential against upper and lower respiratory tract pathogens.
Purpose of the Study:
- To evaluate the in vitro antimicrobial activity of Streptococcus mitis EM-371 against key respiratory pathogens.
- To assess the efficacy of S. mitis EM-371 in a preclinical model of NTHi lung infection.
Main Methods:
- Isolation and in vitro testing of Streptococcus mitis EM-371 against NTHi, P. aeruginosa, and S. aureus.
- Preclinical mouse model to evaluate the protective effect of S. mitis EM-371 against NTHi lung infection over two weeks.
Main Results:
- S. mitis EM-371 demonstrated in vitro antimicrobial activity against NTHi, P. aeruginosa, and S. aureus.
- In vivo treatment with S. mitis EM-371 did not protect against NTHi lung infection.
- The probiotic treatment exacerbated the NTHi lung infection in the preclinical model.
Conclusions:
- In vitro antimicrobial activity alone is insufficient to predict in vivo efficacy for probiotic candidates.
- S. mitis EM-371 is not suitable for preventing or treating NTHi lung infections.
- Further research is needed to develop reliable in vitro methods for next-generation probiotic selection.
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