Regulation divergences of Lactobacillus fermentum PCC and Lactobacillus paracasei 431 on penicillin-induced upper respiratory tract microbial dysbiosis in BALB/c mice

Antibiotic-induced host health imbalance during upper respiratory tract infection (URTI) treatment is an emerging issue. Studies have confirmed that Lactobacillus casei 431 and Lactobacillus fermentum PCC alleviate gut microbiome dysbiosis and improve immune response. However, their effect on the upper respiratory tract (URT) microbial structure and the correlation between the URT microbiota and immunological indicators remain unclear. To evaluate the effects of Lactobacillus strains on restoring penicillin-induced imbalance in the URT microbiome and on immune response, Lactobacillus fermentum PCC and Lactobacillus casei 431 were individually administered to penicillin-pretreated mice, and their effects were assessed. The results revealed that L. casei 431 and L. fermentum PCC could regulate the systemic immune response imbalance, but the regulation direction of L. fermentum PCC was closer to that of the control group. Moreover, the Lactobacillus strains could restore penicillin-induced URT dysbacteriosis in the microbial community structure, but no significant change in alpha diversity was observed. The key bacterial taxa modulated by L. casei 431 were Faecalibaculum, Lactococcus, and Ralstonia. L. fermentum PCC enhanced biofilms and facultatively anaerobic bacteria. Different regulation pathways were observed in the two strains, and RDA revealed that both L. casei 431 and L. fermentum PCC groups were correlated with IL-17 and IL-1α, while the L. casei 431 group was also correlated with IL-6. In conclusion, L. casei 431 and L. fermentum PCC could beneficially and differentially ameliorate penicillin-induced imbalance in the URT microbial composition structure and functional metabolic pathways and modulate immune response, reflecting strain-specific regulation.