Protective effect of intranasally inoculated Lactobacillus fermentum against Streptococcus pneumoniae challenge on the mouse respiratory tract

Abstract

Lactic acid bacteria are increasingly used to restore the ecological equilibrium of different mucosal areas in humans and/or animals. Likewise, they can be used to potentially protect against pathogenic microorganisms. In the present paper, the preventive effect of intranasally inoculated Lactobacillus fermentum against challenge with Streptococcus pneumoniae was studied, using a mouse experimental model. L. fermentum inoculated four times at a dose of 10(7) colony forming units per mouse was able to decrease the number of S. pneumoniae throughout the respiratory tract. The L. fermentum treatment increased the number of activated macrophages in lung slices, and a higher lymphocyte population in the tracheal lamina propria. S. pneumoniae challenge showed a typical response against pathogen with a higher non-specific immune response. Preventive treatment, i.e. L. fermentum administration prior to S. pneumoniae challenge, showed a response close to that of L. fermentum. Anti-S. pneumoniae antibodies increased in lactobacilli-treated animals compared to the non-treated lactobacilli mice. The increase in the antibody levels suggests that the mucosal immune system could be involved in the protective effect, accomplished with competitive exclusion, nutrient competition and production of inhibitory substances. This paper will be the basis for further studies of the protective effect of lactobacilli against S. pneumoniae in the respiratory tract.

Lactococcus lactisas an adjuvant and delivery vehicle of antigens against pneumococcal respiratory infections

“…44 Hussell and Humphreys 45 suggested that NALT could fulfill an important role by reducing the pathogen burden to a level that would induce only minimal inflammation in the lower lung. Using an experimental model of S. pneumoniae infection, Cangemi de Gutierrez et al 46 showed that the preventive intranasal inoculation of Lactobacillus fermentum caused a decrease in the number of pathogens throughout the respiratory tract together with an increase both in the number of activated macrophages in lung and in the lymphocyte population in the tracheal lamina propria. On the other hand, recombinant L. lactis NZ 9000 has been proven to elicit an immune response after inoculation by different mucosal routes.…”

Probiotics for the prevention of respiratory tract infections: a systematic review

“…However, experimental studies on animal models support the hypothesis for a potentially beneficial effect of probiotics on human RTIs. This could be mediated by the stimulation of cellular and humoral immunological functions [23][24][25][26][27][28][29].…”

Distal Mucosal Site Stimulation by Kefir and Duration of the Immune Response

“…This concept implies that oral immune stimulation can induce immunity in distal intestinal mucosal sites. For instance, the consumption offermented milk has been related to a reduced incidence of nasal pathogens (24)(25)(26). The majority of research concerning probiotic-mediated enhanced immune protection has focused on the gastrointestinal tract, and few studies have been conducted to consider the possibility that probiotics might stimulate the common mucosal immune system sufficiently to provide increased protection to other mucosal sites as well (27).…”