Oral Administration of Lacticaseibacillus rhamnosus CRL1505 Modulates Lung Innate Immune Response against Klebsiella pneumoniae ST25

Abstract

Orally administered Lacticaseibacillus rhamnosus CRL1505 enhances respiratory immunity, providing protection against respiratory viruses and Streptococcus pneumoniae. However, the capacity of the CRL1505 strain to improve respiratory immunity against Gram-negative bacterial infections has not been evaluated before. The aim of this work was to evaluate whether the Lcb. rhamnosus CRL1505 was able to beneficially regulate the respiratory innate immune response and enhance the resistance to hypermucoviscous KPC-2-producing Klebsiella pneumoniae of the sequence type 25 (ST25). BALB/c mice were treated with the CRL1505 strain via the oral route and then nasally challenged with K. pneumoniae ST25 strains LABACER 01 or LABACER 27. Bacterial cell counts, lung injuries and the respiratory and systemic innate immune responses were evaluated after the bacterial infection. The results showed that K. pneumoniae ST25 strains increased the levels of TNF-α, IL-1β, IL-6, IFN-γ, IL-17, KC and MPC-1 in the respiratory tract and blood, as well as the numbers of BAL neutrophils and macrophages. Mice treated with Lcb. rhamnosus CRL1505 had significantly lower K. pneumoniae counts in their lungs, as well as reduced levels of inflammatory cells, cytokines and chemokines in the respiratory tract and blood when compared to infected controls. Furthermore, higher levels of the regulatory cytokines IL-10 and IL-27 were found in the respiratory tract and blood of CRL1505-treated mice than controls. These results suggest that the ability of Lcb. rhamnosus CRL1505 to help with the control of detrimental inflammation in lungs during K. pneumoniae infection would be a key feature to improve the resistance to this pathogen. Although further mechanistic studies are necessary, Lcb. rhamnosus CRL1505 can be proposed as a candidate to improve patients' protection against hypermucoviscous KPC-2-producing strains belonging to the ST25, which is endemic in the hospitals of our region.

Keywords: K. pneumoniae; Lcb. rhamnosus CRL1505; innate immunity; probiotics.

Figure 1

Effect of Lacticaseibacillus rhamnosus CRL1505 on lung colonization and damage induced by KPC-2-producing hypermucoviscous Klebsiella pneumoniae ST25 strains. BALB/c mice (6 weeks old) were orally treated with the CRL1505 strain for 5 days and then challenged nasally with K. pneumoniae LABACER 01 (Kp01) or LABACER 27 (Kp27). Before (basal) and two days after challenge, bacteria cell counts in lung homogenates, broncho–alveolar lavages (BAL) lactate dehydrogenase (LDH) activity and albumin concentration were determined. Results represent data from three independent experiments. Asterisks indicate significant differences between the indicated groups, (*) p < 0.05, (**) p < 0.01. Basal levels of BAL albumin were below the detection limit. ND: not detected. Pink bars represent mice given Lcb. rhamnosus CRL1505 and blue bars represent control mice.

Figure 2

Effect of Lacticaseibacillus rhamnosus CRL1505 on respiratory and blood leukocytes numbers induced by KPC-2-producing hypermucoviscous Klebsiella pneumoniae ST25 strains. BALB/c mice (6 weeks old) were orally treated with the CRL1505 strain for 5 days and then challenged nasally with K. pneumoniae LABACER 01 (Kp01) or LABACER 27 (Kp27). Before (basal) and two days after challenge, total and differential leukocytes counts were determined in broncho–alveolar lavages (BAL) and blood. Results represent data from three independent experiments. Asterisks indicate significant differences between the indicated groups, (*) p < 0.05, (**) p < 0.01. Pink bars represent mice given Lcb. rhamnosus CRL1505 and blue bars represent control mice.

Figure 3

Effect of Lacticaseibacillus rhamnosus CRL1505 on respiratory and blood inflammatory cytokines induced by KPC-2-producing hypermucoviscous Klebsiella pneumoniae ST25 strains. BALB/c mice (6 weeks old) were orally treated with the CRL1505 strain for 5 days and then challenged nasally with K. pneumoniae LABACER 01 (Kp01) or LABACER 27 (Kp27). Before (basal) and two days after challenge, TNF-α, IL-1β and IL-6 levels were determined in broncho–alveolar lavages (BAL) and serum. Results represent data from three independent experiments. Asterisks indicate significant differences between the indicated groups, (*) p < 0.05, (**) p < 0.01. Pink bars represent mice given Lcb. rhamnosus CRL1505 and blue bars represent control mice.

Figure 4

Effect of Lacticaseibacillus rhamnosus CRL1505 on respiratory and blood inflammatory chemokines induced by KPC-2-producing hypermucoviscous Klebsiella pneumoniae ST25 strains. BALB/c mice (6 weeks old) were orally treated with the CRL1505 strain for 5 days and then challenged nasally with K. pneumoniae LABACER 01 (Kp01) or LABACER 27 (Kp27). Before (basal) and two days after challenge, KC and MCP-1 levels were determined in broncho–alveolar lavages (BAL) and serum. Results represent data from three independent experiments. Asterisks indicate significant differences between the indicated groups, (**) p < 0.01. Pink bars represent mice given Lcb. rhamnosus CRL1505 and blue bars represent control mice.

Figure 5

Effect of Lacticaseibacillus rhamnosus CRL1505 on respiratory and blood effector cytokines chemokines induced by KPC-2-producing hypermucoviscous Klebsiella pneumoniae ST25 strains. BALB/c mice (6 weeks old) were orally treated with the CRL1505 strain for 5 days and then challenged nasally with K. pneumoniae LABACER 01 (Kp01) or LABACER 27 (Kp27). Before (basal) and two days after challenge, IFN-γ and IL-17 levels were determined in broncho–alveolar lavages (BAL) and serum. Results represent data from three independent experiments. Asterisks indicate significant differences between the indicated groups, (*) p < 0.05, (**) p < 0.01. Pink bars represent mice given Lcb. rhamnosus CRL1505 and blue bars represent control mice.

Figure 6

Effect of Lacticaseibacillus rhamnosus CRL1505 on respiratory and blood regulatory cytokines chemokines induced by KPC-2-producing hypermucoviscous Klebsiella pneumoniae ST25 strains. BALB/c mice (6 weeks old) were orally treated with the CRL1505 strain for 5 days and then challenged nasally with K. pneumoniae LABACER 01 (Kp01) or LABACER 27 (Kp27). Before (basal) and two days after challenge, IL-10 and IL-27 levels were determined in broncho–alveolar lavages (BAL) and serum. Results represent data from three independent experiments. Asterisks indicate significant differences between the indicated groups, (*) p < 0.05, (**) p < 0.01. Pink bars represent mice given Lcb. rhamnosus CRL1505 and blue bars represent control mice.