Respiratory Commensal Bacteria Increase Protection against Hypermucoviscous Carbapenem-Resistant Klebsiella pneumoniae ST25 Infection

Abstract

In a previous work, we demonstrated that nasally administered Corynebacterium pseudodiphtheriticum 090104 beneficially modulated the respiratory innate immune response and improved the protection against Respiratory Syncytial Virus and Streptococcus pneumoniae in mice. In this work, we aimed to evaluate whether the immunomodulatory 090104 strain was able to enhance the resistance against the respiratory infection induced by hypermucoviscous carbapenemase-producing (KPC-2) Klebsiella pneumoniae strains belonging to the sequence type (ST) 25. The nasal treatment of mice with C. pseudodiphtheriticum 090104 before the challenge with multiresistant K. pneumoniae ST25 strains significantly reduced lung bacterial cell counts and lung tissue damage. The protective effect of the 090104 strain was related to its ability to regulate the respiratory innate immune response triggered by K. pneumoniae challenge. C. pseudifteriticum 090104 differentially modulated the recruitment of leukocytes into the lung and the production of TNF-α, IFN-γ and IL-10 levels in the respiratory tract and serum. Our results make an advance in the positioning of C. pseudodiphtheriticum 090104 as a next-generation probiotic for the respiratory tract and encourage further research of this bacterium as a promising alternative to develop non-antibiotic therapeutical approaches to enhance the prevention of infections produced by microorganisms with multiple resistance to antimicrobials such as KPC-2-producing hypermucoviscous K. pneumoniae strains belonging to ST25.

Keywords: Corynebacterium pseudodiphtheriticum; Klebsiella pneumoniae; antibiotic resistance; immunobiotic; next generation probiotics; respiratory commensal bacteria; respiratory immunity.

Figure 1

Effect of Corynebacterium pseudodiphtheriticum on lung colonization and damage induced by KPC-2-producing hypermucoviscous ST25 strains of Klebsiella pneumoniae. Immunocompetent adult BALB/c mice (6 weeks) were nasally stimulated with C. pseudodiphtheriticum 090104 for three days and then challenged nasally with K. pneumoniae LABACER 01 (Kp01) or LABACER 27 (Kp27). Two days after challenge, bacteria cell counts in lung homogenates, lactate dehydrogenase (LDH) enzyme activity and albumin concentration were determined in broncho-alveolar lavages (BAL). 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.

Figure 2

Effect of Corynebacterium pseudodiphtheriticum on respiratory and blood leukocytes counts induced by KPC-2-producing hypermucoviscous ST25 strains of Klebsiella pneumoniae. Immunocompetent adult BALB/c mice (6 weeks) were nasally stimulated with C. pseudodiphtheriticum 090104 for three days and then challenged nasally with K. pneumoniae LABACER 01 (Kp01) or LABACER 27 (Kp27). 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.

Figure 3

Effect of Corynebacterium pseudodiphtheriticum on respiratory and serum cytokines induced by KPC-2-producing hypermucoviscous ST25 strains of Klebsiella pneumoniae. Immunocompetent adult BALB/c mice (6 weeks) were nasally stimulated with C. pseudodiphtheriticum 090104 for three days and then challenged nasally with K. pneumoniae LABACER 01 (Kp01) or LABACER 27 (Kp27). Two days after challenge, TNF-α, IFN-γ and IL-10 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.