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

Antagonistic Effects of Corynebacterium pseudodiphtheriticum 090104 on Respiratory Pathogens

In previous studies, it was demonstrated that Corynebacterium pseudodiphtheriticum 090104, isolated from the human nasopharynx, modulates respiratory immunity, improving protection against infections. Here, the antagonistic effect of the 090104 strain on respiratory pathogens, including Streptococcus pneumoniae, Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii, was explored. In a series of in vitro studies, the capacity of C. pseudodiphtheriticum 090104, its bacterium-like particles, and its culture supernatants to coaggregate, inhibit the growth, and change the virulent phenotype of pathogenic bacteria was evaluated. The results showed that the 090104 strain was able to exert a bacteriostatic effect on K. pneumoniae and S. pneumoniae growth. In addition, C. pseudodiphtheriticum 090104 coaggregated, inhibited biofilm formation, and induced phenotypic changes in all the respiratory pathogens evaluated. In conclusion, this work demonstrated that, in addition to its beneficial effects exerted by host-microbe interactions, C. pseudodiphtheriticum 090104 can enhance protection against respiratory pathogens through its microbe-microbe interactions. The mechanisms involved in such interactions should be evaluated in future research.

Bacterium-like Particles from Corynebacterium pseudodiphtheriticum as Mucosal Adjuvant for the Development of Pneumococcal Vaccines

Previously, it was shown that intranasally (i.n.) administered Corynebacterium pseudodiphtheriticum 090104 (Cp) or CP-derived bacterium-like particles (BLPs) improve the immunogenicity of the pneumococcal conjugate vaccine (PCV). This work aimed to deepen the characterization of the adjuvant properties of Cp and CP-derived BLPs for their use in the development of pneumococcal vaccines. The ability of Cp and CP-derived BLPs to improve both the humoral and cellular specific immune responses induced by i.n. administered polysaccharide-based commercial pneumococcal vaccine (Pneumovax 23®) and the chimeric recombinant PSPF (PsaA-Spr1875-PspA-FliC) protein was evaluated, as well as the protection against Streptococcus pneumoniae infection in infant mice. Additionally, whether the immunization protocols, including Cp and CP-derived BLPs, together with the pneumococcal vaccines can enhance the resistance to secondary pneumococcal pneumonia induced after inflammatory lung damage mediated by the activation of Toll-like receptor 3 (TLR3) was assessed. The results showed that both Cp and CP-derived BLPs increased the immunogenicity and protection induced by two pneumococcal vaccines administered through the nasal route. Of note, the nasal priming with the PSPF T-dependent antigen co-administered with Cp or CP-derived BLPs efficiently stimulated humoral and cellular immunity and increased the resistance to primary and secondary pneumococcal infections. The CP-derived BLPs presented a stronger effect than live bacteria. Given safety concerns associated with live bacterium administration, especially in high-risk populations, such as infants, the elderly, and immunocompromised patients, BLPs emerge as an attractive mucosal adjuvant to improve the host response to pneumococcal infections and to enhance the vaccines already in the market or in development.

Hypermucoviscous Carbapenem-Resistant Klebsiella pneumoniae ST25 Infect Human Intestinal Epithelial Cells and Induce Moderate Inflammation

Klebsiella pneumoniae is an opportunistic pathogen that can produce moderate and severe infections in immunosuppressed hosts. In recent years, an increase in the isolation of hypermucoviscous carbapenem-resistant K. pneumoniae with sequence type 25 (ST25) in hospitals in Norwest Argentina was observed. This work aimed to study the virulence and inflammatory potential of two K. pneumoniae ST25 strains (LABACER01 and LABACER27) in the intestinal mucosa. The human intestinal Caco-2 cells were infected with the K. pneumoniae ST25 strains, and their adhesion and invasion rates and changes in the expression of tight junction and inflammatory factors genes were evaluated. ST25 strains were able to adhere and invade Caco-2 cells, reducing their viability. Furthermore, both strains reduced the expression of tight junction proteins (occludin, ZO-1, and claudin-5), altered permeability, and increased the expression of TGF-β and TLL1 and the inflammatory factors (COX-2, iNOS, MCP-1, IL-6, IL-8, and TNF-α) in Caco-2 cells. The inflammatory response induced by LABACER01 and LABACER27 was significantly lower than the one produced by LPS or other intestinal pathogens, including K. pneumoniae NTUH-K2044. No differences in virulence and inflammatory potential were found between LABACER01 and LABACER27. In line with these findings, no major differences between the strains were found when the comparative genomic analysis of virulence factors associated with intestinal infection/colonization was performed. This work is the first to demonstrate that hypermucoviscous carbapenem-resistant K. pneumoniae ST25 infects human intestinal epithelial cells and induces moderate inflammation.

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

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.

The Respiratory Commensal Bacterium Corynebacterium pseudodiphtheriticum as a Mucosal Adjuvant for Nasal Vaccines

Previously, we demonstrated that nasally administered Corynebacterium pseudodiphteriticum 090104 (Cp) or its bacterium-like particles (BLPs) increase the resistance of mice against bacterial and viral respiratory pathogens by modulating the innate immunity. In this work, we evaluated the ability of Cp and BLPs to stimulate alveolar macrophages, and to enhance the humoral immune response induced by a commercial vaccine against Streptococcus pneumoniae. In the first set of experiments, Cp or the BLPs were incubated with primary cultures of murine alveolar macrophages and the phagocytic activity, and the production of cytokines was evaluated. The results revealed that Cp and BLPs were efficiently phagocyted by respiratory macrophages and that both treatments triggered the production of TNF-α, IFN-γ, IL-6, and IL-1β. In the second set of experiments, 3-week-old Swiss mice were intranasally immunized at days 0, 14, and 28 with the pneumococcal vaccine Prevenar®13 (PCV), Cp + PCV, or BLPs + PCV. On day 33, samples of bronco-alveolar lavages (BAL) and serum were collected for the study of specific antibodies. In addition, immunized mice were challenged with S. pneumoniae serotypes 6B or 19F on day 33 and sacrificed on day 35 (day 2 post-infection) to evaluate the resistance to the infection. Both Cp + PCV and BLPs + PCV groups had higher specific serum IgG and BAL IgA antibodies than the PCV control mice. In addition, the mice that were immunized with Cp + PCV or BLPs + PCV had lower lung and blood pneumococcal cell counts as well as lower levels of BAL albumin and LDH, indicating a reduced lung damage compared to the control mice. Improved levels of anti-pneumococcal antibodies were also detected in the serum and BAL samples after the challenges with the pathogens. The results demonstrated that C. pseudodiphteriticum 090104 and its bacterium-like particles are capable of stimulating the respiratory innate immune system serving as adjuvants to potentiate the adaptive humoral immune response. Our study is a step forward in the positioning of this respiratory commensal bacterium as a promising mucosal adjuvant for vaccine formulations aimed at combating respiratory infectious diseases.

Immunomodulatory Effects of Probiotics: A Novel Preventive Approach for the Control of Bovine Mastitis

Bovine mastitis (BM) is one of the most common diseases of dairy cattle, causing economic and welfare problems in dairy farming worldwide. Because of the predominant bacterial etiology, the treatment of BM is mostly based on antibiotics. However, the antimicrobial resistance (AMR), treatment effectiveness, and the cost of mastitis at farm level are linked to limitations in the antibiotic therapy. These scenarios have prompted the quest for new preventive options, probiotics being one interesting alternative. This review article sought to provide an overview of the recent advances in the use of probiotics for the prevention and treatment of BM. The cellular and molecular interactions of beneficial microbes with mammary gland (MG) cells and the impact of these interactions in the immune responses to infections are revised. While most research has demonstrated that some probiotics strains can suppress mammary pathogens by competitive exclusion or the production of antimicrobial compounds, recent evidence suggest that other probiotic strains have a remarkable ability to modulate the response of MG to Toll-like receptor (TLR)-mediated inflammation. Immunomodulatory probiotics or immunobiotics can modulate the expression of negative regulators of TLR signaling in the MG epithelium, regulating the expression of pro-inflammatory cytokines and chemokines induced upon pathogen challenge. The scientific evidence revised here indicates that immunobiotics can have a beneficial role in MG immunobiology and therefore they can be used as a preventive strategy for the management of BM and AMR, the enhancement of animal and human health, and the improvement of dairy cow milk production.