Lung Bacterial Burden Research Articles

Nebulized Bacteriophages for Prophylaxis of Experimental Ventilator-Associated Pneumonia Due to Methicillin-Resistant Staphylococcus aureus.

There is a need for alternative strategies to combat and prevent antibiotic-resistant bacterial infections. Here, we assessed the potential for bacteriophage prophylaxis in the context of experimental ventilator-associated pneumonia due to methicillin-resistant Staphylococcus aureus in rats. Nebulized phages (aerophages) were delivered to the lungs of rats using a modified vibrating mesh aerosol drug delivery system. Animals were intubated and ventilated for 4 hours, at which point they were infected with methicillin-resistant S. aureus strain AW7 via the endotracheal tube, extubated, and then monitored for 96 hours. Ventilator-associated pneumonia. Male Wistar rats. A single application of aerophages prior to ventilation at one of two concentrations (~1010 plaque forming units/mL or ~1011 plaque forming units/mL). 1) Animal survival at 96 hours, 2) enumeration of bacteria and phages in the lungs and spleen, and 3) lung tissue histopathology. Animals that received aerophages prior to ventilation and methicillin-resistant S. aureus challenge showed a higher survival rate compared with untreated controls (60% for animals that received 3 × 10 plaque forming units; 70% for animals that received 3 × 10 plaque forming units; 0% for controls; p < 0.01 for each treatment versus untreated). Surviving animals that received aerophage prophylaxis had fewer methicillin-resistant S. aureus in the lungs compared with untreated control animals that succumbed to pneumonia (1.6 × 10 colony forming units/g vs 8.0 × 10; p < 0.01). Prophylactically administered nebulized bacteriophages reduced lung bacterial burdens and improved survival of methicillin-resistant S. aureus infected rats, underscoring its potential in the context of ventilator-associated pneumonia.

Early cytokine response to lethal challenge of Klebsiella pneumoniae averted the prognosis of pneumonia in FyuA immunized mice

Klebsiella pneumoniae, a multi drug resistant nosocomial pathogen is associated with pneumonia and immunization gives a hope to fight its infections. A possible vaccine candidate is the conserved protein, yersiniabactin receptor FyuA. Its expression along with the siderophore yersiniabactin increases in bacteria under iron starving conditions prevailing in lungs. In this study, the potential of recombinant FyuA of K. pneumoniae has been evaluated against lung infection in BALB/c mice. Immunization generated both humoral and cell mediated response which conferred protection against the lethal dose of bacteria. Bacterial burden in lungs reduced by 6 log10 CFU/ml after 2nd day post infection as compared to control. Similarly, the levels of pro-inflammatory cytokines IL-17, TNF-α and IL-1β were also reduced significantly; reduced tissue damage was evident from histopathology of lungs in immunized mice. These results indicate the protective role of FyuA which can be a potential vaccine candidate.

BCG vaccination reduces the mortality of Mycobacterium tuberculosis-infected type 2 diabetes mellitus mice.

Diabetes is a significant risk factor for the development of active tuberculosis. In this study, we used a mouse model of type 2 diabetes mellitus (T2DM) to determine the effect of prior Bacillus Calmette-Guérin (BCG) vaccination on immune responses to Mycobacterium tuberculosis (Mtb) infection. We found that, at 6-7 months after Mtb infection, 90% of the Mtb-infected T2DM mice died, whereas only 50% of BCG-vaccinated T2DM-Mtb-infected mice died. Moreover, 40% of the PBS-treated uninfected T2DM mice and 30% of the uninfected BCG-vaccinated T2DM mice died, whereas all uninfected and infected nondiabetic mice survived. BCG vaccination was less effective in reducing the lung bacterial burden of Mtb-infected T2DM mice compared with Mtb-infected nondiabetic mice. BCG vaccination significantly reduced lung inflammation in Mtb-infected T2DM mice compared with that of unvaccinated T2DM mice infected with Mtb. Furthermore, reduced mortality of BCG-vaccinated Mtb-infected T2DM mice is associated with expansion of IL-13-producing CXCR3+ Tregs in the lungs of Mtb-infected T2DM mice. Recombinant IL-13 and Tregs from BCG-vaccinated Mtb-infected T2DM mice converted proinflammatory M1 macrophages to antiinflammatory M2 macrophages. Our findings suggest a potentially novel role for BCG in preventing excess inflammation and mortality in T2DM mice infected with Mtb.

Monophosphoryl Lipid a Attenuates Multiorgan Dysfunction During Post-Burn Pseudomonas Aeruginosa Pneumonia in Sheep.

Monophosphoryl lipid A (MPLA) is a TLR4 agonist that has potent immunomodulatory properties and modulates innate immune function to improve host resistance to infection with common nosocomial pathogens in mice. The goal of this study was to assess the safety and efficacy of MPLA in a sheep model of burn injury and Pseudomonas aeruginosa pneumonia. The sheep provides a favorable model for preclinical testing as their response to TLR4 agonists closely mimics that of humans. Twelve chronically instrumented adult female Merino sheep received 20% total body surface area, third-degree cutaneous burn under anesthesia and analgesia. At 24 h after burn, sheep were randomly allocated to receive: MPLA (2.5 μg/kg i.v., n = 6), or vehicle (i.v., n = 6). At 24 h after MPLA or vehicle treatment, Pseudomonas aeruginosa pneumonia was induced. Sheep were mechanically ventilated, fluid resuscitated and cardiopulmonary variables were monitored for 24 h after induction of pneumonia. Cytokine production, vascular barrier function, and lung bacterial burden were also measured. MPLA infusion induced small and transient alterations in core body temperature, heart rate, pulmonary artery pressure, and pulmonary vascular resistance. Pulmonary mechanics were not altered. Vehicle-treated sheep developed severe acute lung injury during Pseudomonas aeruginosa pneumonia, which was attenuated by MPLA as indicated by improved PaO2/FiO2 ratio, oxygenation index, and shunt fraction. Sheep treated with MPLA also exhibited less vascular leak, lower blood lactate levels, and lower modified organ injury score. MPLA treatment attenuated systemic cytokine production and decreased lung bacterial burden. MPLA was well tolerated in burned sheep and attenuated development of acute lung injury, lactatemia, cytokinemia, vascular leak, and hemodynamic changes caused by Pseudomonas aeruginosa pneumonia.

Lung Microbiota Predict Clinical Outcomes in Critically Ill Patients.

Rationale: Recent studies have revealed that, in critically ill patients, lung microbiota are altered and correlate with alveolar inflammation. The clinical significance of altered lung bacteria in critical illness is unknown.Objectives: To determine if clinical outcomes of critically ill patients are predicted by features of the lung microbiome at the time of admission.Methods: We performed a prospective, observational cohort study in an ICU at a university hospital. Lung microbiota were quantified and characterized using droplet digital PCR and bacterial 16S ribosomal RNA gene quantification and sequencing. Primary predictors were the bacterial burden, community diversity, and community composition of lung microbiota. The primary outcome was ventilator-free days, determined at 28 days after admission.Measurements and Main Results: Lungs of 91 critically ill patients were sampled using miniature BAL within 24 hours of ICU admission. Patients with increased lung bacterial burden had fewer ventilator-free days (hazard ratio, 0.43; 95% confidence interval, 0.21-0.88), which remained significant when the analysis was controlled for pneumonia and severity of illness. The community composition of lung bacteria predicted ventilator-free days (P = 0.003), driven by the presence of gut-associated bacteria (e.g., species of the Lachnospiraceae and Enterobacteriaceae families). Detection of gut-associated bacteria was also associated with the presence of acute respiratory distress syndrome.Conclusions: Key features of the lung microbiome (bacterial burden and enrichment with gut-associated bacteria) predict outcomes in critically ill patients. The lung microbiome is an understudied source of clinical variation in critical illness and represents a novel therapeutic target for the prevention and treatment of acute respiratory failure.

A Blood RNA Signature in a Novel Murine Model Predicts Human Tuberculosis Risk

Tuberculosis (TB) is a highly heterogeneous disease that develops in a subset of individuals infected with aerosolized Mycobacterium tuberculosis (Mtb). We sought to develop an improved experimental model by infecting mice with an ultra-low dose (ULD, 1-3 founding Mtb bacteria), which is believed to reflect a physiologic inoculum. ULD-infected mice exhibited bacterial burdens ranging from <10 to 106 CFUs within individual lungs. Furthermore, they exhibited well-circumscribed granulomas that shared features with human granulomas. To monitor outcomes in live mice, we identified a blood RNA signature that correlated with lung bacterial burdens. Remarkably, this mouse-derived signature predicted Mtb infection outcomes across species, including disease scores in non-human primates and risk of progression to active TB in humans. Overall, the ULD mouse model recapitulates key features of human TB and provides a new platform to study the biology of Mtb infection in a tractable experimental system.

Unique patterns of lower respiratory tract microbiota are associated with inflammation and hospital mortality in acute respiratory distress syndrome

BackgroundThe lung microbiome maintains the homeostasis of the immune system within the lungs. In acute respiratory distress syndrome (ARDS), the lung microbiome is enriched with gut-derived bacteria; however, the specific microbiome associated with morbidity and mortality in patients with ARDS remains unclear. This study investigated the specific patterns of the lung microbiome that are correlated with mortality in ARDS patients.MethodsWe analyzed the lung microbiome from the bronchoalveolar lavage fluid (BALF) of patients with ARDS and control subjects. We measured the copy numbers of 16S rRNA and the serum and BALF cytokines (interleukin [IL]-6, IL-8, receptor for advanced glycation end products, and angiopoietin-2).ResultsWe analyzed 47 mechanically ventilated patients diagnosed with (n = 40) or without (n = 7; control) ARDS. The alpha diversity was significantly decreased in ARDS patients compared with that of the controls (6.24 vs. 8.07, P = 0.03). The 16S rRNA gene copy numbers tended to be increased in the ARDS group compared with the controls (3.83 × 106 vs. 1.01 × 105 copies/mL, P = 0.06). ARDS patients were subdivided into the hospital survivor (n = 24) and non-survivor groups (n = 16). Serum IL-6 levels were significantly higher in the non-survivors than in the survivors (567 vs. 214 pg/mL, P = 0.027). The 16S rRNA copy number was significantly correlated with serum IL-6 levels in non-survivors (r = 0.615, P < 0.05). The copy numbers and relative abundance of betaproteobacteria were significantly lower in the non-survivors than in the survivors (713 vs. 7812, P = 0.012; 1.22% vs. 0.08%, P = 0.02, respectively). Conversely, the copy numbers of Staphylococcus, Streptococcus and Enterobacteriaceae were significantly correlated with serum IL-6 levels in the non-survivors (r = 0.579, P < 0.05; r = 0.604, P < 0.05; r = 0.588, P < 0.05, respectively).ConclusionsThe lung bacterial burden tended to be increased, and the alpha diversity was significantly decreased in ARDS patients. The decreased Betaproteobacteria and increased Staphylococcus, Streptococcus and Enterobacteriaceae might represent a unique microbial community structure correlated with increased serum IL-6 and hospital mortality.Trial registrationThe institutional review boards of Hiroshima University (Trial registration: E-447-4, registered 16 October 2019) and Kyoto Prefectural University of Medicine (Trial registration: ERB-C-973, registered 19 October 2017) approved an opt-out method of informed consent.

2888. STAT4 Mutation in Three Generations with Disseminated Coccidioidomycosis (DCM) also Exhibits Increased Susceptibility to Coccidioidal Infection in Transfected Mice

BackgroundReported coccidioidomycosis has increased with case rates of 198/100,000 in Arizona (2012). In California alone, 2000–2011 hospitalizations were $2.2B. Dissemination occurs in 8% of reports with significant morbidity and occasional deaths. DCM was found in 3 generations: grandmother (skin), mother (skin), and son (bone). Whole exome sequencing identified a heterozygous (het) STAT4 mutation (p.E626G) in all three. This mutation alters the phosphotyrosine binding pocket and is predicted to impair STAT4 function, interfering with (i) receptor binding and phosphorylation, (ii) nuclear localization, and/or (iii) transcription. Expression profiling of antigen-stimulated peripheral blood mononuclear cells from one patient showed dampening of known STAT4 targets compared with controls.MethodsSTAT4 p.E626G was generated and confirmed in C57BL/6NJ (WT) mice using CRISPR-Cas9. With continued breeding, neither homozygous (hom) nor het mice had gross abnormalities. There were normal spleen and lung lymphoid cell numbers. Thymus and bone marrow had normal development of lymphoid subsets. We performed intranasal infection with reduced virulence C. posadasii strain 1038 or with F. tularensis live vaccine- strain (LVS). Naïve or Δcps1-vaccinated mice were tested for resistance to C. posadasii strain Silveira.ResultsAt day 21 post Cp 1038 infection, hom, het, and WT mice had similar lung fungal burdens (~104.7 cfu). All p.E626G mice died between days 31 and 39 with lung burden significantly higher (~9 × 106 cfu) than WT sacrificed on day 44 (7 × 105 cfu, P = 0.015). After LVS infection, p.E626G mice had increased lung bacterial cfu and all had dissemination to the spleen compared with WT lung bacterial burden and no splenic dissemination. Immunized het and WT mice all had significantly reduced lung cfu 14 days following C. posadasii infection compared with unvaccinated WT mice.ConclusionThe STAT4 p.E626G mutated mouse recapitulated patients’ increased susceptibility to coccidioidal infection. The decreased fungal burdens seen in Δcps1-vaccinated mice suggest that vaccination may be effective in those persons genetically susceptible to DCM. Given the increasing frequency and economic burdens of coccidioidomycosis, pursuit of vaccination strategies should continue. Disclosures All Authors: No reported Disclosures.

Tedizolid is a promising antimicrobial option for the treatment of Staphylococcus aureus infections in cystic fibrosis patients.

Tedizolid is a protein synthesis inhibitor in clinical use for the treatment of Gram-positive infections. Pulmonary MRSA infections are a growing problem in patients with cystic fibrosis (CF) and the efficacy of tedizolid-based therapy in CF pulmonary infections is unknown. To evaluate the in vitro and in vivo activity of tedizolid and predict the likelihood of tedizolid resistance selection in CF-background Staphylococcus aureus strains. A collection of 330 S. aureus strains (from adult and paediatric patients), either of normal or small colony variant (SCV) phenotypes, gathered at three CF centres in the USA was used. Tedizolid activity was assessed by broth microdilution, Etest and time-kill analysis. In vivo tedizolid efficacy was tested in a murine pneumonia model. Tedizolid in vitro mutants were obtained by 40 days of exposure and progressive passages. Whole genome sequencing of clinical S. aureus strains with reduced susceptibility to tedizolid was performed. MRSA strain MIC90s were tedizolid 0.12-0.25 mg/L and linezolid 1-2 mg/L; for MSSA strains, MIC90s were tedizolid 0.12 mg/L and linezolid 1-2 mg/L. Two strains, WIS 441 and Seattle 106, with tedizolid MICs of 2 mg/L and 1 mg/L, respectively, had MICs above the FDA tedizolid breakpoint (0.5 mg/L). Tedizolid at free serum concentrations exhibited a bacteriostatic effect. Mean bacterial burdens in lungs (log10 cfu/g) for WIS 423-infected mice were: control, 11.2±0.5; tedizolid-treated (10 mg/kg), 3.40±1.87; linezolid-treated (40 mg/kg), 4.51±2.1; and vancomycin-treated (30 mg/kg), 5.21±1.93. For WIS 441-infected mice the (log10 cfu/g) values were: control, 9.66±0.8; tedizolid-treated, 3.18±1.35; linezolid-treated 5.94±2.19; and vancomycin-treated, 4.35±1.7. These results suggest that tedizolid represents a promising therapeutic option for the treatment of CF-associated MRSA/MSSA infections, having potent in vivo activity and low resistance potential.

Plasma Eicosanoid Levels in Tuberculosis and Tuberculosis-Diabetes Co-morbidity Are Associated With Lung Pathology and Bacterial Burden.

Host eicosanoids are lipid mediators of inflammation that are commonly accepted as important modulators of the host immune response in Mycobacterium tuberculosis infection. During active tuberculosis (TB), eicosanoids may play an important role in the regulation of inflammatory responses. However, a detailed investigation of the relationship of eicosanoids in TB and TB-diabetes comorbidity (TB-DM) and association to disease pathology or bacterial burdens has not been studied. To study this, we examined the plasma levels of Lipoxin A4 (LXA4), 15-epi-LXA4, Leukotriene B4 (LTB4), and Prostaglandin E2 (PGE2) in individuals with either TB-DM, TB, diabetes mellitus (DM) or healthy controls (HC). Plasma levels of LXA4, 15-epi-LXA4, and PGE2 were significantly increased while the levels of LTB4 were significantly decreased in TB-DM and TB group compared to DM and HC. The ratio of LXA4 to LTB4 and 15-epiLXA4 to LTB4 was significantly enhanced in TB-DM compared to TB. Moreover, the levels of LXA4, 15-epi-LXA4 and the ratios of LXA4 to LTB4 and 15-epiLX4 to LTB4 were significantly increased in TB individuals with bilateral or cavitary disease and these markers also revealed a significant positive relationship with bacterial burden. At the completion of anti-tuberculosis therapy (ATT), levels of LXA4, 15-epi-LXA4, and PGE2 in TB-DM and TB groups were diminished and levels of LTB4 were enhanced in the TB group compared to pre-treatment. Our data imply that alteration and upregulation of eicosanoids are standard characteristics of TB-DM co-morbidity. Our data also demonstrate that modulation in the eicosanoid levels reflect disease severity and extent in TB and TB-DM and are modulated by ATT.

Streptococcus pneumoniae Evades Host Cell Phagocytosis and Limits Host Mortality Through Its Cell Wall Anchoring Protein PfbA.

Streptococcus pneumoniae is a Gram-positive bacterium belonging to the oral streptococcus species, mitis group. This pathogen is a leading cause of community-acquired pneumonia, which often evades host immunity and causes systemic diseases, such as sepsis and meningitis. Previously, we reported that PfbA is a β-helical cell surface protein contributing to pneumococcal adhesion to and invasion of human epithelial cells in addition to its survival in blood. In the present study, we investigated the role of PfbA in pneumococcal pathogenesis. Phylogenetic analysis indicated that the pfbA gene is highly conserved in S. pneumoniae and Streptococcus pseudopneumoniae within the mitis group. Our in vitro assays showed that PfbA inhibits neutrophil phagocytosis, leading to pneumococcal survival. We found that PfbA activates NF-κB through TLR2, but not TLR4. In addition, TLR2/4 inhibitor peptide treatment of neutrophils enhanced the survival of the S. pneumoniae ΔpfbA strain as compared to a control peptide treatment, whereas the treatment did not affect survival of a wild-type strain. In a mouse pneumonia model, the host mortality and level of TNF-α in bronchoalveolar lavage fluid were comparable between wild-type and ΔpfbA-infected mice, while deletion of pfbA decreased the bacterial burden in bronchoalveolar lavage fluid. In a mouse sepsis model, the ΔpfbA strain demonstrated significantly increased host mortality and TNF-α levels in plasma, but showed reduced bacterial burden in lung and liver. These results indicate that PfbA may contribute to the success of S. pneumoniae species by inhibiting host cell phagocytosis, excess inflammation, and mortality by interacting with TLR2.

Effect of Iron Supplementation on the Outcome of Non-Progressive Pulmonary Mycobacterium tuberculosis Infection.

The human response to Mycobacterium tuberculosis (Mtb) infection is affected by the availability of iron (Fe), which is necessary for proper immune cell function and is essential for the growth and virulence of bacteria. Increase in host Fe levels promotes Mtb growth and tuberculosis (TB) pathogenesis, while Fe-supplementation to latently infected, asymptomatic individuals is a significant risk factor for disease reactivation. However, the effect of Fe-supplementation on the host immunity during latent Mtb infection remains unclear, due partly to the paucity in availability of animal models that recapitulate key pathophysiological features seen in humans. We have demonstrated that rabbits can develop non-progressive latency similar to infected humans. In this study, using this model we have evaluated the effect of Fe-supplementation on the bacterial growth, disease pathology, and immune response. Systemic and lung Fe parameters, gene expression profile, lung bacterial burden, and disease pathology were determined in the Mtb-infected/Fe- or placebo-supplemented rabbits. Results show that Fe-supplementation to Mtb-infected rabbits did not significantly change the hematocrit and Hb levels, although it elevated total Fe in the lungs. Expression of selected host iron- and immune-response genes in the blood and lungs was perturbed in Mtb-infected/Fe-supplemented rabbits. Iron-supplementation during acute or chronic stages of Mtb infection did not significantly affect the bacterial burden or disease pathology in the lungs. Data presented in this study is of significant relevance for current public health policies on Fe-supplementation therapy given to anemic patients with latent Mtb infection.

Surprising synergy of dual translation inhibition vs. Acinetobacter baumannii and other multidrug-resistant bacterial pathogens

BackgroundMultidrug-resistant (MDR) Acinetobacter baumannii infections have high mortality rates and few treatment options. Synergistic drug combinations may improve clinical outcome and reduce further emergence of resistance in MDR pathogens. Here we show an unexpected potent synergy of two translation inhibitors against the pathogen: commonly prescribed macrolide antibiotic azithromycin (AZM), widely ignored as a treatment alternative for invasive Gram-negative pathogens, and minocycline, among the current standard-of-care agents used for A. baumannii. MethodsMedia-dependent activities of AZM and MIN were evaluated in minimum inhibitory concentration assays and kinetic killing curves, alone or in combination, both in standard bacteriologic media (cation-adjusted Mueller-Hinton Broth) and more physiologic tissue culture media (RPMI), with variations of bicarbonate as a physiologic buffer. Synergy was calculated by fractional inhibitory concentration index (FICI). Therapeutic benefit of combining AZM and MIN was tested in a murine model of A. baumannii pneumonia. AZM + MIN synergism was probed mechanistically by bacterial cytological profiling (BCP), a quantitative fluorescence microscopy technique that identifies disrupted bacterial cellular pathways on a single cell level, and real-time kinetic measurement of translation inhibition via quantitative luminescence. AZM + MIN synergism was further evaluated vs. other contemporary high priority MDR bacterial pathogens. FindingsAlthough two translation inhibitors are not expected to synergize, each drug complemented kinetic deficiencies of the other, speeding the initiation and extending the duration of translation inhibition as verified by FICI, BCP and kinetic luminescence markers. In an MDR A. baumannii pneumonia model, AZM + MIN combination therapy decreased lung bacterial burden and enhanced survival rates. Synergy between AZM and MIN was also detected vs. MDR strains of Gram-negative Klebsiella pneumoniae and Pseudomonas aeruginosa, and the leading Gram-positive pathogen methicillin-resistant Staphylococcus aureus. InterpretationAs both agents are FDA approved with excellent safety profiles, clinical investigation of AZM and MIN combination regimens may immediately be contemplated for optimal treatment of A. baumannii and other MDR bacterial infections in humans. FundNational Institutes of Health U01 AI124326 (JP, GS, VN) and U54 HD090259 (GS, VN). IC was supported by the UCSD Research Training Program for Veterinarians T32 OD017863.

Bacterial killing is enhanced by exogenous administration of lysozyme in the lungs

ObjectiveLysozyme, a 14-kDa protein, is one of the most abundant antimicrobials in the lungs. Its concentration in airway surface sufficient to kill several bacterial pathogens in vitro. The purpose of this study was to determine if administration of exogenous lysozyme would further enhance bacterial killing in vivo. MethodsTo assess the effect of acute lung infection on endogenous lysozyme protein levels, mice were infected by intratracheal instillation of Pseudomonas aeruginosa and bronchoalveolar (BAL) fluid assessed for lysozyme concentration and for muramidase activity. In order to inform in vivo testing, species-specific bacterial killing efficacy was determined by incubating mucoid P. aeruginosa with 2×105 units of chicken lysozyme, human lysozyme or with vehicle at 37°C for 2hours. Subsequently, mice challenged with intratracheally-administered mucoid P. aeruginosa, were reintubated and injected with 2×105 Units of native human lysozyme, recombinant human lysozyme or with vehicle. Lung bacterial burden was enumerated subsequently. ResultsThe concentration of lysozyme protein in BAL fluid from mice challenged with mucoid clinical isolate of P. aeruginosa was increased 4-fold at 6hours post-infection. Quantitative culture showed that the number of recoverable bacteria was significantly decreased by both chicken and human lysozyme compared to vehicle but human lysozyme was significantly more effective than chicken egg lysozyme. In vivo, 24hours post-infection quantitative culture of lung homogenates showed that the number of viable bacteria recovered from mice treated with either native or recombinant lysozyme was decreased with 0.76±0.25×104 and 0.84±0.16×104, respectively, vs. 7.0±2.52×104 CFU/g protein in mice treated with HBSS, both P<0.05. ConclusionsThese results indicate that endogenous lysozyme is increased during acute lung infection and that early administration of exogenous lysozyme further enhances bacterial killing in vivo.

Caspase 11 Negatively Regulates Carbapenem-resistant Klebsiella Pneumoniae (CRKP)-induced Pneumonia

Abstract Background CRKP remains one of the major causes of health-care associated infections worldwide. Due to its multi-drug resistance property, host-targeted immunotherapy is a promising alternative to treat CRKP-infections. Caspase11, a non-canonical inflammasome, has been shown to protect against cytosolic bacterial pathogens. However, its role in CRKP-induced pneumonia remains elusive. Methods We used C57BL/6 (WT) and Caspase 11 knock out (KO) mice to induce pneumonia by intratracheal inoculation of 108 colony forming units (CFUs) of CRKP per mouse. In E coli-induced pneumonia model, 106 CFUs per mouse was used. Results Using a mouse model of CRKP-induced pneumonia, we found that Caspase 11 KO mice were protected from intratracheal CRKP infection. The KO mice had significantly less bacterial burden in lungs and BALF compared to their wild-type counterparts. Total leukocytes and neutrophil recruitment into the air spaces were significantly higher in KO mice. To determine whether the phenotype is specific to CRKP infection, we induced pneumonia in WT and KO mice using E. coli through intratracheal route. Consistent with CRKP model, the KO mice displayed protective phenotype during pulmonary E coli challenge suggesting that the phenotype observed in the KO mice is not specific to single bacterium. Further, the KO mice had less IL-1β, CXCL1, and CXCL2 but higher amount of IL-17A secreted in the lungs suggesting that IL-17A could mediate neutrophil recruitment in the KO mice during pulmonary CRKP infection. Conclusions Our findings together demonstrate that Caspase 11 negatively regulates CRKP-induced pneumonia and blocking Caspase 11 could be a potential therapeutic intervention for treating CRKP-infected pneumonic patients.

Prior Bacillus Calmette-Guérin (BCG) vaccination ameliorates the pathogenesis of Type 2 diabetes mellitus mice infected with Mycobacterium tuberculosis

Abstract Previously, we found experimentally induced type 2 diabetes mellitus (T2DM) mice are highly susceptible to Mycobacterium tuberculosis (Mtb) infection. In the present study, we determined whether prior BCG vaccination has any effect on the susceptibility of T2DM mice infected with Mtb. C57BL/6 mice were vaccinated with BCG or treated with PBS, three months later some mice were induced with T2DM and after another month fifty percent of all groups of mice were challenged with Mtb. All Mtb infected T2DM mice and 40% of uninfected T2DM mice died within 10 months. In contrast, only 40% of Mtb infected BCG vaccinated T2DM mice and 20% of uninfected BCG vaccinated T2DM mice died. Lung bacterial burden was significantly less in Mtb infected BCG vaccinated T2DM mice compared to PBS treated Mtb infected mice. Pro and anti-inflammatory cytokine levels were significantly high in the lungs of Mtb infected BCG vaccinated T2DM mice compared to all other groups of vaccinated and PBS treated mice infected with Mtb. Our findings suggest that prior BCG vaccination protects Mtb infected mice from T2DM induced pathogenesis. Studies are underway to determine the BCG induced mechanism/s those protect T2DM mice challenged with Mtb.

Lung Microbiota Contribute to Pulmonary Inflammation and Disease Progression in Pulmonary Fibrosis.

Rationale: Idiopathic pulmonary fibrosis (IPF) causes considerable global morbidity and mortality, and its mechanisms of disease progression are poorly understood. Recent observational studies have reported associations between lung dysbiosis, mortality, and altered host defense gene expression, supporting a role for lung microbiota in IPF. However, the causal significance of altered lung microbiota in disease progression is undetermined. Objectives: To examine the effect of microbiota on local alveolar inflammation and disease progression using both animal models and human subjects with IPF. Methods: For human studies, we characterized lung microbiota in BAL fluid from 68 patients with IPF. For animal modeling, we used a murine model of pulmonary fibrosis in conventional and germ-free mice. Lung bacteria were characterized using 16S rRNA gene sequencing with novel techniques optimized for low-biomass sample load. Microbiota were correlated with alveolar inflammation, measures of pulmonary fibrosis, and disease progression. Measurements and Main Results: Disruption of the lung microbiome predicts disease progression, correlates with local host inflammation, and participates in disease progression. In patients with IPF, lung bacterial burden predicts fibrosis progression, and microbiota diversity and composition correlate with increased alveolar profibrotic cytokines. In murine models of fibrosis, lung dysbiosis precedes peak lung injury and is persistent. In germ-free animals, the absence of a microbiome protects against mortality. Conclusions: Our results demonstrate that lung microbiota contribute to the progression of IPF. We provide biological plausibility for the hypothesis that lung dysbiosis promotes alveolar inflammation and aberrant repair. Manipulation of lung microbiota may represent a novel target for the treatment of IPF.

Human Adipose-Derived Mesenchymal Stem Cells Modify Lung Immunity and Improve Antibacterial Defense in Pneumosepsis Caused by Klebsiella pneumoniae.

Adult mesenchymal stem cells exert immunomodulatory effects that might improve the host response during sepsis. Knowledge on the effect of adipose‐derived mesenchymal stem cells (ASCs) in sepsis is limited. Klebsiella (K.) pneumoniae is a common cause of gram‐negative pneumonia and sepsis. This study sought to determine the effect of human ASCs on the host response during pneumosepsis in mice. Mice were infected with K. pneumoniae via the airways to induce a gradually evolving infection in the lung culminating pneumosepsis. One or 6 hours after infection, mice were infused intravenously with ASCs or vehicle, and euthanized after 16 hours or 48 hours, respectively. The effects of freshly cultured and cryopreserved ASCs were compared, the latter formulation being more clinically relevant. Intravenously administered ASCs were visualized in lung tissue by immunostaining at 1 and 3 hours, but not at 15 hours after infusion. Although early after infection, ASCs did not or only modestly influence bacterial loads, they reduced bacterial burdens in lungs and distant organs at 48 hours. ASCs reduced the lung levels of pro‐inflammatory cytokines and attenuated lung pathology, but did not influence distant organ injury. ASCs strongly modified the lung transcriptome in uninfected mice and especially mice with pneumosepsis. Cryopreserved and cultured ASCs induced largely similar effects on the lung transcriptome. These data indicate that human ASCs induce profound immune modulatory effects in the lungs, resulting in reduced bacterial burdens and lung inflammation during pneumosepsis caused by a common human pathogen, suggesting that ASCs may be an adjunctive therapeutic in this condition. stem cells translational medicine 2019;8:785&796

Preventing lung pathology and mortality in rabbit Staphylococcus aureus pneumonia models with cytotoxin-neutralizing monoclonal IgGs penetrating the epithelial lining fluid

Staphylococcus aureus pneumonia is associated with high mortality irrespective of antibiotic susceptibility. Both MRSA and MSSA strains produce powerful cytotoxins: alpha-hemolysin(Hla) and up to five leukocidins – LukSF-PV, HlgAB, HlgCB, LukED and LukGH (LukAB) – to evade host innate defense mechanisms. Neutralizing cytotoxins has been shown to provide survival benefit in rabbit S. aureus pneumonia models. We studied the mechanisms of protection of ASN100, a combination of two human monoclonal antibodies (mAbs), ASN-1 and ASN-2, that together neutralize Hla and the five leukocidins, in rabbit MRSA and MSSA pneumonia models. Upon prophylactic passive immunization, ASN100 displayed dose-dependent increase in survival and was fully protective against all S. aureus strains tested at 5 or 20 mg/kg doses. Macroscopic and microscopic lung pathology, edema rate, and bacterial burden were evaluated 12 hours post infection and reduced by ASN100. Pharmacokinetic analysis of ASN100 in bronchoalveolar-lavage fluid from uninfected animals detected efficient penetration to lung epithelial lining fluid reaching peak levels between 24 and 48 hours post dosing that were comparable to the mAb concentration measured in serum. These data confirm that the ASN100 mAbs neutralize the powerful cytotoxins of S. aureus in the lung and prevent damage to the mucosal barrier and innate immune cells.

Lung Bacterial Burden is Increased Following the Onset of Chronic Rejection

Purpose Increased burden of lung bacteria is common in chronic lung diseases, is correlated with decreased lung function, and predicts disease progression. Bacterial burden is increased following lung transplant, but the relationship between bacterial burden and allograft dysfunction is unknown. Methods We obtained 294 bronchoalveolar lavage (BAL) fluid specimens from 214 unique lung transplant recipients. We quantified lung bacterial burden as number of 16S rRNA copies per mL of BAL fluid using droplet digital PCR (Bio-Rad), a novel, ultrasensitive platform. The onset of chronic lung allograft dysfunction (CLAD) was determined using the standard definition of the first of two consecutive FEV1 measurements ≤80% post-transplant baseline. Bacterial burden was compared using the Wilcoxon rank-sum test and percentages were compared using the Chi-square test. Results We compared 145 (49%) BAL specimens collected while patients were CLAD-free (largely for routine surveillance) with 149 (51%) BAL specimens collected after developing CLAD. Bacterial culture results did not differ between the two groups, with 19 (13%) CLAD free samples having positive cultures and 33 (22%) samples positive cultures after the onset of CLAD (p=0.07). However, using culture-independent methods, we found a higher bacterial burden in BAL samples collected after developing CLAD than in the CLAD free samples (p Conclusion Lung bacterial burden is increased following the onset of CLAD. Further investigation will determine the pathogenic and clinical significance of airway dysbiosis in the progression of lung allograft dysfunction.