Mechanisms of Bacterial Colonization of the Respiratory Tract

Nano-metal-organic-frameworks for treating H2O2-Secreting bacteria alleviate pulmonary injury and prevent systemic sepsis

As a vital bacteria-secreted toxin, hydrogen peroxide (H₂O₂) can destroy infected tissues and increase vascular permeability, leading to life-threatening systemic bacteremia or sepsis. No strategy that can alleviate H₂O₂-induced injury and prevent systemic sepsis has been reported. Herein, as a proof of concept, we demonstrate the use of H₂O₂-reactive metal-organic framework nanosystems (MOFs) for treating H₂O₂-secreting bacteria. In mice infected with Streptococcus pneumoniae (S. pneumoniae) isolated from patients, MOFs efficiently accumulate in the lungs after systemic administration due to infection-induced alveolar-capillary barrier dysfunction. Moreover, MOFs sequester pneumococcal H₂O₂, reduce endothelial DNA damage, and prevent systemic dissemination of bacteria. In addition, this nanosystem exhibits excellent chemodynamic bactericidal effects against drug-resistant bacteria. Through synergistic therapy with the antibiotic ampicillin, MOFs eliminate over 98% of invading S. pneumoniae, resulting in a survival rate of greater than 90% in mice infected with a lethal dose of S. pneumoniae. This work opens up new paths for the clinical treatment of toxin-secreting bacteria.

Expression, purification and preliminary characterisation of the choline transporter LicB from opportunistic bacterial pathogens

Many opportunistic bacteria that infect the upper respiratory tract decorate their cell surface with phosphorylcholine to support colonisation and outgrowth. These surface modifications require the active import of choline from the host environment, a process thought to be mediated by a family of dedicated integral membrane proteins that act as choline permeases. Here, we present the expression and purification of the archetype of these choline transporters, LicB from Haemophilus influenzae. We show that LicB can be recombinantly produced in Escherichia coli and purified to homogeneity in a stable, folded state using the detergent n-dodecyl-β-d-maltopyranoside. Equilibrium binding studies with the fluorescent ligand dansylcholine suggest that LicB is selective towards choline, with reduced affinity for acetylcholine and no apparent activity towards other small molecules including glycine, carnitine and betaine. We also identify a conserved sequence motif within the LicB family and show that mutations within this motif compromise protein structure and function. Our results are consistent with previous observations that LicB is a specific high-affinity choline transporter, and provide an experimental platform for further studies of this permease family.

Effects of nasopharyngeal microbiota in respiratory infections and allergies

The human microbiome, which consists of a collective cluster of commensal, symbiotic, and pathogenic microorganisms living in the human body, plays a key role in host health and immunity. The human nasal cavity harbors commensal bacteria that suppress the colonization of opportunistic pathogens. However, dysbiosis of the nasal microbial community is associated with many diseases, such as acute respiratory infections including otitis media, sinusitis and bronchitis and allergic respiratory diseases including asthma. The nasopharyngeal acquisition of pneumococcus, which exists as a pathobiont in the nasal cavity, is the initial step in virtually all pneumococcal diseases. Although the factors influencing nasal colonization and elimination are not fully understood, the adhesion of opportunistic pathogens to nasopharyngeal mucosa receptors and the eliciting of immune responses in the host are implicated in addition to bacterial microbiota properties and colonization resistance dynamics. Probiotics or synbiotic interventions may show promising and effective roles in the adjunctive treatment of dysbiosis; however, more studies are needed to characterize how these interventions can be applied in clinical practice in the future.

3D Hierarchical Polyaniline-Metal Hybrid Nanopillars: Morphological Control and Its Antibacterial Application

Effective and reliable antibacterial surfaces are in high demand in modern society. Although recent works have shown excellent antibacterial performance by combining unique hierarchical nanotopological structures with functional polymer coating, determining the antibacterial performance arising from morphological changes is necessary. In this work, three-dimensional (3D) hierarchical polyaniline–gold (PANI/Au) hybrid nanopillars were successfully fabricated via chemical polymerization (i.e., dilute method). The morphology and structures of the PANI/Au nanopillars were controlled by the reaction time (10 min to 60 h) and the molar concentrations of the monomer (0.01, 0.1, and 1 M aniline), oxidant (0.002, 0.0067, 0.01, and 0.02 M ammonium persulfate), and acid (0.01, 0.1, 1, and 2 M perchloric acid). These complex combinations allow controlling the hierarchical micro- to nanostructure of PANI on a nanopillar array (NPA). Furthermore, the surface of the 3D PANI/Au hierarchical nanostructure can be chemically treated while maintaining the structure using initiated chemical vapor deposition. Moreover, the excellent antibacterial performance of the 3D PANI/Au hierarchical nanostructure (HNS) exceeds 99% after functional polymer coating. The excellent antibacterial performance of the obtained 3D PANI/Au HNS is mainly because of the complex topological and physicochemical surface modification. Thus, these 3D PANI/Au hierarchical nanostructures are promising high-performance antibacterial materials.

Anti-Inflammatory Properties of Fructo-Oligosaccharides in a Calf Lung Infection Model and in Mannheimia haemolytica-Infected Airway Epithelial Cells

Emerging antimicrobial-resistant pathogens highlight the importance of developing novel interventions. Here, we investigated the anti-inflammatory properties of Fructo-oligosaccharides (FOS) in calf lung infections and in airway epithelial cells stimulated with pathogens, and/or bacterial components. During a natural exposure, 100 male calves were fed milk replacer with or without FOS for 8 weeks. Then, immune parameters and cytokine/chemokine levels in the bronchoalveolar lavage fluid (BALF) and blood were measured, and clinical scores were investigated. Calf primary bronchial epithelial cells (PBECs) and human airway epithelial cells (A549) were treated with Mannheimia haemolytica, lipopolysaccharides (LPS), and/or flagellin, with or without FOS pretreatment. Thereafter, the cytokine/chemokine levels and epithelial barrier function were examined. Relative to the control (naturally occurring lung infections), FOS-fed calves had greater macrophage numbers in BALF and lower interleukin (IL)-8, IL-6, and IL-1β concentrations in the BALF and blood. However, FOS did not affect the clinical scores. At slaughter, FOS-fed calves had a lower severity of lung lesions compared to the control. Ex vivo, FOS prevented M. haemolytica-induced epithelial barrier dysfunction. Moreover, FOS reduced M. haemolytica- and flagellin-induced (but not LPS-induced) IL-8, TNF-α, and IL-6 release in PBECs and A549 cells. Overall, FOS had anti-inflammatory properties during the natural incidence of lung infections but had no effects on clinical symptoms.

Neutrophil infiltration in co-housed littermates plays a key role in nasal transmission of Streptococcus pneumoniae in an infant mouse model

Transmission plays an important role in establishing pneumococcal colonization. It comprises three key events: shedding to transmit, entering into a susceptible new host, and adhering to the mucosal surface. Shedding of pneumococci from the respiratory tract of a colonized host is a pivotal step in transmission. Using a co-housed littermate mouse model, we evaluated the importance of the susceptibility to colonization of Streptococcus pneumoniae TIGR4 strain shed from index pups to non-colonized naïve contact pups. Despite sufficient pneumococcal shedding from the colonized host, S. pneumoniae was not contagious between littermates. Neutrophils infiltrated the nasal mucosa of contact pups and contributed to susceptibility of pneumococcal colonization during the course of transmission. Rejection of pneumococcal colonization in the contact pups was associated with accumulation of neutrophils in the nasal mucosa. Inflammation, characterized by neutrophil infiltration, prevents newly entering pneumococci from adhering to the respiratory epithelium in contact mice, suggesting that it plays an important role in reducing the rate of transmission in the initial response of naïve susceptible hosts to pneumococcal acquisition. The initial response of contact mice may regulate neutrophil and/or macrophage infiltration and control the acquisition of existing pneumococci.

Drug-Eluting Endotracheal Tubes for Preventing Bacterial Inflammation in Subglottic Stenosis

OBJECTIVES/HYPOTHESIS

Subglottic stenosis (SGS) results from dysregulated extracellular matrix deposition by laryngotracheal fibroblasts causing scar tissue formation following intubation. Recent work has highlighted a relationship between this inflammatory state and imbalances in the upper airway microbiome. Herein, we engineer novel drug-eluting endotracheal (ET) tubes to deliver a model antimicrobial peptide Lasioglossin-III (Lasio) for the local modulation of the microbiome during intubation.

STUDY DESIGN

Controlled in vitro study.

METHODS

ET tubes were coated with a water-in-oil (w/o) emulsion of Lasio in poly(d,l-lactide-co-glycolide) (PLGA) by dipping thrice. Peptide release was quantified over 2 weeks via fluorometric peptide assays. The antibacterial activity was tested against airway microbes (Staphylococcus epidermidis, Streptococcus pneumoniae, and pooled human microbiome samples) by placing Lasio/PLGA-coated tubes and appropriate controls in 48 well plates with diluted bacteria. Bacterial inhibition and tube adhesion were tested by measuring optical density and colony formation after tube culture, respectively. Biocompatibility was tested against laryngotracheal fibroblasts and lung epithelial cells.

RESULTS

We achieved a homogeneous coating of ET tubes with Lasio in a PLGA matrix that yields a prolonged, linear release over 1 week (typical timeframe before the ET tube is changed). We observed significant antibacterial activity against S. epidermidis, S. pneumoniae, and human microbiome samples, and prevention of bacterial adherence to the tube. Additionally, the released Lasio did not cause any cytotoxicity toward laryngotracheal fibroblasts or lung epithelial cells in vitro.

CONCLUSION

Overall, we demonstrate the design of an effective-eluting ET tube to modulate upper-airway bacterial infections during intubation which could be deployed to help prevent SGS.

LEVEL OF EVIDENCE

N/A Laryngoscope, 2021.

Antigen-Presenting Cells in the Airways: Moderating Asymptomatic Bacterial Carriage

Bacterial respiratory tract infections (RTIs) are a major global health burden, and the role of antigen-presenting cells (APCs) in mounting an immune response to contain and clear invading pathogens is well-described. However, most encounters between a host and a bacterial pathogen do not result in symptomatic infection, but in asymptomatic carriage instead. The fact that a pathogen will cause infection in one individual, but not in another does not appear to be directly related to bacterial density, but rather depend on qualitative differences in the host response. Understanding the interactions between respiratory pathogens and airway APCs that result in asymptomatic carriage, will provide better insight into the factors that can skew this interaction towards infection. This review will discuss the currently available knowledge on airway APCs in the context of asymptomatic bacterial carriage along the entire respiratory tract. Furthermore, in order to interpret past and futures studies into this topic, we propose a standardized nomenclature of the different stages of carriage and infection, based on the pathogen’s position with regard to the epithelium and the amount of inflammation present.

Selective Nutrient Transport in Bacteria: Multicomponent Transporter Systems Reign Supreme

Multicomponent transporters are used by bacteria to transport a wide range of nutrients. These systems use a substrate-binding protein to bind the nutrient with high affinity and then deliver it to a membrane-bound transporter for uptake. Nutrient uptake pathways are linked to the colonisation potential and pathogenicity of bacteria in humans and may be candidates for antimicrobial targeting. Here we review current research into bacterial multicomponent transport systems, with an emphasis on the interaction at the membrane, as well as new perspectives on the role of lipids and higher oligomers in these complex systems.

Use of Pulsed-Field Gel Electrophoresis to Determine the Source of Methicillin-Resistant Staphylococcus aureus Bacteremia

Pulsed-field gel electrophoresis (PFGE) has historically been considered the gold standard in fingerprinting bacterial strains in epidemiological studies and outbreak investigations; little is known regarding its use in individual clinical cases. The current study detailed two clinical cases in which PFGE helped to determine the source of their methicillin-resistant Staphylococcus aureus (MRSA) bacteremia. Patient A was found to have MRSA bacteremia after trauma in her pelvic area. MRSA was also found in her groin but not in her nostril and rectum. PFGE was performed that showed variable bands of her MRSA isolates from blood and groin, suggestive of different strains of MRSA. Her MRSA bacteremia was determined to be unrelated to her pelvic trauma. Patient B was found to have MRSA bacteremia after colonoscopy. MRSA was also found in his nostril and rectum. PFGE was performed that showed variable bands of his MRSA isolates from blood and rectum but identical bands of MRSA isolates from his blood and nostril. His MRSA bacteremia was determined to be unrelated to his colonoscopy procedure. The current study demonstrates the use of PFGE to rule out the source of bacteremia in individual clinical cases.

Impact of Probiotic Bacteria on Respiratory Allergy Disorders

Respiratory allergy is a common disease with an increased prevalence worldwide. The effective remedy is still unknown, and a new therapeutic approach is highly desirable. The review elaborates the influence of probiotic bacteria on respiratory allergy prevention and treatment with particular emphasis on the impact of the current methods of their administration – oral and intranasal. The background of the respiratory allergy is complex thus, we focused on the usefulness of probiotics in the alleviation of different allergy factors, in particular involved in pathomechanism, local hypersensitive evidence and the importance of epithelial barrier. In this review, we have shown that (1) probiotic strains may vary in modulatory potential in respiratory allergy, (2) probiotic bacteria are beneficial in oral and intranasal administration, (3) recombinant probiotic bacteria can modulate the course of respiratory allergy.

Evaluating Functional Immunity Following Encapsulated Bacterial Infection and Vaccination

Encapsulated bacteria such as Streptococcus pneumoniae, Haemophilus influenzae type b and Neisseria meningitidis cause significant morbidity and mortality in young children despite the availability of vaccines. Highly specific antibodies are the primary mechanism of protection against invasive disease. Robust and standardised assays that measure functional antibodies are also necessary for vaccine evaluation and allow for the accurate comparison of data between clinical studies. This mini review describes the current state of functional antibody assays and their importance in measuring protective immunity.

Mucus, Microbiomes and Pulmonary Disease

The respiratory tract harbors a stable and diverse microbial population within an extracellular mucus layer. Mucus provides a formidable defense against infection and maintaining healthy mucus is essential to normal pulmonary physiology, promoting immune tolerance and facilitating a healthy, commensal lung microbiome that can be altered in association with chronic respiratory disease. How one maintains a specialized (healthy) microbiome that resists significant fluctuation remains unknown, although smoking, diet, antimicrobial therapy, and infection have all been observed to influence microbial lung homeostasis. In this review, we outline the specific role of polymerizing mucin, a key functional component of the mucus layer that changes during pulmonary disease. We discuss strategies by which mucin feed and spatial orientation directly influence microbial behavior and highlight how a compromised mucus layer gives rise to inflammation and microbial dysbiosis. This emerging field of respiratory research provides fresh opportunities to examine mucus, and its function as predictors of infection risk or disease progression and severity across a range of chronic pulmonary disease states and consider new perspectives in the development of mucolytic treatments.

Prevalence of pathogens harbouring mobile antimicrobial resistance genes and virulence factors in retail beef and mutton

Food safety is always a global issue, due to the increased dissemination of antimicrobial resistance and food poisoning related to foodborne bacterial pathogens. The purpose of this study was to assess the risk of potential foodborne bacteria of beef and mutton in retail stores. A total of 134 samples were collected from 24 local markets in Beijing, including raw and cooked beef or mutton, as well as samples derived from the corresponding environment and human beings. We obtained 674 isolates, of which Klebsiella spp. and Staphylococcus spp. were the dominant bacterial species in the meat samples and the environmental samples, respectively. Additionally, environmental bacteria are common in samples from different sources. Based on the results of antimicrobial sensitivity testing, resistance to tetracycline (with a resistance rate of 47.40%), amoxicillin + clavulanate (47.13%) and erythromycin (28.03%) were the major resistant phenotypes. According to the whole genome analysis, the extended spectrum beta-lactamase genes harboured by two K. pneumoniae strains isolated from cooked and raw beef were located on mobile elements. The major toxin genes of Bacillus cereus and adhesion- or invasion-related virulence factors were also shared among isolates from different sources. These factors pose potential risks to public health and need attention.

Association of nasopharyngeal viruses and pathogenic bacteria in children and their parents with and without HIV

BACKGROUND

Bacteria and respiratory viruses co-occur in the nasopharynx, and their interactions may impact pathogenesis of invasive disease. Associations of viruses and bacteria in the nasopharynx may be affected by HIV.

METHODS

We conducted a nested case-control study from a larger cohort study of banked nasopharyngeal swabs from families with and without HIV in West Bengal India, to look at the association of viruses and bacteria in the nasopharynx of parents and children when they are asymptomatic. Quantitative polymerase chain reaction for 4 bacteria and 21 respiratory viruses was run on 92 random nasopharyngeal swabs from children--49 from children living with HIV (CLH) and 43 from HIV uninfected children (HUC)-- and 77 swabs from their parents (44 parents of CLH and 33 parents of HUC).

RESULTS

Bacteria was found in 67% of children, viruses in 45%, and both in 27% of child samples. Staphylococcus aureus (53%) was the most common bacteria, followed by Streptococcus pneumoniae (pneumococcus) (37%) in children and parents (53, 20%). Regardless of HIV status, viruses were detected in higher numbers (44%) in children than their parents (30%) (p = 0.049), particularly rhinovirus (p = 0.02). Human rhinovirus was the most frequently found virus in both CLH and HUC. Children with adenovirus were at six times increased risk of also having pneumococcus (Odds ratio OR 6, 95% CI 1.12-31.9) regardless of HIV status. In addition, the presence of rhinovirus in children was associated with increased pneumococcal density (Regression coeff 4.5, 1.14-7.9). In CLH the presence of rhinovirus increased the risk of pneumococcal colonization by nearly sixteen times (OR 15.6, 1.66-146.4), and, pneumococcus and S. aureus dual colonization by nearly nine times (OR 8.7).

CONCLUSIONS

Children more frequently carried viruses regardless of HIV status. In CLH the presence of rhinovirus, the most frequently detected virus, significantly increased co-colonization with pneumococcus and S. aureus.

The Role of Lung Colonization in Connective Tissue Disease-Associated Interstitial Lung Disease

Connective tissue diseases (CTDs) may frequently manifest with interstitial lung disease (ILD), which may severely impair quality and expectation of life. CTD-ILD generally has a chronic clinical course, with possible acute exacerbations. Although several lines of evidence indicate a relevant role of infections in the acute exacerbations of CTD-ILD, little information is available regarding the prevalence of infections in chronic CTD-ILD and their possible role in the clinical course. The aim of the present retrospective study was the identification of lung microbial colonization in broncho-alveolar lavage from patients affected by stable CTD-ILD with radiologically defined lung involvement. We demonstrated that 22.7% of patients with CTD-ILD display microbial colonization by Pseudomonas aeruginosa, Haemophilus influenzae, and non-tuberculous mycobacteria. Moreover, these patients display a major radiologic lung involvement, with higher impairment in lung function tests confirmed in a multivariate logistic regression analysis. Overall, the present study provides new information on lung colonization during CTD-ILD and its possible relationship with lung disease progression and severity.

Pneumonia

Pneumonia is a common acute respiratory infection that affects the alveoli and distal airways; it is a major health problem and associated with high morbidity and short-term and long-term mortality in all age groups worldwide. Pneumonia is broadly divided into community-acquired pneumonia or hospital-acquired pneumonia. A large variety of microorganisms can cause pneumonia, including bacteria, respiratory viruses and fungi, and there are great geographical variations in their prevalence. Pneumonia occurs more commonly in susceptible individuals, including children of <5 years of age and older adults with prior chronic conditions. Development of the disease largely depends on the host immune response, with pathogen characteristics having a less prominent role. Individuals with pneumonia often present with respiratory and systemic symptoms, and diagnosis is based on both clinical presentation and radiological findings. It is crucial to identify the causative pathogens, as delayed and inadequate antimicrobial therapy can lead to poor outcomes. New antibiotic and non-antibiotic therapies, in addition to rapid and accurate diagnostic tests that can detect pathogens and antibiotic resistance will improve the management of pneumonia.

Type I IFNs facilitate innate immune control of the opportunistic bacteria Burkholderia cenocepacia in the macrophage cytosol

The mammalian immune system is constantly challenged by signals from both pathogenic and non-pathogenic microbes. Many of these non-pathogenic microbes have pathogenic potential if the immune system is compromised. The importance of type I interferons (IFNs) in orchestrating innate immune responses to pathogenic microbes has become clear in recent years. However, the control of opportunistic pathogens-and especially intracellular bacteria-by type I IFNs remains less appreciated. In this study, we use the opportunistic, Gram-negative bacterial pathogen Burkholderia cenocepacia (Bc) to show that type I IFNs are capable of limiting bacterial replication in macrophages, preventing illness in immunocompetent mice. Sustained type I IFN signaling through cytosolic receptors allows for increased expression of autophagy and linear ubiquitination mediators, which slows bacterial replication. Transcriptomic analyses and in vivo studies also show that LPS stimulation does not replicate the conditions of intracellular Gram-negative bacterial infection as it pertains to type I IFN stimulation or signaling. This study highlights the importance of type I IFNs in protection against opportunistic pathogens through innate immunity, without the need for damaging inflammatory responses.

A multidisciplinary approach to the management of nontuberculous mycobacterial lung disease: a clinical perspective

INTRODUCTION

Management of nontuberculous mycobacterial lung disease (NTM-LD) can be encumbered by difficult diagnostic criteria and complex treatment decisions. As prevalence of this debilitating, often refractory, progressive lung disease increases globally, management must evolve beyond antimicrobials to encompass holistic and customized treatments coordinated by practitioners across various specialties.

AREAS COVERED

This review aims to complement the recently updated NTM-LD treatment guidelines and expand current approaches to diagnosis, treatment, and disease management in a multidisciplinary dimension. The foundation of effective long-term management of NTM-LD is awareness of diagnostic criteria, individual patient risk factors, and the importance of managing underlying pulmonary and nonpulmonary comorbidities. The value of adopting all available pharmacological and nonpharmacological treatment modalities with a patient-centered approach to address the needs of long-term patient care cannot be minimized.

EXPERT OPINION

This section, while acknowledging the limited advances in understanding of NTM-LD and the availability of newer diagnostic and therapeutic tools over the last decade, underscores the need for a programmatic approach to this chronic, debilitating pulmonary infection. This will not only lead to more comprehensive patient care with better outcomes, but will also inspire and activate robust networks of research and public health initiatives in this field.

Pneumococcal Conjugate Vaccine Impact on Serotype 3: A Review of Surveillance Data

Introduction

Limited changes in serotype 3 invasive pneumococcal disease (IPD) incidence rates after a decade of 13-valent pneumococcal conjugate vaccine (PCV13) introduction into several national immunization programs (NIP) have raised questions about PCV13's effectiveness against this serotype.

Methods

We analyzed the impact of pediatric PCV programs on serotype 3 IPD with two approaches. First, we reviewed the publicly available surveillance data from countries identified in two recently published reviews to describe the population impact of pediatric PCV13 or PCV10 vaccination programs on serotype 3 IPD. We then compared the observed trends in PCV10 and PCV13 countries to a previously described dynamic transmission model that simulates the spread of pneumococcal carriage and development of IPD in a population over time.

Results

When serotype 3 disease rates are compared from countries that have introduced either a 10-valent (PCV10) vaccine that does not contain serotype 3 in its formulation or PCV13 in their pediatric NIP, over time, serotype 3 incidence rate trends are markedly different. Countries with a PCV10 NIP showed a substantial linear increase in serotype 3 pneumococcal disease among all age groups since the time of PCV10 introduction, whereas countries with a PCV13 NIP experienced a modest decline during the 3–4 years after vaccine introduction followed by an inflection upward in subsequent years.

Conclusion

These data suggest that PCV13 provides a certain degree of direct and indirect protection against serotype 3 at the population level and direct adult vaccination with a serotype 3-containing vaccine is likely to provide substantial benefit in the context of a pediatric PCV NIP. Further research around serotype 3 transmission patterns and epidemiology is nonetheless warranted.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40121-021-00406-w.

Protective response against Acinetobacter baumannii with ferric iron receptors HemTR-BauA in a murine sepsis model

Aim: Iron uptake and metabolism pathways are promising targets in vaccine development as an alternative strategy for antibiotics. Methods & methods: HemTR, a putative heme receptor of Acinetobacter baumannii, was expressed and its protectivity against A. baumannii was determined singly or in combination with the siderophore receptor, BauA, in mice. Results: High level of IgG was elicited. There was a delay in mice mortality with reduced bacterial loads in internal organs in the sublethal challenge. Protection was better in the HemTR-BauA group in both lethal and sublethal challenges. Passive transfer of anti-HemTR and anti-BauA partially protected mice against A. baumannii infection. Conclusion: HemTR in combination with other iron receptors could contribute to the development of protective vaccines against A. baumannii.

Comparative Analysis of Mucociliary Clearance and Mucosal Morphology Using High-Speed Videomicroscopy in Children With Acute and Chronic Rhinosinusitis

OBJECTIVE

evaluation of mucociliary clearance and mucosal morphology using high-speed videomicroscopy, and their association with markers of disease severity in children with acute (ARS) and chronic rhinosinusitis (CRS).

METHODS

A total of 67 children aged from 6 to 17 years including 15 healthy children, 20 pediatric patients with acute rhinosinusitis, and 32 cases with chronic rhinosinusitis were enrolled in the present study. SNOT20, Lund-Kennedy, and Lund-Mackay scores were also evaluated.

RESULTS

Children with rhinosinusitis were characterized by significantly lower number of cells with motile cilia, ciliary beat frequency, cilia length, and cell viability, as well as ciliary beat asynchrony, epithelia dystrophy and reduced epithelial cell height, being more severe in ARS group. Neutrophil infiltration of sinonasal mucosa was more profound in children with ARS, whereas the number of lymphocytes was significantly reduced. Markers of ciliary function were characterized by a significant correlation with epithelia dystrophia and neutrophil infiltration. Discriminant analysis demonstrated significant group separation based on the parameters of mucociliary clearance and mucosal morphology. In regression models mucociliary function was also associated with SNOT20, Lund-Kennedy, and Lund-Mackay scores.

CONCLUSION

The results of the present study demonstrate significant alteration of mucociliary clearance and mucosal morphology and its association with sinonasal inflammation and disease severity in patients with rhinosinusitis. Given a tight association between altered mucociliary clearance and severity of the disease, modulation of inflammation and ciliary function both in acute and chronic rhinosinusitis may be considered as the potential tool in therapeutic and surgical management of the disease.

Experimental Human Challenge Defines Distinct Pneumococcal Kinetic Profiles and Mucosal Responses between Colonized and Non-Colonized Adults

Colonization of the upper respiratory tract with Streptococcus pneumoniae is the precursor of pneumococcal pneumonia and invasive disease. Following exposure, however, it is unclear which human immune mechanisms determine whether a pathogen will colonize. We used a human challenge model to investigate host-pathogen interactions in the first hours and days following intranasal exposure to Streptococcus pneumoniae Using a novel home sampling method, we measured early immune responses and bacterial density dynamics in the nose and saliva after volunteers were experimentally exposed to pneumococcus. Here, we show that nasal colonization can take up to 24 h to become established. Also, the following two distinct bacterial clearance profiles were associated with protection: nasal clearers with immediate clearance of bacteria in the nose by the activity of pre-existent mucosal neutrophils and saliva clearers with detectable pneumococcus in saliva at 1 h post challenge and delayed clearance mediated by an inflammatory response and increased neutrophil activity 24 h post bacterial encounter. This study describes, for the first time, how colonization with a bacterium is established in humans, signifying that the correlates of protection against pneumococcal colonization, which can be used to inform design and testing of novel vaccine candidates, could be valid for subsets of protected individuals.IMPORTANCE Occurrence of lower respiratory tract infections requires prior colonization of the upper respiratory tract with a pathogen. Most bacterial infection and colonization studies have been performed in murine and in vitro models due to the current invasive sampling methodology of the upper respiratory tract, both of which poorly reflect the complexity of host-pathogen interactions in the human nose. Self-collecting saliva and nasal lining fluid at home is a fast, low-cost, noninvasive, high-frequency sampling platform for continuous monitoring of bacterial encounter at defined time points relative to exposure. Our study demonstrates for the first time that, in humans, there are distinct profiles of pneumococcal colonization kinetics, distinguished by speed of appearance in saliva, local phagocytic function, and acute mucosal inflammatory responses, which may either recruit or activate neutrophils. These data are important for the design and testing of novel vaccine candidates.

Introduction of Enzyme-Responsivity in Biomaterials to Achieve Dynamic Reciprocity in Cell-Material Interactions

Much effort has been made in the development of biomaterials that synthetically mimic the dynamics of the natural extracellular matrix in tissues. Most of these biomaterials specifically interact with cells, but lack the ability to adapt and truly communicate with the cellular environment. Communication between biomaterials and cells is achieved by the development of various materials with enzyme-responsive moieties in order to respond to cellular cues. In this perspective, we discuss different enzyme-responsive systems, from surfaces to supramolecular assemblies. Additionally, we highlight their further prospects in order to create, inspired by nature, fully autonomous adaptive biomaterials that display dynamic reciprocal behavior. This Perspective shows new strategies for the development of biomaterials that may find broad utility in regenerative medicine applications, from scaffolds for tissue engineering to systems for controlled drug delivery.

Organization of peptidoglycan synthesis in nodes and separate rings at different stages of cell division of Streptococcus pneumoniae

Bacterial peptidoglycan (PG) synthesis requires strict spatiotemporal organization to reproduce specific cell shapes. In ovoid-shaped Streptococcus pneumoniae (Spn), septal and peripheral (elongation) PG synthesis occur simultaneously at midcell. To uncover the organization of proteins and activities that carry out these two modes of PG synthesis, we examined Spn cells vertically oriented onto their poles to image the division plane at the high lateral resolution of 3D-SIM (structured-illumination microscopy). Labeling with fluorescent D-amino acids (FDAA) showed that areas of new transpeptidase (TP) activity catalyzed by penicillin-binding proteins (PBPs) separate into a pair of concentric rings early in division, representing peripheral PG (pPG) synthesis (outer ring) and the leading-edge (inner ring) of septal PG (sPG) synthesis. Fluorescently tagged PBP2x or FtsZ locate primarily to the inner FDAA-marked ring, whereas PBP2b and FtsX remain in the outer ring, suggesting roles in sPG or pPG synthesis, respectively. Pulses of FDAA labeling revealed an arrangement of separate regularly spaced "nodes" of TP activity around the division site of predivisional cells. Tagged PBP2x, PBP2b, and FtsX proteins also exhibited nodal patterns with spacing comparable to that of FDAA labeling. Together, these results reveal new aspects of spatially ordered PG synthesis in ovococcal bacteria during cell division.

Nasal Tissue Extraction Is Essential for Characterization of the Murine Upper Respiratory Tract Microbiota

The nasal microbiota is composed of species that play a role in the colonization success of pathogens, including Streptococcus pneumoniae and Staphylococcus aureus. Murine models provide the ability to explore disease pathogenesis, but little is known about the natural murine nasal microbiota.

Respiratory infections are a leading cause of morbidity and mortality worldwide. Bacterial pathogens often colonize the upper respiratory tract (nose or mouth) prior to causing lower respiratory infections or invasive disease. Interactions within the upper respiratory tract between colonizing bacteria and the resident microbiota could contribute to colonization success and subsequent transmission. Human carriage studies have identified associations between pathogens such as Streptococcus pneumoniae and members of the resident microbiota, although few mechanisms of competition and cooperation have been identified and would be aided by the use of animal models. Little is known about the composition of the murine nasal microbiota; thus, we set out to improve assessment, including tissue sampling, composition, and comparison between mouse sources. Nasal washes were efficient in sampling the nasopharyngeal space but barely disrupted the nasal turbinates. Nasal tissue extraction increased the yield of cultivable bacterial compared to nasal washes, revealing distinct community compositions. Experimental pneumococcal colonization led to dominance by the colonizing pathogen in the nasopharynx and nasal turbinates, but the composition of the microbiota, and interactions with resident microbes, differed depending on the sampling method. Importantly, vendor source has a large impact on microbial composition. Bacterial interactions, including cooperation and colonization resistance, depend on the biogeography of the nose and should be considered during research design of experimental colonization with pathogens.

IMPORTANCE The nasal microbiota is composed of species that play a role in the colonization success of pathogens, including Streptococcus pneumoniae and Staphylococcus aureus. Murine models provide the ability to explore disease pathogenesis, but little is known about the natural murine nasal microbiota. This study established techniques to allow the exploration of the bacterial members of the nasal microbiota. The mouse nasal microbiota included traditional respiratory bacteria, including Streptococcus, Staphylococcus, and Moraxella species. Analyses were affected by different sampling methods as well as the commercial source of the mice, which should be included in future research design of infectious disease research.

Reduction of free polysaccharide contamination in the production of a 15-valent pneumococcal conjugate vaccine

Glycoconjugate vaccines are vaccines in which a bacterial polysaccharide antigen is conjugated to a carrier protein to enhance immunogenicity by promoting T cell-dependent immune response. However, the free (unreacted) polysaccharides remaining after the conjugation process can inhibit the immunogenicity of a conjugate vaccine. Thus, we aimed to reduce the unbound free polysaccharides in the polysaccharide-protein conjugation process for the development of a new 15-valent pneumococcal conjugate vaccine (PCV15) by varying some factors that may affect the conjugation results such as polysaccharide/protein ratio, polysaccharide size, and concentration of a coupling agent in a conjugation reaction mixture. Concentrations of a coupling agent, carbodiimide (EDAC), and a carrier protein (CRM197) used in PCV15 production, during the conjugation process, had little effect on the content of free polysaccharides. However, the size of the polysaccharide was identified as the critical factor to control the free polysaccharide content, with an inverse relationship observed between the molecular weight of the polysaccharide and the residual free polysaccharide content after conjugation. Based on these results, a new PCV15 with low free polysaccharide contamination was produced and tested for immunogenicity using a rabbit model to show that it induces similar level of immune responses in rabbits compared to a comparator vaccine Prevnar13®.

Genomic insights of international clones of Haemophilus influenzae causing invasive infections in vaccinated and unvaccinated infants

The emergence of invasive Haemophilus influenzae infections in vaccinated patient is a public health concern. We have investigated the genomic basis of invasiveness and possible vaccine failure in H. influenzae causing invasive disease in vaccinated and unvaccinated children in Brazil. Three H. influenzae strains isolated from blood cultures of pediatric patients were sequenced. Serotype, MLST, resistome and virulome were predicted using bioinformatic tools, whereas single nucleotide polymorphisms (SNPs) analysis of cap loci and the presence of the putative virulence-enhancing IS1016-bexA partial deletion were predicted in silico. Infections were caused by H. influenzae type a (Hia), type b (Hib) and nontypeable (NTHi), belonging to international high-risk clones of sequence types ST23, ST6 and ST368, respectively, which have been identified in North American, European and Asian countries. Convergence of ampicillin resistance and virulence in Hib-ST6 was supported by bla_TEM-1B and deletion in the bexA gene, whereas presence of SNPs in the cap-b locus was associated with antigenic modifications of the capsule structure. Hia-ST23 and NTHi-ST368 strains carried galU, lpsA, opsX, rfaF, iga1, lgtC and lic1/lic2 virulence genes, associated with colonization, adaptation and damage to the lung, or invasiveness. In summary, deletion in the bexA gene and presence of SNPs in the cap locus of Hib could be contributing to invasive disease and possible vaccine failure in pediatric patients, whereas serotype replacement of Hib with type "a" and NTHi strains denotes the ability of non-vaccine serotypes to re-colonize vaccinated patients. Finally, the dissemination of international high-risk clones of H. influenzae emphasizes the importance of monitoring changes in the molecular epidemiology of invasive H. influenzae disease.

Stenotrophomonas maltophilia outer membrane protein A induces epithelial cell apoptosis via mitochondrial pathways

Stenotrophomonas maltophilia (S. maltophilia) is a common opportunistic pathogen in intensive care units and causes infections most often after surgeries in immune-compromised patients such as those undergoing chemotherapy. Outer membrane protein A (OmpA) is the most abundant of the outer membrane proteins in S. maltophilia. Previous studies on OmpA usually focus on its interaction with the host cells and its role in vaccine development. However, the impact of OmpA on the virulence of S. maltophilia to host cells and the effects on apoptosis remain unclear. In this study, we exposed purified recombinant S. maltophilia OmpA (rOmpA) to HEp-2 cells and investigated the effects of OmpA on epithelial cell apoptosis. Morphologic and flow cytometric analyses revealed that HEp-2 cells stimulated with rOmpA multiple apoptosis features, including nuclear roundness and pyknosis, chromatin aggregation, and phosphatidylserine eversion. We found that rOmpA regulated the protein levels of Bax and Bcl-xL in HEp-2 cells, leading to changes in mitochondria permeability and the release of cytochrome c and apoptosis-inducing factors into the cytoplasm. These subsequently activate the caspase-9/caspase-3 pathway that promote apoptosis. We also observed that rOmpA enhanced the generation of reactive oxygen species and increased intracellular Ca²⁺ levels in HEp-2 cells. Collectively, our data suggested that rOmpA induced epithelial cells apoptosis via mi-tochondrial pathways.

The UhpA mutant of Edwardsiella piscicida enhanced its motility and the colonization in the intestine of tilapia

Edwardsiella piscicida (E. piscicida) is a significant bacterial pathogen of cultured fish, which infected fish meanly through the intestine. Glucose 6-phosphate (Glu6P) in the intestine is nutritious to the pathogen, Meanwhile, Glu6P was found using as a virulent regulating signal for bacteria. The UhpA, one of the Glu6P transport system regulatory proteins could down-regulate the uhpC/uhpB/uhpA system and decrease its pathogenicity. However, the motility and the colonization of E. piscicida affected by UhpA were still unclear. In this study, the motility and the colonization of E. piscicida were monitored. The result demonstrated that the motility of EIB202 was significantly stronger than that of in ΔuhpA according to fractions 4, 8 and 9. However, the motility of ΔuhpA was significantly stronger than that of EIB202 according to the total number at the whole experiment. Although, there was no difference in the number of bacteria in the posterior intestine of tilapia after infected with E. piscicida EIB202 and ΔuhpA. The number of bacteria in the anterior and the middle intestine of fish infected with ΔuhpA were significantly higher than that of in fish infected with EIB202 at the whole experiment (P < 0.05). Interestingly, both E. piscicida strains colonized in the anterior intestine than that of in the middle and posterior intestines of tilapia. Besides, the gene expression of IL-1β and TNF-α in the head-kidney of fish infected with ΔuhpA showed significantly higher (p < 0.05) than fish infected with EIB202 during the whole experimental period. Most importantly, the survival rate of E. piscicida EIB202 and ΔuhpA were 57% and 37% respectively. All results indicate that the uhpA gene mutant in E. piscicida could enhance its motility and the colonization in the intestine of tilapia, this illustrates the mechanism of UhpA decreases the pathogenesis of E. piscicida in fish.

Impact of pneumococcal conjugate vaccine on the carriage density of Streptococcus pneumoniae and Staphylococcus aureus in children living with HIV: a nested case-control study

Nasopharyngeal colonization density of Streptococcus pneumoniae (pneumococcus) is associated with disease severity and transmission. Little is known about the density of pneumococcal carriage in children with HIV (CLH). Pneumococcal vaccines may impact the density of pneumococcus and competing microbes within the nasopharynx. We examined the impact of one dose of PCV13 on carriage density of pneumococcus and Staphylococcus aureus, in CLH, HIV-uninfected children (HUC), and their unvaccinated parents. We conducted a pilot-nested case-control study, within a larger prospective cohort study, on the impact of PCV13, in families in West Bengal India. Quantitative real-time PCR was run on 147 nasopharyngeal swabs from 27 CLH and 23 HUC, and their parents, before and after PCV13 immunization. CLH had higher median pneumococcal carriage density, compared to HUC: 6.28 × 108 copies/mL vs. 2.11 × 105 copies/mL (p = .005). Following one dose of PCV13, pneumococcal densities dropped in both groups, with an increase in S. aureus carriage to 80% from 48% in CLH, and to 60% in HUC from 25%. While limited in sample size, this pilot study shows that CLH carried higher densities of pneumococcus. PCV13 was associated with a decrease in pneumococcal density and a temporal increase in S. aureus carriage regardless of HIV status.

Citrullination of extracellular histone H3.1 reduces antibacterial activity and exacerbates its proteolytic degradation

BACKGROUND

Cystic fibrosis (CF), involves excessive airway accumulation of neutrophils, often in parallel with severe infection caused by Pseudomonas aeruginosa. Free histones are known to possess bactericidal properties, but the degree of antibacterial activity exerted on specific lung-based pathogens is largely unknown. Neutrophils have a high content of peptidyl deiminase 4 (PADI4), which citrullinate cationic peptidyl-arginines. In histone H3.1, several positions in the NH₂-terminal tail are subject to citrullination.

METHODS

Full-length and segmented histone subunit H3.1 was investigated for bactericidal activity towards P. aeruginosa (strain PAO1). PADI4-induced citrullination of histone H3.1 was assessed for antibacterial activity towards P. aeruginosa. Next, the effect of neutrophil elastase (NE)-mediated proteolysis of histone H3.1 was investigated. Finally, PADI4, H3.1, and citrullinated H3.1 were examined in healthy control and CF patient lung tissues.

RESULTS

Full-length histone H3.1 and sections of the histone H3.1 tail, displayed bactericidal activity towards P. aeruginosa. These antibacterial effects were reduced following citrullination by PADI4 or proteolysis by NE. Interestingly, citrullination of histone H3.1 exacerbated NE-mediated degradation. In CF lung tissue, citrullinated histone H3.1 and PADI4 immunoreactivity was abundant. Degraded histone H3.1 was detected in the sputum of CF patients but was absent in the sputum of healthy controls.

CONCLUSIONS

Citrullination impairs the antibacterial activity of histone H3.1 and exacerbates its proteolytic degradation by NE. Citrullination is likely to play an important role during resolution of acute inflammation. However, in chronic inflammation akin to CF, citrullination may dampen host defense and promote pathogen survival, as exemplified by P. aeruginosa.

Viral-bacterial (co-)occurrence in the upper airways and the risk of childhood pneumonia in resource-limited settings

OBJECTIVE

To examine the association between bacterial-viral co-occurrence in the nasopharynx and the risk of community acquired pneumonia (CAP) in young children living in resource-limited settings.

METHODS

A case-control study was conducted between January and December 2017 in Moshi, Tanzania. Children 2-59 months with CAP and healthy controls were enrolled. RSV and Influenza A/B were detected with a standardized polymerase chain reaction (PCR) method, and a simplified real-time quantitative PCR method, without sample pre-processing, was developed to detect bacterial pathogens in nasopharyngeal samples.

RESULTS

A total of 109 CAP patients and 324 healthy controls were enrolled. Co-detection of H. influenzae and S. pneumoniae in nasopharyngeal swabs was linked with higher odds of CAP (aOR=3.2, 95% CI=1.1-9.5). The majority of the H. influenzae isolated in cases and controls (95.8%) were non-typeable. Of the viruses examined, respiratory syncytial virus (RSV) was most common (n = 31, 7.2%) in cases and controls. Children with RSV had 8.4 times higher odds to develop pneumonia than healthy children (aOR=8.4, 95%CI= 3.2 - 22.1).

CONCLUSIONS

Co-occurence of H. influenzae and S. pneumoniae in the nasopharynx was strongly associated with CAP. The high prevalence of non-typeable H. influenzae might be a sign of replacement as a consequence of Haemophilus influenzae type b vaccination.

Associations of barn air quality parameters with ultrasonographic lung lesions, airway inflammation and infection in group-housed calves

Barn climate is believed to play a major role in the bovine respiratory disease complex. However, the exact air quality parameters associated with (sub)clinical pneumonia or airway inflammation in calves are currently unknown. The objective of this cross-sectional study was to assess associations of air quality parameters with clinical signs, lung consolidation, pulmonary inflammation and infection in group-housed calves. In total, 60 beef and dairy farms were visited from January to April 2017 and 428 calves sampled. Measured air quality parameters included continuous 24-h measurements of ammonia concentration, relative humidity and temperature and punctual measurements of air velocity, ammonia, CO₂ and bacterial air load. Calf sampling consisted of clinical examination, thoracic ultrasonography and broncho-alveolar lavage sampling for bacteriological and cytological analysis of broncho-alveolar lavage fluid (BALf). Average air temperature was 14.2 °C (standard deviation (SD) 4.4, range 5.5-23.9) and relative humidity 68.8 % (SD 8.9, range 52.2-91.6). Average ammonia concentration was 1.7 ppm (SD 0.9, range 0-10.0). Lung consolidations of ≥1 cm, ≥3 cm and ≥6 cm in depth were present in 41.1 % (176/428), 27.1 % (116/428) and 16.1 % (69/428) of the calves, respectively. Average pen temperature was positively associated with consolidations of ≥1 cm (P = 0.005), ≥3 cm (P = 0.002) and ≥6 cm (P < 0.01). Ammonia exposure, in hours>4 ppm, was associated with lung consolidation ≥1 cm (odds ratio (OR) = 1.73; confidence interval (CI) = 1.02-3.07; P = 0.04). Ammonia concentration was positively associated with BALf epithelial cell percentage (P = 0.01). Air velocity >0.8 m/s was associated with increased odds of lung consolidation of ≥3 cm (OR = 6.8; CI = 1.2-38.5; P = 0.04) and ≥6 cm (OR = 15.9; CI = 1.2-200.0; P = 0.03). The prevalence of lung consolidations ≥1 cm was higher in the draught (81.8 %; P = 0.0092) and warm, dry and ammonia accumulation clusters (54.2 %; P = 0.02) compared to the presumably normal cluster (31.6 %). In addition, in the warm, dry and ammonia cluster the prevalence of lung consolidations ≥3 cm (38.1 %; P = 0.04) and ≥6 cm (31.4 %; P = 0.01) in depth were higher compared to the presumably normal climate cluster (18.2 % and 9.1 %, respectively). Of all frequently measured indoor air quality parameters, only average temperature, ammonia concentration and air velocity were associated with pneumonia and might therefore be preferable for cost-effective evaluation of calf barn climate.

Dissecting Streptococcus pyogenes interaction with human

Streptococcus pyogenes is a species of Gram-positive bacteria. It is also known as Group A Streptococcus (GAS) that causes pathogenesis to humans only. The GAS infection has several manifestations including invasive illness. Current research has linked the molecular modes of GAS virulence with substantial sequencing determinations for the isolation of genomes. These advances help to comprehend the molecular evolution resulting in the pandemic strains. Thus, it is indispensable to reconsider the philosophy that involves GAS pathogenesis. The recent investigations involve studying GAS in the nasopharynx and its capability to cause infection or asymptomatically reside in the host. These advances have been discussed in this article with an emphasis on the natural history of GAS and the evolutionary change in the pandemic strains. In addition, this review describes the unique functions for major pathogenicity determinants to comprehend their physiological effects.

Pyruvate secretion by oral streptococci modulates hydrogen peroxide dependent antagonism

Many commensal oral streptococci generate H₂O₂ via pyruvate oxidase (SpxB) to inhibit the growth of competing bacteria like Streptococcus mutans, a major cariogenic species. In Streptococcus sanguinis SK36 (SK36) and Streptococcus gordonii DL1 (DL1), spxB expression and H₂O₂ release are subject to carbon catabolite repression by the catabolite control protein A (CcpA). Surprisingly, ccpA deletion mutants of SK36 and DL1 fail to inhibit S. mutans despite their production of otherwise inhibitory levels of H₂O₂. Using H₂O₂-deficient spxB deletion mutants of SK36 and DL1, it was subsequently discovered that both strains confer protection in trans to other bacteria when H₂O₂ is added exogenously. This protective effect depends on the direct detoxification of H₂O₂ by the release of pyruvate. The pyruvate dependent protective effect is also present in other spxB-encoding streptococci, such as the pneumococcus, but is missing from spxB-negative species like S. mutans. Targeted and transposon-based mutagenesis revealed Nox (putative H₂O-forming NADH dehydrogenase) as an essential component required for pyruvate release and oxidative protection, while other genes such as sodA and dps play minor roles. Furthermore, pyruvate secretion is only detectable in aerobic growth conditions at biofilm-like cell densities and is responsive to CcpA-dependent catabolite control. This ability of spxB-encoding streptococci reveals a new facet of the competitive interactions between oral commensals and pathobionts and provides a mechanistic basis for the variable levels of inhibitory potential observed among H₂O₂-producing strains of commensal oral streptococci.

Non-ventilator health care associated pneumonia (NV-HAP): Oncology

Literature suggests that cancer patients can become colonized or infected with a variety of opportunistic and health care-associated pathogens, putting them at higher risk for nonventilator health care-associated pneumonia. This section will review the epidemiology of nonventilator health care-associated pneumonia and the importance of prevention strategies in this vulnerable population. Prevention strategies for cancer patients across the continuum of care are highlighted.

Mechanisms of Epithelial Immunity Evasion by Respiratory Bacterial Pathogens

Bacterial lung infections are major healthcare challenges killing millions of people worldwide and resulting in a huge economic burden. Both basic and clinical research have elucidated host mechanisms that contribute to the bacterial clearance where an indispensable role of immune cells has been established. However, the role of respiratory epithelial cells in bacterial clearance has garnered limited attention due to their weak inflammatory or phagocytic ability compared to immune cells such as macrophages and neutrophils. These studies often underappreciate the fact that epithelial cells are the most abundant cells in the lung, not only serving as building blocks but also providing immune protection throughout the lung. Epithelial cells function either independently to eradicate the pathogen or communicate with immune cells to orchestrate pathogen clearance. The epithelial cells have multiple mechanisms that include mucus production, antimicrobial peptide production, muco-ciliary clearance, and phagocytosis, all of which contribute to their direct antibacterial function. Secretion of cytokines to recruit immune cells and potentiate their antimicrobial activities is a pathway by which the epithelium contributes to bacterial clearance. Successful pathogens outsmart epithelial resistance and find a way to replicate in sufficient numbers to establish infections in the airway or lung epithelial surfaces. In this mini-review, we discuss evidences that establish important roles for epithelial host defense against invading respiratory bacterial pathogens and demonstrate how pathogens outsmart these epithelial immune mechanisms to successfully establish infection. Finally, we discuss briefly how to boost epithelial immunity to improve outcomes in bacterial lung infections.

Mechanisms of Epithelial Immunity Evasion by Respiratory Bacterial Pathogens

Bacterial lung infections are major healthcare challenges killing millions of people worldwide and resulting in a huge economic burden. Both basic and clinical research have elucidated host mechanisms that contribute to the bacterial clearance where an indispensable role of immune cells has been established. However, the role of respiratory epithelial cells in bacterial clearance has garnered limited attention due to their weak inflammatory or phagocytic ability compared to immune cells such as macrophages and neutrophils. These studies often underappreciate the fact that epithelial cells are the most abundant cells in the lung, not only serving as building blocks but also providing immune protection throughout the lung. Epithelial cells function either independently to eradicate the pathogen or communicate with immune cells to orchestrate pathogen clearance. The epithelial cells have multiple mechanisms that include mucus production, antimicrobial peptide production, muco-ciliary clearance, and phagocytosis, all of which contribute to their direct antibacterial function. Secretion of cytokines to recruit immune cells and potentiate their antimicrobial activities is a pathway by which the epithelium contributes to bacterial clearance. Successful pathogens outsmart epithelial resistance and find a way to replicate in sufficient numbers to establish infections in the airway or lung epithelial surfaces. In this mini-review, we discuss evidences that establish important roles for epithelial host defense against invading respiratory bacterial pathogens and demonstrate how pathogens outsmart these epithelial immune mechanisms to successfully establish infection. Finally, we discuss briefly how to boost epithelial immunity to improve outcomes in bacterial lung infections.

Clinical significance of viral-bacterial codetection among young children with respiratory tract infections: Findings of RSV, influenza, adenoviral infections

We aimed to evaluate the clinical significance of bacterial coexistence and the coinfection dynamics between bacteria and respiratory viruses among young children. We retrospectively analyzed clinical data from children aged < 5 years hospitalized with a community-acquired single respiratory viral infection of influenza, adenovirus, or RSV during 2 recent consecutive influenza seasons. Remnant respiratory specimens were used for bacterial PCR targeting Moraxella catarrhalis, Haemophilus influenzae, Streptococcus pneumoniae, and Staphylococcus aureus.A total of 102 children were included; median age was 0.8 years and 44.1% had underlying comorbidities. Overall, 6.8% (7/102) of cases were classified as severe diseases requiring intensive care unit admission and/or mechanical ventilation and ranged from 8.8% for a patient with RSV and 7.6% for those with adenovirus to 0% for those with influenza viruses. The overall viral-bacterial codetection rate was 59.8% (61/102); M catarrhalis was the most frequent (33.3%), followed by H influenzae (31.4%). Influenza cases showed higher bacterial codetection rates (80.0%; 8/10) compared with those with adenoviruses (69.2%; 9/13) and RSV (55.7%; 44/79). S pneumoniae and H influenzae codetections were associated with reduced severity (aOR, 0.24; 95% CI, 0.07-0.89), and reduced risk of wheezing (aOR, 0.36; 95% CI, 0.13-0.98), respectively.We observed the interactions between respiratory viruses and bacteria and the clinical significance of viral-bacterial coexistence in upper airway on disease severity. Future study will be necessary to elucidate the active interactions between different viruses and bacteria and give clues to risk stratified strategy in the management of respiratory infections among young children.

Differential IL-17A response to S. pneumoniae in adenoid tissue of children with sleep disordered breathing and otitis media with effusion

Streptococcus pneumonia, one of the major colonizers in nasopharyngeal adenoids, has been the predominant pathogen causing acute otitis media (AOM) in children. Recent evidence suggests an association between IL-17A-mediated immune response and the clearance of pneumococcal colonization in nasopharyngeal adenoids. Here, we evaluated the expressions of IL-17A and associated genes in hypertrophic adenoid tissues of children with sleep-disordered breathing (SDB) and otitis media with effusion (OME) and their association with pneumococcal carriage. Sixty-six pediatric patients with adenoid hypertrophy were enrolled. During adenoidectomy, nasopharyngeal swab and adenoid tissues were used to determine pneumococcal carriage and IL-17A expression. Our results revealed significantly higher levels of IL-17A and IL-17A:IL-10 mRNA in the SDB patients positive for nasopharyngeal pneumococcal carriage than those negative. However, these differences were not significant in the OME group. These results suggested, in OME patients, prolonged or chronic pneumococcal carriage may occur because of insufficient IL-17A-mediated mucosal clearance, and could further lead to AOM and OME development.

Gold nanoparticles synthesised by flavonoid tricetin as a potential antibacterial nanomedicine to treat respiratory infections causing opportunistic bacterial pathogens

In this study, flavonoid tricetin was used as a reducing and capping agent for the synthesis of gold nanoparticles (AuNPs). Further, the antibacterial efficacy of the synthesised AuNPs was evaluated against the opportunistic bacterial pathogens that cause respiratory infections. The optimum levels for the synthesis of AuNPs were found to be pH 8, temperature 30 °C, tricetin 125 μM and chloroauric acid 250 μM. The tricetin synthesised AuNPs exhibited in spherical shape with an average size of 12 nm. FT-IR results confirmed that the hydroxyl (OH) and carbonyl (CO) groups of tricetin were mainly participated in the synthesis of AuNPs. The opportunistic bacterial pathogens isolated from immunocompromised patients suffering with different respiratory infections were identified as Staphylococcus aureus, Enterobacter xiangfangensis, Bacillus licheniformis, Escherichia fergusonii, Acinetobacter pittii, Pseudomonas aeruginosa, Aeromonas enteropelogenes and Proteus mirabilis. The antibacterial studies confirmed the broad-spectrum antibacterial activity of AuNPs against the tested Gram-positive and Gram-negative bacteria. The synthesised AuNPs showed high biocompatibility on primary normal human dermal fibroblast (NHDF-c) cells up to 50 μM mL^-1. Best of our knowledge, this is the first report on the synthesis of AuNPs using tricetin, which may be a potential antibacterial nanomedicine to treat bacterial infections.

Bordetella pertussis antigens encapsulated into N-trimethyl chitosan nanoparticulate systems as a novel intranasal pertussis vaccine

The mucosal immune system serves as the first line of defense against Bordetella pertussis. Intranasal vaccination, due to its potential to induce systemic and mucosal immune responses, appears to prevent the initial adherence and colonization of the bacteria at the first point of contact. In the present study, two B. pertussis antigens, pertussis Toxoid (PTd) and Filamentous hemagglutinin (FHA), which play a very significant role in virulence and protection against pertussis, were encapsulate into N-trimethyl chitosan (TMC) nanoparticulate systems. After preparation of TMC nanoparticles (NPs), the NPs were characterized and their ability to induce efficient immune responses against B. pertussis was studied in a mouse model. Our findings showed that PTd + FHA-loaded TMC NPs have strong ability to induce IL-4, IL-17, IFN-γ, IgG, and IgA in the mouse model. Results from this study suggest that nasal administration of the PTd + FHA-loaded TMC NPs induced not only a systemic immune response but also a local mucosal response, which may improve the efficacy of pertussis prevention through respiratory tract transmission.

Molecular analysis of an enigmatic Streptococcus pneumoniae virulence factor: The raffinose-family oligosaccharide utilization system

Streptococcus pneumoniae is an opportunistic respiratory pathogen that can spread to other body sites, including the ears, brain, and blood. The ability of this bacterium to break down, import, and metabolize a wide range of glycans is key to its virulence. Intriguingly, S. pneumoniae can utilize several plant oligosaccharides for growth in vitro, including raffinose-family oligosaccharides (RFOs, which are α-(1→6)-galactosyl extensions of sucrose). An RFO utilization locus has been identified in the pneumococcal genome; however, none of the proteins encoded by this locus have been biochemically characterized. The enigmatic ability of S. pneumoniae to utilize RFOs has recently received attention because mutations in two of the RFO locus genes have been linked to the tissue tropism of clinical pneumococcal isolates. Here, we use functional studies combined with X-ray crystallography to show that although the pneumococcal RFO locus encodes for all the machinery required for uptake and degradation of RFOs, the individual pathway components are biochemically inefficient. We also demonstrate that the initiating enzyme in this pathway, the α-galactosidase Aga (a family 36 glycoside hydrolase), can cleave α-(1→3)-linked galactose units from a linear blood group antigen. We propose that the pneumococcal RFO pathway is an evolutionary relic that is not utilized in this streptococcal species and, as such, is under no selection pressure to maintain binding affinity and/or catalytic efficiency. We speculate that the apparent contribution of RFO utilization to pneumococcal tissue tropism may, in fact, be due to the essential role the ATPase RafK plays in the transport of other carbohydrates.

Translating Recent Microbiome Insights in Otitis Media into Probiotic Strategies

The microbiota of the upper respiratory tract (URT) protects the host from bacterial pathogenic colonization by competing for adherence to epithelial cells and by immune response regulation that includes the activation of antimicrobial and (anti-)inflammatory components. However, environmental or host factors can modify the microbiota to an unstable community that predisposes the host to infection or inflammation. One of the URT diseases most often encountered in children is otitis media (OM). The role of pathogenic bacteria like Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis in the pathogenesis of OM is well documented. Results from next-generation-sequencing (NGS) studies reveal other bacterial taxa involved in OM, such as Turicella and Alloiococcus Such studies can also identify bacterial taxa that are potentially protective against URT infections, whose beneficial action needs to be substantiated in relevant experimental models and clinical trials. Of note, lactic acid bacteria (LAB) are members of the URT microbiota and associated with a URT ecosystem that is deemed healthy, based on NGS and some experimental and clinical studies. These observations have formed the basis of this review, in which we describe the current knowledge of the molecular and clinical potential of LAB in the URT, which is currently underexplored in microbiome and probiotic research.

Pulmonary Colonization Resistance to Pathogens via Noncanonical Wnt and Interleukin-17A by Intranasal pep27 Mutant Immunization

Background

Previous studies have focused on colonization resistance of the gut microbiota against antibiotic resistant strains. However, less research has been performed on respiratory colonization resistance.

Methods

Because respiratory colonization is the first step of respiratory infections, intervention to prevent colonization would represent a new approach for preventive and therapeutic measures. The Th17 response plays an important role in clearance of respiratory pathogens. Thus, harnessing the Th17 immune response in the mucosal site would be an effective method to design a respiratory mucosal vaccine.

Results

In this study, we show that intranasal Δpep27 immunization induces noncanonical Wnt and subsequent interleukin (IL)-17 secretion, and it inhibits Streptococcus pneumoniae, Staphylococcus aureus, and Klebsiella pneumoniae colonization. Moreover, IL-17A neutralization or nuclear factor of activated T-cell inhibition augmented bacterial colonization, indicating that noncanonical Wnt signaling is involved in pulmonary colonization resistance.

Conclusions

Therefore, Δpep27 immunization can provide nonspecific respiratory colonization resistance via noncanonical Wnt signaling and IL-17A-related pathways.

Meningococcal pneumonia: a review

Background

Although Neisseria meningitidis is one of the major causes of meningitis, meningococcal pneumonia is the most common non-neurological organ disease caused by this pathogen.

Methods

We conducted a review of the literature to describe the risk factors, pathogenesis, clinical features, diagnosis, treatment and prevention of meningococcal pneumonia.

Results

Meningococcal pneumonia was first described in 1907 and during the 1918–1919 influenza pandemic large numbers of cases of meningococcal pneumonia occurred in patients following the initial viral infection. A number of publications, mainly case series or case reports, has subsequently appeared in the literature. Meningococcal pneumonia occurs mainly with serogroups Y, W-135 and B. Risk factors for meningococcal pneumonia have not been well characterised, but appear to include older age, smoking, people living in close contact (e.g. military recruits and students at university), preceding viral and bacterial infections, haematological malignancies, chronic respiratory conditions and various other non-communicable and primary and secondary immunodeficiency diseases. Primary meningococcal pneumonia occurs in 5–10% of patients with meningococcal infection and is indistinguishable clinically from pneumonia caused by other common pathogens. Fever, chills and pleuritic chest pain are the most common symptoms, occurring in > 50% of cases. Productive sputum and dyspnoea are less common. Diagnosis of meningococcal pneumonia may be made by the isolation of the organism in sputum, blood, or normally sterile site cultures, but is likely to underestimate the frequency of meningococcal pneumonia. If validated, PCR-based techniques may be of value for diagnosis in the future. While penicillin was the treatment of choice for meningococcal infection, including pneumonia, prior to 1991, a third generation cephalosporin has been more commonly used thereafter, because of concerns of penicillin resistance. Chemoprophylaxis, using one of a number of antibiotics, has been recommended for close contacts of patients with meningococcal meningitis, and similar benefits may be seen in contacts of patients with meningococcal pneumonia. Effective vaccines are available for the prevention of infection with certain meningococcal serogroups, but this field is still evolving.

Conclusion

Meningococcal pneumonia occurs fairly frequently and should be considered as a possible cause of pneumonia, particularly in patients with specific risk factors.

Development of a new 15-valent pneumococcal conjugate vaccine (PCV15) and evaluation of its immunogenicity

A new 15-valent pneumococcal conjugate vaccine (PCV15) against serotypes 1, 3, 4, 5, 6A, 6B, 7F, 9V, 11A, 14, 18C, 19A, 19F, 22F, and 23F has been developed using aluminum phosphate as an adjuvant. Using the rabbit model, immunogenicity of each serotype was evaluated by measuring antigen specific antibodies and functional antibody titers and comparing them to a control vaccine, Prevnar13®. Among the shared serotypes in both PCV15 and Prevnar13®, Type 3 and 23F in PCV15 exhibited a lower opsonic index than Prevnar13®. Conversely, the other types showed greater or nearly the same immunogenic effects. Type 11A and 22F are two additional serotypes included in PCV15, and only 22F showed a reasonable opsonic index compared with other types. Type 11A exhibited a basal level fold-increase in OPA; thus, we further optimized 11A as well as 3 and 23F by controlling the polysaccharide-to-protein conjugation ratio as a variable. Antibody levels and functional antibody activities were evaluated by ELISA and OPA, and improved levels of immunogenic activities were observed for all three serotypes. In this study, we propose a new PCV15 candidate, in which the common 13 serotypes and a licensed control vaccine have equivalent efficacy while two additional serotypes showed adequate immunogenicity in the rabbit model.

Microinvasion by Streptococcus pneumoniae induces epithelial innate immunity during colonisation at the human mucosal surface

Control of Streptococcus pneumoniae colonisation at human mucosal surfaces is critical to reducing the burden of pneumonia and invasive pneumococcal disease, interrupting transmission, and achieving herd protection. Here, we use an experimental human pneumococcal carriage model (EHPC) to show that S. pneumoniae colonisation is associated with epithelial surface adherence, micro-colony formation and invasion, without overt disease. Interactions between different strains and the epithelium shaped the host transcriptomic response in vitro. Using epithelial modules from a human epithelial cell model that recapitulates our in vivo findings, comprising of innate signalling and regulatory pathways, inflammatory mediators, cellular metabolism and stress response genes, we find that inflammation in the EHPC model is most prominent around the time of bacterial clearance. Our results indicate that, rather than being confined to the epithelial surface and the overlying mucus layer, the pneumococcus undergoes micro-invasion of the epithelium that enhances inflammatory and innate immune responses associated with clearance.

Streptococcus pneumoniae is a common coloniser of the human nasopharynx, but it also causes severe diseases. Here, Weight et al. use an experimental human pneumococcal carriage model to show that bacterial colonisation is associated with invasion of the epithelium and enhancement of immune responses.