Pathogenicity and virulence of Streptococcus pneumoniae: Cutting to the chase on proteases

The Metabolic Potential of the Human Lung Microbiome

The human lung microbiome remains largely underexplored, despite its potential implications in the pharmacokinetics of inhaled drugs and its involvement in lung diseases. Interactions within these bacterial communities and with the host are complex processes which often involve microbial small molecules. In this study, we employed a computational approach to describe the metabolic potential of the human lung microbiome. By utilizing antiSMASH and BiG-SCAPE software, we identified 1831 biosynthetic gene clusters for the production of specialized metabolites in a carefully compiled genome database of lung-associated bacteria and fungi. It was shown that RiPPs represent the largest class of natural products within the bacteriome, while NRPs constitute the largest class of natural products in the lung mycobiome. All predicted BGCs were further categorized into 767 gene cluster families, and a subsequent network analysis highlighted that these families are widely distributed and contain many uncharacterized members. Moreover, in-depth annotation allowed the assignment of certain gene clusters to putative lung-specific functions within the microbiome, such as osmoadaptation or surfactant synthesis. This study establishes the lung microbiome as a prolific source for secondary metabolites and lays the groundwork for detailed investigation of this unique environment.

Adjudicative efficacy of Bifidobacterium animalis subsp. lactis BLa80 in treating acute diarrhea in children: a randomized, double-blinded, placebo-controlled study

The goal of this study is to assess the efficacy and safety of Bifidobacterium animalis subsp. lactis BLa80, as an adjunct treatment for diarrhea in children with a randomized, double-blinded, placebo-controlled study design. Eligible diarrheal children, aged 0-3 years without the need for antibiotic treatment based on clinical diagnosis when recruited, were randomized into the intervention group (IG, n = 58, with probiotic) or the control group (CG, n = 53, placebo). The primary assessment was the duration of diarrhea. Fecal samples were collected for biochemical index measurement, analysis of gut microbiome composition, and prediction of gene family abundances. The total duration of diarrhea in the IG (122.6 ± 13.1 h) was significantly shorter than in the CG (148.4 ± 17.6 h, p < 0.001). More children in the IG showed improvements in diarrhea compared to the CG, both in intention-to-treat analysis (81.7% vs. 40.0%, p < 0.001) and per protocol analysis (84.4% vs 45.3%, p < 0.001). Cathelicidin level in the IG was significantly higher than that in the CG after the intervention (4415.00 ± 1036.93 pg/g vs. 3679.49 ± 871.18 pg/g, p = 0.0175). The intervention led to an increased abundance of Bifidobacterium breve and Collinsella aerofaciens species, higher alpha-diversity (p < 0.05), and enrichment of functional genes in the gut microbiota related to immunity regulation. Administration of BLa80 at a dose of 5 × 109 CFU/day resulted in a shorter duration of diarrhea and alterations in gut microbiome composition and gene functions.

Streptococcus taonis sp. nov., a novel bacterial species isolated from a blood culture of a patient

One Gram stain-positive, catalase-negative, α-hemolytic, chain-forming or paired cocci, designated ST22-14T, was isolated from a blood culture of a child with suspected infection. The results of 16S rRNA gene sequences analyses showed that the most closely related species to strain ST22-14T were "Streptococcus vulneris" DM3B3T (99.2%), Streptococcus mitis NCTC 12261T (99.0%), "Streptococcus gwangjuense" ChDC B345T, (99.0%), Streptococcus oralis subsp. dentisani 7747T (99.0%), Streptococcus downii CECT 9732T (99.0%), and Streptococcus infantis ATCC 700779T (98.9%). The genome of strain ST22-14T consists of 2,053,261 bp with a G + C content of 39.4%. Average nucleotide identity values between strain ST22-14T and Streptococcus mitis NCTC 12261T or other five species were from 82.2 to 88.0%. In silico DNA-DNA hybridization of ST22-14T showed an estimated DNA reassociation value of 34.6% with the closest species. The main cellular fatty acids of strain ST22-14T were 16:0, 18:0, 14:0, 18:1ω7c and 18:1ω6c. Based on these results, strain ST22-14T should be classified as a novel species of genus Streptococcus, for which the name Streptococcus taonis sp. nov. is proposed (type strain ST22-14T = NBRC 116002T = BCRC 81402T).

Bacterial Infections in Intensive Care Units: Epidemiological and Microbiological Aspects

Intensive care units constitute a critical setting for the management of infections. The patients' fragilities and spread of multidrug-resistant microorganisms lead to relevant difficulties in the patients' care. Recent epidemiological surveys documented the Gram-negative bacteria supremacy among intensive care unit (ICU) infection aetiologies, accounting for numerous multidrug-resistant isolates. Regarding this specific setting, clinical microbiology support holds a crucial role in the definition of diagnostic algorithms. Eventually, the complete patient evaluation requires integrating local epidemiological knowledge into the best practice and the standardization of antimicrobial stewardship programs. Clinical laboratories usually receive respiratory tract and blood samples from ICU patients, which express a significant predisposition to severe infections. Therefore, conventional or rapid diagnostic workflows should be modified depending on patients' urgency and preliminary colonization data. Additionally, it is essential to complete each microbiological report with rapid phenotypic minimum inhibitory concentration (MIC) values and information about resistance markers. Microbiologists also help in the eventual integration of ultimate genome analysis techniques into complicated diagnostic workflows. Herein, we want to emphasize the role of the microbiologist in the decisional process of critical patient management.

The complement system as a key modulator of the oral microbiome in health and disease

In this review, we address the interplay between the complement system and host microbiomes in health and disease, focussing on oral bacteria known to contribute to homeostasis or to promote dysbiosis associated with dental caries and periodontal diseases. Host proteins modulating complement activities in the oral environment and expression profiles of complement proteins in oral tissues were described. In addition, we highlight a sub-set of bacterial proteins involved in complement evasion and/or dysregulation previously characterized in pathogenic species (or strains), but further conserved among prototypical commensal species of the oral microbiome. Potential roles of these proteins in host-microbiome homeostasis and in the emergence of commensal strain lineages with increased virulence were also addressed. Finally, we provide examples of how commensal bacteria might exploit the complement system in competitive or cooperative interactions within the complex microbial communities of oral biofilms. These issues highlight the need for studies investigating the effects of the complement system on bacterial behaviour and competitiveness during their complex interactions within oral and extra-oral host sites.

Genomic and panproteomic analysis of the development of infant immune responses to antigenically-diverse pneumococci

Streptococcus pneumoniae (pneumococcus) is a nasopharyngeal commensal and respiratory pathogen. This study characterises the immunoglobulin G (IgG) repertoire recognising pneumococci from birth to 24 months old (mo) in a prospectively-sampled cohort of 63 children using a panproteome array. IgG levels are highest at birth, due to transplacental transmission of maternal antibodies. The subsequent emergence of responses to individual antigens exhibit distinct kinetics across the cohort. Stable differences in the strength of individuals' responses, correlating with maternal IgG concentrations, are established by 6 mo. By 12 mo, children develop unique antibody profiles that are boosted by re-exposure. However, some proteins only stimulate substantial responses in adults. Integrating genomic data on nasopharyngeal colonisation demonstrates rare pneumococcal antigens can elicit strong IgG levels post-exposure. Quantifying such responses to the diverse core loci (DCL) proteins is complicated by cross-immunity between variants. In particular, the conserved N terminus of DCL protein zinc metalloprotease B provokes the strongest early IgG responses. DCL proteins' ability to inhibit mucosal immunity likely explains continued pneumococcal carriage despite hosts' polyvalent antibody repertoire. Yet higher IgG levels are associated with reduced incidence, and severity, of pneumonia, demonstrating the importance of the heterogeneity in response strength and kinetics across antigens and individuals.

Disease-Associated Streptococcus pneumoniae Genetic Variation

Streptococcus pneumoniae is an opportunistic pathogen that causes substantial illness and death among children worldwide. The genetic backgrounds of pneumococci that cause infection versus asymptomatic carriage vary substantially. To determine the evolutionary mechanisms of opportunistic pathogenicity, we conducted a genomic surveillance study in China. We collected 783 S. pneumoniae isolates from infected and asymptomatic children. By using a 2-stage genomewide association study process, we compared genomic differences between infection and carriage isolates to address genomic variation associated with pathogenicity. We identified 8 consensus k-mers associated with adherence, antimicrobial resistance, and immune modulation, which were unevenly distributed in the infection isolates. Classification accuracy of the best k-mer predictor for S. pneumoniae infection was good, giving a simple target for predicting pathogenic isolates. Our findings suggest that S. pneumoniae pathogenicity is complex and multifactorial, and we provide genetic evidence for precise targeted interventions.

Complete genome analysis of Lactiplantibacillus plantarum VHProbi P06, a novel probiotic that resists Streptococcus pneumoniae in the upper respiratory tract

The purpose of this study was to screen lactic acid bacteria active against Streptococcus pneumoniae and to analyze the genetic basis of their probiotic functions from the genome. We isolated a novel Lactiplantibacillus plantarum VHProbi P06 from pickles, which showed strong antibacterial activity against S. pneumoniae, adhesion to 5-8F cells, and inhibition of S. pneumoniae colonization in the respiratory tract. Genome of VHProbi P06 was analyzed, we found one class II bacteriocin synthesis gene cluster. Genome of the strain contained 42 adhesion-related protein-coding genes, and implicated three exopolysaccharide biosynthesis gene clusters with low homologous to L. plantarum WCFS1. Moreover, VHProbi P06 possessed 3 intact phage regions and 117 Carbohydrate Active Enzyme genes. By comparing the genomes of five L. plantarum, 275 unique genes were found in VHProbi P06. Finally, the gene prediction was verified, the bacteriocin PlnJK produced by P06 was identified by LC-MS/MS, and the laminar exopolysaccharide with a weight-averaged molecular of 125.37 KDa was also found. This study provides a theoretical basis for the application of VHProbi P06 to the upper respiratory tract to resist pathogenic bacteria.

PepO and CppA modulate Streptococcus sanguinis susceptibility to complement immunity and virulence

Streptococcus sanguinis is a ubiquitous commensal species of the oral cavity commonly involved as an opportunistic pathogen in cardiovascular infections. In this study, we investigated the functions of endopeptidase O (PepO) and a C3-degrading protease (CppA) in the systemic virulence of S. sanguinis. Isogenic mutants of pepO and cppA obtained in strain SK36 showed increased susceptibility to C3b deposition and to opsonophagocytosis by human polymorphonuclear neutrophils (PMN). These mutants differ, however, in their profiles of binding to serum amyloid P component (SAP) and C1q, whereas both showed reduced interaction with C4b-binding protein (C4BP) and/or factor H (FH) regulators as compared to SK36. The two mutants showed defects in ex vivo persistence in human blood, serum-mediated invasion of HCAEC endothelial cells, and virulence in a Galleria mellonella infection model. The transcriptional activities of pepO and cppA, assessed by RT-qPCR in nine wild-type strains, further indicated strain-specific profiles of pepO/cppA expression. Moreover, non-conserved amino acid substitutions were detected among the strains, mostly in CppA. Phylogenetic comparisons with homologues of streptococcal species of the oral and oropharyngeal sites suggested that S. sanguinis PepO and CppA have independent ancestralities. Thus, this study showed that PepO and CppA are complement evasion proteins expressed by S. sanguinis in a strain-specific manner, which are required for multiple functions associated with cardiovascular virulence.

Molecular characterization of invasive Streptococcus pneumoniae clinical isolates from a tertiary children's hospital in eastern China

Streptococcus pneumoniae is a common opportunistic pathogen that causes invasive pneumococcal disease (IPD), especially in children. This study aimed to determine the prevalence and molecular characteristics of S. pneumoniae isolated from children with IPD. A total of 78 S. pneumoniae isolates from aseptic body fluids of 70 IPD patients were collected at the Children's Hospital of Nanjing Medical University (Jiangsu Province, China) during 2017-2021. Whole-genome sequencing technology was used to analyze the serotype, sequence type (ST), virulence, and antibiotic resistance of the 78 invasive S. pneumoniae clinical isolates. Our results showed that the pneumococcal infection rate declined after the COVID-19 outbreak in 2019. Serotypes 19F, 14, 6A, 23F, 19A, and 6B were the most common strains. The pneumococcal conjugate vaccine (PCV) 13 serotype coverage rate was 87.1%. All isolates were classified by multi-locus sequence typing (MLST) analysis into 27 different STs, including 3 novel STs (ST17941, ST17942, and ST17944) and 1 novel allele [recP (558)]. The most predominant ST was ST271, followed by ST320 and ST876. All isolates carried the following virulence genes: cbpG, lytB, lytC, pce (cbpE), pavA, slrA, plr (gapA), hysA, nanA, eno, piuA, psaA, cppA, iga, htrA (degP), tig (ropA), zmpB, and ply. All isolates were multidrug resistant and had high levels of resistance to macrolides, tetracyclines, and sulfonamides. Taken together, this study revealed extensive genetic diversity among S. pneumoniae isolates from a single Chinese hospital. Wearing masks, universal infant vaccination with PCV13, and the launch of recombinant protein vaccine development programs could reduce the burden of IPD in children. IMPORTANCE Invasive pneumococcal disease (IPD) caused by Streptococcus pneumoniae in children remains a global burden and should be given more attention due to the fact that the pneumococcal vaccine is not fully covered globally. The molecular epidemiological characteristics of S. pneumoniae are not so clear, especially in these years of COVID-19. In this study, we collected S. pneumoniae isolates from the aseptic body fluid of children with IPD from 2017 to 2021 in a tertiary children's hospital in China and revealed the extensive genetic diversity of these isolates. Most importantly, we first found that the rate of pneumococcal infection has declined since the COVID-19 outbreak in 2019, which means that wearing masks could reduce the transmission of S. pneumoniae. In addition, it was shown that universal infant vaccination with PCV13 seems essential for reducing the burden of IPD in children.

Long-acting vaccine delivery systems

Bolus vaccines are often administered multiple times due to rapid clearance and reduced transportation to draining lymph nodes resulting in inadequate activation of T and B lymphocytes. In order to achieve adaptive immunity, prolonged exposure of antigens to these immune cells is crucial. Recent research has been focusing on developing long-acting biomaterial-based vaccine delivery systems, which can modulate the release of encapsulated antigens or epitopes to facilitate enhanced antigen presentation in lymph nodes and subsequently achieve robust T and B cell responses. Over the past few years, various polymers and lipids have been extensively explored to develop effective biomaterial-based vaccine strategies. The article reviews relevant polymer and lipid-based strategies used to prepare long-acting vaccine carriers and discusses their results concerning immune responses.

In vivo characterization of the bacterial intramembrane-cleaving protease RseP using the heme binding tag-based assay iCliPSpy

Regulated intramembrane proteolysis (RIP) describes the protease-dependent cleavage of transmembrane proteins within the hydrophobic core of cellular membranes. Intramembrane-cleaving proteases (I-CliPs) that catalyze these reactions are found in all kingdoms of life and are involved in a wide range of cellular processes, including signaling and protein homeostasis. I-CLiPs are multispanning membrane proteins and represent challenging targets in structural and enzyme biology. Here we introduce iCLiPSpy, a simple assay to study I-CLiPs in vivo. To allow easy detection of enzyme activity, we developed a heme-binding reporter based on TNFα that changes color after I-CLiP-mediated proteolysis. Co-expression of the protease and reporter in Escherichia coli (E. coli) results in white or green colonies, depending on the activity of the protease. As a proof of concept, we use this assay to study the bacterial intramembrane-cleaving zinc metalloprotease RseP in vivo. iCLiPSpy expands the methodological repertoire for identifying residues important for substrate binding or activity of I-CLiPs and can in principle be adapted to a screening assay for the identification of inhibitors or activators of I-CLiPs, which is of great interest for proteases being explored as biomedical targets.

Control and Prevention of Invasive Pneumococcal Disease: A Current and Historical Perspective

Although significant progress has been made in reducing the incidence of invasive pneumococcal disease (IPD) in children, IPD remains a continued threat. Since the introduction of pneumococcal conjugate vaccines (PCVs), rates of IPD and non-IPD have substantially decreased. However, serotype replacement reversed some of the benefits of PCV7 and, more recently, PCV13. Several replacement serotypes are antibiotic resistant, which is a cause of concern for providers. The introduction of the higher-valency conjugate vaccines PCV15 and PCV20 is expected to provide greater serotype coverage; unfortunately, these vaccines do not include some of the recently emerged serotypes. Recommendations for the use of the 23-valent polysaccharide vaccine in high-risk populations may be modified because of the effectiveness of the newer PCVs. Pediatricians must be aware of the new vaccine strategies for the prevention of IPD and the manifestations of IPD so that prompt empirical therapy can be initiated when treatment is required. [Pediatr Ann. 2023;52(3):e96-e101.].

Vaccine-Preventable Diseases in Older Adults

Older adults are at an increased risk of vaccine-preventable diseases partly because of physiologic changes in the immune and other body systems related to age and/or accumulating comorbidities that increase the vulnerability to infections and decrease the response to vaccines. Strategies to improve the response to vaccines include using a higher antigenic dose (such as in the high-dose inactivated influenza vaccines) as well as adding adjuvants (such as MF59 in the adjuvanted inactivated influenza vaccine).

Antibiotic Resistance of Streptococcus pneumoniae in the Nasopharynx of Healthy Children Less than Five Years Old after the Generalization of Pneumococcal Vaccination in Marrakesh, Morocco

Streptococcus pneumoniae (S. pneumoniae) remains one of the most important pathogens causing childhood infections. The spread of antibiotic-resistant bacteria is a leading cause of treatment failure in children. The purpose of this investigation is to report the antibiotic and multidrug resistance (MDR) of S. pneumoniae strains isolated from healthy children throughout the years 2020–2022. Antimicrobial susceptibility testing of S. pneumoniae strains in selected antimicrobials was performed using disk diffusion and E-test methods on bloodMueller–Hinton agar. The antimicrobials tested included oxacillin, amoxicillin, ceftriaxone, norfloxacin, gentamicin, vancomycin, erythromycin, clindamycin, pristinamycin, tetracycline, chloramphenicol, and trimethoprim-sulfamethoxazole. A total of 201 S. pneumoniae strains were isolated from the nasopharynx of healthy children in Marrakesh, Morocco. The highest rate of resistance of S. pneumoniae was found in penicillin (57.2%), followed by tetracycline (20.9%), and erythromycin (17.9%). The rates of resistance to clindamycin, trimethoprim-sulfamethoxazole, and chloramphenicol were 14.9%, 4%, and 1.5%, respectively. All isolates were susceptible to norfloxacin, gentamicin, vancomycin, and pristinamycin. Approximately 17% of all S. pneumoniae strains were resistant to at least three different antibiotic families. This study showed a low rate of antibiotics resistance among nasopharyngeal S. pneumoniae strains, and it is thus essential to monitor S. pneumoniae susceptibility in healthy children.

Streptococcus pneumoniae promotes lung cancer development and progression

Streptococcus pneumoniae (SP) is associated with lung cancer, yet its role in the tumorigenesis remains uncertain. Herein we find that SP attaches to lung cancer cells via binding pneumococcal surface protein C (PspC) to platelet-activating factor receptor (PAFR). Interaction between PspC and PAFR stimulates cell proliferation and activates PI3K/AKT and nuclear factor kB (NF-kB) signaling pathways, which trigger a pro-inflammatory response. Lung cancer cells infected with SP form larger tumors in BALB/C mice compared to untreated cells. Mice treated with tobacco carcinogen and SP develop more lung tumors and had shorter survival period than mice treated with the carcinogen alone. Mutating PspC or PAFR abolishes tumor-promoting effects of SP. Overabundance of SP is associated with the survival. SP may play a driving role in lung tumorigenesis by activating PI3K/AKT and NF-kB pathways via binding PspC to PAFR and provide a microbial target for diagnosis and treatment of the disease.

Wogonin attenuates the pathogenicity of Streptococcus pneumoniae by double-target inhibition of Pneumolysin and Sortase A

Streptococcus pneumoniae (S. pneumoniae) is a major causative agent of respiratory disease in patients and can cause respiratory distress and other symptoms in severe cases. Pneumolysin (PLY) is a pore-forming toxin that induces host tissue injury and inflammatory responses. Sortase A (SrtA), a catalytic enzyme that anchors surface-associated virulence factors, is critical for S. pneumoniae virulence. Here, we found that the active ingredient of the Chinese herb Scutellaria baicalensis, wogonin, simultaneously inhibited the haemolytic activity of PLY and SrtA activity. Consequently, wogonin decreased PLY-mediated cell damage and reduced SrtA-mediated biofilm formation by S. pneumoniae. Furthermore, our data indicated that wogonin did not affect PLY expression but directly altered its oligomerization, leading to reduced activity. Furthermore, the analysis of a mouse pneumonia model further revealed that wogonin reduced mortality in mice infected with S. pneumoniae laboratory strain D39 and S. pneumoniae clinical isolate E1, reduced the number of colony-forming units in infected mice and decreased the W/D ratio and levels of the inflammatory factors TNF-α, IL-6 and IL-1β in the lungs of infected mice. Thus, wogonin reduces S. pneumoniae pathogenicity by inhibiting the dual targets PLY and SrtA, providing a treatment option for S. pneumoniae infection.

Meningitis patients with pneumonia: correlation between blood parameters and clinical features

Background: This research aimed to explore the possible relationship between the main experimental parameters and clinical status in meningitis patients with pneumonia infection. Methods: A retrospective analysis of the demographic characteristics, clinical features and laboratory parameters of meningitis patients was performed. Results: D-dimer, C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) exhibited good diagnostic ability for meningitis complicated with pneumonia. Additionally, we observed a positive correlation between D-dimer and CRP in cases of meningitis with pneumonia infection. D-dimer, ESR and Streptococcus pneumoniae (S. pneumoniae) were independently associated with meningitis patients with pneumonia infection. Conclusion: D-dimer, CRP, ESR and S. pneumoniae infection may effectively anticipate disease progression and adverse consequences in meningitis patients with pneumonia infection.

Heat shock protein 40 of Streptococcus pneumoniae induces immune response of human dendritic cells via TLR4-dependent p38 MAPK and JNK signaling pathways

INTRODUCTION

Heat shock protein 40 (HSP40) is a vaccine adjuvant candidate for Streptococcus pneumoniae. The mechanism by which HSP40 activates the human dendritic cells (DCs) is unclear.

METHODS

DCs were isolated from human peripheral blood and their markers (HLA-DR, CD86, CD83, and CD80) were detected by flow cytometry. The messenger RNA (mRNA) and secretion levels of inflammary cytokines were measured after DCs were stimulated with recombinant HSP40 (rHSP40). Short hairpin RNAs were used to knock down toll-like receptor 2 (TLR2) and TLR4. The TLR2- or TLR4-deficient DCs were treated with lipopolysaccharides, rHSP40, or peptidoglycan, and then the secretion levels of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) were measured. Moreover, the secretion levels of TNF-α and IL-6 were measured after DCs were treated with mitogen-activated protein kinase (MAPK) inhibitors including SB203580, SP600125, and U0126. In addition, the phosphorylation levels of p38 MAPK and Jun N-terminal kinase (JNK) in DC cells were determined using western blot analysis after treatment with rHSP40 for different times.

RESULTS

DCs were successfully isolated and cultured. rHSP40 treatment significantly increased cytokine levels in a concentration-dependent manner. TLR4 deficiency, but not TLR2 deficiency, significantly suppressed the rHSP40-induced secretion of tumor necrosis factor-α  (TNF-α) and interleukin-6 (IL-6). SB203580 and SP600125 significantly inhibited the rHSP40-induced secretion of TNF-α and IL-6. rHSP40 significantly enhanced the phosphorylation of p38 MAPK and JNK.

CONCLUSION

HPS40 stimulates the immune response of DCs via the p38 MAPK and JNK signaling pathways, which depend on TLR4.

A substrate-induced gating mechanism is conserved among Gram-positive IgA1 metalloproteases

The mucosal adaptive immune response is dependent on the production of IgA antibodies and particularly IgA1, yet opportunistic bacteria have evolved mechanisms to specifically block this response by producing IgA1 proteases (IgA1Ps). Our lab was the first to describe the structures of a metal-dependent IgA1P (metallo-IgA1P) produced from Gram-positive Streptococcus pneumoniae both in the absence and presence of its IgA1 substrate through cryo-EM single particle reconstructions. This prior study revealed an active-site gating mechanism reliant on substrate-induced conformational changes to the enzyme that begged the question of whether such a mechanism is conserved among the wider Gram-positive metallo-IgA1P subfamily of virulence factors. Here, we used cryo-EM to characterize the metallo-IgA1P of a more distantly related family member from Gemella haemolysans, an emerging opportunistic pathogen implicated in meningitis, endocarditis, and more recently bacteremia in the elderly. While the substrate-free structures of these two metallo-IgA1Ps exhibit differences in the relative starting positions of the domain responsible for gating substrate, the enzymes have similar domain orientations when bound to IgA1. Together with biochemical studies that indicate these metallo-IgA1Ps have similar binding affinities and activities, these data indicate that metallo-IgA1P binding requires the specific IgA1 substrate to open the enzymes for access to their active site and thus, largely conform to an "induced fit" model.

Shionone-Targeted Pneumolysin to Ameliorate Acute Lung Injury Induced by Streptococcus pneumoniae In Vivo and In Vitro

Streptococcus pneumoniae (S. pneumoniae), as a Gram-positive bacterium, can cause severe bacterial pneumonia, and result in high morbidity and mortality in infected people. Meanwhile, isolated drug-resistant S. pneumoniae is growing, which raises concerns about strategies for combatting S. pneumoniae infection. To disturb S. pneumoniae pathogenicity and its drug-resistance, developing novel anti-infective strategies or compounds is urgent. In this study, the anti-infective effect of shionone was explored. A minimum inhibitory concentration (MIC) assay and growth curve determination were performed to evaluate the effect of the tetracyclic triterpenoid compound shionone against S. pneumoniae. Hemolysis tests, western blotting, oligomerization inhibition assays, and molecular docking were carried out to explore the anti-infective mechanism of shionone. Moreover, the protective effect of shionone was also confirmed in a mousepneumonia model. The results showed that the excellent hemolytic inhibitory activity of shionone was observed at less than 8 μg/mL. Meanwhile, shionone could disturb the oligomerization of pneumolysin (PLY) but did not interfere with PLY expression at less than 4 μg/mL. Molecular docking suggested that shionone targeted the ASP-59, ILE-60, THR-57, PHE-344, and ASN-346 amino acid sites to reduce S. pneumoniae pathogenicity. Furthermore, shionone alleviated lung histopathologic injury and decreased lung bacterial colonization in vivo. The above results showed that shionone could bind to the PLY active pocket under the concentrations of 8 μg/mL and neutralize PLY hemolysis activity to reduce S. pneumoniae pathogenicity in vitro and in vivo.

The emerging role of NOTCH3 receptor signalling in human lung diseases

The mammalian respiratory system or lung is a tree-like branching structure, and the main site of gas exchange with the external environment. Structurally, the lung is broadly classified into the proximal (or conducting) airways and the distal alveolar region, where the gas exchange occurs. In parallel with the respiratory tree, the pulmonary vasculature starts with large pulmonary arteries that subdivide rapidly ending in capillaries adjacent to alveolar structures to enable gas exchange. The NOTCH signalling pathway plays an important role in lung development, differentiation and regeneration post-injury. Signalling via the NOTCH pathway is mediated through activation of four NOTCH receptors (NOTCH1-4), with each receptor capable of regulating unique biological processes. Dysregulation of the NOTCH pathway has been associated with development and pathophysiology of multiple adult acute and chronic lung diseases. This includes accumulating evidence that alteration of NOTCH3 signalling plays an important role in the development and pathogenesis of chronic obstructive pulmonary disease, lung cancer, asthma, idiopathic pulmonary fibrosis and pulmonary arterial hypertension. Herein, we provide a comprehensive summary of the role of NOTCH3 signalling in regulating repair/regeneration of the adult lung, its association with development of lung disease and potential therapeutic strategies to target its signalling activity.

Genomic investigation of a Streptococcus pneumoniae serotype 24F strain causing meningoencephalitis in Hong Kong

Pneumococcal conjugate vaccines (PCVs) successfully decreased the incidence of invasive pneumococcal disease in children. However, many countries have reported serotype replacement and a rebound in diseases from non-vaccine serotypes. Here, we report the genomic investigation of a Streptococcus pneumoniae strain M215 that caused severe meningoencephalitis in an infant in 2019. The strain was assigned to serotype 24F using the bioinformatic pipeline SeroBA and pneumococcal type specific anti-sera. The strain was resistant to cotrimoxazole from mutations in both folA and folP genes. It was susceptible to penicillin and other non-β-lactam antibiotics. Phylogenetically, it belongs to Global Pneumococcal Sequence Cluster (GPSC) 6 and multi-locus sequence type 162. A total of 38 virulence genes were detected in the genome of M215. Upon comparison of the profile of virulence genes, GPSC6 but not non-GPSC6 strains of serotype 24F and related serotypes were found to possess the major virulence determinant, pilus islet-1, comprising genes encoding sortases (srtB, srtC, srtD), pilus proteins (rrgA, rrgB and rrgC) and one transcriptional regulator (rlrA), which was previously described to be characteristic feature of international clones in the pre-PCV era. In our locality, this represented the first detection of serotype 24F and GPSC6/ST162 causing serious pneumococcal disease. The emergence of the non-vaccine serotype 24F GPSC6/ST162 lineage with molecular feature of high virulence is concerning and emphasizes the need for full characterization of strains causing severe disease.

Pneumococcal Extracellular Serine Proteases: Molecular Analysis and Impact on Colonization and Disease

The pathobiont Streptococcus pneumoniae causes life-threatening diseases, including pneumonia, sepsis, meningitis, or non-invasive infections such as otitis media. Serine proteases are enzymes that have been emerged during evolution as one of the most abundant and functionally diverse group of proteins in eukaryotic and prokaryotic organisms. S. pneumoniae expresses up to four extracellular serine proteases belonging to the category of trypsin-like or subtilisin-like family proteins: HtrA, SFP, PrtA, and CbpG. These serine proteases have recently received increasing attention because of their immunogenicity and pivotal role in the interaction with host proteins. This review is summarizing and focusing on the molecular and functional analysis of pneumococcal serine proteases, thereby discussing their contribution to pathogenesis.

Zoonotic infection and clonal dissemination of Streptococcus equi subspecies zooepidemicus sequence type 194 isolated from humans in Thailand

Streptococcus equi subsp. zooepidemicus (SEZ) is a zoonotic pathogen associated with diseases in a wide range of animals as well as in humans. SEZ sequence type (ST) 194 strains have been associated with outbreaks in China, the USA, and Canada and have caused high mortality in pigs. Nevertheless, human infection by this ST has never been reported. This study conducted a retrospective analysis of 18 SEZ strains from human patients in Thailand during 2005-2020. The study revealed clonal dissemination of ST194 with the identical pulsotype in human patients throughout Thailand. Clinical manifestation was mainly septicemia (61.1%), while 72.2% had a history of eating raw pork products. There were six fatal cases (33.3%). Antimicrobial susceptibility testing revealed that all strains were susceptible to penicillin, ampicillin, cefotaxime, erythromycin, levofloxacin, clindamycin, chloramphenicol, tetracycline and vancomycin. Virulence-associated genes, including bifA, szM, szP, sdzD, spaZ, and fszF, were present in all tested strains. Some representative genes in four pathogenicity islands found in the swine outbreak SEZ-ATCC35246 (ST194) strain were detected in these SEZ strains. Whole-genome sequencing analysis of three representative SEZs in this study revealed no acquired antimicrobial-resistant genes and they contained the same virulence factors. The single-nucleotide polymorphism phylogenetic tree demonstrated that the current strains were clustered with swine ST194 strains. The results should be highlighted as a public health concern, especially to those who may directly or indirectly have contact with livestock or companion animals or have consumed raw meat products as risk factors for infections with SEZ.