Pneumococcal virulence factors: structure and function

Impact of Endogenous Pneumococcal Hydrogen Peroxide on the Activity and Release of Pneumolysin

Streptococcus pneumoniae is the leading cause of community-acquired pneumonia. The pore-forming cholesterol-dependent cytolysin (CDC) pneumolysin (PLY) and the physiological metabolite hydrogen peroxide (H2O2) can greatly increase the virulence of pneumococci. Although most studies have focused on the contribution of both virulence factors to the course of pneumococcal infection, it is unknown whether or how H2O2 can affect PLY activity. Of note, S. pneumoniae exploits endogenous H2O2 as an intracellular signalling molecule to modulate the activity of several proteins. Here, we demonstrate that H2O2 negatively affects the haemolytic activity of PLY in a concentration-dependent manner. Prevention of cysteine-dependent sulfenylation upon substitution of the unique and highly conserved cysteine residue to serine in PLY significantly reduces the toxin's susceptibility to H2O2 treatment and completely abolishes the ability of DTT to activate PLY. We also detect a clear gradual correlation between endogenous H2O2 generation and PLY release, with decreased H2O2 production causing a decline in the release of PLY. Comparative transcriptome sequencing analysis of the wild-type S. pneumoniae strain and three mutants impaired in H2O2 production indicates enhanced expression of several genes involved in peptidoglycan (PG) synthesis and in the production of choline-binding proteins (CPBs). One explanation for the impact of H2O2 on PLY release is the observed upregulation of the PG bridge formation alanyltransferases MurM and MurN, which evidentially negatively affect the PLY release. Our findings shed light on the significance of endogenous pneumococcal H2O2 in controlling PLY activity and release.

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.

Oxidation of hemoproteins by Streptococcus pneumoniae collapses the cell cytoskeleton and disrupts mitochondrial respiration leading to cytotoxicity of human lung cells

Streptococcus pneumoniae (Spn) causes pneumonia that kills millions through acute toxicity and invasion of the lung parenchyma. During aerobic respiration, Spn releases hydrogen peroxide (Spn-H 2 O 2 ), as a by-product of enzymes SpxB and LctO, and causes cell death with signs of both apoptosis and pyroptosis by oxidizing unknown cell targets. Hemoproteins are molecules essential for life and prone to oxidation by H 2 O 2 . We recently demonstrated that during infection-mimicking conditions, Spn-H 2 O 2 oxidizes the hemoprotein hemoglobin (Hb), releasing toxic heme. In this study, we investigated details of the molecular mechanism(s) by which the oxidation of hemoproteins by Spn-H 2 O 2 causes human lung cell death. Spn strains, but not H 2 O 2 -deficient SpnΔ spxB Δ lctO strains caused time-dependent cell cytotoxicity characterized by the rearrangement of the actin, the loss of the microtubule cytoskeleton and nuclear contraction. Disruption of the cell cytoskeleton correlated with the presence of invasive pneumococci and an increase of intracellular reactive oxygen species. In cell culture, the oxidation of Hb or cytochrome c (Cyt c ) caused DNA degradation and mitochondrial dysfunction from inhibition of complex I-driven respiration, which was cytotoxic to human alveolar cells. Oxidation of hemoproteins resulted in the creation of a radical, which was identified as a protein derived side chain tyrosyl radical by using electron paramagnetic resonance (EPR). Thus, we demonstrate that Spn invades lung cells, releasing H 2 O 2 that oxidizes hemoproteins, including Cyt c , catalyzing the formation of a tyrosyl side chain radical on Hb and causing mitochondrial disruption, that ultimately leads to the collapse of the cell cytoskeleton.

Identification of Subunits for Novel Universal Vaccines against Three Predominant Serogroups and the Emerging O145 among Avian Pathogenic Escherichia coli by Pan-RV Pipeline

Avian pathogenic Escherichia coli, a causative agent of avian colibacillosis, has been causing serious economic losses in the poultry industry. The increase in multidrug-resistant isolates and the complexity of the serotypes of this pathogen, especially the recently reported emergence of a newly predominant serogroup of O145, make the control of this disease difficult. To address this challenge, a high-throughput screening approach, called Pan-RV (Reverse vaccinology based on pangenome analysis), is proposed to search for universal protective antigens against the three traditional serogroups and the newly emerged O145. Using this approach, a total of 61 proteins regarded as probable antigens against the four important serogroups were screened from the core genome of 127 Avian pathogenic Escherichia coli (APEC) genomes, and six were verified by Western blots using antisera. Overall, our research will provide a foundation for the development of an APEC subunit vaccine against avian colibacillosis. Given the exponential growth of whole-genome sequencing (WGS) data, our Pan-RV pipeline will make screening of bacterial vaccine candidates inexpensive, rapid, and efficient. IMPORTANCE With the emergence of drug resistance and the newly predominant serogroup O145, the control of Avian pathogenic Escherichia coli is facing a serious challenge; an efficient immunological method is urgently needed. Here, for the first time, we propose a high-throughput screening approach to search for universal protective antigens against the three traditional serogroups and the newly emerged O145. Importantly, using this approach, a total of 61 proteins regarded as probable antigens against the four important serogroups were screened, and three were shown to be immunoreactive with all antisera (covering the four serogroups), thereby providing a foundation for the development of APEC subunit vaccines against avian colibacillosis. Further, our Pan-RV pipeline will provide immunological control strategies for pathogens with complex and variable genetic backgrounds such as Escherichia coli and will make screening of bacterial vaccine candidates more inexpensive, rapid, and efficient.

Analysis of Whole-Genome Sequences of Pathogenic Gram-Positive and Gram-Negative Isolates from the Same Hospital Environment to Investigate Common Evolutionary Trends Associated with Horizontal Gene Exchange, Mutations and DNA Methylation Patterning

Hospital-acquired infections are a generally recognized problem for healthcare professionals. Clinical variants of Gram-negative and Gram-positive pathogens are characterized with enhanced antibiotic resistance and virulence due to mutations and the horizontal acquisition of respective genetic determinants. In this study, two Escherichia coli, two Klebsiella pneumoniae, three Pseudomonas aeruginosa, two Staphylococcus aureus, one Staphylococcus epidermidis and one Streptococcus pneumoniae showing broad spectra of antibiotic resistance were isolated from patients suffering from nosocomial infections in a local hospital in Almaty, Kazakhstan. The aim of the study was to compare general and species-specific pathways of the development of virulence and antibiotic resistance through opportunistic pathogens causing hospital-acquired infections. The whole-genome PacBio sequencing of the isolates allowed for the genotyping and identification of antibiotic resistance and virulence genetic determinants located in the chromosomes, plasmids and genomic islands. It was concluded that long-read sequencing is a useful tool for monitoring the epidemiological situation in hospitals. Marker antibiotic resistance mutations common for different microorganisms were identified, which were acquired due to antibiotic-selective pressure in the same clinical environment. The genotyping and identification of strain-specific DNA methylation motifs were found to be promising in estimating the risks associated with hospital infection outbreaks and monitoring the distribution and evolution of nosocomial pathogens.

Chitosan loaded RNA polymerase inhibitor nanoparticles increased attenuation in toxin release from Streptococcus pneumonia

Background

Multidrug-resistant (MDR) bacterial infections have become an emerging health concern around the world. Antibiotics resistance among S. pneumoniae strains increased recently contributing to increase in incidence of pneumococcal infection. This necessitates the discovery of novel antipnemococcal such as compound C3-005 which target the interaction between RNA polymerase and σ factors. Chitosan nanoparticles (CNPs) exhibited antibacterial activity including S. pneumonia. Therefore, the aims of the current investigation were to formulate CNPs loaded with C3-005 and characteristic their antimicrobial properties against S. pneumonia.

Methods

The CNPs and C3-005 loaded CNPs were produced utilizing ionic gelation method, and their physicochemical characteristics including particle size, zeta potential, polydispersity index (PDI), encapsulation efficiency (EE%), and in vitro release profile were studied. Both differential scanning calorimetry (DSC) and fourier transform infrared spectroscopy (FTIR) were used for chemical characterization. The synthesized NPs' minimum inhibitory concentration (MIC) was determined using killing assay and broth dilution method, and their impact on bacteria induced hemolysis were also studied.

Results

The NPs encapsulating C3-005 were successfully prepared with particle size of 343.5 nm ± 1.3, zeta potential of 29.8 ± 0.37, and PDI of 0.20 ± 0.03. 70 % of C3-005 were encapsulated in CNPs and sustained release pattern of C3-005 from CNPs was revealed by an in vitro release study. CNPs containing C3-005 exhibited higher antipnomcoccal activity with MIC₅₀ of 30 µg/ml when compared with C3-005 and empty CNPs alone. The prepared C3-CNPs showed a reduction of bacterial hemolysis in a concentration-related (dependent) manner and was higher than C3-005 alone.

Conclusions

The findings of this study showed the potential for using C3-005 loaded CNPs to treat pneumococcal infection.

Oxidative Reactions Catalyzed by Hydrogen Peroxide Produced by Streptococcus pneumoniae and Other Streptococci Cause the Release and Degradation of Heme from Hemoglobin

Streptococcus pneumoniae (Spn) strains cause pneumonia that kills millions every year worldwide. Spn produces Ply, a hemolysin that lyses erythrocytes releasing hemoglobin, and also produces the pro-oxidant hydrogen peroxide (Spn-H2O2) during growth. The hallmark of the pathophysiology of hemolytic diseases is the oxidation of hemoglobin, but oxidative reactions catalyzed by Spn-H2O2 have been poorly studied. We characterized the oxidation of hemoglobin by Spn-H2O2. We prepared a series of single-mutant (ΔspxB or ΔlctO), double-mutant (ΔspxB ΔlctO), and complemented strains in TIGR4, D39, and EF3030. We then utilized an in vitro model with oxyhemoglobin to demonstrate that oxyhemoglobin was oxidized rapidly, within 30 min of incubation, by Spn-H2O2 to methemoglobin and that the main source of Spn-H2O2 was pyruvate oxidase (SpxB). Moreover, extended incubation caused the release and the degradation of heme. We then assessed oxidation of hemoglobin and heme degradation by other bacterial inhabitants of the respiratory tract. All hydrogen peroxide-producing streptococci tested caused the oxidation of hemoglobin and heme degradation, whereas bacterial species that produce <1 μM H2O2 neither oxidized hemoglobin nor degraded heme. An ex vivo bacteremia model confirmed that oxidation of hemoglobin and heme degradation occurred concurrently with hemoglobin that was released from erythrocytes by Ply. Finally, gene expression studies demonstrated that heme, but not red blood cells or hemoglobin, induced upregulated transcription of the spxB gene. Oxidation of hemoglobin may be important for pathogenesis and for the symbiosis of hydrogen peroxide-producing bacteria with other species by providing nutrients such as iron.

Pathogenesis of Streptococcus pneumoniae serotype 3 during natural colonization and infections among children and its IgG correlate of protection in a mouse model

Current licensed pneumococcal conjugate vaccines (PCVs) are effective against pneumococcal diseases caused by the serotypes contained in the PCvs However; several studies evaluating pneumococcal colonization and acute otitis-media (AOM) prevention in young children vaccinated with PCV13, observed less effectiveness against serotype-3. One possible reason for less effectiveness may be release of the capsular polysaccharide (CPS) of serotype-3 (CPS-3) as an immune evasion mechanism. Here we evaluated free CPS-3 levels released from 6 clinical isolates from young children compared to WU2 strain and to serotype-19A CPS (CPS-19A) released in vitro when interacting with nasopharyngeal, middle-ear and lung cell-lines. Clinical serotype-3 strains showed greater release of CPS than WU2 with the interaction to 2 cell-lines and all 6 clinical serotype-19A strains. We next evaluated CPS-3 vs CPS-19A levels in middle-ear fluid (MEF) and the nasopharynx (NP) of young children and found higher levels of CPS-3 compared to CPS-19A in MEF during AOM but not in NP secretions during colonization. With anti-CPS-3 IgG in MEF and NP secretions at time of health and onset of AOM, a significant negative correlation (r = -0.75, p < 0.05) between unbound anti-CPS-3 IgG levels and free- anti-CPS-3 in MEF were found, and a significant lower detection of unbound anti-CPS-3 IgG in NP at the time of health with serotype-3 SPN (p < 0.05) compared to irrelevant SPN serotypes were found. In a mouse model of AOM and pneumonia, we sought a correlate of protection against serotype-3 infection using human serum-derived anti-CPS-3 IgG. We conclude that serotype-3 clinical isolates from children release more capsule than WU2 strains or 19A strains during in vitro testing; release more capsule in the MEF of children during AOM than serotype 19A; unbound anti-CPS-3 IgG levels negatively correlate with free-anti-CPS-3; and a level of 2.8 µg/ml anti-CPS-3 antibody protects mice from AOM and pneumonia but not colonization.

Acoustic force spectroscopy reveals subtle differences in cellulose unbinding behavior of carbohydrate-binding modules

Protein adsorption to solid carbohydrate interfaces is critical to many biological processes, particularly in biomass deconstruction. To engineer more-efficient enzymes for biomass deconstruction into sugars, it is necessary to characterize the complex protein-carbohydrate interfacial interactions. A carbohydrate-binding module (CBM) is often associated with microbial surface-tethered cellulosomes or secreted cellulase enzymes to enhance substrate accessibility. However, it is not well known how CBMs recognize, bind, and dissociate from polysaccharides to facilitate efficient cellulolytic activity, due to the lack of mechanistic understanding and a suitable toolkit to study CBM-substrate interactions. Our work outlines a general approach to study the unbinding behavior of CBMs from polysaccharide surfaces using a highly multiplexed single-molecule force spectroscopy assay. Here, we apply acoustic force spectroscopy (AFS) to probe a Clostridium thermocellum cellulosomal scaffoldin protein (CBM3a) and measure its dissociation from nanocellulose surfaces at physiologically relevant, low force loading rates. An automated microfluidic setup and method for uniform deposition of insoluble polysaccharides on the AFS chip surfaces are demonstrated. The rupture forces of wild-type CBM3a, and its Y67A mutant, unbinding from nanocellulose surfaces suggests distinct multimodal CBM binding conformations, with structural mechanisms further explored using molecular dynamics simulations. Applying classical dynamic force spectroscopy theory, the single-molecule unbinding rate at zero force is extrapolated and found to agree with bulk equilibrium unbinding rates estimated independently using quartz crystal microbalance with dissipation monitoring. However, our results also highlight critical limitations of applying classical theory to explain the highly multivalent binding interactions for cellulose-CBM bond rupture forces exceeding 15 pN.

Investigating the Streptococcus sinensis competence regulon through a combination of transcriptome analysis and phenotypic evaluation

Streptococcus sinensis is a recently identified member of the Mitis group of streptococci. This species has been associated with infective endocarditis; however its mechanisms of pathogenesis and virulence are not fully understood. This study aimed to investigate the influence of the competence-stimulating peptide (CSP) and the competence regulon quorum-sensing circuitry (ComABCDE) on subsequent gene transcription and expression, as well as resultant phenotypes. In this study we confirmed the native CSP identity, ascertained when endogenous CSP was produced and completed a transcriptome-wide analysis of all genes following CSP exposure. RNA sequencing analysis revealed the upregulation of genes known to be associated with competence, biofilm formation and virulence. As such, a variety of phenotypic assays were utilized to assess the correlation between increased mRNA expression and potential phenotype response, ultimately gaining insight into the effects of CSP on both gene expression and developed phenotypes. The results indicated that the addition of exogenous CSP aided in competence development and successful transformation, yielding an average transformation efficiency comparable to that of other Mitis group streptococci. Additional studies are needed to further delineate the effects of CSP exposure on biofilm formation and virulence. Overall, this study provides novel information regarding S. sinensis and provides a substantial foundation on which this species and its role in disease pathogenesis can be further investigated.

Diversity of amino acid substitutions of penicillin-binding proteins in penicillin-non-susceptible and non-vaccine type Streptococcus pneumoniae

PURPOSE

In Japan, the introduction of pneumococcal conjugate vaccine (PCV) in children has decreased vaccine-type (VT) pneumococcal infections caused by penicillin (PEN)-non-susceptible Streptococcus pneumoniae. PEN-non-susceptible strains have gradually emerged among non-vaccine types (NVT). In this study, we aim to investigate the pbp gene mutations and the characteristics of PEN-binding proteins (PBPs) that mediate PEN resistance in NVT strains.

MATERIALS AND METHODS

Pneumococcal 41 strains of NVT isolated from patients with invasive pneumococcal infection were randomly selected. Nucleotide sequences for pbp genes encoding PBP1A, PBP2X, and PBP2B were analyzed, and amino acid (AA) substitutions that contribute to β-lactam resistance were identified. In addition, the three-dimensional (3D) structure of abnormal PBPs in the resistant strain was compared with that of a reference R6 strain via homology modeling.

RESULTS

In PEN-non-susceptible NVT strains, Thr to Ala or Ser substitutions in the conserved AA motif (STMK) were important in PBP1A and PBP2X. In PBP2B, substitutions from Thr to Ala, adjacent to the SSN motif, and from Glu to Gly were essential. The 3D structure modeling indicated that AA substitutions are characterized by accumulation around the enzymatic active pocket in PBPs. Many AA substitutions detected throughout the PBP domains were not associated with resistance, except for AA substitutions in or adjacent to AA motifs. Clonal complexes and sequence types showed that almost all NVT cases originated in other countries and spread to Japan via repeat mutations.

CONCLUSIONS

NVT with diverse AA substitutions increased gradually with pressure from both antimicrobial agents and vaccines.

Modulating streptococcal phenotypes using signal peptide analogues

Understanding bacterial communication mechanisms is imperative to improve our current understanding of bacterial infectivity and find alternatives to current modes of antibacterial therapeutics. Both Gram-positive and Gram-negative bacteria use quorum sensing (QS) to regulate group behaviours and associated phenotypes in a cell-density-dependent manner. Group behaviours, phenotypic expression and resultant infection and disease can largely be attributed to efficient bacterial communication. Of particular interest are the communication mechanisms of Gram-positive bacteria known as streptococci. This group has demonstrated marked resistance to traditional antibiotic treatment, resulting in increased morbidity and mortality of infected hosts and an ever-increasing burden on the healthcare system. Modulating circuits and mechanisms involved in streptococcal communication has proven to be a promising anti-virulence therapeutic approach that allows managing bacterial phenotypic response but does not affect bacterial viability. Targeting the chemical signals bacteria use for communication is a promising starting point, as manipulation of these signals can dramatically affect resultant bacterial phenotypes, minimizing associated morbidity and mortality. This review will focus on the use of modified peptide signals in modulating the development of proliferative phenotypes in different streptococcal species, specifically regarding how such modification can attenuate bacterial infectivity and aid in developing future alternative therapeutic agents.

Streptococcus pneumoniae interactions with the complement system

Host innate and adaptive immunity to infection with Streptococcus pneumoniae is critically dependent on the complement system, demonstrated by the high incidence of invasive S. pneumoniae infection in people with inherited deficiency of complement components. The complement system is activated by S. pneumoniae through multiple mechanisms. The classical complement pathway is activated by recognition of S. pneumoniae by C-reactive protein, serum amyloid P, C1q, SIGN-R1, or natural or acquired antibody. Some S. pneumoniae strains are also recognised by ficolins to activate the mannose binding lectin (MBL) activation pathway. Complement activation is then amplified by the alternative complement pathway, which can also be activated by S. pneumoniae directly. Complement activation results in covalent linkage of the opsonic complement factors C3b and iC3b to the S. pneumoniae surface which promote phagocytic clearance, along with complement-mediated immune adherence to erythrocytes, thereby protecting against septicaemia. The role of complement for mucosal immunity to S. pneumoniae is less clear. Given the major role of complement in controlling infection with S. pneumoniae, it is perhaps unsurprising that S. pneumoniae has evolved multiple mechanisms of complement evasion, including the capsule, multiple surface proteins, and the toxin pneumolysin. There is considerable variation between S. pneumoniae capsular serotypes and genotypes with regards to sensitivity to complement which correlates with ability to cause invasive infections. However, at present we only have a limited understanding of the main mechanisms causing variations in complement sensitivity between S. pneumoniae strains and to non-pathogenic streptococci.

Insights Into Amentoflavone: A Natural Multifunctional Biflavonoid

Amentoflavone is an active phenolic compound isolated from Selaginella tamariscina over 40 years. Amentoflavone has been extensively recorded as a molecule which displays multifunctional biological activities. Especially, amentoflavone involves in anti-cancer activity by mediating various signaling pathways such as extracellular signal-regulated kinase (ERK), nuclear factor kappa-B (NF-κB) and phosphoinositide 3-kinase/protein kinase B (PI3K/Akt), and emerges anti-SARS-CoV-2 effect via binding towards the main protease (Mpro/3CLpro), spike protein receptor binding domain (RBD) and RNA-dependent RNA polymerase (RdRp) of SARS-CoV-2. Therefore, amentoflavone is considered to be a promising therapeutic agent for clinical research. Considering the multifunction of amentoflavone, the current review comprehensively discuss the chemistry, the progress in its diverse biological activities, including anti-inflammatory, anti-oxidation, anti-microorganism, metabolism regulation, neuroprotection, radioprotection, musculoskeletal protection and antidepressant, specially the fascinating role against various types of cancers. In addition, the bioavailability and drug delivery of amentoflavone, the molecular mechanisms underlying the activities of amentoflavone, the molecular docking simulation of amentoflavone through in silico approach and anti-SARS-CoV-2 effect of amentoflavone are discussed.

A Small Non-Coding RNA Modulates Expression of Pilus-1 Type in Streptococcus pneumoniae

Streptococcus pneumoniae is a major cause of morbidity and mortality worldwide, and about 30% of the pneumococcal clinical isolates show type I pili-like structures. These long proteinaceous polymers extending from the bacterial surface are encoded by pilus islet 1 and play major roles in adhesion and host colonization. Pili expression is bistable and is controlled by the transcriptional activator RlrA. In this work, we demonstrate that the previously identified small noncoding RNA srn135 also participates in pilus regulation. Our findings show that srn135 is generated upon processing of the 5′-UTR region of rrgA messenger and its deletion prevents the synthesis of RrgA, the main pili adhesin. Moreover, overexpression of srn135 increases the expression of all pili genes and rises the percentage of piliated bacteria within a clonal population. This regulation is mediated by the stabilization of rlrA mRNA since higher levels of srn135 increase its half-life to 165%. Our findings suggest that srn135 has a dual role in pilus expression acting both in cis- (on the RrgA levels) and in trans- (modulating the levels of RlrA) and contributes to the delicate balance between pili expressing and non-expressing bacteria.

Nasopharyngeal Carriage of Streptococcus pneumoniae Among Young Children in Haiti Before Pneumococcal Conjugate Vaccine Introduction

BACKGROUND

Streptococcus pneumoniae, or pneumococcus, is a leading cause of morbidity and mortality in children worldwide. Pneumococcal conjugate vaccines (PCV) reduce carriage in the nasopharynx, preventing disease. We conducted a pneumococcal carriage study to estimate the prevalence of pneumococcal colonization, identify risk factors for colonization, and describe antimicrobial susceptibility patterns among pneumococci colonizing young children in Port-au-Prince, Haiti, before introduction of 13-valent PCV (PCV13).

METHODS

We conducted a cross-sectional study of children aged 6-24 months at an immunization clinic in Port-au-Prince between September 2015 and January 2016. Consenting parents were interviewed about factors associated with pneumococcal carriage; nasopharyngeal swabs were collected from each child and cultured for pneumococcus after broth enrichment. Pneumococcal isolates were serotyped and underwent antimicrobial susceptibility testing. We compared frequency of demographic, clinical, and environmental factors among pneumococcus-colonized children (carriers) to those who were not colonized (noncarriers) using unadjusted bivariate analysis and multivariate logistic regression.

RESULTS

Pneumococcus was isolated from 308 of the 685 (45.0%) children enrolled. Overall, 157 isolates (50.8%) were PCV13 vaccine-type serotypes; most common were 6A (13.3%), 19F (12.6%), 6B (9.7%), and 23F (6.1%). Vaccine-type isolates were significantly more likely to be nonsusceptible to ≥1 antimicrobial (63.1% vs 45.4%, P = .002). On bivariate analysis, carriers were significantly more likely than noncarriers to live in a household without electricity or running water, to share a bedroom with ≥3 people, to have a mother or father who did not complete secondary education, and to have respiratory symptoms in the 24 hours before enrollment (P < .05 for all comparisons). On multivariable analysis, completion of the pentavalent vaccination series (targeting diphtheria, pertussis, tetanus, hepatitis B, and Haemophilus influenzae type b) remained significantly more common among noncarriers.

CONCLUSIONS

Nearly a quarter of healthy children surveyed in Haiti were colonized with vaccine-type pneumococcal serotypes. This baseline carriage study will enable estimation of vaccine impact following nationwide introduction of PCV13.

Inactivation of Transcriptional Regulator FabT Influences Colony Phase Variation of Streptococcus pneumoniae

Streptococcus pneumoniae is an opportunistic pathogen that can alter its cell surface phenotype in response to the host environment. We demonstrated that the transcriptional regulator FabT is an indirect regulator of capsular polysaccharide, an important virulence factor of Streptococcus pneumoniae. Transcriptome analysis between the wild-type D39s and D39ΔfabT mutant strains unexpectedly identified a differentially expressed gene encoding a site-specific recombinase, PsrA. PsrA catalyzes the inversion of 3 homologous hsdS genes in a type I restriction-modification (RM) system SpnD39III locus and is responsible for the reversible switch of phase variation. Our study demonstrated that upregulation of PsrA in a D39ΔfabT mutant correlated with an increased ratio of transparent (T) phase variants. Inactivation of the invertase PsrA led to uniform opaque (O) variants. Direct quantification of allelic variants of hsdS derivatives and inversions of inverted repeats indicated that the recombinase PsrA fully catalyzes the inversion mediated by IR1 and IR3, and FabT mediated the recombination of the hsdS alleles in PsrA-dependent and PsrA-independent manners. In addition, compared to D39s, the ΔfabT mutant exhibited reduced nasopharyngeal colonization and was more resistant to phagocytosis and less adhesive to epithelial cells. These results indicated that phase variation in the ΔfabT mutant also affects other cell surface components involved in host interactions.

Strategies to Attenuate the Competence Regulon in Streptococcus pneumoniae

Streptococcus pneumoniae is an opportunistic respiratory human pathogen that poses a continuing threat to human health. Natural competence for genetic transformation in S. pneumoniae plays an important role in aiding pathogenicity and it is the best-characterized feature to acquire antimicrobial resistance genes by a frequent process of recombination. In S. pneumoniae, competence, along with virulence factor production, is controlled by a cell-density communication mechanism termed the competence regulon. In this review, we present the recent advances in the development of alternative methods to attenuate the pathogenicity of S. pneumoniae by targeting the various stages of the non-essential competence regulon communication system. We mainly focus on new developments related to competitively intercepting the competence regulon signaling through the introduction of promising dominant-negative Competence Stimulating Peptide (dnCSP) scaffolds. We also discuss recent reports on antibiotics that can block CSP export by disturbing the proton motive force (PMF) across the membrane and various ways to control the pneumococcal pathogenicity by activating the counter signaling circuit and targeting the pneumococcal proteome.

Post-13-Valent Pneumococcal Conjugate Vaccine Dynamics in Young Children of Serotypes Included in Candidate Extended-Spectrum Conjugate Vaccines

After worldwide implementation of 10-valent and 13-valent pneumococcal conjugate vaccines (PCV10/PCV13), a 20-valent PCV (PCV20) was developed. We assessed dynamics of non-PCV13 additional PCV20 serotypes (VT20–13), compared with all other non-VT20 serotypes, in children <2 years of age in late PCV13 (2015–2017) and early PCV (2009–2011) periods. Our prospective population-based multifaceted surveillance included isolates from carriage in healthy children, children requiring chest radiography for lower respiratory tract infections (LRTIs), and children with non-LRTI illness, as well as isolates from acute conjunctivitis, otitis media (OM), and invasive pneumococcal disease (IPD). After PCV13 implementation, VT20–13 increased disproportionally in OM, IPD, and carriage in LRTI. VT20–13/non-VT20 prevalence ratio range was 0.26–1.40. VT20–13 serotypes were more frequently antimicrobial-nonsusceptible than non-VT20 serotypes. The disproportionate increase of VT20–13 in respiratory infections and IPD points to their higher disease potential compared with all other non-VT20 as a group.

Prediction of human-Streptococcus pneumoniae protein-protein interactions using logistic regression

Streptococcus pneumoniae is a major cause of mortality in children under five years old. In recent years, the emergence of antibiotic-resistant strains of S. pneumoniae increases the threat level of this pathogen. For that reason, the exploration of S. pneumoniae protein virulence factors should be considered in developing new drugs or vaccines, for instance by the analysis of host-pathogen protein-protein interactions (HP-PPIs). In this research, prediction of protein-protein interactions was performed with a logistic regression model with the number of protein domain occurrences as features. By utilizing HP-PPIs of three different pathogens as training data, the model achieved 57-77 % precision, 64-75 % recall, and 96-98 % specificity. Prediction of human-S. pneumoniae protein-protein interactions using the model yielded 5823 interactions involving thirty S. pneumoniae proteins and 324 human proteins. Pathway enrichment analysis showed that most of the pathways involved in the predicted interactions are immune system pathways. Network topology analysis revealed β-galactosidase (BgaA) as the most central among the S. pneumoniae proteins in the predicted HP-PPI networks, with a degree centrality of 1.0 and a betweenness centrality of 0.451853. Further experimental studies are required to validate the predicted interactions and examine their roles in S. pneumoniae infection.

Immune Responses to Irradiated Pneumococcal Whole Cell Vaccine

Streptococcus pneumoniae (pneumococcus) can cause respiratory and systemic diseases. Recently, γ-irradiation-inactivated, non-encapsulated, intranasal S. pneumoniae (r-SP) vaccine has been introduced as a novel serotype-independent and cost-effective vaccine. However, the immunogenic mechanism of r-SP is poorly understood. Here, we comparatively investigated the protective immunity and immunogenicity of r-SP to the heat-(h-SP) or formalin-inactivated vaccine (f-SP) without adjuvants. Mice were intranasally immunized with each vaccine three times and then challenged with a lethal dose of S. pneumoniae TIGR4 strain and then subsequently evaluated for their immune responses. Immunization with r-SP elicited modestly higher protection against S. pneumoniae than h-SP or f-SP. Immunization with r-SP enhanced pneumococcal-specific IgA in the nasal wash and IgG in bronchoalveolar lavage fluid. Immunization with r-SP enhanced S. pneumoniae-specific IgG, IgG1, and IgG2b in the serum. r-SP more potently induced the maturation of dendritic cells in the cervical lymph nodes than h-SP or f-SP. Interestingly, populations of follicular helper T cells and IL-4-producing cells were potently increased in cervical lymph nodes of r-SP-immunized mice. Collectively, r-SP could be an effective intranasal, inactivated whole-cell vaccine in that it elicits S. pneumoniae-specific antibody production and follicular helper T cell activation leading to protective immune responses against S. pneumoniae infection.

CrfP, a fratricide protein, contributes to natural transformation in Streptococcus suis

Streptococcussuis (S.suis) is an important zoonotic pathogen that causes septicaemia, meningitis and streptococcal toxic shock-like syndrome in its host, and recent studies have shown that S.suis could be competent for natural genetic transformation. Transformation is an important mechanism for the horizontal transfer of DNA, but some elements that affect the transformation process need to be further explored. Upon entering the competent state, Streptococcus species stimulate the transcription of competence-related genes that are responsible for exogenous DNA binding, uptake and processing. In this study, we performed conserved promoter motif and qRT-PCR analyses and identified CrfP as a novel murein hydrolase that is widespread in S.suis and stimulated with a peptide pheromone in the competent state through a process controlled by ComX. A bioinformatics analysis revealed that CrfP consists of a CHAP hydrolase domain and two bacterial Src homology 3-binding (SH3b) domains. Further characterization showed that CrfP could be exported to extracellular bacterial cells and lytic S.suis strains of different serotypes, and this finding was verified by TEM and a turbidity assay. To investigate the potential effect of CrfP in vivo, a gene-deletion mutant (ΔcrfP) was constructed. Instead of stopping the natural transformation process, the inactivation of CrfP clearly reduced the effective transformation rate. Overall, these findings provide evidence showing that CrfP is important for S.suis serovar 2 competence.

Streptococcus pneumoniae endophthalmitis: clinical settings, antibiotic susceptibility, and visual outcomes

Streptococcus pneumoniae endophthalmitis is clinically more severe, more difficult to treat, and carry a higher risk of vision loss, evisceration, or enucleation. This study is to investigate the clinical settings, antibiotic susceptibility, and visual outcomes of S. pneumoniae endophthalmitis at a tertiary referral center in Taiwan. S. pneumoniae endophthalmitis was diagnosed in 38 eyes of 38 patients. The main clinical features were postcataract endophthalmitis (n = 13, 34%) and endophthalmitis associated with corneal ulcer (n = 12, 32%), trauma (n = 6, 16%), endogenous etiology (n = 4, 11%), trabeculectomy (n = 2, 5%), and pterygium excision-related scleral ulcer (n = 1, 3%). Presenting visual acuity ranged from counting fingers to no light perception. Pars plana vitrectomy with intravitreal antibiotics was performed in 17 eyes (39%) in primary or secondary treatments. S. pneumoniae isolates were susceptible to vancomycin (38/38, 100%), penicillin (37/38, 97%), ceftriaxone (37/38, 97%), cefuroxime (12/15, 80%), levofloxacin (13/15 ,87%), and moxifloxacin (15/17, 88%). Final visual acuity was better than 20/400 in 3 of 38 eyes (8%), 5/200 to hand motions in 3 eyes (8%), and light perception to no light perception in 32 eyes (84%). Ten eyes (26%) underwent evisceration or enucleation. Although S. pneumoniae isolates were susceptible to vancomycin, S. pneumoniae endophthalmitis had a very poor visual prognosis.

Pneumococcal Choline-Binding Proteins Involved in Virulence as Vaccine Candidates

Streptococcus pneumoniae is a pathogen responsible for millions of deaths worldwide. Currently, the available vaccines for the prevention of S. pneumoniae infections are the 23-valent pneumococcal polysaccharide-based vaccine (PPV-23) and the pneumococcal conjugate vaccines (PCV10 and PCV13). These vaccines only cover some pneumococcal serotypes (up to 100 different serotypes have been identified) and are unable to protect against non-vaccine serotypes and non-encapsulated pneumococci. The emergence of antibiotic-resistant non-vaccine serotypes after these vaccines is an increasing threat. Therefore, there is an urgent need to develop new pneumococcal vaccines which could cover a wide range of serotypes. One of the vaccines most characterized as a prophylactic alternative to current PPV-23 or PCVs is a vaccine based on pneumococcal protein antigens. The choline-binding proteins (CBP) are found in all pneumococcal strains, giving them the characteristic to be potential vaccine candidates as they may protect against different serotypes. In this review, we have focused the attention on different CBPs as vaccine candidates because they are involved in the pathogenesis process, confirming their immunogenicity and protection against pneumococcal infection. The review summarizes the major contribution of these proteins to virulence and reinforces the fact that antibodies elicited against many of them may block or interfere with their role in the infection process.

Molecular analyses identifies new domains and structural differences among Streptococcus pneumoniae immune evasion proteins PspC and Hic

The PspC and Hic proteins of Streptococcuspneumoniae are some of the most variable microbial immune evasion proteins identified to date. Due to structural similarities and conserved binding profiles, it was assumed for a long time that these pneumococcal surface proteins represent a protein family comprised of eleven subgroups. Recently, however, the evaluation of more proteins revealed a greater diversity of individual proteins. In contrast to previous assumptions a pattern evaluation of six PspC and five Hic variants, each representing one of the previously defined subgroups, revealed distinct structural and likely functionally regions of the proteins, and identified nine new domains and new domain alternates. Several domains are unique to PspC and Hic variants, while other domains are also present in other virulence factors encoded by pneumococci and other bacterial pathogens. This knowledge improved pattern evaluation at the level of full-length proteins, allowed a sequence comparison at the domain level and identified domains with a modular composition. This novel strategy increased understanding of individual proteins variability and modular domain composition, enabled a structural and functional characterization at the domain level and furthermore revealed substantial structural differences between PspC and Hic proteins. Given the exceptional genomic diversity of the multifunctional PspC and Hic proteins a detailed structural and functional evaluation need to be performed at the strain level. Such knowledge will also be useful for molecular strain typing and characterizing PspC and Hic proteins from new clinical S. pneumoniae strains.

Catalytic and lectin domains in neuraminidase A from Streptococcus pneumoniae are capable of an intermolecular assembly: Implications for biofilm formation

Neuraminidase A from Streptococcus pneumoniae (NanA) is a cell wall-bound modular enzyme containing one lectin and one catalytic domain. Unlike homologous NanB and NanC expressed by the same bacterium, the two domains within one NanA molecule do not form a stable interaction and are spatially separated by a 16-amino acid-long flexible linker. In this work, the ability of NanA to form intermolecular assemblies was characterized using the methods of molecular modeling and bioinformatic analysis based on crystallographic data and by bringing together previously published experimental data. It was concluded that two catalytic domains, as well as one catalytic and one lectin domain, originating from two cell wall-bound NanA molecules, can interact through a previously uncharacterized interdomain interface to form complexes stabilized by a network of intermolecular hydrogen bonds and salt bridges. Supercomputer modeling strongly indicated that artocarpin, an earlier experimentally discovered inhibitor of the pneumococcal biofilm formation, is able to bind to a site located in the catalytic domain of one NanA entity and prevent its interaction with the lectin or catalytic domain of another NanA entity, thus directly precluding the generation of intermolecular assemblies. The revealed structural adaptation is discussed as one plausible mechanism of noncatalytic participation of this potentially key pathogenicity enzyme in pneumococcal biofilm formation.

High Titer of Antibody Against Pneumococcal IgA1 Protease in Healthy Individuals

Background and Objectives:

Considering rising antibiotic resistance in various strains of Streptococcus pneumoniae, there is a need to find new immunogenic candidates for developing pneumococcal vaccines. Immunoglobulin A1 (IgA1) protease is one of the virulence factors playing an important role in the pathogenesis of S. pneumoniae infections. In the present study, we aimed to evaluate the titer of antibody against pneumococcal recombinant IgA1 protease in the serum of healthy humans.

Materials and Methods:

A part of the IgA1 protease gene (705 bp) from S. pneumonia ATCC 49619 was amplified by PCR and then digested using restriction enzymes and ligated by the pET28a expression vector. The recombinant protein was expressed in E. coli BL21 strain. Affinity chromatography was used to purify the protein. The titer of antibody against the recombinant protease was determined in healthy individuals in three age groups of <2, 2-40, and > 40 years using indirect Enzyme-Linked Immunosorbent Assay (ELISA).

Results:

The expression and purification of the IgA1 recombinant protease were successful. The concentration of the purified protein was determined as 1.013 mg/ml using the NanoDrop method. The titer of anti-recombinant IgA1 protease antibody (20, 40, 80 and 160) showed a significant correlation with age (p-value<0.05). According to our results, the antibody titer was desirable, especially in individuals over two years old.

Conclusion:

In the present study, desirable antibody titers against the pneumococcal recombinant IgA1 protease were seen in the three groups’ serum of healthy individuals. However, a significant correlation was not totally observed among groups.

Hemoglobin stimulates vigorous growth of Streptococcus pneumoniae and shapes the pathogen's global transcriptome

Streptococcus pneumoniae (Spn) must acquire iron from the host to establish infection. We examined the impact of hemoglobin, the largest iron reservoir in the body, on pneumococcal physiology. Supplementation with hemoglobin allowed Spn to resume growth in an iron-deplete medium. Pneumococcal growth with hemoglobin was unusually robust, exhibiting a prolonged logarithmic growth, higher biomass, and extended viability in both iron-deplete and standard medium. We observed the hemoglobin-dependent response in multiple serotypes, but not with other host proteins, free iron, or heme. Remarkably, hemoglobin induced a sizable transcriptome remodeling, effecting virulence and metabolism in particular genes facilitating host glycoconjugates use. Accordingly, Spn was more adapted to grow on the human α − 1 acid glycoprotein as a sugar source with hemoglobin. A mutant in the hemoglobin/heme-binding protein Spbhp-37 was impaired for growth on heme and hemoglobin iron. The mutant exhibited reduced growth and iron content when grown in THYB and hemoglobin. In summary, the data show that hemoglobin is highly beneficial for Spn cultivation in vitro and suggest that hemoglobin might drive the pathogen adaptation in vivo. The hemoglobin receptor, Spbhp-37, plays a role in mediating the positive influence of hemoglobin. These novel findings provide intriguing insights into pneumococcal interactions with its obligate human host.

Disruption of Aspergillus fumigatus biofilm by Streptococcus pneumoniae: Mycelial fragmentation by hydrogen peroxide

Biofilm is a complex structure consisting of microorganisms such as bacteria, fungi and an extracellular matrix (ECM). Biofilms are involved in most microbial infections and show persistent resistance to antibiotic treatment and immune response. Both Aspergillus fumigatus and Streptococcus pneumoniae are colonizers that can form biofilms in the respiratory tract. These pathogens have been simultaneously isolated from the same patient, but their interaction is poorly understood. We observed morphological changes in single- and mixed-species biofilms prepared for confocal laser scanning microscopy and scanning electron microscopy (SEM). Pneumococci suppressed the development of a fungal biofilm, and it even disrupted a preformed fungal biofilm. When a preformed fungal biofilm was treated with pneumococci, the mycelial network was fragmented, and only bacteria could develop. SEM revealed that the fragmented mycelium was further disrupted into fine filaments as treatment time progressed, and that the ECM of the preformed fungal biofilm had disappeared. The pneumococcal culture supernatant contained mycelial fragmentation activity that was heat-sensitive. The culture supernatant of a mutant pneumococcal strain deficient in pneumolysin (Δply) also exhibited the mycelial fragmentation activity. Enolase and lactate oxidase, which are involved in glycolysis and hydrogen peroxide production, were identified in the culture supernatant of the Δply mutant. Neither the wild type nor the mutant strain could fragment the mycelium in the presence of catalase. These data suggest that hydrogen peroxide could fragment the mycelium and would terminate the co-existence of A. fumigatus and S. pneumoniae in biofilm.

Genomic and Immunogenic Protein Diversity of Erysipelothrix rhusiopathiae Isolated From Pigs in Great Britain: Implications for Vaccine Protection

Erysipelas, caused by the bacterium Erysipelothrix rhusiopathiae, is re-emerging in swine and poultry production systems worldwide. While the global genomic diversity of this species has been characterized, how much of this genomic and functional diversity is maintained at smaller scales is unclear. Specifically, while several key immunogenic surface proteins have been identified for E. rhusiopathiae, little is known about their presence among field strains and their divergence from vaccines, which could result in vaccine failure. Here, a comparative genomics approach was taken to determine the diversity of E. rhusiopathiae strains in pigs in Great Britain over nearly three decades, as well as to assess the field strains’ divergence from the vaccine strain most commonly used in British pigs. In addition, the presence/absence and variability of 13 previously described immunogenic surface proteins was determined, including SpaA which is considered a key immunogen. We found a high diversity of E. rhusiopathiae strains in British pigs, similar to the situation described in European poultry but in contrast to swine production systems in Asia. Of the four clades of E. rhusiopathiae found globally, three were represented among British pig isolates, with Clade 2 being the most common. All British pig isolates had one amino acid difference in the immunoprotective domain of the SpaA protein compared to the vaccine strain. However, we were able to confirm using in silico structural protein analyses that this difference is unlikely to compromise vaccine protection. Of 12 other known immunogenic surface proteins of E. rhusiopathiae examined, 11 were found to be present in all British pig isolates and the vaccine strain, but with highly variable degrees of conservation at the amino acid sequence level, ranging from 0.3 to 27% variant positions. Moreover, the phylogenetic incongruence of these proteins suggests that horizontal transfer of genes encoding for antigens is commonplace for this bacterium. We hypothesize that the sequence variants in these proteins could be responsible for differences in the efficacy of the immune response. Our results provide the necessary basis for testing this hypothesis through in vitro and in vivo studies.

Role of bacterial Ser/Thr protein kinases spr 1577 in the pathogenesis of respiratory infections caused by S. pneumoniae

This study investigated the specific role played by conserved membrane eukaryotic-like Ser/Thr protein kinases (StkP) during infection, particularly pneumonia, in order to get deep insights about Ser/Thr protein kinases signaling during infection and pathogenesis. The wild type and mutated Ser/Thr protein kinases (Spr1577) strains were tested on different cell lines to understand their virulence based on gentamicin protection assay, gene expression analysis and the expression of various interleukins. Though there was no uptake of bacterial CFU at the beginning, after 24 h it was 50% less for the mutated in comparison to wild-type strain, thus indicating a possible role of Spr1577 gene in the phagosomal survival of S pneumoniae. The complemented, strain-restored bacterial survival to the similar extent alike wild-type strains suggest that the Spr1577 kinase activity is not critical for the intracellular survival of S. pneumoniae within macrophages. Peak expression of spr1577 post infection indicating that the virulent genes seemed persuaded within the macrophages. Higher induction of pro-inflammatory cytokines by the wild type and complemented strains, but not by mutated strain, suggest its role in the induction of macrophages functions. S. pneumoniae and S. pyogenes are closely-related pathogens having 97% similarity in their gene sequences suggesting that the virulence mechanisms greatly varies and remain poorly understood for S. pneumoniae.

Total Synthesis of the Lipid-Anchor-Attached Core Trisaccharides of Lipoteichoic Acids of Streptococcus pneumoniae and Streptococcus oralis Uo5

Herein we report an efficient total synthesis of lipid-anchor-appended core trisaccharides of lipoteichoic acids of Streptococcus pneumoniae and Streptococcus oralis Uo5. The key features include the expedient synthesis of the rare sugar 2,4,6-trideoxy-2-acetamido-4-amino-d-Galp building block via one-pot sequential S_N2 reactions and the α-selective coupling of d-thioglucoside with the diacyl glycerol acceptor to construct a common disaccharide acceptor, which was utilized in the total synthesis of target molecules 1 and 2.

Staphylococcus aureuscapsular polysaccharides: a structural and synthetic perspective

This review surveys known structures of staphylococcal polysaccharides and summarizes all synthetic efforts to obtain these sequences.

Intrinsic and extrinsic factors associated with sputum characteristics of presumed tuberculosis patients

BACKGROUND

Sputum remains the most preferred specimen for detection of Mycobacterium tuberculosis due to its non-invasive method of production. Good quality sputum specimen is essential for accurate diagnosis of pulmonary tuberculosis (PTB). It is therefore imperative to assess factors that are related to the production of sputum that is of the best quality.

OBJECTIVE

We assessed the intrinsic and extrinsic characteristics of presumed tuberculosis patients and the quality of sputum they produced.

METHODS

This was a cross-sectional study in which consenting enrolled presumed tuberculosis patients were subjected to medical examination and a structured questionnaire administered to collect clinical history, demographic information, environmental and behavioral characteristics. The enrolled participants were instructed on how to collect spot and morning sputum specimens for macroscopic and microscopic assessment to determine any association.

RESULTS

A total of 309 patients were enrolled into the study with an even distribution on gender (50.5% males). Of these, 202 (65.3%) submitted both a spot and a morning specimen for analysis. On macroscopic examination, 70% spot and 68% morning sputum were characterized as good quality (Purulent/mucoid). The factors associated (p<0.05) with quality specimen included both intrinsic and extrinsic factors. The intrinsic factors included: difficulty in breathing, presence of conjunctivitis and knowledge of the disease whereas the only extrinsic factor associated with production of good quality sputum for tuberculosis diagnosis was time taken by patient to seek tuberculosis treatment after occurrence of any of the TB symptoms.

CONCLUSION

Both intrinsic and extrinsic factors affected the quality of sputum produced by presumed tuberculosis patients. Clinical and behavioral characteristics including conjunctivitis, difficulty in breathing and delay in seeking treatment were important factors that determined the production of good quality sputum specimens, while knowledge of tuberculosis disease did not compel presumed tuberculosis patients to produce good quality sputum for diagnosis of the disease.

A Pyrrhic Victory: The PMN Response to Ocular Bacterial Infections

Some tissues of the eye are susceptible to damage due to their exposure to the outside environment and inability to regenerate. Immune privilege, although beneficial to the eye in terms of homeostasis and protection, can be harmful when breached or when an aberrant response occurs in the face of challenge. In this review, we highlight the role of the PMN (polymorphonuclear leukocyte) in different bacterial ocular infections that invade the immune privileged eye at the anterior and posterior segments: keratitis, conjunctivitis, uveitis, and endophthalmitis. Interestingly, the PMN response from the host seems to be necessary for pathogen clearance in ocular disease, but the inflammatory response can also be detrimental to vision retention. This "Pyrrhic Victory" scenario is explored in each type of ocular infection, with details on PMN recruitment and response at the site of ocular infection. In addition, we emphasize the differences in PMN responses between each ocular disease and its most common corresponding bacterial pathogen. The in vitro and animal models used to identify PMN responses, such as recruitment, phagocytosis, degranulation, and NETosis, are also outlined in each ocular infection. This detailed study of the ocular acute immune response to infection could provide novel therapeutic strategies for blinding diseases, provide more general information on ocular PMN responses, and reveal areas of bacterial ocular infection research that lack PMN response studies.

Streptococcal phosphotransferase system imports unsaturated hyaluronan disaccharide derived from host extracellular matrices

Certain bacterial species target the polysaccharide glycosaminoglycans (GAGs) of animal extracellular matrices for colonization and/or infection. GAGs such as hyaluronan and chondroitin sulfate consist of repeating disaccharide units of uronate and amino sugar residues, and are depolymerized to unsaturated disaccharides by bacterial extracellular or cell-surface polysaccharide lyase. The disaccharides are degraded and metabolized by cytoplasmic enzymes such as unsaturated glucuronyl hydrolase, isomerase, and reductase. The genes encoding these enzymes are assembled to form a GAG genetic cluster. Here, we demonstrate the Streptococcus agalactiae phosphotransferase system (PTS) for import of unsaturated hyaluronan disaccharide. S. agalactiae NEM316 was found to depolymerize and assimilate hyaluronan, whereas its mutant with a disruption in the PTS genes included in the GAG cluster was unable to grow on hyaluronan, while retaining the ability to depolymerize hyaluronan. Using toluene-treated wild-type cells, the PTS activity for import of unsaturated hyaluronan disaccharide was significantly higher than that observed in the absence of the substrate. In contrast, the PTS mutant was unable to import unsaturated hyaluronan disaccharide, indicating that the corresponding PTS is the only importer of fragmented hyaluronan, which is suitable for PTS to phosphorylate the substrate at the C-6 position. This is distinct from Streptobacillus moniliformis ATP-binding cassette transporter for import of sulfated and non-sulfated fragmented GAGs without substrate modification. The three-dimensional structure of streptococcal EIIA, one of the PTS components, was found to contain a Rossman-fold motif by X-ray crystallization. Docking of EIIA with another component EIIB by modeling provided structural insights into the phosphate transfer mechanism. This study is the first to identify the substrate (unsaturated hyaluronan disaccharide) recognized and imported by the streptococcal PTS. The PTS and ABC transporter for import of GAGs shed light on bacterial clever colonization/infection system targeting various animal polysaccharides.

Protective responses of an engineered PspA recombinant antigen against Streptococcus pneumoniae

•

In this study, two immunogenic antigens based on recombinant PspA proteins were immunized mice.

•

The protective effects of developed anti-PspA antibodies in mice in intranasal and intraperitoneal challenges were proved.

•

Based on the obtained results, immunization with the B-regions of PspA antigens are crucial in protection of challenged mice with S. pneumoniae strains.

Streptococcus pneumoniae is a major pathogen in human respiratory tract which causes significant morbidity and mortality across from the world. Currently available vaccines are not completely effective and cannot cover all pathogenic strains so there is an important need to develop an alternative cost-effective vaccine, based on conserved protein antigens. Pneumococcal surface protein A (PspA) is one of interesting candidates for development of a serotype-independent vaccine against pneumococcal infections. PspA is grouped into two major families with five clades, and broad-reacting PspA-based vaccines should contain at least one functional fragment from each of the two families.

In this study, we developed two immunogenic antigens based on recombinant PspA proteins that including the different antigenic regions of PspA from both two families. The cross-reactivity of antibodies elicited against two PspA proteins PspAB1-5 and PspA₄ABC and their role in complement deposition with three strains of pneumococci were tested. The protective effects of developed anti-PspA antibodies in mice in intranasal and intraperitoneal challenges were evaluated using a strain from clade 2. Sera from immunized mice with PspAB_1-5 in comparison with PspA₄ABC was able to deposit more C3 complement component on surface of pneumococci bearing diverse PspA from both families 1 and 2, and immunized mice with the PspAB_1-5 showed a higher protection than PspA₄ABC in pneumococcal challenges.

The obtained results from this study indicate that a PspA-based antigen composed of B region from all clades in addition to conserved domains, can provide a significant protection against multiple strains of S. pneumoniae and may overcome the limitation of polysaccharide vaccines.

Mycobacterium tuberculosis Primary Infection and Dissemination: A Critical Role for Alveolar Epithelial Cells

Globally, tuberculosis (TB) has reemerged as a major cause of morbidity and mortality, despite the use of the Mycobacterium bovis BCG vaccine and intensive attempts to improve upon BCG or develop new vaccines. Two lacunae in our understanding of the Mycobacterium tuberculosis (M. tb)-host pathogenesis have mitigated the vaccine efforts; the bacterial-host interaction that enables successful establishment of primary infection and the correlates of protection against TB. The vast majority of vaccine efforts are based on the premise that cell-mediated immunity (CMI) is the predominating mode of protection against TB. However, studies in animal models and in humans demonstrate that post-infection, a period of several weeks precedes the initiation of CMI during which the few inhaled bacteria replicate dramatically and disseminate systemically. The “Trojan Horse” mechanism, wherein M. tb is phagocytosed and transported across the alveolar barrier by infected alveolar macrophages has been long postulated as the sole, primary M. tb:host interaction. In the current review, we present evidence from our studies of transcriptional profiles of M. tb in sputum as it emerges from infectious patients where the bacteria are in a quiescent state, to its adaptations in alveolar epithelial cells where the bacteria transform to a highly replicative and invasive phenotype, to its maintenance of the invasive phenotype in whole blood to the downregulation of invasiveness upon infection of epithelial cells at an extrapulmonary site. Evidence for this alternative mode of infection and dissemination during primary infection is supported by in vivo, in vitro cell-based, and transcriptional studies from multiple investigators in recent years. The proposed alternative mechanism of primary infection and dissemination across the alveolar barrier parallels our understanding of infection and dissemination of other Gram-positive pathogens across their relevant mucosal barriers in that barrier-specific adhesins, toxins, and enzymes synergize to facilitate systemic establishment of infection prior to the emergence of CMI. Further exploration of this M. tb:non-phagocytic cell interaction can provide alternative approaches to vaccine design to prevent infection with M. tb and not only decrease clinical disease but also decrease the overwhelming reservoir of latent TB infection.

First-In-Class Inhibitors Targeting the Interaction between Bacterial RNA Polymerase and Sigma Initiation Factor Affect the Viability and Toxin Release of Streptococcus pneumoniae

Novel antimicrobial classes are in desperate need for clinical management of infections caused by increasingly prevalent multi-drug resistant pathogens. The protein-protein interaction between bacterial RNA polymerase (RNAP) and the housekeeping sigma initiation factor is essential to transcription and bacterial viability. It also presents a potential target for antimicrobial discovery, for which a hit compound (C3) was previously identified from a pharmacophore model-based in silico screen. In this study, the hit compound was experimentally assessed with some rationally designed derivatives for the antimicrobial activities, in particular against Streptococcus pneumoniae and other pathogens. One compound, C3-005, shows dramatically improved activity against pneumococci compared to C3. C3-005 also attenuates S. pneumoniae toxin production more strongly than existing classes of antibiotics tested. Here we demonstrate a newly validated antimicrobial agent to address an overlooked target in the hit-to-lead process, which may pave the way for further antimicrobial development.

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.

Serotype-Independent Protection Against Invasive Pneumococcal Infections Conferred by Live Vaccine With lgt Deletion

Streptococcus pneumoniae is the most common respiratory bacterial pathogen among cases of community-acquired infection in young children, older adults, and individuals with underlying medical conditions. Although capsular polysaccharide-based pneumococcal vaccines have contributed to significant decrease in invasive pneumococcal infections, these vaccines have some limitations, including limited serotype coverage, lack of effective mucosal antibody responses, and high costs. In this study, we investigated the safety and immunogenicity of a live, whole-cell pneumococcal vaccine constructed by deleting the gene for prolipoprotein diacylglyceryl transferase (lgt) from the encapsulated pneumococcal strain TIGR4 (TIGR4Δlgt) for protection against heterologous pneumococcal strains. Pneumococcal strain TIGR4 was successfully attenuated by deletion of lgt, resulting in the loss of inflammatory activity and virulence. TIGR4Δlgt colonized the nasopharynx long enough to induce strong mucosal IgA and IgG2b-dominant systemic antibody responses that were cross-reactive to heterologous pneumococcal serotypes. Finally, intranasal immunization with TIGR4Δlgt provided serotype-independent protection against pneumococcal challenge in mice. Taken together, our results suggest that TIGR4Δlgt is an avirulent and attractive broad-spectrum pneumococcal vaccine candidate. More broadly, we assert that modulation of such "master" metabolic genes represents an emerging strategy for developing more effective vaccines against numerous infectious agents.

Streptococcus pneumoniae: Invasion and Inflammation

Streptococcus pneumoniae (the pneumoccus) is the leading cause of otitis media, community-acquired pneumonia, and bacterial meningitis. The success of the pneumococcus stems from its ability to persist in the population as a commensal and avoid killing by immune system. This chapter first reviews the molecular mechanisms that allow the pneumococcus to colonize and spread from one anatomical site to the next. Then, it discusses the mechanisms of inflammation and cytotoxicity during emerging and classical pneumococcal infections.

Bacterial sialoglycosidases in Virulence and Pathogenesis

Human oral microbiome and dysbiotic infections have been recently evidently identified. One of the major reasons for such dysbiosis is impairment of the immune system. Periodontitis is a chronic inflammatory disease affecting the tissues that surround and support the teeth. In the United States., approximately 65 million people are affected by this condition. Its occurrence is also associated with many important systemic diseases such as cardiovascular disease, rheumatoid arthritis, and Alzheimer’s disease. Among the most important etiologies of periodontitis is Porphyromonas gingivalis, a keystone bacterial pathogen. Keystone pathogens can orchestrate inflammatory disease by remodeling a normally benign microbiota causing imbalance between normal and pathogenic microbiota (dysbiosis). The important characteristics of P. gingivalis causing dysbiosis are its virulence factors which cause effective subversion of host defenses to its advantage allowing other pathogens to grow. Some of the mechanisms involved in these processes are still not well-understood. However, various microbial strategies target host sialoglycoproteins for immune dysregulation. In addition, the enzymes that break down sialoglycoproteins and sialoglycans are the “sialoglycoproteases”, resulting in exposed terminal sialic acid. This process could lead to pathogen-toll like receptor (TLR) interactions mediated through sialic acid receptor ligand mechanisms. Assessing the function of P. gingivalis sialoglycoproteases, could pave the way to designing carbohydrate analogues and sialic acid mimetics to serve as drug targets.

Differential Expression of Antimicrobial Peptides in Streptococcus pneumoniae Keratitis and STAT3-Dependent Expression of LL-37 by Streptococcus pneumoniae in Human Corneal Epithelial Cells

Streptococcus pneumoniae is the leading cause of bacterial keratitis in the developing world with a growing trend of acquiring resistance against various antibiotics. In the current study, we determined the expression of different antimicrobial peptides (AMPs) in response to S. pneumoniae in patients, as well as in primary and immortalized human corneal epithelial cells. We further focused on LL-37 and determined its expression in human cornea infected with S. pneumoniae and studied the killing ability of LL-37 against S. pneumoniae. The expression of AMPs was determined by quantitative PCR and the phosphorylation of signaling proteins was evaluated by immunoblot analysis. LL-37 expression was also determined by immunofluorescence and Western blot method and the killing ability of LL-37 against S. pneumoniae was determined by colony-forming units. Differential expression of antimicrobial peptides was observed in patients with S. pneumoniae keratitis. Although S. pneumoniae induced expression of the AMPs in human corneal epithelial cells (HCEC), it did not induce AMP expression in U937, a human monocyte cell line. S. pneumoniae also caused activation of nuclear factor kappa-light-chain enhancer of activated B cells (NF-κB)and mitogen activated protein kinase (MAPK) pathways in corneal epithelial cells. LL-37 was found to be effective against both laboratory and clinical strains of S. pneumoniae. LL-37 induction by S. pneumoniae in human corneal epithelial cells was mediated by signal transducer and activator of transcription 3 (STAT3) activation, and inhibition of STAT3 activation significantly reduced LL-37 expression. Our study determines an extensive profile of AMPs expressed in the human cornea during S. pneumoniae infection, and suggests the potential of LL-37 to be developed as an alternative therapeutic intervention to fight increasing antibiotic resistance among bacteria.

Comparative studies of catalytic pathways for Streptococcus pneumoniae sialidases NanA, NanB and NanC

Streptococcus pneumoniae (S. pneumoniae) is a leading human pathogen, which takes large responsibility for severe otitis media, acute meningitis and septicaemia. It encodes up to three distinct sialidases: NanA, NanB and NanC, which are promising drug targets. Recent experimental studies have shown that these three sialidases might work together up to the ultimate step, where NanA and NanB produce N-acetylneuraminic acid (Neu5Ac) and 2,7-anhydro-Neu5Ac following the functions of sialidase and intramolecular trans-sialidase, whilst NanC carries on a ping-pong mechanism that produces or removes 2-deoxy-2,3-didehydro-Neu5AC. It is intriguing that these sialidases have similar active sites but operate via three distinct reaction pathways. To clarify this issue, herein we present the first systematic computational investigation on the catalytic pathways for S. pneumoniae NanA, NanB and NanC based on combined quantum mechanics/molecular mechanics simulations, and propose the most preferred routes for the three S. pneumoniae sialidases. Our findings support the mechanisms of NanA and NanC that were proposed by previous experimental studies, whereas the role of water in NanB was found to differ slightly from our current understandings. The mechanistic insights obtained from this work are expected to assist in the design of potent inhibitors targeting these key enzymes for therapeutic applications.