The host transcriptional response to superinfection by influenza A virus and Streptococcus pneumoniae.

Secondary bacterial challenges during influenza virus infection "superinfection") cause excessive mortality and hospitalization. Here, we present a longitudinal study of bulk gene expression changes in murine lungs during superinfection, with an initial influenza A virus infection and a subsequent Streptococcus pneumoniae infection. In addition to the well-characterized impairment of the host response, we identified superinfection-specific alterations in the global transcriptional program that are linked to the host's ability to resist the pathogens. Particularly, whereas superinfected mice manifested an excessive rapid induction of the resistance-to-infection program, there was a substantial tissue-level rewiring of this program: upon superinfection, interferon-regulated genes were switched from positive to negative correlations with the host's resistance state, whereas genes of fatty acid metabolism switched from negative to positive correlations with resistance states. Thus, the transcriptional resistance state in superinfection is reprogrammed toward repressed interferon signaling and induced fatty acid metabolism. Our findings suggest new insights into a tissue-level remodeling of the host defense upon superinfection, providing promising targets for future therapeutic interventions. IMPORTANCE: Secondary bacterial infections are the most frequent complications during influenza A virus (IAV) pandemic outbreaks, contributing to excessive morbidity and mortality in the human population. Most IAV-related deaths are attributed to Streptococcus pneumoniae (SP) infections, which usually begin within the first week of IAV infection in the respiratory tracts. Here, we focused on longitudinal transcriptional responses during a superinfection model consisting of an SP infection that follows an initial IAV infection, comparing superinfection to an IAV-only infection, an SP-only infection, and control treatments. Our longitudinal data allowed a fine analysis of gene expression changes during superinfection. For instance, we found that superinfected mice exhibited rapid gene expression induction or reduction within the first 12 h after encountering the second pathogen. Cell proliferation and immune response activation processes were upregulated, while endothelial processes, vasculogenesis, and angiogenesis were downregulated, providing promising targets for future therapeutic interventions. We further analyzed the longitudinal transcriptional responses in the context of a previously defined spectrum of the host's resistance state, revealing superinfection-specific reprogramming of resistance states, such as reprogramming of fatty acid metabolism and interferon signaling. The reprogrammed functions are compelling new targets for switching the pathogenic superinfection state into a single-infection state.

In Silico Identification and Characterization of Drug Targets in Streptococcus pneumoniae ATCC 700669 (Serotype 23F) by Subtractive Genomics.

Streptococcus pneumoniae (S. pneumoniae) is an important pathogen worldwide that causes pneumococcal infections which are related to high rates of morbidity and mortality especially in young children, older adults, and immune-compromised persons. Antibiotic resistance in S. pneumoniae is a serious problem across the world from time to time, resulting in treatment failure and diminished value of older medicines. Therefore, the objective of this study was to identify new putative drug targets against S. pneumoniae serotype 23F by using subtractive genomics. By using bioinformatics tools such as NCBI, UniProt KB, PDB, KEGG, DEG, PSORTb, CD hit, DrugBank database, and other softwares, proteins involved in unique metabolic pathways of S. pneumoniae serotype 23F were studied. The result indicates that this serotype consists of 97 metabolic pathways of which 74 are common with that of human, and 23 pathways are unique to the serotype 23F. After investigation and analysis of essentiality, nonhomology, subcellular localization, having drug targets, and enzymatic activity, four proteins were prioritized as druggable targets. These druggable proteins include UDP-N-acetylglucosamine 1-carboxyvinyltransferase, UDP-N-acetyl muramate dehydrogenase, D-alanine-D-alanine ligase, and alanine racemase that are found in S. pneumoniae serotype 23F. All these four proteins are essential, are nonhomologous with human proteins, have drug targets, and are located in cell cytoplasm. Therefore, the authors recommend these proteins to be used for efficient drug design against S. pneumoniae serotype 23F after experimental validation for essentiality and druggability.

Regulation of inflammation and protection against invasive pneumococcal infection by the long pentraxin PTX3.

Streptococcus pneumoniae is a major pathogen in children, elderly subjects, and immunodeficient patients. Pentraxin 3 (PTX3) is a fluid-phase pattern recognition molecule (PRM) involved in resistance to selected microbial agents and in regulation of inflammation. The present study was designed to assess the role of PTX3 in invasive pneumococcal infection. In a murine model of invasive pneumococcal infection, PTX3 was strongly induced in non-hematopoietic (particularly, endothelial) cells. The IL-1ß/MyD88 axis played a major role in regulation of the Ptx3 gene expression. Ptx3-/- mice presented more severe invasive pneumococcal infection. Although high concentrations of PTX3 had opsonic activity in vitro, no evidence of PTX3-enhanced phagocytosis was obtained in vivo. In contrast, Ptx3-deficient mice showed enhanced recruitment of neutrophils and inflammation. Using P-selectin-deficient mice, we found that protection against pneumococcus was dependent upon PTX3-mediated regulation of neutrophil inflammation. In humans, PTX3 gene polymorphisms were associated with invasive pneumococcal infections. Thus, this fluid-phase PRM plays an important role in tuning inflammation and resistance against invasive pneumococcal infection.

Characterization of the innate immune response to Streptococcus pneumoniae infection in zebrafish.

Streptococcus pneumoniae (pneumococcus) is one of the most frequent causes of pneumonia, sepsis and meningitis in humans, and an important cause of mortality among children and the elderly. We have previously reported the suitability of the zebrafish (Danio rerio) larval model for the study of the host-pathogen interactions in pneumococcal infection. In the present study, we characterized the zebrafish innate immune response to pneumococcus in detail through a whole-genome level transcriptome analysis and revealed a well-conserved response to this human pathogen in challenged larvae. In addition, to gain understanding of the genetic factors associated with the increased risk for severe pneumococcal infection in humans, we carried out a medium-scale forward genetic screen in zebrafish. In the screen, we identified a mutant fish line which showed compromised resistance to pneumococcus in the septic larval infection model. The transcriptome analysis of the mutant zebrafish larvae revealed deficient expression of a gene homologous for human C-reactive protein (CRP). Furthermore, knockout of one of the six zebrafish crp genes by CRISPR-Cas9 mutagenesis predisposed zebrafish larvae to a more severe pneumococcal infection, and the phenotype was further augmented by concomitant knockdown of a gene for another Crp isoform. This suggests a conserved function of C-reactive protein in anti-pneumococcal immunity in zebrafish. Altogether, this study highlights the similarity of the host response to pneumococcus in zebrafish and humans, gives evidence of the conserved role of C-reactive protein in the defense against pneumococcus, and suggests novel host genes associated with pneumococcal infection.

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 ß-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.

Pneumococcal genetic variability in age-dependent bacterial carriage.

The characteristics of pneumococcal carriage vary between infants and adults. Host immune factors have been shown to contribute to these age-specific differences, but the role of pathogen sequence variation is currently less well-known. Identification of age-associated pathogen genetic factors could leadto improved vaccine formulations. We therefore performed genome sequencing in a large carriage cohort of children and adults and combined this with data from an existing age-stratified carriage study. We compiled a dictionary of pathogen genetic variation, including serotype, strain, sequence elements, single-nucleotide polymorphisms (SNPs), and clusters of orthologous genes (COGs) for each cohort - all of which were used in a genome-wide association with host age. Age-dependent colonization showed weak evidence of being heritable in the first cohort (h2 = 0.10, 95% CI 0.00-0.69) and stronger evidence in the second cohort (h2 = 0.56, 95% CI 0.23-0.87). We found that serotypes and genetic background (strain) explained a proportion of the heritability in the first cohort (h2serotype = 0.07, 95% CI 0.04-0.14 and h2GPSC = 0.06, 95% CI 0.03-0.13) and the second cohort (h2serotype = 0.11, 95% CI 0.05-0.21 and h2GPSC = 0.20, 95% CI 0.12-0.31). In a meta-analysis of these cohorts, we found one candidate association (p=1.2 × 10-9) upstream of an accessory Sec-dependent serine-rich glycoprotein adhesin. Overall, while we did find a small effect of pathogen genome variation on pneumococcal carriage between child and adult hosts, this was variable between populations and does not appear to be caused by strong effects of individual genes. This supports proposals for adaptive future vaccination strategies that are primarily targeted at dominant circulating serotypes and tailored to the composition of the pathogen populations.

The Roles of Transient Receptor Potential Vanilloid 1 and 4 in Pneumococcal Nasal Colonization and Subsequent Development of Invasive Disease.

Transient receptor potential (TRP) channels, neuronal stimulations widely known to be associated with thermal responses, pain induction, and osmoregulation, have been shown in recent studies to have underlying mechanisms associated with inflammatory responses. The role of TRP channels on inflammatory milieu during bacterial infections has been widely demonstrated. It may vary among types of channels/pathogens, however, and it is not known how TRP channels function during pneumococcal infections. Streptococcus pneumoniae can cause severe infections such as pneumonia, bacteremia, and meningitis, with systemic inflammatory responses. This study examines the role of TRP channels (TRPV1 and TRPV4) for pneumococcal nasal colonization and subsequent development of invasive pneumococcal disease in a mouse model. Both TRPV1 and TRPV4 channels were shown to be related to regulation of the development of pneumococcal diseases. In particular, the influx of neutrophils (polymorphonuclear cells) in the nasal cavity and the bactericidal activity were significantly suppressed among TRPV4 knockout mice. This may lead to severe pneumococcal pneumonia, resulting in dissemination of the bacteria to various organs and causing high mortality during influenza virus coinfection. Regulating host immune responses by TRP channels could be a novel strategy against pathogenic microorganisms causing strong local/systemic inflammation.

Influence of miRNA-30a-5p on Pulmonary Fibrosis in Mice with Streptococcus pneumoniae Infection through Regulation of Autophagy by Beclin-1.

The study is aimed at observing the influence of microribonucleic acid- (miRNA-) 30a-50p on the pulmonary fibrosis in mice with Streptococcus pneumoniae infection through the regulation of autophagy by Beclin-1. Specific pathogen-free mice were instilled with Streptococcus pneumoniae through the trachea to establish the pulmonary fibrosis model. Then, they were divided into the miRNA-30a-50p mimics group (mimics group, n = 10) and miRNA-30a-5p inhibitors group (inhibitors group, n = 10), with the control group (n = 10) also set. Pulmonary tissue wet weight/dry weight (W/D) was detected. The content of tumor necrosis factor-α (TNF-α), interleukin- (IL-) 6, and myeloperoxidase (MPO) was determined using enzyme-linked immunosorbent assay (ELISA). Besides, the changes in the pulmonary function index dynamic lung compliance (Cdyn), plateau pressure (Pplat), and peak airway pressure (Ppeak) were monitored, and the gene and protein expression levels were measured via quantitative PCR (qPCR) and Western blotting. The expression level of miRNA-30a-5p was substantially raised in the mimics group (p < 0.05), but extremely low in the inhibitors group (p < 0.05). The mimics group had obviously raised levels of serum aminotransferase (AST), glutamic-pyruvic transaminase (GPT), alkaline phosphatase (ALP), and pulmonary tissue W/D (p < 0.05). Additionally, the expression levels of TNF-α, IL-6, and MPO were notably elevated in the mimics group, while their expression levels showed the opposite conditions in the inhibitors group (p < 0.05). According to the HE staining results, the inhibitors group had arranged orderly cells, while the mimics group exhibited lung injury, pulmonary edema, severe inflammatory response, and alveolar congestion. In the inhibitors group, Cdyn was remarkably elevated, but Pplat and Ppeak declined considerably (p < 0.05). Besides, the inhibitors group exhibited elevated messenger RNA (mRNA) levels of Beclin-1 and LC3, lowered mRNA levels of α-SMA and p62, a raised protein level of Beclin-1, and a markedly decreased protein level of p62 (p < 0.05). Silencing miRNA-30a-5p expression can promote the expression of Beclin-1 to accelerate the occurrence of autophagy, thereby treating pulmonary fibrosis in mice with Streptococcus pneumoniae infection.

The circulatory small non-coding RNA landscape in community-acquired pneumonia on intensive care unit admission.

Community-acquired pneumonia (CAP) is a major cause of sepsis. Despite several clinical trials targeting components of the inflammatory response, no specific treatment other than antimicrobial therapy has been approved. This argued for a deeper understanding of sepsis immunopathology, in particular factors that can modulate the host response. Small non-coding RNA, for example, micro (mi)RNA, have been established as important modifiers of cellular phenotypes. Notably, miRNAs are not exclusive to the intracellular milieu but have also been detected extracellular in the circulation with functional consequences. Here, we sought to determine shifts in circulatory small RNA levels of critically ill patients with CAP-associated sepsis and to determine the influence of clinical severity and causal pathogens on small RNA levels. Blood plasma was collected from 13 critically ill patients with sepsis caused by CAP on intensive care unit admission and from 5 non-infectious control participants. Plasma small RNA-sequencing identified significantly altered levels of primarily mature miRNAs in CAP relative to controls. Pathways analysis of high or low abundance miRNA identified various over-represented cellular biological pathways. Analysis of small RNA levels against common clinical severity and inflammatory parameters indices showed direct and indirect correlations. Additionally, variance of plasma small RNA levels in CAP patients may be explained, at least in part, by differences in causal pathogens. Small nuclear RNA levels were specifically altered in CAP due to Influenza infection in contrast to Streptococcus pneumoniae infection. Pathway analysis of plasma miRNA signatures unique to Influenza or Streptococcus pneumoniae infections showed enrichment for specific proteoglycan, cell cycle, and immunometabolic pathways.

Genome-wide proximity between RNA polymerase and DNA topoisomerase I supports transcription in Streptococcus pneumoniae.

Streptococcus pneumoniae is a major cause of disease and death that develops resistance to multiple antibiotics. DNA topoisomerase I (TopoI) is a novel pneumococcal drug target. TopoI is the sole type-I pneumococcal topoisomerase that regulates supercoiling homeostasis in this bacterium. In this study, a direct in vitro interaction between TopoI and RNA polymerase (RNAP) was detected by surface plasmon resonance. To understand the interplay between transcription and supercoiling regulation in vivo, genome-wide association of RNAP and TopoI was studied by ChIP-Seq. RNAP and TopoI were enriched at the promoters of 435 and 356 genes, respectively. Higher levels of expression were consistently measured in those genes whose promoters recruit both RNAP and TopoI, in contrast with those enriched in only one of them. Both enzymes occupied a narrow region close to the ATG codon. In addition, RNAP displayed a regular distribution throughout the coding regions. Likewise, the summits of peaks called with MACS tool, mapped around the ATG codon in both cases. However, RNAP showed a broader distribution towards ATG-downstream positions. Remarkably, inhibition of RNAP with rifampicin prevented the localization of TopoI at promoters and, vice versa, inhibition of TopoI with seconeolitsine prevented the binding of RNAP to promoters. This indicates a functional interplay between RNAP and TopoI. To determine the molecular factors responsible for RNAP and TopoI co-recruitment, we looked for DNA sequence motifs. We identified a motif corresponding to a -10-extended promoter for TopoI and for RNAP. Furthermore, RNAP was preferentially recruited to genes co-directionally oriented with replication, while TopoI was more abundant in head-on genes. TopoI was located in the intergenic regions of divergent genes pairs, near the promoter of the head-on gene of the pair. These results suggest a role for TopoI in the formation/stability of the RNAP-DNA complex at the promoter and during transcript elongation.

RNA thermosensors facilitate Streptococcus pneumoniae and Haemophilus influenzae immune evasion.

Bacterial meningitis is a major cause of death and disability in children worldwide. Two human restricted respiratory pathogens, Streptococcus pneumoniae and Haemophilus influenzae, are the major causative agents of bacterial meningitis, attributing to 200,000 deaths annually. These pathogens are often part of the nasopharyngeal microflora of healthy carriers. However, what factors elicit them to disseminate and cause invasive diseases, remain unknown. Elevated temperature and fever are hallmarks of inflammation triggered by infections and can act as warning signals to pathogens. Here, we investigate whether these respiratory pathogens can sense environmental temperature to evade host complement-mediated killing. We show that productions of two vital virulence factors and vaccine components, the polysaccharide capsules and factor H binding proteins, are temperature dependent, thus influencing serum/opsonophagocytic killing of the bacteria. We identify and characterise four novel RNA thermosensors in S. pneumoniae and H. influenzae, responsible for capsular biosynthesis and production of factor H binding proteins. Our data suggest that these bacteria might have independently co-evolved thermosensing abilities with different RNA sequences but distinct secondary structures to evade the immune system.

Gab2 (Grb2-Associated Binder2) Plays a Crucial Role in Inflammatory Signaling and Endothelial Dysfunction.

[Figure: see text].

Clonal lineages and antimicrobial resistance of nonencapsulated Streptococcus pneumoniae in the post-pneumococcal conjugate vaccine era in Japan.

OBJECTIVES: The emergence and spread of nonencapsulated Streptococcus pneumoniae (NESp) is a public health concern in the post-pneumococcal conjugate vaccine era. We analyzed the prevalence, molecular characteristics, and antimicrobial resistance of NESp responsible for noninvasive infections in northern Japan. METHODS: NESp isolates were identified using molecular and phenotypical methods among 4463 S. pneumoniae isolates from noninvasive infection cases during 4 study periods between January 2011 and January 2019. NESp isolates were analyzed for antimicrobial susceptibility, genotype, and virulence-associated genes. RESULTS: Seventy-one NESp isolates were identified (1.6% of total clinical isolates) and assigned to the null capsule clade (NCC)1 (pspK+) (94.4%) or NCC2 (aliC+/aliD+) (5.6%). The dominant sequence types (STs) were ST7502 (23.9%), ST4845 (19.7%), ST16214 (11.3%), ST11379 (9.9%), and ST7786 (7.0%). These 5 dominant STs and all 7 novel STs were related to the sporadic NESp lineage ST1106 or PMEN clone Denmark14-ST230. High non-susceptibility rates of NESp were observed for trimethoprim-sulfamethoxazole, erythromycin, and tetracycline (>92.9%), and multidrug resistance was observed in 88.7% of the NESp isolates, including all ST7502, ST4845, and ST11379 isolates. CONCLUSIONS: The study revealed that the dominant clonal groups of NESp were associated with a high prevalence of non-susceptibility to antimicrobials in northern Japan.

The histone demethylase KDM6B fine-tunes the host response to Streptococcus pneumoniae.

Streptococcus pneumoniae is a natural colonizer of the human respiratory tract and an opportunistic pathogen. Although epithelial cells are among the first to encounter pneumococci, the cellular processes and contribution of epithelial cells to the host response are poorly understood. Here, we show that a S. pneumoniae serotype 6B ST90 strain, which does not cause disease in a murine infection model, induces a unique NF-κB signature response distinct from an invasive-disease-causing isolate of serotype 4 (TIGR4). This signature is characterized by activation of p65 and requires a histone demethylase KDM6B. We show, molecularly, that the interaction of the 6B strain with epithelial cells leads to chromatin remodelling within the IL-11 promoter in a KDM6B-dependent manner, where KDM6B specifically demethylates histone H3 lysine 27 dimethyl. Remodelling of the IL-11 locus facilitates p65 access to three NF-κB sites that are otherwise inaccessible when stimulated by IL-1ß or TIGR4. Finally, we demonstrate through chemical inhibition of KDM6B with GSK-J4 inhibitor and through exogenous addition of IL-11 that the host responses to the 6B ST90 and TIGR4 strains can be interchanged both in vitro and in a murine model of infection in vivo. Our studies therefore reveal how a chromatin modifier governs cellular responses during infection.

Case Report: Analysis of Preserved Umbilical Cord Clarified X-Linked Anhidrotic Ectodermal Dysplasia With Immunodeficiency in Deceased, Undiagnosed Uncles.

Family history is one key in diagnosing inborn errors of immunity (IEI); however, disease status is difficult to determine in deceased relatives. X-linked anhidrotic ectodermal dysplasia with immunodeficiency is one of the hyper IgM syndromes that is caused by a hypomorphic variant in the nuclear factor kappa beta essential modulator. We identified a novel IKBKG variant in a 7-month-old boy with pneumococcal rib osteomyelitis and later found that his mother has incontinentia pigmenti. Genetic analysis of preserved umbilical cords revealed the same variant in two of his deceased maternal uncles. Analysis of preserved umbilical cord tissue from deceased relatives can provide important information for diagnosing IEI in their descendants.

FUT2-ABO epistasis increases the risk of early childhood asthma and Streptococcus pneumoniae respiratory illnesses.

Asthma with severe exacerbation is the most common cause of hospitalization among young children. We aim to increase the understanding of this clinically important disease entity through a genome-wide association study. The discovery analysis comprises 2866 children experiencing severe asthma exacerbation between ages 2 and 6 years, and 65,415 non-asthmatic controls, and we replicate findings in 918 children from the Copenhagen Prospective Studies on Asthma in Childhood (COPSAC) birth cohorts. We identify rs281379 near FUT2/MAMSTR on chromosome 19 as a novel risk locus (OR = 1.18 (95% CI = 1.11-1.25), Pdiscovery = 2.6 × 10-9) as well as a biologically plausible interaction between functional variants in FUT2 and ABO. We further discover and replicate a potential causal mechanism behind this interaction related to S. pneumoniae respiratory illnesses. These results suggest a novel mechanism of early childhood asthma and demonstrates the importance of phenotype-specificity for discovery of asthma genes and epistasis.

An in vivo atlas of host-pathogen transcriptomes during Streptococcus pneumoniae colonization and disease.

Streptococcus pneumoniae (Spn) colonizes the nasopharynx and can cause pneumonia. From the lungs it spreads to the bloodstream and causes organ damage. We characterized the in vivo Spn and mouse transcriptomes within the nasopharynx, lungs, blood, heart, and kidneys using three Spn strains. We identified Spn genes highly expressed at all anatomical sites and in an organ-specific manner; highly expressed genes were shown to have vital roles with knockout mutants. The in vivo bacterial transcriptome during colonization/disease was distinct from previously reported in vitro transcriptomes. Distinct Spn and host gene-expression profiles were observed during colonization and disease states, revealing specific genes/operons whereby Spn adapts to and influences host sites in vivo. We identified and experimentally verified host-defense pathways induced by Spn during invasive disease, including proinflammatory responses and the interferon response. These results shed light on the pathogenesis of Spn and identify therapeutic targets.

Within-host microevolution of Streptococcus pneumoniae is rapid and adaptive during natural colonisation.

Genomic evolution, transmission and pathogenesis of Streptococcus pneumoniae, an opportunistic human-adapted pathogen, is driven principally by nasopharyngeal carriage. However, little is known about genomic changes during natural colonisation. Here, we use whole-genome sequencing to investigate within-host microevolution of naturally carried pneumococci in ninety-eight infants intensively sampled sequentially from birth until twelve months in a high-carriage African setting. We show that neutral evolution and nucleotide substitution rates up to forty-fold faster than observed over longer timescales in S. pneumoniae and other bacteria drives high within-host pneumococcal genetic diversity. Highly divergent co-existing strain variants emerge during colonisation episodes through real-time intra-host homologous recombination while the rest are co-transmitted or acquired independently during multiple colonisation episodes. Genic and intergenic parallel evolution occur particularly in antibiotic resistance, immune evasion and epithelial adhesion genes. Our findings suggest that within-host microevolution is rapid and adaptive during natural colonisation.

Antibiotic Resistance Is Associated with Integrative and Conjugative Elements and Genomic Islands in Naturally Circulating Streptococcus pneumoniae Isolates from Adults in Liverpool, UK.

Pneumonia is the sixth largest cause of death in the UK. It is usually caused by Streptococcus pneumoniae, which healthy individuals can carry in their nose without symptoms of disease. Antimicrobial resistance further increases mortality and morbidity associated with pneumococcal infection, although few studies have analysed resistance in naturally circulating pneumococcal isolates in adult populations. Here, we report on the resistome and associated mobile genetic elements within circulating pneumococcus isolated from adult volunteers enrolled in the experimental human pneumococcal colonisation (EHPC) research program at the Liverpool School of Tropical Medicine, UK. Pneumococcal isolates collected from 30 healthy asymptomatic adults who had volunteered to take part in clinical research were screened for antibiotic susceptibility to erythromycin and tetracycline, and whole-genome sequenced. The genetic context of resistance to one or both antibiotics in four isolates was characterised bioinformatically, and any association of the resistance genes with mobile genetic elements was determined. Tetracycline and macrolide resistance genes [tet(M), erm(B), mef(A), msr(D)] were detected on known Tn916-like integrative and conjugative elements, namely Tn6002 and Tn2010, and tet(32) was found for the first time in S. pneumoniae located on a novel 50 kb genomic island. The widespread use of pneumococcal conjugate vaccines impacts on serotype prevalence and transmission within the community. It is therefore important to continue to monitor antimicrobial resistance (AMR) genes present in both vaccine types and non-vaccine types in response to contemporary antimicrobial therapies and characterise the genetic context of acquired resistance genes to continually optimise antibiotic therapies.