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Vaccines are powerful agents in infectious disease prevention but often designed to protect against some strains that are most likely to spread and cause diseases. Most vaccines do not succeed in eradicating the pathogen and thus allow the potential emergence of vaccine evading strains. As with most evolutionary processes, being able to capture all variations across the entire genome gives us the best chance of monitoring and understanding the processes of vaccine evasion. Genomics is being widely adopted as the optimum approach for pathogen surveillance with the potential for early and precise identification of high-risk strains. Given sufficient longitudinal data, genomics also has the potential to forecast the emergence of such strains enabling immediate or pre-emptive intervention. In this review, we consider the strengths and challenges for pathogen genomic surveillance using the experience of the Global Pneumococcal Sequencing (GPS) project as an early example. We highlight the multifaceted nature of genome data and recent advances in genome-based tools to extract useful information relevant to inform vaccine strategies and treatment options. We conclude with future perspectives for genomic pathogen surveillance.

Streptococcus pneumoniae (pneumococcus) is a major pathogen globally, responsible for an estimated one million deaths annually and contributing significantly to the global burden of antimicrobial resistance. Ongoing surveillance of its vaccine antigen (i.e. serotypes), antimicrobial resistance, and pneumococcal lineages is crucial for assessing the impact of vaccination programs and guiding future vaccine design. However, current bioinformatics tools have several limitations that prevent them from enabling comprehensive analysis that allows simultaneous, large-scale, and independent generation of these crucial data. Here, we present the GPS Pipeline that enables reliable extraction of public health information from pneumococcal genomes using in silico methods. It can accurately identify 102 of 107 known serotypes, recognise 1053 pneumococcal lineages, and predict susceptibilities to 19 common antibiotics. Built on Nextflow and utilising containerisation technology, the GPS Pipeline minimises software setup requirements and bioinformatics expertise while facilitating large-scale analysis of genomic data. The GPS Pipeline was applied and validated on 20,924 pneumococcal genomes worldwide, demonstrating its effectiveness in enhancing responsiveness in pneumococcal genomic surveillance. The GPS Pipeline enables accessible and scalable genomic surveillance of Streptococcus pneumoniae. It performs quality control and in silico typing of sequencing reads with high accuracy using a single simple command, without requiring the internet.

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. Streptococcus pneumoniae is an opportunistic pathogen and asymptomatic colonization is a precursor for invasive disease. Here the authors show rapid within-host evolution of naturally acquired pneumococci in ninety-eight infants driven by high nucleotide substitution rates and intra-host homologous recombination.

Streptococcus pneumoniae adapts within hosts through genetic variation and genome plasticity, facilitating persistence under antibiotic and immune pressures. Here, we investigated a prolonged pneumococcal carriage episode (>337 days) in a healthy, HIV-uninfected adult in Malawi. Whole-genome sequencing of single-colony isolates and plate sweep samples confirmed persistent colonisation by a multidrug-resistant serotype 3 strain with a distinct sequence type (GPSC10-ST18362), which maintained stable predominance despite transient acquisition of other serotypes. The sequentially sampled isolates showed 2 to 11 single-nucleotide polymorphism differences, no evidence of recombination, and modest gene loss involving mobile genetic elements. The total genome size decreased from 2.06 Mb to 2.03 Mb across isolates. Intrahost single-nucleotide variants were identified in genes related to metabolism, stress response, and DNA repair, but showed no consistent signatures of positive selection. Capsular locus analysis revealed deletions consistent with GPSC10-related vaccine-escape profiles. These findings highlight the capacity of GPSC10-ST18362 to persist asymptomatically for months with limited within-host genomic diversity. In this work, authors tracked a pneumococcal serotype 3 strain persisting for a year in a healthy adult, revealing limited genetic change but stable multidrug resistance and features linked to vaccine escape.

Invasive pneumococcal disease (IPD) due to non-vaccine serotypes after the introduction of pneumococcal conjugate vaccines (PCV) remains a global concern. This study used pathogen genomics to evaluate changes in invasive pneumococcal lineages before, during and after vaccine introduction in South Africa. We included genomes (N = 3104) of IPD isolates from individuals aged <18 years (2005–20), spanning four periods: pre-PCV, PCV7, early-PCV13, and late-PCV13. Significant incidence reductions occurred among vaccine-type lineages in the late-PCV13 period compared to the pre-PCV period. However, some vaccine-type lineages continued to cause invasive disease and showed increasing effective population size trends in the post-PCV era. A significant increase in lineage diversity was observed from the PCV7 period to the early-PCV13 period (Simpson’s diversity index: 0.954, 95% confidence interval 0.948-0.961 vs 0.965, 0.962-0.969) supporting intervention-driven population structure perturbation. Increases in the prevalence of penicillin, erythromycin, and multidrug resistance were observed among non-vaccine serotypes in the late-PCV13 period compared to the pre-PCV period. In this work we highlight the importance of continued genomic surveillance to monitor disease-causing lineages post vaccination to support policy-making and future vaccine designs and considerations. Introduction of pneumococcal conjugate vaccines in South Africa has led to reductions in vaccine serotype-related invasive disease. Here, the authors perform a genomic surveillance study to evaluate the impact of vaccines on the population structure of S. pneumoniae .

Background Invasive pneumococcal disease (IPD), caused by Streptococcus pneumoniae , remains a major global health concern, particularly for children. Among more than 100 pneumococcal serotypes, 19A is known for its multidrug resistance (MDR) and increased incidence following PCV7/PCV10 introduction in many countries. Bangladesh introduced PCV10 in 2015 considering the low burden of 19A in the country. Methods Utilizing our IPD surveillance from 2004 to 2023, we investigated the hospital incidence of serotype 19A before and after PCV10 introduction among < 5 years old children in Bangladesh. Whole-genome sequencing was done for 153 serotype 19A isolates from IPD, otitis media, carriage, and urine samples. We used phylogenetic and BEAST analyses to investigate population structure, circulating subtypes, global pneumococcal sequence clusters (GPSCs), sequence types (STs), and antimicrobial resistance genes, and compared them with global 19A genomes. Results Our findings indicate no increase in hospital IPD incidence due to serotype 19A following PCV10 introduction. The MDR 19A-ST320 lineage (GPSC1) remains absent in Bangladesh. ST12888 (GPSC84) became dominant in the post-PCV10 introduction (from 15% to 70%). GPSC84 carries the capsular locus of 19A subtype-I (19A-I), which emerged independently from the standard 19A locus. Macrolide resistance is increasing within the 19A-I/GPSC84 lineage and is estimated to have originated between 2007 and 2011. Conclusions This study presents the first comprehensive genomic analysis of the serotype 19A population in Bangladesh, supporting the decision to introduce PCV10 in Bangladesh based on local pneumococcal serotype burden data. However, the rapid evolution within the local 19A population highlights the need for continuous epidemiological and genomic surveillance to support effective vaccination programs.

Bacterial growth characteristics intrinsic to each strain can impact and influence gene expression, antibiotic susceptibility, and disease pathogenesis. However, little is known about specific genomic variations that influence these bacterial growth features. Here, we investigate the impact of Streptococcus pneumoniae genetics on its in vitro growth features to shed light on genes that may be important targets in the development of vaccines and therapeutics. We use statistical models to estimate growth features and demonstrate that they varied significantly across capsular serotypes and lineages, were strongly correlated with phylogeny, and showed high heritability, highlighting a strong genetic basis. Despite this, genome-wide association studies revealed no specific genomic loci statistically associated with the growth features independently of the genetic background, including those in the locus responsible for capsular polysaccharide synthesis. Our findings suggest that the serotype and lineage, as well as a combination of genomic loci, influence intrinsic pneumococcal growth kinetics, which may have implications for pneumococcal disease pathogenesis.

This month’s Genome Watch highlights how genomic surveillance can provide important information for identifying and tracking emerging pathogens such as SARS-CoV-2.

Rapid adaptation to grow within the physiological conditions found in the host environment is an essential but poorly understood virulence requirement for systemic pathogens such as Streptococcus pneumoniae . We have now demonstrated an essential role for the one-carbon metabolism pathway and a conditional role depending on strain background for proline biosynthesis for S. pneumoniae growth in serum or cerebrospinal fluid, and therefore for systemic virulence. RNAseq and metabolomic data demonstrated that the loss of one-carbon metabolism or proline biosynthesis has profound but differing effects on S. pneumoniae metabolism in human serum, identifying the metabolic processes dependent on each pathway during systemic infection. These data provide a more detailed understanding of the adaptations required by systemic bacterial pathogens in order to cause infection and demonstrate that the requirement for some of these adaptations varies between strains from the same species and could therefore underpin strain variations in virulence potential.

The polysaccharide capsule is essential for the pathogenicity of pneumococcus, which is responsible for millions of deaths worldwide each year. Currently available pneumococcal vaccines are designed to elicit antibodies to the capsule polysaccharides of the pneumococcal isolates commonly causing diseases, and the antibodies provide protection only against the pneumococcus expressing the vaccine-targeted capsules. Since pneumococci can produce different capsule polysaccharides and therefore reduce vaccine effectiveness, it is important to track the appearance of novel pneumococcal capsule types and how these new capsules are created. Herein, we describe a new and the 100th pneumococcal capsule type with unique chemical and serological properties. The capsule type was named 10D for its serologic similarity to 10A. Genetic studies provide strong evidence that pneumococcus created 10D capsule polysaccharide by capturing a large genetic fragment from an oral streptococcus. Such interspecies genetic exchanges could greatly increase diversity of pneumococcal capsules and complicate serotype shifts. Streptococcus pneumoniae (pneumococcus) is a major human pathogen producing structurally diverse capsular polysaccharides. Widespread use of highly successful pneumococcal conjugate vaccines (PCVs) targeting pneumococcal capsules has greatly reduced infections by the vaccine types but increased infections by nonvaccine serotypes. Herein, we report a new and the 100th capsule type, named serotype 10D, by determining its unique chemical structure and biosynthetic roles of all capsule synthesis locus ( cps ) genes. The name 10D reflects its serologic cross-reaction with serotype 10A and appearance of cross-opsonic antibodies in response to immunization with 10A polysaccharide in a 23-valent pneumococcal vaccine. Genetic analysis showed that 10D cps has three large regions syntenic to and highly homologous with cps loci from serotype 6C, serotype 39, and an oral streptococcus strain ( S. mitis SK145). The 10D cps region syntenic to SK145 is about 6 kb and has a short gene fragment of wciN α at the 5′ end. The presence of this nonfunctional wciN α fragment provides compelling evidence for a recent interspecies genetic transfer from oral streptococcus to pneumococcus. Since oral streptococci have a large repertoire of cps loci, widespread PCV usage could facilitate the appearance of novel serotypes through interspecies recombination. IMPORTANCE The polysaccharide capsule is essential for the pathogenicity of pneumococcus, which is responsible for millions of deaths worldwide each year. Currently available pneumococcal vaccines are designed to elicit antibodies to the capsule polysaccharides of the pneumococcal isolates commonly causing diseases, and the antibodies provide protection only against the pneumococcus expressing the vaccine-targeted capsules. Since pneumococci can produce different capsule polysaccharides and therefore reduce vaccine effectiveness, it is important to track the appearance of novel pneumococcal capsule types and how these new capsules are created. Herein, we describe a new and the 100th pneumococcal capsule type with unique chemical and serological properties. The capsule type was named 10D for its serologic similarity to 10A. Genetic studies provide strong evidence that pneumococcus created 10D capsule polysaccharide by capturing a large genetic fragment from an oral streptococcus. Such interspecies genetic exchanges could greatly increase diversity of pneumococcal capsules and complicate serotype shifts.