Streptococcus pneumoniae outbreaks and implications for transmission and control: a systematic review

Chemical Synthesis of Truncated Capsular Oligosaccharide of Serotypes 6C and 6D of Streptococcus pneumoniae with Their Immunological Studies

Serotypes 6C and 6D of Streptococcus pneumoniae are two major variants that cause invasive pneumococcal disease (IPD) in serogroup 6 alongside serotypes 6A and 6B. Since the introduction of the pneumococcal conjugate vaccines PCV7 and PCV13, the number of cases of IPD caused by pneumococcus in children and the elderly population has greatly decreased. However, with the widespread use of vaccines, a replacement effect has recently been observed among different serotypes and lowered the effectiveness of the vaccines. To investigate protection against the original serotypes and to explore protection against variants and replacement serotypes, we created a library of oligosaccharide fragments derived from the repeating units of the capsular polysaccharides of serotypes 6A, 6B, 6C, and 6D through chemical synthesis. The library includes nine pseudosaccharides with or without exposed terminal phosphate groups and four pseudotetrasaccharides bridged by phosphate groups. Six carbohydrate antigens related to 6C and 6D were prepared as glycoprotein vaccines for immunogenicity studies. Two 6A and two 6B glycoconjugate vaccines from previous studies were included in immunogenicity studies. We found that the conjugates containing four phosphate-bridged pseudotetrasaccharides were able to induce good immune antibodies and cross-immunogenicity by showing superior activity and broad cross-protective activity in OPKA bactericidal experiments.

Completion of multidose vaccine series in early childhood: current challenges and opportunities

PURPOSE OF REVIEW

Completion of all doses in multidose vaccine series provides optimal protection against preventable infectious diseases. In this review, we describe clinical and public health implications of multidose vaccine series noncompletion, including current challenges to ensuring children receive all recommended vaccinations. We then highlight actionable steps toward achieving early childhood immunization goals.

RECENT FINDINGS

Although coverage levels are high for most early childhood vaccinations, rates of completion are lower for vaccinations that require multiple doses. Recent research has shown that lower family socioeconomic status, a lack of health insurance coverage, having multiple children in the household, and moving across state lines are associated with children failing to complete multidose vaccine series. These findings provide contextual evidence to support that practical challenges to accessing immunization services are impediments to completion of multidose series. Strategies, including reminder/recall, use of centralized immunization information systems, and clinician prompts, have been shown to increase immunization rates. Re-investing in these effective interventions and modernizing the public health infrastructure can facilitate multidose vaccine series completion.

SUMMARY

Completion of multidose vaccine series is a challenge for immunization service delivery. Increased efforts are needed to address remaining barriers and improve vaccination coverage in the United States.

Effect of trifluoroacetic acid on the antigenicity of capsular polysaccharides obtained from various Streptococcus pneumoniae serotypes

Determining the safety, antigenicity, and immunogenicity by in vitro and in vivo studies is a prerequisite for the development of new vaccines. And this study investigated it for a vaccine made from Streptococcus pneumoniae serotypes 2, 5, 12F, 18C, and 22F. The crude CPS was purified and partially depolymerized by conventional and trifluoroacetic acid methods. 1H NMR analysis confirmed the identity of the depolymerized CPS which gave similar profiles to reference polysaccharides, except for serotype 18C which was de-O-acetylated during TFA treatment. The antigenicity of the depolymerized CPS prepared by either method was comparable to that of the native CPS for serotypes 2, 5, 18C, and 22F based on multiplex bead based competitive inhibition assay. This study demonstrated a relationship between antigenicity and immunogenicity, which offers more suitable candidates for conjugation. It was found that after partial depolymerization process, the CPS with optimal molecular size resulted in higher antigenicity. The immunogenicity of S. pneumoniae serotype 2 conjugates in mice was evaluated by opsonophagocytic assay and a multiplex bead-based assay, wherein on day 42 after immunization, the total and functional IgG titer was found to be increased by 32-fold.

Phylogenetic inference of pneumococcal transmission from cross-sectional data, a pilot study

Background: Inference on pneumococcal transmission has mostly relied on longitudinal studies which are costly and resource intensive. Therefore, we conducted a pilot study to test the ability to infer who infected whom from cross-sectional pneumococcal sequences using phylogenetic inference. Methods: Five suspected transmission pairs, for which there was epidemiological evidence of who infected whom, were selected from a household study. For each pair, Streptococcus pneumoniae full genomes were sequenced from nasopharyngeal swabs collected on the same day. The within-host genetic diversity of the pneumococcal population was used to infer the transmission direction and then cross-validated with the direction suggested by the epidemiological records. Results: The pneumococcal genomes clustered into the five households from which the samples were taken. The proportion of concordantly inferred transmission direction generally increased with increasing minimum genome fragment size and single nucleotide polymorphisms. We observed a larger proportion of unique polymorphic sites in the source bacterial population compared to that of the recipient in four of the five pairs, as expected in the case of a transmission bottleneck. The only pair that did not exhibit this effect was also the pair that had consistent discordant transmission direction compared to the epidemiological records suggesting potential misdirection as a result of false-negative sampling. Conclusions: This pilot provided support for further studies to test if the direction of pneumococcal transmission can be reliably inferred from cross-sectional samples if sequenced with sufficient depth and fragment length.

Vaccinating Welders against Pneumococcus: Evidence from a Systematic Review and Meta-Analysis

Workers occupationally exposed to welding dusts and fumes have been suspected to be at increased risk of invasive pneumococcal disease (IPD). Since the 2010s, the United Kingdom Department of Health and the German Ständige Impfkommission (STIKO) actively recommend welders undergo immunization with the 23-valent polysaccharide (PPV23) pneumococcal vaccine, but this recommendation has not been extensively shared by international health authorities. The present meta-analysis was therefore designed to collect available evidence on the occurrence of pneumococcal infection and IPD among welders and workers exposed to welding fumes, in order to ascertain the effective base of evidence for this recommendation. PubMed, Embase and MedRxiv databases were searched without a timeframe restriction for the occurrence of pneumococcal infections and IPD among welders and workers exposed to metal dusts, and articles meeting the inclusion criteria were included in a random-effect meta-analysis model. From 854 entries, 14 articles (1.6%) underwent quantitative analysis, including eight retrospective studies (publication range: 1980-2010), and six reports of professional clusters in shipbuilding (range: 2017-2020). Welders had an increased likelihood of developing IPD compared with non-welders (odds ratio 2.59, 95% CI 2.00-3.35, I2 = 0%, p = 0.58), and an increased likelihood of dying from IPD (standardized mortality ratio (SMR) 2.42, 95% CI 1.96-2.99, I2 = 0%, p = 0.58). Serotype typing was available for 72 cases, 60.3% of which were represented by serotype 4, followed by 12F (19.2%) and serotype 8 (8.2%). Although the available data derive from a limited number of studies, available results suggest that pneumococcal vaccination should be recommended for workers exposed to welding fumes, and vaccination strategies should consider the delivery of recombinant formulates in order to combine the direct protection against serotypes of occupational interest with the mucosal immunization, reducing the circulation of the pathogen in occupational settings characterized by close interpersonal contact.

Bacterial toxins and heart function: heat-labile Escherichia coli enterotoxin B promotes changes in cardiac function with possible relevance for sudden cardiac death

Bacterial toxins can cause cardiomyopathy, though it is not its most common cause. Some bacterial toxins can form pores in the membrane of cardiomyocytes, while others can bind to membrane receptors. Enterotoxigenic E. coli can secrete enterotoxins, including heat-resistant (ST) or labile (LT) enterotoxins. LT is an AB5-type toxin that can bind to specific cell receptors and disrupt essential host functions, causing several common conditions, such as certain diarrhea. The pentameric B subunit of LT, without A subunit (LTB), binds specifically to certain plasma membrane ganglioside receptors, found in lipid rafts of cardiomyocytes. Isolated guinea pig hearts and cardiomyocytes were exposed to different concentrations of purified LTB. In isolated hearts, mechanical and electrical alternans and an increment of heart rate variability, with an IC50 of ~0.2 μg/ml LTB, were observed. In isolated cardiomyocytes, LTB promoted significant decreases in the amplitude and the duration of action potentials. Na+ currents were inhibited whereas L-type Ca2+ currents were augmented at their peak and their fast inactivation was promoted. Delayed rectifier K+ currents decreased. Measurements of basal Ca2+ or Ca2+ release events in cells exposed to LTB suggest that LTB impairs Ca2+ homeostasis. Impaired calcium homeostasis is linked to sudden cardiac death. The results are consistent with the recent view that the B subunit is not merely a carrier of the A subunit, having a role explaining sudden cardiac death in children (SIDS) infected with enterotoxigenic E. coli, explaining several epidemiological findings that establish a strong relationship between SIDS and ETEC E. coli.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12551-023-01100-6.

Failure to Complete Multidose Vaccine Series in Early Childhood

BACKGROUND

Most early childhood immunizations require 3 to 4 doses to achieve optimal protection. Our objective was to identify factors associated with starting but not completing multidose vaccine series.

METHODS

Using 2019 National Immunization Survey-Child data, US children ages 19 to 35 months were classified in 1 of 3 vaccination patterns: (1) completed the combined 7-vaccine series, (2) did not initiate ≥1 of the 7 vaccine series, or (3) initiated all series, but did not complete ≥1 multidose series. Associations between sociodemographic factors and vaccination pattern were evaluated using multivariable log-linked binomial regression. Analyses accounted for the survey's stratified design and complex weighting.

RESULTS

Among 16 365 children, 72.9% completed the combined 7-vaccine series, 9.9% did not initiate ≥1 series, and 17.2% initiated, but did not complete ≥1 multidose series. Approximately 8.4% of children needed only 1 additional vaccine dose from 1 of the 5 multidose series to complete the combined 7-vaccine series. The strongest associations with starting but not completing multidose vaccine series were moving across state lines (adjusted prevalence ratio [aPR] = 1.45, 95% confidence interval [CI]: 1.18-1.79), number of children in the household (2 to 3: aPR = 1.29, 95% CI: 1.05-1.58; 4 or more: aPR = 1.68, 95% CI: 1.30-2.18), and lack of insurance coverage (aPR = 2.03, 95% CI: 1.42-2.91).

CONCLUSIONS

More than 1 in 6 US children initiated but did not complete all doses in multidose vaccine series, suggesting children experienced structural barriers to vaccination. Increased focus on strategies to encourage multidose series completion is needed to optimize protection from preventable diseases and achieve vaccination coverage goals.

A multiple comorbidities mouse lung infection model in ApoE‑deficient mice

Acute pneumonia is characterised by a period of intense inflammation. Inflammation is now considered to be a key step in atherosclerosis progression. In addition, pre-existing atherosclerotic inflammation is considered to play a role in pneumonia progression and risk. In the present study, a multiple comorbidities murine model was used to study respiratory and systemic inflammation that results from pneumonia in the setting of atherosclerosis. Firstly, a minimal infectious dose of Streptococcus pneumoniae (TIGR4 strain) to produce clinical pneumonia with a low mortality rate (20%) was established. C57Bl/6 ApoE ^-/- mice were fed a high-fat diet prior to administering intranasally 10⁵ colony forming units of TIGR4 or phosphate-buffered saline (PBS). At days 2, 7 and 28 post inoculation (PI), the lungs of mice were imaged by magnetic resonance imaging (MRI) and positron emission tomography (PET). Mice were euthanised and investigated for changes in lung morphology and changes in systemic inflammation using ELISA, Luminex assay and real-time PCR. TIGR4-inoculated mice presented with varying degrees of lung infiltrate, pleural effusion and consolidation on MRI at all time points up to 28 days PI. Moreover, PET scans identified significantly higher FDG uptake in the lungs of TIGR4-inoculated mice up to 28 days PI. The majority (90%) TIGR4-inoculated mice developed pneumococcal-specific IgG antibody response at 28 days PI. Consistent with these observations, TIGR4-inoculated mice displayed significantly increased inflammatory gene expression [interleukin (IL)-1β and IL-6] in the lungs and significantly increased levels of circulating inflammatory protein (CCL3) at 7 and 28 days PI respectively. The mouse model developed by the authors presents a discovery tool to understand the link between inflammation related to acute infection such as pneumonia and increased risk of cardiovascular disease observed in humans.

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

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

Nasopharyngeal colonization by Streptococcus pneumoniae in children and adults before the introduction of the 10-valent conjugate vaccine, Paraguay

Streptococcus pneumoniae is a cause of invasive diseases such as pneumonia, meningitis, and other serious infections among children and adults in Paraguay. This study was conducted to establish S. pneumoniae baseline prevalence, serotype distribution, and antibiotic resistance patterns in healthy children aged 2 to 59 months and adults ≥60 years of age prior to the introduction of PCV10 in the national childhood immunization program in Paraguay. Between April and July 2012, a total of 1444 nasopharyngeal swabs were collected, 718 from children aged 2 to 59 months and 726 from adults ≥60 years of age. The pneumococcal isolation, serotyping, and antibiotic susceptibility testing were performed using standard tests. Pneumococcal colonization prevalence was 34.1% (245/718) in children and 3.3% (24/726) in adults. The most frequent pneumococcal vaccine-types (VT) detected in the children were 6B (42/245), 19F (32/245), 14 (17/245), and 23F (20/245). Carriage prevalence with PCV10 serotypes was 50.6% (124/245) and PCV13 was 59.5% (146/245). Among colonized adults, prevalence of PCV10 and PCV13 serotypes were 29.1% (7/24) and 41.6% (10/24), respectively. Colonized children were more likely to share a bedroom, have a history of respiratory infection or pneumococcal infection compared to non-colonized children. no associations were found in adults. However, no significant associations were found in children and neither in adults. Vaccine-type pneumococcal colonization was highly prevalent in children and rare in adults in Paraguay prior to vaccine introduction, supporting the introduction of PCV10 in the country in 2012. These data will be useful to evaluate the impact of PCV introduction in the country.

Factors associated with pneumococcal vaccine uptake among vulnerable older adults in the United States primary care setting

Pneumococcal vaccine uptake targets set by Healthy People 2020 were not met by 2019 among vulnerable United States populations, yet research suggests progress can be made in primary care settings. This study assessed factors associated with having gotten a pneumococcal vaccine among vulnerable adults aged 50 and older. This study used the 2018 Medical Expenditure Panel Survey nationally representative dataset. Eligible individuals were aged 50-64 with an 'at risk' health condition or ≥65 years and had a primary care provider as their usual source of care (N = 3,760). Binary logistic regression was used to test factors (identified from literature) for a significant association with getting the pneumococcal vaccine. Factors with significant associations were entered into an adjusted multivariable logistic regression model to generate the odds of endorsing a factor given that the respondent got the vaccine. Collinearity among variables was examined with an unacceptable threshold of 0.8 correlation. A significance threshold of 0.05 was used. Those who got the pneumococcal vaccine had 16.7 (p < 0.001), 16.0 (p < 0.001) and 11.0 times (p < 0.001) higher odds of having also gotten the influenza vaccine, the herpes zoster vaccine and a colonoscopy respectively. They had 3.86 times (p = 0.009) higher odds of having diabetes mellitus, 0.036 times (p = 0.019) higher odds of having visited their doctors three times in 2018 and 8.4 times (p = 0.009) higher odds of having seen their doctor within the last year. Concordance statistic for model fit was 0.936. There was a negative association between pneumococcal vaccination and going to three doctor office visits in 2018 vs only once. The strongest positive associations were found between pneumococcal vaccination and getting the herpes zoster vaccine, influenza vaccine and getting a colonoscopy. These results suggest that those who choose to get the pneumococcal vaccine may have higher odds of also getting other vaccines or specific preventative screenings.

Serotype 1 pneumococcus: epidemiology, genomics, and disease mechanisms

Streptococcus pneumoniae (the 'pneumococcus') is a significant cause of morbidity and mortality worldwide, causing life-threatening diseases such as pneumonia, bacteraemia, and meningitis, with an annual death burden of over one million. Discovered over a century ago, pneumococcal serotype 1 (S1) is a significant cause of these life-threatening diseases. Our understanding of the epidemiology and biology of pneumococcal S1 has significantly improved over the past two decades, informing the development of preventative and surveillance strategies. However, many questions remain unanswered. Here, we review the current state of knowledge of pneumococcal S1, with a special emphasis on clinical epidemiology, genomics, and disease mechanisms.

Spray-dried Pneumococcal Membrane Vesicles are Promising Candidates for Pulmonary Immunization

Pneumococcal infections represent a global health threat, which requires novel vaccine developments. Extracellular vesicles are secreted from most cells, including prokaryotes, and harbor virulence factors and antigens. Hence, bacterial membrane vesicles (MVs) may induce a protective immune response. For the first time, we formulate spray-dried gram-positive pneumococcal MVs-loaded vaccine microparticles using lactose/leucine as inert carriers to enhance their stability and delivery for pulmonary immunization. The optimized vaccine microparticles showed a mean particle size of 1-2µm, corrugated surface, and nanocrystalline nature. Their aerodynamic diameter of 2.34µm, average percentage emitted dose of 88.8%, and fine powder fraction 79.7%, demonstrated optimal flow properties for deep alveolar delivery using a next-generation impactor. Furthermore, confocal microscopy confirmed the successful encapsulation of pneumococcal MVs within the prepared microparticles. Human macrophage-like THP-1 cells displayed excellent viability, negligible cytotoxicity, and a rapid uptake around 60% of fluorescently labeled MVs after incubation with vaccine microparticles. Moreover, vaccine microparticles increased the release of pro-inflammatory cytokines tumor necrosis factor and interleukin-6 from primary human peripheral blood mononuclear cells. Vaccine microparticles exhibited excellent properties as promising vaccine candidates for pulmonary immunization and are optimal for further animal testing, scale-up and clinical translation.

International links between Streptococcus pneumoniae vaccine serotype 4 sequence type (ST) 801 in Northern European shipyard outbreaks of invasive pneumococcal disease

BACKGROUND

Pneumococcal disease outbreaks of vaccine preventable serotype 4 sequence type (ST)801 in shipyards have been reported in several countries. We aimed to use genomics to establish any international links between them.

METHODS

Sequence data from ST801-related outbreak isolates from Norway (n = 17), Finland (n = 11) and Northern Ireland (n = 2) were combined with invasive pneumococcal disease surveillance from the respective countries, and ST801-related genomes from an international collection (n = 41 of > 40,000), totalling 106 genomes. Raw data were mapped and recombination excluded before phylogenetic dating.

RESULTS

Outbreak isolates were relatively diverse, with up to 100 SNPs (single nucleotide polymorphisms) and a common ancestor estimated around the year 2000. However, 19 Norwegian and Finnish isolates were nearly indistinguishable (0-2 SNPs) with the common ancestor dated around 2017.

CONCLUSION

The total diversity of ST801 within the outbreaks could not be explained by recent transmission alone, suggesting that harsh environmental and associated living conditions reported in the shipyards may facilitate invasion of colonising pneumococci. However, near identical strains in the Norwegian and Finnish outbreaks does suggest that transmission between international shipyards also contributed to those outbreaks. This indicates the need for improved preventative measures in this working population including pneumococcal vaccination.

Pneumococcal Meningitis Outbreaks in Africa, 2000-2018: Systematic Literature Review and Meningitis Surveillance Database Analyses

BACKGROUND

The meningitis belt of sub-Saharan Africa has traditionally experienced large outbreaks of meningitis mainly caused by Neisseria meningitidis. More recently, Streptococcus pneumoniae has been recognized as a cause of meningitis outbreaks in the region. Little is known about the natural history and epidemiology of these outbreaks, and, in contrast to meningococcal meningitis, there is no agreed definition for a pneumococcal meningitis epidemic. The aim of this analysis was to systematically review and understand pneumococcal meningitis outbreaks in Africa between 2000 and 2018.

METHODS

Meningitis outbreaks were identified using a systematic literature review and analyses of meningitis surveillance databases. Potential outbreaks were included in the final analysis if they reported at least 10 laboratory-confirmed meningitis cases above baseline per week with ≥50% of cases confirmed as pneumococcus.

RESULTS

A total of 10 potential pneumococcal meningitis outbreaks were identified in Africa between 2000 and 2018. Of these, 2 were classified as confirmed, 7 were classified as possible, and 1 was classified as unlikely. Three outbreaks spanned more than 1 year. In general, the outbreaks demonstrated lower peak attack rates than meningococcal meningitis outbreaks and had a predominance of serotype 1. Patients with pneumococcal meningitis tended to be older and had higher case fatality rates than meningococcal meningitis cases. An outbreak definition, which includes a weekly district-level incidence of at least 10 suspected cases per 100 000 population per week, with >10 cumulative confirmed cases of pneumococcus per year, would have identified all 10 potential outbreaks.

CONCLUSIONS

Given the frequency of and high case fatality from pneumococcal meningitis outbreaks, public health recommendations on vaccination strategies and the management of outbreaks are needed. Improved laboratory testing for S. pneumoniae is critical for early outbreak identification.

Whole-Genome Analysis of Streptococcus pneumoniae Serotype 4 Causing Outbreak of Invasive Pneumococcal Disease, Alberta, Canada

After the introduction of pneumococcal conjugate vaccines for children, invasive pneumococcal disease caused by Streptococcus pneumoniae serotype 4 declined in all ages in Alberta, Canada, but it has reemerged and spread in adults in Calgary, primarily among persons who are experiencing homelessness or who use illicit drugs. We conducted clinical and molecular analyses to examine the cases and isolates. Whole-genome sequencing analysis indicated relatively high genetic variability of serotype 4 isolates. Phylogenetic analysis identified 1 emergent sequence type (ST) 244 lineage primarily associated within Alberta and nationally distributed clades ST205 and ST695. Isolates from 6 subclades of the ST244 lineage clustered regionally, temporally, and by homeless status. In multivariable logistic regression, factors associated with serotype 4 invasive pneumococcal disease were being male, being <65 years of age, experiencing homelessness, having a diagnosis of pneumonia or empyema, or using illicit drugs.

Immunogenicity of PCV24, an expanded pneumococcal conjugate vaccine, in adult monkeys and protection in mice

Invasive pneumococcal disease (IPD) is responsible for serious illnesses such as bacteremia, sepsis, meningitis, and pneumonia in young children, older adults, and persons with immunocompromising conditions and often leads to death. Although the most recent pneumococcal conjugate vaccines (PCVs) have been designed to target serotypes identified as the primary causative agents of IPD, the epidemiological landscape continues to change stressing the need to develop new PCVs. We have developed an investigational 24-valent PCV (PCV24) including serotypes 1, 2, 3, 4, 5, 6A, 6B, 7F, 8, 9N, 9V, 10A, 11A, 12F, 14, 15B, 17F, 18C, 19A, 19F, 20, 22F, 23F, and 33F all conjugated to CRM197 and evaluated this vaccine in adult monkeys. PCV24 was shown to be immunogenic and induced functional antibody for all vaccine serotypes. Of the serotypes common to PCV13 and V114 (PCV15), PCV24 had a similar immunogenic response with the exceptions of 23F which had higher IgG GMCs for PCV13 and V114, and 7F which had higher GMCs for PCV13. Functional antibody responses were similar for the serotypes in common between PCV24, PCV13 and V114 vaccines, with the exception of serotype 7F which was greater for PCV13. Overall, this study shows that PCV24 provided similar immunogenicity as the lower valent vaccines in adult monkeys with no apparent serotype interference. In addition, PCV24 also provided protection against pneumococcal infection in a mouse challenge model.

A Nationwide Outbreak of Invasive Pneumococcal Disease in Israel Caused by Streptococcus Pneumoniae Serotype 2

BACKGROUND

Invasive pneumococcal disease (IPD) caused by Streptococcus pneumoniae serotype 2 (Sp2) is infrequent. Large scale outbreaks have not been reported following pneumococcal conjugate vaccine (PCV) implementation. We describe a Sp2 IPD outbreak in Israel, in the 13-valent PCV (PCV13) era, with focus on Sp2 population structure and evolutionary dynamics.

METHODS

The data derived from a population-based, nationwide active surveillance of IPD since 2009. 7-valent PCV (PCV7)/PCV13 vaccines were introduced in July 2009 and November 2010, respectively. Sp2 isolates were tested for antimicrobial susceptibility, Multilocus Sequence Typing (MLST) and Whole Genome Sequencing (WGS) analysis.

RESULTS

Overall, 170 Sp2 IPD cases were identified during 2009-2019; Sp2 increased in 2015 and caused 6% of IPD during 2015-2019, a 7-fold increase compared with 2009-2014.The outbreak was caused by a previously unreported molecular type (ST-13578), initially observed in Israel in 2014. This clone caused 88% of Sp2 during 2015-2019. ST-13578 is a single-locus variant of ST-1504, previously reported globally, including in Israel. WGS analysis confirmed clonality among the ST-13578 population. Single-nucleotide polymorphisms-dense regions support a hypothesis that the ST-13578 outbreak clone evolved from ST-1504 by recombination.All tested strains were penicillin-susceptible (MIC <0.06 μg/mL). The ST-13578 clone was identified almost exclusively (99%) in the Jewish population and was mainly distributed in 3/7 Israeli districts. The outbreak is still ongoing, although declining since 2017.Conclusions: To the best of our knowledge, this is the first widespread Sp2 outbreak since PCV13 introduction worldwide, caused by the emerging ST-13578 clone.

Outbreak of invasive pneumococcal disease among shipyard workers, Turku, Finland, May to November 2019

We report an outbreak of invasive pneumococcal disease and pneumococcal pneumonia among shipyard workers, in Turku, Southwest Finland. In total, 31 confirmed and six probable cases were identified between 3 May and 28 November 2019. Streptococcus pneumoniae serotypes 12F, 4 and 8 were isolated from blood cultures of 25 cases. Occupational hygiene measures and vaccination of ca 4,000 workers are underway to control the outbreak at the shipyard.

Resistance of Gram-Positive Bacteria to Current Antibacterial Agents and Overcoming Approaches

The discovery of antibiotics has created a turning point in medical interventions to pathogenic infections, but unfortunately, each discovery was consistently followed by the emergence of resistance. The rise of multidrug-resistant bacteria has generated a great challenge to treat infections caused by bacteria with the available antibiotics. Today, research is active in finding new treatments for multidrug-resistant pathogens. In a step to guide the efforts, the WHO has published a list of the most dangerous bacteria that are resistant to current treatments and requires the development of new antibiotics for combating the resistance. Among the list are various Gram-positive bacteria that are responsible for serious healthcare and community-associated infections. Methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus faecium, and drug-resistant Streptococcus pneumoniae are of particular concern. The resistance of bacteria is an evolving phenomenon that arises from genetic mutations and/or acquired genomes. Thus, antimicrobial resistance demands continuous efforts to create strategies to combat this problem and optimize the use of antibiotics. This article aims to provide a review of the most critical resistant Gram-positive bacterial pathogens, their mechanisms of resistance, and the new treatments and approaches reported to circumvent this problem.

Upper airways colonisation of Streptococcus pneumoniae in adults aged 60 years and older: A systematic review of prevalence and individual participant data meta-analysis of risk factors

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Systematic review and meta-analysis of 18 studies and more than 6000 participants.

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Adults over the age of 60 had a pooled prevalence of pneumococcal carriage of 9%.

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Risk factors: contact with children, smoking and residing in a nursing home.

Background

Colonisation with Streptococcus pneumoniae can lead to invasive pneumococcal disease and pneumonia. Pneumococcal acquisition and prevalence of colonisation are high in children. In older adults, a population susceptible to pneumococcal disease, colonisation prevalence is reported to be lower, but studies are heterogeneous.

Methods

This is a systematic review and meta-analysis of prevalence of, and risk factors for, pneumococcal colonisation in adults ≥ 60 years of age (PROSPERO #42016036891). We identified peer-reviewed studies reporting the prevalence of S. pneumoniae colonisation using MEDLINE and EMBASE (until April 2016), excluding studies of acute disease. Participant-level data on risk factors were sought from each study.

Findings

Of 2202 studies screened, 29 were analysable: 18 provided participant-level data (representing 6290 participants). Prevalence of detected pneumococcal colonisation was 0–39% by conventional culture methods and 3–23% by molecular methods. In a multivariate analysis, colonisation was higher in persons from nursing facilities compared with the community (odds ratio (OR) 2•30, 95% CI 1•26–4•21 and OR 7•72, 95% CI 1•15–51•85, respectively), in those who were currently smoking (OR 1•69, 95% CI 1•12–2•53) or those who had regular contact with children (OR 1•93, 95%CI 1•27–2•93). Persons living in urban areas had significantly lower carriage prevalence (OR 0•43, 95%CI 0•27–0•70).

Interpretation

Overall prevalence of pneumococcal colonisation in older adults was higher than expected but varied by risk factors. Future studies should further explore risk factors for colonisation, to highlight targets for focussed intervention such as pneumococcal vaccination of high-risk groups.

Funding

No funding was required.

Nano-Based Drug Delivery or Targeting to Eradicate Bacteria for Infection Mitigation: A Review of Recent Advances

Pathogenic bacteria infection is a major public health problem due to the high morbidity and mortality rates, as well as the increased expenditure on patient management. Although there are several options for antimicrobial therapy, their efficacy is limited because of the occurrence of drug-resistant bacteria. Many conventional antibiotics have failed to show significant amelioration in overall survival of infectious patients. Nanomedicine for delivering antibiotics provides an opportunity to improve the efficiency of the antibacterial regimen. Nanosystems used for antibiotic delivery and targeting to infection sites render some benefits over conventional formulations, including increased solubility, enhanced stability, improved epithelium permeability and bioavailability, prolonged antibiotic half-life, tissue targeting, and minimal adverse effects. The nanocarriers' sophisticated material engineering tailors the controllable physicochemical properties of the nanoparticles for bacterial targeting through passive or active targeting. In this review, we highlight the recent progress on the development of antibacterial nanoparticles loaded with antibiotics. We systematically introduce the concepts and amelioration mechanisms of the nanomedical techniques for bacterial eradication. Passive targeting by modulating the nanoparticle structure and the physicochemical properties is an option for efficient drug delivery to the bacteria. In addition, active targeting, such as magnetic hyperthermia induced by iron oxide nanoparticles, is another efficient way to deliver the drugs to the targeted site. The nanoparticles are also designed to respond to the change in environment pH or enzymes to trigger the release of the antibiotics. This article offers an overview of the benefits of antibacterial nanosystems for treating infectious diseases.

Super-dominant pathobiontic bacteria in the nasopharyngeal microbiota as causative agents of secondary bacterial infection in influenza patients

The source of secondary lower respiratory tract bacterial infections in influenza patients is not fully understood. A case–control study was conducted during the 2017–2018 influenza epidemic period in Beijing, China. Nasopharyngeal swabs were collected from 52 virologically confirmed influenza patients and 24 healthy medical staff. The nasopharyngeal microbiota taxonomic composition was analysed using high-throughput sequencing of the 16S rRNA gene V3–V4 regions. The super-dominant pathobiontic bacterial genus (SDPG) was defined as that accounting for >50% of sequences in a nasopharyngeal swab. We attempted to isolate bacteria of this genus from both nasopharyngeal swabs and lower-respiratory tract samples and analyse their genetic similarities. We observed a significantly lower taxonomy richness in influenza cases compared with healthy controls. A SDPG was detected in 61% of severe cases but in only 24% of mild cases and 29% of healthy controls. In 10 cases, the species isolated from lower-respiratory tract infection sites were identified as belonging to the nasopharyngeal microbiota SDPG. Genetically identical strains were isolated from both nasopharyngeal swabs and lower-respiratory tract infection sites, including 23 Acinetobacter baumannii strains from six severe cases, six Klebsiella pneumoniae strains from two severe cases, five Pseudomonas aeruginosa strains from one severe and one mild case, and four Corynebacterium striatum strains from two severe cases. The SDPG in the nasopharyngeal microbiota are the likely cause of subsequent infection in influenza patients.

Commentary: Why Has Uptake of Pneumococcal Vaccines for Children Been So Slow? The Perils of Undervaluation

Pediatric pneumococcal disease exacts a substantial burden on global health, much of which is vaccine-preventable. Despite this considerable burden and the demonstrably high efficacy of pneumococcal conjugate vaccines (PCVs), the overall level of PCV uptake remains concerningly low, especially compared with that of other childhood-recommended vaccines, such as tuberculosis and polio. A broad set of plausible explanations exists for this low uptake, including logistical challenges, psychosocial factors and affordability. One additional and systematic cause of low uptake, which is the focus of our discussion, is economists' and policymakers' tendency to undervalue vaccination in general by adopting a narrow health sector perspective when performing economic evaluations of vaccines. We present an alternative, societal framework for economic evaluations that encompasses a broader set of socioeconomic benefits in addition to health benefits. Quantifying a more comprehensive taxonomy of PCV's benefits will help to address potential undervaluation and may be sufficient not only to justify recommendation and reimbursement but also to stimulate efforts and investment toward closing coverage gaps.

Pneumococcal conjugate vaccine use during humanitarian crises

Streptococcus pneumoniae is a common human commensal that causes a sizeable part of the overall childhood mortality in low income settings. Populations affected by humanitarian crises are at especially high risk, because a multitude of risk factors that are enhanced during crises increase pneumococcal transmission and disease severity. Pneumococcal conjugate vaccines (PCVs) provide effective protection and have been introduced into the majority of routine childhood immunisation programmes globally, though several barriers have hitherto limited their uptake during humanitarian crises. When PCV coverage cannot be sustained during crises or when PCV has not been part of routine programmes, mass vaccination campaigns offer a quick acting and programmatically feasible bridging solution until services can be restored. However, we currently face a paucity of evidence on which to base the structure of such campaigns. We believe that, now that PCV can be procured at a substantially reduced price through the Humanitarian Mechanism, this lack of information is a remaining hurdle to PCV use in humanitarian crises. Considering the difficulties in conducting research in crises, we propose an evidence generation pathway consisting of primary data collection in combination with mathematical modelling followed by quasi-experimental evaluation of a PCV intervention, which can inform on optimal vaccination strategies that consider age targeting, dosing regimens and impact duration.

Outbreaks of severe pneumococcal disease in closed settings in the conjugate vaccines era, 2010-2018: A systematic review to inform national guidance in the UK

INTRODUCTION

Pneumococcal outbreaks are rare but they still occur, particularly in closed settings usually involving vulnerable groups. We undertook a systematic review to identify strategies for controlling pneumococcal outbreaks since the licensure of higher-valent pneumococcal conjugate vaccines (PCVs).

METHODS

A systematic literature search was performed for pneumococcal outbreaks published since 2010. A cluster was defined as two or more cases of severe pneumococcal disease in a closed setting within 14 days.

RESULTS

Eleven reports were identified, including seven caused by serotypes in both the 13-valent PCV (PCV13) and the 23-valent polysaccharide vaccine (PPV23); two were due to a PCV13-only serotype (6A) and one each by a PCV13-related serotype (6C) and a non-vaccine serotype (15A). Eight reported infection control measures, including reinforcing hand washing, respiratory hygiene and patient cohorting. PPV23 was used in five outbreaks, while PCV13 and both vaccines were used in one outbreak each. Different antibiotics were used for chemoprophylaxis in eight outbreaks.

CONCLUSIONS

Most pneumococcal outbreaks are currently caused by vaccine-preventable serotypes, and PPV23 is the preferred vaccine in more than half the outbreaks. Early implementation of infection control measures is important, and antibiotic chemoprophylaxis should be considered for high-risk individuals.