The impact of pneumococcal conjugate vaccines on carriage of and disease caused by Streptococcus pneumoniae serotypes 6C and 6D in southern Israel

Effects of PCV10 and PCV13 on pneumococcal serotype 6C disease, carriage, and antimicrobial resistance

BACKGROUND

The cross-protection of pneumococcal conjugate vaccines (PCV) against serotype 6C is not clearly documented, although 6C represents a substantial burden of pneumococcal disease in recent years. A systematic review by the World Health Organization that covered studies through 2016 concluded that available data were insufficient to determine if either PCV10 (which contains serotype 6B but not 6A) or PCV13 (containing serotype 6A and 6B) conferred protection against 6C.

METHODS

We performed a systematic review of randomized controlled trials and observational studies published between January 2010 - August 2022 (Medline/Embase), covering the direct, indirect, and overall effect of PCV10 and PCV13 against 6C invasive pneumococcal disease (IPD), non-IPD, nasopharyngeal carriage (NPC), and antimicrobial resistance (AMR).

RESULTS

Of 2548 publications identified, 112 were included. Direct vaccine effectiveness against 6C IPD in children ranged between 70 and 85 % for ≥ 1 dose PCV13 (n = 3 studies), was 94 % in fully PCV13 vaccinated children (n = 2), and -14 % for ≥ 1 dose of PCV10 (n = 1). Compared to PCV7, PCV13 efficacy against 6C NPC in children was 66 % (n = 1). Serotype 6C IPD rates or NPC prevalence declined post-PCV13 in most studies in children (n = 5/6) and almost half of studies in adults (n = 5/11), while it increased post-PCV10 for IPD and non-IPD in all studies (n = 6/6). Changes in AMR prevalence were inconsistent.

CONCLUSIONS

In contrast to PCV10, PCV13 vaccination consistently protected against 6C IPD and NPC in children, and provided some level of indirect protection to adults, supporting that serotype 6A but not 6B provides cross-protection to 6C. Vaccine policy makers and regulators should consider the effects of serotype 6A-containing PCVs against serotype 6C disease in their decisions.

Molecular surveillance of pneumococcal carriage following completion of immunization with the 13-valent pneumococcal conjugate vaccine administered in a 3 + 1 schedule

In a cross-sectional study, with the use of molecular methods, we aimed to gain insight into oropharyngeal pneumococcal colonization over time in 1212 Greek children recruited in general pediatric settings throughout the country; they were fully vaccinated with PCV13 (3 + 1 schedule). A single sample was obtained from each child at a time interval of 26 days to 70 months after administration of the 4th (booster) PCV13 dose; sampling time was divided into six time intervals. Carriage of Streptococcus pneumoniae was detected by real-time PCR targeting the lytA gene and isolates were serotyped by singleplex real-time PCR assays. Multiple control procedures to avoid false-positive results were applied. We showed an overall S. pneumoniae carriage rate of 48.6%. Serotyping identified typeable isolates in 82% of the total lytA-positive samples. Non-PCV13 serotypes represented 83.8% of total isolates when excluding serogroups with mixed PCV13 and non-PCV13 serotypes. In multivariate analysis daycare/school attendance emerged as the main contributing factor. Notably, serotypes 19A and 3 were the only two PCV13 serotypes the colonization rate of which increased over time (χ² for trend P < 0.001 and P = 0.012, respectively). The application of the SP2020 gene on lytA-positive serotyped samples showed pneumococcal colonization in 97% of cases, and the overall colonization profile over time closely resembled that of the lytA gene. With the provisions of the methodological approach and age group of our study, the use of the oropharynx emerges as a reliable alternative to the nasopharynx in estimating pneumococcal carriage in epidemiological studies.

The TCM prescription Ma-xing-shi-gan-tang inhibits Streptococcus pneumoniae pathogenesis by targeting pneumolysin

ETHNOPHARMACOLOGICAL RELEVANCE

Ma-xing-shi-gan-tang (MXSGT), which is documented in the Treatise on Febrile Diseases and is a therapeutic drug, is a well-known classic prescription in China and has been widely studied. Previous studies have shown that MXSGT has various pharmacological activities, including anti-influenza virus activity, and ameliorates microvascular hyperpermeability and inflammatory reactions. However, no study has reported the effect of MXSGT in the treatment of bacterial pneumonia.

AIM OF THE STUDY

In this study, the potential inhibition of MXSGT against the virulence of S. pneumoniae by targeting PLY was investigated.

MATERIALS AND METHODS

First, HPLC analysis was used to determine the main components of MXSGT. Then PLY protein was constructed and used for hemolysis assay and western blot to test the ability of MXSGT to inhibit PLY activity, production and widowed characteristics. The growth curve of S. pneumoniae was drawled with or without MXSGT treatment. In addition, the inhibition of MXSGT against PLY-mediated A549 cell death was examined by cytotoxicity assay. Finally, the mouse experiment was used to verify the effect of MXSGT on mouse lungs.

RESULTS

This work has discovered that MXSGT, a TCM prescription, is an effective inhibitor of PLY, an important virulence factor that is essential for S. pneumoniae pathogenicity. MXSGT inhibits the oligomerization of PLY without affecting S. pneumoniae growth and PLY production. In addition, experimental MXSGT treatment was effective against S. pneumoniae infection both in vitro and in vivo.

CONCLUSION

These findings directly demonstrate the potential mechanism of the Chinese herbal formula MXSGT in the treatment of pneumococcal disease and provide additional evidence for promotion of the wide use of MXSGT in the clinic.

Twenty-Year Public Health Impact of 7- and 13-Valent Pneumococcal Conjugate Vaccines in US Children

Pneumococcal conjugate vaccines (PCVs) have been used in the United States since 2000. To assess the cumulative 20-year effect of PCVs on invasive pneumococcal disease (IPD) incidence among children <5 years of age, we analyzed Active Bacterial Core Surveillance data, conducted a literature review, and modeled expected and observed disease. We found that PCVs have averted >282,000 cases of IPD, including ≈16,000 meningitis, ≈172,000 bacteremia, and ≈55,000 bacteremic pneumonia cases. In addition, vaccination has prevented 97 million healthcare visits for otitis media, 438,914-706,345 hospitalizations for pneumonia, and 2,780 total deaths. IPD cases declined 91%, from 15,707 in 1997 to 1,382 in 2019. Average annual visits for otitis media declined 41%, from 78 visits/100 children before PCV introduction to 46 visits/100 children after PCV13 introduction. Annual pneumonia hospitalizations declined 66%-79%, from 110,000-175,000 in 1997 to 37,000 in 2019. These findings confirm the substantial benefits of PCVs for preventing IPD in children.

Early Impact of 13-Valent Pneumococcal Conjugate Vaccine Use on Invasive Pneumococcal Disease Among Adults With and Without Underlying Medical Conditions-United States

BACKGROUND

The 13-valent pneumococcal vaccine (PCV13) was introduced for US children in 2010 and for immunocompromised adults ≥19 years old in series with the 23-valent polysaccharide vaccine (PPSV23) in 2012. We evaluated PCV13 indirect effects on invasive pneumococcal disease (IPD) among adults with and without PCV13 indications.

METHODS

Using Active Bacterial Core surveillance and the National Health Survey, using Active Bacterial Core surveillance and the National Health Interview Survey, we estimated and compared IPD incidence in 2013-2014 and 2007-2008, by age and serotype group (PCV13, PPSV23-unique, or nonvaccine types [NVTs]), among adults with and without PCV13 indications.

RESULTS

IPD incidence declined among all adults. Among adults 19-64 years, PCV13-type IPD declined 57% (95% confidence interval [CI], -68% to -43%) in adults with immunocompromising conditions (indication for PCV13 use), 57% (95% CI, -62% to -52%) in immunocompetent adults with chronic medical conditions (CMCs, indications for PPSV23 use alone), and 74% (95% CI, -78% to -70%) in adults with neither vaccine indication. Among adults aged ≥65 years, PCV13-type IPD decreased 68% (95% CI, -76% to -60%) in those with immunocompromising conditions, 68% (95% CI, -72% to -63%) in those with CMCs, and 71% (95% CI, -77% to -64%) in healthy adults. PPSV23-unique types increased in adults 19‒64 years with CMCs, and NVTs did not change among adults with or without PCV13 indications. From 2013 to 2014, non-PCV13 serotypes accounted for 80% of IPD.

CONCLUSIONS

IPD incidence among US adults declined after PCV13 introduction in children. Similar reductions in PCV13-type IPD in those with and without PCV13 indications suggest that observed benefits are largely due to indirect effects from pediatric PCV13 use rather than direct use among adults.

Phenotypic and genotypic characterization of serogroup 6 Streptococcus pneumoniae isolates collected during 10-valent pneumococcal conjugate vaccine era in Bulgaria

Serogroup 6 remains common in the pneumococcal-conjugated vaccine era in Bulgaria; therefore, we investigated its clonal and serotype dynamics. The antibiotic susceptibilities were assessed by broth microdilution. Strains identified as serogroup 6 with latex agglutination method were subjected to serotype-specific PCRs. Erythromycin-resistant strains were analyzed by PCR for presence of ermB and mefE genes. MLST was performed to define clonal composition of the sequence types (STs). Serogroup 6 was represented by 40 (13.3%) from 301 invasive and non-invasive Streptococcus pneumoniae isolates. Molecular serotyping revealed new emerging serotype 6C (6.6%), not detected in pre-vaccine era. Among unvaccinated patients, mostly we observed serotypes 6А (57.1%) and 6В (28.6%). Serotype 6C was distinctive for vaccinated children (64%), followed by 6A (24%). Penicillin and ceftriaxone non-susceptible serogroup 6 strains were 65% and 5%, respectively; erythromycin- and clindamycin-resistant were 70.0% and 52.5%, respectively. Multidrug-resistant strains were 57.5%. Prevalent genetic determinant for macrolide resistance was ermB gene (75%). MLST revealed 17 STs into 5 clonal complexes and 7 singletons. Predominant genetic lineage was CC386, represented by MDR-6C non-invasive strains. Serotype 6B, principally responsible for invasive diseases in the pre-vaccine era, retreated this position to serotype 6A.

MUCOSAL anti-infections vaccines: Beyond conventional vaccines

An urgent search is currently underway for alternatives to antibiotics to prevent infections, due to the accelerated evolution and increase in antibiotic resistance. This problem is more serious for patients with recurrent infections, since they have to use many cycles of antibiotics per year, so the risk for antibiotic resistance is higher and can be life-threatening. In recent years, the use of prophylactic vaccines via the mucosal route for these patients with recurrent infections has been demonstrated as a potentially beneficial and safe alternative to prevent infections. The new knowledge about mucosal immunity and trained immunity, a form of innate immunity memory that can enhance the response to different infectious threads, has made it easier to extend its use. The application of the new concepts of trained immunity may explain the simultaneous pro-tolerogenic and boosting effect or effects of these drugs on diverse immune cells for different infections. In this review, we describe the immunomodulatory mechanisms of mucosal polybacterial vaccines and their connection with trained immunity and its utility in the prevention of recurrent infections in immunosuppressed patients.

Antimicrobial susceptibility and fluctuations in clonal complexes of serogroup 6 Streptococcus pneumoniae isolates collected from children in Beijing, China, between 1997 and 2016

This study examined the antimicrobial susceptibility patterns and clonal complex (CC) characteristics of serogroup 6 Streptococcus pneumoniae isolates collected from children in Beijing, China, between 1997 and 2016. Serotypes were determined using the Quellung reaction, and the antimicrobial susceptibility profiles of the isolates were determined using the disc-diffusion method or by E-test. Sequence types (STs) were assigned based on multilocus sequence typing. A total of 250 isolates were examined, with 55.2%, 30.0%, 12.8%, and 2.0% of isolates identified as serotypes 6A, 6B, 6C, and 6D, respectively. All of the isolates were susceptible to levofloxacin and vancomycin, and the non-suceptibitility rate to penicillin was 41.6%. Eighty-two distinct STs, assigned to 13 CCs and 28 singletons, were identified. CC982 was the most prevalent CC amongst serotype 6A isolates (34%), followed by CC9789 and CC3173. Amongst serotype 6B isolates, CC90 and CC4542 were the most common, accounting for 25.3% and 14.7% of isolates respectively. Over the study period, the prevalence of CC982, CC4542, and CC4536 isolates showing susceptibility to penicillin and cefuroxime decreased, and the proportion of CC3173, CC9789, CC855, and CC902 isolates showing non-susceptibility to these two antibiotics increased.

Serotype and MLST-based inference of population structure of clinical Streptococcus pneumoniae from invasive and noninvasive pneumococcal disease

Streptococcus pneumoniae is an important human pathogen causing various diseases. In this study, S. pneumoniae from invasive (IPD) and noninvasive pneumococcal disease (NIPD) were studied by serotype and multilocus sequence typing (MLST) for population structure characteristics. A total of 169 clinical S. pneumoniae, containing 63 IPD and 106 NIPD strains, were analyzed. 19F, 19A, 6A, 6B, 1, 14 and 23F were the dominant serotypes in both IPD and NIPD strains. By MLST, 169 strains were divided into 85 sequence types (STs) with an index of discrimination (IOD) value of 0.9606. The seven predominant STs were ST271, ST320, ST876, ST3173, ST236, ST81 and ST342, which were mainly associated with serotypes 19F, 19A, 14, 6A, 19F, 1, and 1/23F, respectively. The 63 IPD strains were divided into 20 serotypes (IOD=0.9135) and 44 STs (IOD=0.9795); the 106 NIPD strains were divided into 16 serotypes (IOD=0.8334) and 49 STs (IOD=0.9430). In conclusion, the serotypes and ST distribution of IPD and NIPD strains analyzed in this study are similar to the profiles observed in other cities of China, suggesting that the clinical S. pneumoniae isolates were derived from clones generally circulating in China. The strains showed a variety of serotypes and STs, and the IPD strains showed higher serotype and genetic diversity than NIPD strains.

Clinical Utility of Polymerase Chain Reaction Testing for Streptococcus pneumoniae in Pediatric Cerebrospinal Fluid Samples: A Diagnostic Accuracy Study of More Than 2000 Samples From 2004 to 2015

The aim of this retrospective study was to review the diagnostic accuracy of real-time polymerase chain reaction (PCR) testing of cerebrospinal fluid (CSF) samples for Streptococcus pneumoniae DNA in comparison with traditional bacterial culture. The hypothesis was that PCR is more sensitive than culture and would detect more cases of pneumococcal meningitis, particularly in children treated with antimicrobials before CSF sampling occurred. Patients younger than 16 years of age who had a CSF sample tested for S. pneumoniae DNA by PCR between 2004 and 2015 were included. A total of 2025 samples were included, and the PCR had a sensitivity of 100% and specificity of 98% for the detection of S. pneumoniae DNA in comparison with culture. Of the 28 culture negative/PCR positive cases, 25 (89%) were probable meningitis cases and only 3 (11%) were suspected false positive results. Nineteen (76%) of the 25 probable cases required ICU admission, and 3 died (12%). Six different serotypes were found in the culture positive patients (18C, 6B, 14, 22F, 7F and 33F). This study demonstrates that PCR testing of CSF samples for S. pneumoniae is sensitive and specific when compared with culture. PCR is particularly useful in detecting those cases where culture is negative, perhaps relating to pre-CSF sampling administration of antimicrobials.

Hilaire AJ, Gerson DF. Novel polysaccharide-protein conjugates provide an immunogenic 13-valent pneumococcal conjugate vaccine for S. pneumoniae

Pneumonia remains the single leading cause of childhood death worldwide. Despite the commercial availability of multiple pneumococcal conjugate vaccines (PCVs), high dosage cost and supply shortages prevent PCV delivery to much of the developing world. The current work presents high-yield pneumococcal conjugates that are immunogenic in animals and suitable for use in human vaccine development. The 13-valent pneumococcal conjugate vaccine (PCV-13) investigated in this research incorporated serotypes 1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F, and 23F. Pneumococcal polysaccharides (PnPSs) and CRM₁₉₇ carrier protein were produced and purified in-house, and used to prepare PnPS-CRM conjugates using unique, cyanide-free, in vacuo glycation conjugation methods. In vitro characterization confirmed the generation of higher molecular weight PnPS-CRM conjugates low in free protein. In vivo animal studies were performed to compare PnuVax's PCV-13 to the commercially available PCV-13, Prevnar^®13 (Pfizer, USA). A boost dose was provided to all groups post-dose 1 at t = 14 days. Post-dose 2 results at t = 28 days showed that all 13 serotypes in PnuVax's PCV-13 were boostable. Per serotype IgG GMCs demonstrated that PnuVax's PCV-13 is immunogenic for all 13 serotypes, with 10 of the 13 serotypes statistically the same or higher than Prevnar^®13 post-dose 2. As a result, the novel polysaccharide-protein conjugates developed in this work are highly promising for use in human PCV development. The in vacuo conjugation technique applied in this work could also be readily adapted to develop many other conjugate vaccines.