Epidemiology of culture-confirmed infections of Streptococcus pneumoniae (2012-2015) and nasopharyngeal carriage in children and households in Taiwan (2014-2015)

Epidemiology of non-vaccine serotypes of Streptococcus pneumoniae before and after universal administration of pneumococcal conjugate vaccines

The universal administration of pneumococcal conjugate vaccines (PCVs) had been demonstrated as an effective way to prevent Streptococcus pneumoniae infection. However, the immunity induced by PCVs protected against the infections caused by vaccine serotypes, which were usually more frequent than non-vaccine serotypes (NVTs). The prevalence and pathogenicity of NVTs after universal vaccination have caused widespread concern. We reviewed the epidemiology of non-PCV13 S. pneumoniae before and after PCV13 introduction, and explored the potential reasons for the spread of NVTs. Emerging and spreading NVTs can be regarded as the focus for future serotype epidemiological survey and vaccine optimization.AbbreviationsIPD: invasive pneumococcal disease PCV: pneumococcal conjugate vaccines VT: vaccine serotypeNVT: non-vaccine serotype.

Trend change of nasopharyngeal colonization with Streptococcus pneumoniae and non-typeable Haemophilus influenzae in children attending daycare centres: nationwide population-based study, South Korea 2014 and 2019

BACKGROUND

Nasopharyngeal (NP) colonization with Streptococcus pneumoniae and non-typeable Haemophilus influenzae (NTHi) is common in children, and may evolve as the source of invasive infections. In Korea, the pneumococcal conjugate vaccines (PCVs) were introduced >10 years ago, enabling the authors to study the effect of the vaccine in preventing carriage.

METHODS

NP swabs were taken and a household survey was conducted at daycare centres located in different regions of Korea in 2014 and 2019. Pneumococcal serotypes were identified using the Quellung method and sequencing. NTHi were identified based on pilA and bexA genes.

RESULTS

In total, 1460 NP swabs were obtained with pneumococcal carriage rates of 36.4-42.1% and NTHi carriage rates of 36.5-26.7%. Among children carrying pneumococci, a significant increase was seen in serotype 23A between 2014 and 2019 (from 12.6% to 22.0%; P=0.005). Children who had received PCV were at lower risk of vaccine-type carriage (2.9% vs 0.8%; P=0.005).

CONCLUSIONS

Between 2014 and 2019, the proportion of children carrying serotype 23A increased significantly, while the carriage rate of NTHi decreased. Continuous surveillance is needed to assess the long-term effects of the PCVs on carriage dynamics of pneumococcus and NTHi.

Divergent serotype distribution between children with otitis media and those without in the pneumococcal conjugate vaccine era

We investigated pneumococcal carriage between children ≦5 years old with otitis media (OM) and those without. Non-PCV13 serotypes were common in both groups; 19A remained the second most common serotype among children with OM despite high PCV13 coverage. This is important when considering a schedule with reduced vaccine doses or reduced valency, and the modification of pneumococcal immunization schedule should be followed up closely to monitor the result of protection against pneumococcal infections.

Disruption of the cpsE and endA Genes Attenuates Streptococcus pneumoniae Virulence: Towards the Development of a Live Attenuated Vaccine Candidate

The majority of deaths due to Streptococcus pneumoniae infections are in developing countries. Although polysaccharide-based pneumococcal vaccines are available, newer types of vaccines are needed to increase vaccine affordability, particularly in developing countries, and to provide broader protection across all pneumococcal serotypes. To attenuate pneumococcal virulence with the aim of engineering candidate live attenuated vaccines (LAVs), we constructed knockouts in S. pneumoniae D39 of one of the capsular biosynthetic genes, cpsE that encodes glycosyltransferase, and the endonuclease gene, endA, that had been implicated in the uptake of DNA from the environment as well as bacterial escape from neutrophil-mediated killing. The cpsE gene knockout significantly lowered peak bacterial density, BALB/c mice nasopharyngeal (NP) colonisation but increased biofilm formation when compared to the wild-type D39 strain as well as the endA gene knockout mutant. All constructed mutant strains were able to induce significantly high serum and mucosal antibody response in BALB/c mice. However, the cpsE-endA double mutant strain, designated SPEC, was able to protect mice from high dose mucosal challenge of the D39 wild-type. Furthermore, SPEC showed 23-fold attenuation of virulence compared to the wild-type. Thus, the cpsE-endA double-mutant strain could be a promising candidate for further development of a LAV for S. pneumoniae.

Genetic diversity of pneumococcal surface protein A (PspA) in paediatric isolates of non-conjugate vaccine serotypes in Japan

PURPOSE

Among the pneumococcal proteins, pneumococcal surface protein A (PspA) is considered the most promising candidate for a serotype-independent vaccine. This study aimed to investigate the serotype, genetic diversity of PspA, lineage (genotype) and drug resistance traits of pneumococcal isolates from paediatric patients.

METHODOLOGY

A total of 678 non-invasive pneumococcal isolates obtained from June to November 2016 were analysed. All isolates were characterized for PspA families, serotypes and macrolide resistance genes. Seventy-one representative isolates of non-vaccine serotypes (NVTs) were genetically analysed for the clade-defining region (CDR) of PspA, as well as multi-locus sequence typing (MLST).

RESULTS

The detection rate of NVTs was 87.9 % (n=596), including dominant NVTs 15A (14.5 %, n=98), 35B (11.8 %, n=80), 15C (9.3 %, n=63) and 23A (9.0 %, n=61). Most isolates (96.6 %) possessed macrolide resistance genes erm(B) and/or mef(A/E). PspA families 1, 2 and 3 were detected in 42.3, 56.6 and 0.6 % of isolates, respectively. Nucleotide sequences of CDR showed high identity (90-100 %) within the same PspA clade, although the CDR identity among different PspA families ranged from 53 to 69 %. All isolates of NVTs 23A, 10A, 34, 24, 22F/22A, 33F, 23B and 38 were from PspA family 1, while NVTs 35B, 15C, 15B and 11A/11D isolates were from family 2. In contrast, genetically distinct PspAs were found in NVTs 6C and 15A. PspA family 3/clade 6 was detected in only NVT serotype 37 isolates assigned to ST447 and ST7970, showing the mucoid phenotype.

CONCLUSION

The present study revealed the predominance of PspA families 1 and 2 in NVTs, and the presence of family 3 in serotype 37.

Non-typeable Streptococcus pneumoniae infection in a medical center in Taiwan after wide use of pneumococcal conjugate vaccine

BACKGROUND

Streptococcus pneumoniae is one of the most common pathogens to cause mucosal and invasive infection in humans. Most of the infection could be prevented through immunization by vaccines containing capsular polysaccharides but some infection may be caused by unencapsulated strains.

METHODS

Clinical isolates of S.pneumoniae from January 2012 to December 2015 at Chang Gung Memorial Hospital, Taiwan. Serotyping by PCR method was performed. Clinical and laboratory information of patients infected by non-typeable pneumococci (NTP) were collected and analyzed.

RESULTS

During the study period, 39 NTP isolates were identified. Most (21 of 39, 53.9%) were collected from purulent upper respiratory tract secretion. Others were from corneal abscess, sputum, and one from blood of a newborn. We recorded a 3.6-fold increase in the rate of isolation from 1.4% in 2012 to 5.0% in 2015 (p = 0.063). Co-infection was found in 24 cases; the major co-infecting pathogens included non-typeable Hemophilus influenzae, Moraxella catarrhalis, and Staphylococcus aureus. Most (39 of 40, 97.5%) of the isolates were susceptible to both penicillin and ceftriaxone. The dominant sequence type ST1106 and an emerging sequence type ST7502 were recognized.

CONCLUSIONS

A gradual increase of NTP infection was found in northern Taiwan in the pneumococcal conjugate vaccine era. Non-typeable pneumococci can cause respiratory and ophthalmological mucosal infection. Invasive infection can occur in newborns or young infants. Most of the isolates remained susceptible to penicillin and ceftriaxone.

Immunization with pneumococcal neuraminidases NanA, NanB and NanC to generate neutralizing antibodies and to increase survival in mice

Purpose. Pneumococcal virulence protein-based vaccines can provide serotype-independent protection against pneumococcal infections. Many studies, including clinical observational studies on Thomsen-Friedenrich antigen exposure and haemolytic uremic syndrome, defined the role of neuraminidases NanA, NanB and NanC in host-pneumococcus interaction. Since neuraminidases are major virulence proteins, they are potential targets for both vaccines and small molecule inhibitors. Here we explored the utility of three neuraminidases as protein vaccine antigens to generate neutralizing antibodies and to increase survival following pneumococcal infections.Methodology. Rabbits and mice were immunized subcutaneously with enzymatically active recombinant NanA, NanB and NanC as individual or a combination of the three neuraminidases. Antisera titres were determined by ELISA. Neuraminidase activity inhibition by antiserum was tested by peanut lectin and flow cytometry. Clinical isolates with serotype 3, 6B, 14, 15B, 19A and 23F were used to infect immunized mice by tail vein injection.Results/Key findings. Presence of high levels of IgG antibodies in antisera against NanA, NanB and NanC indicates that all of the three neuraminidases are immunogenic vaccine antigens. To generate potent NanA neutralizing antibodies, both lectin and catalytic domains are essential, whereas for NanB and NanC a single lectin domain is sufficient. Immunization with triple neuraminidases increased the survival of mice when intravenously challenged with clinical isolates of serotype 3 (40 %), 6B (60 %), 15B (60 %), 19A (40 %) and 23F (30 %).Conclusion. We recommend the inclusion of three pneumococcal neuraminidases in future protein vaccine formulations to prevent invasive pneumococcal infection caused by various serotypes.