Molecular characterization and epidemiology of Streptococcus pneumoniae serotype 24F in Denmark

by Kavalari ID, Fuursted K, Krogfelt KA, Slotved HC

Published in Scientific Reports, 02 April 2019

 

Since 2012, Denmark has observed an increase of invasive pneumococcal infections (IPD) due to Streptococcus pneumoniae serotype 24F. Researchers present epidemiological data on 24F IPD cases, and characterization of 48 24F clinical isolates based on clonal relationship, antimicrobial resistance (AMR) determinants and virulence factors. IPD surveillance data from (1999-2016) were used to calculate the incidence and age-distribution of serotype 24F IPD and the effect of pneumococcal conjugated vaccines (PCV). Characterization of forty-eight 24F isolates (14.7% of all 24F isolates from the period) was based on whole-genome sequencing analysis (WGS). The IPD cases of serotype 24F showed a significant increase (p < 0.05) for all age groups after the PCV-13 introduction in 2010. The majority of tested 24F isolates consisted of two MLST types, i.e. the ST72 and the ST162. Serotype 24F IPD increased in Denmark after the PCV-13 introduction in parallel with an increase of the ST162 clone. The genotypic penicillin binding protein (PBP) profile agreed with the phenotypical penicillin susceptibility. The virulence genes lytA, ply, piaA, piaB, piaC, rspB and the cpsA/wzg were detected in all 24F isolates, while the pspA and zmpC genes were absent.

 

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Maternal pertussis vaccination and its effects on the immune response of infants aged up to 12 months in the Netherlands: an open-label, parallel, randomised controlled trial

by Daan Barug, MD; Inge Pronk, BSc; Marlies A van Houten, MD; Florens G A Versteegh, PhD; Mirjam J Knol, PhD; Jan van de Kassteele, PhD; et al.

Published in The Lancet Infectious Diseases, 01 April 2019.

 

Maternal tetanus, diphtheria, and acellular pertussis (Tdap) vaccination offers protection for neonates against clinical pertussis until primary vaccinations, but maternal antibodies also interfere with infants' immune responses to primary vaccinations. Researchers investigated the effect of maternal Tdap vaccination on the pertussis antibody responses of infants starting primary vaccinations at age 3 months. In an open-label, parallel, randomised, controlled trial, pregnant women aged 18–40 years with a low risk of pregnancy complications were recruited through independent midwives at 36 midwife clinics in the Netherlands and received Tdap vaccination either at 30–32 weeks of pregnancy (maternal Tdap group) or within 48 h after delivery (control group). All term-born infants were vaccinated with the diphtheria, tetanus, and pertussis-inactivated poliomyelitis- Haemophilus influenzae type B-hepatitis B six-in-one vaccine and a ten-valent pneumococcal vaccine at 3 months, 5 months, and 11 months. Randomisation was done using a number generator in a 1:1 ratio and with sealed envelopes. Participants and clinical trial staff were not masked, but laboratory technicians were unaware of study group assignments. The primary endpoint was serum IgG pertussis toxin antibody concentrations at age 3 months. Cord blood and infant blood samples were collected at age 2 months, 3 months, 6 months, 11 months, and 12 months. Analysis was done by modified intention to treat with all randomly assigned participants in case a laboratory result was available. This trial is registered with ClinicaltTrialsRegister.eu (EudraCT 2012-004006-9) and trialregister.nl (NTR number NTR4314). The trial is now closed to new participants. Between Jan 16, 2014, and March 4, 2016, 118 pregnant women were enrolled into our study, with 58 in the maternal Tdap group and 60 in the control group. The geometric mean concentration (GMC) of pertussis toxin antibodies were higher in infants in the maternal Tdap group than in the control group infants at age 3 months (GMC ratio 16.6, 95% CI 10.9–25.2) and also significantly higher compared with control infants at age 2 months. After primary vaccinations, antibody concentrations for pertussis toxin, filamentous haemagglutinin, and pertactin were significantly lower at all time points in infants of the maternal Tdap group than in infants in the control group. No safety issues after maternal Tdap vaccination were encountered. In view of the high pertussis toxin antibody concentrations at age 3 months, maternal vaccination supports a delay of the first pertussis vaccination in infants until at least age 3 months. Maternal antibody interference affects antibody concentrations after primary and booster vaccinations. The clinical consequences of this interference remain to be established.  Article access can be found here.    
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Maternal immunisation to improve the health of HIV-exposed infants

by Angela M Bengtson, PhD; Alan M Sanfilippo, PhD; Brenna L Hughes, MD; David A Savitz, PhD.

Published in The Lancet Infectious Diseases, 01 April 2019.

 

 

HIV-exposed but uninfected (HEU) infants are at an increased risk of many infectious diseases that can contribute to the high mortality seen among HEU children. Maternal immunisation could be a promising strategy to reduce infections in HEU infants. However, very little research has explored the effect of HIV on the immunogenicity and effectiveness of vaccines given during pregnancy. Researchers reviewed available evidence on maternal immunisation among women living with HIV (WLWH) for all vaccines recommended, considered, or being investigated for routine or risk-based use during pregnancy. Of the 11 vaccines included, only three have been investigated in WLWH. Available evidence suggests that maternal HIV infection limits the immunogenicity of several vaccines, leaving HEU infants more susceptible to infection during their first few months of life. Whether maternal immunisation reduces the infectious morbidity and mortality associated with infectious diseases in HEU children remains unknown. Researchers concluded the Review by identifying future research priorities.  Article access can be found here.   
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Prediction and validation of immunogenic domains of pneumococcal proteins recognized by human CD4+ T-cells

by van de Garde MDB, van Westen E, Poelen MCM, Rots NY, van Els CACM

Published in Infection and Immunity, 25 March 2019. 

 

 

CD4+ T-cell mechanisms are implied in protection against pneumococcal colonization; however, their target antigens and function are not well defined. In contrast to high-throughput protein arrays for serology, basic antigen tools for CD4+ T-cell studies are lacking. Here researchers evaluate the potential of a bioinformatics tool in silico prediction of immunogenicity as a method to reveal domains of pneumococcal proteins targeted by human CD4+ T-cells.

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Changes in Serotype of Streptococcus pneumoniae After the Introduction of the 13-Valent Pneumococcal Vaccine in a Homogenous Population on Jeju Island

by Yoo JR, Heo ST, Oh H, Oh S, Kim YR, Lee KH

Published in Infection & Chemotherapy, March 2019. 

 

Researchers compared the serotypes of Streptococcus pneumoniae between the pre-pneumococcal conjugate vaccine (PCV)13 era and post-PCV13 era among homogenous inhabitants of an isolated South Korean island. A total of 325 S. pneumoniae strains were isolated. In the pre-PCV13 era, 19A/F, 15A/F, 19B, and 23A serotypes were identified. In the post-PCV13 era, 15 serotypes were identified. The 19F and 23A serotypes showed the highest prevalence in the pre- and post-PCV13 era, respectively. After PCV13 introduction, the PCV 13 serotype coverage rate was decreased (80.0% and 30.5% in the pre- and post-PCV13 eras, respectively), while the proportion of non-PCV 13 serotypes increased.

 

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