Capacity of serotype 19A and 15B/C Streptococcus pneumoniae isolates for experimental otitis media: Implications for the conjugate vaccine

Non-vaccine Streptococcus pneumoniae serotypes are increasingly associated with disease. We evaluated isolates of the same sequence type (ST199) but different serotypes (15B/C, 19A) for growth in vitro, and pathogenic potential in a chinchilla otitis media model. We also developed a quantitative PCR (qPCR) assay to quantitatively assess each isolate, circumventing the need for selectable markers. In vitro studies showed faster growth of serotype 19A over 15B/C. Both were equally capable of colonization and middle ear infection in this model. Serotype 19A is included in new conjugate vaccine formulations while serotype 15B/C is not. Non-capsular vaccine targets will be important in disease prevention efforts.     

Characterization of Streptococcus pneumoniae invasive serotype 19A isolates recovered in Colombia

The aim of this study was to determine the molecular characterization of invasive penicillin non-susceptible Streptococcus pneumoniae serotype 19A isolates, collected in Colombia between 1994 and 2012. A total of 115 isolates serotype 19A were analyzed. Genetic relationship of 80 isolates with minimal inhibitory concentration (MIC) to penicillin ≥0.125 μg/was determined by pulsed-field gel electrophoresis (PFGE) and selected strains were studied by multilocus sequence typing (MLST). Among the 115 isolates, resistance to penicillin in meningitis was 64.2%, in non-meningitis 32.2% were intermediate and 1.1% were high resistance. The most frequent sequence types were ST320 (33.7%), ST276 (21.5%), and ST1118 (11.2%). Five isolates were associated with the Spain^9V-ST156 clone, and two isolates were related to Colombia^23F-ST338 clone. S. pneumoniae serotype 19A increased in Colombia was associated with the spread of isolates genetically related to ST320 and ST276, and emergence of capsular variants of worldwide-disseminated clones.     

Humoral immune response of a pneumococcal conjugate vaccine: capsular polysaccharide serotype 14-Lysine modified PspA

Polysaccharide-protein conjugates are so far the current antigens used for pneumococcal vaccines for children under 2 years of age. In this study, pneumococcal surface protein A (PspA) was used as a carrier protein for pneumococcal capsular polysaccharide serotype 14 as an alternative to broaden the vaccine coverage. PspA was modified by reductive amination with formaldehyde in order to improve the specificity of the reaction between protein and polysaccharide, inhibiting polymerization and the gel formation reaction. In the synthesis process, the currently used activator, 1-[3-(dimethylamine)propyl]-3-ethylcarbodiimide hydrochloride (EDAC) was substituted for 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMT-MM). BALB/c mice were immunized with either the PS14-mPspA conjugate or the co-administered components in a three dose regimen and sera from the immunized animals were assayed for immunity induced against both antigens: PS14 and mPspA. Modification of more than 70% of lysine residues from PspA (mPspA) did not interfere in the immune response as evaluated by the anti-PspA titer and C3 complement deposition assay. Sera of mice immunized with conjugated PS14-mPspA showed similar IgG titers, avidity and isotype profile as compared to controls immunized with PspA or mPspA alone. The complement deposition was higher in the sera of mice immunized with the conjugate vaccine and the opsonophagocytic activity was similar for both sera. Conjugation improved the immune response against PS14. The anti PS14 IgG titer was higher in sera of mice immunized with the conjugate than with co-administered antigens and presented an increased avidity index, induction of a predominant IgG1 isotype and increased complement deposition on a bacteria with a surface serotype 14. These results strongly support the use of PspA as carrier in a conjugate vaccine where both components act as antigens.     

First report of Streptococcus pneumoniae serotype 6D isolates from invasive infections

We report the first invasive Streptococcus pneumoniae isolates of serotype 6D and the first occurrence of this serotype in Europe. Till now, the appearance of serotype 6D pneumococci in nasopharyngeal carriage has been speculated to be associated with a selective pressure from vaccination with the conjugated 7-valent antipneumococcal vaccine. Our observations indicate that this serotype is present also among unvaccinated individuals in the population where mass infant vaccination has not yet been introduced. Importantly, these strains were isolated from invasive infections, indicating the full virulence potential of pneumococci belonging to serotype 6D and its importance for future vaccine formulations.     

Mucosal and systemic immunization with a novel attenuated pneumococcal vaccine candidate confer serotype independent protection against Streptococcus pneumoniae in mice

Despite the availability of effective vaccines, Streptococcus pneumoniae is still one of the major infectious diseases causing substantial morbidity and mortality in children under 5 years old. In this study, we demonstrate the protective efficacy of S. pneumoniae SPY1, a novel live attenuated vaccine strain against pneumococcal infection in murine models. This strain was characterized by defects in three important pneumococcal virulence factors including capsule, teichoic acids and pneumolysin. The lactate dehydrogenase assays and in vivo animal experiments demonstrated a significantly attenuated virulence and a reduced nasopharyngeal colonization for the SPY1 strain. We also show that mucosal and systemic immunization with the live SPY1 strain induced protective immune responses against pneumococci. Mucosal immunization with SPY1 offered better protection against colonization challenge with strains TIGR4 and serotype 19F than systemic SPY1 immunization. In invasive infection models, mucosal vaccination with the SPY1 strain conferred complete protection against D39 and clinical serotype 6B and 3 strains. Notably, intranasal vaccination with the SPY1 strain conferred superior protection against pneumococcal invasive disease compared with the commercial available vaccines. SPY1 strain was shown to elicit high levels of serotype-independent antibodies and a mixed cellular immune response. Besides, the SPY1 serum was able to passively protect mice against invasive challenge with D39 strain, indicating the protective effect of the antibody-mediated responses. Together, the SPY1 strain may be a promising live vaccine strain to protect pneumococcal infection.     

Global serotype distribution among Streptococcus pneumoniae isolates causing otitis media in children: Potential implications for pneumococcal conjugate vaccines

Acute otitis media (AOM) is the most common infection following pneumococcal colonization of the upper respiratory tract. Streptococcus pneumoniae causes 30–60% of AOM cases worldwide. However, not all pneumococcal serotypes cause disease and an association exists with nasopharyngeal colonization by certain serotypes and their propensity to cause AOM. This review examines the global serotype distribution relationship between pneumococcal serotypes and AOM in children aged <18 years and demonstrates that the most common pneumococcal serotypes causing AOM globally are 3, 6A, 6B, 9V, 14, 19A, 19F, and 23F.     

Changes in Streptococcus pneumoniae serotype distribution in invasive disease and nasopharyngeal carriage after the heptavalent pneumococcal conjugate vaccine introduction in Bogotá, Colombia

Background

In Bogotá, the Heptavalent Conjugate Vaccine (PCV7) was introduced into childhood immunization schedule since 2009. The aim of this study was to assess the changes in serotype distribution and penicillin susceptibility of Streptococcus pneumoniae isolates recovered from nasopharyngeal samples and invasive disease among children living in Bogotá, before and after PCV7 introduction.

Methods

Nasopharyngeal swabs were collected from healthy children aged between 12 and 18 months of age before (years 2005–2006) and after (2011) PCV7 introduction. Identification of S. pneumoniae was performed by multiplex PCR. Serotype was determined by PCR and Quellung reaction. Susceptibility to penicillin, ceftriaxone, trimethoprim-sulfamethoxazole, chloramphenicol, tetracycline and erythromycin was evaluated. In addition, distribution of serotypes and antimicrobial susceptibility before and after vaccine introduction among invasive isolates recovered from children ≤2 years old living in Bogotá was analyzed.

Results

Prevalence of pneumococcal nasopharyngeal carriage declined from 55.7% (137/246) in unvaccinated to 44.2% (87/197) (p = 0.01) in vaccinated children. The proportion of children carrying PCV7 serotypes decreased from 23.6% (58/246) to 7.6% (15/197) (p < 0.001). The decrease was counterbalanced by an increase in the proportion of non-PCV7 serotypes. The most prevalent among emerging serotypes were 15A, 15B, 15 C, 11A and 35B. Among IPD isolates, PCV7 serotypes decreased from 69.1% (235/340) in 2005/2009 to 38.0% (32/84) in 2010/2011 (p < 0.001). The increase of non-PCV7 serotypes was significant. Resistance to penicillin among invasive isolates recovered from meningitis decreased from 41.1% (30/73) in the pre-vaccine period to 14.2% (2/14) in post-vaccine period (p = 0.02).

Conclusions

A decrease in the prevalence of pneumococcal nasopharyngeal carriage following the introduction of PCV7 vaccine, have been overshadowed by an important surge in the prevalence of non-PCV7 serotypes. Systematic surveillance combining nasopharyngeal carriage surveys and IPD detection could help in evaluating the impact of conjugate vaccines.     

Re: Global serotype distribution among Streptococcus pneumoniae isolates causing otitis media in children: Potential implications for pneumococcal conjugate vaccines

Acute otitis media (AOM) is one of the most commonly diagnosed childhood infections. Analysis of global serotype distribution among Streptococcus pneumonia isolates causing otitis media in children may improve coverage of future pneumococcal conjugate vaccines. Serotypes like 3 or 19A should not only be included in future vaccine formulations but they should preferably protect against these serotypes. To construct future AOM vaccine with higher vaccine efficacy also other pathogens causing AOM need to be taken into consideration.     

Streptococcus pneumoniae invasive infections in Burkina Faso, 2007 to 2011

Objective

We had for aim to determine the epidemiology of meningeal and lung invasive infections due to Streptococcus pneumoniae in Burkina Faso.

Material and methods

We screened for S. pneumoniae with the usual bacteriology techniques and with real time polymerase chain reaction (rt-PCR) in 7917 samples of cerebrospinal fluid (CSF) and pleural fluid (PF) collected in the Ouagadougou Yalgado Ouedraogo Teaching Hospital, from 2007 to 2011.

Results

S. pneumoniae was identified in 476 (6%) samples including 455 (5.7%) in CSF and 21 (0.3%) in PF. Sixty-seven percent of invasive infections occurred in patients 15 years of age or less, without any significant sex ratio difference. The infections occurred most frequently between January and August, with the first and most important peak between January and May (dry season) and the second peak between June and August (at the beginning of rain season). The introduction of rt-PCR proved the under diagnosing of invasive infections by usual bacteriological methods (latex agglutination assay and culture).

Conclusion

Invasive pneumococcal infections occur mainly in patients 15 years of age or less, without any difference in sex ratio and with peaks in the dry season. Vaccinal schedules should include all age ranges in Burkina Faso.     

Serotype prevalence and antibiotic resistance in Streptococcus pneumoniae clinical isolates among global populations

Streptococcus pneumoniae remains a leading cause of disease in children and adults. Serotypes differ in invasiveness, virulence, and antibiotic resistance; therefore, serotype surveillance is necessary to monitor the burden of pneumococcal disease, especially in the setting of pneumococcal vaccination programs. The Tigecycline Evaluation Surveillance Trial, (TEST), is an on-going global antibiotic susceptibility surveillance program. Serotypes and antibiotic susceptibilities of 2173 invasive S. pneumoniae in this existing database during 2004–2008 were evaluated. Worldwide, serotypes 19A (28%), 19F (10%) and 14 (9%) were the most common in children under 5 years. In adults over 16 years, 19A (13%), 3, 6A and 7F (all 7%) were most common. Serotypes 19A, 6A, 19F, 6B, 15A, 9V, and 14 exhibited significantly higher levels of erythromycin resistance (P < 0.05), while 19A, 19F, 35B, 6A, 6B, 23A, 9V, 15A, and 14 demonstrated higher rates of penicillin resistance (P < 0.05). This analysis of an existing pathogen database provides a snapshot of global serotype data and describes the consequential issue of antibiotic resistance in specific serotypes, many of which are increasingly common causes of invasive pneumococcal disease.     

Control of Streptococcus pneumoniae serotype 5 epidemic of severe pneumonia among young army recruits by mass antibiotic treatment and vaccination

During an outbreak of severe pneumonia among new army recruits, an epidemiological investigation combined with repeated nasopharyngeal/oropharyngeal cultures from sick and healthy contacts subjects was conducted. Fifteen pneumonia cases and 19 influenza-like illness cases occurred among 596 recruits over a 4-week period in December 2005. Pneumonia attack rates reached up to 5.5%. A single pneumococcus serotype 5 clone was isolated from blood or sputum cultures in 4 patients and 30/124 (24.1%) contacts. Immunization with 23-valent polysaccharide vaccine supplemented with a 2-dose azithromycin mass treatment rapidly terminated the outbreak. Carriage rates dropped to <1%, 24 and 45 days after intervention.     

Effect of vaccination with pneumococcal capsular polysaccharides conjugated to Haemophilus influenzae-derived protein D on nasopharyngeal carriage of Streptococcus pneumoniae and H. influenzae in children under 2 years of age

Following primary and booster vaccination with an 11-valent pneumococcall protein D conjugate vaccine there was a 42.8% (95% CI: −16.7 to 71.9, ns) reduction in the carriage of Streptococcus pneumoniae vaccine serotypes and a 42.6% (95% CI: 1.3–66.6) reduction in the carriage of Haemophilus influenzae identified by standard microbiological techniques. When PCR and immunoblot assays were used to further improve specificity of non-typeable H. influenzae strain identification, carriage of H. influenzae was still reduced with 38.6% (95% CI: −6.3 to 64.6, ns). Reduction of acute otitis media (AOM) episodes preceded the impact on carriage. These data provide further support of the functional role of the protein D immunity.     

Co-colonization by Haemophilus influenzae with Streptococcus pneumoniae enhances pneumococcal-specific antibody response in young children

Background

Streptococcus pneumoniae (Spn), Haemophilus influenzae (Hi) and Moraxella catarrhalis (Mcat) are common bacterial pathogens of respiratory infections and common commensal microbes in the human nasopharynx (NP). The effect of interactions among theses bacteria during co-colonization of the NP on the host immune response has not been evaluated. The objective of this study was to assess the impact of co-colonization by Hi or Mcat on the systemic antibody response to vaccine protein candidate antigens of Spn and similarly the impact of co-colonization by Spn and Mcat on antibody responses to Hi vaccine protein candidate antigens.

Methods

Serum samples were collected from healthy children at 6, 9, 15, 18, and 24 months of age when they were colonized with Spn, Hi, Mcat or their combinations. Quantitative ELISA was used to determine serum IgA and IgG against three Spn antigens and three Hi antigens, and as well as whole cells of non-typeable (NT) Spn and Hi.

Results

NP colonization by Spn increased serum IgA and IgG titers against Spn antigens PhtD, PcpA and PlyD and whole cells of NTSpn, and co-colonization of Hi or Mcat with Spn resulted in further increases of serum pneumococcal-specific antibody levels. NP colonization by Hi increased serum IgA and IgG titers against Hi antigens P6, Protein D and OMP26 and whole cells of NTHi, but co-colonization of Spn or Mcat with Hi did not result in further increase of serum NTHi-specific antibody levels.

Conclusion

Co-colonization of Hi or Mcat with Spn enhances serum antibody response to NTSpn whole cells and Spn vaccine candidate antigens PhtD, PcPA and PlyD1. Co-colonization appears to variably modulate pathogen species-specific host adaptive immune response.     

A Phase I,dose-escalation trial in adults of three recombinant attenuated Salmonella Typhi vaccine vectors producing Streptococcus pneumoniae surface protein antigen PspA

Background

Live, attenuated, orally-administered Salmonella strains are excellent vectors for vaccine antigens and are attractive as vaccines based on previous use of S. Typhimurium in animals. A Phase I dose escalation trial was conducted to evaluate the safety and immunogenicity of three newly constructed recombinant attenuated Salmonella enterica serovar Typhi vaccine (RASV) vectors synthesizing Streptococcus pneumoniae surface protein A (PspA).

Methods

The 3 S. Typhi strains used as vectors to deliver PspA were S. Typhi ISP1820; S. Typhi Ty2 RpoS⁻; and S. Typhi Ty2 RpoS⁺. Sixty healthy adults (median age 25.2 years) were enrolled into 4 Arms (total 15 subjects per Arm); within each Arm, subjects were randomized 1:1:1 into 3 Groups of 5. All subjects in the same Group received the same vaccine vector, and all subjects in the same Arm received the same titer of vaccine (10⁷, 10⁸, 10⁹ or 10¹⁰ CFU). Adverse events, safety, shedding, and IgG and IgA titers against Salmonella outer membrane proteins (OMPs), lipopolysaccharide (LPS) and PspA were evaluated.

Results

In the highest dose group, no subject experienced severe reactions or serious adverse events. Most adverse events were mild; one subject had a positive blood culture. No subject shed vaccine in stool. No statistically significant differences for post vaccination ELISA or ELISPOT results between Groups were detected. However, a limited number of ≥4 fold increases from baseline for IgA anti-OMPs, IgA and IgG anti-LPS, and IgA anti-PspA occurred for a few individuals as measured by ELISA, and IgA anti-OMPs as measured by ELISPOT assay.

Conclusions

All three S. Typhi vectored pneumococcal vaccines were safe and well-tolerated. Immunogenicity was limited possibly due to pre-existing high antibody titers prior to vaccination. Increases in IgA were most often observed.     

Identification of a surface protective antigen,HP0197 of Streptococcus suis serotype 2

Streptococcus suis serotype 2 (SS2) is a porcine and human pathogen with adhesive and invasive properties. As traditional inactive vaccine has obvious shortcomings, to identify protective antigens would undoubtedly contribute to the development of novel vaccines. HP0197 has been identified as immunogenic protein in the previous study but its protective efficacy was not clear. In the present study, the purified recombinant HP0197 protein could elicit a significant humoral antibody response and could confer significant protection against challenge with lethal dose of SS2 in mice and pigs. In addition, the hyperimmune sera against HP0197 could efficiently kill the bacteria in the opsonized phagocytosis test and conferred significant protection against SS2 infection in the experiment of passive immunization. The present study suggests with strong evidence that the identified protective antigen would be a novel and an effective vaccine candidate for SS2.     

2012—2017年某院儿童肺炎链球菌感染分布特点及耐药性

目的了解某院儿童肺炎链球菌感染分布特点、耐药性及其变化趋势。方法对该院2012年1月—2017年12月儿科住院患儿的痰、血、脑脊液标本进行分离培养和细菌鉴定,参照美国临床实验室标准化协会(CLSI)文件M100-S28标准进行药敏试验和结果判定,对数据进行统计分析。结果共分离2384株肺炎链球菌,男性占54.32%,女性占45.68%;0.5~3岁年龄段患儿占63.38%,≤0.5岁者占21.10%,>3岁者占15.52%。肺炎链球菌占所有分离细菌的18.08%,按季度统计其占细菌分离的比率,四季度(20.62%,839/4068)>一季度(18.77%,762/4059)>二季度(18.42%,557/3024)>三季度(11.11%,226/2034),但随季度变化的差异在逐步缩小。肺炎链球菌对红霉素、复方磺胺甲口恶唑、克林霉素、四环素耐药率高(73.21%~99.62%),对左氧氟沙星、氯霉素、头孢呋辛、头孢噻肟、阿莫西林、青霉素的耐药率较低(0.19%~33.92%),未发现对万古霉素、奎奴普丁/达福普汀、利奈唑胺、莫西沙星耐药的肺炎链球菌。结论肺炎链球菌主要分离于呼吸道感染患儿,≤3岁儿童是感染主体。肺炎链球菌分离率随季度变化的差异正在逐步缩小,其时间分布特点越来越不明显。阿莫西林、青霉素可作为治疗儿童肺炎链球菌感染的一线药物。     

Changes in the incidence of Streptococcus pneumoniae bacteremia and its serotypes over 10 years in one hospital in South Korea

Here, we examined the distribution of pneumococcal serotypes and the antibiotic susceptibility of Streptococcus pneumoniae in clinical blood isolates. The serotypes of 91 S. pneumoniae blood isolates, collected from January 2003 to March 2014, were identified by multiplex PCR and sequencing. The most common serotypes were 19F, 19A, 3, 4, and 14, accounting for 53.8% of the total. The serotype coverage rates of pneumococcal conjugated vaccine (PCV) 7, PCV10, and PCV13 were different during three test periods: 38.7%, 70.9%, and 93.5% in period I (2003–2005), 46.8%, 50.0%, and 75.0% in period II (2006–2008), and 28.5%, 32.1%, and 64.2% in period III (2009–2014), respectively. By contrast, the number of non-PCV13 serotypes increased from 6.4% in period I to 25% and 35.7% in periods II and III, respectively. The susceptibility of non-PCV13 serotypes to antimicrobial agents (penicillin, erythromycin, cefotaxime, and meropenem) was higher than that of PCV serotypes. In particular, non-PCV13 serotypes showed 100% and 95% susceptibility to penicillin and cefotaxime, respectively. Serotypes 19A and 19F showed high prevalence (79.1%) among 24 multi-drug resistant (MDR) isolates. Notably, all serotype 19A isolates were MDR. From January 2003 to March 2014, the proportion of non-PCV13 serotype pneumococci in blood isolates increased whereas the coverage rate of PCV13 decreased. Effective pneumococcal vaccines are required to protect against MDR serotype 19A isolates and the increasing number of non-PCV13 serotypes.     

Design questions for Streptococcus pneumoniae vaccine trials with a colonisation endpoint

Evaluation of vaccine efficacy for protection against colonisation (VE_col) with Streptococcus pneumoniae and other bacterial pathogens is often based on a cross-sectional study design, in which only one nasopharyngeal sample is obtained per study subject. Here we investigate the feasibility of this study design by investigating a number of practical design problems. Specific questions are related to the timing of colonisation measurement with respect to the time of vaccination, the adjustment for the within-host replacement of vaccine-type colonisation by the non-vaccine type pneumococci, and the impact of multiple serotype colonisation on VE_col estimation. We also discuss the issue of choosing the control vaccine, including comparison of two active pneumococcal vaccines, as well as the sample size and the statistical power of colonisation endpoint trials. In addition, the statistical design with the specific aim to include information about VE_col in the licensure process of new pneumococcal vaccine products is discussed.     

肺炎链球菌感染相关溶血尿毒综合征1例及文献复习

目的了解儿童肺炎链球菌感染相关溶血尿毒综合征(SP-HUS)的临床特点及治疗转归。方法回顾性分析1例采用血浆置换(PE)治疗SP-HUS患儿的临床资料,并查阅相关文献进行分析。结果患儿男性,3岁3个月,因咳嗽10 d,加重伴发热、胸痛3 d为代主诉入院,具有溶血尿毒综合征(HUS)三联征,肺泡灌洗液培养和痰培养均为肺炎链球菌,诊断SP-HUS成立,经积极抗感染同时联合3次连续性肾替代治疗(CRRT)和2次PE治疗,患儿病情逐渐好转出院。文献复习发现,国内报道的两例SP-HUS患儿年龄分别为1岁6个月、3岁,均以肺炎起病,经积极抗感染和支持对症治疗,均好转出院。结论对于肺炎链球菌感染患儿应加强重视,警惕并发HUS,婴幼儿为高危人群,综合治疗是治疗成功的关键。