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

Streptococcus pneumoniae serotype 19A in Latin America and the Caribbean: a systematic review and meta-analysis, 1990-2010

BACKGROUND

Pneumococcal conjugate vaccines (PCVs) are in the process of implementation in Latin America. Experience in developed countries has shown that they reduce the incidence of invasive and non-invasive disease. However, there is evidence that the introduction of PCVs in universal mass vaccination programs, combined with inappropriate and extensive use of antibiotics, could be associated to changes in non-PCV serotypes, including serotype 19A. We conducted a systematic review to determine the distribution of serotype 19A, burden of pneumococcal disease and antibiotic resistance in the region.

METHODS

We performed a systematic review of serotype 19A data from observational and randomized clinical studies in the region, conducted between 1990 and 2010, for children under 6 years. Pooled prevalence estimates from surveillance activities with confidence intervals were calculated.

RESULTS

We included 100 studies in 22 countries and extracted data from 63. These data reported 19733 serotyped invasive pneumococcal isolates, 3.8% of which were serotype 19A. Serotype 19A isolates were responsible for 2.4% acute otitis media episodes, and accounted for 4.1% and 4.4% of 4,380 nasopharyngeal isolates from healthy children and in hospital-based/sick children, respectively. This serotype was stable over the twenty years of surveillance in the region. A total of 53.7% Spn19A isolates from meningitis cases and only 14% from non meningitis were resistant to penicillin.

CONCLUSIONS

Before widespread PCV implementation in this region, serotype 19A was responsible for a relatively small number of pneumococcal disease cases. With increased use of PCVs and a greater number of serotypes included, monitoring S. pneumoniae serotype distribution will be essential for understanding the epidemiology of pneumococcal disease.

Early-life and contemporaneous nutritional and environmental predictors of antibody response to vaccination in young Gambian adults

Recent research links nutritional exposures early in life with alterations in functional immunity that persist beyond childhood. Here we investigate predictors of antibody response to polysaccharide vaccines in a cohort of Gambian adults with detailed records from birth and early infancy available. 320 adults were given a single dose of a Vi polysaccharide vaccine for Salmonella typhi and a 23-valent capsular polysaccharide pneumococcal vaccine. Anti-Vi antibody levels and antibodies against 4 pneumococcal serotypes (1, 5, 14 and 23F) were measured in serum samples collected at baseline and then 14 days following vaccination and compared to data available from birth and early infancy. Post-vaccination antibody titres to serotype 14 of the pneumococcal vaccine were negatively associated with rate of growth from birth to three months of age, infant weight at 12 months of age and season of birth, but no other associations were observed with early-life exposures. The strongest predictor of antibody levels was pre-vaccination antibody titres, with adult height and serum neopterin levels at time of vaccination also implicated. The current study does not support the hypothesis that nutritional exposures early in life consistently compromise antibody response to polysaccharide vaccines administered in young adulthood.

Prevention of acute otitis media using currently available vaccines

Acute otitis media (AOM) is common in infants and children. Although approximately two-thirds of cases are due to bacteria, almost all of the episodes are preceded by upper respiratory viral infection. Several viruses, among which respiratory syncytial virus is the most common, are involved in the determination of AOM. However, a significant number of AOM cases are associated with influenza infection, and influenza viruses are among the most frequently found respiratory viruses in the middle ear fluid during an acute episode of AOM. Consequently, influenza vaccination may have a favorable impact on the incidence and course of AOM. Moreover, as Streptococcus pneumoniae is one of the leading AOM bacterial pathogens and it is well known that influenza virus infection predisposes to pneumococcal infection, there is a further reason to suggest the use of influenza vaccine to reduce the risk of AOM. On the other hand, the administration of pneumococcal conjugate vaccine is considered per se a possible means of reducing the incidence of the disease. However, although a number of studies have measured the impact of both vaccines on AOM, it is still not known whether (and to what extent) they are really effective, nor what impact the more recently licensed vaccines may have. The aim of this review is to examine the clinical impact of vaccinations on AOM.

Virulence of Streptococcus pneumoniae serotype 6C in experimental otitis media

Increases in colonization with serotypes of Streptococcus pneumoniae not contained within the 7-valent pneumococcal conjugate vaccine (PCV) have been reported among children following introduction. Serotype 6C has emerged as prevalent in nasopharyngeal colonization and acute otitis media (AOM), though it is uncommonly recovered from children with invasive pneumococcal disease. Vaccine serotypes within PCV7 have been replaced by nonvaccine serotypes without significant changes in the overall carriage rate. We hypothesize 1) that serotypes vary in their ability to evade host defenses and establish AOM following colonization and 2) the observed reduction in pneumococcal otitis results from a reduced disease potential by some 'replacement serotypes'. We compared the capacity of S. pneumoniae serotypes 6C and 19A to produce experimental otitis media (EOM) in a chinchilla model. The proportion of chinchillas that developed culture positive EOM and density of middle ear infection was evaluated. EOM was found in 28/82 (34%) ears challenged with 6C compared to 13/18(72.2%) with 19A [p = 0.0003]. When disease due to 6C did occur, it was characterized by low-density infection. Our findings demonstrate that challenge with serotype 6C results in EOM less frequently than 19A. These data support the need for greater knowledge regarding differences among serotypes to produce AOM.

Non-capsulated and capsulated Haemophilus influenzae in children with acute otitis media in Venezuela: a prospective epidemiological study

Background

Non-typeable Haemophilus influenzae (NTHi) and Streptococcus pneumoniae are major causes of bacterial acute otitis media (AOM). Data regarding AOM are limited in Latin America. This is the first active surveillance in a private setting in Venezuela to characterize the bacterial etiology of AOM in children < 5 years of age.

Methods

Between December 2008 and December 2009, 91 AOM episodes (including sporadic, recurrent and treatment failures) were studied in 87 children enrolled into a medical center in Caracas, Venezuela. Middle ear fluid samples were collected either by tympanocentesis or spontaneous otorrhea swab sampling method. Standard laboratory and microbiological techniques were used to identify bacteria and test for antimicrobial resistance. The results were interpreted according to Clinical Laboratory Standards Institute (CLSI) 2009 for non-meningitis isolates. All statistical analyses were performed using SAS 9.1 and Microsoft Excel (for graphical purposes).

Results

Overall, bacteria were cultured from 69.2% (63 of the 91 episodes); at least one pathogen (S. pneumoniae, H. influenzae, S. pyogenes or M. catarrhalis) was cultured from 65.9% (60/91) of episodes. H. influenzae (55.5%; 35/63 episodes) and S. pneumoniae (34.9%; 22/63 episodes) were the most frequently reported bacteria. Among H. influenzae isolates, 62.9% (22/35 episodes) were non-capsulated (NTHi) and 31.4% (11/35 episodes) were capsulated including types d, a, c and f, across all age groups. Low antibiotic resistance for H. influenzae was observed to amoxicillin/ampicillin (5.7%; 2/35 samples). NTHi was isolated in four of the six H. influenzae positive samples (66.7%) from recurrent episodes.

Conclusions

We found H. influenzae and S. pneumoniae to be the main pathogens causing AOM in Venezuela. Pneumococcal conjugate vaccines with efficacy against these bacterial pathogens may have the potential to maximize protection against AOM.

Pathogens implicated in acute otitis media failures after 7-valent pneumococcal conjugate vaccine implementation in France: distribution, serotypes, and resistance levels

BACKGROUND

Before 7-valent pneumococcal conjugate vaccine (PCV7) implementation in France, several studies had described the microbiology of acute otitis media (AOM) treatment failures. The causative pathogens were Streptococcus pneumoniae (Sp) followed by nontypable Haemophilus influenzae (NTHi). The aim of this study was to describe the epidemiology of pathogens involved in AOM treatment failures or recurrences.

METHODS

This French multicentric prospective study enrolled 143 children with AOM treatment failure between 2007 and 2009 observed by 8 ear, nose, and throat specialists. Failure was defined as the persistence of AOM symptoms after at least 48 hours of antibiotic therapy or their recurrence within 4 days after the end of treatment. Standardized history and physical examination findings were recorded, and culture of middle ear fluid (MEF) was obtained.

RESULTS

Mean age was 16.9 ± 9.9 months (median, 13.7). Eighty-eight percent of children had received more than 1 dose of PCV7, and 70.6% attended day care. The most common antibiotic used at the time of treatment failure or recurrence was a combination of amoxicillin and clavulanate (51.1%). Bacteriologic sampling demonstrated that in 35% of cases (n=50), no otopathogen was cultured at the time of treatment failure or recurrence. Similar proportions of Sp and NTHi were observed in the 86 patients (60.1%) from whom only a single species was recovered from MEF (46.5% for Sp, n=40 and 45.3% for NTHi, n=39). Among Sp strains, 4.4% were penicillin susceptible, 77.8% were penicillin intermediate, and 17.8% were fully penicillin resistant, and serotype 19A represented 84.5% of all serotypes detected. Among NTHi isolates, 15.5% (n=7) were β-lactamase-producing strains (including 2 strains with only this mechanism of resistance), and strains with reduced susceptibility by changes in protein binding to penicillin (β-lactamase-negative ampicillin resistant strains) represented 35.5% of cases. Among the 50 sterile MEF samples, polymerase chain reaction was performed in 32, of which 4 were positive for HI, 3 for Sp, and 3 for both.

CONCLUSIONS

Among children with AOM treatment failures in France, Sp and NTHi were equally distributed; 19A was the main Sp serotype, and the main resistance mechanism for NTHi was β-lactamase-negative ampicillin resistance.

Pneumococcal disease manifestation in children before and after vaccination: what's new?

Pneumococcal infections remain a relevant cause of morbidity and mortality in children, especially in countries where vaccination has not been introduced. In contrast to the common belief by many pediatricians, the most important pneumococcal infections are of the respiratory tract and not invasive diseases. The recent pandemic of the H1N1 virus prompted studies to better understand the interaction between the influenza virus, Streptococcus pneumoniae, and pneumonia outcomes. Radiological findings of bacteremic pneumonia have been well investigated and besides the typical alveolar consolidation, a broad spectrum of atypical patterns has been reported. Molecular techniques, such as real-time polymerase chain reaction (PCR), can improve the detection of S. pneumoniae in sterile fluids, mainly in regions where previous antibiotic therapy is a common practice. In the post vaccination era, new manifestations of pneumococcal invasive disease, such as hemolytic uremic syndrome, have increased in association with parapneumonic empyema. Moreover, serotypes not included in PCV7, particularly serotypes 1, 3, 5, 7F, and 19A, have been among the most common isolates in pneumococcal disease. In Latin America, pneumococcal primary peritonitis has been described as an important clinical syndrome in a growing proportion of patients, mainly in girls. The development of newer and more specific diagnostic markers to distinguish bacterial and viral pneumonia are urgently sought, and will be especially pertinent after the introduction of pneumococcal conjugate vaccines with expanded serotypes. Such markers would minimize inappropriate diagnosis of false positive cases and treatment with antibacterial agents, while increasing positive predictive values for diagnosis of bacterial pneumonia. The extension of serotype coverage with the new conjugate vaccines is promising for pneumococcal infections and coverage against antibiotic-resistant strains.

The future of pneumococcal disease prevention

Pneumococcal disease (PD) is the leading cause of vaccine preventable deaths in children <5 years of age worldwide, with most of the deaths occurring in the developing world. Prevention of PD in children has been achieved by vaccination with pneumococcal conjugate vaccine (PCV), the basis for which is induction of a protective antibody response against the bacterial polysaccharide capsule. Conjugation of the polysaccharide capsule to a protein carrier enables the generation of an immunologic response to the vaccine in young children, leading to protection against infection. The heptavalent PCV, which contains 7 of the 93 known pneumococcal serotypes (4, 6B, 9V, 14, 18C, 19F, 23F) was the first PCV available, licensed in the US in 2000 and subsequently in many countries worldwide, including Latin American and Caribbean countries. Since its introduction, PCV7 has been documented effective for reducing invasive PD mortality and burden, as well as that of pneumonia and otitis media. Additionally, PD caused by the vaccine serotypes has decreased in the unimmunized population due to herd immunity induced by PCV7. Despite this success, significant disease burden still exists globally due to serotypes not included in PCV7. Currently there are 2 new PCVs that have been approved for use in children, a 10-valent vaccine (includes PCV7 serotypes plus serotypes 1, 5 and 7F) and a 13-valent vaccine (includes PCV7 serotypes plus serotypes 1, 3, 5, 6A, 7F and 19A). The selection of new serotypes to be included was based on importance of these serotypes as causes of PD. An additional 15-valent vaccine (includes PCV 7 serotypes plus serotypes 1, 3, 5, 6A, 7F, 19A, 22F and 33F) is undergoing clinical trial testing. In view of the 93 serotypes that are currently known, it seems clear that vaccines with greater coverage, likely based on proteins common to all serotypes, will be needed in the future. Technical and regulatory challenges to the development and approval of newer PCVs include a need for licensing criteria of common protein vaccines, establishment of correlates of protection for disease manifestations other than invasive disease, comparative efficacy data, and clinical trial testing of concomitant immunization of higher valency PCVs with other vaccines.

Acute bacterial meningitis in infants and children: epidemiology and management

Acute bacterial meningitis (ABM) continues to be associated with high mortality and morbidity, despite advances in antimicrobial therapy. The causative organism varies with age, immune function, immunization status, and geographic region, and empiric therapy for meningitis is based on these factors. Haemophilus influenzae type b (Hib), Streptococcus pneumoniae, and Neisseria meningitidis cause the majority of cases of ABM. Disease epidemiology is changing rapidly due to immunization practices and changing bacterial resistance patterns. Hib was the leading cause of meningitis in children prior to the introduction of an effective vaccination. In those countries where Hib vaccine is a part of the routine infant immunization schedule, Hib has now been virtually eradicated as a cause of childhood meningitis. Vaccines have also been introduced for pneumococcal and meningococcal diseases, which have significantly changed the disease profile. Where routine pneumococcal immunization has been introduced there has been a reported increase in invasive pneumococcal disease due to non-vaccine serotypes. In those parts of the world that have introduced conjugate meningococcal vaccines, there has been a significant change in the epidemiology of meningococcal meningitis. As a part of the United Nations Millennium Development Goal 4, the WHO has introduced a new vaccine policy to improve vaccine availability in resource poor countries. In addition, antibiotic resistance is an increasing problem, especially with pneumococcal infection. Effective treatment focuses on early recognition and use of effective antibiotics. This review will attempt to focus on the changing epidemiology of ABM in pediatric patients due to vaccination, the changing patterns of infecting bacterial serotypes due to vaccination, and on antibiotic resistance and its impact on current management strategies.

Novel protein-based pneumococcal vaccines administered with the Th1-promoting adjuvant IC31 induce protective immunity against pneumococcal disease in neonatal mice

Streptococcus pneumoniae is responsible for many vaccine-preventable deaths, annually causing around 1 million deaths in children younger than 5 years of age. A new generation of pneumococcal vaccines based on conserved proteins is being developed. We evaluated the immunogenicities and protective efficacies of four pneumococcal protein vaccine candidates, PcsB, StkP, PsaA, and PspA, in a neonatal mouse model. Mice were immunized three times and challenged intranasally with virulent pneumococci. All four proteins were immunogenic in neonatal mice, and antibody (Ab) responses were significantly enhanced by the novel adjuvant IC31, which consists of an antibacterial peptide (KLKL5KLK) and a synthetic oligodeoxynucleotide, ODN1a, that signals through Toll-like receptor 9 (TLR9). Two single proteins, StkP and PspA, combined with IC31 significantly reduced pneumococcal bacteremia but had no effects on lung infection. Three proteins, PcsB, StkP, and PsaA, were evaluated with alum or IC31. IC31 enhanced Ab responses and avidity to all three proteins, whereas alum enhanced Ab responses and avidity to StkP and PsaA only. Mice receiving the trivalent protein formulation with IC31 had significantly reduced bacteremia and lung infection compared to unvaccinated mice, but the level of protection was dependent on the dose of IC31. When PspA was added to the trivalent protein formulation, the dose of IC31 needed to obtain protective immunity could be reduced. These results demonstrate that a novel pneumococcal protein-based vaccine is immunogenic at an early age of mice and emphasize the benefits of using a combination of conserved proteins and an effective adjuvant to elicit potent protective immunity against invasive pneumococcal disease.

Increase in serotype 19A prevalence and amoxicillin non-susceptibility among paediatric Streptococcus pneumoniae isolates from middle ear fluid in a passive laboratory-based surveillance in Spain, 1997-2009

BACKGROUND

Conjugate vaccines, such as the 7-valent conjugate vaccine (PCV7), alter serotype nasopharyngeal carriage, potentially increasing cases of otitis media by non-vaccine serotypes.

METHODS

All paediatric middle ear fluid (MEF) isolates received in the Spanish Reference Laboratory for Pneumococci through a passive, laboratory-based surveillance system from January 1997 to June 2009 were analysed. Data from 1997 to 2000 were pooled as pre-vaccination period. Trends over time were explored by linear regression analysis.

RESULTS

A total of 2,077 isolates were analysed: 855 belonging to PCV7 serotypes, 466 to serotype 19A, 215 to serotype 3, 89 to serotype 6A and 452 to other serotypes (< 40 isolates each). Over time, there has been a decreasing trend for PCV7 serotypes (R(2) = 0.944; p < 0.001, with significant decreasing trends for serotypes 19F, 14, 23F and 9V), and increasing trends for serotype 19A (R(2) = 0.901; p < 0.001), serotype 3 (R(2) = 0.463; p = 0.030) and other non-PCV7 serotypes (R(2) = 0.877; p < 0.001), but not for serotype 6A (R(2) = 0.311; p = 0.094). Considering all isolates, amoxicillin non-susceptibility showed an increasing trend (R(2) = 0.528; p = 0.017). Regarding serotype 19A, increasing trends in non-susceptibility to penicillin (R(2) = 0.726; p = 0.001), amoxicillin (R(2) = 0.804; p < 0.001), cefotaxime (R(2) = 0.546; p = 0.005) and erythromycin (R(2) = 0.546; p = 0.009) were found, with amoxicillin non-susceptibility firstly detected in 2003 (7.4%) and increasing up to 38.0% in 2009. In PCV7 serotypes (which prevalence decreased from 70.7% during 1997-2000 to 10.6% in 2009) amoxicillin non-susceptibility rates showed an increasing trend (R(2) = 0.702; p = 0.002). However, overall, amoxicillin non-susceptibility (≈25% in 2008-9) could be mainly attributed to serotype 19A (> 35% isolates) since PCV7 strains represented < 11% of total clinical isolates.

CONCLUSIONS

In contrast to reports on invasive pneumococcal strains, in MEF isolates the reduction in the prevalence of PCV7 serotypes was not associated with decreases in penicillin/erythromycin non-susceptibility. The high prevalence of serotype 19A among paediatric MEF isolates and the amoxicillin non-susceptibility found in this serotype are worrisome since amoxicillin is the most common antibiotic used in the treatment of acute otitis media. These data suggest that non-PCV7 serotypes (mainly serotype 19A followed by serotypes 3 and 6A) are important etiological agents of acute otitis media and support the added value of the broader coverage of the new 13-valent conjugate vaccine.

The immunogenicity of pneumococcal polysaccharides in infants and children: a meta-regression

The immunogenicity of plain (not conjugated) pneumococcal polysaccharides in children and infants was reviewed using a systematic literature search. Immunogenicity was defined as the fold-increase in serotype specific antibody concentration after a single dose of plain polysaccharide vaccine in unprimed subjects. Meta-regression was used to calculate the influence of study treatments including subject age, sampling time, dosage, immunization route, vaccine composition and study location. Immunogenicity increased with age for all serotypes, and the increase was more rapid in the first 11 months of life. Study location was the next most significant study variable, with higher responses in countries with lower GDP. A flat dose-response curve was observed over a range from 5 to 50 μg polysaccharide. Serotypes 6A, 6B, 14, 19F and 23F were significantly less immunogenic than serotypes 2, 3, 4, 7F, 8, 9N, 9V and 18C in 11 month old children, but continued to increase in immunogenicity with age until reaching similar levels at 6 years. Some proposed T-independent immune mechanisms could explain the differences in serotype immunogenicity.

Impact of conjugate pneumococcal vaccines on the changing epidemiology of pneumococcal infections

Streptococcus pneumoniae-related infections have a major global impact on healthcare, especially in the developing world, and are considered the number one vaccine-preventable cause of death in children. There are more than 90 pneumococcal serotypes and 46 serogroups. The first capsular polysaccharide pneumococcal vaccine was licensed in the USA in 1977 for individuals older than 2 years of age at high risk for pneumococcal disease. Two decades later, the first 7-valent pneumococcal polysaccharide-protein conjugate vaccine completed the required clinical trials and was introduced as part of the national immunization program of various countries. New-generation vaccines that include emerging serotypes, while maintaining protection against the 7-valent pneumococcal serotypes, have recently been approved. With the addition of these serotypes, the majority of potential pneumococcal serotypes causing invasive disease in most parts of the world could be covered.

[Economic evaluation of an infant immunization program in Mexico, based on 13-valent pneumococcal conjugated vaccines]

OBJECTIVES

Vaccination is an effective intervention for reduce child morbidity and mortality associated to pneumococcus. The availability of new anti-pneumococcal vaccines makes it necessary to evaluate its potential impact on public health and costs related to their implementation. The aim of this study was to estimate the cost-effectiveness and cost-utility of immunization strategies based on pneumococcal conjugated vaccines (PCV's) currently available in Mexico from a third payer perspective.

MATERIAL AND METHODS

A decision tree model was developed to assess both, economic and health impact, of anti-pneumococcal vaccination in children <2 years (lifetime time horizon, discount rate: 5% annual). Comparators were: no-vaccination (reference) and strategies based on 7, 10 and 13-valent PCV's. Effectiveness measures were: child deaths avoided, life-years gained (LYG) and quality adjusted life years (QALY's) gained. Effectiveness, utility, local epidemiology and cost of treating pneumococcal diseases were extracted from published sources. Univariate sensitivity analysis were performed.

RESULTS

Immunization dominates no-vaccination: strategy based on 13-valent vaccine prevented 16.205 deaths, gained 331.230 LY's and 332.006 QALY's and saved US$1.307/child vaccinated. Strategies based on 7 and 10-valent PCV's prevented 13.806 and 5.589 deaths, gained 282.193 and 114.251 LY's, 282.969 and 114.972 QALY's and saved US$1.084 and US$731/child vaccinated, respectively. These results were robust to variations in herd immunity and lower immunogenicity of 10-valent vaccine.

CONCLUSIONS

In Mexico, immunization strategies based on 7, 10 and 13-valent PCV's would be cost-saving interventions, however, health outcomes and savings of the strategy based on 13-valent vaccine are greater than those estimated for 7 and 10-valent PCV's.

Moraxella catarrhalis outer membrane vesicles carry β-lactamase and promote survival of Streptococcus pneumoniae and Haemophilus influenzae by inactivating amoxicillin

Moraxella catarrhalis is a common pathogen found in children with upper respiratory tract infections and in patients with chronic obstructive pulmonary disease during exacerbations. The bacterial species is often isolated together with Streptococcus pneumoniae and Haemophilus influenzae. Outer membrane vesicles (OMVs) are released by M. catarrhalis and contain phospholipids, adhesins, and immunomodulatory compounds such as lipooligosaccharide. We have recently shown that M. catarrhalis OMVs exist in patients upon nasopharyngeal colonization. As virtually all M. catarrhalis isolates are β-lactamase positive, the goal of this study was to investigate whether M. catarrhalis OMVs carry β-lactamase and to analyze if OMV consequently can prevent amoxicillin-induced killing. Recombinant β-lactamase was produced and antibodies were raised in rabbits. Transmission electron microscopy, flow cytometry, and Western blotting verified that OMVs carried β-lactamase. Moreover, enzyme assays revealed that M. catarrhalis OMVs contained active β-lactamase. OMVs (25 μg/ml) incubated with amoxicillin for 1 h completely hydrolyzed amoxicillin at concentrations up to 2.5 μg/ml. In functional experiments, preincubation of amoxicillin (10× MIC) with M. catarrhalis OMVs fully rescued amoxicillin-susceptible M. catarrhalis, S. pneumoniae, and type b or nontypeable H. influenzae from β-lactam-induced killing. Our results suggest that the presence of amoxicillin-resistant M. catarrhalis originating from β-lactamase-containing OMVs may pave the way for respiratory pathogens that by definition are susceptible to β-lactam antibiotics.

Distribution, dynamics and antibiotic resistance patterns of Streptococcus pneumoniae serotypes causing acute otitis media in children in southern Israel during the 10 year-period before the introduction of the 7-valent pneumococcal conjugate vaccine

OBJECTIVES

To determine the dynamics of serotype prevalence, potential coverage by pneumococcal conjugate vaccines (PCV) and antibiotic resistance patterns of Streptococcus pneumoniae causing acute otitis media (AOM) in children in southern Israel before PCV7 introduction in the routine immunization program in Israel.

METHODS

All S. pneumoniae isolates from middle ear fluid from children with AOM during 1999-2008 were included. Prospectively collected demographic data on S. pneumoniae serotypes and antibiotic resistance patterns were analyzed.

RESULTS

A total of 14,911 tympanocenteses yielded 5281 (35%) S. pneumoniae. Proportion of S. pneumoniae-AOM did not vary significantly (overall 35%; 33% in 2007; 38% in 2002 and 2003). The most frequent serotypes were 19F, 14, 23F and 19A; in both Jewish and Bedouin children; serotypes 6A and 19A contributed 6% and 10%, respectively, of all S. pneumoniae isolates. Serotypes included in PCV7, PCV10 and PCV13 represented 60%, 64%, 85% in Jewish children vs. 49%, 55% and 74%, respectively, in Bedouin children (P < 0.001). Nonsusceptibility to TMP/SMX decreased significantly, in parallel with a significant increase in the nonsusceptibility to erythromycin, clindamycin and in multidrug resistant (MDR) isolates. No changes were recorded in the proportion of S. pneumoniae isolates with penicillin MIC ≥ 1.0 μg/ml. The proportion of penicillin- and erythromycin-nonsusceptible and of MDR serotype 6A and 19A isolates increased significantly in Bedouin children.

CONCLUSIONS

(1) No significant changes were recorded in the yearly proportions of serotypes 23F, 19F, 19A, 14 and 6A in both ethnic populations; (2) Potential coverage of the 3 PCVs was higher in Jewish children than in Bedouin children; (3) The relatively high coverage of macrolides- and multidrug-resistant S. pneumoniae by PCV13 and lack of increase in penicillin, erythromycin and multidrug nonsusceptibility among non-PCV13 isolates is encouraging.

Streptococcus pneumoniae clonal complex 199: genetic diversity and tissue-specific virulence

Streptococcus pneumoniae is an important cause of otitis media and invasive disease. Since introduction of the heptavalent pneumococcal conjugate vaccine, there has been an increase in replacement disease due to serotype 19A clonal complex (CC)199 isolates. The goals of this study were to 1) describe genetic diversity among nineteen CC199 isolates from carriage, middle ear, blood, and cerebrospinal fluid, 2) compare CC199 19A (n = 3) and 15B/C (n = 2) isolates in the chinchilla model for pneumococcal disease, and 3) identify accessory genes associated with tissue-specific disease among a larger collection of S. pneumoniae isolates. CC199 isolates were analyzed by comparative genome hybridization. One hundred and twenty-seven genes were variably present. The CC199 phylogeny split into two main clades, one comprised predominantly of carriage isolates and another of disease isolates. Ability to colonize and cause disease did not differ by serotype in the chinchilla model. However, isolates from the disease clade were associated with faster time to bacteremia compared to carriage clade isolates. One 19A isolate exhibited hypervirulence. Twelve tissue-specific genes/regions were identified by correspondence analysis. After screening a diverse collection of 326 isolates, spr0282 was associated with carriage. Four genes/regions, SP0163, SP0463, SPN05002 and RD8a were associated with middle ear isolates. SPN05002 also associated with blood and CSF, while RD8a associated with blood isolates. The hypervirulent isolate's genome was sequenced using the Solexa paired-end sequencing platform and compared to that of a reference serotype 19A isolate, revealing the presence of a novel 20 kb region with sequence similarity to bacteriophage genes. Genetic factors other than serotype may modulate virulence potential in CC199. These studies have implications for the long-term effectiveness of conjugate vaccines. Ideally, future vaccines would target common proteins to effectively reduce carriage and disease in the vaccinated population.

Non-typeable Haemophilus influenzae and Streptococcus pneumoniae as primary causes of acute otitis media in colombian children: a prospective study

Background

Acute otitis media (AOM) is one of the most frequently encountered bacterial infections in children aged < 5 years; Streptococcus pneumoniae (S. pneumoniae) and non-typeable Haemophilus influenzae (NTHi) are historically identified as primary AOM causes. Nevertheless, recent data on bacterial pathogens causing AOM in Latin America are limited. This prospective study aimed to identify and characterize bacterial etiology and serotypes of AOM cases including antimicrobial susceptibility in < 5 year old Colombian children.

Methods

From February 2008 to January 2009, children ≥3 months and < 5 years of age presenting with AOM and for whom a middle ear fluid (MEF) sample was available were enrolled in two medical centers in Cali, Colombia. MEF samples were collected either by tympanocentesis procedure or spontaneous otorrhea swab sampling. Bacteria were identified using standard laboratory methods, and antimicrobial resistance testing was performed based on the 2009 Clinical and Laboratory Standards Institute (CLSI) criteria. Most of the cases included in the study were sporadic in nature.

Results

Of the 106 enrolled children, 99 were included in the analysis. Bacteria were cultured from 62/99 (63%) of samples with S. pneumoniae, H. influenzae, or S. pyogenes. The most commonly isolated bacteria were H. influenzae in 31/99 (31%) and S. pneumoniae in 30/99 (30%) of samples. The majority of H. influenzae episodes were NTHi (27/31; 87%). 19F was the most frequently isolated pneumococcal serotype (10/30; 33%). Of the 30 S. pneumoniae positive samples, 8/30 (27%) were resistant to tetracycline, 5/30 (17%) to erythromycin and 8/30 (27%) had intermediate resistance to penicillin. All H. influenzae isolates tested were negative to beta-lactamase.

Conclusions

NTHi and S. pneumoniae are the leading causes of AOM in Colombian children. A pneumococcal conjugate vaccine that prevents both pathogens could be useful in maximizing protection against AOM.

Continued control of pneumococcal disease in the UK – the impact of vaccination

Streptococcus pneumoniae, also known as the pneumococcus, is an important cause of morbidity and mortality in the developed and developing world. Pneumococcal conjugate vaccines were first introduced for routine use in the USA in 2000, although the seven-valent pneumococcal conjugate vaccine (PCV7) was not introduced into the UK's routine childhood immunization programme until September 2006. After its introduction, a marked decrease in the incidence of pneumococcal disease was observed, both in the vaccinated and unvaccinated UK populations. However, pneumococci are highly diverse and serotype prevalence is dynamic. Conversely, PCV7 targets only a limited number of capsular types, which appears to confer a limited lifespan to the observed beneficial effects. Shifts in serotype distribution have been detected for both non-invasive and invasive disease reported since PCV7 introduction, both in the UK and elsewhere. The pneumococcal Haemophilus influenzae protein D conjugate vaccine (PHiD-CV, Synflorix; GlaxoSmithKline) and 13-valent pneumococcal conjugate vaccine (PCV13, Prevenar 13; Pfizer) have been newly licensed. The potential coverage of the 10- and 13-valent conjugate vaccines has also altered alongside serotype shifts. Nonetheless, the mechanism of how PCV7 has influenced serotype shift is not clear-cut as the epidemiology of serotype prevalence is complex. Other factors also influence prevalence and incidence of pneumococcal carriage and disease, such as pneumococcal diversity, levels of antibiotic use and the presence of risk groups. Continued surveillance and identification of factors influencing serotype distribution are essential to allow rational vaccine design, implementation and continued effective control of pneumococcal disease.

Pneumococcal serotypes causing pneumonia with pleural effusion in pediatric patients

To determine the prevalence of serotypes of Streptococcus pneumoniae responsible for pneumonia with pleural effusion, we determined the capsular polysaccharide (PS) type directly on 49 pleural fluid specimens collected from pediatric patients during 2007 to 2009 with laboratory-confirmed pneumococcal pneumonia by using monoclonal antibodies and a multiplex, bead array immunoassay. Because the fluids had to be heated to remove nonspecific reactivity before being tested in the immunoassay and type 19A PS is heat labile, the pleural fluid samples were also tested for serotype 19A capsule gene locus by PCR. Use of the multiplex immunoassay combined with type-specific 19A PCR allowed for serotype determination on 40 of 49 pleural fluids. Pneumococcal pneumonia with pleural effusion was associated with a limited number of serotypes, with types 1, 3, 7F/A, and 19A accounting for 75% of the typeable cases. The concentration of capsular PS in the pleural fluids was often greater than 1 μg/ml and sufficient to inhibit the opsonic capacity of sera from individuals who had received the 23-valent pneumococcal PS vaccine. Based on the serotypes observed before and after introduction of the 7-valent pneumococcal conjugate vaccine, the recently licensed 13-valent pneumococcal conjugate vaccine may reduce the incidence of pneumonia with pleural effusions.

Multiplex PCR to determine Streptococcus pneumoniae serotypes causing otitis media in the Republic of Ireland with further characterisation of antimicrobial susceptibilities and genotypes

The purpose of this study was to determine the serotypes, genotypes and antimicrobial susceptibilities of Streptococcus pneumoniae causing otitis media (OM) in children in Dublin, Ireland. S. pneumoniae isolates (n = 28) from spontaneously discharging OM were studied. Serotyping was performed using a previously undescribed multiplex polymerase chain reaction (PCR) scheme in combination with serological methods. Multilocus sequence typing (MLST) was performed using standard procedures. Antimicrobial susceptibility testing was performed using the Etest method. Fourteen different S. pneumoniae serotypes were identified. The five most common serotypes were 3, 19F, 19A, 14 and 6A, which accounted for 68% of all infections. The 7-valent pneumococcal conjugate vaccine (PCV7), 10-valent pneumococcal conjugate vaccine (PHiD-CV) and 13-valent pneumococcal conjugate vaccine (PCV13) provided potential coverages of 43%, 46% and 86%, respectively. Reduced susceptibility to penicillin was evident for 25% of isolates and was associated with serotypes 14, 19A, 19F and 9V. A total of 21 different sequence types (STs) were identified. Pneumococcal Molecular Epidemiology Network (PMEN) clones or their variants represented 54% (15/28) of all isolates. Continued monitoring and characterisation of S. pneumoniae causing OM in Ireland is warranted in order to guide future vaccine and treatment policies.

Intranasal vaccination with chitosan-DNA nanoparticles expressing pneumococcal surface antigen a protects mice against nasopharyngeal colonization by Streptococcus pneumoniae

Streptococcus pneumoniae is a respiratory pathogen, and mucosal immune response plays a significant role in the defense against pneumococcal infections. Thus, intranasal vaccination may be an alternative approach to current immunization strategies, and effective delivery systems to mucosal organism are necessary. In this study, BALB/c mice were immunized intranasally with chitosan-DNA nanoparticles expressing pneumococcal surface antigen A (PsaA). Compared to levels in mice immunized with naked DNA or chitosan-pVAX1, anti-PsaA IgG antibody in serum and anti-IgA antibody in mucosal lavages were elevated significantly in mice immunized with chitosan-psaA. The balanced IgG1/IgG2a antibody ratio in serum, enhanced gamma interferon (IFN-γ) and IL-17A levels in spleen lymphocytes, and mucosal washes of mice immunized with chitosan-psaA suggested that cellular immune responses were induced. Furthermore, significantly fewer pneumococci were recovered from the nasopharynx of mice immunized with chitosan-psaA than for the control group following intranasal challenge with ATCC 6303 (serotype 3). These results demonstrated that mucosal immunization with chitosan-psaA may successfully generate mucosal and systemic immune responses and prevent pneumococcal nasopharyngeal colonization. Hence, a chitosan-DNA nanoparticle vaccine expressing pneumococcal major immunodominant antigens after intranasal administration could be developed to prevent pneumococcal infections.

Public health and economic impact of the 13-valent pneumococcal conjugate vaccine (PCV13) in the United States

The 7-valent pneumococcal conjugate vaccine (PCV7) has dramatically decreased pneumococcal disease incidence, and the 13-valent vaccine (PCV13) protects against 6 additional Streptococcus pneumoniae serotypes. A decision-analytic model was constructed to evaluate the impact of infant vaccination with PCV13 versus PCV7 on pneumococcal disease incidence and mortality as well as the incremental benefit of a serotype catch-up program. PCV13 effectiveness was extrapolated from observed PCV7 data, using assumptions regarding serotype prevalence and PCV13 protection against additional serotypes. The model predicts that PCV13 is more effective and cost saving compared with PCV7, preventing 106,000 invasive pneumococcal disease (IPD) cases and 2.9 million pneumonia cases, and saving $11.6 billion over a 10-year period. The serotype catch-up program would prevent an additional 12,600 IPD cases and 404,000 pneumonia cases, and save an additional $737 million compared with no catch-up program.

Vaccination with peptide mimotopes produces antibodies recognizing bacterial capsular polysaccharides

A phage display peptide library was screened using a panel of antibodies to the capsular polysaccharides of Streptococcus agalactiae and Neisseria meningitidis. Mimotopes NPDHPRVPTFMA (2-8), LIPFHKHPHHRG (3-2) and EQEIFTNITDRV (G3) showing the highest binding capacity and strongest ELISA reaction were selected for immunization experiments. These mimotopes were either synthesised as oligodeoxynucleotides for DNA immunization or MAP (multiple antigen peptide) for peptide immunization. Mimotope-DNA vaccination, particularly for G3, induced antibodies recognizing a number of target bacteria. This response was seen after the second boost injection and was significantly enhanced by the 3rd boost injection with a Th1-associated profile, which was dominated by IgG2a, followed by IgG1. Mimotope-MAP immunization also produced strong humoral immune responses to the bacteria. Antibodies from G3 DNA immunization reacted with the surface molecules of S. agalactiae, N. meningitidis and Escherichia coli K5 shown by indirect immunofluorescence staining, indicating a possible localization to the bacterial capsule. Antibodies produced both from DNA/MAP immunization reacted with purified bacterial capsular polysaccharides by ELISA and were of high avidity. We have further characterized peptide G3 by a 'tiling path' study to examine the effect of changing individual residues in the peptide in raising antibodies, which showed that the EIFTN motif in G3 was important in generating antibodies to several capsulated bacteria. We conclude that mimotope immunization with DNA or MAP potentially induces strong antibody responses against encapsulated bacteria. It is suggested that the antibody targets are polysaccharides, and these antibodies may cross react at least among closely related species of bacteria.

Serotype distribution in pneumococcal acute otitis media with ruptured tympanic membrane or sepsis in Germany

This retrospective analysis examined the pneumococcal serotype distribution of acute otitis media in Germany from 1995 to 2007. Data from the German National Reference Centre for Streptococci included 512 cases of pneumococcal otitis media in children and adults. Infections were mainly seen in children aged <5 years, who represented 67.0% of all reported cases. Most isolates (86.7%) were from spontaneous ruptures of the tympanum; 11.1% of the isolates were from otogenic sepsis or meningitis. Serotype 19F was the leading serotype (21.5%); serotype 3 (13.9%) was also often encountered. In children aged <5 years, the 7-valent, 10-valent, and 13-valent pneumococcal conjugate vaccines covered 54.3%, 60.2%, and 84.6% of the serotypes, respectively. Reduced penicillin susceptibility (minimum inhibitory concentration >or=0.1 mg/l) was seen in 11.0% of strains; 22.4% of strains were resistant to macrolides. Although based on a very limited selection of acute otitis media isolates, this analysis provides an estimate of the pneumococcal serotypes responsible for otitis media in Germany and underscores the need for future prospective studies.

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.