Molecular Detection of Streptococcus pneumoniae on Dried Blood Spots from Febrile Nigerian Children Compared to Culture

Background

Nigeria has one of the highest burdens of pneumococcal disease in the world, but accurate surveillance is lacking. Molecular detection of infectious pathogens in dried blood spots (DBS) is an ideal method for surveillance of infections in resource-limited settings because of its low cost, minimal blood volumes involved, and ease of storage at ambient temperature. Our study aim was to evaluate a Streptococcus pneumoniae real-time polymerase chain reaction (rt-PCR) assay on DBS from febrile Nigerian children on Whatman 903 and FTA filter papers, compared to the gold standard of culture.

Methods

Between September 2011 to May 2015, blood was collected from children 5 years of age or under who presented to six hospital study sites throughout northern and central Nigeria with febrile illness, and inoculated into blood culture bottles or spotted onto Whatman 903 or FTA filter paper. Culture and rt-PCR were performed on all samples.

Results

A total of 537 DBS specimens from 535 children were included in the study, of which 15 were culture-positive for S. pneumoniae. The rt-PCR assay detected S. pneumoniae in 12 DBS specimens (2.2%). One positive rt-PCR result was identified in a culture-negative specimen from a high-risk subject, and two positive rt-PCR results were negative on repeat testing. Six culture-confirmed cases of S. pneumoniae bacteremia were missed. Compared to culture, the overall sensitivities of Whatman 903 and FTA DBS for detection of S. pneumoniae were 57.1% (95% CI 18.4–90.1%) and 62.5% (95% CI 24.5–91.5%), respectively. Nonspecific amplification was noted in an additional 22 DBS (4.1%). Among these, six were positive for a non-S. pneumoniae pathogen on culture.

Conclusions

Rt-PCR was able to detect S. pneumoniae from clinical DBS specimens, including from a culture-negative specimen. Our findings show promise of this approach as a surveillance diagnostic, but also raise important cautionary questions. Several DBS specimens were detected as S. pneumoniae by rt-PCR despite growth of a non-S. pneumoniae pathogen on culture. A precise definition of what constitutes a positive result is required to avoid falsely over-identifying specimens.

Sickle-Cell Disease in Nigerian Children: Parental Knowledge and Laboratory Results

BACKGROUND

Sickle-cell disease (SCD) is the most common inherited genetic disorder in sub-Saharan Africa, and it is associated with early mortality and lifelong morbidity. Early diagnosis is essential for instituting appropriate care and preventive therapy.

OBJECTIVE

To compare parental knowledge or perception of their offspring's hemoglobin phenotype prior to testing and actual validated laboratory test results.

METHODS

In a prospective community-based survey, we assessed parental knowledge of their children's hemoglobin phenotype and corroborated this with the results from a laboratory confirmatory test determined by high-performance liquid chromatography.

RESULTS

We screened 10,126 children aged less than 5 years. A total of 163 (1.6%) parents indicated that their offspring had been previously tested and had knowledge of the child's hemoglobin genotype. However, 51 (31.2%) of 163 parents of children who had been previously tested did not know the result of their offspring's test, and 18 (35.3%) of these 51 children were found to have SCD. Of those who claimed previous knowledge, 25 (15.3%) of 163 reported incorrect results. Overall, we identified 272 (2.76%) new cases from 9,963 children who had not been previously tested.

CONCLUSION

There is the need to promote public awareness about SCD and the benefit of early diagnosis, quality assurance in laboratory diagnosis and institution of sustainable patient care pathways.

Hydroxyurea Therapy for Children With Sickle Cell Anemia in Sub-Saharan Africa: Rationale and Design of the REACH Trial

BACKGROUND

Sickle cell anemia (SCA) is an inherited hematological disorder that causes a large but neglected global health burden, particularly in Africa. Hydroxyurea represents the only available disease-modifying therapy for SCA, and has proven safety and efficacy in high-resource countries. In sub-Saharan Africa, there is minimal use of hydroxyurea, due to lack of data, absence of evidence-based guidelines, and inexperience among healthcare providers.

PROCEDURE

A partnership was established between investigators in North America and sub-Saharan Africa, to develop a prospective multicenter research protocol designed to provide data on the safety, feasibility, and benefits of hydroxyurea for children with SCA.

RESULTS

The Realizing Effectiveness Across Continents with Hydroxyurea (REACH, ClinicalTrials.gov NCT01966731) trial is a prospective, phase I/II open-label dose escalation study of hydroxyurea that will treat a total of 600 children age 1-10 years with SCA: 150 at each of four different clinical sites within sub-Saharan Africa (Angola, Democratic Republic of Congo, Kenya, and Uganda). The primary study endpoint will be severe hematological toxicities that occur during the fixed-dose treatment phase. REACH has an adaptive statistical design that allows for careful assessment of toxicities to accurately identify a safe hydroxyurea dose.

CONCLUSIONS

REACH will provide data that address critical gaps in knowledge for the treatment of SCA in sub-Saharan Africa. By developing local expertise with the use of hydroxyurea and helping to establish treatment guidelines, the REACH trial results will have the potential to transform care for children with SCA in Africa.

Neonatal group B streptococcus disease in developing countries: are we ready to deploy a vaccine?

Group B streptococcus (GBS) disease is the leading cause of neonatal sepsis in developed countries and has high case fatality rates. In developing countries, however, the burden of GBS is less clear; this is due to a lack of studies using optimal diagnostic, clinical and laboratory techniques and is complicated by the wide availability of non-prescription antibiotics to the general population and in peripartum patients. There is an urgent need for prospective, population-based surveillance to provide an accurate assessment of neonatal GBS disease burden in developing countries, which remains largely unrecognized, and consequently obscures the potential relevance of GBS vaccination in these populations. Preliminary data on GBS vaccines are promising as a preventive tool for neonatal GBS infection, more so than any other currently available public health initiative. However, how do we assess the true impact of a GBS vaccine without accurate surveillance data on the real burden of disease?

Comparative effectiveness of congregation- versus clinic-based approach to prevention of mother-to-child HIV transmission: study protocol for a cluster randomized controlled trial

Background

A total of 22 priority countries have been identified by the WHO that account for 90% of pregnant women living with HIV. Nigeria is one of only 4 countries among the 22 with an HIV testing rate for pregnant women of less than 20%. Currently, most pregnant women must access a healthcare facility (HF) to be screened and receive available prevention of mother-to-child HIV transmission (PMTCT) interventions. Finding new approaches to increase HIV testing among pregnant women is necessary to realize the WHO/ President's Emergency Plan for AIDS Relief (PEPFAR) goal of eliminating new pediatric infections by 2015.

Methods

This cluster randomized trial tests the comparative effectiveness of a congregation-based Healthy Beginning Initiative (HBI) versus a clinic-based approach on the rates of HIV testing and PMTCT completion among a cohort of church attending pregnant women. Recruitment occurs at the level of the churches and participants (in that order), while randomization occurs only at the church level. The trial is unblinded, and the churches are informed of their randomization group. Eligible participants, pregnant women attending study churches, are recruited during prayer sessions. HBI is delivered by trained community health nurses and church-based health advisors and provides free, integrated on-site laboratory tests (HIV plus hemoglobin, malaria, hepatitis B, sickle cell gene, syphilis) during a church-organized ‘baby shower.’ The baby shower includes refreshments, gifts exchange, and an educational game show testing participants’ knowledge of healthy pregnancy habits in addition to HIV acquisition modes, and effective PMTCT interventions. Baby receptions provide a contact point for follow-up after delivery. This approach was designed to reduce barriers to screening including knowledge, access, cost and stigma. The primary aim is to evaluate the effect of HBI on the HIV testing rate among pregnant women. The secondary aims are to evaluate the effect of HBI on the rate of HIV testing among male partners of pregnant women and the rate of PMTCT completion among HIV-infected pregnant women.

Discussion

Results of this study will provide further understanding of the most effective strategies for increasing HIV testing among pregnant women in hard-to-reach communities.

Trial Registration

Clinicaltrials.gov, NCT01795261

Host response transcriptional profiling reveals extracellular components and ABC (ATP-binding cassette) transporters gene enrichment in typhoid fever-infected Nigerian children

Background

Salmonella enterica serovar Typhi (S. Typhi) is a human-specific pathogen that causes typhoid fever, and remains a global health problem especially in developing countries. Its pathogenesis is complex and host response is poorly understood. In Africa, typhoid fever can be a major cause of morbidity in young infected children. The onset of the illness is insidious and clinical diagnosis is often unreliable. Gold standard blood culture diagnostic services are limited, thus rapid, sensitive, and affordable diagnostic test is essential in poor-resourced clinical settings. Routine typhoid fever vaccination is highly recommended but currently licensed vaccines provide only 55-75% protection. Recent epidemiological studies also show the rapid emergence of multi-drug resistant S. Typhi strains. High-throughput molecular technologies, such as microarrays, can dissect the molecular mechanisms of host responses which are S. Typhi-specific to provide a comprehensive genomic component of immunological responses and suggest new insights for diagnosis and treatment.

Methods

Global transcriptional profiles of S. Typhi-infected young Nigerian children were obtained from their peripheral blood and compared with that of other bacteremic infections using Agilent gene expression microarrays. The host-response profiles of the same patients in acute vs. convalescent phases were also determined. The top 96-100 differentially-expressed genes were identified and four genes were validated by quantitative real-time PCR. Gene clusters were obtained and functional pathways were predicted by DAVID (Database for Annotation, Visualization and Integrated Discovery).

Results

Transcriptional profiles from S. Typhi-infected children could be distinguished from those of other bacteremic infections. Enriched gene clusters included genes associated with extracellular peptides/components such as lipocalin (LCN2) and systemic immune response which is atypical in bacterial invasion. Distinct gene expression profiles can also be obtained from acute vs. convalescent phase during typhoid fever infection. We found novel down-regulation of ABC (ATP-binding cassette) transporters genes such as ABCA7, ABCC5, and ABCD4 and ATPase activity as the highest enriched pathway.

Conclusions

We identified unique extracellular components and ABC transporters gene enrichments in typhoid fever-infected Nigerian children, which have never been reported. These enriched gene clusters may represent novel targeted pathways to improve diagnostic, prognostic, therapeutic and next-generation vaccine strategies for typhoid fever in Africa.

Sickle cell disease and malaria morbidity: a tale with two tails

More than 230,000 children are born in Africa with sickle cell disease (SCD) each year: approximately 85% of all affected births worldwide. Although malaria is commonly viewed as a major problem for African patients with this condition, questions still remain about its relative importance as a cause of ill heath and death. In the absence of definitive studies investigating the contribution of malaria to morbidity and mortality in African children with SCD, policy makers will continue to lack the evidence on which to base appropriate management guidelines.

Infection in sickle cell disease: a review

Infection is a significant contributor to morbidity and mortality in sickle cell disease (SCD). The sickle gene confers an increased susceptibility to infection, especially to certain bacterial pathogens, and at the same time infection provokes a cascade of SCD-specific pathophysiological changes. Historically, infection is a major cause of mortality in SCD, particularly in children, and it was implicated in 20-50% of deaths in prospective cohort studies over the last 20 years. Worldwide, it remains the leading cause of death, particularly in less developed nations. In developed countries, measures to prevent and effectively treat infection have made a substantial contribution to improvements in survival and quality of life, and are continually being developed and extended. However, progress continues to lag in less developed countries where the patterns of morbidity and mortality are less well defined and implementation of preventive care is poor. This review provides an overview of how SCD increases susceptibility to infections, the underlying mechanisms for susceptibility to specific pathogens, and how infection modifies the outcome of SCD. It also highlights the challenges in reducing the global burden of mortality in SCD.

Sense and the science of childhood immunization: Can we achieve more with less?

The threat of biological terrorism with small pox virus and a global influenza pandemic in the face of limited vaccine supply recently stimulated research into the evaluation of fractional dose vaccine regimens, with promising immunogenicity results. While this approach is not new, it has been less applied to vaccines for less sensational but nevertheless, significant killer diseases. This manuscript provides an overview of the basics of immunization as it applies to the current practice of immunization in children, comments on the untapped avenues for cost reduction of vaccine delivery, and the potential for saving more lives with currently available resources.

Bacterial pneumonia vaccines and childhood pneumonia: are we winning, refining, or redefining?

Bacterial pneumonia is a substantial cause of childhood morbidity and mortality worldwide, but determination of pathogen-specific burden remains a challenge. In less developed settings, the WHO recommended guidelines are useful for initiating care, but are non-specific. Blood culture has low sensitivity, while radiological findings are non-specific and do not discriminate between viral and bacterial causes of pneumonia. In vaccine probe studies, efficacy is dependent on the specificity of the study outcome to detect pneumonia and the impact of the vaccine on the selected outcome, and may underestimate the true burden of bacterial pneumonia. The rising incidence of antibiotic resistance, emerging respiratory pathogens, potential replacement pneumococcal disease following widespread introduction of pneumococcal polysaccharide-protein conjugate vaccine, the limited specificity of chest radiography, and the poor sensitivity of blood culture are substantial obstacles to accurate surveillance. We provide an overview of the diagnostic challenges of bacterial pneumonia and highlight the need for refining the current diagnostic approach to ensure adequate epidemiological surveillance of childhood pneumonia and the success, or otherwise, of any immunisation strategies.

Efficacy of nine-valent pneumococcal conjugate vaccine against pneumonia and invasive pneumococcal disease in The Gambia: randomised, double-blind, placebo-controlled trial

BACKGROUND

Pneumonia is estimated to cause 2 million deaths every year in children. Streptococcus pneumoniae is the most important cause of severe pneumonia. We aimed to assess the efficacy of a nine-valent pneumococcal conjugate vaccine in children.

METHODS

We undertook a randomised, placebo-controlled, double-blind trial in eastern Gambia. Children age 6-51 weeks were randomly allocated three doses of either pneumococcal conjugate vaccine (n=8718) or placebo (8719), with intervals of at least 25 days between doses. Our primary outcome was first episode of radiological pneumonia. Secondary endpoints were clinical or severe clinical pneumonia, invasive pneumococcal disease, and all-cause admissions. Analyses were per protocol and intention to treat.

FINDINGS

529 children assigned vaccine and 568 allocated placebo were not included in the per-protocol analysis. Results of per-protocol and intention-to-treat analyses were similar. By per-protocol analysis, 333 of 8189 children given vaccine had an episode of radiological pneumonia compared with 513 of 8151 who received placebo. Pneumococcal vaccine efficacy was 37% (95% CI 27-45) against first episode of radiological pneumonia. First episodes of clinical pneumonia were reduced overall by 7% (95% CI 1-12). Efficacy of the conjugate vaccine was 77% (51-90) against invasive pneumococcal disease caused by vaccine serotypes, 50% (21-69) against disease caused by all serotypes, and 15% (7-21) against all-cause admissions. We also found an efficacy of 16% (3-28) against mortality. 110 serious adverse events arose in children given the pneumococcal vaccine compared with 131 in those who received placebo.

INTERPRETATION

In this rural African setting, pneumococcal conjugate vaccine has high efficacy against radiological pneumonia and invasive pneumococcal disease, and can substantially reduce admissions and improve child survival. Pneumococcal conjugate vaccines should be made available to African infants.

Failure of serial human immunodeficiency virus type 1 DNA polymerase chain reactions to identify human immunodeficiency virus type 1 clade A/G

The most commonly used test to screen for human immunodeficiency virus type 1 (HIV-1) infection in HIV-exposed infants in the United States is HIV-1 qualitative DNA polymerase chain reaction (PCR). However, the commercially available HIV-1 DNA PCR lack optimal sensitivity to detect non-subtype B subtypes of HIV-1. We report here HIV-1 infection in a West African infant that went undetected by serial HIV-1 DNA PCR tests.

Colostrum Obtained from Women Vaccinated with Pneumococcal Vaccine during Pregnancy Inhibits Epithelial Adhesion ofStreptococcus pneumoniae

Prevention of nasopharyngeal colonization may reduce the burden of pneumococcal infection during infancy. Colostrum obtained from Gambian mothers who had been vaccinated with either Pneumovax II or Mengivax A&C (n=8 per group) during pregnancy was examined for inhibition of adherence of Streptococcus pneumoniae serotypes 6B and 14 to pharyngeal epithelial cells in vitro. Pneumococcal adherence was significantly reduced in the presence of breast milk (P< or =.0001 for S. pneumoniae serotype 14; P=.036 for serotype 6B), independent of the concentration of secretory IgA antibodies. Maternal vaccination with polyvalent pneumococcal polysaccharide vaccine boosts the capacity of colostrum to inhibit adherence of pneumococci to pharyngeal epithelial cells. In breast-feeding populations, maternal vaccination might prevent pneumococcal disease in young infants.

Serotype-specific pneumococcal antibodies in breast milk of Gambian women immunized with a pneumococcal polysaccharide vaccine during pregnancy

BACKGROUND

In breast-feeding populations, immunization during pregnancy with pneumococcal polysaccharide offers a potentially useful approach to preventing pneumococcal disease in young infants.

METHODS

Breast milk samples were collected at 0, 2, 4 and 6 months after delivery from Gambian women vaccinated during pregnancy (24-32 weeks gestation) with Pneumovax II (n = 56) or Mengivax A&C (n = 57). Specimens were examined for secretory immunoglobulin A (s-IgA) concentration, subclass distribution and avidity specific to pneumococcal serotypes 4, 6B, 14, 19F and 23F and the antigen mixture in Pneumovax II by enzyme-linked immunosorbent assay. Colostral s-IgA and IgG concentrations in paired maternal sera were compared.

RESULTS

Colostral s-IgA concentrations specific to all pneumococcal polysaccharide antigens investigated were significantly higher (P < 0.05) among Pneumovax II vaccinees. Titers specific to serotypes 4, 6B and 14 and the vaccine formula remained significantly higher during 6 months, and those for 19F were higher during 4 months. Significantly higher concentrations of vaccine antigen-specific s-IgA antibody were sustained for 6 months after delivery (P = 0.011). Comparison of colostral s-IgA and IgG in serum revealed a significant correlation only among Mengivax A&C vaccinees for pneumococcal polysaccharide 23F (rs= 0.68; P < or = 0.0001). Vaccination elicited trends toward increased s-IgA2, reaching significance for serotype 14 and the vaccine formula. Immunization elicited significantly higher s-IgA avidities specific to all pneumococcal polysaccharide antigens studied during 6 months.

CONCLUSIONS

The public health value of immunization during pregnancy with pneumococcal polysaccharide vaccine in breast-feeding populations warrants further evaluation, particularly in populations with a high incidence of pneumococcal disease in early infancy.

Immunogenicity and efficacy of childhood vaccines in HIV-1-infected children

Children infected by HIV-1 are particularly vulnerable to severe, recurrent, or unusual infections by vaccine-preventable pathogens. Routine immunisations seem to be generally safe for HIV-1-infected children, but responses may be suboptimal. Early HIV-1-induced immune attrition associated with viral replication may particularly interfere with the development of memory responses. In high HIV-1 prevalence regions, the accumulation of susceptible hosts may compromise disease-control efforts. Although early control of viral replication through treatment with highly active therapy may preserve immune function and responses to routine childhood vaccines, availability is limited in the areas most affected. In this review, we provide an overview of the immunogenicity and efficacy of childhood vaccines in HIV-1-infected children. The possible immunological bases for defective responses are discussed; unanswered questions and the need for further research are delineated.

Vaccines for children: policies, politics and poverty

The dawn of the 21st century ushered in spectacular advances in vaccine production technology. However, the benefits of these developments have been largely confined to the world's most affluent and least afflicted. Of the 14 million deaths that occur world-wide in children aged less than 5 years, over 95% of these occur in developing countries and at least 70% are caused by infections for which vaccines are already available in other countries. While impoverished countries do not have a right to be assisted with the provision of funds or vaccines by affluent developed countries, an initiative for the global eradication of a vaccine preventable disease, requires a global effort. Assisting developing countries to achieve such goals should be a high priority for wealthy nations, even if only to protect their own populations. With improved international travel, not only can newly emerging diseases spread across the globe, but pathogens eliminated from one population can be re-imported by travellers or immigrants. In contrast, the recent decline in acceptance of immunisation programmes in developed countries are secondary to strong anti-vaccine movements attributing unproven adverse reactions to vaccines, placing these life-saving vaccines into disrepute. A fertile ground for propagation of these ideologies is created by parents who in their lifetime may not have seen a child killed or maimed from bacterial meningitis or measles and therefore have little understanding of the risk-benefit of vaccination. The development and deployment of vaccines must be a global effort as are the treaties for global disarmament for weapons of mass destruction.

Safety and immunogenicity of pneumococcal conjugate vaccine in combination with diphtheria, tetanus toxoid, pertussis and Haemophilus influenzae type b conjugate vaccine

BACKGROUND

Pneumococcal polysaccharide/protein conjugate vaccines (PnCV) are immunogenic and effective in infancy. However, an addition to the nine currently recommended vaccine injections during the first year of life of African children may be a deterrent to participation in a PnCV program. Thus we have evaluated the safety and immunogenicity of a 9-valent PnCV (Wyeth Lederle Pediatrics and Vaccines) mixed with diphtheria, tetanus toxoid, cell pertussis and type b (TETRAMUNE).

METHODS

Healthy Gambian infants were randomized at the age of 2 months to receive three doses 1 month apart of either (1) placebo reconstituted in TETRAMUNE in the right thigh (control) or (2) PnCV in the left thigh and TETRAMUNE in the right thigh (separate) or (3) PnCV reconstituted in TETRAMUNE as a single injection in the right thigh (combined). The vaccines were given together with routine Expanded Program on Immunization vaccines. Adverse reactions were recorded after vaccination, and antibody concentrations were measured by enzyme-linked immunosorbent assays.

RESULTS

Local induration and tenderness were observed more commonly at the site of injection of TETRAMUNE than at the site of injection with PnCV after each dose of vaccination. Swelling at the site of injection was encountered more frequently at the site of administration of TETRAMUNE than at the site of administration PnCV ( P< 0.00001 for Doses 1 and 2 and P< 0.0009 for Dose 3). Swelling at the site of administration of TETRAMUNE mixed with PnCV was comparable with that observed for TETRAMUNE alone. Although most mothers reported that the babies "felt hot" 24 h after each injection, febrile reactions (temperature, >or=38 degrees C) were infrequent and resolved with antipyretics. Geometric mean titer for anti-polyribosylribitol phosphate antibody was 11.6 microg/ml [95% confidence limits (95% CI), 9.2, 14.6] in the control group and comparable with 13.3 microg/ml (95% CI 11.0, 16.0) in the combined group and significantly higher at 17.9 microg/ml (95% CI 14.7, 21.9; P= 0.01) in the separate group. Geometric mean concentrations of serotype-specific pneumococcal antibodies were higher in the combined group than the separate group for all nine serotypes. Antibody responses to diphtheria and pertussis antigens were similar in all groups. Anti-tetanus toxoid antibody concentrations were lowest in the combined group (6.66 IU/ml, 95% CI 5.77, 7.68 in the control group; 5.15 IU/ml, 95% CI 4.39, 6.03 in the combined group; P= 0.02). However, all vaccinees achieved protective antibody values.

CONCLUSION

The combination of TETRAMUNE and PnCV is safe and immunogenic.

The new pneumococcal vaccine

Pneumococcal disease is now the leading cause of vaccine-preventable bacterial disease in children worldwide. Although a pneumococcal polysaccharide vaccine has been available for over three decades, its use has been limited due to poor immunogenicity in the most vulnerable children, aged less than 2 years. The prevalence of pneumococcal disease worldwide and the alarming global escalation of multiresistant strains of Streptococcus pneumoniae (pneumococcus) during the past decade have provided the impetus for the development and application of a new pneumococcal vaccine. The outstanding success of Haemophilus influenzae type b (Hib) conjugate vaccine in the control of invasive Hib disease is a reason to be optimistic that the pneumococcal conjugate vaccines will achieve similar results for the control of invasive pneumococcal disease. Remarkable efficacy against invasive pneumococcal disease with a seven-valent pneumococcal conjugate vaccine was demonstrated in infants and toddlers in the USA, and in February 2000 the first pneumococcal conjugate vaccine was licensed. Licensure and widespread use is likely to follow in other countries in which there is a need and the means to afford this live-saving vaccine. Active disease surveillance must be sustained globally, while active research, development of other multivalent conjugate formulations and the search for new candidate protein-based vaccines are in progress.