Prevention of Infectious Diseases by Neonatal and Early Infantile Immunization: Prospects for the New Millennium*:

Aetiology of community-acquired neonatal sepsis in low and middle income countries

BACKGROUND

99% of the approximate 1 million annual neonatal deaths from life-threatening invasive bacterial infections occur in developing countries, at least 50% of which are from home births or community settings. Data concerning aetiology of sepsis in these settings are necessary to inform targeted therapy and devise management guidelines. This review describes and analyses the bacterial aetiology of community-acquired neonatal sepsis in developing countries.

METHODS

A search of Medline, Embase, Global Health and Web of Knowledge, limited to post-1980, found 27 relevant studies. Data on aetiology were extracted, tabulated and analysed along with data on incidence, risk factors, case fatality rates and antimicrobial sensitivity.

RESULTS

The most prevalent pathogens overall were Staphylococcus aureus (14.9%), Escherichia coli (12.2%), and Klebsiella species (11.6%). However, variations were observed both between global regions and age-of-onset categories. Staphylococcus aureus and Streptococcus pneumoniae were most prevalent in Africa, while Klebsiella was highly prevalent in South-East Asia. A notably higher prevalence of Group B Streptococcus was present in neonates aged 7 days or less. The highest case fatality rates were recorded in South-East Asia. Klebsiella species showed highest antimicrobial resistance.

CONCLUSION

Data on community-acquired neonatal sepsis in developing countries are limited. Future research should focus on areas of high disease burden with relative paucity of data. Research into maternal and neonatal vaccination strategies and improved diagnostics is also needed. All of this could contribute to the formulation of community-based care packages, the implementation of which has significant potential to lower overall neonatal mortality and hence advance progress towards the attainment of Millennium Development Goal 4.

Applications and Optimization of Immunization Procedures

Classical immunization protocols have produced an antibody-based humoral response that is very effective against susceptible infectious diseases. Immunization introduces an external substance to induce the host immune system to respond specifically. Typically an antigen is used, but DNA, or a primed, pre-existing leukocyte or antigen-presenting cell, can also be used. Immunization is currently being used or investigated for the prevention and treatment of infectious diseases, cancer, addictions, allergies, pregnancy, and autoimmune diseases. It is also being used to produce biologically active materials such as polyclonal and monoclonal antibodies, antivenins, and anti-toxins for treating a wide range of conditions. Animals have been integral to the development of immunization techniques, as producers of toxoids and antitoxins, as models (e.g., to validate materials and protocols used for immunization, to understand the impact of immunization itself on the immune system, and to help investigators devise methods for determining the efficacy of vaccines) and as beneficiaries themselves of vaccines and antitoxins. The choice of immunization protocols is complex, and results may be affected by many factors such as dose and concentration of antigen, choice of adjuvants, time between inoculation and response measurement, and method of detection. The immune system responses to an antigen are also complex and continue to develop with advancing age. Anatomical, physiological, and immune system differences between species influence responses to immunization, as do the purity and presentation of the antigens and adjuvants. When directly comparing results, animals should be sourced from the same supplier. This review highlights the many uses of immunization techniques and introduces important considerations for the choice of protocols and animal models.