Bacterial and viral etiology of serious infections in very young Filipino infants.

OBJECTIVE: Pneumonia, meningitis and other serious infections are leading causes of death in developing countries. As part of a multicenter study we aimed to determine the etiology of pneumonia, meningitis and other serious infections in a cohort of Filipino infants ages 90 days or younger. METHOD: During a 2-year period, 2053 infants age 90 days or younger presenting to 1 of 3 Manila community hospitals were screened; 873 had signs or symptoms suggestive of an infectious illness, and 608 were judged to have clinical features suggestive of severe infection and had laboratory workup including blood for culture and white blood cell count, nasopharyngeal aspirate for virology, cerebrospinal fluid culture when indicated and chest radiograph. Chest radiographs were read independently by 3 radiologists without knowledge of clinical findings. RESULTS: Of the 873 enrolled infants, 81 died (91%). After exclusion of presumed contaminants, positive bacterial culture from blood and/or cerebrospinal fluid was obtained in 35 infants (5.8%; 95% confidence interval 4%, 8%), 9 of whom died. The organisms responsible for meningitis were Acinetobacter spp. (4), Streptococcus pneumoniae (2), Escherichia coli (2), Enterobacter spp. (1), Pseudomonas aeruginosa (1), Haemophilus influenzae (1) and Staphylococcus aureus (1); those responsible for the other clinical diagnoses were Salmonella spp. (6), Enterobacter spp. (3), Streptococcus pyogenes (3), other Gram-negative organisms (8), S. pneumoniae (1) and Staphylococcus aureus (2). In 685 infants examined for viral causes of their illness, 223 viruses were isolated from 219 infants (32%; 95% confidence interval 28%, 36%). Enteroviruses were the most common potential pathogens identified (22% of infants studied), followed by respiratory syncytial virus (17%), rhinovirus (10%) and adenovirus (4%). Concomitant virus identification occurred in 10 of those with positive bacterial culture (29%; 95% confidence interval, 15%, 46%), with enterovirus being found in 7 of these cases. CONCLUSION: Many young Filipino infants with life-threatening illness were evaluated in this study. Thirty-five had infections attributable to bacteria, with Salmonella spp. being the most common, followed by Gram-negative organisms. Pneumococcus was an unusual cause.

Antibody responses of three Haemophilus influenzae type b conjugate vaccines after one, two and three doses in Filipino children.

Differences in the magnitude of antibody response after one, two or three doses of Haemophilus influenzae type b conjugate vaccines have been reported which may influence decision-making regarding which vaccine should be used. This is of particular importance in developing countries where children may not receive a full immunization series and the vaccination schedule may be delayed. Serum antibody responses to three Hib capsular polysaccharide protein conjugate vaccines (PRP-OMP, HbOC and PRP-T) were evaluated in 102 Filipino infants. Vaccination was carried out at 6, 10 and 14 weeks of age based on the national Expanded Programme on Immunization (EPI) schedule together with diphtheria-tetanus-pertussis, hepatitis B and oral poliomyelitis vaccines. Sera were collected at 6 weeks and 1 month after each vaccination. Anti-Hib polysaccharide antibody concentrations were determined by Farrtype radioimmunoassay (RIA) and enzymeimmunoassay (EIA), Following the first dose, the geometric mean concentrations (GMC, micrograms ml-1) for PRP-OMP, HbOC and PRP-T were 0.69, 0.27 and 0.38, respectively. After two doses, there was a significant response (P < 0.05) to PRP-OMP and PRP-T (0.89 and 1.47) but not for HbOC (0.37). Differences in the GMC after the primary series were significant (pairwise P < 0.05): GMC was highest for PRP-T (4.0), followed by HbOC (1.6) and PRP-OMP (1.1). All three Hib vaccines were immunogenic when given in the local EPI schedule in Filipino infants although significant differences in the kinetics and magnitude of antibody responses were noted. The anti-Hib antibody concentrations determined by RIA and EIA were also compared in order to validate the latter for use in laboratories where it is feasible. There was a good correlation (r2 = 76%; P = 0.0001) in the Hib antibody titres obtained by both assays.

Evaluation of sampling sites for detection of upper respiratory tract carriage of Streptococcus pneumoniae and Haemophilus influenzae among healthy Filipino infants.

Two sampling techniques, nasal swabbing and oropharyngeal swabbing, for detection of the upper respiratory tract carriage of Streptococcus pneumoniae and Haemophilus influenzae were studied prospectively with 296 healthy Filipino infants at various ages: 6 to 8, 10 to 12, 14 to 17, 18 to 22, 32 to 39, and 46 to 65 weeks. In all age groups S. pneumoniae was isolated significantly more often (P < 0.0001) from the nasal site than from the oropharyngeal site. H. influenzae was found equally often at both sites.

Patterns of acute respiratory tract infection in children: a longitudinal study in a depressed community in Metro Manila.

The incidences of acute respiratory tract infection (ARI) and acute lower respiratory infection (ALRI) were 6.1 and 0.5 per child-year, respectively, in children less than 5 years old in a depressed urban community in Manila. The peak age-specific incidence occurred in those children 6-23 months old for ARI and 6-11 months old for ALRI. Age less than 2 years, malnutrition, household crowding, and parental smoking were associated with a statistically significant, though modest, increase in ARI morbidity. The crude mortality rate was 14.3 per 1,000 children 0-4 years old, with a corresponding ARI-specific mortality rate of 8.9 per 1,000. The prevalence of viral infection was 32.8 and that of bacteremic ALRI was 6.7 per 1,000 children with moderate ALRI. Respiratory syncytial virus was the predominant viral pathogen, while Streptococcus pneumoniae, Haemophilus influenzae, and Staphylococcus aureus were the most frequently isolated bacterial pathogens. Transmission of respiratory pathogens in depressed communities, facilitated by inadequate housing, inaccessible health services, and prevalent malnutrition, will continue unless meaningful socioeconomic improvement is realized.