High rate of pneumococcal bacteremia in a prospective cohort of older children and adults in an area of high HIV prevalence in rural western Kenya
1 International Emerging Infections Program, Centers for Disease Control and Prevention, Mbagathi Road, off Mbagathi Way, Nairobi, Kenya
2 Kenya Medical Research Institute/Centers for Disease Control, Research and Public Health Collaboration, P.O. Box 1578, Kisumu, Kenya
3 Respiratory Diseases Branch, Division of Bacterial Diseases, Centers for Disease Control and Prevention, 1600 Clifton Rd. Atlanta, Georgia 30333
4 KEMRI/Wellcome Trust Research Programme, Centre for Geographic Medicine Research - Coast, Kilifi, Kenya
BMC Infectious Diseases 2010, 10:186 doi:10.1186/1471-2334-10-186Published: 23 June 2010
Although causing substantial morbidity, the burden of pneumococcal disease among older children and adults in Africa, particularly in rural settings, is not well-characterized. We evaluated pneumococcal bacteremia among 21,000 persons ≥5 years old in a prospective cohort as part of population-based infectious disease surveillance in rural western Kenya from October 2006-September 2008.
Blood cultures were done on patients meeting pre-defined criteria - severe acute respiratory illness (SARI), fever, and admission for any reason at a referral health facility within 5 kilometers of all 33 villages where surveillance took place. Serotyping of Streptococcus pneumoniae was done by latex agglutination and quellung reaction and antibiotic susceptibility testing was done using broth microdilution. We extrapolated incidence rates based on persons with compatible illnesses in the surveillance population who were not cultured. We estimated rates among HIV-infected persons based on community HIV prevalence. We projected the national burden of pneumococcal bacteremia cases based on these rates.
Among 1,301 blood cultures among persons ≥5 years, 52 (4%) yielded pneumococcus, which was the most common bacteria isolated. The yield was higher among those ≥18 years than 5-17 years (6.9% versus 1.6%, p < 0.001). The highest yield was for inpatients with SARI (10%), compared with SARI outpatients (3%) and acute febrile outpatients (1%). Serotype 1 pneumococcus was most common (42% isolates) and 71% were serotypes included in the 10-valent pneumococcal conjugate vaccine (PCV10). Non-susceptibility to beta-lactam antibiotics was low (<5%), but to trimethoprim-sulfamethoxazole was high (>95%). The crude rate of pneumococcal bacteremia was 129/100,000 person-years, and the adjusted rate was 419/100,000 person-years. Nineteen (61%) of 31 patients with HIV results were HIV-positive. The adjusted rate among HIV-infected persons was 2,399/100,000 person-years (Rate ratio versus HIV-negative adults, 19.7, 95% CI 12.4-31.1). We project 58,483 cases of pneumococcal bacteremia will occur in Kenyan adults in 2010.
Pneumococcal bacteremia rates were high among persons ≥5 years old, particularly among HIV-infected persons. Ongoing surveillance will document if expanded use of highly-active antiretroviral treatment for HIV and introduction of PCV10 for Kenyan children (anticipated in late 2010) result in substantial secondary benefits by reducing pneumococcal disease in adults.