Because of their susceptibility to severe pneumococcal infection, children with sickle cell disease (SCD) are routinely placed on penicillin prophylaxis. Throughout the world increasing penicillin resistance of pneumococci has been reported thereby jeopardizing potential efficacy of this preventive intervention. The objective of the present study was to assess the prevalence and antimicrobial susceptibility of penicillin-resistant pneumococci colonizing children with sickle cell disease and to identify factors associated with their acquisition.

Nasopharyngeal cultures for Streptococcus pneumoniae were obtained from all children with sickle sell disease attending clinics in a statewide university based network. Background colonization rates were determined in children attending day care centers in some of the same locations. All recovered S. pneumoniae were tested for susceptibility to penicillin and all resistant strains were examined for susceptibility to other antibiotics.

Overall nasopharyngeal pneumococcal colonization rates among 351 children with sickle cell disease were 12% while in 245 controls was 35%. Colonization was associated with age < 2 years (P=0.0000001) and day care attendance>20 hours/wk (P=0.00005). More than half of these strains in SCD were resistant to penicillin, 33% having intermediate resistance (MIC 0.06-1μg/ml) and 29%, high level resistance (MIC ≥ 2.0μg/ml). Many of these organisms were also resistant to other classes of antibiotics.

Penicillin resistance was identified more frequently among isolates from sickle cell disease patients than controls, 62% vs 41%, P=0.01, although the overall prevalence of colonization with resistant strains was not different in the two groups, 7% vs 12%, P=0.05. The relative percentage of intermediate(54%) vs high-level resistance (46%) among total resistant strains was identical for patients and controls.

Although penicillin prophylaxis and pneumococcal vaccine for sickle cell disease patients have reduced overall nasopharyngeal colonization and disease caused by S. pneumoniae, a higher percentage of colonizing strains are now resistant to penicillin as well as other antimicrobial agents. Newer strategies for preventing disease and early management of suspected pneumococcal infection in these children must be developed.