Serotype and antimicrobial susceptibility patterns of isolates of Streptococcus pneumoniae causing invasive disease in The Gambia 1996–2003

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Abstract
Summary: Objectives  To describe the characteristics of pneumococcal isolates obtained from patients with invasive pneumococcal disease in The Gambia.Methods  Pneumococcal isolates were obtained from children aged ≤6 years with invasive pneumococcal disease during a Haemophilus influenzae vaccine effectiveness study (1997–2002) and from patients with invasive pneumococcal disease admitted to the MRC hospital, Fajara, for routine care (1996–2003). Isolates were identified, serotyped and tested for antibiotic susceptibility.Results  Five hundred and thirty one pneumococcal isolates were obtained from 518 patients; 55 (10.6%) patients died; 415 isolates (79%) were from blood culture, 84 (16%) from CSF, and 42 (8%) from lung aspirates. Forty serogroups and serotypes were identified; six accounted for 64% and 16 for 86% of all episodes; 33.7% were of serotypes 1 and 5. 23.5% were of a 7‐valent vaccine serotype, 57.1% were of a 9‐valent vaccine serotype; 56% were of a 7‐valent serogroup and 78% were of a 9‐valent serogroup. There was a significant increase in the proportion of isolates of non‐vaccine serogroup with increasing age (P < 0.0001). Antibiotic resistance had not significantly increased over time; but intermediate non‐susceptibility to penicillin had risen and resistance to chloramphenicol had fallen in isolates of vaccine serotype compared with those of non‐vaccine serotype.Conclusions  The majority of invasive pneumococcal disease in The Gambia is caused by pneumococci of relatively few serogroups. A conjugate vaccine would be expected to reduce the pneumococcal disease burden substantially and to have a beneficial effect on pneumococcal antibiotic resistance to penicillins.