Distribution of serotypes and antibiotic resistance among pneumococci in Northern Ireland.

Altogether, 488 consecutive strains of Streptococcus pneumoniae isolated from clinical specimens were serotyped and their antibiotic susceptibility determined. Of all strains isolated, 89.7% (90.6% for strains isolated from patients with serious infection) were of types present in the new polyvalent (23-valent) pneumococcal vaccine. Four strains showed reduced susceptibility to penicillin (minimum inhibitory concentration 0.1-1.0 mg/l). Two of those strains (both serotype 23) were also of intermediate susceptibility to other antibiotics (ampicillin, cephradine, chloramphenicol and tetracycline) but were sensitive to erythromycin. A significant proportion (12%) was resistant to tetracycline.