Antibiotic resistance and serotypes of Streptococcus pneumoniae at Birmingham public health laboratory, 1989–94

Antibiotic resistance of 1515 consecutive laboratory isolates of Streptococcus pneumoniae between 1989 and 1994 was analyzed. Overall, 39 (2.6%) isolates were resistant to penicillin, 102 (6.7%) resistant to erythromycin and 52 (3.4%) resistant to tetracycline. There was a higher proportion of penicillin resistant isolates from sterile sites compared with "non-sterile sites" (5% vs. 2.2%; P vs. 5.6%; P One hundred and fifty isolates (9.9%) were serotyped, including isolates from sterile sites and those with penicillin resistance. The commonest serotypes of penicillin-sensitive pneumococci were 14, 19, 9 and 6. The majority of penicillin-resistant pneumococci (PRP) were of serotype 9 (64%) followed by 6, 23 and 19. Overall 95% of these isolates were of serotypes represented in the 23-valent pneumococcal polysaccharide vaccine (Pneumovax II). PRP were more likely to have resistance to erythromycin (2.3%) or tetracycline (2.3%) compared to penicillin-sensitive pneumococci (6% and 3% respectively). Most of the PRP were isolated from patients aged over 50 years including 11 isolates from blood cultures of patients with pneumonia or septicaemia. There was a possible epidemiological association between four patients with PRP but surveillance cultures of hospital contacts revealed no extra cases. These results show a worrying increase in infections due to PRP which has implications for clinical and laboratory staff in the diagnosis and treatment of serious pneumococcal infections.