Trends in antimicrobial resistance and serotype distribution of blood and cerebrospinal fluid isolates of Streptococcus pneumoniae in South Africa, 1991-1998.

OBJECTIVE: Since 1979, the South African Institute for Medical Research (SAIMR) has served as the national reference center for pneumococcal serotyping and monitoring of antibiotic resistance trends. This study documents trends in antimicrobial resistance in pneumococci isolated from blood or cerebrospinal fluid (CSF) between 1991 and 1998 in South Africa.
METHODS: Pneumococcal isolates (n = 7406) from either blood or CSF were sent to the SAIMR reference laboratory for serotyping. The isolates were evaluated for resistance to penicillin, chloramphenicol, tetracycline, erythromycin, clindamycin, and rifampicin.
RESULTS: Resistance to one or more antibiotics increased significantly from 19% in 1991 to 1994 to 25% in 1995 to 1998 in all ages, and in children from 32% to 38% (P < 10[-6]). Although penicillin resistance did not increase in children (28.1% vs. 28.9%), penicillin resistance in all ages increased from 9.6% to 18.0%. Significant increases in resistance to chloramphenicol, tetracycline, erythromycin, and rifampicin also were seen in both groups. Multiple resistance increased significantly, from 2.2% to 3.8%. The proportion of isolates with intermediate or high-level penicillin resistance remained constant during the surveillance period. Erythromycin resistance, predominantly expressed as simultaneous resistance to erythromycin and clindamycin, increased from 1.6% to 2.6%. The percentage of erythromycin-resistant isolates that were resistance to erythromycin alone increased from 10.6% to 28.7%, suggesting the emergence of mefE-mediated resistance. In children 2 years of age and younger, although serogroup 6 remained the most common, there were significant increases in serogroups 19, 18, and 13. The percentage of the total invasive pneumococcal disease in this population that is caused by serogroups found in the nonavalent pneumococcal conjugate vaccine (serogroups 1, 4, 5, 6B, 9V, 14, 18C, 19F, 23F) increased from 72% to 91%.
CONCLUSIONS: Antibiotic resistance in the pneumococcus is increasing in South Africa, although the proportion of strains with high-level penicillin resistance has not increased. New conjugate vaccines may not only decrease the burden of all pneumococcal disease but, in addition, lower the incidence of antibiotic-resistant disease in South Africa.