Molecular basis and clonal nature of increasing pneumococcal macrolide resistance in South Africa, 2000–2005

The prevalence and molecular epidemiology of pneumococcal macrolide resistance in South Africa was investigated. Minimum inhibitory concentrations and serotypes of pneumococcal isolates causing invasive disease from 2000–2005 (n = 15 982), collected through a national laboratory-based surveillance system, were determined. Randomly selected isolates from 2005 (51%; 260/508) had resistance mechanisms determined, and clonality was investigated by pulsed-field gel electrophoresis (PFGE) (n = 64) and multilocus sequence typing (n = 7). Macrolide resistance increased from 9% (160/1828) in 2000 to 14% (508/3656) in 2005 (P < 0.001). Serotype 14 was the most common macrolide-resistant serotype (40%; 760/1921). The majority of macrolide-resistant isolates (75%; 1437/1921) displayed the macrolide–lincosamide–streptogramin B (MLSB) phenotype. Of the strains screened genotypically, 57% (147/260) contained erm(B), 27% (71/260) contained mef(A) and 15% (40/260) contained erm(B) and mef(A); 1% (2/260) contained ribosomal mutations. Macrolide-resistant isolates were predominantly penicillin-non-susceptible and multidrug-resistant. Isolates clustered according to serotype by PFGE, and 22% (14/64), 11% (7/64) and 5% (3/64) of isolates were related to the Taiwan19F-14, England14-9 and Spain9V-3 global clones, respectively. Routine use of the 7-valent pneumococcal conjugate vaccine (PCV-7) could reduce the burden of macrolide-resistant pneumococcal disease in South Africa.