Increased activity of 16-membered lactone ring macrolides against erythromycin-resistant Streptococcus pyogenes and Streptococcus pneumoniae: characterization of South African isolates
Kp. Klugman et al., Increased activity of 16-membered lactone ring macrolides against erythromycin-resistant Streptococcus pyogenes and Streptococcus pneumoniae: characterization of South African isolates, J ANTIMICRO, 42(6), 1998, pp. 729-734
The susceptibility of 40 erythromycin-resistant isolates of Streptococcus p
yogenes and 40 multiply-resistant isolates of Streptococcus pneumoniae to s
ix macrolide antibiotics, representing 14-, 15- and 16-membered lactone rin
g structures, was tested. The genetic basis for macrolide resistance in the
strains was also determined. Both erm and mef determinants were encountere
d in the 36 S. pneumoniae Isolates tested, but only mef in the five S. pyog
enes isolates tested. All isolates showed cross-resistance among the 14-mem
bered macrolides erythromycin, clarithromycin and roxithromycin and the 15-
membered macrolide, azithromycin. However, the erythromycin-resistant S pyo
genes isolates retained full susceptibility to spiramycin and josamycin (16
-membered agents). These latter two antibiotics were also more active than
the other macrolides against erythromycin-resistant S. pneumoniae isolates,
especially josamycin which was 8-64 times more active than erythromycin; s
piramycin was only two to eight times more active than erythromycin.