Mi. Morosini et al., In vitro activity of telithromycin against Spanish Streptococcus pneumoniae isolates with characterized macrolide resistance mechanisms, ANTIM AG CH, 45(9), 2001, pp. 2427-2431
The susceptibilities to telithromycin of 203 Streptococcus pneumoniae isola
tes prospectively collected during 1999 and 2000 front 14 different geograp
hical areas in Spain were tested and compared with those to erythromycin A,
clindamycin, quinupristin-dalfopristin, penicillin G, cefotaxime, and levo
floxacin. Telithromycin was active against 98.9% of isolates (MICs, less th
an or equal to0.5 mug/ml), with MICs at which 90% of isolates are inhibited
being 0.06 mug/ml, irrespective of the resistance genotype. The correspond
ing values for erythromycin were 61.0% (MICs, less than or equal to0.25 mug
/ml) and > 64 mug/ml. The erm(B) gene (macrolide-lincosamide-streptogramin
B resistance phenotype) was detected in 36.4% (n = 74) of the isolates, whi
ch corresponded to 93.6% of erythromycin-intermediate and -resistant isolat
es, whereas the mef(A) gene (M phenotype [resistance to erythromycin and su
sceptibility to clindamycin and spiramycin without blunting]) was present i
n only 2.4% (it = 5) of the isolates. One of the latter isolates also carri
ed erm(B). Interestingly, in one isolate for which the erythromycin MIC was
2 mug/ml, none of these resistance genes could be detected. Erythromycin M
ICs for S. pneumoniae crm(B)-positive isolates were higher (range, 0.5 to >
64 mug/ml) than those for erm(B)- and mef(A) -negative isolates (range, 0.
008 to 2 mug/ml). The corresponding values for telithromycin were lower for
both groups, with ranges of 0.004 to 1 and 0.002 to 0.06 mug/ml, respectiv
ely. The erythromycin MIC was high for a large number of erm (B) -positive
isolates, but the telithromycin MIC was low for these isolates. These resul
ts indicate the potential usefulness of telithromycin for the treatment of
infections caused by erythromycin-susceptible and -resistant S. pneumoniae
isolates when macrolides are indicated.