Affiliation:
1. Department of Medical Microbiology, University of Aberdeen, Aberdeen AB25 2ZD, Scotland, United Kingdom
Abstract
ABSTRACT
Erythromycin-resistant isolates of
Streptococcus pneumoniae
from blood cultures and noninvasive sites were studied over a 3-year period. The prevalence of erythromycin resistance was 11.9% (19 of 160) in blood culture isolates but 4.2% (60 of 1,435) in noninvasive-site isolates. Sixty-two of the 79 resistant isolates were available for study. The M phenotype was responsible for 76% (47 of 62) of resistance, largely due to a serotype 14 clone, characterized by multilocus sequence typing as ST9, which accounted for 79% (37 of 47) of M phenotype resistance. The ST9 clone was 4.8 times more common in blood than in noninvasive sites. All M phenotype isolates were PCR positive for
mef
(A), but sequencing revealed that the ST9 clone possessed the
mef
(A) sequence commonly associated with
Streptococcus pyogenes
. All M phenotype isolates with this
mef
(A) sequence also had sequences consistent with the presence of the Tn
1207.1
genetic element inserted in the
celB
gene. In contrast, isolates with the
mef
(E) sequence normally associated with
S. pneumoniae
contained sequences consistent with the presence of the mega insertion element. All MLS
B
isolates carried
erm
(B), and two isolates carried both
erm
(B) and
mef
(E). Fourteen of the 15 MLS
B
isolates were tetracycline resistant and contained
tet
(M). However, six M phenotype isolates of serotypes 19 (two isolates) and 23 (four isolates) were also tetracycline resistant and contained
tet
(M). MICs for isolates with the
mef
(A) sequence were significantly higher than MICs for isolates with the
mef
(E) sequence (
P
< 0.001). Thus, the ST9 clone of
S. pneumoniae
is a significant cause of invasive pneumococcal disease in northeast Scotland and is the single most important contributor to M phenotype erythromycin resistance.
Publisher
American Society for Microbiology
Cited by
81 articles.
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