Erythromycin-resistant genes in group A β-haemolytic Streptococci in Chengdu, Southwestern China.
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Date
2014-07
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Abstract
Context: The management of Group A β‑haemolytic Streptococci (Streptococcus pyogenes or GAS) infection
include the use of penicillins, cephalosporins or macrolides for treatment. A general increase in macrolides resistance
in GAS has been observed in recent years. Differences in rates of resistance to these agents have existed according
to geographical location and investigators. Aims: To investigate the antibiotic pattern and erythromycin‑resistant
genes of GAS isolates associated with acute tonsillitis and scarlet fever in Chengdu, southwestern China.
Settings and Design: To assess the macrolide resistance, phenotype, and genotypic characterization of GAS isolated
from throat swabs of children suffering from different acute tonsillitis or scarlet fever between 2004 and 2011 in the city
of Chengdu, located in the southwestern region of China. Materials and Methods: Minimal inhibitory concentration
with seven antibiotics was performed on 127 GAS isolates. Resistance phenotypes of erythromycin‑resistant GAS
isolates were determined by the double‑disk test. Their macrolide‑resistant genes (mefA, ermB and ermTR) were
amplified by PCR. Results: A total of 98.4% (125/127) of the isolates exhibited resistance to erythromycin, clindamycin
and tetracycline. All isolates were sensitive to penicillin G and cefotaxime. Moreover, 113 ermB‑positive isolates
demonstrating the cMLS phenotype of erythromycin resistance were predominant (90.4%) and these isolates showed
high‑level resistance to both erythromycin and clindamycin (MIC90 > 256 μg/ml); 12 (9.6%) isolates demonstrating
the MLS phenotype of erythromycin resistance carried the mefA gene, which showed low‑level resistance to both
erythromycin (MIC90 = 8 μg/ml) and clindamycin (MIC90 = 0.5 μg/ml); and none of the isolates exhibited the M
phenotype. Conclusions: The main phenotype is cMLS, and the ermB gene code is the main resistance mechanism
against macrolides in GAS. Penicillin is the most beneficial for treating GAS infection, and is still used as first‑line
treatment. And macrolide antibiotics are not recommended for treatment of GAS infection in children because of the
high rates of antimicrobial resistance in mainland China.
Description
Keywords
Child/children, genotype, group A β‑haemolytic streptococcus, phenotype, resistence, streptococcus pyogenes
Citation
Zhou W, Jiang Y M, Wang H J, Kuang L H, Hu Z Q, Shi H, Shu M, Wan C M. Erythromycin-resistant genes in group A β-haemolytic Streptococci in Chengdu, Southwestern China. Indian Journal of Medical Microbiology. 2014 Jul-Sept ; 32 (3): 290-293.