Identification of Streptococcus G and its drug resistance

doi:10.3969/j.issn.1673-8640.2016.09.019

Abstract

Abstract:

Objective To investigate the significance of 16S rDNA sequencing method in identifying beta-hemolytic Streptococcus G and determine the drug resistance of beta-hemolytic Streptococcus G to antibiotics,like penicillin,erythromycin and clindamycin,by in vitro drug susceptibility test,in order to determine the drug resistance phenotypes and genotypes of erythromycin-resistant isolates. Methods A total of 50 beta-hemolytic Streptococcus G isolates were collected from Fudan University Huashan Hospital,and they were identified by API 20 Strep Streptococcus identification system,Lancefield's streptococcal grouping test and 16S rDNA sequencing method. The in vitro drug susceptibility test was performed by agar dilution method. Erythromycin-resistant phenotypes were determined by D test. The drug resistance genes,ermB and mefA,were determined by polymerase chain reaction（PCR）. Results The 50 beta-hemolytic Streptococcus G isolates were identified by API 20 Strep Streptococcus identification system asStreptococcus dysgalactiae. For 16S rDNA sequencing method,there were 42 isolates of Streptococcus dysgalactiae and 8 isolates of Streptococcus anginosus,and the identification rate was >97%. 16S rDNA sequencing method was used as standard,and the identification accuracy of API 20 Strep Streptococcus identification system was 84%. The results of Lancefield's streptococcal grouping test were all group G. The results of drug susceptibility test showed that there was no levofloxacin-,ceftriaxone-,vancomycin- and penicillin-resistant isolates. Erythromycin resistance was found in 28 isolates（56%）,among them,there were 26 isolates（52%） with cMLs,2 isolates（4%） with Ms and no isolate with iMLs. Furthermore,4 isolates （8%） were intermediately resistant to erythromycin. A total of 31 isolates（62%） were clindamycin-resistant,among them,3 isolates（6%） were sensitive to erythromycin and resistant to clindamycin,and 2 isolates（4%） were intermediately resistant to erythromycin and resistant to clindamycin. All cMLs-resistant isolates carried ermB,and 2 Ms-resistant isolates carried mefA. There were 2 isolates of 4 isolates with intermediate resistance to erythromycin carried ermB and mefA,respectively. Conclusions 16S rDNA sequencing method could identify Streptococcus G. The drug resistance rates to erythromycin and clindamycin increase. However,all the isolates are sensitive to penicillin. The beta-lactam antibiotic may be the first choice for the treatment of Streptococcus G infection.

Key words: Streptococcus G, Drug susceptibility test, 16S rDNA, ermB, mefA

CLC Number:

R446.5

HE Lihua, NI Lijun, LIU Hong, WANG Bei, TIAN Yueru, GUO Jian, WU Wenjuan. Identification of Streptococcus G and its drug resistance[J]. Laboratory Medicine, 2016, 31(9): 820-824.

Figures/Tables 2

References 15

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抗菌药物	MIC解释标准（μg/mL）
抗菌药物	敏感	中介	耐药
红霉素	≤0.25	0.5	≥1
克林霉素	≤0.25	0.5	≥1
青霉素	≤0.12	-	-
万古霉素	≤1	-	-
左氧氟沙星	≤2	4	≥8
头孢曲松	≤0.5	-	-

抗菌药物	MIC解释标准（μg/mL）
抗菌药物	敏感	中介	耐药
红霉素	≤0.25	0.5	≥1
克林霉素	≤0.25	0.5	≥1
青霉素	≤0.12	-	-
万古霉素	≤1	-	-
左氧氟沙星	≤2	4	≥8
头孢曲松	≤0.5	-	-

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