Takarn Piyawan, Tharavichitkul Prasit, Malasao Rungnapa, Boonthum Anusorn
Clin Lab. 2019 Apr 1;65(4). doi: 10.7754/Clin.Lab.2018.180902.
Streptococcus gallolyticus subspecies (subsp.) pasteurianus, previously known as Streptococcus bovis biotype II/2, has been described as a causative agent of endocarditis, neonatal sepsis, meningitis, bacteremia, and colorectal carcinoma in humans. The aim of this study was to characterize the erythromycin and tetracycline resistance genes of S. gallolyticus subsp. pasteurianus strains isolated from patients with septicemia and bacteremia in Thailand.
The clinical isolates of Streptococcus gallolyticus were identified by using conventional biochemical tests, PCR, and sodA gene sequence analysis. The erythromycin and tetracycline susceptibilities were determined by disk diffusion and agar dilution methods, while the resistance genes were identified by nucleotide sequence analysis.
From a total of 108 blood cultures, 36 (33%) were identified as S. gallolyticus subsp. pasteurianus with the nucleotide sequence identities of partial sodA gene with the reference strains ranging from 98.1 to 100%. Of these, 25 (69.4%) contained erythromycin resistance genes and erm(B) was the most predominant gene (30.6%), followed by erm(T) (19.4%) and mef(A) (5.6%). In addition, erm(B) was also detected in combination with lnu(B) (8.3%), erm(T) and mef(A) (2.8%), and mef(A) and lnu(B) (2.8%). It was interesting to note that lnu(B) was detected for the first time in S. gallolyticus subsp. pasteurianus in this study. For tetracycline resistance genes, tet(L) and tet(M) were detected at 13.9% and 11.1%, respectively. However, tet(M) in combination with tet(L) was detected most commonly at 69.4% and with tet(L) and tet(O) at 5.6%.
A number of erythromycin and tetracycline resistance genes were detected in S. gallolyticus subsp. pasteurianus strains circulating in Thailand.
解脲链球菌巴氏亚种，以前称为牛链球菌生物型II/2，已被描述为人类心内膜炎、新生儿败血症、脑膜炎、菌血症和结直肠癌的病原体。本研究的目的是对从泰国败血症和菌血症患者中分离出的解脲链球菌巴氏亚种菌株的红霉素和四环素抗性基因进行表征。
采用常规生化试验、聚合酶链反应（PCR）和sodA基因序列分析对解脲链球菌临床分离株进行鉴定。通过纸片扩散法和琼脂稀释法测定红霉素和四环素敏感性，同时通过核苷酸序列分析鉴定抗性基因。
在总共108份血培养物中，36份（33%）被鉴定为解脲链球菌巴氏亚种，其部分sodA基因与参考菌株的核苷酸序列同一性在98.1%至100%之间。其中，25份（69.4%）含有红霉素抗性基因，erm(B)是最主要的基因（30.6%），其次是erm(T)（19.4%）和mef(A)（5.6%）。此外，还检测到erm(B)与lnu(B)（8.3%）、erm(T)和mef(A)（2.8%）以及mef(A)和lnu(B)（2.8%）同时存在。有趣的是，本研究中首次在解脲链球菌巴氏亚种中检测到lnu(B)。对于四环素抗性基因，tet(L)和tet(M)的检测率分别为13.9%和11.1%。然而，tet(M)与tet(L)同时存在的情况最为常见，为69.4%，tet(M)与tet(L)和tet(O)同时存在的情况为5.6%。
在泰国流行的解脲链球菌巴氏亚种菌株中检测到了多种红霉素和四环素抗性基因。
