Zhu Yinchu, Zhang Yue, Ma Jiale, Dong Wenyang, Zhong Xiaojun, Pan Zihao, Yao Huochun
College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, China.
OIE Reference Lab for Swine Streptococcosis, Nanjing, China.
Front Microbiol. 2019 Feb 26;10:274. doi: 10.3389/fmicb.2019.00274. eCollection 2019.
serotype 5, an emerging zoonosis bacterial pathogen, has been isolated from infections in both pigs and humans. In this study, we sequenced the first complete genome of a virulent, multidrug-resistant SS5 strain HN105. The strain HN105 displayed enhanced pathogenicity in zebrafish and BABL/c mouse infection models. Comparative genome analysis identified a novel 80K integrative conjugative element (ICE), ICESsuHN105, as required for the multidrug resistance phenotype. Six corresponding antibiotic resistance genes in this ICE were identified, namely (O), (M), (two copies), , and . Phylogenetic analysis classified the element as a homolog of the ICESa2603 family, containing the typical family backbone and insertion DNA. DNA hybrids mediated by natural transformation between HN105 and ZY05719 verified the antibiotic resistant genes of ICESsuHN105 that could be transferred successfully, while they were dispersedly inserted with a single gene in different genomic locations of ZY05719 transformants. To further identify the horizontal transfer of ICESsuHN105 as a whole mobile genetic element, a circular intermediate form of ICESsuHN105 was detected by PCR. However, the effective conjugation using serotype 2 as recipients was not observed in current assays . Further studies confirmed the presence of the complete lantibiotic locus encoded in ICESsuHN105 that effectively inhibits the growth of other streptococci. In summary, this study demonstrated the presence of antibiotic resistance genes in ICE that are able to transfer between different clinical isolates and adapt to a broader range of serotype or species.
血清型5是一种新出现的人畜共患病细菌病原体，已从猪和人类感染中分离出来。在本研究中，我们对一株强毒、多重耐药的SS5菌株HN105进行了首个全基因组测序。菌株HN105在斑马鱼和BABL/c小鼠感染模型中表现出增强的致病性。比较基因组分析确定了一种新型的80K整合接合元件（ICE），即ICESsuHN105，它是多重耐药表型所必需的。在该ICE中鉴定出六个相应的抗生素抗性基因，即（O）、（M）、（两个拷贝）、、和。系统发育分析将该元件归类为ICESa2603家族的同源物，包含典型的家族主干和插入DNA。由自然转化介导的HN105和ZY05719之间的DNA杂交验证了ICESsuHN105的抗生素抗性基因可以成功转移，而它们在ZY05719转化体的不同基因组位置以单个基因分散插入。为了进一步确定ICESsuHN105作为一个完整的可移动遗传元件的水平转移，通过PCR检测到了ICESsuHN105的环状中间形式。然而，在目前的试验中未观察到以血清型2作为受体的有效接合。进一步的研究证实了ICESsuHN105中编码的完整羊毛硫抗生素基因座的存在，该基因座可有效抑制其他链球菌的生长。总之，本研究证明了ICE中存在能够在不同临床分离株之间转移并适应更广泛血清型或物种的抗生素抗性基因。
