Johnson James R, Clermont Olivier, Johnston Brian, Clabots Connie, Tchesnokova Veronika, Sokurenko Evgeni, Junka Adam F, Maczynska Beata, Denamur Erick
Veterans Affairs Medical Center, Minneapolis, Minnesota, USA.
J Clin Microbiol. 2014 May;52(5):1358-65. doi: 10.1128/JCM.03502-13. Epub 2014 Feb 5.
Escherichia coli sequence type 131 (ST131), a widely disseminated multidrug-resistant extraintestinal pathogen, typically exhibits serotype O25b:H4. However, certain ST131 isolates exhibit serotype O16:H5 and derive from a phylogenetic clade that is distinct from the classic O25b:H4 ST131 clade. Both clades are assigned to ST131 by the Achtman multilocus sequence typing (MLST) system and a screening PCR assay that targets ST131-specific sequence polymorphisms in the mdh and gyrB genes. However, they are classified as separate STs by the Pasteur Institute MLST system, and an ST131 PCR method that targets the O25b rfb region and an ST131-specific polymorphism in pabB detects only the O25b-associated clade. Here, we describe a novel PCR-based method that allows for rapid and specific detection of the O16-associated ST131 clade. The clade members uniformly contained allele 41 of fimH (type 1 fimbrial adhesin) and a narrow range of alleles of gyrA and parC (fluoroquinolone target genes). The virulence genotypes of the clade members resembled those of classic O25b:H4 ST131 isolates; representative isolates were variably lethal in a mouse subcutaneous sepsis model. Several pulsotypes spanned multiple sources (adults, children, pets, and human fecal samples) and locales. An analysis of recent clinical E. coli collections showed that the O16 ST131 clade is globally distributed, accounts for 1 to 5% of E. coli isolates overall, and, when compared with other ST131 isolates, it is associated with resistance to ampicillin, gentamicin, and trimethoprim-sulfamethoxazole and with susceptibility to fluoroquinolones and extended-spectrum cephalosporins. Attention to this O16-associated ST131 clade, which is facilitated by our novel PCR-based assay, is warranted in future epidemiological studies of ST131 and, conceivably, in clinical applications.
大肠杆菌序列类型131（ST131）是一种广泛传播的多重耐药性肠外病原体，通常表现为血清型O25b:H4。然而，某些ST131分离株表现为血清型O16:H5，并且源自一个与经典的O25b:H4 ST131进化枝不同的系统发育进化枝。这两个进化枝都通过阿赫特曼多位点序列分型（MLST）系统以及一种针对mdh和gyrB基因中ST131特异性序列多态性的筛选PCR检测法被归类为ST131。然而，它们在巴斯德研究所MLST系统中被分类为不同的序列类型，并且一种针对O25b rfb区域和pabB中ST131特异性多态性的ST131 PCR方法仅能检测到与O25b相关的进化枝。在此，我们描述了一种基于PCR的新方法，该方法能够快速、特异性地检测与O16相关的ST131进化枝。该进化枝成员一致含有fimH（1型菌毛黏附素）的等位基因41以及gyrA和parC（氟喹诺酮靶基因）的有限等位基因范围。该进化枝成员的毒力基因型与经典的O25b:H4 ST131分离株相似；代表性分离株在小鼠皮下败血症模型中具有不同程度的致死性。几种脉冲型跨越了多个来源（成人、儿童、宠物和人类粪便样本）和地区。对近期临床大肠杆菌样本的分析表明，O16 ST131进化枝在全球范围内分布，占大肠杆菌分离株总数的1%至5%，并且与其他ST131分离株相比，它与对氨苄西林、庆大霉素和甲氧苄啶 - 磺胺甲恶唑的耐药性以及对氟喹诺酮类和广谱头孢菌素的敏感性相关。在未来对ST131的流行病学研究以及可能的临床应用中，借助我们基于PCR的新检测法关注这个与O16相关的ST131进化枝是很有必要的。
