Differences in virulence and drug resistance between <i>Clostridioides difficile</i> ST37 and ST1 isolates

One of the most common hospital-acquired infections is caused by toxigenic Clostridioides difficile. Although C. difficile ST37 only produces a functional toxin B, it causes disease as severe as that caused by hypervirulent ST1. We aim to compare the differences in virulence and drug resistance between ST37 and ST1 isolates. We conducted whole-genome sequencing on ST37 and ST1 isolates, analyzing their type-specific genes, and the distribution and mutation of genes related to virulence and antibiotic resistance. We compared the in vitro virulence-related phenotypes of ST37 and ST1 isolates, including: TcdB concentration, number of spores formed, aggregation rate, biofilm formation, swimming diameter in semi-solid medium, motility diameter on the surface of solid medium, and their resistance to 14 CDI-related antibiotics. We detected 4 ST37-specific genes related to adherence, including lytC, cbpA, CD3246, and srtB. We detected 97 virulence-related genes in ST37 isolates that exhibit genomic differences compared to ST1. ST37 isolates showed increased aggregation, biofilm formation, and surface motility compared to ST1 in vitro. Chloramphenicol resistance gene catQ and tetracycline resistance gene tetM are present in ST37 but absent in ST1 strains. The resistance rates of ST37 to chloramphenicol and tetracycline were 45.4% and 81.8%, respectively, whereas ST1 isolates were sensitive to both antibiotics. ST1 was more resistant to rifaximin than ST37. ST37 isolates showed stronger aggregation, biofilm formation and surface motility, and had higher resistance rates to chloramphenicol and tetracycline. ST1 isolates showed stronger ability to produce toxin and sporulation, and was highly resistant to rifaximin.产毒艰难梭菌（toxigenic Clostridioides difficile）是最为常见的医院获得性感染致病菌之一。尽管艰难梭菌ST37仅表达功能性毒素B（TcdB），但其引发的疾病严重程度可与高毒力ST1菌株相当。本研究旨在对比ST37与ST1分离株在毒力与耐药性层面的差异。我们对两类分离株开展全基因组测序（whole-genome sequencing），分析其菌株特异性基因，以及与毒力、抗生素耐药性相关基因的分布特征与突变情况。此外，我们还对比了ST37与ST1分离株的体外毒力相关表型，涵盖：TcdB浓度、孢子形成数量、聚集率、生物膜形成能力、半固体培养基内的泳动直径、固体培养基表面的运动直径，以及对14种艰难梭菌感染（Clostridioides difficile infection，CDI）相关抗生素的耐药性。经检测，共发现4个与黏附功能相关的ST37特异性基因，分别为lytC、cbpA、CD3246及srtB。相较于ST1菌株，ST37分离株中存在97个存在基因组差异的毒力相关基因。体外实验结果显示，ST37分离株的聚集能力、生物膜形成能力及表面运动能力均优于ST1菌株。ST37菌株携带有氯霉素耐药基因catQ与四环素耐药基因tetM，而ST1菌株则无此类耐药基因。ST37对氯霉素与四环素的耐药率分别为45.4%与81.8%，而ST1分离株对这两种抗生素均表现为敏感。ST1菌株对利福昔明的耐药性强于ST37。综上，ST37分离株具备更强的聚集能力、生物膜形成能力与表面运动能力，且对氯霉素、四环素的耐药率更高；而ST1分离株的毒素产生能力与孢子形成能力更强，且对利福昔明具有高度耐药性。