This study aimed to characterize in silico enterotoxigenic Escherichia coli F4- and F18-positive isolates (n = 90) causing swine postweaning diarrhea, including pathogenic potential, phylogenetic relationship, antimicrobial and biocide resistance, prophage content, and metal tolerance rates. F4 strains belonged mostly to the O149 and O6 serogroups and ST100 and ST48 sequence types (STs). F18 strains were mainly assigned to the O8 and O147 serogroups and ST10, ST23, and ST42. The highest rates of antimicrobial resistance were found against streptomycin, sulfamethoxazole, tetracycline, trimethoprim, and ampicillin. No resistance was found toward ciprofloxacin, cefotaxime, ceftiofur, and colistin. Genes conferring tolerance to copper (showing the highest diversity), cadmium, silver, and zinc were predicted in all genomes. Enterotoxin genes (ltcA, 100% F4, 62% F18; astA, 100% F4, 38.1% F18; sta, 18.8% F4, 38.1% F18; stb, 100% F4, 76.2% F18) and fimbria-encoding genes typed as F4ac and F18ac were detected in all strains, in addition to up to 16 other virulence genes in individual strains. Phage analysis predicted between 7 and 20 different prophage regions in each strain. A highly diverse variety of plasmids was found; IncFII, IncFIB, and IncFIC were prevalent among F4 isolates, while IncI1 and IncX1 were dominant among F18 strains. Interestingly, F4 isolates from the early 1990s belonged to the same clonal group detected for most of the F4 strains from 2018 to 2019 (ONT:H10-A-ST100-CH27-0). The small number of single-nucleotide polymorphism differences between the oldest and recent F4 ST100 isolates suggests a relatively stable genome. Overall, the isolates analyzed in this study showed remarkably different genetic traits depending on the fimbria type.

中文翻译：

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猪断奶后腹泻中产肠毒素的大肠杆菌F4和F18阳性菌株的基因组表征。

这项研究旨在鉴定在计算机上产生肠毒素的大肠杆菌F4-和F18阳性分离株（n= 90）引起猪断奶后腹泻，包括致病潜能，系统发育关系，抗微生物和杀生物剂耐药性，原噬菌体含量和金属耐受率。F4菌株主要属于O149和O6血清群以及ST100和ST48序列类型（STs）。F18菌株主要分为O8和O147血清群以及ST10，ST23和ST42。发现对链霉素，磺胺甲恶唑，四环素，甲氧苄啶和氨苄青霉素的抗药性最高。没有发现对环丙沙星，头孢噻肟，头孢噻呋和粘菌素有抗药性。在所有基因组中都预测了赋予铜（显示最高多样性），镉，银和锌耐受性的基因。肠毒素基因（ltcA，100％F4，62％F18; astA，100％F4，38.1％F18;sta，F4 18.8％，F18 38.1％; 机顶盒，100％F4、76.2％F18）和菌丝编码基因（分别为F4ac和F18ac）以及单个菌株中多达16种其他毒力基因。噬菌体分析预测了每个菌株的7至20个不同的噬菌体区域。发现了多种多样的质粒。在F4分离株中，IncFII，IncFIB和IncFIC普遍存在，而在F18菌株中，IncI1和IncX1占主导地位。有趣的是，1990年代初的F4分离株属于2018年至2019年检测到的大多数F4菌株的同一克隆组（ONT：H10-A-ST100-CH27-0）。最老的F4 ST100分离株之间的少量单核苷酸多态性差异表明相对稳定的基因组。总的来说，在这项研究中分析的分离株显示出明显不同的遗传特性，这取决于菌毛的类型。