Identification, Shiga toxin subtypes and prevalence of minor serogroups of Shiga toxin-producing Escherichia coli in feedlot cattle feces

• Published in: Scientific reports 2021-04, Vol.11 (1), p.8601-8601, Article 8601
• Main Authors: Capps, Kaylen M., Ludwig, Justin B., Shridhar, Pragathi B., Shi, Xiaorong, Roberts, Elisabeth, DebRoy, Chitrita, Cernicchiaro, Natalia, Phebus, Randall K., Bai, Jianfa, Nagaraja, T. G.
• Format: Article
• Language: English
• Subjects: 631/326; 631/326/41; 631/326/41/1470; Cattle; E coli; Enteritis; Escherichia coli; Feces; Feedlots; Food contamination; Food sources; Foodborne pathogens; Genes; Hemolytic uremic syndrome; Hemorrhage; Hemorrhagic enteritis; Hindgut; Humanities and Social Sciences; Infections; multidisciplinary; Science; Science (multidisciplinary); Shiga toxin; Stx gene; Stx1 gene; Toxins; Virulence; Water pollution
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-021-87544-w

Shiga toxin-producing Escherichia coli (STEC) are foodborne pathogens that cause illnesses in humans ranging from mild to hemorrhagic enteritis with complications of hemolytic uremic syndrome and even death. Cattle are a major reservoir of STEC, which reside in the hindgut and are shed in the feces, a major source of food and water contaminations. Seven serogroups, O26, O45, O103, O111, O121, O145 and O157, called ‘top-7’, are responsible for the majority of human STEC infections in North America. Additionally, 151 serogroups of E. coli are known to carry Shiga toxin genes ( stx ). Not much is known about fecal shedding and prevalence and virulence potential of STEC other than the top-7. Our primary objectives were to identify serogroups of STEC strains, other than the top-7, isolated from cattle feces and subtype stx genes to assess their virulence potential. Additional objective was to develop and validate a novel multiplex PCR assay to detect and determine prevalence of six serogroups, O2, O74, O109, O131, O168, and O171, in cattle feces. A total of 351 strains, positive for stx gene and negative for the top-7 serogroups, isolated from feedlot cattle feces were used in the study. Of the 351 strains, 291 belonged to 16 serogroups and 60 could not be serogrouped. Among the 351 strains, 63 (17.9%) carried stx 1 gene and 300 (82.1%) carried stx 2, including 12 strains positive for both. The majority of the stx 1 and stx 2 were of stx 1a (47/63; 74.6%) and stx 2a subtypes (234/300; 78%), respectively, which are often associated with human infections. A novel multiplex PCR assay developed and validated to detect six serogroups, O2, O74, O109, O131, O168, and O171, which accounted for 86.9% of the STEC strains identified, was utilized to determine their prevalence in fecal samples (n = 576) collected from a commercial feedlot. Four serogroups, O2, O109, O168, and O171 were identified as the dominant serogroups prevalent in cattle feces. In conclusion, cattle shed in the feces a number of STEC serogroups, other than the top-7, and the majority of the strains isolated possessed stx 2, particularly of the subtype 2a, suggesting their potential risk to cause human infections.