Prevalence and Characteristics of Plasmid-Encoded Serine Protease EspP in Clinical Shiga Toxin-Producing Escherichia coli Strains from Patients in Sweden

Shiga toxin-producing (STEC) infection can cause a broad spectrum of symptoms spanning from asymptomatic shedding to mild and bloody diarrhea (BD) and even life-threatening hemolytic-uremic syndrome (HUS). As a member of the serine protease autotransporters of (SPATE) family, EspP has the ability to degrade human coagulation factor V, leading to mucosal bleeding, and also plays a role in bacteria adhesion to the surface of host cells. Here, we investigated the prevalence and genetic diversity of among clinical STEC isolates from patients with mild diarrhea, BD, and HUS, as well as from asymptomatic individuals, and assessed the presence of and its subtypes in correlation to disease severity. We found that 130 out of 239 (54.4%) clinical STEC strains were positive, and the presence of was significantly associated with BD, HUS, and O157:H7 serotype. Eighteen unique genotypes (GTs) were identified and categorized into four subtypes, i.e., α (119, 91.5%), γ (5, 3.8%), δ (4, 3.1%), and ε (2, 1.5%). α was widely distributed, especially in strains from patients with BD and HUS, and correlated with serotype O157:H7. Serogroup O26, O145, O121, and O103 strains carried α only. Ten GTs were identified in α, and α/GT2 was significantly associated with severe disease, i.e., BD and HUS. Additionally, was strongly linked to the presence of gene, and the coexistence of α and / + was closely related to HUS status. To sum up, our data demonstrated a high prevalence and genetic diversity of the gene in clinical STEC strains in Sweden and revealed an association between the presence of , subtypes, and disease severity. , particularly the α subtype, was prone to be present in more virulent STEC strains, e.g., "top-six" serotypes strains.