First report of the novel pathogenicity Island of Adhesion and Autoaggregation (LAA) in Shiga toxin-producing Escherichia coli LEE negatives from Argentina

MONTERO, D.A.; DEL CANTO, F.; PADOLA, N.L.; COLELLO, R.; GONZÁLEZ, J.; ETCHEVERRIA, A.; VELEZ, M.V.; BUSTAMANTE, A.V.; VIDAL, R.

Florencia

Simposio; 10th International Symposium of VTEC 2018; 2018

VTEC

IntroductionShiga toxin, the virulence factor attributed to the progression of hemolytic uremic syndrome (HUS), can be identified in two major antigenic forms, Stx1 and Stx2. The ability to adhere to epithelial cells is an important virulence trait, because adherence presumably enables to deliver toxins efficiently to host organs. A pathogenicity island (PAI) named the locus of enterocyte effacement (LEE) governs the adherence in STEC LEE positives. However, the presence of LEE is not essential for pathogenesis, considering that some LEE negatives STEC have been associated with SUH. In recent discovery researchers identified a member of the Heat-resistant agglutinin family and characterized this antigen named Hemagglutinin from Shiga toxin-producing E. coli (Hes). More importantly, they show that the hes and other genes such as iha, pagC, ag43 were integrated in each of the four modules present in the new Island named Locus of Adhesion and Autoaggregation (LAA) whose presence is associated with severe disease. MethodsA total of 354 STEC LEE negative strains were selected. The STEC strains were isolated from cattle (dairy and beef cattle), farm environment and food (meat, hamburger and chicken hamburger) between 2000 and 2015 in Argentina. The STEC strains were characterized by PCR to detect three modules of LAA (I, II, III) and hes, iha, lesP, pagC, tpsA, ag43 (as marker of module IV). Results LAA was found in 44% of STEC LEE negatives corresponding to O91 (81%); O174 (69%); O113 (67%); O171 (67%); O178 (66%); O117 (43%); O130 (26%) and O141 (11%). The presence of this PAI is associated with strains harboring stx2 (56%) and belonging to phylogroup B1 (90%). According to the origin, STEC strains LEE negatives isolated from food and adult cattle carry LAA more than strains isolated from calves. Ninety percent of the strains carrying hes and /or module I had the complete PAI. When each module of LAA was detected independently or in combination between them in different frequencies STEC were considered LAA negatives.ConclusionsLAA is a novel pathogenicity island associated with strains isolated from SUH cases. This first reports show that LAA is widely distributed among STEC LEE negative strains from different origins. LAA or hes should be detected as predictor of virulence of STEC LEE negatives.