LEE-Negative Shiga Toxin-Producing Escherichia coli Strains Associated with Human Disease in Argentina

CARBONARI CC; MILIWEBSKY E; CHINEN I; DEZA N; D´ASTEK BA; MANFREDI E; GALLI L; BASCHKIER A; ZOLEZZI G; RIVAS M

Amsterdam

Simposio; 8th International Symposium on Shiga toxin (Verocytotoxin) Producing Escherichia coli Infections; 2012

In Argentina, Shiga toxin-producingEscherichia coli (STEC) O157:H7 is the prevalent serotype associatedwith outbreaks and sporadic cases of diarrhea (D), bloody diarrhea(BD) and hemolytic uremic syndrome (HUS). In addition, non-O157 STEC serotypes, described as highly virulent, are identifiedmainly as O145:NM, O26:H11, O103:H2, and O121:H19. However, LEE-negative strains with different virulence profiles are detectedwith a low frequency, associated to severe human disease. The aim of this study was to characterize LEE-negative STEC strains isolatedfrom human disease in Argentina. Between 2000 and 2010, a total of 60 LEEnegativeSTEC strains were isolated from human disease: HUS (32), D (20), BD (7), and septicemia (1). STEC strains were phenotypicallyand genotypically characterized. The stx-genotyping was performedby PCR-RFLP, including the stx2dactivatable gene detection. The subtyping was done by pulsed-field gel electrophoresis (PFGE) using the 24-h PulseNet standardized protocol. A total of 16 different serotypes were detected: O91:H21 (7;11.6%), O174:H21 (6; 10%), O8:H19 (5; 8.3%), O8:H16 (3; 5%),O113:H21 (3; 5%), O174:NM (3; 5%), O15:H27 (2; 3.3%), O171:H2(2; 3.3%), O174:H28 (2; 3.3%), O20:H19 (1; 1.6%), O22:H8 (1;1.6%), O58:H40 (1; 1.6%), O91:NM (1; 1.6%), O113:H4 (1; 1.6%), O113:NM (1; 1.6%), O178:H19 (1; 1.6%). Some strains were nontypeable: ONT:NM (11; 18.3%), ONT:HNT (4; 6.6%), ONT:H19 (2;3.3%), O22:HNT (1; 1.6%), O113:HNT (1; 1.6%), ONT:H21 (1;1.6%). The predominant genotypes were: stx2d2 (20%), stx2 (13.3%),stx2d/ehxA (5%), stx2d2/ehxA (5%), stx2d/stx2d2/ehxA (3.3%), stx1/ehxA (3.3%). Out of 39 strains, 22 (56.4%) harbored the stx2dactivatablegene. Twelve (20%) strains were resistant to at least one of the antimicrobials tested. By XbaI-PFGE, the strains were highly diverse, 57strains yielded 48 patterns and three were non-typeable. LEE-negative STEC strains were isolated in Argentina, and some of them harbored the stx2dactivatable gene associated withsevere human disease. Specific methodologies are needed to improvelaboratory-based surveillance of non-O157 STEC infections.