Shiga Toxin-Producing Escherichia coli Isolated from Different Reservoirs Between 1998 and 2010 in Argentina

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

Amsterdam

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

Shiga toxin-producing Escherichia coli (STEC) is the most important emerging food-borne pathogen, and a major cause of gastroenteritis that may be complicated by hemorrhagiccolitis, or hemolytic uremic syndrome. As it has subsequently been found that healthy cattle can harbor the bacterium, ruminants are now regarded as its main reservoir, though STEC has been isolated from other animal species such as sheep, pigs, geese, gulls and pets. Transmission occurs through the consumption of undercooked meat, unpasteurized dairy products, and vegetables or water contaminated by animal feces. In Argentina, where HUS is endemic, approximately 400 new cases are reported annually. STEC O157:H7 is the predominant serotype isolated from clinical cases, but little is known about the dominant subtypes in the reservoir. The aim of this study was to characterize STEC strains from different animal reservoirs from 1998 to 2010.A collection of 698 STEC and non-toxigenic O157 strains isolated from cattle (n = 625), dogs (n = 22), wild ruminants (n = 21), sheeps (n = 11), goats (n = 4), rabbits (n = 8), cats (n = 4), chinchillas (n = 2) and seagull (n = 1) during surveys and research programs, were included. The strains were characterized by biochemical tests, serotyping, stx-genotyping, and pulsedfield gel electrophoresis (PFGE) using the 24-h PulseNet standardized protocol. The strains were grouped into 45 serogroups and 82 serotypes. The prevalent serotype was O157:H7 (18.1%) followed byO178:H19 (8%), ONT:H2 (6.6%), O8:H19 (6.2%), O130:H11 (4.7%), O103:NM (4%) and O113:H21 (3.6%). Other serotypes involved in human disease, such as O111:NM, O121:NM, O145:NM, O174:H21, O26:NM and O91:H21, were also found. STEC O157:H7 strains were isolated from cattle, rabbits, dogs and sheeps. The stxgenotyping showed that stx2 (64.3%) was prevalent, followed by stx1 and stx2 (22.3%), and stx1 (10.7%). Eighteen (2.6%) strains were non-toxigenic and 11 of them isolated from dogs belonged to O157:H16 serotype. Among the 126 STEC O157 strains, 54 XbaI-PFGE patterns were identified with at least 61.2% similarity. Ninety-four isolates were grouped in 21 clusters, while 32 strains showed unique patterns.Some XbaI-PFGE patterns established, including AREXHX01.0011 and AREXHX01.0022, are common in human disease. It is important to recognize that, though cattle are the main reservoir of STEC, other animals can harbor STEC. This should be considered in order to take different prevention measures when handling these animals.