Clonal diversity of Shiga toxin-producing Escherichia coli isolated from human cases, animal reservoirs and food products, in Argentina in 2005.

CHINEN I., ; MILIWEBSKY E., ; DEZA N., ; CARBONARI C., ; GUGLIADA J., ; MANFREDI E., ; BASCHKIER A., ; LEOTTA G.A., ; RIVAS M.

Melbourne, Australia.

Simposio; 6th International Symposium on Shiga Toxin (Verocytotoxin) - Producing Escherichia coli infections.; 2006

Hemolytic-uremic syndrome (HUS) has for many years been the most common cause of acute renal failure in childhood and infancy in Argentina. In 2005, 464 cases of HUS were reported by Hospital Nephrology Units and the annual incidence rate was 13.9 cases per 100,000 children under five years of age. Shiga toxin-producing Escherichia coli (STEC) O157:H7 was the prevalent serotype. To determine the diversity of the STEC strains isolated from different sources in Argentina in 2005, a total of 203 STEC strains (164 human specimens, 29 food products, 6 animal reservoirs, and 4 environmental samples) were studied. Among the human cases, 85 (52%) were associated with HUS. The strains were phenotypically and genotypically characterized, and subtiped by phage typing, stx genotyping and pulse-field gel electrophoresis (PFGE). A total of 128 strains were identified as STEC O157:H7. The 96.9% of these strains were isolated from human cases, and the genetic profile stx2/stx2vh-a, eae+, ehxA+, was the prevalent. These STEC O157 strains yielded a total of 74 XbaI-PFGE patterns, showing the high clonal diversity of the strains. Among the 40 non-O157 STEC strains of human origin, 18 (40%) were serotyped as O145:NM. Fourteen out of 19 HUS cases were associated with STEC strains stx2+, eae+, ehxA+, of different serotypes, however, the other 5 cases were related to STEC strains negative for eae. The most frequent serotypes isolated from food products were O8:H21, O20:H19, O91:H21, O103:H2, and O174:NM. The subtyping techniques confirmed the genetic diversity of the STEC strains of different serotypes. In conclusion, these results demonstrate that STEC strains are widespread in Argentina and infect animals and humans as well as contaminate food products. Therefore, control and preventive guidelines are necessary to reduce the burden of HUS and STEC infections in our country