IGEVET   21075
INSTITUTO DE GENETICA VETERINARIA "ING. FERNANDO NOEL DULOUT"
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Detection of Escherichia coli Shiga Toxin-Producing in bovine feces and surface water streams in a cattle farm of Argentina.
Autor/es:
TANARO J.D., LEOTTA G.A., LOUND L., GALLI L., PIAGGIO M., CARBONARI C., IRINO K., RIVAS M.
Lugar:
Buenos Aires
Reunión:
Simposio; 7th International Symposium on Shiga Toxin (Verocytotoxin) - Producing Escherichia coli infections.; 2009
Resumen:
In Argentina Hemolytic Uremic Syndrome is endemic and the incidence rate is the highest in the world, 15 cases per 100,000 children under 5 years old. The aim of this work was to detect Shiga toxin-producing Escherichia coli (STEC) in bovine feces and surface water of a cattle-raising area in a farm of Argentina, to characterize the isolates and establish the clonal relationship by Pulsed-Field Gel Electrophoresis (PFGE). Between September 2005 and August 2006, 288 samples of bovine feces collected by rectal swabs and 79 samples of water taken with modified Moore swabs were studied in a cattle farm of Gualeguaychú, Argentina. Both samples were incubated at 42ºC for 24 h in modified EC broth with 20 mg/L of sodium novobiocine. After incubation, loops from each enrichment broth was streaking on MacConkey agar, simultaneously the immunomagnetic separation for E. coli O157 was performed. The immunoconcentrate was streaking in two media: O157:H7 ID™ and MacConkey sorbitol agar (Biokar) supplemented with 2.5 mg/L of potassium tellurite and 0.05 mg/L of cefixime (TC-SMAC). From all plates, the confluent growth zone and individual colonies were screened for stx1, stx2 and rfbO157 genes by a multiplex polymerase chain reaction (PCR). From each positive fecal and water sample, one stx-colony was selected for further characterization. Isolates were identified by biochemical tests, enterohemolysis, serotyping, and Stx production. Antimicrobial susceptibility was established according to CLSI/NCCLS standards and methods. Intimin (eae), ehxA and fliCH7 genes and stx variants were investigated. XbaI-PFGE was performed. PFGE images of gels were obtained and the analysis of TIFF images was carried out through the BioNumerics version 4.0 software package (Applied Maths, Kortrijk, Belgium) using the Dice coefficient and UPGMA to generate dendrograms with 1.5% tolerance values. In bovine samples, a prevalence of 39.6% (114/288) was found. Twenty five (31.6%) out of 79 water samples were stx-positive by PCR as screening method. Four strains (5.1%) could be recovered. The frequency of serotypes was 10% O157:H7, 6% O136:H12 and O178:H19, 3% O116:H21, 2% O107:H7, O113:H21, O163:H19, O179:H8, O8:H16, O113:H-, O124:H19, O141:H49 and O22:H8, 1% O130:H11, O15:H27, O174:H28, O2:H25, O22:H16, O7:H-, O79:H28, O8:H19 and O91:H21. The genotypes found were stx2c y stx1/eae/ehxA (13%), stx1/stx2/saa/ehxA (11%), stx2/saa/ehxA (10%), stx2d2 and stx1 (9%), rfbO157/fliCh7/stx1/stx2c/eae/ehxA and stx2c/stx2d2 (5%), stx2/stx2d2/saa, stx2/saa and stx2 (4%), and rfbO157/fliCh7/stx2c/eae/ehxA (3%). By XbaI-PFGE 59 patterns were established, grouped in 22 clusters. Thirty seven strains showed unrelated XbaI pattern. One strain of animal origin recovered in September 2005 and other strain of environmental origin detected in February 2006 showed identical genetic profile and indistinguishable PFGE pattern. Argentine cattle are an important reservoir of STEC and water may contribute to the transmission and maintenance of STEC in grazed cattle.