Julio Copes

Shiga toxin-producing Escherichia coli in beef retail markets from Argentina

Shiga toxin-producing Escherichia coli (STEC) are foodborne pathogens that cause mild or serious diseases and can lead to people death. This study reports the prevalence and characteristics of STEC O157 and non-O157 in commercial ground beef and environmental samples, including meat table, knife, meat mincing machine, and manipulator hands (n = 450) obtained from 90 retail markets over a nine-month period. The STEC isolates were serotyped and virulence genes as stx (Shiga toxin), rfbO157] (O157 lipopolysaccharide), fliCH7 (H7 flagellin), eae (intimin), ehxA (enterohemolysin) and saa (STEC autoagglutinating adhesin), were determined. STEC O157 were identified in 23 (25.5%) beef samples and 16 (4.4%) environmental samples, while STEC non-O157 were present in 47 (52.2%) and 182 (50.5%), respectively. Among 54 strains isolated, 17 were STEC O157:H7 and 37 were STEC non-O157. The prevalent genotype for O157 was stx2/eae/ehxA/fliCH7 (83.4%), and for STEC non-O157 the most frequent ones were stx1/stx2/saa/ehxA (29.7%); stx2 (29.7%); and stx2/saa/ehxA (27%). None of the STEC non-O157 strains were eae-positive. Besides O157:H7, other 20 different serotypes were identified, being O8:H19, O178:H19, and O174:H28 the prevalent. Strains belonging to the same serotype could be isolated from different sources of the same retail market. Also, the same serotype could be detected in different stores. In conclusion, screening techniques are increasingly sensitive, but the isolation of STEC non-O157 is still a challenge. Moreover, with the results obtained from the present work, although more studies are needed, cross-contamination between meat and the environment could be suspected.

Efecto de la adición de agua electroactivada a la bebida de bovinos de engorde a corral (feedlot), en un establecimiento de la provincia de Buenos Aires

espanolEl objetivo general del trabajo fue evaluar el efecto del consumo de agua electroactivada (AE) en bovinos de engorde a corral (feedlot); los objetivos particulares fueron: 1. determinar la presencia de E. coli O157 y de Salmonella spp. en materia fecal y 2. determinar su eficiencia como promotora de crecimiento. Se utilizaron 150 bovinos divididos en 4 lotes (L). El L1 fue tratado con 0,3 %, 1,5 % y 3,0 % de AE; el L2 con 0,3 % y 1,5 %; el L3 con 0,3 % y el L4 no fue tratado. En cada visita se pesaron los animales y se obtuvieron muestras de materia fecal, y en la ultima tambien de sangre. En materia fecal se determino la presencia de E. coli O157 y de Salmonella spp. En sangre se determinaron: pH, bicarbonato, sodio, potasio, cloro y hemoglobina total. Para el procesamiento de datos estadisticos se utilizo el programa Infostat. Con respecto a la ganancia de peso, la tendencia a favor del L2 y L3 a los 60 dias de tratamiento, podria deberse al efecto promotor de crecimiento por el consumo de AE. Las muestras de materia fecal resultaron positivas para E. coli O157 en 3,3 % para el L2 a los 60 dias, y para Salmonella spp. en 3,3 % y 1,6 % para los L3 y L4 a los 90 dias de tratamiento, respectivamente. No se evidenciaron alteraciones en los valores de referencia de los parametros sanguineos evaluados. La adicion de AE en el agua de bebida de bovinos de feedlot podria ser utilizada como promotora de crecimiento. EnglishThe general objective of the work was to evaluate the consumption of electroactivated water (AE) in feedlot cattle; the particular objectives were: 1. to determine the presence of E. coli O157 and Salmonella spp. in feces and 2. determine its efficiency as a promoter of growth. One hundred and fifty animals were grouped into 4 lots (L). The L1 was treated with 0.3 %, 1.5 % and 3.0 % of EAW; L2 with 0.3 % and 1.5 %; L3 with 0.3 % and L4 was not treated. In each of the 4 visits to the feedlot the animals were weighed and fecal samples were taken. Also, in the 4th visit, blood samples were taken. Fecal samples were analyzed to determine the presence of E. coli O157 and Salmonella spp. In the blood samples, pH, bicarbonate, sodium, potassium, chlorine, and total hemoglobin were determined. Data were analyzed using Infostat software. With respect to weight gain, tendency in favor of L2 and L3 after 60 days of treatment could be due to the growth promoter effect of EAW consumption. Fecal samples were positive for E. coli O157 in 3.3% for L2 at 60 days, and for Salmonella spp. in 3.3% and 1.6% for L3 and L4 after 90 days of treatment, respectively. No alterations were observed in the reference values of the evaluated blood parameters. The addition of EAW to the drinking water of feedlot cattle could be used as a growth promoter.