Eduardo Manfredi

Isolation and characterization of Escherichia coli O157:H7 from retail meats in Argentina.

Between February and May 2000, 279 meat samples were collected from 136 retail stores in Gualeguaychú City, Argentina. Samples were assayed for Escherichia coli O157:H7 by selective enrichment in modified EC broth containing novobiocin, followed by immunomagnetic separation (IMS) and plating onto both sorbitol MacConkey agar supplemented with cefixime and potassium tellurite and a chromogenic medium. Eleven E. coli O157:H7 isolates were detected in 6 (3.8%) of 160 ground beef samples, in 4 (4.8%) of 83 fresh sausages, and in 1 (3.3%) of 30 dry sausages. E. coli O157:H7 was not isolated from five hamburger patties or one barbecue-type fresh sausage assayed. The isolates were tested for virulence-related genes. Ten additional Shiga toxin-producing E. coli (STEC) O157:H7 isolates of food origin, recovered from different locations in Argentina, were included for comparison purposes. All 21 isolates harbored both eae and EHEC-hlyA genes, and 12 (57.1%) encoded stx2/stx2vh-a. The isolates were of phage types 87 (seven strains), 14 (four strains), 4 (three strains), and 26 (one strain). Six strains were nontypable by phage typing. Pulsed-field gel electrophoresis (PFGE) revealed 19 XbaI-PFGE profiles. Fifteen (71%) strains were grouped in four clusters, which shared more than 80% of DNA restriction fragments. The enrichment culture method with IMS was a sensitive procedure to detect E. coli O157:H7 strains in retail meats. Some of the isolates from different stores presented a high clonal relatedness, as determined by XhaI-PFGE and phage typing, and harbored the virulence factors associated with human illness.

Shiga toxin-producing Escherichia coli O157 in beef and chicken burgers, and chicken carcasses in Buenos Aires, Argentina

We describe the isolation and characterization of Shiga toxin (Stx)-producing Escherichia coli (STEC) O157:H7 from cooked and uncooked beef and chicken burgers and from chicken carcasses collected during sampling procedures in 2001 and 2002 in Buenos Aires City, Argentina. Of the 24 STEC O157:H7 strains isolated, 20 were recovered from 19 (6.8%) out of 279 samples of beef and chicken burgers, and 4 strains from 4 (10.3%) out of 39 chicken carcasses. The samples were analyzed following the USDA/FSIS 2002 method. The prevalent stx genotype was stx(2) and stx(2c) (12 strains, 50%). All strains were characterized as eae and ehxA-positive. By XbaI-PFGE, the strains yielded 10 different patterns. Eighteen out of 24 strains were grouped in four clusters: #1 (4 strains, AREXHX01.0043), #2 (4 strains, AREXHX01.0022), #3 (8 strains, AREXHX01.0139), and #4 (2 strains, AREXHX01.0200). Identical strains by phage typing, stx genotyping and PFGE were detected in uncooked and cooked beef and chicken burgers in different restaurants, which had been collected on the same or different sampling dates. These findings help to underline the importance of STEC O157 detection in meat products, to improve active surveillance, and to define control strategies in order to prevent new cases of STEC infection.

Brote de intoxicación alimentaria asociado al consumo de leche ultrapasteurizada en la República del Paraguay

Durante marzo de 2007 ocurrio un brote epidemico asociado al consumo de leche ultrapasteurizada que afecto a las ciudades de San Lorenzo, Ciudad del Este y Asuncion, de la Republica del Paraguay. Las personas afectadas fueron 400, de las cuales 60 requirieron hospitalizacion. Se aislo S. aureus subespecie aureus de 5 pacientes, 3 operarios y 3 muestras de leche. Todas las cepas fueron productoras de enterotoxinas. Las aislamientos de 3 pacientes, de un operario y de las muestras de leche portaron los genes que codifican las enterotoxinas C (sec) y D (sed), y presentaron un patron unico de macrorrestriccion (SmaI-PFGE). Se identifico a la leche como fuente de intoxicacion y a un operario de la linea de produccion como origen de la contaminacion. Este es el primer brote de ETA denunciado en Paraguay en el cual se pudo aislar, caracterizar y subtipificar el agente etiologico en la planta de elaboracion, en el alimento y en las personas afectadas.

Subtyping of Escherichia coli O157:H7 Strains Isolated from Human Infections and Healthy Cattle in Argentina

Shiga toxin-producing Escherichia coli (STEC) cause nonbloody (NBD) and bloody diarrhea (BD), and hemolytic uremic syndrome (HUS). Cattle have been described as their main reservoir. STEC O157:H7 is recognized as the predominant serotype in clinical infections, but much less is known about the dominant subtypes in humans and animals or their genetic relatedness. The aims of this study were to compare the STEC O157 subtypes found in sporadic human infections with those in the bovine reservoir using stx-genotyping, phage typing, and XbaI-pulsed-field gel electrophoresis (PFGE), and correlate the subtypes with the severity of clinical manifestations. The 280 STEC O157:H7 strains collected included in this study were isolated from HUS (n=122), BD (n=69), and NBD (n=30) cases, and healthy carriers (n=5), and from bovines (n=54) in the abattoirs. The stx-genotyping showed that stx₂/stx(2c(vh-a)) was predominant in human (76.1%) and in bovine strains (55.5%), whereas the second more important genotype was stx₂ (20.8%) in human and stx(2c(vh-a)) (16.7%) in cattle strains. In human strains, PT4 (37.6%), PT49 (24.3%), and PT2 (18.6%) were the most frequent PTs (80.5%). In bovine isolates, PT2 (26%), PT39 (16.7%), and PT4 and PT49 (11.1% each) were predominant. By XbaI-PFGE, all 280 strains yielded 148 patterns with 75% similarity, and 169 strains were grouped in 37 clusters. Identical PT-PFGE-stx profile combinations were detected in strains of both origins: PT4-AREXH01.0011-stx₂/stx(2c(vh-a)) (12 humans and one bovine), PT4-AREXH01.0543-stx₂/stx(2c(vh-a)) (one human and four bovines), PT2-AREXH01.0076-stx₂/stx(2c(vh-a)) (one human and four bovines), PT49-AREXH01.0175-stx₂/stx(2c(vh-a)) (seven humans and one bovine), and PT49-AREXH01.0022-stx₂/stx(2c(vh-a)) (seven humans and one bovine). No correlation was found among the stx-genotypes, the phage type, and the clinical symptoms.

Characterization and Genetic Relationship of Shiga Toxin-Producing Escherichia Coli Strains Isolated From Food in Argentina, 1999-2013

Isabel Chinen, Elizabeth Miliwebsky, Claudia Carolina Carbonari, Beatriz D Astek, Gisela Zolezzi, Natalia Deza, Ariela Baschkier, Eduardo Manfredi, Marta Rivas. Characterization and Genetic Relationship of Shiga Toxin-Producing Escherichia coli Strains Isolated From Food in Argentina, 1999-2013. In: Anais do 12o Congresso Latinoamericano de Microbiologia e Higiene de Alimentos MICROAL 2014 [= Blucher Food Science Proceedings, num.1, vol.1]. Sao Paulo: Editora Blucher, 2014. DOI 10.5151/foodsci-microal-244 Characterization and Genetic Relationship of Shiga Toxin-Producing Escherichia coli Strains Isolated From Food in Argentina, 1999-2013