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.
Chinen
I
I
Servicio Fisiopatogenia, Instituto Nacional de Enfermedades Infecciosas-ANLIS Carlos G. Malbrán, Buenos Aires, Argentina.
Tanaro
J D
JD
Miliwebsky
E
E
Lound
L H
LH
Chillemi
G
G
Ledri
S
S
Baschkier
A
A
Scarpin
M
M
Manfredi
E
E
Rivas
M
M
D001118:Argentina; D001434:Bacteriophage Typing / Q000379:methods; D016521:Electrophoresis, Gel, Pulsed-Field; D019453:Escherichia coli O157 / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D018189:Immunomagnetic Separation; D008460:Meat / Q000382:microbiology*; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D022603:Shiga Toxins / Q000235:genetics; D014774:Virulence
D022603:Shiga Toxins