The aim of this paper is to describe a methodology applicable to the isolation of viable Escherichia coli O157 from beef carcasses and faecal samples and specifically to overcome problems of background flora outgrowth, which can reduce sensitivity of the test. 100 samples were collected in a slaughterhouse of province of Ravenna from December 2001 to January 2003, namely carcass samples and rectum content of 50 animals 2 x 2.5 cm fragments (tick <0.5 cm) were excised aseptically from rump, flank, brisket and neck before chilling. Faeces were taken with a sterile spoon after incision of rectum in the tripery. The entire pool of tissue fragments from each carcass (equivalent to 20 cm2) and 25 grams of faecal material were used to isolate Escherichia coli serotype O157 with the Laboratory Procedures MFLP-80 and MFLP-90 (Directorate’s-Health Canada’s). Faeces from cattle contain an huge number of bacteria, other then E.coli, that can survive/multiply in presence of Tryptone Soya Broth added with bile salts and novobiocin (20 mg/lt). Immunomagnetic enrichment procedure has proved useful to capture specifically E. coli O157, but other organisms were found in a great number, thus reducing the sensitivity of the test, even because diffusion of the fluorescent pigments in the Phenol Red Sorbitol Agar with MUG made it impossible to detect β-glucuronidase-negative colonies. HC agar with MUG proved to be more selective so decreasing background bacteria outgrowth. Besides the use of sterile swab instead of glass spatula and the technique of streaking helped very much in detection of isolated colonies on both agar media.
S. Albonetti, M. Trevisani, S. Alonso Alvarez, R. Rosmini (2004). RESEARCH OF ESCHERICHIA COLI SEROTYPE O157 IN BEEF CARCASSES AND FAECAL MATERIAL.
RESEARCH OF ESCHERICHIA COLI SEROTYPE O157 IN BEEF CARCASSES AND FAECAL MATERIAL
ALBONETTI, SABRINA;TREVISANI, MARCELLO;ALONSO ALVAREZ, SILVIA;ROSMINI, ROBERTO
2004
Abstract
The aim of this paper is to describe a methodology applicable to the isolation of viable Escherichia coli O157 from beef carcasses and faecal samples and specifically to overcome problems of background flora outgrowth, which can reduce sensitivity of the test. 100 samples were collected in a slaughterhouse of province of Ravenna from December 2001 to January 2003, namely carcass samples and rectum content of 50 animals 2 x 2.5 cm fragments (tick <0.5 cm) were excised aseptically from rump, flank, brisket and neck before chilling. Faeces were taken with a sterile spoon after incision of rectum in the tripery. The entire pool of tissue fragments from each carcass (equivalent to 20 cm2) and 25 grams of faecal material were used to isolate Escherichia coli serotype O157 with the Laboratory Procedures MFLP-80 and MFLP-90 (Directorate’s-Health Canada’s). Faeces from cattle contain an huge number of bacteria, other then E.coli, that can survive/multiply in presence of Tryptone Soya Broth added with bile salts and novobiocin (20 mg/lt). Immunomagnetic enrichment procedure has proved useful to capture specifically E. coli O157, but other organisms were found in a great number, thus reducing the sensitivity of the test, even because diffusion of the fluorescent pigments in the Phenol Red Sorbitol Agar with MUG made it impossible to detect β-glucuronidase-negative colonies. HC agar with MUG proved to be more selective so decreasing background bacteria outgrowth. Besides the use of sterile swab instead of glass spatula and the technique of streaking helped very much in detection of isolated colonies on both agar media.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
