M. Cornélis

Isolation and molecular characterization of Escherichia coli O157 isolated from cattle, pigs and chickens at slaughter

From 1999 until 2001, 3625 food samples were examined for the presence of Escherichia coli O157. Samples were from bovine origin (ground beef, n=549; carcasses, n=2452), calves (carcasses, n=147), chicken (breast, n=203; carcasses, n=71) and pigs (carcasses, n=85; trimmings, n=118). Vidas ECO detected 451 (12%) samples positive, but from only 27 (0.74%) samples was E. coli O157 isolated. One strain was isolated from bovine ground beef (0.18%), one from a pig carcass (1.17%) and all others were isolated from bovine carcasses (1.02%). All strains possessed the attaching-and-effacing gene, the enterohemorrhagic plasmid and verotoxin (VT) genes, except the strain isolated from the pig carcass that was therefore eliminated. Six of the strains were urease-positive. Strains were typed by two DNA fingerprinting methods: random amplification of polymorphic DNA (RAPD) and pulsed field gel electrophoresis (PFGE). PFGE revealed a similarity of 71.05%, while RAPD was 77.36% similar. None of the typing methods were able to classify all urease-positive strains to one pattern. Strains in the same PFGE cluster did not belong to one RAPD cluster. This paper highlights that Belgian fresh meat at retail level can be contaminated with E. coli O157 and that two different typing methods divide strains into different types.

Identification of "unknown analytes" in injection sites: a semi-quantitative interpretation

The analytical approach to the detection of residues of legally used veterinary medicinal products (VMPs) is similar to the approach of forbidden substances. The only difference lies in the quantitative component of the method. Since there is an evolution towards a different strategy in the screening for VMPs in matrices of slaughtered animals, a new approach was developed for determining the residues. The aim of this research was to create an efficient screening approach for determining the identity and/or quantity of legally and illegally used VMPs present at high concentrations in injection sites. The determination of these ‘unknown’ VMPs is combined with a fast report to the customer. Examples are given of the identification of phenylbutazone, penicillin G benzathine and florfenicol. For quantitative purposes, using a mini-validation procedure, concentrations far above the maximum residue limit (MRL) of the identified VMP can be reported. A quantitative validation normally consists of determining the required validation parameters at three levels: 1/2 MRL, MRL, 2 MRL. For highly concentrated injection sites, an alternative approach is proposed. The alternative validation consists of a comparison of the analyte concentration in the sample with the spike at the MRL and 10 times the MRL concentration.

New database on hormone and veterinary drug residue determination in animal products.

A new database was created which provides a carefully judged inventory of analytical methods available for the determination of residues of growth promoters (steroidal anabolic hormones, beta-agonists and glucocorticoids) and veterinary drugs (antibiotics and growth inhibitors), which are or will be regulated by EU legal acts. This database is available on the Internet at http:/(/)cemu10.fmv.ulg.ac.be/OSTC.