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Listeria monocytogenes was isolated from 11/236 (4 x 7%) caecal samples from parent flocks, providing broilers to the abattoirs investigated. Caecal samples from 2078 broilers representing 90 randomly selected broiler flocks were negative for L. monocytogenes. A total of 3080 samples from seven abattoirs including poultry processing line samples, and final products were also examined for L. monocytogenes. Listeria monocytogenes was isolated in 0 x 3% to 18 x 7% of the samples collected in the different abattoirs. Epidemiological typing of 247 L. monocytogenes isolates, including serotyping, phage typing, pulsed-field gel electrophoresis and ribotyping revealed 62 different clones. Based upon typability and discriminatory power, DNA typing methods used were found equally suitable as epidemiological markers. Serotyping and phage typing were not found useful as epidemiological markers for poultry isolates of L. monocytogenes since only 120/247 (48 x 6%) isolates were typable by phage typing and 230/247 (93 x 1%) L. monocytogenes belonged to serotype 01 while 6/247 (2 x 4%) belonged to 04. The discovery of a few dominating clones in each abattoir might indicate an endemic occurrence of L. monocytogenes. It is concluded that L. monocytogenes in the broiler production is primarily localized to the abattoirs. The incidence of L. monocytogenes may be reduced by improving the hygiene.

Two different genotypic methods, colony hybridization and polymerase chain reaction (PCR), were applied to detect enterotoxin, verotoxin and fimbrial genes in 708 Escherichia coli (E. coli) strains from piglets with diarrhoea. The results were compared with those obtained by phenotypic methods. D N A fragments specific for each of the enterotoxins LT, ST, and ST,, the verotoxins VT,, VT, and VT,,, and for each of the fimbrial genes K88 (F4), K99 (F5), 987P (F6), F41 and F107, respectively, were used as probes in a colony hybridization assay of the E. coli strains. A PCR assay was used as genotypic test for the verotoxin gene. An Enzyme-linked immunosorbent assay (ELISA) using monoclonal antibodies was performed to test for the presence of K88 and K99 fimbriae, and a Vero cell test was performed to test for verotoxin production. Toxin detection kits were applied to detect the E. coli heat-labile enterotoxin (LT) and the heat-stable (ST,) enterotoxin. The correlation between the results obtained by genotypic and phenotypic methods was 97.7-100 %. The prevalence of the different fimbrial and toxin genes in E. coli strains from piglets with neonatal and postweaning diarrhoea were recorded. The verotoxin and the fimbrial F107 genes were found to be more frequent in postweaning E. coli strains than in neonatal E. coli strains. IntroductionEnterotoxigenic Escherichia coli (E. coli) (ETEC) is an important cause of diarrhoea in piglets. The diarrhoea occurs just after birth, in 1-7 day-old piglets, as neonatal diarrhoea. Postweaning diarrhoea occurs just after weaning in 22-49 days old piglets. Recognized virulence factors of the enterotoxigenic E. coli are the fimbrial adhesins K88, K99, 987P and F41 and the enterotoxins ST,, ST, and LT. Due to the lack of suitable methods a complete survey of virulence factors of E. coli strains pathogenic for piglets has not been carried out in Denmark before this study.The plasmid borne genes encoding ST,, STb and LT have been cloned and sequenced 50 OJENIYI, AHRENS and MEYLING (1981), the K99 fimbrial gene by ROOSENDAAL et al. (1984), the F41 fimbrial gene by FIDOCK et al. (1989) and the 987P fimbrial gene by DE GRAFF & KLAASEN (1987). The F107 fimbrial gene has been sequenced by IMBERECHTS et al. (1992). This information made it possible to synthesize oligonucleotides which, after labelling, may be used directly to identify fimbrial or toxin genes in a colony hybridization test, or used as primers for the amplification of a specific region of the toxin gene using the polymerase chain reaction (PCR) technique. These methods are readily applicable to large numbers of strains in contrast t o the classical methods such as agglutination tests (for fimbriae), infant mouse test (for ST, toxin), ligated swine intestine (for STb) and cell culture tests (for LT toxin), all of which are unsuitable for large scale studies.In the present study, specific DNA probes were constructed by the PCR technique and used in colony hybridization assays t o identify fimbrial and toxin genes of E. coli iso...

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