Differences in virulence genes frequency among VTEC isolates from cattle, foods and environment.

LUCCHESI, PAULA M.A.; KRÜGER ALEJANDRA; PADOLA, NORA L.; ETCHEVERRÍA, ANALÍA I.; SANZ, MARCELO, E; FERNÁNDEZ, DANIEL; ALONSO, MÓNICA Z.; POLIFRONI, ROSANA; ARROYO, GUILLERMO H.; PARMA, ALBERTO E.

Amsterdam

Simposio; 8th International Symposium on Shiga Toxin (Verocytotoxin) producing Escherichia coli infections.; 2012

Introduction & Objectives: The aims of this study w ere to asses the prevalent virulence genes and their combinations among a collection of VTEC isolates obtained from bovine cattle, foods and the environment, and to compare the results among isolates from different origins: calves, grow n calves, adult cattle, foods and environment. Material & Methods: The isolates had been obtained from bovine cattle (451 isolates comprising: 95 from calves, 75 from grow n calves, and 281 from adult cattle w hich include dairy cow s, feedlot cattle and cattle at slaughter), meat (74 isolates) and the environment of dairy farms (20 isolates). They w ere characterized by a multiplex PCR that detects vt1, vt2, eae, ehxA and saa. Results: The vt2 gene w as present in average in 85.1 % of the isolates, follow ed by ehxA and saa genes (63.7 and 35.6 %, respectively). When the isolates w ere grouped according to the origin, some marked differences in gene frequency w ere detected. The eae gene w as detected in a high frequency in isolates from calves and the environment (74.7 and 65 %, respectively), w hereas the frequency w as less than 15 % in isolates from the other origins. The saa gene frequency show ed an inverse trend, but never reached levels higher than 50 %. The percentage of vt1?positive isolates w as ≥ 40 among those from calves and the environment, and low er in the isolates from the other origins. The predominant virulence profiles, w hich comprised 78% of the isolates, w ere vt2, vt2/ehxA/saa, vt1/vt2/ehxA/saa, and vt2/eae/ehxA, arranged in decreasing order. Among calves, the profiles vt1/eae/ehxA and vt2/eae/ehxA w ere the most frequent, follow ed by vt2, and these three profiles also predominated among environmental VTEC isolates. The profile vt2 w as the most frequent among grow n calves, adult cattle and food isolates, follow ed by vt2/ehxA/saa and vt1/vt2/ehxA/saa. Conclusions: The frequencies of the genes detected in this study kept close similarity among isolates from meat, adult cattle and grow n calves, differing from those from calves and the environment, w hich show ed a higher frequency of eae and vt1 than the others. The relationship betw een VTEC isolates from meat and aduIt cattle is not unexpected as meat can become contaminated w ith VTEC during slaughter and the samples from adult cattle included cattle at slaughter and feedlot cattle that w ere near finishing. Besides it, on the other hand it can be speculated that young animals (calves) make an important contribution to the contamination of the environment in dairy farms.