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Antimicrobial Agents and Chemotherapy, January 2008, p. 248-252, Vol. 52, No. 1
0066-4804/08/$08.00+0     doi:10.1128/AAC.00714-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Mosaic Tetracycline Resistance Genes and Their Flanking Regions in Bifidobacterium thermophilum and Lactobacillus johnsonii

Angela H. A. M. van Hoek,^1* Sigrid Mayrhofer,² Konrad J. Domig,² Ana B. Flórez,³ Mohammed S. Ammor,^3, Baltasar Mayo,³ and Henk J. M. Aarts¹

RIKILT-Institute of Food Safety, Wageningen UR, Bornsesteeg 45, NL-6708PD Wageningen, The Netherlands,¹ Department of Food Science and Technology, Division of Food Microbiology and Hygiene, BOKU—University of Natural Resources and Applied Life Sciences, Gregor Mendel Strasse 33, A-1180 Vienna, Austria,² Instituto de Productos Lácteos de Asturias, CSIC, Carretera de Infiesto s/n, 33300-Villaviciosa, Asturias, Spain³

Received 1 June 2007/ Returned for modification 3 August 2007/ Accepted 24 October 2007

For the first time, mosaic tetracycline resistance genes were identified in Lactobacillus johnsonii and in Bifidobacterium thermophilum strains. The L. johnsonii strain investigated contains a complex hybrid gene, tet(O/W/32/O/W/O), whereas the five bifidobacterial strains possess two different mosaic tet genes: i.e., tet(W/32/O) and tet(O/W). As reported by others, the crossover points of the mosaic tet gene segments were found at similar positions within the genes, suggesting a hot spot for recombination. Analysis of the sequences flanking these genes revealed that the upstream part corresponds to the 5' end of the mosaic open reading frame. In contrast, the downstream region was shown to be more variable. Surprisingly, in one of the B. thermophilum strains a third tet determinant was identified, coding for the efflux pump Tet(L).

Published ahead of print on 29 October 2007.

Present address: Laboratory of Microbiology and Biotechnology of Foods, Agricultural University of Athens, 75 Iera Odos, 11855 Athens, Greece.