MLVA-16 typing of 295 marine mammal Brucella isolates from different animal and geographic origins identifies 7 major groups within Brucella ceti and Brucella pinnipedialis
1 INRA, UR1282, Infectiologie Animale et Santé Publique, IASP, Nouzilly, F-37380, France
2 Université Paris-Sud 11, CNRS, UMR8621, Institut de Génétique et Microbiologie, Orsay 91405, France
3 Division of Analytical Microbiology, Centre d'Etudes du Bouchet, Vert le Petit, F-91710, France
4 SAC Veterinary Services, Inverness, IV2 4JZ, UK
5 Norwegian School of Veterinary Science, Department of Food Safety and Infection Biology, Section of Arctic Veterinary Medicine, Stakkevollveien 23, N-9010 Tromsø, Norway
6 Norwegian National Veterinary Institute, Ullevålsveien 68, N-0106 Oslo, Norway
7 Bundeswehr Institute of Microbiology, Department of Bacteriology, Neuherbergstr. 11, D-80937 Munich, Germany
8 RWTH Aachen University, Department of Internal Medicine III, Pauwelsstraße 30, D-52074 Aachen, Germany
9 Institut Universitaire de Technologie, Université François Rabelais, 29 rue du pont-volant, 37082 Tours cedex 2, France
10 Friedrich Loeffler Institute, Institute of Bacterial Infections and Zoonoses, Naumburger Str. 96a, D-07743 Jena, Germany
11 Veterinary and Agrochemical Research Centre (VAR), Groeselenberg 99, B-1180 Brussels, Belgium
12 DGA/MRIS-Mission pour la Recherche et l'Innovation Scientifique, 7-9, rue des Mathurins, Bagneux F-92221, France
BMC Microbiology 2009, 9:145 doi:10.1186/1471-2180-9-145Published: 20 July 2009
Since 1994, Brucella strains have been isolated from a wide range of marine mammals. They are currently recognized as two new Brucella species, B. pinnipedialis for the pinniped isolates and B. ceti for the cetacean isolates in agreement with host preference and specific phenotypic and molecular markers. In order to investigate the genetic relationships within the marine mammal Brucella isolates and with reference to terrestrial mammal Brucella isolates, we applied in this study the Multiple Loci VNTR (Variable Number of Tandem Repeats) Analysis (MLVA) approach. A previously published assay comprising 16 loci (MLVA-16) that has been shown to be highly relevant and efficient for typing and clustering Brucella strains from animal and human origin was used.
294 marine mammal Brucella strains collected in European waters from 173 animals and a human isolate from New Zealand presumably from marine origin were investigated by MLVA-16. Marine mammal Brucella isolates were shown to be different from the recognized terrestrial mammal Brucella species and biovars and corresponded to 3 major related groups, one specific of the B. ceti strains, one of the B. pinnipedialis strains and the last composed of the human isolate. In the B. ceti group, 3 subclusters were identified, distinguishing a cluster of dolphin, minke whale and porpoise isolates and two clusters mostly composed of dolphin isolates. These results were in accordance with published analyses using other phenotypic or molecular approaches, or different panels of VNTR loci. The B. pinnipedialis group could be similarly subdivided in 3 subclusters, one composed exclusively of isolates from hooded seals (Cystophora cristata) and the two others comprising other seal species isolates.
The clustering analysis of a large collection of marine mammal Brucella isolates from European waters significantly strengthens the current view of the population structure of these two species, and their relative position with respect to the rest of the Brucella genus. MLVA-16 is confirmed as being a rapid, highly discriminatory and reproducible method to classify Brucella strains including the marine mammal isolates. The Brucella2009 MLVA-16 genotyping database available at http://mlva.u-psud.fr/ webcite is providing a detailed coverage of all 9 currently recognized Brucella species.