Phenotypic and genetic characterization of Lactococcus garvieae isolated in Spain from lactococcosis outbreaks and comparison with isolates of other countries and sources

The phenotypic and genetic analysis results for 84 isolates of Lactococcus garvieae (including 62 strains from trout with lactococcosis from four diff erent countries, 7 strains from cows and water buffalos with subclinical ma stitis, 3 from water, and 10 from human clinical samples) are presented. Th ere was great phenotypic heterogeneity (13 different biotypes) based on the acidification of saccharose, tagatose, mannitol, and cyclodextrin and the presence of the enzymes pyroglutamic acid arylamidase and N-acetyl-beta-glu cosaminidase. L. garvieae also exhibited high genetic diversity by pulsed-f ield gel electrophoresis (PFGE), with 19 different pulsotypes among the iso lates of L. garvieae studied. Only epidemiologically related strains, like the Spanish and Italian fish isolates and the cow and water buffalo isolate s, displayed a close genetic relationship by PFGE, while the strains isolat ed from sporadic clinical cases, like the human isolates, were genetically unrelated. Overall, a general correlation between phenotypic and genetic da ta was observed, Epidemiological analysis of biotype and PFGE results indic ated that the trout lactococcosis outbreaks in Spain and Portugal and those in France and Italy were produced by genetically unrelated clones. In Spai n, two different clones were detected; the outbreaks diagnosed from 1995 on ward were produced by a clone (biotype 2, pulsotype Al) which, although gen etically related, was different from the one that was responsible for the o utbreaks studied between 1991 and 1994 (biotype 1, pulsotype B). The Portug uese isolate had a biochemical profile identical to that of the Spanish str ain isolated from 1995 onward and is also genetically closely related to th is strain (pulsotype A2). There was a close relationship between the two pu lsotypes (E and F) found in the Italian isolates. The French isolate (bioty pe 3, pulsotype D) was not genetically related to any other L. garvieae fis h isolate. These results suggest the existence of diverse infection sources for the different lactococcosis outbreaks.