Screening of Lactococcal Adhesion Genes and Two Pneumococcal Genes as Genetic Determinants of Virulence in Lactococcus garvieae Strains

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Nine lactococcal adhesin and two pneumococcal virulence genes were characterized in twenty Lactococcus garvieae strains obtained from rainbow trout, and also one human isolate by PCR. Findings showed that all strains carried adhPsaA (522 bp), LPxTG-1 (947 bp), adhCI (490 bp), and purB (864 bp) while some of the strains had adhPav (1048 bp), LPxTG-2 (767 bp), LPxTG-3 (231 bp), adhCII (732 bp), adh (398 bp) and SP_0121 (966 bp). High nucleotide homologies (85-99%) of adhCI, adhCII, adh, adhPav, adhPsaA, LPxTG-1, LPxTG-3 involved in bacterial adhesion were determined between L. garvieae strains and reference Lg2. Genes containing polymorphisms among strains were not considered to be directly involved in bacterial pathogenesis. The amplification of LPxTG-3 only in fish isolates showed that it might be responsible for coding the host-specific virulence factor. However, undetermined amplicons demonstrated that LPxTG-4 could not be used as a host-specific gene marker. Pneumococcal purB and SP_0121 have been experimentally detected in L. garvieae genome for the first time. Consequently, both purB and SP_0121 can be used as a virulence marker for L. garvieae. Findings provided valuable knowledge about L. garvieae pathogenesis and, will contribute to identify the appropriate genomic targets to develop new therapeutics against the lactococcosis.