Lactic acid bacteria virulence assessment: in silico predictions vs G. mellonella in vivo assays

MARTINO, G; OSORIO, J; ESTEBAN, L; MAGNI, C; BLANCATO, VS

Rosario

Congreso; L Reunión Anual de SAIB; 2014

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Identification of virulence proteins in sequenced genomes is useful to estimate their pathogenic potential. Nevertheless, mechanisms underlying pathogenesis are rather complex. To check the performance of existing prediction systems on lactic acid bacteria, we analyzed the available genomes of representative strains found in fermented foods, including our own sequenced strains and compared bioinformatic findings with in vivo results using G. mellonella. Prediction systems mvirDB and MP3 indicated that all the studied strains would have a large number of virulence factors (VF), whereas Virulence Finder only reported VF in E. faecalis. On the other hand Pathogen Finder predicted E. faecalis and E. mundtii as human pathogens. Infection of G. mellonella with E. faecalis led to a high mortality rate, E. mundtii caused an intermediate mortality, whereas L. lactis and Lb. casei hardly appeared to be lethal. Furthermore, we determined the contribution of citrate cluster to E. faecalis pathogenesis. Infection of larvae with citrate lyase or oxaloacetate decarboxylase deficient strains caused none or low mortality, suggesting that WT induced mortality could be dependent on the presence of an active citrate metabolism. In conclusion, diversity of results thrown by the available prediction software makes the use of experimental in vivo systems a convenient tool to reinforce or discard such results.