First Report of Lactococcus petauri in the Pumpkinseed (Lepomis gibbosus) from Candia Lake (Northwestern Italy)

Abstract

Lactococcus petauri has emerged as a pathogen affecting farmed fish. In this case report, L. petauri was isolated from Lepomis gibbosus captured in Lake Candia, located in Piedmont, Northwestern Italy. Initially identified as L. garvieae using conventional methods like RAPID 32 ID STREP and MALDI-TOF, molecular analysis based on sequencing of the 16S-23S rRNA internal transcribed spacer region (ITS) confirmed it as L. petauri. The study also assessed the isolated strain’s pathogenicity by examining hemolysin and capsule cluster genes, revealing only hemolysin 2 amplicon; notably, the fish exhibited no lesions or pathological alterations. The L. petauri strain from this study displayed resistance to several antibiotics, being sensitive only to ampicillin, amoxicillin, florfenicol, and G-penicillin. This research provides new insights into host range of L. petauri and raises awareness of potential public health implications, particularly concerning zoonotic potential.

Key Contribution: L. petauri is reported for the first time in fish species in Italy; in particular, it is reported in wild pumpkinseed capture in Lake Candia located in Piedmont.