Skin lesion-associated pathogens from Octopus vulgaris: first detection of Photobacterium swingsii, Lactococcus garvieae and betanodavirus.

The common octopus Octopus vulgaris Cuvier, 1798 is extremely important in fisheries and is a useful protein source in most Mediterranean countries. Here we investigated pathogens associated with skin lesions in 9 naturally deceased specimens that included both cultured and wild common octopus. Within 30 min after death, each octopus was stored at 4°C and microbiologically examined within 24 h. Bacterial colonies, cultured from swabs taken from the lesions, were examined using taxonomical and biochemical analyses. Vibrio alginolyticus and V. parahaemolyticus were only isolated from cultured animals. A conventional PCR targeting the 16S ribosomal RNA (rRNA) gene and sequencing were performed on 2 bacterial isolates that remained unidentified after taxonomical and biochemical analysis. The sequence results indicated that the bacteria had a 99% identity with Lactococcus garvieae and Photobacterium swingsii. L. garvieae was confirmed using a specific PCR based on the 16S-23S rRNA internal transcribed spacer region, while P. swingsii was confirmed by phylogenetic analyses. Although all animals examined were found to be infected by the protozoan species Aggregata octopiana localised in the intestines, it was also present in skin lesions of 2 of the animals. Betanodavirus was detected in both cultured and wild individuals by cell culture, PCR and electron microscopy. These findings are the first report of L. garvieae and betanodavirus from skin lesions of common octopus and the first identification of P. swingsii both in octopus skin lesions and in marine invertebrates in Italy.