Influence of Moraxella sp. colonization on the kidney proteome of farmed gilthead sea breams (Sparus aurata, L.)

A total of 960 gilthead sea breams (Sparus aurata, L.), collected along 17 months from four offshore sea cage plants and two natural lagoons in Sardinia, were subjected to routine microbiological examination of internal organs throughout the production cycle. Thirteen subjects (1.35%) were found positive for Moraxella sp. in the kidney (7), brain (3), eye (1), spleen (1), and perivisceral fat (1). In order to investigate the influence of Moraxella sp. colonization, positive and negative kidney samples were subjected to a differential proteomics study by means of 2-D PAGE and mass spectrometry. Interestingly, Moraxella sp. infected kidneys displayed a concerted upregulation of several mitochondrial enzymes compared to negative tissues, reinforcing previous observations following lipopolysaccharide (LPS) challenge in fish.Presence of Moraxella sp. in farmed sea bream kidney is able to induce proteome alterations similar to those described following LPS challenge in other fish species. This study revealed that Moraxella sp. might be causing metabolic alterations in fish, and provided indications on proteins that could be investigated as markers of infection by Gram-negative bacteria within farming plants.The occurrence of a bacterial infection outbreak in an aquaculture plant can produce important detrimental effects, including decreased growth rate, impaired fish wellness, and poor productivity, and may rapidly lead to widespread fish losses if left uncontrolled [1]. Therefore, the tanks or cages need to be constantly monitored for absence of potentially deleterious bacteria. However, several bacterial species isolated from fish tissues, including Moraxella [2], do not currently receive attention as potentially harmful for the fish farming economy, although infections by Moraxella sp. are becoming increasingly common in Mediterranean aquaculture plants. There have been increasing reports from farmers concerning slow fish growth, losses in production efficiency, and po