Mycobacterium chelonae associated with tumor-like skin and oral masses in farmed Russian sturgeons (Acipenser gueldenstaedtii)

Elisabetta Antuofermo,Monica Caffara,Udo Hetzel,Stefano Rocca,Giovanni P Burrai,Claudio Pedron,Sara Nuvoli,Marino Prearo,Ilaria Giorgi,Antonio Pais

doi:10.1186/1746-6148-10-18

Abstract

BackgroundNon-tuberculous mycobacteria responsible for piscine mycobacteriosis usually produce visceral granulomas in both freshwater and marine species. In this study, the first occurrence of Mycobacterium chelonae associated with tumor-like lesions in the Russian sturgeon (Acipenser gueldenstaedtii) is reported. Fifteen sturgeons from an Italian fish farm showing skin and oral cauliflower-like masses were investigated by histopathology, bacterial culture and molecular analyses.ResultsA total of 20 masses different in size located in the mouth and in pectoral and caudal fins (characterized by abundant calcium deposits and by mild to moderate granulomatous inflammation) were observed with a significant different degree of histological severity. All internal organs of the fish were negative for mycobacteria, Ziehl-Neelsen was positive in only one of the oral masses, whereas bacterial and PCR analyses detected the presence of M. chelonae for almost all the skin and oral masses. Based on these results, a calcinosis of dystrophic origin associated with a chronic granulomatous inflammation was considered as a primary diagnosis consequent to tissue injury in areas susceptible to trauma.ConclusionsWe hypothesized that the occurrence of M. chelonae in farmed sturgeons was only a secondary event related to its presence in a stressful rearing environment and subsequent to a dystrophic calcinosis occurred in previously damaged tissues.

Highlights

Non-tuberculous mycobacteria responsible for piscine mycobacteriosis usually produce visceral granulomas in both freshwater and marine species
Few papers described a group of Siberian sturgeons (Acipenser baeri) imported in Italy from France showing visceral granulomas [26], and caviar fishes from Iran exhibiting gill lesions, both caused by Mycobacterium marinum [27]
In all the sturgeons examined in this study, the lesions were different in size and larger masses were mostly observed in the oral cavity, most of which showing a severe histological pattern significantly correlated with their size and with an infiltrative activity

Summary

Introduction

Non-tuberculous mycobacteria responsible for piscine mycobacteriosis usually produce visceral granulomas in both freshwater and marine species. The Russian sturgeon, Acipenser gueldenstaedtii Brandt & Ratzeburg, 1833, is an ancient fish native to Black Sea, Sea of Azov and Caspian Sea entering all the main rivers that empty into them [1].This species has both anadromous and freshwater populations: at sea, it occurs in shallow coastal and estuarine zones, while in freshwaters it inhabits the deep parts of large rivers with moderate to swift current [2] It was introduced throughout Europe and, due to loss of habitat caused by the construction of dams and to overfishing to collect its eggs, it is. Few papers described a group of Siberian sturgeons (Acipenser baeri) imported in Italy from France showing visceral granulomas [26], and caviar fishes from Iran exhibiting gill lesions, both caused by Mycobacterium marinum [27]

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