Experimental mycobacteriosis in striped bass Morone saxatilis

Abstract

Striped bass Morone saxatilis were infected intraperitoneally with approximately 10 5 Mycobacterium marinum, M. shottsii sp. nov., or M. gordonae. Infected fish were maintained in a flow-through freshwater system at 18 to 21°C, and were examined histologically and bacteriologically at 2, 4, 6, 8, 17, 26, 36 and 45 wk post-infection (p.i.). M. marinum caused acute peritonitis, followed by extensive granuloma development in the mesenteries, spleen and anterior kidney. Granulomas in these tissues underwent a temporal progression of distinct morphological stages, culminating in well-circumscribed lesions surrounded by normal or healing tissue. Mycobacteria were cultured in high numbers from splenic tissue at all times p.i. Standard Ziehl-Neelsen staining, however, did not demonstrate acid-fast rods in most early inflammatory foci and granulomas. Large numbers of acid-fast rods were present in granulomas beginning at 8 wk p.i. Between 26 and 45 wk p.i., reactivation of disease was observed in some fish, with disintegration of granulomas, renewed inflammation, and elevated splenic bacterial densities approaching 10 9 colony-forming units g -1 . Infection with M. shottsii or M. gordonae did not produce severe pathology. Mild peritonitis was followed by granuloma formation in the mesenteries, but, with 1 exception, granulomas were not observed in the spleen or anterior kidney. M. shottsii and M. gordonae both established persistent infections in the spleen, but were present at densities at least 2 orders of magnitude less than M. marinum at all time points observed. Granulomas in the mesenteries of M. shottsii-and M. gordonaeinfected fish resolved over time, and no reactivation of disease was observed. KEY WORDS: Mycobacteriosis · Striped bass · Morone saxatilis · Mycobacterium marinum · Mycobacterium gordonae · Mycobacterium shottsii · Granuloma Resale or republication not permitted without written consent of the publisherDis Aquat Org 54: [105][106][107][108][109][110][111][112][113][114][115][116][117] 2003 respectively (Sakanari et al. 1983, Hedrick et al. 1987. Mycobacterium marinum was cultured from fish in the latter study, and has also been isolated from wild Pacific striped bass (Landsell et al. 1993). Recently, visceral and dermal lesions in striped bass from Chesapeake Bay and its tributaries were shown to be associated with mycobacterial infection (Vogelbein et al. 1999). An epizootiological study of striped bass from Virginia tributaries of Chesapeake Bay found up to 62.7% prevalence of mycobacteriosis, based on histological presence of characteristic granulomas. This suggests the disease has significant effects on wild stocks (Cardinal 2001).In addition to Mycobacterium marinum and several other Mycobacterium spp., 2 recently described species of mycobacteria, 'M. chesapeaki ' (Heckert et al. 2001) and M. shottsii (Rhodes et al. 2001(Rhodes et al. , 2003 in press), have been isolated from Chesapeake Bay striped bass. Mycobacteria were cultured from splenic tissue of approximately 76% of stripe...

Characterization of the acute inflammatory response in the hybrid tambacu (Piaractus mesopotamicus male × Colossoma macropomum female) (Osteichthyes)

“…Later, the inflammatory response was evaluated by ink injection (Ellis et al, 1976), complete Freund's adjuvant and Staphylococcus aureus (Finn and Nielsen, 1971), carrageenin (Timur et al, 1977), Escherichia coli lipopolysaccharide (LPS), complete Freund's adjuvant, turpentine and carrageenin (White et al, 1981), Vibrio alginolyticus (MacArthur et al, 1984), liquid paraffin (Suzuki, 1986), Edwardsiella ictaluri LPS (Saeed and Plumb, 1986), Pseudomonas alcaligenes and Aeromonas punctata (Siwicki and Studnicka, 1987), Aeromonas salmonicida (Reite and Evensen, 1994), LPS (Brunetti et al, 1994), Freund's adjuvant and squalene (Jenkins and Klesius, 1998), microcystin (Vajcová et al, 1998), Escherichia coli , peptidoglican (Kono and Sakai, 2001), beta-glucan of Saccharomyces cerevisiae and Salmonella typhimurium LPS (Paulsen et al, 2001) and Mycobacterium marinum (Gauthier et al, 2003). In these studies, the inflammation was characterized by showing macrophages, leucocytes, fibroblasts and fibroplasia.…”

Comparative analysis of mycobacterial infections in wild striped bass Morone saxatilis from Chesapeake Bay

“…In this comparative study, the histological method of observing granulomas in aseptically collected splenic tissue revealed fewer mycobacterial infections than did quantitative bacteriology or nested PCR. This finding, along with previous reports which have described difficulties detecting acid-fast bacilli in granulomatous fish tissues (Gomez et , Colorni et al 1998, Gauthier et al 2003, indicates that strict reliance upon histological approaches could result in false negatives. The possibility exists that splenic granulomas may be absent from early infections due to an insufficient hypersensitive response of the host.…”

“…On the other hand, reliance on granuloma detection as evidence for mycobacteriosis can also lead to false positive results since granulomas can be caused by microorganisms other than mycobacteria (Gomez et al 1993, Falkinham 2002. In this instance, however, there are numerous reports of typical granulomatous development due to mycobacteria in wild striped bass from the Chesapeake Bay (Heckert et al 2001, Rhodes et al 2001, Gauthier et al 2003.…”

“…Although histological methods are commonly employed for the detection of mycobacterial infection in fishes (Sakanari et al 1983, Bruno et al 1998, Cardinal 2001, Rhodes et al 2001, Gauthier et al 2003, concurrent use of culture-and molecular-based detection methods remain limited. In this comparative study, the histological method of observing granulomas in aseptically collected splenic tissue revealed fewer mycobacterial infections than did quantitative bacteriology or nested PCR.…”

“…Morone saxatilis include aquacultured fish off the Pacific coast (Hedrick et al 1987), experimentally infected fish (Wolf & Smith 1999, Gauthier et al 2003, and wild fish from the Pacific and Atlantic coasts, the latter specifically in the Chesapeake Bay (Landsdell et al 1993, Heckert et al 2001, Rhodes et al 2001, 2003, 2005. Mycobacteriosis in Chesapeake Bay striped bass is noteworthy, as these fish constitute one of the region's most important recreational and commercial fisheries.…”