Isolation of Mycobacteria from Frozen Fish Destined for Human Consumption

Abstract

Mycobacteria were isolated from defrost water and tissue of sole (Solea solea), hake (Merluccius merluccius), cod (Gadus morhua), ling (Genypterus blacodes), and monkfish (Lophius piscatorius) on Löwenstein-Jensen medium after incubation at different temperatures. Samples of frozen fish were obtained under sterile conditions inside a refrigeration chamber (؊18 to ؊22°C) in a wholesale market from which these products are distributed to shops for retail sale and human consumption.Nontuberculous mycobacteria (NTM) are transmitted to humans from the environment, including through ingestion of food. They have been isolated from beef, pork, lamb (19), milk and other dairy products (8, 16, 18, 21, 22, 23), water (1, 7, 10, 20), vegetables (broccoli, spinach, and lettuce) (24), fruit (cherries, pomegranates, and apples) (24), preserves and brine (19), herbs (basil and parsley) (24), oysters (18), and fish such as Pacific salmon (2) and Channa striatus (4). The objectives of all of these studies were to show the presence of mycobacteria in food samples and analyze these possible sources of human infection or colonization.Mycobacteria can survive under environmental conditions that are intolerable for most other bacterial genera, including temperatures below 0°C. Strains are known that have remained viable in nutrient broth at Ϫ70°C for years (11,13). This may be due to the specific properties of their cell walls, such as high lipid content and therefore hydrophobicity, which renders them resistant to changes in environmental conditions (14).Due to the association between mycobacteria and a variety of different aqueous environments (3, 5, 9, 15), it seems reasonable to believe that these organisms may occur in frozen foods, including fish, which are widely consumed by humans. When fish is frozen in order to preserve quality, microorganisms are inevitably included.Our objective was to find out whether frozen fish contains NTM from which humans could be colonized.Samples of frozen fish were obtained under sterile conditions inside a refrigeration chamber (temperature between Ϫ18 and Ϫ22°C) in a wholesale market from which these products are distributed to shops for retail sale and human consumption. The fish and their origins were as follows: Solea solea from Denmark, Merluccius merluccius from Spain, Gadus morhua from Iceland, Genypterus blacodes from Argentina, and Lophius piscatorius from Ireland. Ten samples of each of the five species of fish, a total of 50 samples, were analyzed. When the samples were obtained, the fish product was individually vacuum packed in plastic bags in the case of G. morhua, G. blacodes, and L. piscatorius whereas the samples of S. solea were also individually wrapped in plastic but not vacuum packed. The pieces of M. merluccius were packed in a single plastic food grade bag.All of the fish had been gutted and frozen, with the head and caudal fin removed, and cut longitudinally into boneless fillets in the case of S. solea, boneless steaks in the case of G. morhua, and transverse slices in t...

Nontuberculous Mycobacteria in Freshwater Fish and Fish Products Intended for Human Consumption

“…Viable mycobacteria were predominantly isolated from frozen fish samples. As has been previously demonstrated, freezing did not devitalize mycobacteria during storage of samples including frozen fish (Livanainen et al, 1995;Mediel et al, 2000).…”

“…This could influence the presence of mycobacteria in these samples, because water, including drinking water, is considered to be an important reservoir of NTM (Falkinham, 1996;Primm et al, 2004). In the study of Mediel et al (2000), various NTM species (M. fortuitum, M. gordonae, M. chelonae, M. nonchromogenicum, M. peregrinum, and M. terrae complex members) were isolated from the tissues and defrosted water of frozen marine fish.…”

Isolation and characterization of mycobacteria from striped bass Morone saxatilis from the Chesapeake Bay

“…However, assignment of these environmental isolates to existing species is tenuous and requires additional genotypic studies. Mediel et al (2000) also reported the inability to speciate mycobacteria isolated from fish on the basis of biochemical or restriction fragment length polymorphism analysis pattterns. With the development of new molecular tools that have enhanced discriminatory power, there has been an explosion of new species in the Mycobacterium taxon (Tortoli 2003).…”

Comparative chemical composition of different muscle zones in angler (Lophius piscatorius)

“…Preliminary research into quality changes in this species during storage or technological processing has assessed microbial presence (Mediel et al, 2000), volatile amine formation (RuizCapillas and Horner, 1999), nucleotide degradation (Mendes et al, 2001) and employment of advanced chilling strategies ( BarrosVelá zquez et al, 2008;García-Soto et al, 2011). Previous research related to chemical composition and nutritional value of angler is scarce and has focused on proximate and amino acid composition (Jhaveri et al, 1984), fatty acid composition (Sirot et al, 2008), and assessment of a-tocopherol and essential minerals (Jhaveri et al, 1984;Carvalho et al, 2005).…”