Ž .
Aquaculture 185 2000 235–243 www.elsevier.nlrlocateraqua-online
Use of Carnobacterium sp. as a probiotic for ž
Atlantic salmon Salmo salar L. and rainbow trout ž
Oncorhynchus mykiss, Walbaum
P.A.W. Robertson
a
, C. O’Dowd
a
, C. Burrells
b
, P. Williams
b
, B. Austin
a,
a
Department of Biological Sciences, Heriot-Watt UniÕersity, Riccarton, Edinburgh, Scotland EH14 4AS, UK
b
EWOS Technology Centre, Unit 1, Kingsthorne Park, Houston Industrial Estate, LiÕingston, West Lothian, Scotland EH54 5DB, UK
Accepted 9 November 1999
Abstract
A strain of Carnobacterium sp., isolated from the intestine of Atlantic salmon, was evaluated for potential use as a probiotic for salmonids. In vitro studies demonstrated antagonism against
Aeromonas hydrophila, A. salmonicida, FlaÕobacterium psychrophilum, Photobacterium damse- lae subsp. piscicida, Streptococcus milleri, Vibrio anguillarum and V. ordalii but not towards
Debaryomyces hansenii, Janthinobacterium liÕidum, V. alginolyticus, V. harÕeyi or Yersinia ruckeri. Feeding salmonids with diets containing the probiotic revealed that the isolate remained
viable in the gastrointestinal tract. After reverting to feeding with control diets, the isolate was re-isolated from the intestine up to 4 and 10 days in fingerlings and fry, respectively. After feeding
with the probiotic for 14 days, challenge by cohabitation indicated effectiveness at reducing disease caused by A. salmonicida, V. ordalii and Y. ruckeri but not V. anguillarum. q 2000
Elsevier Science B.V. All rights reserved.
1. Introduction
As a negative aspect to the success of aquaculture, increased intensification has led to higher outbreaks of disease, encompassing an ever increasing range of pathogens
Ž .
Austin and Austin, 1999 . To combat these diseases, widespread use of broad-spectrum Ž
chemotherapeutants has led to drug resistance problems in aquaculture e.g., Brown, .
1989; Karunasagar et al., 1994 . In order to rectify this situation, greater emphasis has
Corresponding author. Tel.: q44-131-451-3452; fax: q44-131-451-3009. Ž
. E-mail address: b.austinhw.ac.uk B. Austin .
0044-8486r00r - see front matter q 2000 Elsevier Science B.V. All rights reserved. Ž
. PII: S 0 0 4 4 - 8 4 8 6 9 9 0 0 3 4 9 - X
been placed on improved husbandry through better nutrition, improved water quality and lower stocking densities, and the use of vaccines and non-specific immunostimulants,
Ž .
such as b-1,3 glucans Austin and Austin, 1999 . Recently, attention has focused on the use of probiotics, using methods developed for
human medicine and agriculture for which the mechanisms by which probiotics operate Ž
have been well defined e.g., Fuller, 1978, 1992; Fuller and Turvey, 1971; Parker, 1974; .
Roach and Tannock, 1980; Smoragiewicz et al., 1993 . Most probiotics are supplied as live supplements in food, which must have the ability to survive passage through the
Ž .
intestinal tract Fuller, 1992 . The benefit to the host may arise as a nutritional effect, whereby the bacteria are able to break down toxic or otherwise unnutritious components
Ž .
of the diet, which the host can then digest Smoragiewicz et al., 1993 . Alternatively, the probiotic may prevent potential pathogens from colonising the gut by production of
antimicrobial compounds, or by outcompeting them for nutrients or mucosal space Ž
. Smoragiewicz et al., 1993 .
Only a few studies have addressed the use of probiotics in aquaculture. In particular, Ž
improvements have been shown in the culture of larval Pacific oysters Douillet and .
Ž .
Langdon, 1994 and turbot
Gatesoupe, 1991 following use of bacterial isolates.
Widespread use of probiotics has occurred in the Ecuadorian shrimp industry, where encouraging results have been obtained with batch cultures of Vibrio alginolyticus when
applied to larval rearing tanks. Here, there was improvement in growth of Penaeus Ž
Õ annamei larvae, and a reduction in the incidence and severity of disease Garriques and
. Arevalo, 1995 . This led to a reduction in the use of antibiotics during larval rearing
Ž .
Garriques and Arevalo, 1995 . Subsequently, a probiotic isolate of V. alginolyticus was demonstrated to be effective in controlling infections in salmonids, as caused by
Ž .
Aeromonas salmonicida, V. anguillarum and V. ordalii Austin et al., 1995 . However, the use of V. alginolyticus as a probiotic is of concern insofar as the taxon is also
Ž associated with disease Alfaro et al., 1993; Austin et al., 1993; Sutton and Garrick,
. 1993; Lee et al., 1996; Balebona et al., 1998 .
From agriculture, it is apparent that the majority of probiotics comprise lactic acid Ž
bacteria notably Lactobacillus sp., Bifidobacterium sp. and Streptococcus sp. Smora- .
giewicz et al., 1993 . Lactic acid bacteria also form a major component of the normal Ž
. microflora in the gastrointestinal tract of healthy fish Ringo and Gatesoupe, 1998 .
Consequently, the potential to use lactic acid bacteria as probiotics in fish has been examined. For example, lactic acid bacteria have provided turbot with protection against
Ž .
disease caused by Vibrio sp. Gatesoupe, 1994; Olsson et al., 1998 . Recently, an isolate of Carnobacterium sp. has been shown to survive in the gut of salmonids, and produce
Ž .
inhibitory compounds in intestinal mucus Joborn et al., 1997 . In this study, the benefit
¨
of this Carnobacterium sp. for use as a probiotic for salmonids was examined.
2. Materials and methods
