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Aquaculture 183 2000 195–205 www.elsevier.nlrlocateraqua-online
Antibiotic resistance in bacteria isolated from Artemia nauplii and efficacy of formaldehyde to
control bacterial load
A.S. Sahul Hameed , G. Balasubramanian
Aquaculture DiÕision, Department of Zoology, C. Abdul Hakeem College, MelÕisharam - 632 509, Vellore Dist., Tamil Nadu, India
Accepted 31 July 1999
Abstract
A study was carried out to determine the antibiotic resistance in bacteria isolated from Artemia nauplii and the efficiency of formaldehyde to control the bacteria associated with Artemia nauplii.
The total aerobic heterotrophic bacteria of Artemia nauplii was determined on seawater nutrient agar and TCBS agar, and ranged from 3.8 = 10
3
to 8.1 = 10
3
and 9.4 = 10
2
to 4.3 = 10
3
colony Ž
. forming units CFU per nauplius on seawater nutrient agar and TCBS agar plates, respectively.
Among these bacteria, 336 isolates were tested for their resistance to five antibiotics. The minimum inhibiting concentrations of chloramphenicol, erythromycin, nitrofurazone, oxytetracy-
cline, tetracycline, formaldehyde and sodium hypochlorite for 336 isolates were recorded. The LC50 values of oxytetracycline, formaldehyde and sodium hypochlorite for Artemia nauplii were
determined as 540.5, 293.1 and 5.6 mgrl, respectively, after 24 h of exposure. The efficacy of formaldehyde was compared with that of antibiotics and formaldehyde was found to be very
effective in controlling the bacteria of Artemia nauplii. q 2000 Elsevier Science B.V. All rights reserved.
Keywords: Artemia; Nauplii; Antibiotic resistant bacteria; Antibiotics; Formaldehyde; Efficacy
1. Introduction
Artemia is widely recognized as the best natural, storable live feed available, and is used in marine finfish and crustacean hatcheries around the world because of its
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nutritional and operational advantages Sorgeloos et al., 1986 . Artemia nauplii are also
Corresponding author. 0044-8486r00r - see front matter q 2000 Elsevier Science B.V. All rights reserved.
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PII: S 0 0 4 4 - 8 4 8 6 9 9 0 0 2 9 3 - 8
considered a possible vector for the introduction of pathogens into the rearing systems. Artemia nauplii carry a large bacterial load that may be transferred from live preys into
the tanks of fish and shellfish larvae. Some bacteria have been reported to be the source of diseases and high mortalities in fish larvae, and live feeds are thought to be
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responsible Tatani et al., 1985; Muroga et al., 1987; Nicolas et al., 1989 . Therefore, Artemia nauplii are often treated in order to reduce the bacteria associated with them
prior to feeding them to the larvae. Previous studies often recommend rinsing the nauplii Ž
. in sterile fresh or seawater Austin and Allen, 1982; Rodriguez et al., 1991 , but some
Ž authors argue that rinsing has little effect on the bacteria Dehasque et al., 1991;
. Verdonck et al., 1991 . In this situation, antibiotics have been tried to disinfect the live
Ž feed before introducing into the rearing systems Hatai et al., 1981; Yamanoi and
. Sugiyama, 1987; Tanasomwang and Muroga, 1989, 1992; Gomezgil et al., 1994 . The
potential consequences of antibiotic use in the treatments are the development of antibiotic resistant micro-organisms, multiple antibiotic resistance, resistance transfer to
pathogenic bacteria, and reduced efficacy of antibiotic treatment for diseases caused by
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resistant pathogens Frappaolo and Guest, 1986 . The research on the development of antibiotic resistant bacteria has mainly focused
on cattle, poultry and swine. Studies on the development of antibiotic resistance in bacterial fish pathogens has also been reported from all areas of aquaculture, ranging
Ž from warm water to coldwater, marine to freshwater Rahim et al., 1984; Hjeltnes et al.,
1987; Tsoumas et al., 1989; McPhearson et al., 1991; Richards et al., 1991; Spanggaard .
et al., 1993 . The purpose of the present study is to determine the antibiotic resistance in bacteria isolated from Artemia nauplii, to find out the alternative for the antibiotics used
routinely in aquaculture systems, to compare the efficacy of formaldehyde to control the bacteria associated with Artemia nauplii and to determine the tolerance level of
Artemia nauplii to formaldehyde and its optimum exposure time to reduce the bacteria.
2. Materials and methods
