International Journal of Aquaculture, 2016, Vol.6, No.3, 1
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9
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antibiotics and antibiotic resistant bacteria from aquatic system all around the world alarms its future impacts
(Karki et al., 2013). In addition to the development and spread of drug resistance, the use of antibiotics in the
ornamental fish industry and aquaculture can lead to the accretion of residual antibiotics in aquatic environments
(Cabello, 2006; Hoque, 2014), accumulation in the food chain (Chen et al., 2010) and detrimental effect on the
microbial biodiversity (Zhou et al., 2010).
Transfer of resistance genes, between pathogenic to non-pathogenic bacteria make the situationworseand act as a
pool of resistance genes from which genes can be further distributed and may ultimately end up in human
pathogens (Bogaard and Stobberingh, 2000). Plasmid-borne resistance genes have been transferred by conjugation
from the fish pathogen
Aeromonas salmonicida
to
Escherichia coli
, a bacterium of human origin, some strains of
which are pathogenic for humans (Romero et al., 2012).Reportsonthe prevalence of resistant bacteria from water,
sediments or wild animals are increasing (Schmidtet al., 2001; Giraud, 2004) and pose potential danger to human
(Rose et al., 2013).Multi drug resistance was noted in many
Aeromonas
strainsfrom ornamental fish and fresh
water fish farms, (Hatha et al., 2005; Sreedharan et al., 2012; Nifty and Hatha, 2012).
Kerala, the southernmost state in India is bestowed 44 rivers and extensive backwater systems which support good
fish fauna, both edible and ornamental. Many of the indigenous ornamental fishes are being identified for
potential use in ornamental fish industry and breeding technologies are being developed as pre-requisite to
commercial exploitation. This has led to a spurt in freshwater ornamental industry and trade in Kerala during the
last five years. However, many of the natural waters are subjected considerable organic pollution which might
provide right kind of environment for the emergence of drug resistant mutants. In this regard, we have analysed
the prevalence of antibiotic resistance among the gut associated bacteria from two potential indigenous freshwater
ornamental fishes such as
A. lineatus
and
E. maculatus
in order to get a snapshot of prevalence of drug resistant
mutants.
2 Materials and Methods
2.1 Description of the collection site and fishes selected for the study
Fresh water fishes namely
Etroplus maculatus
(Orange chromide) and
Apocheilus
lineatus
(Striped panchax)
(Figure 1 a; Figure 1 b) were collected from backwaters at Edavanakad, (10
o
15’20” N; 76
o
34’20” E) using scoop
net and brought alive to the laboratory. These backwaters are an extension of Cochin estuary which has undergone
considerable organic pollution from anthropogenic activities.
E. maculatus
and
A. lineatus
thrive in these polluted
waters and we identified them as potential candidates for the study of gut associated bacteria.
a b
Figure 1 Indigenous freshwater ornamental fishes analysed in this study
Note: a:
Etroplus maculatus
; b:
Aplocheilus lineatus
After taking the morphometric measurements such as total length (TL) and standard length (ST) the fishes were
dissected out aseptically using sterile surgical blade. The entire gut region was aseptically removed, weighed and
homogenized using sterile glass homogenizer, and serially diluted up to 10
-6
using 10% phosphate buffer solution
of pH 7.2 Aliquots of 0.2 ml samples from each dilution were spread plated in duplicate on nutrient agar (Hi
