Vol 3 (1) 2011 - UBM :: Departamentul de Chimie-Biologie

H. El-Sayed M. Farag, Concentration of antibiotics residues in farmed tilapia and their relationship to resistant
Aeromonas strains
[43]. The variation in the number and types
of the Aeromonas isolates from that of other
studies may be attributed to the changes of
water temperature and the adverse
conditions during intensification [44], such
as bad handling, inadequate concentration of
feed and oxygen, salinity of the harvested
site, concentration of organic matter and the
sewage effluents of water [45, 5].
It was revealed that 100% of the
isolated strains in group I (n=140) and II
(n=64) were resistances for oxytetracycline,
meanwhile 35.71% (n=20) of the isolated
strains from the group III were resistances
for oxytetracycline. The resistant strains of
group III were identified as A. caviae and A.
sobria that represent with an incidence of 80
% (n=16) and 20 % (n=4) respectively
(table, 8, 9). The intermediates sensitive
strains were recorded in group III and
identifies as A. scubertii with an incidence of
100% (n=16) but the incidence of sensitive
strains for oxytetracycline disc were
recorded also in group III with an incidence
of 60% (n=12) and 40% (n=8) for A. caviae
and A. hydrophila respectively. The results
of groups I and II agreed with the results
recorded by Rhodes [46] and higher than
that of Son [47], Schmidt [43] and
Abraham[20]. The results of group III were
lower than that recorded by Schmidt [42],
Schmidt [43] and Abraham, [20]. These
differences may due to the maintenance of
the acquired resistance genes within the
bacterial population, once it enter to these
population, results in protection of the
bacterium from tetracycline produced by
other member of microflora or residues in
agriculture or domestic effluents [43]. Also
the misused of antibiotic such as of lower
efficacy, high or lower dose of antibiotic
[35, 36], the persistence and degradation of
the antibiotic in the sediment, in the deeper
layer, [48, 49] and an increase in the
building up of antibiotic [50] enhance the
production of bacterial resistance for
antibiotic.
4. Conclusions
Antibiotics residues are seemed to
quality defects in farmed tilapia that facing
the challenges of the fish exporting in Egypt.
Also, it is represent a potential health risks
for consumers from the point of the adverse
oxytetracycline residual effect and the
initiation of the bacterial resistance genes.
Application of good manufacture practices
and Hazards Analysis Critical Control
System (HACCP) in tilapia farms must be
done for improving the antibiotics residual
problem in fish muscles. Good management
program should be applied to overcome the
outbreak by Aeromonas species specially
during the summer season. Treated tilapia
must be held for the recommended
withdrawal time before they can be
marketed for ensuring their safety for human
consumption. Future investigations should
be done for evaluation the antibiotics
residual levels in the water used for farming.
5. References
1. FAO "Food and Agriculture
Organization" (2006). FAO Fisheries
Technical Paper NO. 500. p.134.
Rome: State of world
aquaculture.Fessehaye, Y. 2006.
Natural Mating in Nile Tilapia
(Oreochromis niloticus L.):
Implications for Reproductive Success,
inbreeding and cannibalism. PhD.
thesis, Wageningen University.
2. Chapman, F. A. (1992).Culture of
hybrid tilapia: A reference profile. A
series of the Department of Fisheries
and Aquatic Sciences, Circular 1051.
Institute of Food and Agricultural
Sciences. University of Florida
3. Holmes, P., Niccolls, L. M. and Sartory,
D. P. (1996). In Austin, B., Altwegg,
M., Gosling, P. J. and Joseph, S. (Eds).
The genus Aeromonas: The ecology of
mesophilic Aeromonas in the aquatic
environment, p.127-150. New York, N.
Y: John Wiley & Sons Publishers.
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