International Journal of Aquaculture, 2017, Vol.7, No.23, 143-158
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survived after 24 h exposure to different concentrations of bile juice. With gradual decrease in the concentration
of bile, an increase in the number of viable colonies was observed. Table 5 depicts the result of bile tolerance.
Table 4 Inhibition area (mm) produced by the selected gut bacteria in cross streaking method against the tested fish pathogens
Strains
AH
AS
AB
AV
P
BM
PP
PF
Bacterial strains
Proximal Intestine
ONF4L
6
-
5
-
-
-
-
-
ONF1X
-
-
-
-
3
-
-
6
ONF1P
-
5
-
-
7
8
5
7
ONF1T
-
2
-
-
4
4
4
5
Distal Intestine
ONH1Ph
-
2
-
-
-
-
4
-
ONH1A
-
-
-
-
4
-
-
-
ONH2A
-
-
4
3
2
3
-
-
ONH2Ph
-
-
-
-
-
-
-
2
ONH1C
-
-
3
-
3
1
-
4
ONH2C
-
-
-
-
-
-
-
3
Yeast strains
Proximal Intestine
ONF7.1C
2
-
-
-
-
3
-
-
ONF8.1A
-
-
-
-
-
-
3
-
ONF14.1C
-
2
-
-
-
-
2
-
ONF21.1B
-
-
-
-
-
2
-
-
Distal Intestine
ONH15.1B
-
-
-
-
-
2
-
-
Note: AH=
Aeromonas hydrophila
; AS=
Aeromonas salmonicida
; AB=
Aeromonas sobria
; AV=
Aeromonas veronii
; P=
Pseudomonas
sp.; BM=
Bacillus mycoides
; PP=
Pseudomonas putida
; PF=
Pseudomonas fluorescens
Table 5 Tolerance of the selected isolates at different concentrations of fish bile juice for 1.5 h at 30°C, viable count was determined
on TSA plates inoculated with bile exposed bacterial suspension. Data are mean ±standard error (n = 3)
Bile (%)
Log CFU mL
-1
ONF1P
ONF7.1C
0
5.72±0.006
4.63±0.007
1
5.54±0.006
4.27±0.009
2
5.50±0.004
4.16±0.007
3
5.48±0.005
4.02±0.009
4
5.37±0.004
3.90±0.007
5
5.26±0.006
3.81±0.005
6
5.26±0.004
3.48±0.006
7
5.20±0.005
3.18±0.003
8
5.14±0.005
2.67±0.006
9
5.14±0.008
2.46±0.003
10
5.03±0.001
2.06±0.004
11
5.01±0.002
-
12
4.80±0.003
-
13
4.45±0.004
-
Study of growth in mucus revealed that strains ONF1P and ONF7.1C grew well in mucus of
O. niloticus
(Figure
1). As evident from the optical density, maximum growth was observed after 48h of incubation. Growth
eventually started to decline after 72 h of incubation.
