الفهرس 
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Abstract
Aeromonas spp. are considered the main occasion of diseases including ulcerative syndrome leading to high mortalities also can be a problem for human consumers.
The samples were collected for my study from tilapia fish (O. niloticus) had signs of septicemia and suffered from MAS (n=56), environmental water (n=56), sediment of fish farms soil (n=56) and stool samples of patients suffering from gastroenteritis (n=56), where:
1. Aeromonas spp. were isolated from tilapia fish suffering from MAS with a percentage of 55.3 % (31/56).
2. Aeromonas spp. were isolated from stool samples of patients suffering from gastroenteritis either diarrhoeal stool or apparently had abdominal pain at a percentage of 51.3 % (19/37) and 42.1 % (8/19) respectively with a total percentage of 48.2 % (27/56) and were isolated from environmental samples water and soil at a percentage of 21.4 % (12/56) and 30.3 % (17/56) respectively.
3. A total of 87 positive Aeromonas spp. isolates recovered from all samples. The prevalence of the positive isolates distributed based on their source was 55.3% (31/56) from tilapia fish, 21.4% (12/56) from water, 30.3% (17/56) from soil, and 48.2% (27/56) from human stool samples.
4. The sensitivity tests for the isolated Aeromonas strains revealed that, they were highly sensitive to ciprofloxacin (85.2%) followed by moxifloxacin and norfloxacin (82.4% and 80.6% respectively). Meanwhile, they were less sensitive to gentamycin, streptomycin and cefotaxime. Moreover, they were highly resistant to ampicillin (97.8%) followed by penicillin-G and amoxicillin (94.6% and 89.8% respectively).
5. PCR identification using 16S rRNA gene confirmed identification of a total of 18 positive Aeromonas hydrophila strains recovered from phenotypically identified 28 Aeromonas spp. positive samples obtained from total 87 Aeromonas spp. positive samples. The prevalence of the positive isolates distributed based on their source was 85.7% (6/7) from diseased fish, 42.3% (3/7) from water, 42.3% (3/7) from soil, and 85.7% (6/7) from stool swab of diarrheic patients.
6. In typing those strains the total number of ERIC-PCR bands was 14 in fish, 12 in water, 13 in soil, and 14 in stool swab isolates. No identical band pattern was observed among the 18 isolates even single band not significant among the isolates of the same sample types may be due to the genus. This indicates the higher genetic variety among A. hydrophila isolates involved in this study. The highest (largest size) band (2.73 kb) was noticed in 2 stool swab isolates (lanes 6 and 11), while the lowest (smallest size) band (0.27 kb) was found in fish (lane 4), water (lane 2) and soil (lane 1) isolates.
7. Based on the results of ERIC fingerprinting analysis, 18 A. hydrophila isolates were categorized into 6 clusters (C1 to C6) ERIC types. Isolates no. (3,4) isolated from fish, 2 isolated from water and (1) isolated from soil clustered in group (C1). Isolates no. (5) isolated from stool, (8) isolated from water and (7) isolated from soil clustered in group (C6). There was a high similarity among C1 and C6 from 60 % to 75% of identity. But there is no identity between isolate no. (17) isolated from human stool and C5 which has isolates no. (9 and 10) isolated from fish. High similarity was found between C3 and C4 reach to 67% of identity. C3 and C4 have isolates isolated from fish (15 in C3 and 16 in C4) and human stool (18 in C3 and 6 in C4) and human stool.
8. The UPGMA cluster analysis on the basis of RAPD profile of Aeromonas hydrophila depicted all the strains having the several clusters and it suggests that their profiles are species specific. Visible RAPD fingerprinting profiles revealed the substantial wide genetic diversity among the strains tested. Strains 12, 13, 10, 11, 2 and 9 formed a minor cluster (C3) with similarity average 43%, their sources were stool, soil, fish, stool, water and fish respectively, while 5 and 15 strains, their sources were stool and fish respectively, formed a separate minor cluster with similarity 25% against the cluster (C1) which consisted of 4 and 16 strain from fish source and 17 strain from stool source with similarity 57%. This may be insufficient to indicates the genetic relationship among the strains within the clusters. It is clear that one can easily understand the percentage of genetic similarities between the strains. There was a high similarity among C4 (10,11 and 2 strains) and C5 (3 and 6 strains from fish and stool sources respectively) 71% of identity. But there is no identity between isolate no. (15) isolated from fish and isolate no. (2) isolated from water.
However, not infer the possibility of water borne infection of Aeromonas hydrophila from water and need in my opinion to correlate these results of clinical (fish and human) and environmental water and soil (ecotype) and virulence gene, in a wide scale.