الفهرس 
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Abstract
6. SUMMARY
Escherichia coli and Salmonella infections constitute a major economic problem and a serious public health hazard. This work aimed to study a number of characters as markers for E. coli and Salmonella microorganisms.
The characters discussed in the current study were, the prevalence rate of both E. coli and Salmonella isolates recovered from apparently healthy chickens, slaughtered chickens and eggs, as well as serotyping, detection of some virulence attributes, pathogenicity and antimicrobial sensitivity patterns of the isolates.
In the present study, the bacteriological examination of 427 samples collected from chickens revealed the isolation of 136 (47.7%) and 69 (48.5) E. coli isolates from apparently healthy and slaughtered chickens, respectively.
Regarding the site of isolation, the E. coli isolates recovered from nasal swabs, cloacal swabs, intestine, liver, heart blood and gall bladder represented 29.3, 37.1, 11.7, 8.3, 9.3 and 4.4% of the total number of isolates.
On the other hand, the examination of the same samples resulted in isolation of 20 (7.0%) and 12 (8.5%) Salmonella isolates from apparently healthy and slaughtered chickens respectively. Concerning the isolation site, the recovery rates of Salmonella isolates were 25.0, 37.5, 15.6, 12.5, 6.3 and 3.1% of the total number of isolates from nasal swabs, cloacal swabs, intestine, liver, heart blood and gall bladder, respectively.
The examination of 102 table eggs for presence of salmonella revealed the isolation of 6 (5.9%) Salmonella isolates. The total percent for Salmonella isolates was 7.2%.
Out of 136 E. coli isolates recovered from apparently healthy chickens 90 isolates were serotyped into O78 (34 isolates), O119 (12 isolates), O126 (9), O26 (7), O87 (7), O125 (4), O128 (7), O146 (5) and O27 (5 isolates). In addition to 46 untypable strains.
From 69 E. coli isolates recovered from slaughtered chicken the differentiated serovars were O78 (19 isolates), O1, O2, O8 and O27 (1 isolate each), O119, O126 and O125 (5 isolates each), O26, O87, O128 and O146 (2 isolates each). The remaining 23 strains were untypable.
Serotyping of 38 Salmonella isolates, revealed the differentiation of 5 serovars which were S. enterica serovars typhimurium (15 isolates), gallinarum (8 isolates), enteritidis (7 isolates), infantis (5 isolates) and anatum (3 isolates).
Concerning the virulence factors of E. coli strains, first the congo red binding activity was detected in 35.3 and 60.9% of
E. coli isolates from apparently healthy and slaughtered chickens, respectively.
Examination of E. coli isolates for haemagglutination and mannose resistance haemagglutination activity revealed that 12, 56, 20 and 16 isolates were HA+ to cattle, chicken, sheep and horse erythrocytes, respectively. Meanwhile, 4, 40, 12 and 8 isolates were MRHA to cattle, chicken, sheep and horse erythrocytes. Moreover, 69 E. coli isolates from slaughtered chickens revealed 28, 66, 37 and 28 HA+ isolates to cattle, chicken, sheep and horse erythrocytes, while, 12, 48, 24 and 20 isolates were MRHA to cattle, chicken, sheep and horse erythrocytes, respectively. All E. coli isolates were HA– to human erythrocytes.
Out of 21 different E. coli serovars, the enterotoxigenic strains were 3 (3.33%) and 7 (58.3%) of the E. coli isolates recovered from apparently healthy and slaughtered chickens, respectively.
Results of congo red binding test of Samonella isolates revealed that 55.0, 58.3 and 33.3% of Salmonella isolates recovered from apparently healthy chickens, slaughtered chickens and eggs, respectively.
Testing of Salmonella isolates for HA and MRHA activity resulted in 23, 21 and 7 Salmonella strains were HA+ and 18, 11 and 6 isolates were MRHA to chicken, sheep and horse erythrocytes. The enterotoxigenic Salmonella strains represented 45.0, 66.7 and 33.3% of the total isolates recovered from apparently healthy chickens, slaughtered chickens and table eggs respectively.
Pathogenicity of the Salmonella serovars was examined in chickens. All serovars were pathogenic with various percentages according to types and routes of infection. In this work, the clinical signs, post mortem examination and mortality rates were discussed.
The antimicrobial susceptibility of E. coli and Salmonella serovars were investigated.
The sensitivity percentages of E. coli isolates were 72.9, 62.5, 60.4 and 52.1% to amikacin, flumiquin, norfloxacin and colistin, respectively.
While, the tested strains were resistant to trimethoprim sulphamethoxazole (79.2%), amoxicillin (65.4%) and chloramphenicol (50.0%).
On the other hand, the sensitivity percentages of
S. typhimurium were 80.0, 73.3 and 53.3 to gentamicin, norfloxacin and amikacin.
The examined 8 strains of S. gallinarum pullorum were sensitive to amikacin (87.5%), chloramphenicol (75.0%) and gentamicin (75.0%).
S. enteritidis examination revealed that 100.0% of the isolates were sensitive to amikacin and gentamicin.
The isolates were sensitive to norfloxacin in percentage of 57.1% and were resistant to amoxicillin and trimethoprim-sulpha methoxazol. Meanwhile, 100.0, 80.0, 80.0, and 60.0% of the
S. infantis isolates were sensitive to amikacin, norfloxacin, gentamicin and chloramphenicol, respectively. While, 80.0, 60.0 and 60.0% of S. infantis isolates were resistant to amoxicillin, norfloxacin and colistin.
The S. anatum isolates were sensitive to : Norfloxacin (100%), amikacin (100%), gentamicin (100%), chloramphenicol and colistin (66.7%) each and were resistant to trimethoprim-sulphamethoxazol (66.7%).