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Abstract
In the present study, 536rectal content samples were collected from 364 cows and 172 buffaloes,which examined for presence of aeromonasspp. The result of aeromonasisolation revealed that 88 (24.17%) cows and 28 (16.27%) buffaloes were positive forAeromonas species . The prevalence rate of different aeromonas species in diarrhoeic bovine farmanimalsshowed that out of 364 examined cows, 52 (14.28%) animals harboredA. Hydrophila, 22 (6.04%) A. caviae and 14 (3.84%) A. veroniibiovarsobria.Out of 172 tested buffaloes, 16 (9.30%) animals carriedA. hydrophila, 8 (4.65%) A. veroniibiovarsobria and 4 (2.32%) A. caviae.Seasonal variation of aeromonas spp. isolated from diarrhoeic bovine farm animals demonstrated that the highest isolation rate of aeromonasspp.from examined diarrhoeic bovine farm animals were recordedin summer (48.28%) followed by spring (29.31%), autumn (15.52%) andwinter (6.89%). Invitro study of the virulence factors of the recovered aeromonas spp. revealed that,all motile aeromonas isolates gave Congo red positive with different degrees in colour,with an incidence of 54 (46.55%), while in case of crystal violet binding ability, 76 isolates gave CV + with an incidence of (65.52%). Studying the ability of recovered Aeromonas spp. for growth at 43{u00B0}C. revealed thatmost aeromonas isolates of buffaloes (92,86%) grow at 43{u00B0}C followed by isolates of cows (75%). The 116 different Aeromonas isolates recovered from examined samples were tested for ability to produce enterotoxin, the result revealed that there are 86 aeromonas strains (74.14%) were positive for production of enterotoxin. Thestudy of the cytotoxicity of the selected 116 aeromonasisolates on vero cells showed that, 64 isolates with an incidence of (55.17%) were able to produce cytolytic enterotoxin. The in vitro sensitivity of Aeromonasisolates were done against 13 different chemotherapeutic agents. The obtained results revealed that most strains of A.hydrophilawere sensitive to chloramphenicol (94.12%), ciprofloxacin and norfloxcin (91.18% each). While it was notice that most strains of A. caviae were sensitive to chloramphenicol (100%), ciprofloxacin and norfloxcin (92.31% each). All Aeromonas strains were resistant to erythromycin and penicillin G