The antibiogram and role of antibody in prophylaxis to Escherichia coli O157:H7 infection in albino rats was investigated in this study. 500 stool samples were collected from apparently healthy individuals, out of which 80 were positive for the organism. The sensitivity patterns of the isolate to conventional antibiotics were investigated. Moreover, the role of antibodies to actively or passively protect albino rats against E. coli O157:H7 infection was also carried out. The antibody used for the passive protection test was raised in rabbits immunized with the organism. The isolates were sensitive to the test antibiotics in an increasing order as follows: septrin (0%), ampicillin (0%), nalidixic acid (2.5%), augmentin (5%), ciproflox (5%), peflacine (16.25%), tarivid (16.25%), ceporex (16.25%), streptomycin (33.7%) and gentamycin (81.25%). All the isolates displayed multiple resistance to all the antibiotics used. Three (3.75%) of these were resistant to 3 of the antibiotics, 2(2.5%) to 4 of the antibiotics, 25 (31.25%) to 5 of the antibiotics, 24 (30.0%) to 6 antibiotics, 20 (25.0%) to 7 of the antibiotics, 4 (5.0%) to 8 of the antibiotics, 0 (0.0%) to 9 antibiotics, and 2 (2.5%) to all the 10 antibiotics used. For the immunization assay, after the primary immunization of the animals, the antibody titre of the animals averaged 1:85.3 for rabbits and 1:128 for rats. These values increased after the administration of the booster dose to 1:2048 for rabbits and 1:512 for rats. In the protection assay, only active immunization with live cells of E. coli O157:H7 protected the rats from infection, passive immunization did not protect them from infection despite using antibody of high titre value (1:2048) against the infection in albino rats. This study showed that E. coli O157:H7 isolated from apparently healthy individuals displayed multiple resistance to all the antibiotics. However, in case of an outbreak, gentamycin can be used for treating infection caused by the pathogen. For prophylaxis, however, active immunization with live cells of E. coli O157:H7 is recommended.
Key words: Escherichia coli O157:H7, albino rats, antibiotics, immunization.
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