Characterization of plasmids of Escherichia coli isolated from mastitis
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Date
1993
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Department of Veterinary Microbiology, College of Veterinary and Animal Science, Mannuthy
Abstract
Escherichia coli. were isolated in 15.33 per cent cases of mastitis. Of the 46 E. coli isolated 43 were resistant to one to nine antibiotics and three were sensitive to all the 13 antibiotics tested. The organisms were resistant to rifampicin (78.26%) followed by oxytetracycline (50%), tetracycline (37.78%), nalidixic acid (19.56%), co-trimoxasole (8.69%) and gentamicin (6.52%). All the organisms were susceptible to kamamycin and norfloxacin. Among the .multiple drug resistance oxytetracycline - rifampicin (OR) resistance was noticed in 76.2% cases. Twenty-six different patterns of antibiotic resistance were noticed among 43 E. coli isolates giving a reliability of 60.46 per cent in differentiating the isolates. Hence, antibiogram could only be used as an adjunct to plasmid profiling in epidemiological studies.
The resistograms revealed cent per cent resistance to lead, followed by antimony (32.6%), copper (30.43%), silver(19.56%) and cetrimide (2.17%). All the isolates were sensitive to cadmium and mercury. Among the 46 E. coli isolates, 9 different resistogram patterns were obtained giving reliability of 19.56 per cent in differentiating the strains.
A correlation between the antibiotics and heavy metal ac; lead an+-imcny and copper, was observed inresistance such as leaa, descending order.
of the forty-six E. coli isolates three (6.52%) were hemolytic on sheep blood agar. Two of the three hemolytic strains were also enterotoxigenic.
Thirteen of the 46 (28.26%) E. coli isolates were enterotoxigenic, when tested by rabbit ligated ileal loop assay. Two of the thirteen (15.38%) enterotoxigenic isolates were also hemolytic.
Fourteen of the 24 (58.33%) drug resistant E. coli transferred drug resistance against one or more antibiotics to the recipient organism. In none of the cases the furazolidone resistance was transferred.
All the three hemolytic E. coli isolates transferred the hemolytic character by conjugation indicating the plasmid borne nature of hemolysin production. None of the enterotoxin producing E. coli could transfer the character to recipient by conjugation.
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