Septicaemic potential and serum resistance among intestinal Escherichia coli of neonatal calves Sharma K.K.*, Soni S.S. Department of Veterinary Microbiology, College of Veterinary and Animal Science, Rajasthan Agricultural University, Bikaner-334001, (Rajasthan) ** Corresponding author: Assistant Professor, Department of Veterinary Microbiology, College of Veterinary Science and AH, NAU, Navsari; kishan12sharma@redffmail.com
Abstract The present study was designed to determine septicaemic potential and serum resistance of E. coli, which were isolated from neonatal calf diarrhoea. A total of 97 E. coli with different serovars were used for the study. The septicaemic potential was measured with two tests viz., Congo red dye agar test and Sereny test. Serum resistance was measured by microtitre plate assay method. Out of 97 isolate tested, 46 were found CR positive, while 51 did not bind the dye and declared negative. Confirmation of CR test was done with Sereny test. All CR negative E. coli were also negative with Sereny test. But, out of 46 CR positive isolates, only 27 gave positive reaction in Sereny test. CR test was found 100% specific and 58.59% sensitive in detection of bovine invasive E. coli. The serovars found potentially septicaemic in the present study were O2, O5, O8, O9, O21, O25, O42, O48, O60, O78, O 86, O101, O 109, O123, O136, and O158. Six point two five per cent serum concentration was chosen to determine relationship between septicaemia and serum resistance. Out of 46 CR positive, E. coli 23 (50%), 15 (32.60%) and 8 (17.39%) were serum sensitive, intermediate and resistant, respectively. When Sereny test was taken as criterion of septicaemia, out of 27 isolates, 12 (44.44%), 10(37.03%) and 5 (18.51%) were sensitive, intermediate and resistant to bactericidal effect of serum. It can be concluded that serum resistance increased as septicaemic potential increased. But, no relation between serum resistance and serovars could be established. Top |