Genetic Studies on Escherichia Coli Strains Isolated From Cases of Bovine Mastttis

Abstract

This study was carried out on 53 milk samples positive for California Mastitis Test taken from eight herds infected with clinical mastitis in Taif City. Mean Somatic cell Count (SCC) was 4, 482, 000 cells / ml. Forty-eight (51.06%) E .coli strains were isolated from bovine mastitic milk by bacteriological methods. From these E .coli strains, 27 were characterized with regard to their serotype and their DNA polymorphism pattern with REP and ERIC primers, special attention was given to recurrent E .coli mastitis in cows . For studying the epidemiology of clinical E . coli mastitis, the combination of serotype and DNA pattern detected , was used in this investigation .It was assured that the PCR reaction with the ERIC primers can be used in the field of E. coli strains identification. Based on the DNA polymorphisms patterns of E. coli isolates from clinical mastitic cows , it revealed that isolates have a great variations in regard to their genotypes. During the same lactation period, it was detected more than one clinical mastitis case associated with E . coli, but this clinical mastitic occurrence was irregularly. Whatever the occurrence, at this rate, E . coli strains isolated from the separate episodes of inflammation, were for the most part, of the same serotype and had the same DNA amplification pattern. Therefore, the PCR DNA amplification method can not replace serotyping in epidemiological studies .