Microbiological characterization and genetic analysis of bacteria isolated from blood cultures and fecal samples in calves with symptoms of septicemia and diarrhea

Diarrhea in calves can be caused by bacteria, viruses, and parasites. Among bacteria, Escherichia coli is considered responsible for the appearance of enteric diarrhea and septicemia in these animals, conditions that require immediate attention. Among E. coli infections of calves, more focus is placed on intestinal pathogenic (InPEC) infections, and extra – intestinal pathogenic (ExPEC) infections are ignored. This study aims to reveal which E. coli pathotype causes the infection as molecular and serotype and to reveal the differences according to the age groups of the factors in the herd. Blood and fecal samples of 10 calves aged 3 – 15 d with diarrhea were analyzed. The primary agent causing enteritis was determined by examining the stool samples with BoviD – 5 Ag. Then, samples were subjected to culture and identification processes. It was determined that the stool samples had 2/10 with E. coli K99, 4/10 with rotavirus, and 4/10 with mixed rotavirus infections and Cryptosporidium spp. E. coli was detected from all blood samples by hemoculture. The study isolated only the SepEC and ETEC groups from samples. All SepEC isolates were determined to carry type 1 pilus responsible for adhesion. In addition, it was determined that 9/10 of the SepEC group carried the colicin V gene responsible for pathogenicity. Also, all E. coli isolated from calves aged 3 – 15 d were found to be resistant to antibiotics. In conclusion, primary enteritis is caused by rotavirus Cryptosporidium spp. and ETEC. However, it was determined that SepEC group E. coli causing septicemia showed different antigenic and genetic features than E. coli in the intestinal tract. The virulence factors of the SepEC group may vary due to genomic plasticity, and their antigenic structures should be more closely examined and added to vaccine test studies.