Isolation and Identification of Pathogenic Bacteria Causing Neonatal Diarrhea Present in Bovine Colostrum, from San Miguel de Bolívar, Ecuador

Calves are born agammaglobulinemic, meaning they lack antibodies in their immune system. Therefore, it is essential in cows to transfer these defense mechanisms through colostrum. However, colostrum can be a vehicle for pathogenic microorganisms causing diarrhea. The objective of this study was to identify pathogenic bacteria in ۲۰ samples of bovine colostrum from San Miguel de Bolívar, Ecuador. The isolation of bacteria was carried out using culture methods, followed by their characterization using phenotypic and biochemical tests, and then their susceptibility to oxytetracycline, amoxicillin, sulfamethoxazole with trimethoprim and cephalexin was evaluated by the disk diffusion method, following CLSI standards. Antibiotics used were: oxytetracycline (T۱), amoxicillin (T۲), sulfamethoxazole + trimethoprim (T۳), and cephalexin (T۴). All ۲۰ colostrum samples analyzed showed bacterial growth, identifying ۵ pathogenic genera in ۱۲ samples: Salmonella spp. (۴۱.۶۷%), Escherichia coli (۲۵%), Listeria spp. (۶.۶۷%), and Corynebacterium spp., Arcanobacterium spp. (۸.۳۳% each). In susceptibility tests, all were resistant to amoxicillin (T۲), except Salmonella spp. regarding cephalexin (T۴). Oxytetracycline inhibited Salmonella, E. coli, and Corynebacterium spp., while half of Listeria spp. were resistant and the other half sensitive. Arcanobacterium spp. resisted oxytetracycline, but sulfamethoxazole plus trimethoprim inhibited all genera. These findings suggest that beta-lactams are ineffective against diarrhea in calves in San Miguel de Bolívar.

Keywords:

Colostrum , Bacteria , Diarrhea , Antimicrobial susceptibility