CNF producing Escherichia coli isolated from cattle in Northern Ireland

Tissue culture assays were used to investigate the incidence of cytotoxic necrotising factors (CNFs) 1 and 2 in Escherichia coli strains from cattle. E. coli cultures were obtained from faeces collected from 223 cases of diarrhoea and from 113 healthy animals. In addition, strains cultured from 62 cases of mastitis, 66 cases of septicaemia and 68 cases of abortion were also investigated. E. coli producing CNF 1 or 2 were identified in all sample groups except for the abortion cases. Comparable levels of CNF1 strains were present in E. coli from the faeces of diarrhoeic (4%) and healthy faeces (4.4%) whereas lower levels of CNF2 were identified in the faeces from diarrhoeic animals (19.3%) in comparison with healthy animals (30.9%). One CNF1 producing strain was identified among the E. coli isolated from mastitis samples, while 3% and 10.6% of septicaemic strains were positive for CNF1 and 2, respectively. Serogrouping of CNF isolates did not reveal the association of any particular serogroups with the different conditions.