Adaptation ofEscherichia colito the Bovine Mammary Gland

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Abstract
Clinical mastitis in six Somerset dairy herds was monitored over a 12-month period.Escherichia coliwas implicated in 34.7% of all clinical cases. Forty-one percent of all clinicalE. colimastitis cases occurred in just 2.2% of the population. A total of 23.9% of clinicalE. colicases occurred in quarters suffering recurrent cases ofE. colimastitis. The genotypes of strains involved in recurrent cases of clinicalE. colimastitis were compared by DNA fingerprinting with enterobacterial repetitive intergenic consensus primers. In 85.7% of cases of recurrent quarterE. colimastitis, the same genotype was implicated as the cause of disease, suggesting persistence of the organism within the mammary environment. The same genotype as that in the original case was also implicated in 8.5% of recurrent cases occurring in different quarters of the same cow, suggesting spread between quarters. These findings challenge our current understanding of the epidemiology ofE. colimastitis and suggest that pathogen adaptation and host susceptibility may be playing a part in the changing pattern of clinical mastitis experienced in the modern dairy herd.