Recurrent clinical mastitis caused by Escherichia coli in dairy cows

In this study, the occurrence of persistent intramammary infections caused by Escherichia coli with recurrent episodes of clinical mastitis caused by E. coli are described for a cohort of 300 Dutch dairy herds. Calculations o n the recurrent episodes were based on data collected by dairy farmers. The genotype of the E. coli strains was determined by means of a polymerase ch ain reaction using enterobacterial repetitive intergenic consensus (ERIC) p rimers, resulting in a DNA fingerprint. Quarters in which the same E. coli genotype was found were considered to be persistently infected. In 4.77% of all episodes of clinical mastitis caused by E. coli, persistent intramamma ry infections caused by the same E, coli genotype were found. Based on the occurrence of the same genotypes, we concluded that, in 2.98% of all episod es, transmission of E. coli strains among quarters within one cow might hav e occurred. In 13.04% of all episodes of clinical mastitis caused by E. col i in the study, different E. coli genotypes were isolated from recurrent ep isodes of clinical mastitis within the same cow, indicating that these cows were highly susceptible to recurrent intramammary infections caused by E. coli.