Förekomst av Klebsiella pneumoniae i avföring hos mjölkkor : en riskfaktor för mastit?

Abstract: Cows affected by mastitis caused by Klebsiella (K.) pneumoniae often become seriously ill. In some cases herdproblems may occur. Contaminated bedding material is considered to be one of the most common risk factors for klebsiella mastitis. In a recently performed study in USA it was found, however, that more than 80 % of healthy, lactating dairy cows excreted K. pneumoniae in faeces. Such a high degree of excretion of klebsiella bacteria was considered to possibly be a new risk factor for mastitis. The overall aim of this work was to find more knowledge regarding important risk factors for klebsiella mastitis in Swedish dairy cows. More specifically one aim was to test out a method for analysis of K. pneumoniae in faecal samples from dairy cows, and with the use of this method investigate the presence of K. pneumoniae in faeces from dairy cows in Swedish herds with or without problems due to klebsiella mastitis. To better understand the spread of K. pneumoniae within Swedish dairy herds another aim was to compare isolates of K. pneumoniae from milk samples from clinical cases of mastitis, faecal samples and environmental samples using PFGE. One hundred faecal samples were collected from one hundred dairy cows on ten farms. Five of these farms had problems with Klebsiella mastitis. The samples were analysed by a method based on a recently developed American method to detect Klebsiella pneumoniae in faeces of dairy cows. MacConkey agar containing ampicillin was used. Confirmation of the diagnosis K. pneumoniae was done using API 20E. Twenty-two milk isolates, five environmental isolates and two faecal isolates from the five farms with mastitis problems were genotyped using PFGE (pulsed-field gel electrophoresis). One faecal sample from a farm with mastitis problems was positive for K. pneumoniae. Two isolates came from this sample. Among in total twenty-seven isolates (milk, environmental and faecal) thirteen pulsotypes were found, and six of those were found more than once. One pulsotype was found in milk isolates from two farms. On two farms, all samples belonged to the same herd specific pulsotype. On another farm, one environmental isolate had the same pulsotype as a milk isolate. Two other milk isolates from the same farm were of the same pulsotype. The two faecal isolates belonged to the same pulsotype. In the rest of the cases single isolates were found of the remaining pulsotypes. Faecal shedding of K. pneumoniae does not seem to be an important risk factor for klebsiella mastitis in Swedish dairy cows. The PFGE results showed large diversity among milk isolates, but that farm outbreaks of klebsiella mastitis caused by the same klebsiella strain can occur.