Srithanasuwan Anyaphat, Pangprasit Noppason, Suriyasathaporn Witaya
Department of Food Animal Clinic, Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai, Thailand.
Akkhraratchakumari Veterinary College, Walailak University, Nakhon Si Thammarat, Thailand.
Front Vet Sci. 2022 Apr 18;9:806674. doi: 10.3389/fvets.2022.806674. eCollection 2022.
The objectives of this study were determined by two experiments including Experiment 1 (EXP1) using obtained from a weekly longitudinal study to compare virulence patterns between transient and persistent intramammary infection (IMI), and Experiment 2 (EXP2) using a stored-known-appearance PFGE strain of a contagious to determine a change of virulence patterns after long-term transmission. For EXP1, quarter milk samples from 31 milking cows were aseptically and longitudinally collected once a week for 10 weeks. A total of 14 isolates from quarters with 1 and >4 weeks of duration of IMI were categorized as transient and persistent IMI, respectively. For EXP2, 11 isolates of a stored-known-appearance PFGE strain of from our previous study (1) were randomly selected, including 5 from transient IMI (1 month) and 6 from persistent IMI (>1 month). The virulence profiles of all isolates were investigated, including , and CAMP factor or , using PCR. The Kaplan-Meier estimates were used to calculate the duration of IMI in EXP1. Approximately 50% of field IMI was spontaneously cured within 1 week, while 25% was not cured within 10 weeks. From EXP1, 4 virulence patterns were found in 14 isolates. The majority of patterns for transient did not include (63.6%), the gene relating to capsule formation. Regardless of transient or persistent IMI, a high similarity of the virulence pattern within a PFGE strain was found in EXP2. Few changes of virulence pattern within a PFGE strain were found or were related to its subsequently changing to transient IMI.
本研究的目标由两个实验确定，包括实验1（EXP1），该实验使用从每周纵向研究中获得的数据来比较短暂性和持续性乳房内感染（IMI）之间的毒力模式；以及实验2（EXP2），该实验使用一种传染性病原菌的已知外观的储存PFGE菌株来确定长期传播后毒力模式的变化。对于EXP1，每周无菌纵向采集31头泌乳奶牛的四分之一乳样，持续10周。从IMI持续时间为1周和超过4周的乳腺中分离出的总共14株菌株分别被归类为短暂性和持续性IMI。对于EXP2，从我们之前的研究（1）中随机选择11株已知外观的储存PFGE菌株的分离株，包括5株来自短暂性IMI（1个月）和6株来自持续性IMI（超过1个月）。使用PCR研究所有分离株的毒力谱，包括[具体毒力指标未明确给出]和CAMP因子或[具体毒力指标未明确给出]。使用Kaplan-Meier估计法计算EXP1中IMI的持续时间。大约50%的现场乳房内感染在1周内自然治愈，而25%在10周内未治愈。从EXP1中，在14株分离株中发现了4种毒力模式。短暂性[病原菌未明确给出]的大多数模式不包括与荚膜形成相关的基因（63.6%）。无论短暂性还是持续性IMI，在EXP2中发现同一PFGE菌株内毒力模式高度相似。在同一PFGE菌株内发现毒力模式很少变化，或者与随后转变为短暂性IMI有关。
