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Title: Epidemiology, detection, molecular typing and control of porcine colonic spirochaetosis (Brachyspira pilosicoli)
Author: Corona-Barrera, Enrique
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2003
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Brachyspira pilosicoli is a Gram negative anaerobic intestinal spirochaete which is the aetiological agent of porcine colonic spirochaetosis (PCS). PCS is prevalent in the United Kingdom and many other countries. This study aimed to determine risk factors associated with PCS, assess detection procedures, investigate the genetic variation among isolates from porcine colitis outbreaks and evaluate the efficacy of disinfectant-sanitisers against B. pilosicoli in vitro. An epidemiological study was carried out using data from pig farms with and without infectious colitis to determine possible risk factors. Categorical variables including a wide range of housing and management factors were analysed. The major factors associated with infectious colitis involving B. pilosicoli were: source of breeding stock replacements (p < 0.045), presence of concurrent infection with Streptococcus suis on the farm (p < 0.038), and bedded floors (p < 0.007). Fully slatted floors were identified as a protective factor (p < 0.007). The diagnostic potential of immunomagnetic separation (IMS) for detection of B. pilosicoli and B. hyodysenteriae from faecal samples was investigated. The sensitivities of the IMS (direct and indirect methods) using polyclonal antibodies (PAbs) and monoclonal antibodies (MAbs) were evaluated and compared with the standard diagnostic method namely direct culture, and polymerase chain reaction (PCR). IMS using PAbs did not improve the diagnostic sensitivity. IMS using MAbs did not increase diagnostic sensitivity when performed with the recommended washing steps. However, IMS performed without the washing steps improved the sensitivity for detection ofB. pilosicoli and had higher sensitivity than direct culture. PCR was more sensitive than the IMS using MAbs (performed with the recommended washing steps). IMS using MAbs shows potential to improve detection ofBrachyspira spp. but further work on a method that avoids significant loss of target cells during the washing steps is required. The genetic diversity of single and multiple isolates from pig farms, two dog isolates and one human isolate ofB. pilosicoli was investigated by arbitrarily primed PCR (AP-PCR). One isolate of the different species B. hyodysenteriae was included as an outgroup. AP-PCR was optimised using four primers individually. The generated data was subjected to analysis by distance method and parsimony method. The DNA banding patterns of B. hyodysenteriae and B. pilosicoli were clearly differentiated by each primer. Phylograms were generated from DNA fragment data for each primer and for pooled data (fragment data of the four primers) to give more robustness to the analysis. The high genetic variation shown by some of the multiple isolates from the same farm suggested that infections by B. pilosicoli in UK farms might not be caused by a single (clonal) genotype. Seven disinfectant-sanitisers were tested for their efficacy against six isolates ofB. pilosicoli. The products were commercially available and included four different chemical groups: quaternary ammonium group, tar-organic acid group, caustic soda group and peroxide group. Serial 10-fold dilutions ofthe products were prepared and challenged with an inoculum of 105 bacterial cells ofB. pilosicoli. To determine the importance of thorough cleaning of farm buildings in relation to the potential of efficacy of disinfectant agents, these products were tested with and without presence of organic matter (as sterile pig faeces). Contact times of 15, 30, 45 and 60 minutes between the disinfectant agents and B. pilosicoli were evaluated. No differences were observed between contact times or between isolates. In the absence of organic matter, the highest efficacies were obtained by DSC-1000 and Long Life with 64 and 50.0 % efficacy at 1:10000 dilution, followed by Ambicide with 43.0 % efficacy at the same dilution (1:10000). In the presence of organic matter the best results were achieved by DSC-1000 and Long Life both with 14.0 % efficacy at dilution 1:1000. The presence of organic matter had a negative effect on the efficacy of the products evaluated against B. pilosicoli (P < 0.006), confirming the importance of thorough cleaning prior to disinfection. Heavy Duty and Virkon S were the most affected by the presence of organic matter with efficacies at the level of 7.0 and 0.0 %, respectively, at the 1:100 dilution. The chemical groups that showed the best performance in the presence of organic matter were the quaternary ammonium and tar-organic acids groups in particular the products DSC-100, Long Life, Ambicide and Farm Fluid.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available