Transfer and shedding of a rifampicin-resistant strain of Escherichia coli (RREC) among cattle was studied in a research feedlot comprised of 30 pens of 11 or 12 yearling steers. On 3 separate occasions, 9,6 and 6 of the 12 steers in 3 different peripheral pens in the lot were orally inoculated with 1011 cells of an unmodified RREC isolate from bovine feces. Fecal swabs were preformed on all 360 steers in the feedlot immediately prior to and at approximately 5-week intervals thereafter. Following inoculation, fecal grab samples were collected daily from all 12 pen mates for up to 4 months. In all 3 trials, the inoculated steers each shed RREC within 24 h of inoculation. All 12 steers in each inoculated pen were positive for RREC within 48 h; all 36 steers shed RREC intermittently throughout the three sampling periods. Transfer to 4 steers in an adjacent pen was confirmed only during the first trial (3 steers shed once each on day 8, day 26 or day 40; the fourth shed on 6 occasions between days 8 and 40). Transfer to non-adjacent pens was not detected during any of the 3 trials. All recovered RREC isolates were compared to the inocula using LMX agar and fatty acid methyl ester (FAME) analysis. Additionally, select recovered isolates were subjected to carbon source utilization tests. The three inocula were further subjected to 16S rRNA sequence analysis, minimum inhibitory antibiotic concentration profiles and pulsed-field gel electrophoresis and were determined to be the same strain. It was observed with the exception of the pen floor, that the resistant strain did not move through the animal feedlot environment, as easily or pervasively as other studies suggested. The RREC did not persist in the feedlot environment beyond the 4-month trial period. Fecal contamination form the pen floor, animal-to-animal contact and the chute system may have facilitated transfer of the resistant strain between animals. Animal stress may have facilitated the pen-to-pen transfer observed during trial 1, as the inoculation was conducted within 1 week of the steers' arrival in the feedlot. / xii, 102 leaves : ill. ; 28 cm.

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Abstracts in English and Zulu / Fluorescence polarization assay (FPA), a serological assay, was validated as an alternative test for the rapid and cost-effective diagnosis of bovine brucellosis, with the aim of improving the control of brucellosis in South Africa. The FPA is anticipated to distinguish between vaccinated and infected cattle, circumventing the challenge associated with the tests that are currently used. Positive cattle serum samples (n =420) confirmed by Complement Fixation Test were tested in conjunction with serum samples (n = 446) from non-infected cattle initially tested on Rose Bengal Test, CFT and compared with FPA. The optimum cut-off value that offers the highest diagnostic sensitivity (Dsn) and diagnostic specificity (Dsp) was determined as 87 mP with the use of ROC analysis. The Dsn and Dsp of FPA using this cut-off value was calculated at 99.09% - 100% and 68.09%- 76.61% respectively with a 95% confidence interval (cl). The area under curve (AUC) was calculated at 0.9842 with a 95% standard error (S.E) of 0.005532 with positive and negative likelihood ratio (+LR) (-LR) at 3.643 and 1.002, respectively. The FPA was found to be as effective as CFT and should be considered because of its accuracy and other advantages such as speed, high throughput and the objectivity of the interpretation of results that can be obtained electronically by the (PHERAstar) machine. The test should be included in routine serological diagnosis for brucellosis. / I- Fluorescence polarization assay (i-FPA) ukuhlolwa kwe-serological okuqinisekiswe njengenye indlela yokuhlola ukuxilongwa okusheshayo nengabizi kwe-bovine brucellosis, okuzokwenza ngcono ukulawulwa kwe-brucellosis eNingizimu Afrika. Ngaphezu kwalokho, i-FPA kulindeleke ukuthi yehlukanise phakathi kwezinkomo ezigonyiwe nezithelelekile futhi lokhu kuzonciphisa inselelo ehambisana nokuhlolwa esetshenziswa njengamanje. Amasampula amahle avumayo we-serum ezinkomo (n = 420) aqinisekiswa yi-CFT ahlolwe ngokuhlangana namasampula e-serum (n = 446) avela ezinkomeni ezingathelelekile ezahlolwa kuqala ku-RBT, CFT futhi kuqhathaniswa ne-FPA. Inani elinqunyiwe elikhulu elinikezela ukuzwela okuphezulu kokuxilonga (i-Dsn) kanye nokucaciswa kokuxilongwa (i-Dsp) kunqunywe njenge-87 mP kusetshenziswa ukuhlaziywa kwe-ROC. I-Dsn ne-Dsp ye-FPA esebenzisa leli nani elisikiwe libalwe ngama-99.09% - 100% no-68.09% - 76.61% ngokulandelana kwesikhathi sokuzethemba esingu-95% (cl). Indawo engaphansi kwe-Curve noma ijika thizeni (i-AUC) ibalwe ku-0.9842 enephutha elingu-95% elijwayelekile (SE) lika- 0.005532 elinezilinganiso ezinhle nezimbi ze-likehood (+ LR) (-LR) ngo-3.643 no- 1.002, ngokulandelana. I-FPA isebenza njenge-CFT futhi kufanele ibhekwe ngenxa yokunemba eneqiniso kwayo nezinye izinzuzo ezifana nejubane lokuthola imiphumela kanye nenhloso yokuchazwa kwemiphumela engatholakala ngomshini wekhomphuyitha (PHERAstar), i-FPA kufanele ifakwe ekuhlolweni okuvamile ngokujwayelekile kwe-serological ye-brucellosis. / Agriculture and  Animal Health / M. Sc. (Agriculture)