LD2668 .T4 1947 T5 / Master of Science

Staphylococcus aureus is a coagulase-positive, Gram-positive, coccal bacterium. It is one of the leading causes of both skin and invasive infections. It plays an important role in diagnostics and treatment due to its ability to develop resistance to antimicrobial drugs. Methicillin-resistant Staphylococcus aureus or MRSA is an important nosocomial pathogen in both humans and animals due to its resistance to all ?-lactam antimicrobial agents. Colonization of MRSA in horses poses a great concern. This is considered an important risk factor for development of staphylococcal related diseases in horses admitted to veterinary hospitals. Colonized horses can also be a source of zoonotic MRSA infections. Methicillin-resistant Staphylococcus aureus detection based on a PCR reaction is commonly used and various types of PCR-based assays were developed to assist in early detection of MRSA. The main aim of the study was to compare the currently used conventional microbiological techniques with a published multiplex PCR assay targeting the mecA, spa and pvl genes for the rapid and accurate identification of MRSA in horses admitted to the Onderstepoort Veterinary Teaching Hospital, University of Pretoria. A total of 50 isolates, which consists of isolates from horses and their immediate environment, were included in the study of which 94% (n=47) were shown to be infected with methicillin resistant Staphylococcus aureus using conventional microbiological techniques. The remaining three gave inconsistent results. Their isolates were obtained, DNA was extracted and subjected to the multiplex PCR assay. The PCR results indicated that both the mecA and spa genes were present in 72% (n=36) of these isolates, indicative of MRSA strains. In 20% (n=10) of the isolates, only the spa gene could be detected; suggesting that these cannot be classified as being methicillin resistant. The pvl gene could not be detected in any of the isolates tested. A total of four isolates (8%) yielded results that were inconsistent with being MRSA using molecular identification. Overall there was a good correlation between genotypic analysis by PCR and phenotypic determination using S. aureus species identification and susceptibility testing methods. The multiplex PCR assay had a detection limit of 2.18 x 108 colony-forming units (cfu)/ml. This detection limit is higher compared to other published molecular identification techniques used for Staphylococcus aureus but sensitive enough for the accurate detection of MRSA in overnight cultured isolates. Results suggest that the current PCR assay could be used as a supplementary diagnostic method in the routine diagnosis for rapid, sensitive, and specific detection of S. aureus and its associated antibiotic resistance genes in equine samples. / Mini Dissertation (MSc)--University of Pretoria, 2015. / tm2016 / Veterinary Tropical Diseases / MSc / Unrestricted

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Osteoarthritis of the metacarpo/metatarsophalangeal joint is a major cause of lameness in the horse. Magnetic resonance imaging and particularly delayed gadolinium enhanced imaging of cartilage (dGEMRIC) and T2 cartilage mapping in humans has been shown to visualize cartilage matrix changes in osteoarthritis early in the disease process. T2 mapping is a non-invasive technique characterizing hyaline articular cartilage and repair tissue. In dGEMRIC, the negatively charged administered Gd-DTPA2−, penetrates hyaline cartilage in an inverse relationship to the proteoglycan concentration thereof. In osteoarthritis, proteoglycan concentration is decreased with increased penetration of Gd-DTPA2− due to a relative decrease in negative charge of the proteoglycan-depleted cartilage. This study was performed on normal cadaver limbs of twelve euthanized racing Thoroughbreds. Six horses’ midcondylar distal third metacarpals/metatarsals (Mc3s/Mt3s) underwent six precontrast inversion recovery (IR) sequences for dGEMRIC T1 relaxation time calculation, as well as T2 mapping sequences using a 1.5T machine. Gd-DTPA2- was injected intra-articularly and the same six IR sequences repeated at 30, 60, 120, and 180 minutes post-injection at the same midcondylar sites. The distal Mc3/Mt3 cartilage thickness was measured histologically and compared to selected images of the T1 and T2 weighted sequences. T1 and T2 maps were created by fitting the respective data into mono-exponential relaxation equations for each pixel, and mean values of certain regions of interest were calculated. A second group of six horses’ fore and hind limbs were randomly assigned to two groups and the limbs either chilled or frozen, allowed to return to room temperature and scanned similarly to the first control group. Chilling and freezing effects on dGEMRIC and T2 mapping results were evaluated. The main conclusions from this study are that IR and proton density weighted (T2 mapping) sequences can measure distal Mc3/Mt3 cartilage thickness where the cartilage doesn’t overlap with that of the proximal phalanx. However, accurate measurement was hampered by the thin cartilage in this region. dGEMRIC mapping, using intra-articular Gd-DTPA2- is a feasible technique and T1 relaxation times decrease in a similar fashion to that of the human, with the optimal time of scanning after intra-articular Gd-DTPA2- injection being 60-120 minutes. There is little effect on T1 or T2 relaxation time and mapping images after chilling and freezing of the limbs except where the magic angle effect predominates in the T2 mapping sequences. Limitations of this study include relatively coarse spatial resolution of the thin cartilage, the overlap of the distal Mc3/Mt3 cartilage with the adjacent phalanx and the relatively low number of limbs used, resulting in low statistical power, particularly in the frozen limbs’ study. In spite of these limitations, this study provides technical information and reference values of dGEMRIC and T2 mapping in the cadaver distal Mc3/Mt3 of the normal Thoroughbred horse of value for forthcoming studies. Future studies need to evaluate intravenous administration of Gd-DTPA2- and cartilage mapping in live exercised vs. non-exercised horses. Ultimately, dGEMRIC and T2 mapping of horse metacarpo/metatarso-phalangeal joints with differing degrees of osteoarthritis should be used to attempt to diagnose early cartilage degeneration to endeavour to halt or delay its progression. / Thesis (PhD)--University of Pretoria, 2013. / gm2013 / Companion Animal Clinical Studies / unrestricted

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Call number: LD2668 .T4 1986 D42 / Master of Science / Diagnostic Medicine/Pathobiology

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Alkaline phosphatase (ALP) is an enzyme present in intestinal mucosa, bile, bone and renal tubule cells. Bile acids have been shown to decrease ALP activity from bone and kidney but not those from intestinal origin. This action can be mimicked in serum and peritoneal fluid samples by the use of an L-phenylalanine buffer which specifically measures intestinal ALP activity only; while the standard buffer measures total ALP activity. We sought to assess the diagnostic and prognostic relationship of intestinal and total ALP activity between serum and peritoneal fluid in 126 horses with acute colic. Blood and peritoneal fluid samples were analyzed for ALP activity using both the standard and L-phenylalanine based buffers. Neither total nor intestinal serum ALP activity was useful in classifying type or severity of intestinal damage. Total and intestinal peritoneal fluid ALP activity were lowest in horses suffering simple medical colic and non-strangulated surgical lesions, and highest in surgical cases with suspected ulceration, strangulation, peritonitis and intestinal rupture. High total and intestinal peritoneal fluid ALP activity was associated with greater intestinal damage, increased probability of surgical intervention and a worse prognosis while low total and intestinal peritoneal fluid ALP activity was unable to accurately differentiate between simple medical colics and surgical colics. The use of L-phenylalanine buffer in both serum and peritoneal fluid did not improve the sensitivity of the test. Based on these results, determination of total ALP activity in peritoneal fluid may be helpful in identifying ischemic or inflammatory bowel lesions in horses with acute colic. A portable clinical analyzer (PCA) was used for the determination of venous blood and peritoneal fluid pH value, glucose, lactate and electrolyte concentrations in a hospital setting. Blood and peritoneal fluid glucose, lactate, sodium, chloride and potassium concentrations, and pH value were determined using both a portable clinical analyzer with test cartridges and an in-house analyzer in 56 horses with acute abdominal disease. Results were compared by the Bland-Altman method of comparison and linear regression. The PCA yielded higher blood and peritoneal pH values, with greater variability in the alkaline range and lower pH values in the acidic range. The PCA glucose concentrations (<150 mg/dL) were significantly lower, and were higher in the high range (>150 mg/dL). Venous lactate concentration (<5 mmol/dL) arid peritoneal fluid lactate concentration (<2 mmol/dL) had the smallest variability. On average, the PCA underestimated peritoneal lactate and glucose concentration. Peritoneal fluid sodium and chloride concentration had higher bias and variability than venous sodium and chloride concentration. Venous and peritoneal fluid potassium concentration was closely clustered around the mean with a low bias and variability. Correlation coefficients were >0.80 for all values except venous and peritoneal sodium concentration; venous chloride concentration and venous pH value. The PCA may be suitable for point-of-care biochemical analysis of blood and peritoneal fluid for horses suffering colic and may provide further diagnostic and prognostic information. The PCA may be of help in diagnosing metabolic acidosis, uroperitoneum, septic and non-septic peritonitis and intestinal ischemia. This may be of benefit to ambulatory equine clinicians. / Graduation date: 2004

The cestode Anoplocephala perfoliata is known to cause fatal colic in horses. The epidemiology of the cestode has rarely been evaluated in Canada. I detected A. perfoliata eggs in 4-18% of over 1000 faecal samples collected over 2 years. Worm intensity ranged from 1 to >1000 worms. Pastured horses were infected more often than non-pastured horses, especially in western Alberta, likely reflecting their higher rates of exposure to mite intermediate hosts. In a comparison of diagnostic techniques, fecal egg counts were the least accurate. Western blot analysis had the highest sensitivity to detect antibodies to the cestode (100%), but had lower specificity. A serological enzyme-linked immunosorbent assay (ELISA) had a lower sensitivity (70%) for detection of antibodies than described in previous studies. A coproantigen ELISA had 74% sensitivity and 92% specificity, and a positive correlation was found between antigen concentration and cestode intensity. The latter is important because it implicates the utility of this method for accurate clinical diagnosis and epidemiological studies. / viii, 70 leaves ; 29 cm.