Thesis (M.S.)--University of Wisconsin--Madison. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 90-96).

1 Microbiology Laboratory, Charlotte Maxeke Johannesburg Academic Hospital, Department of Clinical Microbiology and Infectious Diseases, National Health Laboratory Service and University of the Witwatersrand, Johannesburg / Background: Clostridium difficile is a common cause of healthcare-associated diarrhoea. Laboratory testing for C. difficile infection (CDI) remains an area of confusion as there is not a single accepted reference standard or a single best test. Aim: To analyse the impact of different diagnostic methods on reported CDI rates. In addition, CDI incidence rates at Charlotte Maxeke Johannesburg Academic Hospital (CMJAH) were determined. Method: Results of stool samples submitted for C. difficile testing at CMJAH from 1 January 2014 to 31 August 2017 were reviewed. From January 2014 to July 2016, samples were tested by polymerase chain reaction (PCR) or toxin immunoassay, and from August 2016 to August 2017 algorithm-based testing (glutamate dehydrogenase and toxin immunoassay followed by PCR) was performed. Results: A total of 4829 samples were submitted. For the first period, toxin immunoassay and PCR showed a positivity rate of 11.4% and 21.1%, respectively, with an overall positivity rate of 18.7% (95% CI: 15.6 – 21.9). For the second period, the positivity rate was 15.9% (95% CI: 11.3 – 17.7). This rate included samples that were GDH positive and either showed toxin production or had a positive Xpert® result. CDI incidence for the two periods was different, with an incidence rate of 8.8 and 6.1 per 10 000 patient-days for the first and second periods, respectively. Conclusion: The choice of laboratory testing method has a major impact on the diagnosis of CDI, and therefore on the reported rates of CDI. Standardisation of laboratory testing and incidence rate reporting is required in order to obtain robust and reliable data. / E.K. 2019

Thesis ( M.Sc.) -- University of Adelaide, Dept. of Pathology, 1983. / Typescript (photocopy).

Thesis (Ph. D.)--University of Missouri--Columbia, 1997. / "December 1997." Typescript. Vita. Includes bibliographical references (leaves 100-109). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri--Columbia, 1997. / Typescript. Vita. Includes bibliographical references (leaves: 100-109). Also available on the Internet.

Call number: LD2668 .T4 1986 R63 / Master of Science / Diagnostic Medicine/Pathobiology

Clostridium perfringens type E iota toxin is implicated in some cases of fatal diarrhea in calves, lambs, and guinea pigs. A crossreacting "iota-like" toxin, produced by Clostridium spiroforme, is responsible for antibiotic-associated and weaning related enterotoxemias of rabbits. Antisera developed against culture supernatant of either organism neutralized the biological activity of iota or iota-like toxin. By using C. spiroforme antiserum and crossed immunoelectrophoresis (crossed IEP), we found two cross-reacting antigens in C. perfringens type E supernatants. C. perfringens types A, B, C, and D, which do not produce iota toxin, did not cross-react with C. spiroforme antiserum. To determine if either antigen had iota toxin activity, we separated the cross-reacting antigens of C. perfringens by preparative isoelectric focusing (IEF) and tested all IEF fractions for biological activity in guinea pigs and mice. The fraction containing the faster-migrating antigen seen in crossed IEP, designated iota b (i_b), had some guinea pig dermonecrotic and mouse lethal activity. Other fractions, including the one containing the slower migrating iota a (i_a) antigen, had little to no biological activity. When fractions containing i_a and i_b were mixed, there was an 8 and 25 fold increase in mouse lethal and dermonecrotic titers, respectively. Activity was neutralized by C. perfringens type E or C. spiroforme antisera and other fractions, when mixed with i_a or i_b, did not have a synergistic effect. Both components of C. perfringens iota toxin were purified using ammonium sulfate precipitation, DEAE anion exchange chromatography, preparative IEF, Sephadex G-100 gel filtration, and flatbed electrophoresis to yield a 12 and 5% final recovery of i_a and i_b, respectively. Each protein was homogeneous by SDS PAGE, gradient PAGE, and crossed IEP using homologous antiserum. There was at least an 8 fold increase in mouse lethal titer and 64 fold increase in dermonecrotic titer when equimolar amounts of i_a and i_b were mixed. Monospecific antisera against purified i_a and i_b neutralizd the iota or iota-like activity of crude supernatants. A sensitive and specific ELISA was developed using monospecific and C. spiroforme antisera. The i_a and i_b proteins have a pI of 5.2 and 4.2 and molecular weights of 48,000 and 71,000 (SDS PAGE), respectively. The i_a protein is heat stable (85° C/15 min) while i_b lost its activity at 55°C. Amino terminus sequencing revealed that both proteins were blocked by an unknown functional group(s). Purified i_a, but not i_b, has ADP-ribosylating activity specific poly-L-arginine in vitro. Recent evidence suggests that nonmuscle actin, involved in the cytoskeletal structure of eucaryotic cells, may act as the in situ acceptor. / Ph. D.

A quantitative competitive binding "triple sandwich" enzyme immunoassay was used to evaluate pathogen/class-specific antibody responses in Holstein-Friesian calves vaccinated against Clostridium perfringens B-toxin at various ages postpartum. Vaccination of dams at six weeks and again at two weeks prepartum increased pathogen-specific antibody levels in their colostrum and respective calf's serum. Calves initially vaccinated at three days produced both a primary and secondary pathogen-specific antibody response, whereas calves initially vaccinated at 12 and 21 days produced only secondary responses. Maternally-derived antibodies were found to suppress neonatal antibody production following primary immunization. They were also found to influence secondary humoral immune responses, although in a diminished capacity. Pathogen-specific IgG and IgM concentrations in dams' sera and colostra were found related to subsequent pathogen-specific IgG and IgM neonatal serum concentrations. Only pathogen-specific IgA in dams' colostra was correlated to neonatal levels, possibly owing to a different origin and role of this immunoglobulin class. All class-specific colostral immunoglobulin levels were related to subsequent neonatal concentrations. Based on results from this experiment, it is recommended that calves be vaccinated at three days postpartum with a booster administered at 63 days.

Source: Masters Abstracts International, Volume: 46-04, page: 2097. Adviser: Herbert L. DuPont. Includes bibliographical references.