A thesis submitted to the Faculty of Medicine, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements of Doctor of Philosophy. Johannesburg 1991 / Trimethoprim is a broad-spectrum antimicrobial agent frequently used either in combination with sulphamethoxazole (cotrimoxazole) or alone in the treatment of urinary and respiratory tract infections. Since the introduction of this drug in 1969 resistance to it has been monitored in several centres in Europe continuously but only intermittently in the United States of America and developing countries in Africa, Asia, Central and South America. In Europe the incidence of trimethoprim resistance has increased significantly in the last 20 years. In developing countries no trends have been established but the incidence of resistance appears to be greater in these countries than in Europe or the USA. / IT2018

A unique undescribed gram-negative rod is extensively characterized in this study. The cells of this unusual water isolate measure 1.2 x 6.5 microns. The most distinguishing characteristic of the bacterium is a polar tuft of 35-40 flagella that aggregate to function as a single organelle which is visible under phase contrast.

Burkholderia cepacia complex (Bcc) bacteria reside in soil, plant rhizospheres, and water, but the prevalence of Bcc in outdoor environments is not clear. In this study, we sampled a variety of soil and rhizosphere environments with which people may have contact: playgrounds, athletic fields, parks, hiking trails, residential yards and gardens. A total of 9l soil samples was obtained from three large U.S. cities (Philadelphia, PA, Cleveland, OH, and Portland, OR). In the first phase of the study, putative Bcc isolates were recovered on Burkholderia cepacia selective agar (BCSA) and trypan blue tetracycline medium (TBT). Isolates were sent to the Burkholderia cepacia Referral Laboratory and Repository, where they were identified using biochemical tests, growth at 32��C, and polymerase chain reaction (PCR) assays targeting both rRNA and recA gene sequences. Bcc isolates were genotyped by using RAPD, PFGE and rep-PCR. A total of 1013 bacterial isolates were examined, and 68 were identified as B. cepacia complex. The majority of these were B. pyrrocinia or genomovar VII (B. ambifaria); however, a few genomovar III isolates were also recovered. Fourteen (15%) of 91 soil samples yielded Bcc isolates. In the second phase of the study, DNA was extracted from 87 of the 91 soil samples and examined with PCR assays targeting Bcc 16S rRNA gene sequences. By using assays developed by LiPuma et al. (1999), 82% of the soil samples were positive for at least one Bcc genomovar, whereas 94% of samples were positive for at least one Bce genomovar using the Bauernfeind et al. (1999) assay system. Selected amplicons generated from four soil samples were cloned, and plasmids from multiple transformants (total=120) were screened by RFLP analysis. Among the clones evaluated from three of four soil samples, 90% or more had the "Burkholderia" RFLP pattern. In the remaining soil sample, only 9.5% of the evaluated clones displayed this profile. Sequence analysis of the 463bp 16S rRNA inserts from eight clones with the "Burkholderia" RFLP pattern indicated that all were from members of the Bcc. However, the four soil samples from which these clones were generated did not yield isolates identified as Bcc. This study indicates that the use of selective media may not be the best way to estimate the environmental prevalence of Bcc in soils. The natural populations of Bcc in soils with which people commonly have contact may be much higher than previously estimated. / Graduation date: 2002

Twenty-three marine and two terrestrial gram-negative bacteria were examined by electron microscopy for the effect on the outer membrane of the cells of washing the organisms successively in 0.5M NaCl and 0.5M sucrose. Six marine bacteria lost their outer membranes completely, three lost large segments but not all of their outer membranes, and six retained their outer membranes but with either gross distortions of the outer membrane and/or segments of outer membrane removed from some cells. The remaining eight marine and two terrestrial bacteria appeared to have continuous outer membranes after application of the wash procedure. / Eighteen of the twenty-three marine bacteria employed in the wash treatment study and two terrestrial bacteria were examined for the effect of washing and suspending the organisms in various solutions with respect to lysis of the cells and Optical Density (O.D.) changes of suspensions. / A spectrum of lytic susceptibility was observed among the marine bacteria ranging from those organisms which lysed in distilled water after exposure to Mg('2+) through organisms which lysed upon suspension in distilled water after pre-exposure to NaCl but which failed to lyse in distilled water if pre-exposed to Mg('2+) to organisms which failed to lyse in distilled water even after exposure to NaCl. E. coli and Ps. aeruginosa also fell within this spectrum. / After exposure to NaCl and subsequent suspension of these organisms in decreasing concentrations of either NaCl, KCl or MgCl(,2), concentrations of KCl two to three times that of NaCl or ten to four hundred times that of MgCl(,2) could protect most marine organisms from lysis or larger decreases in the O.D. of their suspensions. However, three marine and both terrestrial bacteria required only equal concentrations of KCl or NaCl to effect protection. / No overall distinction can therefore be made between marine and terrestrial bacteria with respect to the status of the outer membrane of these organisms after washing them in NaCl and sucrose solutions or the sensitivity of the two groups of organisms to lysis in distilled water after pre-exposure to NaCl or MgCl(,2).

No description available.

Thesis (doctoral)--University of Helsinki, 2007. / Includes bibliographical references. Also available on the World Wide Web.

Thesis (M.S.)--Rochester Institute of Technology, 1990. / Includes bibliographical references (leaves 46-48).

Thesis (doctoral)--University of Göteborg, Sweden, 1980. / Includes bibliographical references.

Thesis (M.S.)--Duquesne University, 2005. / Title from document title page. Abstract included in electronic submission form. Includes bibliographical references (p. 100-110) and index.

Thesis (MTech (Medical Technology))--Cape Technikon, 1998. / This study was undertaken to investigate resistance to aminoglycoside antibiotics and the transfer of resistance in selected Gram negative bacilli in hospitals in the Greater Durban area in order to determine whether the development of resistance in this region was similar to that found in other countries and whether it was the same in the hospitals in the region. It was intended that the study might expose the existence of nosocomial pathogens of a particular strain or endemic plasmids responsible for aminoglycoside antibiotic resistance. Strains of Klebsiella, Enterobacter and Serratia species and Escherichia coli resistant to gentamicin, tobramycin, netilmicin or amikacin were obtained. Resistance of the isolates obtained to the above aminoglycoside antibiotics was confirmed using a disc diffusion technique. Resistance mechanisms were initially assigned on the basis of resistance to these four aminoglycoside antibiotics. In approximately 50% of the isolates, including donor isolates and their respective transconjugants, resistance mechanisms were confirmed or revised on the basis of a changed resistance profile to a range of 12 aminoglycoside antibiotics in conjunction with DNA/DNA hybridization tests. Bacterial conjugation studies were performed on selected isolates to investigate the transfer of aminoglycoside resistance from Klebsiella pneumoniae isolates to recipient Escherichia coli. Plasmid profiles of all isolates and Escherichia colitransconjugants were compared to establish similarities. Isolates in three of the four genera of bacteria and all isolates collectively, demonstrated the greatest incidence of resistance to tobramycin. Amikacin resistance was, in all groups of isolates, the least frequently encountered. Collectively, the most frequent mechanisms of resistance were the AAC(3)-V and AAC(6')-1 enzymes One large hospital showed a high frequency of the AAC(3)-V modifying enzyme while in other hospitals a wider range of enzyme resistance mechanisms were evident. Plasmid profiles were generally dissimilar within and between different genera and the different hospitals. / Mangosuthu Technikon Research Fund