Thesis (Ph.D.)--University of Idaho, April 2006. / Major professor: Kenneth W. Bayles. Abstract. Includes bibliographical references (leaves 100-122). Also available online in PDF format.

published_or_final_version / Community Medicine / Master / Master of Public Health

The effect of different oxygen atmospheres on growth, energy charge and enterotoxin production of Staphylococcus aureus was investigated. Three atmospheres, air, 5% oxygen in nitrogen and 20% oxygen in nitrogen, were tested on three strains producing enterotoxins A, B and C. Colony forming units (CFU), dry weight, dissolved oxygen, pH, adenosine phosphates and adenylate energy charge and enterotoxin production were measured. The effect of sugars added to the culture media was also studied. A significant difference was observed among the atmospheres in their effect on growth in the earlier hours. Growth was fastest in air for all the strains, followed by 20% and 5% oxygen in nitrogen. Growth response of the strains to the atmospheres were similar among all three strains. Depletion of dissolved oxygen occurred with rapid growth. The pH was alkaline in all cultures by the last hours sampled. A significant difference was also observed among the atmospheres in the effect on enterotoxin production, although this differed among strains. In strains 265-1 and S-6, enterotoxin A and B production, respectively, was faster in air than it was in either 5% or 20% oxygen in nitrogen. This corresponded to the effect on growth rate. The response of strain 361 was distinctively different from the other two strains. In this strain the atmospheres of 5% and 20% oxygen in nitrogen had a stimulatory effect on the rate of production of enterotoxin C. There was a definite pattern of change in energy charge during the growth cycle of S. aureus with apparent difference among three strains. In 265-1, the energy charge increased very rapidly and reached 0.68 at 3 hr of growth; an equivalent level was reached in strains S-6 and 361 at about 8 hr after an initial lag. The time at which enterotoxin production was detectable coincided with a rapid increase in energy charge, except with a lag for strain 361. Added sugars had a slightly stimulatory effect on growth in air and a significantly stimulatory effect on growth in 5% and 20% oxygen in nitrogen. The decreased growth rate observed in 5% and 20% oxygen in nitrogen when cells were grown in the simple NAK medium was relieved in 5% and 20% oxygen in nitrogen when the sugars were added. Sugars repressed enterotoxin production by S. aureus in air. However, the repressive effect of the sugars on enterotoxin production was not observed when the cells were grown in 5% and 20% oxygen in nitrogen. The relationship of energy charge to enterotoxin production should be studied with regard to the effects of media components. / Graduation date: 1975

Digitized by Kansas Correctional Industries

Background: Methicillin-resistant Staphylococcus aureus(MRSA) is a well-recognized nosocomial agent in hospital setting, but few data about the epidemiology of MRSA in long-term care facilities are available. The aim of the study is to overview the prevalence and risk factors for MRSA carriage in an endemic situation in long-term care facilities (LTCF)settings. Methods: A keyword search was conducted in the PubMed and Medline database(January 2004through May 2014). Titles and abstracts were screened to identify the studies on MRSA prevalence and risk factors for carriage in patients in non-outbreak situations in LTCF settings. The quality of the included studies are evaluated by seven criteria(outcome definition, time unit, target population, participants, observer bias, screening procedure, swabbing sites) and referred as ‘good’, ‘fair’ and ‘poor’. Results: Twenty one observational papers were included in the review. Two of them were categorized as good quality. MRSA prevalence rates varied over a wide range, from 0% to 58%.Several factors are associated to MRSA colonization, which are host-related (such as advanced age, poor functional status, and comorbidities), antecedents (such as prior MRSA colonization, prior antibiotic therapy, prior hospitalization and transferal between acute-care hospital and LTCF) and facility specific characteristics. Conclusions: This review suggested that a wide variation of MRSA colonization among LTCFs, one of the possible causes was due to different methodological differences between studies. A standardized recommendation on swabbing sites and outcome calculations for prevalence study is needed in order to allow comparison among different healthcare settings. A better understand of risk factors for MRSA in healthcare facilities to develop a targeted infection control strategy for facilities associated colonization. / published_or_final_version / Public Health / Master / Master of Public Health

Growth and enterotoxin production of Staphylococcus aureus in papain-treated beef and ham were studied. In addition to an untreated control, four treatments were used in the beef experiment including two levels of papain, a commercial tenderizer preparation, and commercially tenderized beef. Two levels of papain treatment and an untreated control were used for the ham study. Both raw and cooked samples were tested. Proteolysis was determined by 280 nm readings in a spectrophotometer for total UV absorbing materials and for UV absorbing materials in a trichloroacetic acid soluble meat solution. The third method, a more sensitive analysis, used trinitrobenzene sulfonic acid to determine the amount of free amino nitrogen present. With the latter method some differences in the amount of amino groups present could be detected among the various treatments. Strain S-6 which produces both enterotoxins A and B was used for the experiment. The inoculum level for studies of meat slices held at 30 and 42 C was 1 x 10⁷ colony forming units per gram. Sampling times for the number of colony forming units and for enterotoxin production by microslide and Oudin assays were 5, 8, and 24 hr. The action of papain did not significantly affect the number of colony forming units nor the amount of enterotoxin produced in treated versus untreated control meat samples. The number of colony forming units at 30 C increased at a slower initial rate than at 42 C although higher numbers of viable cells were detected after 24 hr in the samples incubated at 30 C. Cooked samples supported a faster initial growth than raw samples. Earlier and greater enterotoxin B production occurred when cooked samples, especially of beef, were the substrates. Enterotoxin B concentrations in cooked beef held at 42 C were estimated to be 0.06, 0.9 - 1.0, and 0.2 - 2 μg per g for 5, 8, and 24 hr respectively. Raw beef samples contained no detectable enterotoxin until after 24 hr (0.2 - 0.9 μg per g). At 30 C approximately 1 μg per g of enterotoxin B was detected in the cooked samples and only 0.02 (μg per g in some raw samples after 24 hr. The cooked and "not fully cooked" hams were similar in support of growth and enterotoxin production. Enterotoxin B concentrations present in "hot fully cooked" samples held at 42 C were approximately 0 - 0.9 (μg per g at 5 hr, 0 - 1 μg per g at 8 hr, and from 0.05 - 1.8 μg per g at 24 hr. Enterotoxin levels in the cooked samples were 0.2 - 0.9 μg, 0.25 - 1 ug, and 1 - 6.2 μg per g after 5, 8, and 24 hr respectively. Isolated samples, positive for enterotoxin A (0.05 μg per g), were detected in cooked beef held at 42 C for 24 hr. Detectable amounts (0.05 - 0.2 μg per g) were found, however, in both the cooked and "not fully cooked" cured hams, especially at the higher incubation temperature. / Graduation date: 1972

Diss. (sammanfattning) Uppsala : Sveriges lanbruksuniv. / Härtill 4 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2001. / Härtill 5 uppsatser.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 179-196). Also available via the Internet.

Thesis (M.S.)--University of Wisconsin--Madison, 1964. / eContent provider-neutral record in process. Description based on print version record. Bibliography: l. 132-140.