Thesis (M.S.)--University of Michigan, 1970.

Thesis (doctoral)--Katholieke Universiteit te Nijmegen.

Thesis (doctoral)--Universität Tübingen, 1933. / At head of title: Aus dem Hygienischen Institut der Universität Tübingen. "Lebenslauf": p. 53. Includes bibliographical references.

Made available in DSpace on 2014-06-11T19:27:54Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-07-15Bitstream added on 2014-06-13T18:56:44Z : No. of bitstreams: 1 oliveira_dtn_me_araca.pdf: 464380 bytes, checksum: 604c14584189497c81a25c41ad98c57e (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A ação dos produtos desinfetantes sobre as propriedades físico-químicas da resina acrílica norteia sua seleção para a higienização de aparelhos ortodônticos removíveis. Avaliou-se a resistência à fratura de resina acrílica ativada quimicamente após ciclagem em diferentes soluções desinfetantes. Foram confeccionados quarenta corpos de prova com resina acrílica autopolimerizável incolor (Clássico,Ind.&Com.Ltda./Brasil) utilizando-se matriz metálica retangular e circular, seguindo-se às técnicas de polimerização sob pressão úmida (imersão em água/n=20) e sob pressão seca (sem água/n=20) foram subdivididos em 4 grupos (n=5), conforme a solução utilizada para ciclagem: água destilada (Controle), bicarbonato de sódio, hipoclorito de sódio 1% e Corega®Tabs. A ciclagem consistiu em imersão em 100 ml da solução por 10 minutos três vezes ao dia e, em seguida, manutenção em recipiente fechado contendo saliva artificial a 37ºC. Este ciclo foi realizado durante 30 dias, trocando-se as soluções e a saliva a cada procedimento executado. Na sequência os espécimes foram submetidos ao ensaio de resistência flexural a três pontos foi utilizada máquina EMIC DL3000, à velocidade de 5mm/min, dispondo-se as amostras em suporte contendo dois apoios de sustentação, sendo aplicada força axial e equidistante aos dois outro pontos até a ruptura do corpo-de-prova. Os espécimes circulares foram levados para leitura em Microscópio de Força Atômica (AFM - V Nanoscope Veeco). Os resultados, submetidos à análise de variância (P<0,001 ) e o Teste de Tuckey (P<0,05) não apontaram diferenças significantes para a resistência flexural. Conclui-se que os métodos de polimerização e as soluções testadas não modificaram a resistência flexural... / The disinfectant products action on the physicochemical properties of acrylic resin guides its selection to the cleaning of removable orthodontic appliances. The fracture resistance of acrylic resin after cycling in different disinfectant solutions was evaluated. Forty specimens were made with colorless acrylic resin (Clássico, Ind. & Com.Ltda. / Brazil), using matrix, followed by the techniques of polymerization under wet pressure (immersion in water / n = 20) and dry pressure (no water / n = 20). The samples were divided into 4 groups (n = 5) as the solution used for cycling: distilled water (Control), sodium bicarbonate, sodium hypochlorite 1% and Corega®Tabs. The cycling consisted of immersion in 100 ml of solution for 10 minutes three times a day and then maintained in a closed container containing artificial saliva at 37 º C. These cycles were conducted during 30 days, changing the solutions and artificial saliva for each procedure performed. Latter, the specimens were submitted to surface analysis with Atomic Force Microscope (AFM - Veeco Nanoscope V). A machine, EMIC DL3000, was used for the three-point flexural strength test, speed of 5mm/min, providing the sample in medium containing two restraints support. After that axial force was applied and equidistant to the two other points to the body to break the specimens. The results were submitted to analysis of variace(P<0,001) and Tuckey Test (P<0,05) showed no significant differences in flexural strength test. The Atomic Force Microscopy analysis revealed less topographical roughness for the group Corega®Tabs. We conclude that the polymerization methods and solutions tested did not alter the flexural strength of the material studied except the comparation between... (Complete abstract click electronic access below)

An increase in the number of bacteria resistant to most of the antibiotics or biocides in common use is a problem faced by industries and the community at large. More bacteria are resistant to moderate levels of biocides, with the bacteria in biofilms being the most difficult to control. High levels of biocides are used and this has detrimental effects on the environment, as biocides are toxic to humans, being carcinogenic, corrosive and producing intolerable odours. Electrochemical activation technology provides an alternative way of controlling microorganisms. ECA water was shown in other countries to have antimicrobial properties. Anolyte, the positively charged solution is benign to fumes and corrosion caused by other biocides. Since anolyte is eco-friendly and present no problems to the environment, it provides a good alternative for controlling microorganisms instead of chemical control. The minimum inhibitory concentration (MIC) of anolyte and its antimicrobial properties against different microorganisms in suspension was evaluated. The I: 1 0 and neat anolyte gave a 100% kill of all organisms tested while 1 :20 dilution gave variable killing percentages ranging from 31 % to 100%. Minimum inhibitory concentration was found to be 20% for most Gram positives and 50% for most Gram negatives. Anolyte did have some antimicrobial properties with MIC differing amongst different organisms. Biofilm control using different concentrations of anolyte and sodium hypochlorite was evaluated. Neat and 1: 10 anolyte removed biofilm while 1: 100 did not have effect on biofilm. The 100 and 300 ppm sodium hypochlorite were effective in removing the biofilm while 10, 25 and 50 ppm could not remove it. Hand wash trials and hospital disinfection using anolyte resulted in a decrease in the number of cfu/25cm3 after treatment. Effective disinfection of hands and hospital equipment was achieved. Different surfaces in a milking parlour were treated with anolyte to test its suitability to disinfect a milking parlour. High numbers of microorganisms and spreaders were observed from the plates before the surfaces were cleaned with anolyte. All spreaders were identified as sporeformers. Results were generally better when anolyte was used as a disinfectant, being able to eliminate spreaders as well. Treatment of chicken carcasses with anolyte to evaluate its effect on their shelf life was also tested. The number of colony forming units on chicken carcasses decreased after treatment of the carcasses with anolyte. Anolyte is therefore a naturally safe disinfectant that could be used in most fields including water distribution systems and industries for biofilm control, hospitals for minimising cross infection, food industries for increasing quality and shelf life of food and also in households for washing hands. / Dissertation (MSc (Microbiology))--University of Pretoria, 2006. / Microbiology and Plant Pathology / unrestricted

A common vector of nosocomial infections is Pseudomonas aeruginosa. This opportunistic pathogen is resistant against different classes of antibiotics as well as against biocides. Some P. aeruginosa strains are able to form biofilm. The biofilm formation on medical devices represent a common occurrence that can lead to serious illness and death. Bacteria in biofilms are more resistant than their planktonic counterparts. Therefore it is important to find disinfectants that will be effective also against biofilm. Bactericidal efficacy of four disinfectants has been evaluated on biofilm and on planktonic forms of P. aeruginosa.

Bacterial biofilms are 1,000 times harder to kill than planktonic bacteria. Spores are also harder to kill compared to vegetative cells. We developed a rapid model for establishing dry surface bacterial biofilms for disinfectant efficacy testing and challenged them with seven EPA-registered disinfectants. We also demonstrated that during the disinfection of surfaces contaminated with bacterial spores, disinfectant wipes may transfer spores from contaminated to uncontaminated surfaces.

The objective of this study was to investigate the differences in survival of L. monocytogenes EGD (Bug600) (serotype 1/2a) in various disinfectants and essential oils after sublethal heat stress at 48°C for 60 min. The survival of heat stressed L. monocytogenes cells was decreased in lethal acid (HCl or H3PO4 pH 2.5), lethal oxidative stress (H2O2 1000 ppm) and lethal quaternary ammonium compounds (QAC 2.5-3.5 ppm) compared to non-stressed control cells. By contrast, the survival of heat stressed L. monocytogenes cells was higher in lethal alkali (NaOH or KOH pH 12) than the control cells. Also, the survival of heat stressed L. monocytogenes cells was higher in lethal carvacrol (428 ppm) and bay oil (1100 ppm) but was decreased in lethal red thyme oil (300 pm) compared to control. These findings indicate that the heat stressed cells of L. monocytogenes are not easily killed by alkali-based disinfectants and essential oils containing carvacrol and bay oil. Therefore, disinfectants and essential treatments should be carefully considered when heat stressed cells of L. monocytogenes may be present.

According to USDA-FSIS reports, L. monocytogenes and Salmonella are two important foodborne pathogens that are prevalent throughout catfish environment. Channel catfish (Ictalurus punctatus) is the most important aquaculture species in the United States accounting for more than 60% of its aquaculture production. The objectives of this study were to determine the effect of strain, temperature concentration on the growth, survival and biofilm formation of L. monocytogenes and Salmonella using catfish mucus extract on different food-contact surfaces. Growth and survival of L. monocytogenes and Salmonella was greater at the higher concentration of mucus extract at both 10°C and 22°C. In 15 micrograms/ml catfish mucus extract L. monocytogenes and Salmonella counts increased to 4.5 log CFU/ml after 72 h at 10°C and 5-7 log CFU/ml counts after 32-48 h at 22°C. In 375 micrograms/ml catfish mucus extract L. monocytogenes and Salmonella counts increased to 6-7 log CFU/ml counts after 72 h at 10°C and 8-9 log CFU/ml counts after 32-48 h at 22°C. L. monocytogenes and Salmonella were able to grow and survive for more than 63 days with at least 4-6 log CFU/ml at 10°C and 6-8 log CFU/ml in 375 micrograms/ml and 15 micrograms/ml of catfish mucus extract respectively. No differences (P > 0.05) among L. monocytogenes and Salmonella strains were observed to form biofilms in the presence catfish mucus extract on the stainless steel surface. The biofilm formation by L. monocytogenes and Salmonella in catfish mucus extract was less (P < 0.05) on buna-n rubber when compared to stainless steel, polyethylene and polyurethane surfaces. Therefore, the findings in this study show that catfish mucus promotes L. monocytogenes and Salmonella to grow and subsequently form biofilms on different food-contact surfaces also promotes growth and survival of these pathogens for longer period of time in catfish processing industries.

Encephalitozoon cuniculi is a zoonotic protozoan parasite in the phylum Microspora that has been shown to naturally infect several host species, including humans, rabbits and dogs. Currently, serological diagnosis of infection is made using the immunofluorescense assay (IFA) or enzyme-linked immunosorbent assay (ELISA). Although these methods are sensitive and reliable, there are several drawbacks to both tests. Cross-reactivity between other Encephalitozoon species is common, and specialized equipment is required for IFA and ELISA. Most wildlife species are unable to be tested using these methods, because species-specific antibodies are required. One goal of this work was to develop a new serological test for diagnosing E. cuniculi infection that would be more practical for use in small veterinary and medical clinics. The effectiveness of the agglutination test was examined in CD-1 and C3H/He mice infected with E. cuniculi or one of 2 other Encephalitozoon species. The results indicate that the agglutination test is 86% sensitive and 98% specific for E. cuniculi, with limited cross-reactivity to E. intestinalis. The test is fast and easy to conduct, and requires no specialized equipment or species-specific antibodies. Recent reports of microsporidial DNA in crop irrigation waters suggest that unpasteurized juice products may be contaminated with E. cuniculi. High pressure processing (HPP) is an effective means of eliminating bacteria and extending the shelf life of products while maintaining the sensory features of food and beverages. The effect of HPP on the in vitro infectivity of E. cuniculi spores was examined. Spores were exposed to between 140 and 550 MPa for 1 min, and then spores were loaded onto cell culture flasks or were kept for examination by transmission electron microscopy (TEM). Spores treated with between 200 and 275 MPa showed reduction in infectivity. Following treatment of 345 MPa or more, spores were unable to infect host cells. No morphologic changes were observed in pressure-treated spores using TEM. The effect of disinfectants on in vitro infectivity of E. cuniculi spores was also examined. Spores of E. cuniculi were exposed to several dilutions of commercial bleach, HiTor and Roccal, and 70% ethanol for 10 minutes and then loaded onto Hs68 cells. The results of this study showed that all concentrations of disinfectants tested were lethal to E. cuniculi spores. Encephalitozoon cuniculi spores are more sensitive to disinfectants than are coccidian oocysts and other parasite cysts. / Master of Science