Uso de RMN no Estado Estacionário para Aumento de Sensibilidade de Análises Químicas.

bitstream/CNPDIA/10489/1/CT37_2000.pd

Comparative evaluation of coagulase-negative staphylococci (CoNS) adherence to acrylic by a static method and a parallel-plate flow dynamic method

The main goal of this work was to evaluate the adhesion to acrylic of several clinical strains of Staphylococcus epidermidis and Staphylococcus haemolyticus using both static and dynamic adhesion methods, and to compare the results obtained with these two methods. Adhesion was evaluated using the static slide method with different washing procedures, and the parallel plate flow chamber method. The extent of S. epidermidis adhesion, assessed by both methods, was greater than that of S. haemolyticus. The number of bacteria which adhered using the static method was lower than that using the dynamic method. It was found that the simple static method, when performed with an accurate washing procedure, can be as effective as the dynamic flow method for assessing differences in the adherence capacity of strains. Although the dynamic flow method yielded more overall information, its greater complexity and cost may not always justify its use for certain experimental comparisons. This investigation has shown that simple static adhesion methods, when performed accurately, can be used to evaluate differences in adhesion capacity.NIH - grant AI 46706.Fundação para a Ciência e a Tecnologia (FCT) – Programa Operacional “Ciência, Tecnologia, Inovação” (POCTI) - POCTI/ESP/42688/2001, grant SFRH/BD/8676/2002

Inhibition of adherence of coagulase-negative Staphylococci (CoNS) to acrylic by subinhibitory concentrations of antibiotics

CoNS are major nosocomial pathogens associated with infections of indwelling medical devices. The major virulence factor for these organisms is their ability to adhere to devices and form biofilms. Antibiotics interacting with the cell wall may influence bacterial adhesion by causing changes in the cell surface. These cell surface modifications may increase or decrease bacterial adherence to biomaterials. In this study the effect of sub-mic concentrations of cefazolin, vancomycin and dicloxacilin on adhesion to acrylic of several CoNS clinical isolates was determined. The results showed a minimal effect for vancomycin on reducing adhesion, although this antibiotic had a very low MIC value, and thus a high efficiency in killing bacteria in suspension. Cefazolin and dicloxacilin induced a higher inhibition of adhesion, reaching more than 60% for some strains, although being antibiotics that have a lower efficiency of killing bacteria in suspension. Combinations of the drugs were evaluated and a synergistic effect was observed. Use of antibiotics that inhibit adherence of CoNS to biomaterials may augment other treatment strategies for device-related infections

Differences in adhesion and biofilm formation of several clinical isolates of Staphylococcus epidermidis

Staphylococcus epidermidis and similar coagulase-negative staphylococci (CoNS) are now well established as major nosocomial pathogens associated with infections of indwelling medical devices. The major virulence factor of these organisms is mainly due to their ability to adhere to devices and form a biofilm.however, it is not known if adherence and biofilm formation are closely linked phenotypes for clinical isolates. since different clinical isolates of s. epidermidis would be expected to exhibit different phenotypic behaviours it is further expected that strains of s. epidermidis might have different abilities to adhere to synthetic surfaces and subsequently produce biofilms. in this study the initial adherence and subsequent biofilm formation properties of 9 clinical isolates of s. epidermidis along with biofilm+ and biofilm– control strains were assayed. the adherence results were interpreted in terms of the physico-chemical interaction established between the cells and the adhesion substratum as assessed by contact angle measurements.as expected, the clinical isolates exhibited different abilities to adhere to hydrophilic glass and to form biofilms. moreover, the strains that produced the highest amounts of biofilms were not the ones able to adhere to the largest extent and vice-versa. for example, the biofilm- control strain actually showed the highest level of initial adhesion capability and did not produce biofilm. these results indicate that high levels of initial adherence do not necessarily lead to strong biofilm formation and that some strains do not have a high initial adherence but can subsequently form a strong biofilm. these two aspects of the pathogenesis of medical device related-infection may need to be evaluated independently to ascertain the contribution of each to the virulence of cons causing device related infections

Metodologia de medida da difusividade térmica por RMN-CWFP.

bitstream/CNPDIA-2009-09/11832/1/CT72_2006.pd