Staphylococcus aureus is the major pathogen causing intramammary infections in dairy cattle worldwide. Among the factors that contribute to its spread and infectious potential is the ability to overcome the mechanisms of antimicrobials activity. The present work investigated the antimicrobial resistance pattern and sensibility to bacteriocins produced by strains of Lactobacillus spp of 30 isolates of S. aureus from mastitis. From this, 29 are beta-lactamase producers. Eight isolates (26.6%) showed resistance to at least four antibiotics being considered multiresistent. All of them were mecA-positive. Otherwise, all isolates tested showed sensibility to at least one of the four bacteriocin producer strains. Due to the significant depletion of the efficacy of antimicrobials, pathogen growth inhibition by bacteriocins seems an alternative of biological control in infectious processes.

Avaliou-se o perfil de suscetibilidade bacteriana de diferentes sítios infecciosos frente aos antimicrobianos de eleição e determinaram-se o perfil de atividade in vitro e a concentração inibitória mínima (CIM) da azitromicina. Diferentes testes fenotípicos detectaram resistência à azitromicina em 45% de Staphylococcus spp. e 65% dos bastonetes Gram-negativo. A CIM50 para S. aureus foi 4,0μg/mL para S. intermedius 1,0μg/mL, Staphylococcus spp. coagulase-negativo >512μg/mL e bastonetes Gram-negativo 256μg/mL. Investigou-se, também, uma possível resistência cruzada entre oxacilina e azitromicina por meio da detecção do gene mecA em Staphylococcus spp. Foi possível detectar resistência à azitromicina em nove (15%) isolados de Staphylococcus spp. mecA positivo.

Antimicrobials susceptibility pattern of bacterial isolated from different sites of infection, in vitro azithromycin activity pattern, and its minimum inhibitory concentration (MIC) values were evaluated. Different phenotypic tests detected azithromycin resistance in 45% of Staphylococcus spp. and 65% of resistant Gram-negative rods. MIC50 was 4.0μg/mL for Staphylococcus aureus, 1.0μg/mL for S. intermedius, >512.0μg/mL for coagulase negative Staphylococcus, and 256.0μg/mL for Gram-negative rods. In addition, it was investigated the possible cross-resistance between oxacillin and azithromycin, by detection of mecA gen in Staphylococcus spp. Nine (15%) mecA-positive Staphylococcus spp. were also phenotypically resistant to azithromycin.

Aspectos cinético e termodinâmico da transferência de carga em polímeros condutores foram investigados. Um modelo de difusão restrita foi impregado para interpretar os dados obtidos por cronopotenciometria com pulso. Em filmes de poli 3-metiltiofeno, o coeficiente de difusão aparente diminuiu em função da espessura do filme mas ficou constante com a concentração eletrolítica. Em filmes finos, usando-se voltametria cíclica, caracterizou-se mudanças termodinâmicas, como em particular, a deconvolução das duas transferências eletrônicas envolvidas no processo. Usando-se um modelo nernstiano incluindo potenciais de interação, conseguiu-se descrever a reação para as duas etapas eletroquímicas. Finalmente, como esperado, uma correlação entre o raio iônico dos dopantes e o coeficiente de difusão aparente foi estabelecida em filmes de polipirrol.

The kinetics and thermodynamic aspects of charge transfer in conducting polymers were investigated. A restricted diffusion model was used to analyze kinetic data obtained from pulse-chronopotentiometric experiments. In poly 3-methylthiophene, the apparent diffusion coefficient decreased with the film thickness, whereas it remained constant with the electrolyte concentration. In thin films, thermodynamic changes were characterized by cyclic voltammetry, specifically, the deconvolution of the two electronic transfers involved in the process. Using a Nernstian model including interaction potentials, the two electrochemical steps were well described. Finally, as expected, a correlation between the ionic radius of the dopants and the apparent diffusion coefficient was established in polypyrrole films.