Caracterização fenotípica de Cepas de Staphylococcus aureus isoladas de queijos ricota

This study aimed to isolate strains of Staphylococcus aureus in ricotta cheeses and to characterize them respecting phenotypic markers of lipolytic activity, and bacteriocin typing and resistance typing. For isolation, were acquired 11 samples of different brands of ricotta cheese sold in supermarkets in João Pessoa - Paraíba. Among the 41 strains, 82.9% proved positive lipase (Lip+) and 17.1%, negative lipase (Lip-). In relation to bacteriocin typing, 9.76% showed bacteriocin producing against a strain of Staphylococcus aureus isolated from surfaces processing food and 55% were susceptible to a strain of Staphylococcus aureus isolated from ricotta cheese. For resistance typing, 87.8% of strains were resistant to streptomycin, 26.59% to penicillin and 19.51% to erythromycin. None of the strains were resistant to tetracycline. Variability was observed between the minimal inhibitory concentrations (MIC), both in resistant strains as sensitive ones, so the variability showed more prevalent with penicillin (ranging from 0.015625 to 16 mg / mL) and the variability between strains of the same cheese. Only erythromycin-resistant strains were subjected to "D-test" to determine the type of resistance, of which all presented inductive resistant. From this results obtained, can conclude that although the phenotypes show an adaptive answer on related to the peculiarities of local environmental pressures, it is clear the importance of these genetic markers to discern new strains of S. aureus for those endemic, as well as to investigate possible epidemiological impacts and on food safety.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPESEste estudo teve como objetivo isolar cepas de Staphylococcus aureus de queijos ricota e caracterizá-las com relação a marcadores fenotípicos de atividade lipolítica, bacteriocinotipagem e resistotipagem. Para o isolamento, foram adquiridas 11 amostras de queijo ricota de diferentes marcas comercializadas em supermercados da cidade de João Pessoa-PB. Entre as 41 cepas isoladas, 82,9% revelaram-se lipase positiva (Lip+) e 17,1%, lipase negativa (Lip-). Com relação à bacteriocinotipagem, 9,76% mostraram-se produtoras de bacteriocinas frente a uma cepa de Staphylococcus aureus isolada de superfícies de processamento de alimentos e 55% mostraram-se sensíveis a uma cepa de Staphylococcus aureus isolada de queijo ricota. Para resistotipagem, 87,8% das cepas apresentaram-se resistentes a estreptomicina, 26,59% a penicilina e 19,51% a eritromicina. Nenhuma das cepas foi resistente a tetraciclina. Observou-se a variabilidade entre as Concentrações Inibitórias Mínimas, tanto em cepas resistentes como sensíveis, sendo tal variabilidade mais predominante com penicilina (variação de 0,015625 a 16 μg/mL), bem como a variabilidade entre cepas do mesmo queijo. Apenas cepas resistentes a eritromicina foram submetidas ao D-teste a fim de determinar o tipo de resistência, das quais todas as cepas mostraram-se com resistência indutiva. A partir dos resultados obtidos, pode-se concluir que embora os fenótipos revelem uma resposta adaptativa relacionada às peculiaridades das pressões ambientais locais, é evidente a importância destes marcadores genéticos a fim de se distinguir novas linhagens de S. aureus daquelas endêmicas, bem como investigar possíveis impactos epidemiológicos e na segurança alimentar

Potential impacts of climate change on biogeochemical functioning of Cerrado ecosystems

The Cerrado Domain comprises one of the most diverse savannas in the world and is undergoing a rapid loss of habitats due to changes in fire regimes and intense conversion of native areas to agriculture. We reviewed data on the biogeochemical functioning of Cerrado ecosystems and evaluated the potential impacts of regional climate changes. Variation in temperature extremes and in total amount of rainfall and altitude throughout the Cerrado determines marked differences in the composition of species. Cerrado ecosystems are controlled by interactions between water and nutrient availability. In general, nutrient cycles (N, P and base cations) are very conservative, while litter, microbial and plant biomass are important stocks. In terms of C cycling, root systems and especially the soil organic matter are the most important stocks. Typical cerrado ecosystems function as C sinks on an annual basis, although they work as source of C to the atmosphere close to the end of the dry season. Fire is an important factor altering stocks and fluxes of C and nutrients. Predicted changes in temperature, amount and distribution of precipitation vary according to Cerrado sub-regions with more marked changes in the northeastern part of the domain. Higher temperatures, decreases in rainfall with increase in length of the dry season could shift net ecosystem exchanges from C sink to source of C and might intensify burning, reducing nutrient stocks. Interactions between the heterogeneity in the composition and abundance of biological communities throughout the Cerrado Domain and current and future changes in land use make it difficult to project the impacts of future climate scenarios at different temporal and spatial scales and new modeling approaches are needed