How different is the proteome of the extended spectrum ß-lactamase producing Escherichia coli strains from seagulls of the Berlengas natural reserve of Portugal?

UNLABELLED: ß-Lactam antibiotics like cefotaxime are the most commonly used antibacterial agents. Escherichia coli strains 5A, 10A, 12A and 23B isolated from Seagulls feces, are cefotaxime-resistant strains that produces extended-spectrum beta-lactamases. Bacterial resistance to these antibiotics occurs predominantly through structural modification on the penicillin-binding proteins and enzymatic inactivation by extended-spectrum ß-lactamases. Using classical proteomic techniques (2D-GE) coupled to mass spectrometry and bioinformatics extended analysis, in this study, we report several significant differences in cytoplasmic proteins expression when the strains were submitted to antibiotic stress and when the resistant strains were compared with a non-resistant strain. A total of 79 differentially expressed spots were collected for protein identification. Significant level of expression was found in antibiotic resistant proteins like ß-lactamase CTX-M-1 and TEM and also in proteins related with oxidative stress. This approach might help us understand which pathways form barriers for antibiotics, another possible new pathways involved in antibiotic resistance to devise appropriate strategies for their control already recognized by the World Health Organization and the European Commission. BIOLOGICAL SIGNIFICANCE: This study highlights the protein differences when a resistant strain is under antibiotic pressure and how different can be a sensible and resistant strain at the protein level. This survey might help us to understand the specifics barriers for antibiotics and which pathways are involved in its resistance crosswise the wildlife.

Response of Listeria monocytogenes to liquid smoke.

AIMS: To investigate the effect of liquid smoke on growth, survival, proteomic pattern and haemolytic potential of Listeria monocytogenes. METHODS AND RESULTS: Growth and survival curves were recorded in brain-heart infusion broth supplemented with three concentrations of liquid smoke. L. monocytogenes growth was inhibited in the presence of 15 microg ml(-1) phenol while a rapid decrease in cell viability occurred in the presence of 30 microg ml(-1) phenol. The proteome of L. monocytogenes cytosoluble proteins was slightly modified after 2-h incubation with 30 microg ml(-1) phenol but no protein already characterized in response to other known stresses was induced, except the protease ClpP. Liquid smoke inhibited the haemolytic potential without affecting hly gene expression, showing a potential inhibition of protein activity or stability. CONCLUSIONS: The presence of liquid smoke in a rich medium strongly affected growth and survival of L. monocytogenes. Brief smoke stress affected the metabolic pathways and inhibited the haemolytic activity of L. monocytogenes. SIGNIFICANCE AND IMPACT OF STUDY: This study is a first step in the investigation of the influence of a smoked product on L. monocytogenes strains.