Browsing by Author "Coelho, Pedro Barata"
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- Oxidative stress genes involved in the virulence-dependent susceptibility to antibiotics in Pseudomonas aeruginosaPublication . Coelho, Pedro Barata; Fernandes, Ruben; Silva, Carina; Oliveira, Marco; Veiga, Marlene; Sá, Sara; Vieira, André; Guedes, Carla; Baylina, PilarPseudomonas aeruginosa is a Gram-negative opportunistic pathogen which rarely causes disease in healthy people. P. aeruginosa, in particular strain PAO1 is also a biological model for studying virulence and bacterial social traits, such as quorum sensing, SOS response among other. Antibiotic response is dependent, among several other factors, to the response to environmental stress conditions. The present study aims to understand the role of 10 PAO1 oxidative gene mutants in the response to antibiotic stress in elastase, protease and pyocyanin-dependent virulence factors. PAO1 was stressed to several antibiotics (penicilins, cephalosporins, macrolides, and quinolones), and the virulence proteins were measured by means of spectroscopic methods. Viability was measured by means of Erythrosin B. PAO1 GGT, GLO1, RubA2, GSH A mutants were the most susceptible to the production of virulence-dependent factors.
- Phylogenetic Insights of β-lactam resistance of the CTX-M familyPublication . Coelho, Pedro Barata; Mendonça, Jacinta; Silva, Carina; Baylina, Pilar; Fernandes, Ruben; Guedes, CarlaBacterial resistance is a major public health concern, particularly against β-lactam antibiotics, one of the most widely used antibacterial drugs. The production of extended-spectrum β-lactamases (ESBLs) is the main defense mechanism found in Gram negative bacteria. Among all the ESBLs, the CTX-M enzymes appear as the most efficient in terms of diffusion in different epidemiological contexts, outnumbering the others. Originated in chromosomal genes of Klyvera spp., the blaCTX-M genes have become associated with mobile genetic elements, such as plasmids, that have mediated inter-replication and dissemination. CTX-M enzymes exhibit a striking plasticity, with a large number of allelic variants belonging to several sub-lineages, which can be associated with functional heterogeneity of clinical relevance. This observational analytical study provides an update of this family, currently with more than 200 variants described, from a phylogenetic, molecular and structural point of view through homology in amino acid sequences. There are currently 6 defined clusters (CTX-M-1, CTX-M-2, CTX-M-8, CTX-M-9, CTX-M-25 and CTX-M-151), with the domains CTX -M-1 and CTX-M-9 presenting subgroups, composed mainly of variants identified as hybrids between them (particularly between CTX-M-14 and CTX-M-15).
- The synergic effect of antibiotics is dependent of oxidative stress genes in Pseudomonas aeruginosaPublication . Fernandes, Rúben; Coelho, Pedro Barata; Guedes, Carla; Gojon, Frantz; Oliveira, Marco; Veiga, Marlene; Sá, Sara; Silva, Carina; Baylina, PilarPseudomonas aeruginosa is a Gram-negative opportunistic pathogen commonly found in Cystic fibrosis, infected wound of the diabetic foot among others. Clinical management of such infection depends deeply on the antibiotic therapy. Antibiotic response is dependent, among several other factors, to the response to host stress conditions, such as low-grade inflammation, metabolic conditions and oxidative stress and to social bacteria response such as quorum sensing and biofilm formation. P. aeruginosa, in particular strain PAO1 is also a biological model for studying bacterial biofilm formation. The present study aims to understand the antibiotic synergic response (ampicillin, ceftazidime, ciprofloxacin) in biofilm formation / degradation of 10 PAO1 oxidative gene mutants. Viability was measured by means of Erythrosin B and biofilm formation was measured by Crystal Violet assay. PAO1 GRLX, SEPHS 1, Rub A1, where the strains with a most pronounced biofilm formation and combination of ceftazidme::ciprofloxacin were most efficient in this biological model. The results are interesting, and although they are encouraging, they should be taken with caution.