RESUMEN
Pseudomonas aeruginosa causes chronic lung infections in people with cystic fibrosis (CF) and acute opportunistic infections in people without CF. Forty-two P. aeruginosa strains from a range of clinical and environmental sources were collated into a single reference strain panel to harmonise research on this diverse opportunistic pathogen. To facilitate further harmonized and comparable research on P. aeruginosa, we characterized the panel strains for growth rates, motility, virulence in the Galleria mellonella infection model, pyocyanin and alginate production, mucoid phenotype, LPS pattern, biofilm formation, urease activity, and antimicrobial and phage susceptibilities. Phenotypic diversity across the P. aeruginosa panel was apparent for all phenotypes examined, agreeing with the marked variability seen in this species. However, except for growth rate, the phenotypic diversity among strains from CF versus non-CF sources was comparable. CF strains were less virulent in the G. mellonella model than non-CF strains (P = 0.037). Transmissible CF strains generally lacked O-antigen, produced less pyocyanin and had low virulence in G. mellonella. Furthermore, in the three sets of sequential CF strains, virulence, O-antigen expression and pyocyanin production were higher in the earlier isolate compared to the isolate obtained later in infection. Overall, this full phenotypic characterization of the defined panel of P. aeruginosa strains increases our understanding of the virulence and pathogenesis of P. aeruginosa and may provide a valuable resource for the testing of novel therapies against this problematic pathogen.
Asunto(s)
Fibrosis Quística/complicaciones , Microbiología Ambiental , Fenotipo , Infecciones por Pseudomonas/microbiología , Pseudomonas aeruginosa/patogenicidad , Animales , Modelos Animales de Enfermedad , Humanos , Lepidópteros/microbiología , Dosificación Letal Mediana , Locomoción , Pseudomonas aeruginosa/clasificación , Pseudomonas aeruginosa/aislamiento & purificación , Pseudomonas aeruginosa/fisiología , Análisis de Supervivencia , VirulenciaRESUMEN
In a previous study, we described 2 forms of cyclic enterobacterial common antigen (ECACYC), a tetramer and a pentamer, from Escherichia coli O157. ECACYC is present in several representatives of the Enterobacteriaceae. To date, functional studies on ECACYC are sparse. Cyclic oligosaccharides in other bacteria, like the cyclic ß-glucans in Rhizobiaceae, represent microbe-associated molecular patterns involved in host-bacteria interaction. This observation determined the aim of the present study: to test whether the tetrameric and pentameric ECACYC from E. coli O157 can be recognised by host humoral and cellular mechanisms. ELISA tests designed to compare the 2 ECACYC with the O157 lipopolysaccharide showed that both ECACYC were not recognised by polyclonal anti-O157 serum but were good ligands for mannan-binding lectin. The lectin had a higher affinity for the tetramer than the pentamer. ECACYC deposited more C3b than did the lipopolysaccharide. To examine the interactions with human circulating neutrophils, the antigens were loaded onto fluorescent latex beads and applied in a phagocytosis experiment. Spheres coated with the 2 ECACYC occasionally adhered to phagocyte surfaces but, unlike O157-loaded spheres, failed to induce free-radical release. The results show that the 2 ECACYC represent microbe-associated molecular patterns recognised by host humoral non-self-recognition mechanisms.
Asunto(s)
Antígenos Bacterianos/aislamiento & purificación , Escherichia coli O157/inmunología , Fagocitosis , Animales , Antígenos Bacterianos/química , Antígenos Bacterianos/metabolismo , Ensayo de Inmunoadsorción Enzimática/métodos , Radicales Libres/metabolismo , Interacciones Huésped-Patógeno , Humanos , Sueros Inmunes/inmunología , Ligandos , Lipopolisacáridos/química , Lipopolisacáridos/inmunología , Lectina de Unión a Manosa/metabolismo , Microesferas , Neutrófilos/inmunología , Neutrófilos/metabolismo , Fagocitos/inmunología , Fagocitos/metabolismo , beta-Glucanos/inmunología , beta-Glucanos/metabolismoRESUMEN
Humicola lutea 103 is a copper-tolerant fungal strain able to grow in the presence of 300 µg·mL(-1) Cu(2+) under submerged cultivation. To prevent the consequences of copper overload, microorganisms have evolved molecular mechanisms that regulate its uptake, intracellular traffic, storage, and efflux. In spite of this avoidance strategy, high heavy-metal concentrations caused distinct and widespread ultrastructural alterations in H. lutea. The mitochondria were the first and main target of the toxic action. The effect of copper on activities of the key enzymes (hexokinase, glucose-6-phosphate dehydrogenase, malate dehydrogenase, and isocitrate dehydrogenase) included in the 3 main metabolic pathways, glycolysis, pentose phosphate pathway, and tricarboxylic acid cycle, was investigated. High metal concentrations exhibited a dramatic negative effect on hexokinase, while the other 3 enzymes showed a significant and dose-dependent stimulation. On the basis of the present and previous results we concluded that the copper-induced oxidative stress plays an important role in the fungal tolerance to high Cu (2+) concentrations.