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| Author(s): |
Vinícius Godoy Cerezer
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Faculdade de Medicina (FM/SBD) |
| Defense date: | 2013-05-24 |
| Examining board members: |
Carlos Alberto Moreira Filho;
Artur Figueiredo Delgado;
Ana Clara Guerrini Schenberg
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| Advisor: | Carlos Alberto Moreira Filho |
| Abstract | |
The genus Stenotrophomonas comprises twelve species of Gram- negative and non-fermentative bacteria, which can be found in the environment. The species S. maltophilia is the only one, until the present, that includes opportunistic pathogenic strains in humans. S. maltophilia gained clinical importance by being involved in an increasing number of infections in immunocompromissed patients and in NICUs, with high rates of morbidity and mortality. Environmental and clinical isolates of S. maltophilia share around 85% of genomic homology and this difference may be a consequence of adaptation to the different ecological niches where S. maltophilia can be found. Although infection and/or colonization by S. maltophilia occur mainly in the nosocomial environment, several studies have shown a growing number of community-acquired infections. In this study, nosocomial isolates and clinical strains of S. maltophilia were phenotyped and their phylogenetic profiles compared by using Multilocus Sequence Typing (MLST). In order to accomplish the MLST analysis the constitutive genes atpD, gapA, guaA, nuoD, ppsA, recA and rpoA were used. The resultant global phylogenetic profile showed high clonal variability, what correlates with the adaptability process of environmental S. maltophilia to other habitats. It was found that two clinical isolates subgroups of S. maltophilia with great phylogenetic homogeneity present intergroup recombination indicating the high permittivity to horizontal gene transfer, a mechanism involved in the acquisition of antibiotic resistance and expression of virulence factors. Moreover, for most of the clinical samples studied here, phylogenetic inferences can be made with the use of the gene ppsA only. Therefore, the sequencing of just one specific fragment of this gene would allow, in many cases, to determine whether the infection with S. maltophilia ? ? was caused by a strain already present in the nosocomial environment, or by bacteria introduced from the community in this environmental through the movement of people and materials. Finally, phenotyping data showed that even closely phylogenetic related nosocomial isolates and clinical strains do not share the same metabolic profile, thus indicating their community- acquired origin (AU) | |
| FAPESP's process: | 10/04115-9 - Phenotypic and phylogenetic characterization of clinical isolates of Stenotrophomonas |
| Grantee: | Vinícius Godoy Cerezer |
| Support Opportunities: | Scholarships in Brazil - Master |