SMANIA ANDREA
Congresos y reuniones científicas
Título:
Role of mismatch repair system deficiency in the evolution of Paeudomonas aeruginosa in chronic airway infections
Autor/es:
FELIZIANI S; QUIROGA R; MARVIG R; MOLIN S; SMANIA AM
Lugar:
Copenague
Reunión:
Congreso; 14th International Symposium of Microbial Ecology (ISME14); 2012
Resumen:
Pseudomonas aeruginosa (PA) is an opportunistic pathogen capable to cause chronic airway infections (CAI) in cystic fibrosis (CF) patients. In these infections, the same bacterial lineage persists throughout the life-time of the patients by using diverse adaptive mechanisms, such as biofilm growth and genetic diversification based on mutagenic events, leading to the emergence of multiple phenotypic variants. Hypermutability, mainly due to deficiency in DNA mismatch repair system (MRS), is highly selected and highly prevalent in CAI and it has been proposed as an additional adaptive strategy used by PA for persisting. However, the role of hypermutators in CAI persistence remains to be completely solved.
This work is aimed to study the impact of hypermutability on the phenotypic diversification and PA genome structure through many generations of persistence in CF patients. For that, cross-sectional and longitudinal analysis was performed by obtaining collections of isolates from two CF patients (CFA and CFD) infected by the same individual PA clone for more than 8 years. Among criteria for choosing these CF patients was the presence of hypermuator strains during the course of CAI. CFA collection was composed by two hypermutator isolates obtained in 2004 and 2007 and a population of 90 isolates obtained from a single sputum sample in 2010. CFD collection was composed by a nonmutator strain in 1991, two hypermutator strains in 1995 and 2002, and a population of 90 isolates obtained from a single sputum sample in 2011. Both collections were analyzed by using a combination of whole genome sequencing, BIOLOG metabolic profiling and phenotypic characterization. Both collections showed a high selection, prevalence and dominance of hypermutator strains. However, by analyzing the mutS and mutL genes, which codify for main MRS components, it was observed that different hypermutators clones hold diverse MRS mutations, even clones coexisting at the same time, suggesting the existence of emergence/extinction events during the evolutionary history and confirming a strong selective pressure for hypermutators in the CF environment. However, metabolic and phenotypic diversity analyses indicate that hypermutators and nonmutators clones follow convergent evolution into same adaptive traits. Whole genomic sequencing of each earliest isolate belonging from both patients as well as latest 11 hypermutator strains from CFA 2010 collection and 11 isolates from CFD 2011 collections (6 hypermutators, 3 nonmutators and 2 weak mutators) were performed. The de novo assembly and sequence analysis of these genomes are currently in progress. By comparative analyses of the genetic variation in hypermutators and nonmutators clones during CAI progress, we seek to build an evolutionary scenario that allows elucidating the role that hypermutators play in CAI persistance.