CONICET | Buscador de Institutos y Recursos Humanos

Burkholderia cepacia complex (Bcc) species are opportunistic human pathogens capable of causing chronic and often severe respiratory tract infections in cystic fibrosis (CF) patients. The excessive production of thick and sticky mucus in CF patients clogs their airways and provides a favourable environment for bacterial infection. This environment, characterized by a heterogeneous distribution of nutrients and the presence of host immune response agents, and therapeutic antibiotics, makes bacteria face continuous adaptive challenges. For P. aeruginosa both the genetic adaptations and phenotypic variation that occur during long-term CF lung infection are very well characterized (conversion to the mucoid phenotype, inactivation of quorum sensing functions, resistance to antibiotics, alterations in lipopolysaccharide (LPS), loss of type III secretion system and a rise in the mutation rate leading to a hypermutator phenotype)2. In contrast, the behavior of Bcc bacterial due to their persistence in CF lungs is mostly unknown. In our laboratory a CF population comprising 95 patients and 155 isolates belonging to different CF reference centers and hospitals has been studied since 2004, when a Bcc outbreak occurred and the incidence of this group of bacteria definitely increased in Argentina. Although in 47 % of the studied patients Bcc colonization was transient, the remaining 53 % CF population acquired a chronic infection, which in approximately half the cases involved a single species colonization. We here aim to show the use of FT-IR spectroscopy as a powerful tool to contribute in the understanding of several aspects associated to the adaptation of Bcc bacteria to persist in the hostile lung environment of CF patients and produce chronic infections. Over these 9 years of investigation we could establish that while the genotypic diversity of the whole the population -both isolates obtained for the new and the chronically infected CF patients- decreased the phenotypic diversity increased as indicated by a high number of FT-IR spectral types encountered in the last years of our surveillance. The analysis of the spectra of subsequent isolates obtained from the some patients along their chronic infection we could detect spectral changes associated to adaptations such as the loss of Type IV pili (evaluated by ), changes in the capability of accumulation polyhidroxibutirate (PHB) as carbon and energy storage material (1740, 1383, 1182, 1303, 1182 and 1059), variations in the regions assigned to carbohydrate 1250-900 cm-1 which could be associated with an adaptative conversion form the mucoid to non-mucoid variants along the course of the chronic infection. Moreover the analysis of subsequent isolates retrive from CF patients chronically infected by B. cenocepacia showed changes in the intensity of in the spectral signals assigned to lipids (3000-2800 cm-1). This latter result is in agreement with previous observations reported for B. cenocepacia isolates recovered after 3,5 years of lung infections where alterations of membrane fatty acid composition, were observed. Thus, as FT¬-IR spectroscopy is sensitive to the presence of different cell components and/or virulence factors, it constitute a very powerful and rapid tool to analyze chemical modifications associates with phenotypic variations among the different isolates retrieved over long term infections. We have provided a significant insight into phenotypic variations which helped to elucidate the ?microbial evolution? associated to bacterial persistence and adaptation within chronic lung infection in CF patients. REFERENCES 1.Miñán et al., Analyst 134: 1138 ? 1148, 2009;. New York, 1992. 2.Smith, et al., Proc Natl Acad Sci USA 103: 8487?8492, 2006.. 3.Bosch et al., J Clin Microbiol 46: 2535?2546, 2008. 4.Couthinio et al. Infection and Imnunity , July 2011, p. 2950?2960