iBB

Burkholderia cepacia complex (Bcc) bacteria can adapt to the hostile lung environment of cystic fibrosis (CF) patients leading to chronic infection. While it is unclear why different Bcc species/strains differ in their pathogenic potential, lipopolysaccharides (LPS) are considered a major virulence factor. The O-antigen (OAg) component of LPS is believed to modulate host-pathogen interaction and to be under selective pressure. A study recently published in Frontiers in Cellular and Infection Microbiology was performed to understand whether OAg loss can be considered a general phenomenon that affects immune evasion favoring chronic infection. A systematic retrospective and longitudinal screening was performed based on a collection of 357 isolates involving 21 different Bcc strains of six/seven Bcc species/lineages isolated from CF patients. These isolates were recovered from 1995 to 2016 from 19 CF patients under surveillance at Hospital de Santa Maria over the duration of chronic infection (ranging from 1.2 to 15.2 years). B. cenocepacia and B. multivorans showed a tendency to lose the OAg along chronic infection, with the switch frequency increasing with the duration of infection and level of lung function deterioration. For the first time, this study shows that the rarely found species B. cepacia and B. contaminans keep the OAg even during infections that last for 10 and 15 years. This research, coordinated by Prof. Isabel Sá-Correia and with the BIOTECnico PhD student Amir Hassan as first author, reinforces the relevance attributed to OAg-expression switch suggesting marked differences in the various Bcc species.

During chronic respiratory infections of cystic fibrosis (CF) patients, bacteria adaptively evolve in response to the nutritional and immune environment. A research paper from iBB-BSRG researchers, just published in Frontiers in Microbiology (part of the Research Topic: Evolutionary Mechanisms of Infectious Diseases), contributes to the understanding of shared and species specific evolutionary patterns of B. cenocepacia and B. multivorans evolving in the same CF lung environment. Results support the idea that positive selection might be driven by the action of the host immune system, antibiotic therapy and low oxygen and iron concentrations. This research work, coordinated by Prof. Isabel Sá-Correia, results from the PhD thesis in Biotechnology and Biosciences (BIOTECnico program) of A. Amir Hassan. Dr. AA Hassan is currently working at the Laboratory of Microbiology, Department of Biochemistry and Microbiology, Ghent University, Belgium.

Bacterial cell envelope plays a central role in cell physiology and the alteration of surface properties can implicate the variation of phenotypes that play a crucial role in the pathogenesis of infectious diseases, such as the resistance to antibiotics and other environmental stresses, biofilm formation, persistence of infection. However, the influence that Burkholderia cenocepacia adaptive evolution during long-term respiratory infection in cystic fibrosis (CF) patients has on cell wall morphology and mechanical properties is poorly understood. This study, just published in the journal Scientific Reports, has examined cell wall morphology and mechanical properties of three sequential B. cenocepacia clonal variants by Atomic Force Microscopy (AFM). Results reinforce the concept of the occurrence of phenotypic variation and adaptive evolution during chronic infection, also at the level of cell size, form, envelope topography and physical properties. This research work, coordinated by Prof. Isabel Sá-Correia from iBB-BSRG and IST, was the result of a national collaboration with the team of Dr. Mário S. Rodrigues from BioISI, Faculty of Sciences, Universidade de Lisboa, having the IST PhD student of the BIOTECnico program Amir Hassan, from iBB-BSRG, as first author of the publication.