Opportunistic Pathogen Increasing in Cystic Fibrosis Patients

Burkholderia contaminans, a bacteria belonging to the Burkholderia cepacia complex (Bcc), is an opportunistic pathogen creating increasing concern for patients with cystic fibrosis in certain parts of the world. An opportunistic pathogen is an invading microorganism that finds its way into the body, sometimes with deadly force, when a person is in a weakened immune state because of another illness.

The finding published in the scientific journal PLOS One in an article titled “Understanding the Pathogenicity of Burkholderia contaminans, an Emerging Pathogen in Cystic Fibrosis,” is important because it can help scientists understand how the bacteria adapts to the lungs of cystic fibrosis patients and causes chronic lung infections. Ultimately, understanding the microorganism could lead to the development of better drugs to battle the infection.

The predominance of B. contaminans infections has increased in Spain, Argentina and other Ibero-American countries (Portuguese speaking nations within the Americas). Frequently found in respiratory samples of cystic fibrosis patients in those areas, the bacteria often leads to debilitating lung infections and high risk for developing deadly septicemia — but little more was known.

According to the study report: “This lack of information is worrisome in light of increasing proportion and even predominance of B. contaminans infections . . . indicating a large and characteristic geographic distribution of considerable concern.”

The team of researchers led by Dr. Pavel Drevinek of the Department of Medical Microbiology, 2nd Faculty of Medicine, Charles University and Motol University Hospital in Prague, performed a genome-wide comparative analysis of two isolates of the bactieria from the sputum and blood of a female cystic fibrosis patient in Argentina.

The research team found that samples of the bacteria isolated from the patient were genetically very different from one another; more specifically, the two isolates differed by more than 1,400 mutations.

Data showed that there were significant changes in the expression of bacterial genes involved in the virulence (severity), motility (movement), and chemotaxis (the process by which bacteria move by sensing their chemical environment). The scientists also detected changes in the expression of genes that are activated in stressful conditions for the bacteria such as low-oxygen, and that encode for stress-related proteins. Finally, the researchers observed some changes in the expression of genes responsible for the biosynthesis (process of new substances developing within the body) of anti-fungal and hemolytic (red-blood cell destroying) compounds.

Researchers found that there were two distinct types of B. contaminans that coexisted in the body of the patient and entered her bloodstream. They found that B. contaminans isolates can hold a high genomic diversity, potentially resulting in different bacterial virulence.

The report concluded: “We demonstrate the profound effect of DNA repair deficiency on the evolution of the B. contaminans genome in the stable environment of CF sputum. Observed mutational and transcriptional inactivation of Bcc virulence factors might help to unravel the mechanisms that drive the adaptation of this primarily environmental bacterium to the CF lung during chronic infection.”