Identification by subtractive hybridization of a novel insertion element specific for two widespread Burkholderia cepacia genomovar III strains
Lixia Liu1, Theodore Spilker, Tom Coenye
1Department of Pediatrics and Communicable Diseases, University of Michigan Medical School, Ann Arbor, Michigan 48109-0646, USA.
Abstract:
Species of the Burkholderia cepacia complex cause chronic and life-threatening infections in persons with cystic fibrosis. Epidemic strains infect multiple patients, reside primarily in genomovar III, and have an apparent enhanced capacity for human infection and/or interpatient transmission. By using subtractive hybridization, a novel insertion element, designated IS1363, was identified in epidemic strain PHDC, known to infect many cystic fibrosis patients in the mid-Atlantic region of the United States. IS1363 was also found in most isolates of the ET12 lineage, responsible for infecting large numbers of patients in Ontario, Canada, and the United Kingdom. Southern blot analysis demonstrated that whereas multiple copies of IS1363 were present in strain PHDC, only one copy was present in ET12 isolates. IS1363 was used to probe a collection of 943 B. cepacia complex isolates, representing all nine genomovars, recovered from 761 cystic fibrosis patients or the natural environment. IS1363 was not found in other genomovar III strains and, with the exception of B. ambifaria, was absent from other B. cepacia complex species. Genotyping analyses of all IS1363-positive isolates demonstrated that strain PHDC was more widely distributed in the United States than previously appreciated; 212 cystic fibrosis patients in 24 states were identified as being infected with PHDC.
Insights
A novel insertion element, IS1363, was identified in epidemic Burkholderia cepacia complex strains causing cystic fibrosis infections. This element helps track the spread of these dangerous bacteria in patients.
Area of Science:
- Microbiology
- Genetics
- Infectious Diseases
Background:
- The Burkholderia cepacia complex (BCC) comprises species responsible for severe, chronic infections in cystic fibrosis (CF) patients.
- Epidemic BCC strains, often from genomovar III, exhibit increased human infectivity and transmission capabilities.
- Understanding the genetic basis of epidemic BCC strains is crucial for infection control.
Purpose of the Study:
- To identify novel genetic elements associated with epidemic BCC strains.
- To investigate the prevalence and distribution of identified elements in BCC isolates from CF patients and environmental sources.
- To utilize genetic markers for improved epidemiological tracking of BCC infections.
Main Methods:
- Subtractive hybridization was employed to identify unique DNA sequences in epidemic BCC strain PHDC.
- Southern blot analysis was used to determine the copy number of the insertion element in different strains.
- IS1363 was used as a probe to screen a large collection of BCC isolates (n=943) from CF patients and environmental samples.
- Genotyping was performed on IS1363-positive isolates to assess geographical distribution.
Main Results:
- A novel insertion element, IS1363, was identified in epidemic BCC strain PHDC.
- IS1363 was also detected in the ET12 lineage, another significant epidemic BCC group.
- Multiple copies of IS1363 were found in strain PHDC, while only one copy was present in ET12 isolates.
- IS1363 was largely absent from other BCC genomovar III strains and species, except for B. ambifaria.
- IS1363-positive isolates revealed a wider distribution of strain PHDC across 24 US states, infecting 212 CF patients.
Conclusions:
- IS1363 is a valuable genetic marker for identifying and tracking specific epidemic BCC strains, particularly PHDC and ET12.
- The widespread presence of IS1363 in PHDC highlights its utility in understanding the epidemiology of BCC infections in CF patients.
- Further research into IS1363's role could provide insights into BCC pathogenicity and transmission dynamics.
