Abstract
BackgroundChronic lung infection with the bacterium Pseudomonas aeruginosa is one of the hallmarks of cystic fibrosis (CF) and is associated with worsening lung function, increased hospitalisation and reduced life expectancy. A virulent clonal strain of P. aeruginosa (Australian epidemic strain I; AES-I) has been found to be widespread in CF patients in eastern Australia.MethodsSuppression subtractive hybridization (SSH) was employed to identify genetic sequences that are present in the AES-I strain but absent from the sequenced reference strain PAO1. We used PCR to evaluate the distribution of several of the AES-I loci amongst a collection of 188 P. aeruginosa isolates which was comprised of 35 AES-I isolates (as determined by PFGE), 78 non-AES-I CF isolates including other epidemic CF strains as well as 69 P. aeruginosa isolates from other clinical and environmental sources.ResultsWe have identified a unique AES-I genetic locus that is present in all 35 AES-I isolates tested and not present in any of the other 153 P. aeruginosa strains examined. We have used this unique AES-I locus to develop a diagnostic PCR and a real-time PCR assay to detect the presence of P. aeruginosa and AES-I in patient sputum samples.ConclusionsWe have developed diagnostic PCR assays that are 100% sensitive and 100% specific for the P. aeruginosa strain AES-I. We have also shown that Whatman FTA® Elute cards may be used with PCR-based assays to rapidly detect the presence of P. aeruginosa strains in CF sputum.
Highlights
Chronic lung infection with the bacterium Pseudomonas aeruginosa is one of the hallmarks of cystic fibrosis (CF) and is associated with worsening lung function, increased hospitalisation and reduced life expectancy
We reported a case of cross-infection of a patient with non-CF bronchiectasis that resulted in significant clinical deterioration [12]
BLASTX analysis of the 12 unique Australian epidemic strain-I (AES-I) suppression subtractive hybridization (SSH) sequences indicated that 3 (HW15, HW16, HW21) were 100% identical to genes located within the P. aeruginosa O6 antigen LPS biosynthetic gene cluster [25] and identified AES-I as belonging to the O6 serotype, a widespread serotype and the same as the LES and Midlands epidemic strains [13]
Summary
Chronic lung infection with the bacterium Pseudomonas aeruginosa is one of the hallmarks of cystic fibrosis (CF) and is associated with worsening lung function, increased hospitalisation and reduced life expectancy. Ensuing surveillance of the CF clinic in 1999 found that 55% of those infected with P. aeruginosa had an identical or closely related strain to that of the five young children [10]. This strain appeared to show increased virulence as it was associated with increased hospitalisation and poorer pulmonary function amongst. Three years after the introduction of these measures, we noted a significant decrease in the incidence and prevalence of AES-I infection [14] This observation strongly supports the notion that the AES-I is transmitted by cross-infection between patients during hospital and clinic visits and highlights the success of cohorting strategies in limiting AES-I transmission
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