M025: MOLECULAR MICROBIAL ECOLOGY STUDIES ON PSEUDOMONAS AERUGINOSA
ISOLATES FROM CYSTIC FIBROSIS PATIENTS: THE ROLE OF IRON IN THE
REGULATION OF VIRULENCE RELATED FACTORS
C. Adams*, Declan Hickey*, Mary Morris-Quinn*,B. Lucey+,
M. Lynch+, C. Short**, B.Cryan+, J.G.B. Watson** and F. O'Gara*.
Microbiology Dept., University College, Cork, Ireland. +Microbiology
Dept., Regional Hospital, Cork, Ireland. **Paediatrics Dept.,
Regional Hospital, Cork, Ireland.
Pseudomonas aeruginosa, the most important pathogen isolated from the respiratory tract of cystic fibrosis (CF) patients, appears to be refractory to antibiotic therapy and has the ability produce a range of potential virulence determinants. To date, the epidemiology and mechanisms of colonisation, persistence and pathogenicity of P. aeruginosa infection in CF patients remain unclear. An arbitrarily primed PCR (AP-PCR) technique was used to generate genomic fingerprints of P. aeruginosa isolates from a population of patients attending the CF clinic at the Cork University Hospital. These strains were grouped on the basis of the genomic fingerprints obtained. To date >16 groups have been identified with a predominance of 2-3 main groups. P. aeruginosa strains isolated from various environmental locations have also been typed using this AP-PCR technique and a strain identical to a CF clinical isolate has been identified. These results suggest that both cross infection between patients and direct infection from the environment is possible. Once infected, the competitive growth and survival of bacteria in a host environment requires the organism to sense its environment appropriately and respond with co-ordinate alterations in the expression of virulence related genes. Since free iron is extremely limited in the mammalian host environment the acquisition of iron by the invading organism is a major environmental factor essential for bacterial survival and pathogenicity. Pseudomonas aeruginosa isolates from a population of CF patients have been analysed for the production and regulation of iron responsive virulence factors, including protease, elastase and siderophore. The P. aeruginosa isolates, representing diverse genetic groups based on fingerprint analysis, differed in the expression and regulation of these potential virulence traits. Molecular microbial ecology studies are aimed at establishing if there is any correlation between the expression of these traits and the survival and pathogenicity of Pseudomonas aeruginosa in the CF lung.