Risk of Pseudomonas aeruginosa cross-colonisation in patients with cystic fibrosis within a holiday camp - a molecular-epidemiological study

Objective. A study on the molecular epidemiology of Pseudomonas aeruginosa in patients with cystic fibrosis (CF) from Germany (N=18) and Israel (N=12) is presented. The aim is to provide an answer to the question as to whethe r or not social contact outside the hospital environment involves a potenti al risk for person-to-person spread of this pathogen. Methods: Sputa from German and Israeli patients were obtained while these w ere attending a holiday camp in Israel. The sputum samples were analysed wi th regard to Pseudomonas aeruginosa. Strains dissimilar in macroscopic appe arance and/or antibiotic resistance patterns were genotyped using pulsed-fi eld gel electrophoresis after digestion of genomic DNA with restriction end onuclease Spel. The genetic polymorphism of DNA fragment patterns of all st rains (N=146) was studied for their overall relatedness using a fingerprint software system. Results: Most of the German patients (77.7%) were colonised persistently by a unique clonal type during the four-week screening period. Isolates obtai ned from Israeli patients displayed a very close clonal relationship and a higher antibiotic resistance as a result of preceding epidemic spread of ce rtain clones before the camp. Additionally, isolates showing identical PFGE patterns were demonstrated once in a single male Israeli patient and in on e female German patient, suggesting previous cross-colonisation. Conclusion: The occurrence of person-to-person spread through social contac t in patients with CF is supported by our findings, but remains a rare even t outside the hospital environment, provided appropriate hygienic measures are applied.