- Background: Transmission of Pseudomonas aeruginosa among cystic fibrosis patients attending health camps has been reported previously. Objectives: To determine the transmission of P. aeruginosa among CF patients during three winter camps in the Dead Sea region in southern Israel. Methods: Three consecutive CF patient groups were studied, each of which spent 3 weeks at the camp. The patients were segragated prior to camp attendance: patients who were not colonized with P aeruginosa constituted the first group, and colonized patients made up the two additional groups. Sputum cultures were obtained upon arrival, at mid-camp and on the last day. Environmental cultures were also obtained. Patients were separated during social activities and were requested to avoid social mingling. Isolates were analyzed by antibiotic susceptibility profile and by pulsed field gel electrophoresis. Results: Ninety isolates from 19 patients produced 28 different fingerprint patterns by PFGE. Isolates from two siblings and two patients from the same clinic displayed the same fingerprint pattern. These patients were already colonized with these organisms upon arrival. Two couples were formed during the camp, but PFGE showed no transmission of organisms. All other patients' isolates displayed unique fingerprint patterns and were distinguishable from those of other attendees, and none of the P aeruginosa-negative patients acquired P aeruginosa during camp attendance. Environmental cultures were negative for P aeruginosa. Conclusions: We were unable to demonstrate cross-infection of P aeruginosa among CF patients participating in health camps at the Dead Sea who were meticulously segregated.