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Pseudomonas infection in CF
  1. ROB ROSEBY,
  2. JOHN MASSIE
  1. Department of Respiratory Medicine
  2. Royal Children's Hospital
  3. Parkville
  4. Melbourne
  5. Victoria 3052
  6. email: rosebyr{at}cryptic.rch.unimelb.edu.au
    1. S ELBORN
    1. Adult Cystic Fibrosis Centre
    2. Belfast City Hospital
    3. Belfast BT9 7AB
    4. UK
    5. email: stuart.elborn{at}bch.n-i.nhs.uk

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      Elborn et al 1 have attempted to address the important question of whether it is better to treat patients with cystic fibrosis (CF) who have chronicPseudomonas aeruginosa infection with intravenous antibiotics on the basis of symptoms or to treat them electively, and found no significant difference between their groups. They chose a particularly unwell subgroup of the CF population to study, and one might expect a policy of increasing from three symptomatic to four elective courses of intravenous antibiotics to make the least difference in such patients. We believe that patients who require 2–4 courses of intravenous antibiotics per year anyway are not those for whom this question of treatment is most pressing to answer. The benefit of elective treatment needs to be investigated in patients who have only recently acquired Pseudomonas aeruginosa, as per the Danish model.2 It is this group of patients for whom a recommendation of four intravenous treatments per year would be the greatest departure from current practice in most centres, and for whom strong evidence of benefit, including replication of the Danish results, is needed.

      Of great concern in the study by Elborn et al is the finding of an excess of deaths at five years in the group treated electively. This is not well accounted for by the authors. It is possible that the patients treated electively adopted a “sick role” with concomitant reduction in physical activity contributing to deterioration. In addition, patients admitted to hospital have increased opportunity for exposure to more virulent bacteria. In the study by Elborn et al the organisms were identified by their resistance patterns and were similar between the groups. However, research currently underway at our institution indicates that infection with certain genotypes ofP aeruginosa gives a worse prognosis than others, and sharing of such organisms among those frequently admitted may account for the difference in outcome at five years. We would suggest that it is important to study P aeruginosa genotypes to identify more accurately the possibility of cross infection being responsible for the worse outcome of the group treated electively.

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      author's reply We thank Drs Roseby and Massie for their comments on the British Thoracic Society study comparing elective and symptomatic antibiotic treatment in patients with cystic fibrosis (CF). They raise a number of issues which are important. The patients studied were not a particularly unwell group of CF patients and they represent a very average group of patients in their second and third decade. The main difference from the patients studied in Copenhagen is that treatment in their group was initiated early in the course of P aeruginosainfection while patients in the BTS study had been infected for some time. We agree that the patients who respond best to the intervention of elective intravenous antibiotics are likely to be those who have recently been infected with P aeruginosa. It would be useful for a further study to examine but, as most centres would have insufficient patients, this would need to be a study involving a considerable number of CF clinics.

      The issue of excess deaths is concerning. This study was designed to be as simple as possible for the participating physicians so unfortunately we do not have the organisms available to look for genotypes or virulence markers. However, there was no suggestion that the patients who died had any different in vitro antimicrobial resistance patterns from those of survivors.

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