Oseltamivir-induced resistant pandemic A/H1N1 influenza virus in a child with cystic fibrosis and Pseudomonas aeruginosa infection

Susanna Esposito, Claudio G. Molteni, Carla Colombo, Cristina Daleno, Valeria Daccò, Angie Lackenby, Nicola Principi*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

28 Citations (Scopus)


Background: Oseltamivir is considered the drug of choice for patients with pandemic influenza for whom drug treatment is recommended because adamantanes seem to be ineffective against pandemic A/H1N1 influenza virus and zanamivir is contraindicated in people with underlying respiratory conditions and difficult to administer in younger children. Objectives: To increase knowledge on oseltamivir resistance emergence in pandemic A/H1N1 influenza. Study design: Description of the case of an 8-year-old boy with cystic fibrosis and Pseudomonas aeruginosa infection in whom an oseltamivir-resistant pandemic A/H1N1 influenza virus was demonstrated. Results: On the basis of clinical and virological failure (nasopharyngeal secretions remained positive for pandemic A/H1N1 influenza virus and appearance of 275Y mutation in 100% virus population) on fifth day of treatment, oseltamivir was replaced by zanamivir inhalation (5 mg to be inhaled twice a day). This change was associated with a rapid improvement in the patient's general condition, respiratory findings and laboratory data (including disappearance of pandemic A/H1N1 influenza virus) in the absence of any adverse event. Conclusions: The emergence of oseltamivir-resistant strains is related to the administration of the drug, supporting the restriction of oseltamivir use to carefully defined high-risk groups. Infection due to pandemic virus with the H275Y mutation can be associated with a severe clinical course, supporting the systematic monitoring of antiviral susceptibility in pandemic influenza-positive high-risk patients whose influenza is not resolved by oseltamivir treatment. Zanamivir inhalation can be successfully used in patients with cystic fibrosis without causing adverse respiratory events, highlighting that the risks and benefits of this drug must be considered on a patient by patient basis.

Original languageEnglish
Pages (from-to)62-65
Number of pages4
JournalJournal of Clinical Virology
Issue number1
Publication statusPublished - May 2010

Bibliographical note

Funding Information:
The laboratory analyses were partially supported by a grant from the Italian Ministry of Health , Bando Giovani Ricercatori 2007.


  • Antiviral resistance
  • Children
  • Cystic fibrosis
  • Oseltamivir
  • Pandemic A/H1N1 influenza virus
  • Swine influenza


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