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J Clin Virol. 2008 Jan;41(1):25-8. Epub 2007 Dec 4.

Detection of human influenza A (H1N1) and B strains with reduced sensitivity to neuraminidase inhibitors.

Author information

1
Virologie et Pathologie humaine, CNRS FRE 3011, Université Lyon 1, 7 rue Guillaume Paradin, 69372 Lyon cedex 08, France. vanessa.escuret@chu-lyon.fr <vanessa.escuret@chu-lyon.fr>

Abstract

BACKGROUND:

Neuraminidase inhibitors (NAIs) have been used since 2005 in France.

OBJECTIVE:

Influenza viruses isolated in hospital and community cases in winter 2005-2006 were evaluated for their sensitivity to NAIs.

STUDY DESIGN:

Isolates were tested in duplicate with a fluorescence-based neuraminidase assay. The IC50 for oseltamivir or zanamivir was calculated for each strain. Mean IC50 (+/-S.D.) are expressed in nM. Viruses with IC50 superior or very superior to the upper limit (mean IC50+2.5 S.D.) were considered as outliers or resistant viruses, respectively. HA and NA genes for outliers, resistant strains and for a few sensitive strains were sequenced.

RESULTS:

Out of 225 B isolates, one was found resistant to both oseltamivir and zanamivir with a D197Y mutation in NA and eight isolates were outliers for oseltamivir and/or zanamivir. Out of 151 A (H1N1) isolates, one was found resistant to oseltamivir but sensitive to zanamivir with a H275Y mutation in NA, two isolates were resistant to zanamivir and three isolates were outliers for oseltamivir and/or zanamivir. New mutations were detected in outliers compared to sensitive viruses.

CONCLUSION:

Resistant influenza strains to NAIs are circulating at a stable and low level of 1% since the introduction of NAIs in clinical practice.

PMID:
18055253
DOI:
10.1016/j.jcv.2007.10.019
[Indexed for MEDLINE]

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