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Amantadine-resistant influenza A virus in Taiwan
1School of Medical Technology, Chang Gung University, Clinical Virology Laboratory, Chang Gung Memorial Hospital, Tao-Yuan.
Background And Purpose:
Amantadine and rimantadine have been used for treatment and prophylaxis of influenza A virus infection. We examined the amantadine susceptibility of field isolates of influenza A virus in Taiwan from 1996 to 1998 to monitor the presence of resistant strains.
Methods:
Eighty-four field isolates of influenza A virus were examined for resistance to amantadine by plaque inhibition assay. Virus isolates with amantadine 50% inhibitory concentrations (IC50) greater than 0.9 microgram were chosen for sequence analysis of the M gene that is the molecular target for amantadine/rimantadine. Reverse transcription-polymerase chain reaction (RT-PCR) was used to amplify the viral RNA. RT-PCR products were examined and purified by agarose gel electrophoresis for further sequence analysis. The Genetics Computer Group Sequence Analysis Package and the neighbor-joining method listed in the Molecular Evolutionary Genetic Analysis package were used for phylogenetic analysis.
Results:
One field strain was amantadine resistant (IC50 > 10 micrograms/mL), with a mutation (position 31, serine to asparagine) in the M2 protein. The resistant virus was isolated from a non-immunocompromised child without a history of amantadine/rimantadine treatment. None of the family members reported previous exposure to amantadine/rimantadine.
Conclusions:
In this series, amantadine-resistant influenza A (H1N1) virus was isolated from a non-immunocompromised Taiwanese child without a known history of exposure to this drug. Resistant field isolates were rare. Due to the increasing use of amantadine/rimantadine in Taiwan, continued surveillance for amantadine/rimantadine-resistant influenza A viruses is warranted.
Insights
Amantadine-resistant influenza A virus was detected in Taiwan, highlighting the need for ongoing surveillance. This finding is crucial for managing influenza A infections and guiding antiviral drug use.
Area of Science:
- Virology
- Antimicrobial Resistance
- Public Health
Background:
- Amantadine and rimantadine are antivirals used for influenza A treatment and prophylaxis.
- Monitoring antiviral resistance is essential for effective disease management.
Purpose of the Study:
- To assess amantadine susceptibility in Taiwanese influenza A virus field isolates from 1996-1998.
- To identify and characterize amantadine-resistant influenza A strains.
Main Methods:
- Plaque inhibition assay to determine amantadine 50% inhibitory concentrations (IC50).
- Sequence analysis of the M gene in resistant isolates.
- Reverse transcription-polymerase chain reaction (RT-PCR) for viral RNA amplification.
- Phylogenetic analysis using established bioinformatics packages.
Main Results:
- One amantadine-resistant influenza A strain (IC50 > 10 µg/mL) was identified.
- The resistant strain had a mutation (Ser31Asn) in the M2 protein.
- The resistant virus was isolated from a child with no prior amantadine/rimantadine exposure.
Conclusions:
- Amantadine-resistant influenza A (H1N1) virus was found in a Taiwanese child without known drug exposure.
- Resistant field isolates were infrequent during the study period.
- Continued surveillance for amantadine/rimantadine resistance in influenza A is recommended due to increasing drug usage.