Oseltamivir-resistant pandemic (H1N1) 2009 virus, South Korea.
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ABSTRACT:
SUBMITTER: Yi H
PROVIDER: S-EPMC3294558 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:During May 2009-April 2010, we analyzed 692 samples of pandemic (H1N1) 2009 virus from patients in Mexico. We detected the H275Y substitution of the neuraminidase gene in a specimen from an infant with pandemic (H1N1) 2009 who was treated with oseltamivir. This virus was susceptible to zanamivir and resistant to adamantanes and oseltamivir.
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Project description:Resistance to oseltamivir was observed to influenza A pandemic (H1N1) 2009 virus strains, isolated from two patients in North Greece. Investigations showed resistant viruses with the neuraminidase (NA) 275Y genotypes. Pandemic A (H1N1) 2009 virus should be closely monitored for emergence of resistant variants.
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Project description:An oseltamivir-resistant influenza A pandemic (H1N1) 2009 virus evolved and emerged from zero to 52% of detectable virus within 48 hours of a patient's exposure to oseltamivir. Phylogenetic analysis and data gathered by pyrosequencing and cloning directly on clinical samples suggest that the mutant emerged de novo.
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Project description:Resistance to oseltamivir was observed in influenza A pandemic (H1N1) 2009 virus isolated from an untreated person in Hong Kong, China. Investigations showed a resistant virus with the neuraminidase (NA) 274Y genotype in quasi-species from a nasopharyngeal aspirate. Monitoring for the naturally occurring NA 274Y mutation in this virus is necessary.
| S-EPMC3044550 | biostudies-literature
Project description:Influenza viruses resistant to antiviral drugs emerge frequently. Not surprisingly, the widespread treatment in many countries of patients infected with 2009 pandemic influenza A (H1N1) viruses with the neuraminidase (NA) inhibitors oseltamivir and zanamivir has led to the emergence of pandemic strains resistant to these drugs. Sporadic cases of pandemic influenza have been associated with mutant viruses possessing a histidine-to-tyrosine substitution at position 274 (H274Y) in the NA, a mutation known to be responsible for oseltamivir resistance. Here, we characterized in vitro and in vivo properties of two pairs of oseltaimivir-sensitive and -resistant (possessing the NA H274Y substitution) 2009 H1N1 pandemic viruses isolated in different parts of the world. An in vitro NA inhibition assay confirmed that the NA H274Y substitution confers oseltamivir resistance to 2009 H1N1 pandemic viruses. In mouse lungs, we found no significant difference in replication between oseltamivir-sensitive and -resistant viruses. In the lungs of mice treated with oseltamivir or even zanamivir, 2009 H1N1 pandemic viruses with the NA H274Y substitution replicated efficiently. Pathological analysis revealed that the pathogenicities of the oseltamivir-resistant viruses were comparable to those of their oseltamivir-sensitive counterparts in ferrets. Further, the oseltamivir-resistant viruses transmitted between ferrets as efficiently as their oseltamivir-sensitive counterparts. Collectively, these data indicate that oseltamivir-resistant 2009 H1N1 pandemic viruses with the NA H274Y substitution were comparable to their oseltamivir-sensitive counterparts in their pathogenicity and transmissibility in animal models. Our findings highlight the possibility that NA H274Y-possessing oseltamivir-resistant 2009 H1N1 pandemic viruses could supersede oseltamivir-sensitive viruses, as occurred with seasonal H1N1 viruses.
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Project description:The neuraminidase (NA) inhibitor oseltamivir offers an important immediate option for the control of influenza, and its clinical use has increased substantially during the recent H1N1 pandemic. In view of the high prevalence of oseltamivir-resistant seasonal H1N1 influenza viruses in 2007-2008, there is an urgent need to characterize the transmissibility and fitness of oseltamivir-resistant H1N1/2009 viruses, although resistant variants have been isolated at a low rate. Here we studied the transmissibility of a closely matched pair of pandemic H1N1/2009 clinical isolates, one oseltamivir-sensitive and one resistant, in the ferret model. The resistant H275Y mutant was derived from a patient on oseltamivir prophylaxis and was the first oseltamivir-resistant isolate of the pandemic virus. Full genome sequencing revealed that the pair of viruses differed only at NA amino acid position 275. We found that the oseltamivir-resistant H1N1/2009 virus was not transmitted efficiently in ferrets via respiratory droplets (0/2), while it retained efficient transmission via direct contact (2/2). The sensitive H1N1/2009 virus was efficiently transmitted via both routes (2/2 and 1/2, respectively). The wild-type H1N1/2009 and the resistant mutant appeared to cause a similar disease course in ferrets without apparent attenuation of clinical signs. We compared viral fitness within the host by co-infecting a ferret with oseltamivir-sensitive and -resistant H1N1/2009 viruses and found that the resistant virus showed less growth capability (fitness). The NA of the resistant virus showed reduced substrate-binding affinity and catalytic activity in vitro and delayed initial growth in MDCK and MDCK-SIAT1 cells. These findings may in part explain its less efficient transmission. The fact that the oseltamivir-resistant H1N1/2009 virus retained efficient transmission through direct contact underlines the necessity of continuous monitoring of drug resistance and characterization of possible evolving viral proteins during the pandemic.
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Project description:BackgroundOseltamivir resistance among 2009 pandemic influenza A (H1N1) viruses (pH1N1) is rare. We investigated a cluster of oseltamivir-resistant pH1N1 infections in a hospital ward.MethodsWe reviewed patient records and infection control measures and interviewed health care personnel (HCP) and visitors. Oseltamivir-resistant pH1N1 infections were found with real-time reverse-transcription polymerase chain reaction and pyrosequencing for the H275Y neuraminidase (NA) mutation. We compared hemagglutinin (HA) sequences from clinical samples from the outbreak with those of other surveillance viruses.ResultsDuring the period 6-11 October 2009, 4 immunocompromised patients within a hematology-oncology ward exhibited symptoms of pH1N1 infection. The likely index patient became febrile 8 days after completing a course of oseltamivir; isolation was instituted 9 days after symptom onset. Three other case patients developed symptoms 1, 3, and 5 days after the index patient. Three case patients were located in adjacent rooms. HA and NA sequences from case patients were identical. Twelve HCP and 6 visitors reported influenza symptoms during the study period. No other pH1N1 isolates from the hospital or from throughout the state carried the H275Y mutation.ConclusionsGeographic proximity, temporal clustering, presence of H275Y mutation, and viral sequence homology confirmed nosocomial transmission of oseltamivir-resistant pH1N1. Diagnostic vigilance and prompt isolation may prevent nosocomial transmission of influenza.
| S-EPMC3307091 | biostudies-literature
Project description:The oseltamivir-resistant pandemic influenza virus A (2009 H1N1) with H275Y mutation in neuraminidase (NA) has been sporadically reported, and its wide spread remains a potential threat. Here we detected the uneven distribution of H275Y mutant virus in a patient who received a 21-day long-term administration of oseltamivir. Intrahost variation of the virus showed that the H275Y mutant virus was the predominant population in both nasopharynx and right lung, whereas the oseltamivir-sensitive virus comprised half the population in the left lung. By constructing minimum spanning trees, it is proposed that the H275Y mutant might be generated primarily in the nasopharynx, then spread to the right and left lungs.
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Project description:As the pandemic (H1N1) 2009 influenza virus continues to infect human populations globally, reports on epidemiologically linked animal infections are also on the rise. Since December 2009, pandemic (H1N1) 2009-like viruses have been isolated in pigs from different swine farms of South Korea. Genetic and phylogenetic analyses of viral segments demonstrated several events of human-to-swine transmission with no apparent signs of reassortment. These events were also supported by serological surveillance in pig sera collected from April to December, suggesting that reverse transmission probably started between June and July with a drastic increase in prevalence the following months. Although molecular characterization indicates that the swine isolates are generally stable, some viruses are genetically evolving, most notably in their surface proteins. Animal studies (ferrets and mice) reveal that swine pandemic isolates epitomize biological properties attributed to the currently circulating human pandemic viruses, including replication kinetics and efficient transmission, indicating their potential to return to circulation among humans. Overall, these results indicate widespread human-to-animal transmission of pandemic (H1N1) 2009 influenza viruses in South Korea. With the significant role of pigs in the ecology of influenza viruses, these transmission events should be closely monitored and minimized to prevent the risk of generating viruses with greater human health concerns.
| S-EPMC2937722 | biostudies-literature
Project description:Adamantane and oseltamivir resistance among influenza viruses is a major concern to public health officials. To determine the prevalence of antiviral-resistant influenza viruses in Guangdong, China, 244 seasonal A (H1N1) and 222 pandemic A (H1N1) 2009 viruses were screened for oseltamivir resistance by a fluorescence-based neuraminidase (NA) inhibition assay along with NA gene sequencing. Also, 147 seasonal A (H1N1) viruses were sequenced to detect adamantane resistance markers in M2. Adamantane-resistant seasonal A (H1N1) viruses clustering to clade 2C were dominant in 2008, followed by oseltamivir-resistant seasonal A (H1N1) viruses, clustering to clade 2B during January and May 2009. In June 2009, a lineage of double-resistant seasonal A (H1N1) viruses emerged, until it was replaced by the pandemic A (H1N1) 2009 viruses. The lineage most likely resulted from reassortment under the pressure of the overuse of adamantanes. As all viruses were resistant to at least one of the two types of antiviral agents, the need for close monitoring of the prevalence of antiviral resistance is stressed.
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