Oseltamivir-resistant influenza A(H1N1)pdm2009 strains found in Brazil are endowed with permissive mutations, which compensate the loss of fitness imposed by antiviral resistance

The 2009 pandemic influenza A virus outbreak led to the systematic use of the neuraminidase (NA) inhibitor oseltamivir (OST). Consequently, OST-resistant strains, carrying the mutation H275Y, emerged in the years after the pandemics, with a prevalence of 1-2%. Currently, OST-resistant strains have been found in community settings, in untreated individuals. To spread in community settings, H275Y mutants must contain additional mutations, collectively called permissive mutations. We display the permissive mutations in NA of OST-resistant A(H1N1)pdm09 virus found in Brazilian community settings. The NAs from 2013 are phylogenetically distinct from those of 2012, indicating a tendency of positive selection of NAs with better fitness. Some previously predicted permissive mutations, such as V241I and N369K, found in different countries, were also detected in Brazil. Importantly, the change D344N, also predicted to compensate loss of fitness imposed by H275Y mutation, was found in Brazil, but not in other countries in 2013. Our results reinforce the notion that OST-resistant A(H1N1)pdm09 strains with compensatory mutations may arise in an independent fashion, with samples being identified in different states of Brazil and in different countries. Systematic circulation of these viral strains may jeopardise the use of the first line of anti-influenza drugs in the future. (AU)

Oseltamivir-resistant influenza A(H1N1)pdm09 virus in southern Brazil

The neuraminidase (NA) genes of A(H1N1)pdm09 influenza virus isolates from 306 infected patients were analysed. The circulation of oseltamivir-resistant viruses in Brazil has not been reported previously. Clinical samples were collected in the state of Rio Grande do Sul (RS) from 2009-2011 and two NA inhibitor-resistant mutants were identified, one in 2009 (H275Y) and the other in 2011 (S247N). This study revealed a low prevalence of resistant viruses (0.8%) with no spread of the resistant mutants throughout RS.

Virological surveillance and antiviral resistance of human influenza virus in Argentina, 2005–2008 / Vigilancia virológica y resistencia a los antivíricos del virus de la gripe humana en la Argentina, 2005–2008

Objective. To describe the virological characteristics of the influenza strains circulating in Argentina in 2005–2008 and to assess the prevalence of antiviral resistance. Methods. On the basis of their geographical spread and prevalence, influenza A and B isolates grown in Madin–Darby canine kidney cells were selected after antigenic and genomic characterization to be analyzed for antiviral resistance by enzymatic assay and pyrosequencing. Amantadine susceptibility was evaluated by pyrosequencing for known resistance markers on 45 strains of influenza A. Susceptibility to oseltamivir and zanamivir was evaluated by enzymatic assay of 67 influenza A and 46 influenza B strains, some of which were further analyzed by sequencing the neuraminidase gene. Results. Resistance to amantadine was observed only on A(H3N2) strains (29/33); all of them carried the mutation S31N in their M2 sequence. Oseltamivir resistance was observed in 12 (34.3%) of the 35 A(H1N1) strains from 2008; all of them carried the mutation H275Y in their neuraminidase sequence. All these viruses remained sensitive to zanamivir. Conclusions. This study describes a high incidence of amantadine-resistant influenza A(H3N2) viruses since 2006 and an unprecedented increase in oseltamivir resistance detected only in influenza A(H1N1) viruses isolated in 2008. Influenza A and B viruses were more sensitive to oseltamivir than to zanamivir, and influenza A viruses were more sensitive to both neuraminidase inhibitors than the influenza B viruses. The national data generated and analyzed in this study may help increase knowledge about influenza antiviral drug resistance, which is a problem of global concern.

Objetivo. Describir las características virológicas de las cepas de virus de la gripe que circulaban en la Argentina entre el 2005 y el 2008, y evaluar la prevalencia de la resistencia a los antivíricos. Métodos. Según su diseminación geográfica y su prevalencia, se seleccionaron aislados de gripe A y B cultivados en células renales caninas de Madin-Darby después de su caracterización antigénica y genómica, y se analizó su resistencia a los antivíricos mediante análisis enzimático y pirosecuenciación. La sensibilidad a la amantadina se evaluó por pirosecuenciación para los marcadores conocidos de resistencia en 45 cepas de gripe A. La sensibilidad al oseltamivir y al zanamivir se evaluó mediante análisis enzimático de 67 cepas de gripe A y 46 cepas de gripe B, algunas de las cuales se analizaron en mayor profundidad mediante la secuenciación del gen de la neuraminidasa. Resultados. Se observó resistencia a la amantadina solo en las cepas de gripe A (H3N2) (29/33); todas ellas tenían la mutación S31N en su secuencia de M2. Se observó resistencia al oseltamivir en 12 (34,3%) de las 35 cepas de gripe A (H1N1) aisladas en el 2008; todas ellas tenían la mutación H275Y en su secuencia de neuraminidasa. Todos estos virus conservaron su sensibilidad al zanamivir. Conclusiones. En este estudio se describe una incidencia elevada del virus de la gripe A (H3N2) resistente a la amantadina desde el 2006 y un aumento sin precedentes de la resistencia al oseltamivir detectada solo en los virus de la gripe A (H1N1) aislados en el 2008. Los virus de la gripe A y B fueron más sensibles al oseltamivir que al zanamivir y los virus de la gripe A fueron más sensibles a ambos inhibidores de la neuraminidasa que los virus de la gripe B. Los datos nacionales generados y analizados en este estudio pueden ayudar a aumentar los conocimientos acerca de la resistencia a los fármacos antivíricos dirigidos contra el virus de la gripe, lo que es un motivo de preocupación mundial.

Estrategias para la reducción de la brecha del conocimiento a la acción en Argentina: la prevención y tratamiento de la influenza A (H1N1) en embarazadas como caso de análisis / Knowledge to action gap reduction strategies in Argentina: influenza A (H1N1) prevention and treatment in pregnant women as a case of analysis

Los reportes rápidos basados en la evidencia constituyen una de las estrategias para la reducción de la brecha del conocimiento a la acción. Objetivo: comunicar los resultados y lecciones aprendidas a partir de la elaboración de un reporte rápido sobre la efectividad y seguridad del uso de vacunas y antivirales para la influenza pandémica en embarazadas. Métodos: revisión sistemática sobre efectividad y seguridad del uso de antivirales y vacunas para influenza tipo A (H1N1) en embarazadas. Resultados: se recuperaron 166 citas: aunque sólo 88 cumplieron los criterios de inclusión. Los reportes epidemiológicos de la afectación de la pandemia señalan un riesgo de hospitalización tres a cinco veces más alto en embarazadas en comparación con la población general. Dos revisiones recientes indican que el oseltaminivir no estaría asociado con un mayor riesgo teratogénico. La evidencia sobre el zanamivir es escasa, absorción sistémica. A noviembre de 2009, la evidencia sobre la efectividad y seguridad de la vacuna para influenza A (H1N1) en embarazadas era escasa (dos ensayos en curso). Conclusión: los reportes rápidos constituyen una estrategia eficiente para el intercambio de conocimiento entre investigadores y decisores, aún en el contexto de una pandemia; sin embargo, es necesario encontrar métodos que permitan optimizar su implementación de manera sistemática y transparente.

Evidence-based rapid reviews constitute one of the knowledge to action GAP reduction strategies. Objective: to communicate the results and learned lessons during the elaboration of an evidence-based rapid review about the effectiveness and safety of vaccines and antivirals for influenza pandemic in pregnant women. Methods: all document containing evidence on adverse events and / or vaccines for influenza type A (H1N1) in pregnant women or that describes the evolution of the pandemic in this population was considered for analysis. Results: 166 articles were retrieved, although only 88 accomplished the inclusion criteria. Epidemiological reports of the pandemic situation indicate three to five times higher risk of hospitalization in pregnant women compared with the general population. Two recent reviews indicate that oseltamivir would not be associated with increased teratogenic risk. The evidence on the zanamivir is scarce, but the risk associated with its use is considered low because of its reduced systemic absortion. Through november 2009, evidence on effectiveness and safety of the H1N1 vaccine in pregnant women was scarce (two on-going clinical trials). Conclusion: evidence-based rapid reviews constitute an efficient strategy for researchers and decision-makers knowledge exchange, even in the context of a pandemic. However, methods that optimize its implementation through a systematic and transparent way are needed.