Nature, severity, and impact of chronic oropharyngeal dysphagia following curative resection for esophageal cancer: a cross-sectional study.

Chronic oropharyngeal dysphagia (COD) and aspiration after esophageal cancer surgery may have clinical significance; however, it is a rarely studied topic. In a prospective cross-sectional observational study we comprehensively evaluated the nature, severity, and impact of COD, its predictors, and the impact of the surgical approach and site of anastomosis. Forty participants were recruited via purposive sampling from the (Irish) National Center between November 2021 and August 2022. Swallow evaluations included videofluoroscopy [Dynamic Imaging Grade of Swallowing Toxicity v2 (DIGESTv2), MBS Impairment Profile, Penetration-Aspiration Scale)]. Functional Oral Intake Scale (FOIS) identified oral intake status. The patient reported outcome measures of swallowing, and Quality of Life (QL) included EAT-10 and MD Anderson Dysphagia Inventory (MDADI). Fourteen (35%) participants presented with COD on DIGESTv2 and 10% had uncleared penetration/aspiration. Avoidance or modification of diet on FOIS was observed in 17 (42.5%). FOIS was associated with pharyngeal dysphagia (OR = 4.05, P = 0.046). Median (range) EAT-10 and MDADI Composite results were 3(0-30) and 77.9(60-92.6), respectively. Aspiration rates significantly differed across surgical groups (P = 0.029); only patients undergoing transhiatal surgery aspirated. Survivors of esophageal cancer surgery may have COD that is undiagnosed, potentially impacting swallow-related QL. Given the small number of aspirators, further research is required to determine whether aspiration risk is associated with surgical approach. A FOIS score below 7 may be a clinically useful prompt for the MDT to refer for evaluation of COD following curative intent surgery. These data present findings that may guide preventive and rehabilitative strategies toward optimizing survivorship.

A Rough Colony Morphology of Mycobacterium abscessus Is Associated With Cavitary Pulmonary Disease and Poor Clinical Outcome.

BACKGROUND: The Mycobacterium abscessus complex (MABC) is a difficult to treat mycobacterium with two distinct morphologies: smooth and rough. As the clinical implications are unclear, we explored the morphology of MABC in relation to disease and outcome. METHODS: We performed a retrospective multicenter cohort study including patients with confirmed MABC in Sweden, 2009-2020, with treatment outcome as the primary outcome. MABC colony morphology was determined by light microscopy on Middlebrook 7H10 agar plates. RESULTS: Of the 71 MABC isolates, a defined morphology could be determined for 63 isolates, of which 40 were smooth (56%) and 23 were rough (32%). Immunosuppression, pulmonary disease, and cavitary lesion on chest radiographs were significantly associated with a rough isolate morphology. Participants with smooth isolates had more favorable treatment outcomes (12/14, 86%) compared to those with rough isolates (3/10, 30%). In an age-adjusted logistic regression, rough morphology of MABC was associated to lower odds of clinical cure compared to smooth morphology (adjusted odds ratio, 0.12; P = .049). CONCLUSIONS: Study participants with rough MABC colony morphology of isolates had a worse clinical outcome compared to those with smooth isolates. The biological mechanisms should be further characterized and colony morphology of MABC taken into account during clinical management.

Exercise-based dysphagia rehabilitation for adults with oesophageal cancer: a systematic review.

BACKGROUND: Dysphagia is prevalent in oesophageal cancer with significant clinical and psychosocial complications. The purpose of this study was i) to examine the impact of exercise-based dysphagia rehabilitation on clinical and quality of life outcomes in this population and ii) to identify key rehabilitation components that may inform future research in this area. METHODS: Randomised control trials (RCT), non-RCTs, cohort studies and case series were included. 10 databases (CINAHL Complete, MEDLINE, EMBASE, Web of Science, CENTRAL, and ProQuest Dissertations and Theses, OpenGrey, PROSPERO, RIAN and SpeechBITE), 3 clinical trial registries, and relevant conference abstracts were searched in November 2020. Two independent authors assessed articles for eligibility before completing data extraction, quality assessment using ROBINS-I and Downs and Black Checklist, followed by descriptive data analysis. The primary outcomes included oral intake, respiratory status and quality of life. All comparable outcomes were combined and discussed throughout the manuscript as primary and secondary outcomes. RESULTS: Three single centre non-randomised control studies involving 311 participants were included. A meta-analysis could not be completed due to study heterogeneity. SLT-led post-operative dysphagia intervention led to significantly earlier start to oral intake and reduced length of post-operative hospital stay. No studies found a reduction in aspiration pneumonia rates, and no studies included patient reported or quality of life outcomes. Of the reported secondary outcomes, swallow prehabilitation resulted in significantly improved swallow efficiency following oesophageal surgery compared to the control group, and rehabilitation following surgery resulted in significantly reduced vallecular and pyriform sinus residue. The three studies were found to have 'serious' to 'critical' risk of bias. CONCLUSIONS: This systematic review highlights a low-volume of low-quality evidence to support exercise-based dysphagia rehabilitation in adults undergoing surgery for oesophageal cancer. As dysphagia is a common symptom impacting quality of life throughout survivorship, findings will guide future research to determine if swallowing rehabilitation should be included in enhanced recovery after surgery (ERAS) programmes. This review is limited by the inclusion of non-randomised control trials and the reliance on Japanese interpretation which may have resulted in bias. The reviewed studies were all of weak design with limited data reported.

Influenza A/H4N2 mallard infection experiments further indicate zanamivir as less prone to induce environmental resistance development than oseltamivir.

Neuraminidase inhibitors (NAIs) are the gold standard treatment for influenza A virus (IAV). Oseltamivir is mostly used, followed by zanamivir (ZA). NAIs are not readily degraded in conventional wastewater treatment plants and can be detected in aquatic environments. Waterfowl are natural IAV hosts and replicating IAVs could thus be exposed to NAIs in the environment and develop resistance. Avian IAVs form the genetic basis for new human IAVs, and a resistant IAV with pandemic potential poses a serious public health threat, as NAIs constitute a pandemic preparedness cornerstone. Resistance development in waterfowl IAVs exposed to NAIs in the water environment has previously been investigated in an in vivo mallard model and resistance development was demonstrated in several avian IAVs after the exposure of infected ducks to oseltamivir, and in an H1N1 IAV after exposure to ZA. The N1 and N2 types of IAVs have different characteristics and resistance mutations, and so the present study investigated the exposure of an N2-type IAV (H4N2) in infected mallards to 1, 10 and 100 µg l-1 of ZA in the water environment. Two neuraminidase substitutions emerged, H274N (ZA IC50 increased 5.5-fold) and E119G (ZA IC50 increased 110-fold) at 10 and 100 µg l-1 of ZA, respectively. Reversion towards wild-type was observed for both substitutions in experiments with removed drug pressure, indicating reduced fitness of both resistant viruses. These results corroborate previous findings that the development of resistance to ZA in the environment seems less likely to occur than the development of resistance to oseltamivir, adding information that is useful in planning for prudent drug use and pandemic preparedness.

A systematic review of current methodology of high resolution pharyngeal manometry with and without impedance.

PURPOSE: This systematic review appraises and summaries methodology documented in studies using high resolution pharyngeal manometry (HRM) with and without impedance technology (HRIM) in adult populations. METHODS: Four electronic databases CINAHL, EMBASE, MEDLINE, and Cochrane Library were searched up to, and including March 2017. Studies reporting pharyngeal HRM/HRIM for swallowing and/or phonatory assessment, published in peer-reviewed journals in English, German, or Spanish were assessed for the inclusion criteria. Of the selected studies, methodological aspects of data acquisition and analysis were extracted. Publications were graded based on their level of evidence and quality of methodological aspects was assessed. RESULTS: Sixty-two articles were identified eligible, from which 50 studies reported the use of HRM and 12 studies used HRIM. Of all included manuscripts, the majority utilized the ManoScan™ system (64.5%), a catheter diameter of 4.2 mm was most prevalently documented (30.6%). Most publications reported the application of topical anesthesia (53.2%). For data analysis in studies using HRM, software intrinsic to the recording system was reported most frequently (56%). A minority of the studies using HRM provided data about measurement reliability (10%). This is higher for studies using HRIM (50%). CONCLUSIONS: Considerable methodological variability exists regarding data acquisition and analysis in published studies using HRM/HRIM. Lacking reports of methodology make study replications difficult and reduce the comparability across studies. More data regarding the impact of individual methodological aspects on study outcomes are further required for the development of methodological recommendations.

In vivo mallard experiments indicate that zanamivir has less potential for environmental influenza A virus resistance development than oseltamivir.

Neuraminidase inhibitors are a cornerstone of influenza pandemic preparedness before vaccines can be mass-produced and thus a neuraminidase inhibitor-resistant pandemic is a serious threat to public health. Earlier work has demonstrated the potential for development and persistence of oseltamivir resistance in influenza A viruses exposed to environmentally relevant water concentrations of the drug when infecting mallards, the natural influenza reservoir that serves as the genetic base for human pandemics. As zanamivir is the major second-line neuraminidase inhibitor treatment, this study aimed to assess the potential for development and persistence of zanamivir resistance in an in vivo mallard model; especially important as zanamivir will probably be increasingly used. Our results indicate less potential for development and persistence of resistance due to zanamivir than oseltamivir in an environmental setting. This conclusion is based on: (1) the lower increase in zanamivir IC50 conferred by the mutations caused by zanamivir exposure (2-17-fold); (2) the higher zanamivir water concentration needed to induce resistance (at least 10 µg l-1); (3) the lack of zanamivir resistance persistence without drug pressure; and (4) the multiple resistance-related substitutions seen during zanamivir exposure (V116A, A138V, R152K, T157I and D199G) suggesting lack of one straight-forward evolutionary path to resistance. Our study also adds further evidence regarding the stability of the oseltamivir-induced substitution H275Y without drug pressure, and demonstrates the ability of a H275Y-carrying virus to acquire secondary mutations, further boosting oseltamivir resistance when exposed to zanamivir. Similar studies using influenza A viruses of the N2-phylogenetic group of neuraminidases are recommended.

Implementing the Free Water Protocol does not Result in Aspiration Pneumonia in Carefully Selected Patients with Dysphagia: A Systematic Review.

The Frazier Free Water Protocol was developed with the aim of providing patients with dysphagia an option to consume thin (i.e. unthickened) water in-between mealtimes. A systematic review was conducted of research published in peer-reviewed journals. An electronic search of the EMBASE, CINAHL and MEDLINE databases was completed up to July 2016. A total of 8 studies were identified for inclusion: 5 randomised controlled trials, 2 cohort studies with matched cases and 1 single group pre-post intervention prospective study. A total of 215 rehabilitation inpatients and 30 acute patients with oropharyngeal dysphagia who required thickened fluids or were to remain 'nil by mouth', as determined by bedside swallow assessment and/or videofluoroscopy/fiberoptic endoscopic evaluation of swallowing, were included. Meta-analyses of the data from the rehabilitation studies revealed (1) low-quality evidence that implementing the protocol did not result in increased odds of having lung complications and (2) low-quality evidence that fluid intake may increase. Patients' perceptions of swallow-related quality of life appeared to improve. This review has found that when the protocol is closely adhered to and patients are carefully selected using strict exclusion criteria, including an evaluation of their cognition and mobility, adult rehabilitation inpatients with dysphagia to thin fluids can be offered the choice of implementing the Free Water Protocol. Further research is required to determine if the Free Water Protocol can be implemented in settings other than inpatient rehabilitation.

Influenza A(H7N9) virus acquires resistance-related neuraminidase I222T substitution when infected mallards are exposed to low levels of oseltamivir in water.

Influenza A virus (IAV) has its natural reservoir in wild waterfowl, and new human IAVs often contain gene segments originating from avian IAVs. Treatment options for severe human influenza are principally restricted to neuraminidase inhibitors (NAIs), among which oseltamivir is stockpiled in preparedness for influenza pandemics. There is evolutionary pressure in the environment for resistance development to oseltamivir in avian IAVs, as the active metabolite oseltamivir carboxylate (OC) passes largely undegraded through sewage treatment to river water where waterfowl reside. In an in vivo mallard (Anas platyrhynchos) model, we tested if low-pathogenic avian influenza A(H7N9) virus might become resistant if the host was exposed to low levels of OC. Ducks were experimentally infected, and OC was added to their water, after which infection and transmission were maintained by successive introductions of uninfected birds. Daily fecal samples were tested for IAV excretion, genotype, and phenotype. Following mallard exposure to 2.5 µg/liter OC, the resistance-related neuraminidase (NA) I222T substitution, was detected within 2 days during the first passage and was found in all viruses sequenced from subsequently introduced ducks. The substitution generated 8-fold and 2.4-fold increases in the 50% inhibitory concentration (IC50) for OC (P < 0.001) and zanamivir (P = 0.016), respectively. We conclude that OC exposure of IAV hosts, in the same concentration magnitude as found in the environment, may result in amino acid substitutions, leading to changed antiviral sensitivity in an IAV subtype that can be highly pathogenic to humans. Prudent use of oseltamivir and resistance surveillance of IAVs in wild birds are warranted.

Oseltamivir-resistant influenza A (H1N1) virus strain with an H274Y mutation in neuraminidase persists without drug pressure in infected mallards.

Influenza A virus (IAV) has its natural reservoir in wild waterfowl, and emerging human IAVs often contain gene segments from avian viruses. The active drug metabolite of oseltamivir (oseltamivir carboxylate [OC]), stockpiled as Tamiflu for influenza pandemic preparedness, is not removed by conventional sewage treatment and has been detected in river water. There, it may exert evolutionary pressure on avian IAV in waterfowl, resulting in the development of resistant viral variants. A resistant avian IAV can circulate among wild birds only if resistance does not restrict viral fitness and if the resistant virus can persist without continuous drug pressure. In this in vivo mallard (Anas platyrhynchos) study, we tested whether an OC-resistant avian IAV (H1N1) strain with an H274Y mutation in the neuraminidase (NA-H274Y) could retain resistance while drug pressure was gradually removed. Successively infected mallards were exposed to decreasing levels of OC, and fecal samples were analyzed for the neuraminidase sequence and phenotypic resistance. No reversion to wild-type virus was observed during the experiment, which included 17 days of viral transmission among 10 ducks exposed to OC concentrations below resistance induction levels. We conclude that resistance in avian IAV that is induced by exposure of the natural host to OC can persist in the absence of the drug. Thus, there is a risk that human-pathogenic IAVs that evolve from IAVs circulating among wild birds may contain resistance mutations. An oseltamivir-resistant pandemic IAV would pose a substantial public health threat. Therefore, our observations underscore the need for prudent oseltamivir use, upgraded sewage treatment, and surveillance for resistant IAVs in wild birds.

Prevalence, nature and trajectory of dysphagia postoesophageal cancer surgery: a prospective longitudinal study protocol.

INTRODUCTION: Dysphagia is a common problem following oesophagectomy, and is associated with aspiration pneumonia, malnutrition, weight loss, prolonged enteral feeding tube dependence, in addition to an extended in-hospital stay and compromised quality of life (QOL). To date, the prevalence, nature and trajectory of post-oesophagectomy dysphagia has not been systematically studied in a prospective longitudinal design. The study aims (1) to evaluate the prevalence, nature and trajectory of dysphagia for participants undergoing an oesophagectomy as part of curative treatment, (2) to determine the risk factors for, and post-operative complications of dysphagia in this population and (3) to examine the impact of oropharyngeal dysphagia on health-related QOL across time points. METHODS AND ANALYSIS: A videofluoroscopy will be completed and analysed on both post-operative day (POD) 4 or 5 and at 6-months post-surgery. Other swallow evaluations will be completed preoperatively, POD 4 or 5, 1-month and 6-month time points will include a swallowing screening test, tongue pressure measurement, cough reflex testing and an oral hygiene evaluation. Nutritional measurements will include the Functional Oral Intake Scale to measure feeding tube reliance, Malnutrition Screening Tool and the Strength, Assistance With Walking, Rise From a Chair, Climb Stairs and Falls questionnaire. The Reflux Symptom Index will be administered to investigate aerodigestive symptoms commonly experienced by adults post-oesophagectomy. Swallowing-related QOL outcome measures will be determined using the European Organisation for Research and Treatment of Cancer QLQ-18, MD Anderson Dysphagia Inventory and the Swallowing Quality of Life Questionnaire. ETHICS AND DISSEMINATION: Ethical approval has been granted by the Tallaght University Hospital/St. James' Hospital Research Ethics Committee (JREC), Dublin, Ireland (Ref. No. 2021-Jul-310). The study results will be published in peer-reviewed journals and presented at national and international scientific conferences.

Primary tuberculosis infection in 35 children at a Swedish day care center.

BACKGROUND AND METHOD: The decline of tuberculosis (TB) in the Swedish population since the middle of the 20th century resulted in decreased awareness of the disease. Increased migration from TB-endemic countries has resulted in new cases and risk of transmission. A day care provider was diagnosed with cavitary TB after being symptomatic for 5 months. We describe the contact tracing at the day care center, the clinical and radiographic findings, and treatment of the infected children. RESULTS: We stratified the children by contact with the source case and examined the most exposed first. Thirty-two of 53 attending and 3 of 84 visiting preschool children were infected. All of them had spent at least 3 days at the center. Symptoms were usually mild and nonspecific. Seventeen children had pulmonary radiographic changes compatible with primary TB, and one had miliary TB. The radiographic resolution was slow, with normalization in 50% after 12 months. Eighteen months after termination of treatment, there have been no relapses. The children with latent infection were treated with rifampin for 4 months and none has developed TB. CONCLUSIONS: The manifestations of primary TB in children today are similar to those described 50-70 years ago. The tuberculin skin test is an effective tool for contact tracing in an unvaccinated, previously nonexposed childhood population. Rapid detection of contagious patients and thorough contact investigation remain our most important means to reduce transmission.

Risk of resistant avian influenza A virus in wild waterfowl as a result of environmental release of oseltamivir.

Oseltamivir is the best available anti-influenza drug and has therefore been stockpiled worldwide in large quantities as part of influenza pandemic preparedness planning. The active metabolite oseltamivir carboxylate (OC) is stable and is not removed by conventional sewage treatment. Active OC has been detected in river water at concentrations up to 0.86 µg/L. Although the natural reservoir hosts of influenza A virus (IAV) are wild waterfowl that reside in aquatic environments, the ecologic risks associated with environmental OC release and its potential to generate resistant viral variants among wild birds has largely been unknown. However, in recent years a number of in vivo mallard (Anas platyrhynchos) studies have been conducted regarding the potential of avian IAVs to become resistant to OC in natural reservoir birds if these are drug exposed. Development of resistance to OC was observed both in Group 1 (N1) and Group 2 (N2, N9) neuraminidase subtypes, when infected ducks were exposed to OC at concentrations between 0.95 and 12 µg/L in their water. All resistant variants maintained replication and transmission between ducks during drug exposure. In an A(H1N1)/H274Y virus, the OC resistance mutation persisted without selective drug pressure, demonstrating the potential of an IAV with a permissive genetic background to acquire and maintain OC resistance, potentially allowing circulation of the resistant variant among wild birds. The experimental studies have improved the appreciation of the risks associated with the environmental release of OC related to resistance development of avian IAVs among wild birds. Combined with knowledge of efficient methods for improved sewage treatment, the observations warrant implementation of novel efficient wastewater treatment methods, rational use of anti-influenza drugs, and improved surveillance of IAV resistance in wild birds.

Oseltamivir Resistance in Influenza A(H6N2) Caused by an R292K Substitution in Neuraminidase Is Not Maintained in Mallards without Drug Pressure.

BACKGROUND: Wild waterfowl is the natural reservoir of influenza A virus (IAV); hosted viruses are very variable and provide a source for genetic segments which can reassort with poultry or mammalian adapted IAVs to generate novel species crossing viruses. Additionally, wild waterfowl act as a reservoir for highly pathogenic IAVs. Exposure of wild birds to the antiviral drug oseltamivir may occur in the environment as its active metabolite can be released from sewage treatment plants to river water. Resistance to oseltamivir, or to other neuraminidase inhibitors (NAIs), in IAVs of wild waterfowl has not been extensively studied. AIM AND METHODS: In a previous in vivo Mallard experiment, an influenza A(H6N2) virus developed oseltamivir resistance by the R292K substitution in the neuraminidase (NA), when the birds were exposed to oseltamivir. In this study we tested if the resistance could be maintained in Mallards without drug exposure. Three variants of resistant H6N2/R292K virus were each propagated during 17 days in five successive pairs of naïve Mallards, while oseltamivir exposure was decreased and removed. Daily fecal samples were analyzed for viral presence, genotype and phenotype. RESULTS AND CONCLUSION: Within three days without drug exposure no resistant viruses could be detected by NA sequencing, which was confirmed by functional NAI sensitivity testing. We conclude that this resistant N2 virus could not compete in fitness with wild type subpopulations without oseltamivir drug pressure, and thus has no potential to circulate among wild birds. The results of this study contrast to previous observations of drug induced resistance in an avian H1N1 virus, which was maintained also without drug exposure in Mallards. Experimental observations on persistence of NAI resistance in avian IAVs resemble NAI resistance seen in human IAVs, in which resistant N2 subtypes do not circulate, while N1 subtypes with permissive mutations can circulate without drug pressure. We speculate that the phylogenetic group N1 NAs may easier compensate for NAI resistance than group N2 NAs, though further studies are needed to confirm such conclusions.

Online solid phase extraction liquid chromatography using bonded zwitterionic stationary phases and tandem mass spectrometry for rapid environmental trace analysis of highly polar hydrophilic compounds - Application for the antiviral drug Zanamivir.

Zanamivir (Za) is a highly polar and hydrophilic antiviral drug used for the treatment of influenza A viruses. Za has been detected in rivers of Japan and it's environmental occurrence has the risk of inducing antiviral resistant avian influenza viruses. In this study, a rapid automated online solid phase extraction liquid chromatography method using bonded zwitterionic stationary phases and tandem mass spectrometry (SPE/LC-MS/MS) for trace analysis of Za was developed. Furthermore, an internal standard (IS) calibration method capable of quantifying Za in Milli-Q, surface water, sewage effluent and sewage influent was evaluated. Optimum pre-extraction sample composition was found to be 95/5 v/v acetonitrile/water sample and 1% formic acid. The developed method showed acceptable linearities (r(2)≥0.994), filtration recovery (≥91%), and intra-day precisions (RSD≤16%), and acceptable and environmentally relevant LOQs (≤20ngL(-1)). Storage tests showed no significant losses of Za during 20 days and +4/-20°C (≤12%) with the exception of influent samples, which should be kept at -20°C to avoid significant Za losses. The applicability of the method was demonstrated in a study on phototransformation of Za in unfiltered and filtered surface water during 28 days of artificial UV irradiation exposure. No significant (≤12%) phototransformation was found in surface water after 28 days suggesting a relatively high photostability of Za and that Za should be of environmental concern.

The Spanish flu in Uppsala, clinical and epidemiological impact of the influenza pandemic 1918-1919 on a Swedish county.

INTRODUCTION AND AIM: The Spanish flu reached Sweden in June 1918, and at least one-third of the population (then 5.8 million) became infected. Some 34,500 persons (5.9 per 1,000 people) died from influenza during the first year of the pandemic (when acute pneumonia is included, the number of deaths rose to 7.1 per 1,000 people). In this historical look back at the pandemic, our aim was to review the epidemiological impact on the Swedish county of Uppsala, the clinical outcomes and the economic impact on the regional hospital; a relevant backgound to consider the impact of a future virulent pandemic. We also focused on how the pandemic was perceived by the medical community and by health care authorities. METHODS: Health care reports, statistics, daily newspapers, medical journals, and records of patients treated for influenza at the Uppsala Academic Hospital from July 1918 to June 1919 were included in our review. RESULTS: An influenza related mortality rate of 693 persons (5.1 per 1,000 people) was reported in the Uppsala region from 1918-1919; from July 1918 to June 1919, 384 patients were treated for influenza at the Uppsala Academic Hospital. The first wave peaked in November 1918 with case fatality rates up to 30%; a second wave peaked in April 1919 with a lower rate of mortality. Of the patients treated, a total of 66 died. Of these, 60% were 20-29 years of age, and 85% were less than 40 years old. Autopsy reports revealed pneumonia in 89% of the cases; among these, 47% were hemorrhagic, 18% were bilateral, and 45% had additional extrapulmonary organ involvement. Signs of severe viral disease were documented, but secondary bacterial disease was the primary cause of death in the majority of cases. CONCLUSION: The epidemiologic and pathologic results were in accordance with other publications of this time period. The costs of running the hospital doubled from 1917 to 1920 and then reversed by 45%. Today, an influenza pandemic of the same virulence would paralyze health care systems and result in extremely high financial costs and rates of mortality.

Resistance mutation R292K is induced in influenza A(H6N2) virus by exposure of infected mallards to low levels of oseltamivir.

Resistance to neuraminidase inhibitors (NAIs) is problematic as these drugs constitute the major treatment option for severe influenza. Extensive use of the NAI oseltamivir (Tamiflu®) results in up to 865 ng/L of its active metabolite oseltamivir carboxylate (OC) in river water. There one of the natural reservoirs of influenza A, dabbling ducks, can be exposed. We previously demonstrated that an influenza A(H1N1) virus in mallards (Anas platyrhynchos) exposed to 1 µg/L of OC developed oseltamivir resistance through the mutation H274Y (N2-numbering). In this study, we assessed the resistance development in an A(H6N2) virus, which belongs to the phylogenetic N2 group of neuraminidases with distinct functional and resistance characteristics. Mallards were infected with A(H6N2) while exposed to 120 ng/L, 1.2 µg/L or 12 µg/L of OC in their sole water source. After 4 days with 12 µg/L of OC exposure, the resistance mutation R292K emerged and then persisted. Drug sensitivity was decreased ≈13,000-fold for OC and ≈7.8-fold for zanamivir. Viral shedding was similar when comparing R292K and wild-type virus indicating sustained replication and transmission. Reduced neuraminidase activity and decrease in recovered virus after propagation in embryonated hen eggs was observed in R292K viruses. The initial, but not the later R292K isolates reverted to wild-type during egg-propagation, suggesting a stabilization of the mutation, possibly through additional mutations in the neuraminidase (D113N or D141N) or hemagglutinin (E216K). Our results indicate a risk for OC resistance development also in a N2 group influenza virus and that exposure to one NAI can result in a decreased sensitivity to other NAIs as well. If established in influenza viruses circulating among wild birds, the resistance could spread to humans via re-assortment or direct transmission. This could potentially cause an oseltamivir-resistant pandemic; a serious health concern as preparedness plans rely heavily on oseltamivir before vaccines can be mass-produced.