Replication of an H9N2 Avian Influenza Virus and Cytokine Gene Expression in Chickens Exposed by Aerosol or Intranasal Routes.

This study related the replication of an H9N2 avian influenza virus in chickens to the induction of host acute immune response after aerosol or intranasal inoculation with the virus. On 1, 2, 4, and 7 days postinoculation (dpi), oropharyngeal swabs and tissue specimens of trachea, lungs, spleen, and cecal tonsils were collected for quantification of viral RNA. Expression of cytokine genes in lungs, spleen, and cecal tonsils was quantified by reverse transcriptase-PCR. Virus was detected in all oropharyngeal swabs up to 4 dpi in chickens from both inoculation groups. However, virus was detected more frequently (P<0.05) and in higher titers (1-4 log difference) in specimens of trachea and lungs from the group exposed to aerosols than from the group given intranasal drops. In accord with viral replication findings, expressions of cytokine genes interleukin (IL)-1ß (on 2 and 7 dpi), IL-6 (on 2 dpi), and interferon (IFN)-γ (on 2 and 4 dpi) were up-regulated to a significantly higher level (P<0.05) in lung tissue specimens from the group exposed to virus aerosol than from controls that were given saline intranasally. Only IFN-γ on 1 dpi was up-regulated (P<0.05) above that of controls in lung tissue specimens from the group given intranasal drops of virus. In comparison, replication of the virus and induction of IL-1ß and IL-6 genes were limited in spleen and cecal tonsil tissue specimens from both groups of chickens inoculated with the virus. These findings indicate that virus administered in aerosols was more efficient than virus administered as intranasal drops, in infecting the lower respiratory tract and in inducing the activity of the cytokine genes. The intense respiratory infection caused by virus aerosols might increase the shedding and transmission of the H9N2 virus in chickens.

Optimization of RT-QuIC Assay Duration for Screening Chronic Wasting Disease in White-Tailed Deer.

Real-time quaking-induced conversion (RT-QuIC) assays have become a common tool to detect chronic wasting disease (CWD) and are very sensitive provided the assay duration is sufficient. However, a prolonged assay duration may lead to non-specific signal amplification. The wide range of pre-defined assay durations in current RT-QuIC applications presents a need for methods to optimize the RT-QuIC assay. In this study, receiver operating characteristic (ROC) analysis was applied to optimize the assay duration for CWD screening in obex and retropharyngeal lymph node (RLN) tissue specimens. Two different fluorescence thresholds were used: a fixed threshold based on background fluorescence (Tstdev) and a max-point ratio (maximum/background fluorescence) threshold (TMPR) to determine CWD positivity. The optimal assay duration was 33 h for obex and 30 h for RLN based on Tstdev, and 29 h for obex and 32 h for RLN based on TMPR. The optimized assay durations were then evaluated for screening CWD in white-tailed deer from an affected farm. At a replicate level, using the optimized assay durations with TStdev and TMPR, the level of agreement with enzyme-linked immunosorbent assay (ELISA) was significantly higher (p < 0.05) than that when using a 40 h assay duration. These findings demonstrate that the optimization of assay duration via a ROC analysis can improve RT-QuIC assays for screening CWD in white-tailed deer.

Aerosol transmission of an avian influenza H9N2 virus with a tropism for the respiratory tract of chickens.

A low pathogenic avian influenza virus (LPAI H9N2) was administered to 3-wk-old chickens by aerosol exposure, intranasal inoculation, and by oral inoculation. Tests for virus were by in ovo assay and by real-time reverse-transcriptase PCR. The aerosol dosage was determined by aerosolizing virus into a chamber when it was empty and when it contained chickens. Air was collected and the amount of virus inhaled was estimated to be about 18% of the total body uptake. In transmission studies, tests for virus were conducted on oropharyngeal or cloacal swabs. The 50% infectious dose (ID50) for aerosolized virus was about 2 log 10 and 5 log 10 lower than by nasal or oral inoculation, respectively. The recovery rate was higher from swabs of the oropharyngeal region than from the cloacal region (P < 0.05). For horizontal transmission studies, uninfected chickens were held in isolators with seeders that had been inoculated intranasally with the H9N2 virus. Chickens exposed by indirect contact were separated by screens from the seeders. In another isolator those directly exposed were intermingled with the seeders. During the 10-day test period, none of the chickens developed symptoms of disease, but infection was detected as early as 4 and 7 days in the indirectly and directly exposed groups, respectively. These findings suggested that aerosol transmission of viruses similar to LPAI H9N2 could efficiently occur, at least over short distances.

Evaluation of Pressurized Steam Disinfection of Surfaces Contaminated by Mycobacterium terrae: A Surrogate for Mycobacterium bovis.

Introduction: Decontamination of farms affected by bovine tuberculosis could be very challenging during outbreaks occurring in the winter with freezing temperatures. Steam treatment has been of practical interest, but information is needed on whether such treatment is able to inactivate the causative agent, Mycobacterium bovis. This study was to evaluate the use of pressurized steam for inactivation of Mycobacterium terrae, a surrogate for M. bovis on various surfaces. Methods: Carrier disks made of steel, wood, or rubber were inoculated with 6.32 ± 0.38 log10 M. terrae. While being held at background temperatures of -20°C, 4°C, or 21°C, these carrier disks were treated with pressurized steam (120°C ± 5°C) for 5, 10, 15, or 20 s. Reduction in colony forming units of M. terrae and temperatures on the top and bottom surfaces of the disks were determined. Results: Complete inactivation of 6 log10 M. terrae on steel and wood disks was achieved by 10 s of steam treatment at all three background temperatures. In comparison, 20 s of steam treatment was needed for the complete inactivation of mycobacteria on rubber disks. Corresponding to the longer treatment time required for mycobacterial inactivation, temperatures on the bottom surface of the rubber disks rose substantially slower than those of the steel and wood disks at all three background temperatures. Conclusion: The results suggested that treatment with pressurized steam has potential for efficient and effective disinfection of surfaces contaminated by mycobacteria at or below freezing temperatures in winter.

Unsupervised Feature Selection via Graph Regularized Nonnegative CP Decomposition.

Unsupervised feature selection has attracted remarkable attention recently. With the development of data acquisition technology, multi-dimensional tensor data has been appeared in enormous real-world applications. However, most existing unsupervised feature selection methods are non-tensor-based which results the vectorization of tensor data as a preprocessing step. This seemingly ordinary operation has led to an unnecessary loss of the multi-dimensional structural information and eventually restricted the quality of the selected features. To overcome the limitation, in this paper, we propose a novel unsupervised feature selection model: Nonnegative tensor CP (CANDECOMP/PARAFAC) decomposition based unsupervised feature selection, CPUFS for short. In specific, we devise new tensor-oriented linear classifier and feature selection matrix for CPUFS. In addition, CPUFS simultaneously conducts graph regularized nonnegative CP decomposition and newly-designed tensor-oriented pseudo label regression and feature selection to fully preserve the multi-dimensional data structure. To solve the CPUFS model, we propose an efficient iterative optimization algorithm with theoretically guaranteed convergence, whose computational complexity scales linearly in the number of features. A variation of the CPUFS model by incorporating nonnegativity into the linear classifier, namely CPUFSnn, is also proposed and studied. Experimental results on ten real-world benchmark datasets demonstrate the effectiveness of both CPUFS and CPUFSnn over the state-of-the-arts.

Community Detection via Multihop Nonnegative Matrix Factorization.

Community detection aims at finding all densely connected communities in a network, which serves as a fundamental graph tool for many applications, such as identification of protein functional modules, image segmentation, social circle discovery, to name a few. Recently, nonnegative matrix factorization (NMF)-based community detection methods have attracted significant attention. However, most existing methods neglect the multihop connectivity patterns in a network, which turn out to be practically useful for community detection. In this article, we first propose a novel community detection method, namely multihop NMF (MHNMF for brevity), which takes into account the multihop connectivity patterns in a network. Subsequently, we derive an efficient algorithm to optimize MHNMF and theoretically analyze its computational complexity and convergence. Experimental results on 12 real-world benchmark networks demonstrate that MHNMF outperforms 12 state-of-the-art community detection methods.

Complete Genome Sequence of a Canadian Strain of Escherichia coli with Multiple Metal and Antimicrobial Resistance Genes That Was Isolated from Municipal Biosolids.

This announcement reports the complete genome sequence of a non-Shiga toxin-producing Escherichia coli strain that was isolated from municipal biosolids collected from a Canadian wastewater treatment plant. This strain contains multiple metal, antimicrobial, and heat resistance genes, as determined by genome sequencing, and could be a useful bacterial model for future studies.

Reduction of Aspergillus flavus and aflatoxin on almond kernels using gaseous chlorine dioxide fumigation.

The almond industry suffers product losses caused by mold growth and toxin contamination. Gaseous chlorine dioxide (ClO2) has the potential for postharvest reduction of mycotoxic Aspergillus flavus. In this study, almonds inoculated with A. flavus were fumigated with gaseous ClO2 for 1, 2, 3, 8, 12, and 24 h using a dry precursor sachet batch method. The headspace concentration ranged from 0.5 to 2.4 mg/L, depending on initial dosing and time. At its highest concentration, gaseous ClO2 demonstrated an 84.4 % degradation efficiency of aflatoxin B1 (AFB1) with a reduction of 2.4 log CFU/g of A. flavus on almond kernels. Additionally, suppression of AFB1 continued after one-month storage at 4 °C. No significant oxidative effect and color difference (ΔE) was observed on the treated kernels. The almond industry can apply gaseous ClO2 technology to reduce mold contamination and product losses.

Community Detection via Autoencoder-Like Nonnegative Tensor Decomposition.

Community detection aims at partitioning a network into several densely connected subgraphs. Recently, nonnegative matrix factorization (NMF) has been widely adopted in many successful community detection applications. However, most existing NMF-based community detection algorithms neglect the multihop network topology and the extreme sparsity of adjacency matrices. To resolve them, we propose a novel conception of adjacency tensor, which extends adjacency matrix to multihop cases. Then, we develop a novel tensor Tucker decomposition-based community detection method-autoencoder-like nonnegative tensor decomposition (ANTD), leveraging the constructed adjacency tensor. Distinct from simply applying tensor decomposition on the constructed adjacency tensor, which only works as a decoder, ANTD also introduces an encoder component to constitute an autoencoder-like architecture, which can further enhance the quality of the detected communities. We also develop an efficient alternative updating algorithm with convergence guarantee to optimize ANTD, and theoretically analyze the algorithm complexity. Moreover, we also study a graph regularized variant of ANTD. Extensive experiments on real-world benchmark networks by comparing 27 state-of-the-art methods, validate the effectiveness, efficiency, and robustness of our proposed methods.

Unsupervised Feature Selection via Orthogonal Basis Clustering and Local Structure Preserving.

Due to the "curse of dimensionality" issue, how to discard redundant features and select informative features in high-dimensional data has become a critical problem, hence there are many research studies dedicated to solving this problem. Unsupervised feature selection technique, which does not require any prior category information to conduct with, has gained a prominent place in preprocessing high-dimensional data among all feature selection techniques, and it has been applied to many neural networks and learning systems related applications, e.g., pattern classification. In this article, we propose an efficient method for unsupervised feature selection via orthogonal basis clustering and reliable local structure preserving, which is referred to as OCLSP briefly. Our OCLSP method consists of an orthogonal basis clustering together with an adaptive graph regularization, which realizes the functionality of simultaneously achieving excellent cluster separation and preserving the local information of data. Besides, we exploit an efficient alternative optimization algorithm to solve the challenging optimization problem of our proposed OCLSP method, and we perform a theoretical analysis of its computational complexity and convergence. Eventually, we conduct comprehensive experiments on nine real-world datasets to test the validity of our proposed OCLSP method, and the experimental results demonstrate that our proposed OCLSP method outperforms many state-of-the-art unsupervised feature selection methods in terms of clustering accuracy and normalized mutual information, which indicates that our proposed OCLSP method has a strong ability in identifying more important features.

Evaluation of the Use of Sea Water as a Diluent for an Accelerated Hydrogen Peroxide Disinfectant for Inactivation of Avian Influenza Virus: A Surrogate for Infectious Salmon Anemia Virus.

Introduction: Use of sea water as a diluent for disinfectants has been of practical interest for control of aquaculture disease outbreaks in sea where fresh water is limited. This study evaluated the use of natural sea water (NSW), artificial sea water (ASW), or standard hard water (SHW) as a diluent for preparation of accelerated hydrogen peroxide (AHP) solutions against an avian influenza virus, a surrogate for the infectious salmon anemia virus. Methods: AHP solutions containing 0.18%, 0.35%, or 0.44% (w/w) of hydrogen peroxide (H2O2), corresponding to 1/40, 1/20, and 1/16 dilutions of the disinfectant concentrate, were evaluated at -20°C, 4°C, and 21°C. Results: When NSW was used as the diluent, a 0.35% H2O2 concentration was required to inactivate ∼6 log10 virus at 21°C in a 5-min contact time. When temperature dropped to 4°C, 0.44% H2O2 in NSW was required to obtain a similar inactivation within a 5-min contact time. At -20°C, supplemented with antifreeze agents, the 0.44% H2O2 in NSW solutions produced complete inactivation of 5.4 log10 virus within a 10-min contact time. In comparison, lower H2O2 concentrations and/or shorter contact times were needed to inactivate equal amounts of the virus at the same temperature when using SHW or ASW as a diluent to prepare disinfection solutions. Conclusion: The results suggested that NSW could be used as a diluent in disinfection solutions for virus inactivation as long as disinfectant concentrations and/or contact times are properly increased.

A Review: Gaseous Interventions for Listeria monocytogenes Control in Fresh Apple Cold Storage.

Listeria monocytogenes (L. monocytogenes) causes an estimated 1600 foodborne illnesses and 260 deaths annually in the U.S. These outbreaks are a major concern for the apple industry since fresh produce cannot be treated with thermal technologies for pathogen control before human consumption. Recent caramel apple outbreaks indicate that the current non-thermal sanitizing protocol may not be sufficient for pathogen decontamination. Federal regulations provide guidance to apple processors on sanitizer residue limits, organic production, and good manufacturing practices (GMPs). However, optimal methods to control L. monocytogenes on fresh apples still need to be determined. This review discusses L. monocytogenes outbreaks associated with caramel apples and the pathogen's persistence in the environment. In addition, this review identifies and analyzes possible sources of contaminant for apples during cold storage and packing. Gaseous interventions are evaluated for their feasibility for L. monocytogenes decontamination on apples. For example, apple cold storage, which requires waterless interventions, may benefit from gaseous antimicrobials like chlorine dioxide (ClO2) and ozone (O3). In order to reduce the contamination risk during cold storage, significant research is still needed to develop effective methods to reduce microbial loads on fresh apples. This requires commercial-scale validation of gaseous interventions and intervention integration to the current existing apple cold storage. Additionally, the impact of the interventions on final apple quality should be taken into consideration. Therefore, this review intends to provide the apple industry suggestions to minimize the contamination risk of L. monocytogenes during cold storage and hence prevent outbreaks and reduce economic losses.

Mobility of ß-lactam resistance under ampicillin treatment in gut microbiota suffering from pre-disturbance.

Ingestion of food- or waterborne antibiotic-resistant bacteria may lead to dissemination of antibiotic resistance genes (ARGs) in the gut microbiota. The gut microbiota often suffers from various disturbances. It is not clear whether and how disturbed microbiota may affect ARG mobility under antibiotic treatments. For proof of concept, in the presence or absence of streptomycin pre-treatment, mice were inoculated orally with a ß-lactam-susceptible Salmonella enterica serovar Heidelberg clinical isolate (recipient) and a ß-lactam resistant Escherichia coli O80:H26 isolate (donor) carrying a blaCMY-2 gene on an IncI2 plasmid. Immediately following inoculation, mice were treated with or without ampicillin in drinking water for 7 days. Faeces were sampled, donor, recipient and transconjugant were enumerated, blaCMY-2 abundance was determined by quantitative PCR, faecal microbial community composition was determined by 16S rRNA amplicon sequencing and cecal samples were observed histologically for evidence of inflammation. In faeces of mice that received streptomycin pre-treatment, the donor abundance remained high, and the abundance of S. Heidelberg transconjugant and the relative abundance of Enterobacteriaceae increased significantly during the ampicillin treatment. Co-blooming of the donor, transconjugant and commensal Enterobacteriaceae in the inflamed intestine promoted significantly (P<0.05) higher and possibly wider dissemination of the blaCMY-2 gene in the gut microbiota of mice that received the combination of streptomycin pre-treatment and ampicillin treatment (Str-Amp) compared to the other mice. Following cessation of the ampicillin treatment, faecal shedding of S. Heidelberg transconjugant persisted much longer from mice in the Str-Amp group compared to the other mice. In addition, only mice in the Str-Amp group shed a commensal E. coli O2:H6 transconjugant, which carries three copies of the blaCMY-2 gene, one on the IncI2 plasmid and two on the chromosome. The findings highlight the significance of pre-existing gut microbiota for ARG dissemination and persistence during and following antibiotic treatments of infectious diseases.

The fate of recombinant plasmids during composting of organic wastes.

Composting was investigated as a means for safe disposal of organic waste containing bacteria that carry transgenes in recombinant plasmids. To generate model recombinant plasmids, a mobile IncQ plasmid, RSF1010, and a non-mobile plasmid, pGFP, were genetically modified to carry a DNA segment encoding both green fluorescent protein and kanamycin resistance and were designated as RSF1010-GFPK and pGFPK. Escherichia coli (E. coli) C600 harboring these plasmids were inoculated into chicken manure specimens that were placed in compost at 20 and 60 cm from the bottom of a 1.0-m high compost bin. Control specimens were held at ambient temperature. By day 10, compost temperatures at the lower and upper levels of the bin had reached 45.3 and 61.5 degrees C, respectively, and at both levels the target E. coli had been inactivated and the plasmids had lost their capacity to be transformed or mobilized. Furthermore, based on real time Polymerase chain reaction (PCR), the transgene fragments along with the host chromosomal DNA fragment from specimens at the upper level had been degraded beyond the detection limit. However, at the lower level where temperatures remained below 48 degrees C these fragment persisted to day 21. At ambient temperatures (0-8 degrees C), the E. coli, plasmids and the transgene fragments persisted in manure specimens throughout the 21 day test period. The study showed the potential for composting as a safe procedure for disposal of bacteria carrying transgenes in recombinant plasmids.

Understanding water activity change in oil with temperature.

Our recent studies and several publications suggest that the low water activity (aw) of oil in thermal processing might be a major contributing factor towards the increased thermal resistance of bacteria in oils. In this study, we developed a reliable method to measure the water activity of oil by measuring the equilibrium relative humidity in a small headspace. Using this method, water activity of peanut oil was found to decrease exponentially with increasing temperature. A model derived from excess Gibbs free energy was fitted to the observations with an R2 = 99.6% and RMSE = 0.01 (aw). Our results suggest that the sharply reduced water activity of oil resulting from a rise in temperature could cause desiccation of bacteria. This is a possible explanation for the protective effect of oil in thermal processing.

Mobility of ß-Lactam Resistance Under Bacterial Co-infection and Ampicillin Treatment in a Mouse Model.

Ingestion of food- or waterborne antibiotic-resistant bacteria may lead to the dissemination of antibiotic-resistance genes in the gut microbiota and the development of antibiotic-resistant bacterial infection, a significant threat to animal and public health. Food or water may be contaminated with multiple resistant bacteria, but animal models on gene transfer were mainly based on single-strain infections. In this study, we investigated the mobility of ß-lactam resistance following infection with single- versus multi-strain of resistant bacteria under ampicillin treatment. We characterized three bacterial strains isolated from food-animal production systems, Escherichia coli O80:H26 and Salmonella enterica serovars Bredeney and Heidelberg. Each strain carries at least one conjugative plasmid that encodes a ß-lactamase. We orally infected mice with each or all three bacterial strain(s) in the presence or absence of ampicillin treatment. We assessed plasmid transfer from the three donor bacteria to an introduced E. coli CV601gfp recipient in the mouse gut, and evaluated the impacts of the bacterial infection on gut microbiota and gut health. In the absence of ampicillin treatment, none of the donor or recipient bacteria established in the normal gut microbiota and plasmid transfer was not detected. In contrast, the ampicillin treatment disrupted the gut microbiota and enabled S. Bredeney and Heidelberg to colonize and transfer their plasmids to the E. coli CV601gfp recipient. E. coli O80:H26 on its own failed to colonize the mouse gut. However, during co-infection with the two Salmonella strains, E. coli O80:H26 colonized and transferred its plasmid to the E. coli CV601gfp recipient and a residential E. coli O2:H6 strain. The co-infection significantly increased plasmid transfer frequency, enhanced Proteobacteria expansion and resulted in inflammation in the mouse gut. Our findings suggest that single-strain infection models for evaluating in vivo gene transfer may underrepresent the consequences of multi-strain infections following the consumption of heavily contaminated food or water.

A biosecure composting system for disposal of cattle carcasses and manure following infectious disease outbreak.

During outbreaks of infectious animal diseases, composting may be an effective method of disposing of mortalities and potentially contaminated manure. Duplicate biosecure structures containing 16 cattle (Bos taurus) mortalities (343 kg average weight) were constructed with carcasses placed on a 40-cm straw layer and overlaid with 160 cm of feedlot manure. At a depth of 80 cm (P80), compost heated rapidly, exceeding 55 degrees C after 8 d and maintained temperatures of 55 to 65 degrees C for > 35 d. Temperatures at 160 cm (P160) failed to exceed 55 degrees C, but remained above 40 degrees C for >4 mo. To investigate rates of microbial inactivation, Escherichia coli O157:H7, Campylobacter jejuni, and Newcastle disease virus (NDV) were inoculated in manure (E. coli O157:H7 and C. jejuni approximately 10(8) CFU g(-1); NDV, approximately 10(6) EID(50) g(-1)), embedded at P80 and P160 and retrieved at intervals during composting. Escherichia coli O157:H7 and NDV were undetectable after 7 d at both depths. The C. jejuni DNA was detected up to 84 d at P80 and >147 d at P160. To estimate degradation of recalcitrant substrates, bovine brain, hoof, and rib bones were also embedded at P80 and P160 and retrieved at intervals. Residues of soft tissues remained in carcasses after opening at 147 d and bovine tissue decomposition ranked as brain > hoof > bone. More than 90% dry matter (DM) of brain disappeared after 7 d and 80% DM of hoof decomposed after 56 d. High degradation of cattle carcasses, rapid suppression of E. coli O157:H7 and NDV and reduction in viable cell densities of >6 logs for C. jejuni demonstrates that the biosecure composting system can dispose of cattle carcasses and manure in an infectious disease outbreak.

Aerosol exposure enhanced infection of low pathogenic avian influenza viruses in chickens.

To assess the impact of different routes of inoculation on experimental infection of avian influenza (AI) viruses in chickens, this study compared virus replication and cytokine gene expression in respiratory and gastrointestinal organ tissues of chickens, which were inoculated with four low pathogenic subtypes, H6N1, H10N7, H10N8, and H13N6 AI viruses via the aerosol, intranasal, and oral routes respectively. Aerosol inoculation with the H6N1, H10N7, and H10N8 viruses significantly increased viral titres and upregulated the interferon (IFN)-γ, interleukin (IL)-6, and IL-1ß genes in the trachea and lung tissues compared to intranasal or oral inoculation. Furthermore, one or two out of six chickens died following exposure to aerosolized H6N1 or H10N8 virus respectively. The H13N6 virus reached the lung via aerosol inoculation although failed to establish infection. Collectively, chickens were more susceptible to aerosolized AI viruses compared to intranasal or oral inoculation, and virus aerosols might post a significant threat to poultry health.

H9N2 avian influenza virus retained low pathogenicity after serial passage in chickens.

The H9N2 strains of avian influenza viruses (AIVs) circulate worldwide in poultry and cause sporadic infection in humans. To better understand the evolution of these viruses while circulating in poultry, an H9N2 chicken isolate was passaged 19 times in chickens via aerosol inoculation. Whole-genome sequencing showed that the viruses from the initial stock and those after the 8th and 19th passages (P0, P8, and P19) all had the same monobasic cleavage site in the hemagglutinin (HA), typical for viruses of low pathogenicity. However, at position 226 of the HA protein the ratio of glutamine (which favors avian-type receptor binding) to leucine (which favors mammalian-type receptor binding) decreased from 54:46 in P0, to 87:13 in P8, and then 0:100 in P19. In chickens exposed to aerosols of P0, P8, or P19, replication of the viruses was similar and mainly limited to the respiratory tract. None of the infected chickens showed any clinical signs. Over the 19 passages the viruses maintained relatively stable infectivity but gradually lost lethality to chicken embryos. According to the hemagglutination inactivation assay, P8 was slightly and P19 significantly (P < 0.05) less thermostable than P0. Collectively, after 19 passages in chickens the H9N2 AIVs retained low pathogenicity with a positive selection of L226 in the HA. These findings suggest that H9N2 viruses might acquire mammalian specificity after asymptomatic circulation in avian species.

Les souches H9N2 du virus de l'influenza aviaire (VIA) circulent mondialement parmi la volaille et causent des infections sporadiques chez l'humain. Afin de mieux comprendre l'évolution de ces virus alors qu'ils circulent parmi la volaille, un isolat H9N2 de poulet a été passé 19 fois chez des poulets via inoculation par aérosol. Le séquençage du génome complet a démontré que les virus de l'approvisionnement initial et ceux après le 8e et le 19e passages (P0, P8, et P19) avaient tous le même site de clivage monobasique dans l'hémagglutinine (HA), typique des virus de faible pathogénicité. Toutefois, à la position 226 de la protéine HA le ratio de glutamine (qui favorise l'adhésion aux récepteurs de type aviaire) à leucine (qui favorise l'adhésion aux récepteurs de type mammalien) a diminué de 54:46 à P0, à 87:13 à P8, et à 0:100 à P19. Chez des poulets exposés à des aérosols provenant de P0, P8, ou P19, la réplication des virus était similaire et principalement limitée au tractus respiratoire. Aucun des poulets infectés n'a montré de signes cliniques. Sur l'ensemble des 19 passages les virus ont maintenu un pouvoir infectant relativement stable mais ont graduellement perdu leur capacité létale pour les embryons de poulets. En fonction des résultats de l'épreuve d'inactivation de l'hémagglutination, P8 était légèrement et P19 significativement (P < 0,05) moins thermostable que P0. De manière globale, après 19 passages chez des poulets les VIA H9N2 ont maintenu une faible pathogénicité avec sélection positive de L226 dans l'HA. Ces résultats suggèrent que les virus H9N2 pourraient acquérir une spécificité mammalienne après circulation asymptomatique dans les espèces aviaires.(Traduit par Docteur Serge Messier).

Detection of multiple antibiotic-resistant Salmonella enterica serovar Typhimurium DT104 by phage replication-competitive enzyme-linked immunosorbent assay.

A phage replication-competitive enzyme-linked immunosorbent assay (PR-cELISA) was developed for the detection of multiple antibiotic-resistant Salmonella Typhimurium DT104. In the PR-cELISA procedure, a phage, BP1, was inoculated into a log-phase bacterial culture at a ratio of 1:100. After a 3-h incubation of the mixture, BP1 replication was measured by cELISA based on the competitive binding between BP1 and biotinylated BP1 to Salmonella Typhimurium smooth lipopolysaccharide. Among the 84 Salmonella strains and 9 non-Salmonella strains that were tested by PR-cELISA, BP1 detected 39 of 40 Salmonella Typhimurium strains, 2 of 10 Salmonella non-Typhimurium somatic group B strains, and 5 of 18 Salmonella somatic group D1 strains. With the addition of chloramphenicol to the culture medium, PR-cELISA detected all 27 multiple antibiotic-resistant Salmonella Typhimurium DT104 and none of the other Salmonella strains or non-Salmonella strains tested. The results demonstrated that PR-cELISA has potential applications for the detection of multiple antibiotic-resistant Salmonella Typhimurium DT104.