<div><strong>Background:</strong> <em>Riemerella anatipestifer</em> (<em>R. anatipestifer</em>) is a gram negative, microaerophilic, non-motile, bipolar bacteria. High genetic diversity and molecular differentiation were reported among field isolates. Although the bacterium causes one of the most economically important duck diseases in the north-eastern region of India, little work has been done on isolation, identification and molecular characterization of the bacteria. Hence, the present investigation was undertaken with a view to characterize the <em>R. anatipestifer</em> isolates from ducks of Assam.</div>

<div><br />
<strong>Methods:</strong> Phenotypic and molecular identification of <em>R. anatipestifer </em>isolates from domesticated ducks of Assam, India were carried out during the period from February, 2019 to January 2020. A total of 624 samples (Ocular swab, throat swab, liver, spleen, kidney, brain, heart, lung) from ducks comprising of apparently healthy, ailing and dead ducks were collected from five districts of Assam, India were processed to isolate and identify the bacteria. The tentative identification of the bacteria was done based on phenotypic characteristics <em>viz.</em>, colony morphology, growth characteristics and biochemical reactions. All the phenotypically positive isolates were further subjected to molecular identification based on PCR assay targeting<em> 16S rRNA </em>gene and ERIC sequence.<br />
<br />
&nbsp;</div>

<div><strong>Result:</strong> The bacteria could be isolated from different field samples. The highest percentage of the samples that yielded the bacteria are from brain (76%) followed by spleen (74%) of dead ducks and less number of ocular swab (33%) from apparently healthy ducks were found positive. Sequencing of the amplified product of the selected <em>R. anatipestifer </em>isolates targeting 16S <em>rRNA</em> gene revealed homology percentage of 96.5-100%. Further, sequences representing five geographical locations were submitted to NCBI gene bank. Phylogenetic studies of the isolates indicated that there is prevalence of at least two genetically different strains of <em>R. anatipestifer</em> in the study area. The study suggested that the <em>R. anatipestifer</em> infection is endemic in Assam causing varying rate of morbidity (39%) and mortality (53%) and molecular based confirmation is necessary besides phenotypic identification.</div>


<div>Isolation and Molecular Characterization of <em>Riemerella anatipestifer</em> from Domesticated Ducks of Assam, India</div>


<div><strong>Background: </strong>Among the various bacterial pathogens P. multocida and R. anatipestifer cause varying degrees of mortality and morbidity leading to huge economic losses among the duck farming community. Considering the lack of information regarding the characterization of <em>P. multocida </em>and <em>R. anatipestifer</em>, a study was undertaken to establish the prevalence of these diseases in ducks from different parts of Assam, together with the capsular and virulence-associated gene characterization and antimicrobial resistance.&nbsp;<br />
<br />
<strong>Methods:</strong> A total of 235 samples comprising lungs, tracheal swabs, livers, heart blood and spleens collected from 47 diseased ducks, were screened for <em>P. multocida </em>and <em>R. anatipestife</em>r. The capsular and virulence-associated genes were amplified in isolated strains. The resistance pattern towards commonly used antimicrobial agents was studied by the disc diffusion method.<br />
<br />
<strong>Result: </strong>The prevalence of duck septicemia and new duck disease was confirmed in ducks of Assam, India. Molecular tools were found to be highly specific besides phenotypic-based approaches in the detection, confirmation and differentiation of both bacteria due to phenotypic similarity. The antibiotic resistance patterns of both bacteria revealed a varying degree of sensitivity toward different antibiotics.</div>


Isolation and Molecular Characterization of Riemerella anatipestifer from Domesticated Ducks of Assam, India

Characterization of Pasteurella multocida and Riemerella anatipestifer of Ducks in Assam, India