Background: Klebsiella pneumoniae which are commonly recognized in laboratory are termed as classical K. pneumoniae (cKP). A new strain of K. pneumoniae named hypermucoviscous K. pneumoniae (hmvKP) emerging with a distinctive feature than classical strains. Our study aimed to determine the prevalence of hypermucoviscous K. pneumoniae in our hospital and their phenotypic comparison with the classical strains.Methods : This laboratory-based cross-sectional study done from February to July 2018,

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... the Department of Microbiology, Manmohan Memorial Teaching Hospital, Kathmandu, Nepal. One hundred and five clinical non-duplicative isolates of K. pneumoniae proceeded for the study. Hypermucoviscosity of isolated K. pneumoniae were tested by standard String test. Antibiotic susceptibility was determined by the Kirby-Bauer disk diffusion method according to Clinical and Laboratory Standards Institute (CLSI) guidelines. Further β-lactamases (ESBL, MBL, and KPC) were detected by the phenotypic combination disk test method. Serum resistance and biofilm production were determined to assess their virulence.Results: A total of one hundred five non-repetitive pure and microbiologically identified K. pneumoniae were taken for study. Among the isolated K. pneumoniae, 29 (27.6%) were hypermucoviscous K. pneumoniae (hmvKP) and 76(72.4%) were classical K. pneumoniae (cKP) determined by string test. The majority of K. pneumoniae were resistant to ceftazidime (80%) and cefotaxime (78%) whereas all the isolates were found susceptible to polymyxin b and colistin. Extended spectrum beta lactamase (ESBLs) production, Metallo-beta lactamase (MBL), Klebsiella pneumoniae carbapenemase (KPC) production, biofilm, and serum resistance were compared among classical and hypermucoviscos strains and the hypermucoviscous strains revealed significantly higher expression of virulence than classical strainsConclusion: The expression of virulence factors and antimicrobial resistance was found significantly higher among the hypermucoviscous strains when phenotypically compared. The prevalence of these hypermucoviscous strains in hospital settings may increase the risk of morbidity and mortality. Therefore, timely diagnosis and appropriate treatment strategies are crucial.