Introduction of a novel tellurite-containing selective mediumfor the rapid phenotypic identification method of hypervirulentKlebsiella pneumoniae isolates

Background and Aim : Klebsiella pneumoniae has two pathotypes circulating worldwide: classicK. pneumoniae (cKp) and hypervirulent K.pneumoniae (hvKP) strains. hvKps due to theexpression of multiple virulence factors has increased the mortality and complications ofK.pneumoniae infections. So far, the string test method used for phenotypic identification ofhvKps showed low sensitivity and accuracy. Therefore, the aim of this study is to use a methodbased on the resistance of hvKps to potassium tellurite to design a rapid screening method that hashigher accuracy and sensitivity than the string test.Methods : we collected ۴۷۷ non-repetitive K.pneumoniae as clinical isolates from two educationalhospitals. The hypermucoviscous phenotype of the hvKp isolates was examined by the string test.Since most hvKp isolates carry tellurite resistance genes located on virulence plasmid, they areable to reduce tellurite and form a black colony. Therefore, in this study, we used telluritecontainingselective medium as a rapid screening test. Finally, we evaluated and compared twophenotypic methods using the hvKp molecular identification marker (PCR the aerobactin gene iuc,and iut).Results : In this study, out of ۴۷۷ K. pneumoniae isolates, ۱۶۳ isolates (۳۴.۲%) were telluriteresistantK. pneumoniae isolates, while ۶۲ of the ۴۷۷ K. pneumoniae isolates (۱۳%) were reportedwith positive string test and hypermucoviscous phenotype. So they were selected for the molecularidentification test. In the PCR method ۶۲.۶% (۱۰۲/۱۶۳) of tellurite-resistant were hvKp and ۴۸%(۴۹/۱۰۲) hvKp isolates showed string test positive.Conclusion : This study showed that resistance to tellurite is strongly associated with hvKpisolates. It seems that most of the large virulence plasmids in hvKps carry tellurite resistance genes.Therefore, this method was found to be superior to the string test for rapid phenotypic hvKpdetection

کلیدواژه ها:

Hypervirulent Klebsiella pneumonia ، rapid phenotypic identification method ، tellurite-resistant ، string test ، PCR