One of the most concerning antibiotic resistance is that against the last resort
antibiotic, the carbapenems. Carbapenemase are a diverse class of enzymes that mediates
carbapenem resistance. Which hydrolyze, not just carbapenem, but others of different classes as well. The two main clones of carbapenemase producers of Klebsiella
pneumoniae are ST11 and ST307 in South Korea.
In our recent study, we characterized and compared the virulence of two main clones of K. pneumoniae isolates from South Korea, ST11 and ST307, including carbapenem-resistant and -susceptible isolates. Although the two clones did not show a difference in virulence with respect to serum resistance and macrophage infection, the ST11
isolates demonstrated diverse features compared to ST307 (figure 1A). Meanwhile, ST307 isolates exhibited homogeneous features and a similar virulence level as that of the wzi14-type ST11 isolates (figure 1 and 2). Among ST11 a particular serotype, wzi14, showed
higher virulence than other serotypes of the clone (figure 1B). All five wzi14-type ST11
isolates contained ybtS, three of which possessed additional virulence genes rmpA2 and iutA. Although the high virulence with respect to serum resistance and macrophage internalization would be responsible for the feature of the capsule in K. pneumoniae, the presence of more virulence genes also contributes to the pathogenicity of the isolates. In our
analysis, the ybtS-positive isolates had higher serum resistance-related virulence than that
of the ybtS-negative isolates (figure 3A and B). Thus, highlighting the importance of wzi14-type and ybtS in virulence of K. pneumoniae ST11 and ST307 of both carbapenem resistant and susceptible clinical isolates. This study further suggests the prolonged
existence and dissemination of ST11 and the relativily recent introduction of ST307 as
high-risk K. pneumoniae clone.