Mucoviscosity of cohorts of classical K. pneumoniae (cKp) strains, partially virulent hypervirulent K. pneumoniae (pvhvKp) strains, and fully virulent hypervirulent K. pneumoniae (fvhvKp) strains. Bacterial strains were grown in either lysogeny broth (LB) or iron-chelated M9 minimal medium plus added trace elements (c-M9-te). The culture OD600 was normalized to 1.0 and then centrifuged at 1,000 × g for 5 min. Mucoviscosity was recorded as the post/prespin OD600 ratio. (A) cKp strain cohort; (B) pvhvKp strain cohort; (C) fvhvKp strain cohort; (D) all cohorts grown in LB; (E) all cohorts grown in c-M9-te. The horizontal line marks 0.15. Three independent assays were performed on different days for each strain, and the data were reported as means ± SD. ****, P < 0.0001 by two-way ANOVA.