ABSTRACT Despite the increasing number of reports on hypervirulent and extended-spectrum β-lactamase (ESBL)-producing Klebsiella pneumoniae infections, data on the distribution of these pathogens in the community are limited. To address this knowledge gap, we investigated the carriage rates of K. pneumoniae complex in the stools of community-dwelling individuals in Japan. From 627 stool samples submitted to a commercial diagnostic laboratory, 407 Klebsiella strains were identified from 368 samples, corresponding to a colonization rate of 58.7%. Based on whole-genome sequencing, K. pneumoniae was the most prevalent species ( n = 218, 53.6%), followed by Klebsiella variicola ( n = 137, 33.7%). The detection rate of K. variicola was higher than previously reported in studies from other Asian countries. The overall distribution of sequence types (STs) was similar to those observed in previous studies of clinical isolates. However, hypervirulent K. pneumoniae clones, specifically ST23-K1 and ST412-K57, and ESBL-producing strains were rare, each accounting for less than 1% of the strains. These findings suggest that, while carriage of K. pneumoniae complex species is common in the community, healthcare settings may represent a more significant reservoir of hypervirulent and ESBL-producing K. pneumoniae strains in this epidemiological setting. IMPORTANCE Klebsiella pneumoniae complex species are bacteria that can cause serious infections, especially in hospital settings. Some types have become more dangerous because they are resistant to antibiotics or highly virulent. To better understand where these harmful clones come from, this study looked for Klebsiella species in healthy people living in the community in Japan. The results showed that these bacteria are commonly found in the gut, particularly K. pneumoniae and K. variicola . While some strains with traits linked to antibiotic resistance or severe infections were identified, they were rare. These findings suggest that most people carry Klebsiella strains as commensals and that the more dangerous forms of Klebsiella are likely spreading mainly in healthcare settings.
Watanabe et al. (Wed,) studied this question.