<i>Klebsiella pneumoniae</i> : Prevalence, Reservoirs, Antimicrobial Resistance, Pathogenicity, and Infection: A Hitherto Unrecognized Zoonotic Bacterium

Abstract

<i>Klebsiella pneumoniae</i> is considered an opportunistic pathogen, constituting an ongoing health concern for immunocompromised patients, the elderly, and neonates. Reports on the isolation of <i>K. pneumoniae</i> from other sources are increasing, many of which express multidrug-resistant (MDR) phenotypes. Three phylogroups were identified based on nucleotide differences. Niche environments, including plants, animals, and humans appear to be colonized by different phylogroups, among which KpI (<i>K. pneumoniae</i>) is commonly associated with human infection. Infections with <i>K. pneumoniae</i> can be transmitted through contaminated food or water and can be associated with community-acquired infections or between persons and animals involved in hospital-acquired infections. Increasing reports are describing detections along the food chain, suggesting the possibility exists that this could be a hitherto unexplored reservoir for this opportunistic bacterial pathogen. Expression of MDR phenotypes elaborated by these bacteria is due to the nature of various plasmids carrying antimicrobial resistance (AMR)-encoding genes, and is a challenge to animal, environmental, and human health alike. Raman spectroscopy has the potential to provide for the rapid identification and screening of antimicrobial susceptibility of <i>Klebsiella</i> isolates. Moreover, hypervirulent isolates linked with extraintestinal infections express phenotypes that may support their niche adaptation. In this review, the prevalence, reservoirs, AMR, Raman spectroscopy detection, and pathogenicity of <i>K. pneumoniae</i> are summarized and various extraintestinal infection pathways are further narrated to extend our understanding of its adaptation and survival ability in reservoirs, and associated disease risks.