Epidemiology, Virulence Factors, and Antibacterial Resistance of Klebsiella spp.: The Known Unknowns

<i>Klebsiella</i> spp. are among the most prominent bacteria in nature and can be found in different environments, including soil, vegetation, and surface waters. The most important species of the <i>Klebsiella</i> genus is <i>Klebsiella pneumoniae</i>, which is recognized as an alarming opportunistic pathogen responsible for approximately 70% of human infections within their family. Due to their evolving hypervirulence and antimicrobial resistance, there is an increasing amount of research about the trends and mechanisms of virulence factors and epidemiology. Understanding pathogenetic mechanisms is important to advance diagnostic methods and treatment. In this review, we aim to summarize the available information and recent development in research of <i>Klebsiella</i> spp., specifically focusing on the trends in epidemiology, virulence factors, and the development of antimicrobial resistance.