Klebsiella pneumoniae (KP) represents one of the main causative agents of opportunistic infections. KP associated infectious diseases can be local, for example, pneumonia, and generalized, including severe, often life-threatening conditions (meningitis, sepsis). Besides the chromosomal genome with a variety of different genetic loci, KP contains an additional plasmid genome which endues it with important biological properties. That’s why KP strains can be opportunistic, hypervirulent, and resistant to antimicrobials. In this literature review, literature data on the molecular resistant mechanisms, virulence factors and infectious diseases caused by KP is discussed.