The bacteria of the genus Klebsiella, of omnipresent nature, are many and very different among them. In general, they are Gram negative, therefore, quite similar to E. coli, potentially pathogenic and opportunistic. Man represents a model host organism in which bacteria of the genus Klebsiella live physiologically without causing infection as in the colon and upper respiratory tract. However, in immunosuppressed individuals or with chronic debilitating diseases, Klebsiella bacteria can easily establish important infectious phenomena, especially in the respiratory tract, in the blood and in the urinary tract with the formation of particularly aggressive resistant antibiotic strains, especially when Infections are contracted in the hospital or in medical clinics. Although the symptoms of urinary tract infections caused by Klebsiella are clinically indistinguishable from those caused by other pathogens, it is necessary to pay special attention in these cases, especially in catheterized individuals. In this sense, especially when the local and systemic symptoms, burning and pain in the bladder, are accompanied by fever, chills, pain when urinating, it will be crucial to make a urine culture to determine the specific cause, before the infection rises to the kidneys and may trigger dangerous pyelonephritis.