Definition
The *genus Klebsiella* comprises Gram-negative bacteria known for causing various infections. These bacteria are commonly found in the environment and in human intestines. *Klebsiella pneumoniae* is a significant species, known for causing pneumonia and bloodstream infections, especially in healthcare settings. Think of *Klebsiella* as a family of bacteria that are generally opportunistic, meaning they take advantage of weakened immune systems. It's similar to a gate-crasher, sneaking in when the party's security is down. While some species are harmless, others can be quite dangerous, particularly to vulnerable individuals.