K pneumoniae is an opportunistic pathogens found in the environment and in mammalian mucosal surfaces. The principal pathogenic reservoirs of infection are the gastrointestinal tract of patients. K pneumonia is known pathogen leading to nosocomial outbreaks.
Acinetobacter species are Gram-negative organisms commonly found in the environment. Although previously considered to be relatively avirulent, the Acinetobacter calcoaceticus-baumanii complex is emerging as a problematic, multidrug-resistant, nosocomial and community-acquired pathogen.
Pseudomonas aeruginosa is a common bacterium found in soil and water. Pseudomonas aeruginosa has become an important cause of infection, especially in patients with compromised host defense mechanisms. It is a frequent cause of nosocomial infections such as pneumonia, urinary tract infections (UTIs)
E. coli are Gram-negative organisms commonly found in the lower intestine of warm blooded animals. Although most E.coli strains are harmless some serotypes can cause serious life threatening infections.