ABSTRACT
Gram-negative bacteria do not retain the crystal violet stain during classical Gram staining methods to differentiate between bacterial pathogens. Gram-negative bacteria do not follow a monophyletic, phylogenetic pattern, and thus, the designation is primarily of importance in the determination of which antimicrobial to use when treating bacterial infections. This chapter briefly discusses species of the following Gram-negative genera in the phylum Proteobacteria: Acinetobacter, Burkholderia, and Moraxella. Species outside of the Acb complex, including Acinetobacter ursingii, have also been associated with nosocomial infection. The most clinically important species of this genus is Moraxella catarrhalis, which originally was thought of as a commensal of the upper respiratory tract but, as of late, has been identified to cause disease of the eye, ear, and sinus in children. The Acinetobacter , Burkholderia , and Moraxella genera contain a mix of important human pathogens and environmental bacteria.
