A diplococcus (plural diplococci) is a round bacterium (a coccus) that typically occurs in the form of two joined cells. Examples of gram-negative diplococci are Neisseria sp., Haemophilus, Moraxella catarrhalis, Acinetobacter, and Brucella. Examples of gram-positive diplococci would be Streptococcus pneumoniae and enterococcus.