1. Gram-negative
1.1. Cocci
1.1.1. Aerobes / Facultative anaerobes
1.1.1.1. Monococci
1.1.1.1.1. Haemophilus influenzae
1.1.1.1.2. Bordetella pertussis
1.1.1.1.3. Brucella spp.
1.1.1.2. Diplococci
1.1.1.2.1. Neisseria meningitis
1.1.1.2.2. Neisseria gonorrhoeae
1.1.1.2.3. Moraxella catarrhalis
1.2. Rods
1.2.1. Aerobes
1.2.1.1. Pseudomonas aeruginosa
1.2.1.2. Vibrio cholerae
1.2.1.3. Campylobacter spp.
1.2.1.4. Bartonella spp.
1.2.2. Anaerobes
1.2.2.1. Bacteroides spp.
1.2.2.2. Fusobacteria spp.
1.2.3. Facultative anaerobes
1.2.3.1. Enterobacteriaciae
1.2.3.1.1. Lactose fermenting
1.2.3.1.2. Non-lactose fermenting
1.2.3.2. Proteus spp.
1.2.3.3. Serratia spp.
1.2.3.4. Yersinia spp.
2. Gram-positive
2.1. Cocci
2.1.1. Aerobes / Facultative anaerobes
2.1.1.1. Catalase positive
2.1.1.1.1. Staphylococci
2.1.1.2. Catalase negative
2.1.1.2.1. Grow in chains
2.1.1.2.2. Grow in pairs
2.2. Rods
2.2.1. Aerobes
2.2.1.1. Bacillus cereus
2.2.1.2. Bacillus anthracis
2.2.1.3. Listeria monocytogenes
2.2.2. Anaerobes
2.2.2.1. Clostridium spp.
2.2.2.2. Actinomyces spp.
2.2.3. Facultative anaerobes
2.2.3.1. Corynebacterium diphtheriae
3. Other
3.1. Intracellular
3.1.1. Chlamydia spp.
3.1.2. Rickettsia spp.
3.1.3. Borrelia spp.
3.2. Poorly-staining
3.2.1. Mycobacterium tuberculosis
3.2.2. Legionella spp.
3.2.3. Helicobacter pylori
3.3. Acid-fast
3.3.1. Mycoplasma spp.
3.3.2. Nocardia spp.