Appendix C

Differentiation of Bacterial Cultures based on Morphological and Physiological Characteristics

Group 1: Aerobic and Anaerobic Cocci

Table 1. Aerobic cocci.
Gram stain Arrangement
Micrococcus spp. + tetrads
Neisseria gonorrhoeae – diplococci
Table 2. Anaerobic cocci.
Catalase Oxidase Arrangement Oxygen
Staphylococcus spp (see Table 1) + – clusters Facultative anaerobe
Streptococcus spp.

(see Table 4)

 – – chains Aerotolerant anaerobe
Enterococcus spp.

(see Table 4)

 – – chains Aerotolerant anaerobe
Table 3. Differentiation of Staphylococcus spp.
Staphylococcus aureus Staphylococcus epidermidis Staphylococcus saprophyticus
Coagulase 4+ – 1–2+
Mannitol Salt Agar + – +
Urease – or wk+ + +
Hemolysis Beta (β) – or wk + –
Novobiocin resistance Susc. (-) Susc. (-) Res. (+)
Table 4. Differentiation of Streptococcus and Enterococcus spp.
Streptococcus pyogenes Enterococcus faecalis
Hemolysis on BAP Beta (β) Gamma (γ)
Bile Esculin No growth (-) Growth/black (+)

Group 2: Aerobic and Facultatively Anaerobic Bacilli

Gram positive bacilli

Endospore forming: Bacillus spp. (see Table 5)

Non-endospore forming: Corynebacterium xerosis

Table 5. Differentiation of Bacillus spp.
Endospore shape, location, sporangium
B. cereus Oval, central, sporangium not swollen
B. lentus Oval, terminal, sporangium swollen

Gram negative bacilli

Strictly aerobic: Pseudomonas aeruginosa

Facultatively anaerobic: Enterobacteriaceae (see Table 6)

Table 6. Differentiation of Enterobacteriaceae
TSI Sulfide/Indole/Motility Methyl Red VP Citrate
Escherichia coli A/A – /+/+ + – –
Enterobacter aerogenes A/A -/-/+ – + +
Citrobacter freundii A/A -/-/+ + – +
Klebsiella pneumoniae A/A -/-/- – + +
Salmonella enteritidis K/A +/-/+ + – +