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 +/-/+ + +


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