Aerobic Microorganisms

Question 1

Gram-positive cocci in clusters (gram stain positive)

Answer 1

Staphylococcus spp.
Coagulase-positive: S. aureus
Coagulase-negative: S. epidermidis, S. lugdunensis, S. hominis, S. saprophyticus, S. haemolyticus, S. capitis

Question 2

Gram-positive cocci in pairs (gram stain positive)

Answer 2

Streptococcus pneumoniae

Question 3

Gram-positive cocci in chains (gram stain positive)

Answer 3

Viridans streptococci (α-hemolytic): S. milleri, S. mutans, S. salivarius, S.  mitis, S. sanguis 
Group streptococci (β-hemolytic): Group A (S. pyogenes), Group B (S.  agalactiae), Group C (Streptococcus equi), Group D (S. bovis, S. equinus),  Groups F and G streptococci (S. dysgalactiae)

Question 4

Gram-positive cocci in pairs & chains (gram stain positive)

Answer 4

Enterococcus spp. (E. faecalis, E. faecium, E. durans, E. gallinarum, E. avium, E casseliflavus, E. raffinosus)

Question 5

Non-spore-forming

Gram-positive bacilli

Answer 5

Corynebacterium spp. (C. diphtheriae, C. jeikeium, C. striatum, etc.) Lactobacillus spp.
Listeria monocytogenes

Question 6

Spore-forming

Gram-positive bacilli

Answer 6

Bacillus spp. (B. anthracis, B. cereus, etc.)

Streptomyces spp.

Question 7

Branching, filamentous

Gram-positive bacilli

Answer 7

Erysipelothrix rhusiopathiae

Nocardia spp. (N. asteroides)

Question 8

Gram-negative cocci

Answer 8

Neisseria spp. (N. gonorrhoeae, N. meningitidis, etc.)

Moraxella catarrhalis

Question 9

Gram-negative coccobacilli

Answer 9

Haemophilus spp. (H. influenzae, H. parainfluenzae, H. ducreyi, etc.)

Question 10

Lactose-fermenting

Gram-negative bacilli

Answer 10

Aeromonas hydrophila
*Citrobacter spp. (C. freundii, C. koseri)
*Enterobacter spp. (E. cloacae, E. aerogenes [Klebsiella aerogenes]) *Escherichia coli
*Klebsiella spp. (K. pneumoniae, K. oxytoca)
Pasteurella multocida
Vibrio cholerae

Question 11

Non-lactose-fermenting

Gram-negative bacilli

Answer 11

Acinetobacter spp. (A. baumannii)
Alcaligenes spp.
Burkholderia cepacia
*Morganella morganii
*Proteus spp. (P. mirabilis, P. vulgaris)
*Providencia spp. (P. rettgeri, P. stuartii)
Pseudomonas spp. (P. aeruginosa, P. putida, P. fluorescens) *Salmonella spp. (S. typhi, S. paratyphi, S. enteritidis, S. typhimurium) *Serratia marcescens
*Shigella spp. (S. dysenteriae, S. sonnei)
Stenotrophomonas maltophilia

Question 12

Other Gram-negative bacilli

Gram-negative bacilli

Answer 12

Brucella spp. 
Bordetella spp. 
Campylobacter jejuni 
Francisella tularensis 
Helicobacter pylori

Question 13

Miscellaneous organisms where Gram stain is typically not useful
___________________________________________
ATYPICAL BACTERIA
(Cell walls difficult to stain; Mycoplasma lack a cell wall)
___________________________________________
SPIROCHETES
(Motile, corkscrew-shaped organism visualized using dark field microscopy)

Answer 13

Chlamydophila pneumoniae 
Chlamydia trachomatis 
Legionella pneumophila 
Mycoplasma pneumoniae 
\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
Treponema pallidum (syphilis) 
Borrelia burgdorferi (Lyme disease) 
Leptospira interrogans

Question 14

Gram-variable bacilli

Answer 14

Gardnerella vaginalis