Gram Stains of Medically Significant Bacteria

Question 1

Staphylococcus aureus

Answer 1

Gram-positive cocci in clusters

Question 2

Staphylococcus epidermidis

Answer 2

Gram-positive cocci in clusters

Question 3

Staphylococcus saprophyticus

Answer 3

Gram-positive cocci in clusters

Question 4

Streptococcus pyogenes,

Answer 4

Gram-positive coccus in chains

Question 5

Group B Streptococcus

Answer 5

Gram-positive coccus in chains

Question 6

Streptococcus pneumoniae

Answer 6

Gram-positive coccus in pairs

Question 7

Enterococcus faecalis

Answer 7

Gram-positive cocci in chains

Question 8

Vibrio cholerae

Answer 8

Gram-negative bacillus, curved

Question 9

Vibrio parahemolyticus

Answer 9

Gram-negative bacillus, curved

Question 10

Vibrio vulnificus

Answer 10

Gram-negative bacillus, curved

Question 11

Campylobacter jejuni

Answer 11

Gram-negative bacillus, thin curved rods, occasional “s” or gull wing shapes

Question 12

Helicobacter pylori

Answer 12

Curved gram-negative bacillus

Question 13

Salmonella

Answer 13

Gram-negative bacillus

Question 14

Enteric Fever (Typhoid fever) — Salmonella Typhi & Paratyphi

Answer 14

Gram-negative bacillus

Question 15

Shigella

Answer 15

Gram-negative bacillus; member of the family Enterobacteriaceae

Question 16

Escherichia coli

Answer 16

Gram-negative bacillus

Question 17

Enterotoxic E. coli

Answer 17

Gram-negative bacillus

Question 18

Shiga Toxin-producing E.coli (

Answer 18

Gram-negative bacillus

Question 19

Enterohemorrhagic E. coli

Answer 19

Gram-negative bacillus

Question 20

Yersinia enterocolitica

Answer 20

Gram-negative bacillus (Family Enterobacteriaceae)

Question 21

Yersinia pestis

Answer 21

Gram-negative bacillus

Question 22

Legionella pneumophila

Answer 22

Gram-negative bacillus, pleomorphic, stains poorly; culture challenges

Question 23

Pseudomonas aeruginosa

Answer 23

Gram-negative bacilli

Question 24

Acinetobacter baumannii

Answer 24

Gram-negative bacillus, grows on MacConkey

Question 25

Brucella melitensis & B. abortus

Answer 25

Small Gram-negative coccobacillus, very slow growing

Question 26

Francisella tularensis

Answer 26

Very small Gram-negative bacillus; grows poorly in standard culture media

Question 27

Bordetella pertussis

Answer 27

Gram-negative bacillus (cocco-bacillus) (GNB, GNCB )

Question 28

Haemophilus influenzae

Answer 28

Gram-negative coccobacillus (very small, short rod)

Question 29

Haemophilus ducreyi

Answer 29

Gram-negative coccobacillus

Question 30

Moraxella catarrhalis (formerly Branhamella catarrhalis)

Answer 30

Gram-negative cocci in pairs

Question 31

Neisseria meningitidis

Answer 31

Gram-negative cocci in pairs

Question 32

Neisseria gonorrhoeae

Answer 32

Gram-negative cocci in pairs

Question 33

Chlamydia trachomatis

Answer 33

Very small, unusual, atypical gram-negative bacteria (not realistic to observe via Gram stain)

Question 34

Chlamydia pneumoniae

Answer 34

Very small, unusual, atypical gram-negative bacteria (not realistic to observe via Gram stain)

Question 35

Mycoplasma pneumoniae

Answer 35

Atypical bacterium -- no cell wall, small, poorly staining

Question 36

Rickettsia and Orientia species

Answer 36

"Atypical" bacteria -- small, coccobacilli

Question 37

Coxiella burnetti

Answer 37

"Atypical" bacteria -- small, coccobacilli, gram-negative but does not stain well

Question 38

Listeria monocytogenes

Answer 38

Gram-positive bacillus, aerobic, non-sporeforming (NSF)

Question 39

Corynebacterium diphtheriae

Answer 39

Gram-positive bacillus, aerobic, non-sporeforming (NSF), pleomorphic

Question 40

Bacillus cereus

Answer 40

Gram-positive bacillus, spore-forming, aerobic

Question 41

Bacillus anthracis

Answer 41

Gram-positive bacillus, spore-forming, aerobic

Question 42

Clostridium species

Answer 42

Gram-positive bacilli, spore forming; Anaerobe

Question 43

Clostridium difficile

Answer 43

Gram-positive bacilli, spore forming; Anaerobe

Question 44

Clostridium botulinum

Answer 44

Gram-positive bacilli, spore forming; Anaerobe

Question 45

Clostridium tetani

Answer 45

Gram-positive | bacilli, sporeforming, spore causes enlarged end of bacilli, i.e. drumstick shape

Question 46

Bacteroides fragilis

Answer 46

Gram-negative bacilli, often pleomorphic