Enterobacteriaceae

Question 1

Primary intestinal pathogens (4)

Answer 1

Salmonella
Shigella
Yersinia enterocolitica
E. coli 0157:H7

Question 2

Gram stain

Answer 2

g- b

Gram neg facultative rods

Question 3

Motility

Answer 3

Peritrichous flagella OR non-motile

Question 4

Lactose Fermentors on MAC

Answer 4

Pink (pk)
Mucous (pk muc) - Klebsiella pneumoniae
Dry (dry pk) - Escherichia coli

Question 5

Oxidase rxn

Answer 5

NEG - colourless tetramethyl-p-phenylene diamine (TMPD)

pos - purple indophenol

Question 6

Oxidase Theory

Answer 6

Cytochromes - electron transport chain

Question 7

Triple Sugar Iron (TSI) Theory

Answer 7

Differential medium - CHO fermentation, H2S and gas production
Slant - aerobic
Butt - anaerobic
Indicator - phenol red (below pH 6.8)
Stab, streak, incubate 18-24 h, 35°C

Question 8

TSI Results

Answer 8

Nonfermenters (K/K) = Alk slant/Alk butt, no change
Non-Lactose fermenter (K/A) = Alk slant/Acid butt, glucose fermented
Lactose/Sucrose Fermenter (A/A) = Acid slant/Acid Butt
H2S -

Question 9

Citrate

Answer 9

Organism used citrate as a carbon source.
Brothymol blue indicator (alk end product)
POS - blue
NEG - green

Question 10

Serologic groups

Answer 10

O (somatic) Ag
H (flagellar) Ag
K (capsular) Ag

Question 11

O Ag

Answer 11

Somatic
Heat-stable
Located in cell wall
Resists alcohol

Question 12

H Ag

Answer 12

Flagellar
Heat-labile
Found in flagellum
Resists formalin

Question 13

K Ag

Answer 13

Capsular
Heat-labile polysaccharide
K1 Ag (E. coli) 
Vi Ag (Salmonella typhi)
May mask O Ag

Question 14

Biochemical Test Sequence for LF

Answer 14

MAC - pk
BAP - Lg gy
Gram stain, TSI, MCIOM (lysine)
(malonate, citrate, indole, ornithine, motility)

Question 15

Biochemical Test Sequence for NLF, LLF

Answer 15

MAC - wt
BAP - Lg gy
Oxidase, TSI, UPOIM
(Urea, Phenylalanine, Ornithine, Indole, Motility)