Quiz 2

Question 1

What are 3 clinically significant enterobacteria that are not part of normal flora?

Answer 1

Salmonella spp
Shigella spp
Yersinia spp

Question 2

What are phenotypic features of enterobacteria

Answer 2

• GNR or coccobacilli
• facultative anaerobes
• non-spore formers
• glucose fermenter - sugar
  fermenters
• catalase + (except Shigella dysenteriae)
  Oxidase - (except Plesiomonas shigelloides)
• capable of reducing nitrates to nitrite
• capable of growing on MAC

Question 3

Why do we do stool cultures?

Answer 3

R/O enteric pathogens: Salmonella, Shigella, Campylobacter, E. coli O157:H7, Yersinia, Aeromonas and Vibrio

All fecal samples are routinely screened for Salmonella, Shigella and Camplyobacter
- some labs screen for E. coli O157:H7

Question 4

Collection and transport of stool cultures

Answer 4

fresh stool plated immediately, held on ice for 2 hrs (needs preservatives)
- kept in transport medium (cary-blair, Amies, Stuart) 4 days

Question 5

What media do you use if you suspect Shigella?

Answer 5

blood agar, MAC, HE, XLD

Question 6

E. coli

Answer 6

• motile
• GNR
• lactose-fermenter
• Most common cause of UTI, septicemia, nosocomial infections
• AA on TSI
• nitrate +, MUG +

++–

Question 7

Enterohemorrhagic E. coli (EHEC)

Answer 7

shiga-toxin producing E. coli

causes hemorrhagic colitis/hemolytic-uremic syndrome (HUS) - O157:H7

Question 8

E. coli O157:H7

Answer 8

VF - cytotoxin (shiga-toxin) or verotoxin
SMAC

O - somatic/cell wall Ag
H - flagella Ag

Question 9

Klebsiella

Answer 9

• non-motile GNR
• opportunistic (lives in GIT)
• pneumonia, septicemia, UTI, ENT
• lactose-fermenter
• encapsulated (mucoid colonies)
• A/A
  –++
  oxidase -, nitrate +

Question 10

Serratia

Answer 10

• motile GNR
• red pigment on MAC (prodigiosin)
• UTI, endocarditis, otitis externa, septicemia, wound infections, arthritis
• lactose fermenter
  A/A
  oxidase -, nitrate +

Question 11

Proteus

Answer 11

• motile, GNR
• Swarmers
• non-lactose fermenter
• opportunistic pathogen
• UTI, septicemia, pneumonia, wound infection
  K/A
  P. vulgaris Indole +
  P. mirabilis Indole -
• oxidase -, nitrate +
• phenylalanine deaminase (PAD) +
  More common than serratia

Question 12

Morganella morganii

Answer 12

• motile, GNR
• related to Proteus
• non-lactose fermenter
• no swarming on blood agar
• opportunistic
• UTI, septicemia, pneumonia, meningitis, wound infections
  K/A w/gas
  ++–
• oxidase -, nitrate +
  PAD +

Question 13

Providencia

Answer 13

• motile, GNR
• non-lactose fermenter
• no swarming
• UTI, septicemia, pneumonia, meningitis, burn wound infections
• K/A w/wout H2S
  ++-+
  oxidase -, nitrate +
  PAD +

Question 14

Salmonella

Answer 14

S. enterica (typhi) & S. bongori

- eggs, poultry, unpasteurized dairy