Enterobacteriae

Question 1

Enterobacteria general characteristics

Answer 1

• facultative anaerobe
• gram negative
• noncapsulated
• motile
• nitrate reduction
• oxidase negative
• catalase positive
• ferment sugars
• non fastidious
• non spore forming

Question 2

Components of the cell wall of enterobacteria

Answer 2

Somatic O polysaccharide
Core polysaccharide
Lipid A

Question 3

Serologic Ags of Enterobacteriae

Answer 3

Somatic O -> strain specific, cross rx between closely related genera
K Antigens -> in the capsule
H Antigens -> in flagella -> heat labile

Question 4

Motile species of Enterobacteriae are coated with

Answer 4

Peritrichous flagella

Question 5

Common virulence factors associated with enterobacteria

Answer 5

• endotoxin _> depends on Lipid A component of LPS
• capsule
• antigenic phase variation
• type III Secretion System
• sequestration of growth factors -> siderophores
• resistance to serum killing
• antimicrobial resistance

Question 6

Dieseases caused by e. Coli

Answer 6

Gastroenteritis, UTIs (produce Hemolysin A), neonatal Meningitids (K1 capsular Antigen), Sepsis

Question 7

E. Coli gastroenetrotis causing strains

Answer 7

ETEC -> heat stable (ST) and heat labile (LT) enterotoxins
EPEC
EAEC -> shortening of microvilli
STEC -> evolved from EPEC, shiga toxin
EIEC

Question 8

Species of Salmonella

Answer 8

Salmonella enterica -> Salmonella typhi
Salmonella bongori

Question 9

Pathogenesis of Salmonella sp.

Answer 9

• endotoxin
• capsule
• ability to invade cells
• replicate intracellulary
• survival in macrophages & spread
• tolerance to acids
• pathogenicity island I and II
• type III secretion system

Question 10

What is reservoir of salmonella sp.?

Answer 10

Gallbladder

Question 11

Species of shigella

Answer 11

S. Dysenteria (produces Shiga toxin)
S. Flexneri
S. Sonnei
S. Boydii

Question 12

Pathogenesis of Shigella

Answer 12

• invade M cells in colon
• Type III secretion
• replicate in cytoplasm
• actin rearrangement

Question 13

Yersinia species

Answer 13

Y. Pestis _> plague
Y. Enterocolita -> self limiting gastroenteritis
Y. Pseudotuberculosis -> gastroenteritis

Question 14

Klebsiella characteristics

Answer 14

• nonmotile
• polysaccharide capsule
• resistant to most antibiotic classes
• k. Pneumonia, k. Oxytoca

Question 15

Whoch enetrobacteria produces Urease, raises urine pH and renal stones?

Answer 15

Proteus

Question 16

Agar of enterobacter

Answer 16

MacConkey

Question 17

Cell morphology of Enterobacteriacaea?

Answer 17

Gram negative bacillary or cocobacillary cells

Question 18

Colonial morphology of Enetrobacteriacea on
- blood agar
- MacConkey agar
- SS agar

Answer 18

Blood Agar: large, dull, dry or mucoid, swarming phenomenon for proteus

MacConkey Agar: lactose fermenter produce red colonies (E. coli), lactose non fermentors produce colorless or transparent colonies (Salmonella)

SS Agar: Salomonella -> colorless colonies with black centers
Shigella -> colorless colonies with no blackening