IIA. Systemic Bacteriology | 9. Salmonella and Shigella

Question 1

I. Salmonella
1. What are the features of salmonella?

Answer 1

• Gram-negative
• motile rods, peritrich flagella
• Non-spore forming
• Facultative anaerobic

Question 2

I. Salmonella
2. What are the optimal environment for Salmonella?

Answer 2

• Salmonella grow at an optimum of 37oC
• Optimum pH for growth of Salmonella is 6.5-7.5; may grow at a pH range of 4.5-9.0

Question 3

I. Salmonella
3. what are the biochemical properties of salmonella?

Answer 3

• H2S production
• Lactose negative, Urease negative, Indol negative

Question 4

I. Salmonella - Salmonella serology
4A. What is Salmonella serology based on?

Answer 4

Serogroups or serotypes based on O and H (flagella) antigens.

Question 5

I. Salmonella - Salmonella serology
4B. What are the features of O antigens

Answer 5

O antigens are vary variable

Question 6

I. Salmonella - Salmonella serology
4C. What are the features of H antigens

Answer 6

The H (flagella) antigens
* occur in two phases;
1 and 2 and only one phase is expressed at a given time

Question 7

I. Salmonella
5. What are the salmonella virulence factors?

Answer 7

• Endotoxin – may play a role in intracellular survival
• Capsule (for S. typhi and some strains of S. paratyphi)
• Adhesions – both fimbrial and non-fimbrial
• Flagella – help bacteria to move through intestinal mucous

Question 8

I. Salmonella
6. Which species of Salmonella have capsule as a virulence factor?

Answer 8

Capsule (for S. typhi and some strains of S. paratyphi)

Question 9

I. Salmonella
7A. What is clinical significance of salmonella?

Answer 9

Question 10

I. Salmonella
7B. What are the features of salmonellosis?

Answer 10

• Salmonella multiply in the GI tract inducing a strong inflammatory response
• > The inflammatory response prevents the spread beyond the GI tract and eventually kills the bacteria.

Question 11

I. Salmonella
7C. What are the features of enteric fever?

Answer 11

Salmonella disseminate before they multiply to high enough levels to stimulate a strong inflammatory response.

Question 12

I. Salmonella
8. What are important serotypes of salmonella?

Answer 12

S. Typhi and Paratyphi A, B, C

Question 13

I. Salmonella
9. What are the features of zoonotic infections?

Answer 13

Question 14

I. Salmonella
10. What are the serotypes responsible for salmonellosis?

Answer 14

caused by for e.g. S. Enteritidis, S. Typhimurium, S. Choleraesuis

Question 15

I. Salmonella - serotypes responsible for salmonellosis
11. What is the source of infection of serotypes responsible for salmonellosis?

Answer 15

animal feces

Question 16

I. Salmonella - serotypes responsible for salmonellosis
12. What is the transmission route of infection of serotypes responsible for salmonellosis?

Answer 16

route of transmission: consumption of food contaminated with human feces
* especially improperly cooked poultry, eggs
* symptoms usually start 18-24 hours after ingestion

Question 17

I. Salmonella - serotypes responsible for salmonellosis
13. What is the disease caused by serotypes responsible for salmonellosis?

Answer 17

Question 18

I. Salmonella - serotypes responsible for salmonellosis
14. How do we diagnose serotypes responsible for salmonellosis?

Answer 18

Question 19

I. Salmonella - serotypes responsible for salmonellosis
15. What is the treatment for salmonellosis?

Answer 19

• AB treatment is not needed
• supportive treatment (rehydration mainly)
• in invasive / systemic cases might consider ampcillin, fluoroquinolons, ceftriaxon

Question 21

I. Salmonella - enteric fever
16. What are serotypes responsible for enteric fever?

Answer 21

Caused by S. Typhi, S. Paratyphi A, B, C

Question 21

I. Salmonella - enteric fever (S. Typhi, S. Paratyphi A, B, C)
17. What is the source of infection of enteric fever?

Answer 21

infected human feces

Question 22

I. Salmonella - enteric fever (S. Typhi, S. Paratyphi A, B, C)
18. What is the transmission route of infection of enteric fever?

Answer 22

consumption of food contaminated with infected human feces

Question 23

I. Salmonella - enteric fever (S. Typhi, S. Paratyphi A, B, C)
18. How does enteric fever infect?

Answer 23

enteric fever (invasive infection!)
- small intestine invasion
→ macrophages (Peyer-patches)
→ mesenteric lymphnodes
→ primary bacteriaemia (blood stream)
→ hepatic Kupffer cells
→ secondary bacteriaemia

Question 24

I. Salmonella - enteric fever (S. Typhi, S. Paratyphi A, B, C)
19. What are the symptoms of enteric fever?

Answer 24

• high fever
• bradycardia, rash
• “brain fog” (confusion)
• hepatosplenomegaly
• Peyer-patch perforation (blood might appear in stool)

Question 25

I. Salmonella - enteric fever (S. Typhi, S. Paratyphi A, B, C) 20A. How do we diagnose enteric fever?

Answer 25

- diagnosis: based on clinical signs and symptoms 1. Sampling 2. Laboratory

Question 26

I. Salmonella - enteric fever (S. Typhi, S. Paratyphi A, B, C) 20B. How do we diagnose enteric fever based on sampling?

Answer 26

stool, bile, blood culture, blood (for serology)

Question 27

I. Salmonella - enteric fever (S. Typhi, S. Paratyphi A, B, C) 20C1. How do we diagnose enteric fever based on laboratory?

Answer 27

Cultivation, but it is not enough (all are S. enterica, but the serotype does matter!) - serotyping→ agglutination - indirect confirmation: mixing patient’s serum with known Salmonella Typhi bacteria in a test tube → agglutination = confirms that the patient has antibodies against S. Typhi (Gruber-Widal tube agglutination)

Question 28

I. Salmonella - enteric fever (S. Typhi, S. Paratyphi A, B, C) 20C2. How do we perform indirect confirmation of enteric fever based on laboratory diagnose?

Answer 28

consumption of food contaminated with infected human feces

Question 29

I. Salmonella - enteric fever (S. Typhi, S. Paratyphi A, B, C) 21. What is the empirical treatment for enteric fever?

Answer 29

* beta-lactams (aminopenicillins, cephalosporins) * fluoroquinolons * trimetophrim-sulfamethoxazol

Question 30

I. Salmonella - enteric fever (S. Typhi, S. Paratyphi A, B, C) 22. How do we prevent enteric fever?

Answer 30

Vaccination (pl. Typhim Vi: capsular vaccine) - recommended before travelling to certain destinations - mandatory in certain professions ( laboratory workers, wastewater technicians)

Question 31

I. Salmonella 23A. What are the agar plates suitable for Salmonella culturing?

Answer 31

1. Bismuth-sulphite agar: H2S-production → black colonies 2. brillantgreen ager 3. deoxycholate-citrate agar (DC) 4. Xylose-lysine deoxycholate agar (XLD): H2S-production → black colonies 5. Hektoen-agar

Question 32

I. Salmonella 23B. What are the features of Brillant-green culture media?

Answer 32

- Brillant green – for selection lactose, dextrose, saccharose Andrade indicator (acidic pH -> - Salmonella lactose neg.– no colour - E. coli lactose+ - red)

Question 33

I. Salmonella 23C. What are the features of Bismuth-sulphite media?

Answer 33

brillant green – for selection bismuth salt + sodium sulphite -> Salmonella H2S production => Bismuth sulphide (black)

Question 34

I. Salmonella 24. What are the bacteria that cause typhoid and parathyoid fever?

Answer 34

Question 35

II. Shigella 1. What are the features of Shigella?

Answer 35

- Gram Negative (-) rod, enterobacteriaceae, non-lactose fermenter - Facultative anaerobic - Non-motile - Grows green colonies on hektoin agar - Acid resistant (only a few organisms required to start an infection

Question 36

II. Shigella 2. What is the optimal environment for Shigella?

Answer 36

* pH 6.4 to 7.8 * Temperature 10-40 (optimal temperature 37oC)

Question 37

II. Shigella 3. List the pieces of Shigella genus

Answer 37

Question 38

II. Shigella 4. What is the source of infection of shigella?

Answer 38

: human feces (feco-oral transmission)

Question 39

II. Shigella 5A. What is the disease caused by shigella?

Answer 39

dysentery

Question 40

II. Shigella 5B. What is the pathomechanism of Shigella?

Answer 40

* bacterium infects the intestinal epithelial cells through M-cells * leads to inflammation and ulceration in the bowels (* might heal spontaneously)

Question 40

II. Shigella 5C. What is the diagnosis of Shigella?

Answer 40

dysentery

Question 41

II. Shigella 5D. What is the empirical therapy of Shigella?

Answer 41

- rehydration - Antibiotics: beta-lactams (penicillins, cephalosporins); luoroquinolons; trimetophrim-sulfamethoxazol

Question 42

II. Shigella 6. What do S. dysenteriae do?

Answer 42

Dysenteriae produces Shiga-toxin - capillary entdothelium damage → blood clot formation → RBC damage → haemolysis (haemolytic uraemic syndrome - HUS)

Question 43

II. Shigella 7A. What are the agar plates can we use for growing shigella?

Answer 43

1. Desoxycholate-citrate agar 2. Eosine-methylenblue ag

Question 44

II. Shigella 7B. What are the features of Desoxycholate-citrate agar?

Answer 44

It containing desoxycholic acid, sodium citrate, lead acetate, ferrous ammonium sulfate, lactose, and neutral red indicator => Shigellae: small, round-shaped, colourless colonies (lactose -, H2S-).

Question 45

II. Shigella 7C. What are the features of Eosine-methylenblue ag ar?

Answer 45

small, round-shaped, colourless colonies (lactose -)

Question 46

II. Shigella 8. How can we prevent shigella?

Answer 46

personal and food hygiene