Salmonella

Question 1

General characteristics of salmonella

Answer 1

Gram (-) rods

Catalase (+)

Oxidase (-)

Facultative anaerobes

Grows yellow on macconkey agar

Ferments glucose but NOT lactose

Motile

Question 2

What are the most common causes of getting salmonella?

Answer 2

Animals:

• poultry
• turtles
• dogs/cats
• hedgehogs
• pigs and cattle

Vegetables and leafy greens

Question 3

What are the 4 main types of salmonella infections

Answer 3

1) gastroenteritis
2) bacteremia/septicemia (w/out GI symptoms)
3) enteric fever
4) carrier (asymptomatic) state

Question 4

Gastroenteritis salmonella symptoms

Answer 4

most common form of infection

Incubates for 12-48 hrs

Sudden onset once it is active and presents with:

• fever, chills, cramps, profuse diarrhea, vomiting
• few leukocytes in stool

Lasts 2-3 days in health hosts and is self-limiting

• can remain in stool for weeks thou
• much more dangerous in immunocompromised and infants

Question 5

What are the most common genus and serotypes of salmonella

Answer 5

S. Enterica = most common genus

Both below are most common serotypes:

• Enterica typhimurium
• Enterica entertitids

Question 6

Enteric fever salmonella

Answer 6

Incubation is 7-20 days

Has an insidious onset that lasts for several weeks:

• gradual increasing fever that plateaus into a “ typhoidal” state
• constipation and bloody diarrhea

Is more dangerous than gastroenteritis form

Question 7

Salmonella pathogensis

Answer 7

Invades epithelium and induces inflammation and neutrophil extravasion
- causes edema

Edema causes inflammatory damages and effusion of neutrophils causing neutrophil damage secondarily as neutrophils try to kill pathogens

Virulence factors:

• fimbrial attachment
• induce cellular “ruffling” (forces host cell to engulf bacterium)
• survive in own vacuoles inside cells and prevents phagolysosome fusion
• resistance to acid and serum killing (acutely, chronically will die)

Question 8

How to diagnose salmonella diagnosis

Answer 8

Get sample from food/water/stool
- blood also if fever is present

grow on SS agar

• pink = e. Coli
• black = salmonella

Question 9

What ages are the highest incidence in infants?

Answer 9

6 months - 5 years

- more common in summer vs winter seasons

Question 10

Why is salmonella infections increasing?

Answer 10

Food processing is changing

Consumer preferences are changing

Poor sanitation/contamination are more likely

fresh fruits/vegetables = increased risk of salmonella

Question 11

Typhoid fever presentation and pathogenesis

Answer 11

caused by salmonella enterica typhi

Possess Vi capsule*
- resists all complement activity of host

Presentation

• growing constant fever
• diffuse rose spots on abdomen
• GI distress with potential hemorrhage