9. a. Salmonella

Question 1

What are the virulence factors of salmonella?

Answer 1

Peritrichous flagellae

Stay alive within macrophages

Question 2

How is salmonella spread?

Answer 2

Faecal-oral

Contaminated food and water

Question 3

In typhoidal salmonella, what events lead up to the primary bacteraemia?

Answer 3

Bacteria adheres to and penetrates epithelium over Peyer’s patches using fimbriae
Ingested by macrophages and brought to mesenteric lymph nodes
Multiply in lymph nodes
Primary bacteraemia occurs at days 10-14

Question 4

How does typhoidal salmonella cause a secondary bacteraemia?

Answer 4

Invade and multiply in liver, gall bladder, spleen and bone marrow
Secondary bacteraemia occurs during week 3

Question 5

How does typhoid fever progress after the secondary bacteraemia?

Answer 5

From the gallbladder the bacteria reinfects the intestinal tract and causes necrosis of Peyer’s patches

Question 6

What are the clinical features of typhoid fever during the first week?

Answer 6

Slowly rising temperature
Headache
Bradycardia
Constipation or diarrhoea

Question 7

What are the clinical features of typhoid fever during the second week?

Answer 7

High fever
Distended abdomen and splenomegaly
Pea soup diarrhoea
Rose spots

Question 8

What are rose spots?

Answer 8

Bacteria embolise to dermis
Found on flanks, buttocks and costal margin
Resolve within 2-5 days
Salmon coloured blanching maculopapules

Question 9

What are the clinical features of typhoid fever during the third week?

Answer 9

Hepatic, renal and bone marrow dysfunction
Bowel perforation
Osteomyelitis of spine and long bones if sickle cell

Question 10

What are the clinical features of typhoid fever during the fourth week and beyond?

Answer 10

Symptoms improve but bowel may still perforate

Weight loss and debilitating weakness for months

Question 11

What is chronic carriage of typhoidal salmonella defined as?

Answer 11

Positive stool cultures 12 months after overcoming the disease

Question 12

What is the management of a chronic carrier of typhoidal salmonella?

Answer 12

Ciproflaxin for 1 month
Can’t work in the food industry until negative stool
Increased risk of gallbladder cancer

Question 13

What samples can be cultured to diagnose typhoid fever?

Answer 13

Blood in first week
Faeces in second
Urine in third
Bone marrow

Question 14

What is the treatment for typhoid fever?

Answer 14

10-14 days of ceftriaxone

Check susceptibility for ciprofloxacin and azithromycin

Question 15

What vaccines are available for typhoidal salmonella?

Answer 15

Polysaccharide subunit

Live attenuated oral

Question 16

What are the sources of salmonella gastroenteritis?

Answer 16

GIT of animals and reptiles
Foodborne in meat and animal products
Faecal-oral

Question 17

What is the incubation period of salmonella gastroenteritis?

Answer 17

18-72 hours

Question 18

What are the clinical features of salmonella gastroenteritis?

Answer 18

3-7 days of diarrhoea, nausea, headache

Danger of dehydration

Question 19

What is chronic excretion of salmonella gastroenteritis?

Answer 19

Up to 4 weeks after the infection

Question 20

What factors increase the likelihood a patient will chronically excrete salmonella?

Answer 20

Antibiotics
HIV
IBD
Diverticulosis

Question 21

What complications are associated with salmonella gastroenteritis?

Answer 21

BSI
Osteomyelitis
Meningitis
Infect prosthetics, grafts and valves
Reactive arthritis

Question 22

When should antibiotics be given in salmonella gastroenteritis?

Answer 22

younger than 1 or older than 50
Immunocompromised
Risk factors for endocarditis or joint disease

Question 23

What are the lab features of salmonella?

Answer 23

Gram negative bacilli
Non-lactose fermenting
Black colonies on XLD

Question 24

Why does salmonella produce black colonies on XLD?

Answer 24

Hydrogen sulphide production

Question 25

What is used to track salmonella outbreaks?

Answer 25

Whole genome sequencing