MI: GI infections Pt.3

Question 1

What are the main microbiological features of Campylobacter?

Answer 1

• Gram negative
• Comma-shaped
• Microaerobphilic
• Oxidase-positive
• Motile

Question 2

How is Campylobacter transmitted?

Answer 2

Transmitted via ingestion of food and water contaminated with animal faeces

Question 3

Describe the presentation of Campylobacter jejuni infection.

Answer 3

• Watery, foul-smelling diarrhoea, bloody stools, fever and severe abdominal pain

Question 4

How is Campylobacter infection treated?

Answer 4

Only treated if immunocompromised

• Erythromycin or ciprofloxacin if presenting within first 4-5 days

Question 5

What are some complications of Campylobacter infection?

Answer 5

Guillian-Barre syndrome

Reactive arthritis

Question 6

Which other bacterial organisms can cause GI disease?

Answer 6

Yersinia enterocolitica

• Non-lactose fermenting
• Transmitted via food contaminated with faeces of domestic animals
• Causes enterocolitis and mesenteric adenitis
• Also associated with reactive arthritis

Mycobacteria (M. Tuberulosis, Avium, Intracellulare)

Question 7

What are the key characteristics of Entamoeba histolytica?

Answer 7

• Motile trophozoite in diarrhoeal illness
• Non-motile cyst in non-diarrhoeal illness
• Killed by boiling, removed via water filters
• Contains four nuclei
• No animal reservoir

Question 8

Describe the pathophysiology of diarrhoeal illness caused by Entamoeba histolytica.

Answer 8

Ingestion of cysts → trophozoites move into the ileum → colonise the colon → causes flask-shaped ulcers

Question 9

Describe the presentation of GI infection by Entamoeba histolytica.

Answer 9

• Dysentry
• Flatulence
• Tenesmus
• Liver abscess

Chronic infection can cause weightloss +/- diarrhoea

Question 10

How is Entamoeba histolytica infection diagnosed and treated?

Answer 10

• Diagnosis: stool microscopy (wet-mount, iodine and trichrome), serology of invasive disease
• Treatment: metronidazole + paromomycin

Question 11

What are the key microbiological features of Giardia lamblia?

Answer 11

• Pear-shaped trophozoites
• Two nuclei
• Four flagellae and a suction disc

Question 12

Outline the pathophysiology of GI disease caused by Giardia.

Answer 12

• Transmitted by ingestion of cyst from faecally contaminated water
• Excystation in the duodenum leads to trophozoite attachment
• Results in malabsorption of protein and fat

Question 13

How does Giarda infection present?

Answer 13

• Foul-smelling non-bloody diarrhoea,
• Cramps, flatulence,
• NO fever

Question 14

How is Giardia infection diagnosed and treated?

Answer 14

• Stool microscopy
• ELISA
• String test
• Treatment: metronidazole

Question 15

What are the main features of Cryptosporidium parvum?
What stain is used?

Answer 15

• Protozoa that causes severe diarrhoea in the immunocompromised
• Oocysts can be seen in the stool using modified Kinyoung acid fast stain
• Treated by boosting the immune system

Question 16

What is the predominant strain of norovirus?

Answer 16

GII4

Question 17

What is rotavirus and what does it cause?

Answer 17

• dsDNA virus
• Replicates in the mucosa of the small intestine
• Causes secretory diarrhoea with no inflammation

NOTE: exposure to natural infection twice will confer lifelong immunity

Question 18

List some other viruses that can cause diarrhoeal illnesses.

Answer 18

• Adenovirus (types 40 and 41 can cause non-bloody diarrhoea in <2 year olds) - diagnosed via PCR or stool antigen detection
• Poliovirus
• Enterovirus (e.g. coxaskie, echovirus)
• Hepatitis A

Transmitted via faeco-oral route

Question 19

Which causes of diarrhoeal illness have available vaccines?

Answer 19

• Cholera (serogroup O1)
• Campylobacter
• ETEC
• Salmonella typhi
• Rotavirus - rotarix (live, monovalent), rotateq (pentavalent), rotashield (used if risk of intussusception)

Question 20

Who is responsible for collecting reports of diarrhoeal illness and identifying outbreaks?

Answer 20

Health Protection Unit (HPU)