Week 10

Question 1

Identify key microbial classes involved in causing GIT infections

Answer 1

Bacteria: Salmonella spp.
Viruses: Rotavirus, Norovirus
Protozoa: Giardia, Cryptosporidium spp.
Helminths: Strongyloides

Question 2

Provide examples for the ‘contact’ mode of transmission and associated infectious agents

Answer 2

1. Fingers - direct contact (c.difficle)
2. Fomites - indirect contact (c.difficle)
3. Faeces - indirect contact (shigella spp.)

Question 3

Provide examples for the ‘common vehicle’ mode of transmission and associated infectious agents

Answer 3

1. Contaminated water - stagnant water, high concentration organic material (Giardia)
2. Food poisoning - poor storage (staphylococcus aureus exotoxin)

Question 4

Label key features anatomically

Answer 4

google picture

Question 5

what are some susceptible hosts and give reasons for why they are susceptible

Answer 5

Extremes of age
- immune response
- hygiene practices

Malnutrition/Poor Immune response
- medication
- treatment
- co-morbid diseases

Travelers
- Immunologically naive to endemic infections in travel zones

Question 6

Provide a detailed example for endogenous reservoirs for GIT infections

Answer 6

• imbalance in the gut of the infected individual allowing opportunistic overgrowth of usually low abundance microbes
• for example Clostridioides difficile, may be caused by antimicrobial treatment

Question 7

Provide a detailed example for exogenous reservoirs for GIT infections

Answer 7

• externally originating infectious agents
• for example, Vibrio cholerae from the environment, via drinking water contaminated with faecal material

Question 8

Compare and contrast inflammatory and non inflammatory diarrhoea using stool features, site of infection, and common causes

Answer 8

Inflammatory
Stool
- blood/pus/mucus
- small volume

Site of infection
- Colon (large intestine)

Common Causes
- campylobacter
- salmonella
- c.difficle

Non-inflammatory
Stool
- no leukocytes
- rarely blood/mucus
- large volume

Site of infection
- small intestine (reason there is a large volume - less time for water reabsorbed)

Common causes
- viruses
- staphylococcus aureus

Question 9

Provide 3 examples of when antimicrobial therapy would be appropriate and indicated in addition to symptomatic management for GIT infection

Answer 9

All infected individuals with Shigella spp. due to low infectious dose

Clostridioides difficile patients with recent antimicrobial therapy due to refractory disease

Candida spp. and immunocompromised (HIV, solid organ transplant) due to immune impairment, risk of secondary systemic infection

Question 10

Using the example of a norovirus outbreak on a cruise ship, describe the preventative measures and control strategies that could be used to protect against transmission through vomit and fecal material.

Answer 10

Vomit
- preventative measures include hand hygiene, and a surgical mask
- control strategies include isolation/quarantine and emesis bags

Fecal material
- preventative measures include hand hygiene, splash screens for food buffets, serving implements restricted to specific foods
- control strategies include isolation/quarantine and sewerage treatment

Question 11

Using the example of a Clostridioides difficile infection in a care-facility resident, describe the preventative measures and control strategies that could be used to protect against transmission through fecal material.

Answer 11

Preventative measures
- antimicrobial stewardship (narrow spectrum, minimum duration)
- hand hygiene (not ABHR as not sporicidal)
- surface disinfection (sporicidal)
- “one bum one seat”

Control strategies
- isolation/quarantine
- standard and contact precautions (environmental cleaning and linen, waste management, safe sharps use and disposal, aseptic technique, equipment reprocessing, PPE-aprons and gloves)