Week 4 Microorganisms of GI Tract + Foodborne Infections

Question 1

What does commensal, opportunistic and pathogenic mean when it comes to microorganisms?

Answer 1

Commensal -> live in/on us and don’t cause harm

Pathogenic -> aren’t normally present and cause disease/ harm when they are present

Opportunistic -> normally in us but can become pathogenic when conditions are right e.g. immunosurpressed, antibiotics, antacids etc.

Question 2

What is an obligate pathogen

Answer 2

One that must cause disease to spread and survive

Question 3

What is Gastro-enteritis

Answer 3

Gastro-enteritis
= inflammation of the digestive tract,
causing nausea, vomiting, abdominal pain, diarrhea, potentially fever.

Question 4

FIll in these viral and parasitic causes of GE

Answer 4

Question 5

Fill out these bacterial cause of gastroenteritis?

Answer 5

Question 6

What’s the difference between bacterial infection and intoxication as causes of gastroenteritis (GE)?

Answer 6

Infection means the harm is caused directly by the bacteria multiplying and colinising the GI tract, damaging tissues, causing inflammation and disrupting digestion.

Intoxication means that harm is caused by a toxin produced by the bacteria, the toxin can be produced either before or after the bacteria has been ingested

Question 7

What does secretory mean as a feature of diarrhea?

Give some examples of bacteria that cause secretory diarrhea

Answer 7

Question 8

What does inflammatory mean as a feature of diarrhea?

Give some examples of bacteria that cause inflammatory diarrhea

Answer 8

Question 9

What type of bacteria has faster onset of GE symptoms, infection or toxic?

Answer 9

Toxic has faster onset of symptoms as it can take a several hours/days for infective bacteria ot multiply enough to cause symptoms

Question 10

What are the criteria for mild, moderate and serious diarrhea?

Answer 10

Question 11

Differences in character of diarrhea whether it is the small bowel or large bowel affected?

Answer 11

Question 12

Fill in these bacterial causes

Answer 12

Question 13

Where is the GI tract do the following pathogens inhabit?

1. Vibrio cholerae
2. Shigella spp
3. Clostridioides difficile
4. Helicobacter Pylori

Answer 13

Question 14

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Question 15

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Question 16

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Question 17

Answer 17

Question 18

Answer 18

Question 19

Answer 19

Question 20

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Question 21

Answer 21

Question 22

• Jeremy, 22yo Student No medical history
• Epigastric pain, waxing and waning for a « few months »
• Better just after eating, but then worse 2-3 hours after
• Worse when leans forward, better when sat up
• Bought some GavisconⓇ in the pharmacy - symptoms resolved for a while
• Has taken his grandma’s Omeprazole for few days - cessation of symptoms but relapse after 2 weeks

He goes to his GP, what would a stool test reveal?

Answer 22

Helicobacter Pylori antigens

Question 23

What is the appearence of helicobacter pylori?

Answer 23

Curved/spiral-shaped

Question 24

Is helicobacter pylori gram-negative or gram-positive

Answer 24

Gram negative

Question 25

How does H. pylori survive in the sotmach?

Answer 25

It produces urease which can break down urea in the stomach. Urea os broken down in to ammonia and co2. The ammonia then buffers pH causing a neutral micro-environment

Question 26

What are the pathogenesis of H. pylori symptoms?

Answer 26

Gastric and duodenal ulcers leads to gastritis and gastric cancer

Question 27

How is H. pylori diagnosed?

Answer 27

Biopsy and histology/culture and/or Urea breath test and/or Antigen in stools

Question 28

How common is h. pylori?

Answer 28

Very common Present in up to 50% of western adults and 100% in developing world Mostly asymptomatic. Only treated when symptoms present.

Question 29

Is Campylobacter jejuni gram -ve or gram +ve?

Answer 29

gram negative

Question 30

Campylobacter jejuni common cause?

Answer 30

Undercooked poultry

Question 31

Campylobacter jejuni incubation period?

Answer 31

1-3 days

Question 32

Campylobacter jejuni symptoms

Answer 32

Bloody stool / abdominal cramps / fever

Question 33

Campylobacter jejuni long term complications?

Answer 33

Bacteraemia Guillain- barre syndrome

Question 34

Is Non typhoidal Salmonella gram -ve or gram +ve

Answer 34

gram -ve

Question 35

What is the rule of thumb for gram +ve/ gram -ve things?

Answer 35

If it lives in a wet environment it's gram nagative Hint - rain is never fun

Question 36

Non typhoidal Salmonella causes

Answer 36

Eggs (imported) / poultry/ meats/ pets

Question 37

Non typhoidal Salmonella Incubation period?

Answer 37

Incubation period : 6- 72 hours

Question 38

Non typhoidal Salmonella syptoms?

Answer 38

D & V / high fever (no blood)

Question 39

Non typhoidal Salmonella long term complications?

Answer 39

bacteraemia aortitis osteomyelitis meningitis splenic cyst

Question 40

If salmonella is typhoidal how does it present?

Answer 40

Fever and constipation

Question 41

Common cause of viral diarrhoea in immuno-competent children

Answer 41

Rotavirus

Question 42

Common cause of viral diarrhoea in immuno-competent adults

Answer 42

Norovirus

Question 43

* You work for MSF in DRCongo, in a refugee camp in North- Kivu * The nurse comes to you: in the last 2 days, 17 residents have presented with acute « gastroenteritis » * Nausea - Vomiting – water diarrhea +++ Vast majority has no pain, no fever What is this?

Answer 43

Vibrio cholerae aka cholera ou know this because diarrhea with no pain or fever

Question 44

How is vibrio cholerae spread?

Answer 44

contaminated water or food (seafood!)

Question 45

Is vibrio cholerae gram +ve or gram -ve?

Answer 45

Gram -ve

Question 46

What is the shape of vibrio cholerae?

Answer 46

comma-shaped bacterium – motile with polar flagellum

Question 47

How does vibrio cholerae cause its problems?

Answer 47

Produces a toxin which prevent sodium absorbtiona nd encourages water secretion

Question 48

How do you test for cholera?

Answer 48

Stool Culture

Question 49

What is the cause of death of cholera?

Answer 49

Dehydration

Question 50

How are cholera stools often described?

Answer 50

Rice-water stools

Question 51

How do you treat cholera?

Answer 51

Rehydrate with water + sodium either orally or IV Antibiotics

Question 52

* You work in the A&E at the RIE * Michelle, 62yo, back from Tanzania 2 days ago * MH: Thyroxine for hypothyroidism > 30 years * The last day of the trip, eats a street food « local speciality » Abdominal cramps started the day before admission * Brought by her husband because of high fever (39.5°c), chills, diffuse abdominal pain (cramping), diarrhea first watery but then with fresh blood —> Panicked * Physical examination: Sweating, pale, in pain, Abdomen soft but diffuse pain * Bloods: High inflammatory markers, Nothing else remarkable What do you think? What do you do?

Answer 52

Shigella Supportive + Antibiotics

Question 53

Shingella gram staining?

Answer 53

Gram -ve

Question 54

Shingella microscopic character

Answer 54

Nonmotile, facultatively anaerobic, rods

Question 55

Shingella transmission

Answer 55

contaminated water or food, very low infectious load

Question 56

Shingella family?

Answer 56

Enterobacteriaceae

Question 57

Which if these four species of shingella are important for diarrhea? S. dysenteriae S. flexneri S. boydii S. sonnei

Answer 57

S. dysenteriae

Question 58

Is shingella an invasive or toxic pathogen?

Answer 58

Primarily Invasive (hence invasive in previous ven-diagram) However S. dysenteriae does produce shiga-toxin

Question 59

Shingella symptoms

Answer 59

Bacterial dysentery = Bloody diarrhea (+pus/mucus) + Abdominal cramps + Fever

Question 60

Shingella long term complications

Answer 60

Local: toxic megacolon Systemic: hemolytic uremic syndrome (HUS) (breakdown of red blood cells, low platelet count, and acute kidney injury) cause by shiga-toxin

Question 61

Shingella diagnosis?

Answer 61

Stool culture +- (PCR)

Question 62

* You’re an SHO on the geriatrics ward * Pablo, 82yo, admitted for productive cough, fever, dyspnea and chest pain * Right inferior lobe pneumonia —> Start on Amoxicillin-Clavulanic Acid (Co-Amoxiclav) * Day 7 of admission: better, smiling, no need for oxygen anymore, cough and fever resolved —> Stop antibiotics * Day 9: sudden onset of severe diarrhea, and relapse of fever Stools: Greenish, liquid, smelly++ WHat do you do? What do you find out?

Answer 62

* Stool analysis * +ve for C. Difficile toxin

Question 63

What does c. diff. look like?

Answer 63

Anaerobic Motile, spore former

Question 64

Is c. diff. gram +ve or gram -ve?

Answer 64

Gram-positive

Question 65

Out of the four big bacterial GI infections we will most likely get asked about which are gram -ve and which are gram +ve?

Answer 65

* Clostridioides difficile: +ve * Shigella: -ve * Vibrio cholerae: -ve * Campylobacter jejuni: -ve

Question 66

When are you more vunerable to c. diff.?

Answer 66

C. diff. is antibiotic resistant so you are vunerable after antibiotic use. Particularly potent in hospitals

Question 67

What happens to c. diff. in the stomach?

Answer 67

C. diff. itself is destroyed by acid in the stomach. However the spores are highly durable and are acid resistant. It is the injestion of spores that leads to an infection

Question 68

What is the timeline of c. diff. from susceptibility to symptoms

Answer 68

Question 69

Is c. diff. infective or toxic?

Answer 69

Toxic

Question 70

What are the two c. diff. toxins?

Answer 70

* Toxin A (TcdA) – enterotoxin * Toxin B (TcdB) – cytotoxin

Question 71

From mild to severe what is the range of c. diff. symptoms?

Answer 71

* Asymptomatic carriage * Diarrhoea / simple colitis * Pseudomembranous colitis * Fulminant (sudden and intense onset) colitis

Question 72

What is pseudomembranous colitis?

Answer 72

Pseudomembranous colitis is a severe inflammation of the colon characterized by the presence of yellow-white plaques (called pseudomembranes) on the colonic mucosa. These pseudomembranes are made of: * Dead epithelial cells * Fibrin * Mucus * Inflammatory cells (neutrophils) They sit on top of damaged mucosa — hence the name "pseudo" membrane (not a real epithelial membrane).

Question 73

Which antibiotics should you be careful with with regards to c. diff.?

Answer 73