Gut pathogens

Question 1

Candida

Answer 1

• Intestinal yeast
• C. albicans is the most recognised in humans pathogens
• Linked to IBS, fatigue, + itchy skin, recurrent thrush
• Can be managed by nystatin, but not commonly used due to side-effects

Question 2

Types of Bacterial pathogens

Answer 2

• Invasive ie EPEC, Shigella, Campylobacter, Salmonellae
• Cytotoxic ie EPEC, EHEC, some Shigella
• Toxigenic ie V. Cholerae, ETEC, some Shigella
• Adhesive ie EAEC

Question 3

Helicobacter pylori

Answer 3

• Common gastric pathogen
• 6-8 Polar flagellas
• Invades mucosal layer
• Associated with Type B gastritis, peptic ulcer, gastric carcinoma
• Possible faecal oral spread, but still not fully confirmed
• Antimicrobials used to treat it

Question 4

Bacteroides

Answer 4

• Gram -ve rods
• The dominant genus in the colon
• New research shows that there is association with obesity
• Proteolytic + sacchorolytic
• One type is known to be involved in cross-talk, communicating to human cells to influence diet + nutrient intake

Question 5

Clostridia

Answer 5

• Gram +ve spore formers
• Anaerobic
• Some produce toxins
• Proteolytic
• Normal resident of human flora
• Overgrowth can be problematic
• c. difficile
  + Occurs in association with antibiotic exposure
  + PMC
  + Formas plaques composed of mucin, fibrin, + gut cells
  + Most frequently implicated antibiotics: Ampicillin, clindamycin, cephalsporins
  + 2 types of toxins are produces
  + Vancomycin + anion resins used as treatment

Question 6

Fusobacteria

Answer 6

• Filamentous
• Anaerobic
• Gram +ve
• Its role in the gut is unclear, but contributes to several diseases, including periodontal (gum) problems + tropical skin ulcers

Question 7

Staphylococci

Answer 7

• Gram +ve
• Most are completely harmless, but can cause diseases in some
• Contains MRSA variant

Question 8

Streptococci

Answer 8

• Gram +ve coci
• Some used as probiotics
• Certain species are haemolytic
• Grows in chains or pairs
• Found in mouth, skin, intestine + URT of humans

Question 9

Enterococci

Answer 9

• Gram +ve, often occur in pairs
• High level of endemic antibiotic resistance
• Previously used as probiotics
• Facultatively anaerobic

Question 10

Vellonella

Answer 10

• Gram -ve cocci
• Non-motile diplococci
• Occurs in mouth + gut
• Parasitic in nature

Question 11

E. coli

Answer 11

• Gram -ve rods
• Some are pathogenic + cause severe gastroenteritis
• Probiotic variants exist
• Used as indicators in poo

Question 12

Mycobacterium

Answer 12

• Implicated in Crohn’s disease
• Peak occurance in 15-35 years old
• Involves a granulomatous reaction
• Varies in the level of inflammatory response
• Fever, pain, triredness, diarrhoea

Question 13

Sulphate-reducing bacteria

Answer 13

• Occur in 45% of healthy persons
• Reduce sulphate to sulphide in conjunction with an e- donating substrate
• Competes with methangoens for H2
• Commonest genus: Desulfovibrio
• Pathological role in the gut remains unclear