Microorganisms in GI tract Flashcards
What are the benefits provided by the normal microbiota?
- Nutrient and micronutrient availability
- Terminal postnatal differentiation of mucosal structures
- Physical barrier function
- Immune system development
- Regulation of metabolism
- Colonization resistance against pathogens
True or False: All pathogens are commensals when contained within the GI tract.
True
When pathogens cause disease, they become classified as ‘pathogens’.
What are the protective factors in the GI tract’s antimicrobial immunity?
- Barrier function
- pH
- Flow rate
- Bile salts/digestive enzymes
- Redox potential/oxygen tension
What are common pathogenic mechanisms in the GI tract?
- Adherence mechanisms
- Motility
- Toxin production
- Resistance
- Avoidance of the immune system
What is the clinical manifestation of diarrhea?
Liquid stools with more than 80% of water
Diarrhea can be classified as osmotic, secretory, inflammatory, or due to motility issues.
Fill in the blank: _______ is a common cause of acute gastroenteritis characterized by watery diarrhea.
Vibrio cholerae
What are the clinical features of Vibrio cholerae infection?
- Watery diarrhea (‘rice-water stools’)
- Severe dehydration
What is the physiological characteristic of Helicobacter pylori?
Curved/spiral-shaped, gram-negative
Present in up to 50% of western adults and 100% in the developing world.
What diagnostic methods are used for Helicobacter pylori?
- Biopsy and histology/culture
- Urea breath test
- Antigen in stools
What are the virulence factors of Vibrio cholerae?
- Pili (adherence to mucosae)
- Toxin production
What is the clinical case presentation for Vibrio cholerae?
Acute gastroenteritis with nausea, vomiting, and aqueous diarrhea
The majority of patients have no pain or fever.
What is the treatment for Vibrio cholerae infection?
- Rehydration
- Antibiotics (if necessary)
What is the importance of microbial balance in the gastrointestinal tract?
Maintains health and prevents disease through various mechanisms
Disruption can lead to infections or diseases such as IBD.
What are the key clinical features of bacterial dysentery?
Bloody diarrhea (+pus/mucus) + Abdominal cramps + Fever
Which pathogens are examples of GI pathogen infections?
- Helicobacter Pylori
- Vibrio cholerae
- Shigella spp
- Clostridioides difficile
How is Shigella primarily transmitted?
Contaminated water or food, very low infectious load
What is the role of shiga-toxin produced by S. dysenteriae?
It causes inflammation of the gut epithelium
What is the physiopathology of Shigella infection?
Bacteria enter mucosal cells via M-cells, ingested by macrophages, leading to apoptosis, cytokine release, inflammation, and tissue destruction
What are potential complications of a Shigella infection?
- Local: toxic megacolon
- Systemic: Autoimmune
What is the diagnosis method for Shigella infection?
Stool culture and PCR
What are typical treatments for Shigella infection?
- Ciprofloxacin
- Azithromycin
What is the primary cause of nosocomial diarrhea?
Clostridioides difficile
What are the clinical features of Clostridioides difficile infection?
- Asymptomatic carriage
- Diarrhea / simple colitis
- Pseudomembranous colitis
- Fulminant colitis
What are the common treatments for Clostridioides difficile infection?
- Metronidazole
- Vancomycin
- Fidaxomicin
- Probiotics
- Faecal transplants
- Immunotherapy
