University:
Swansea University
Course:
PM134 | Microbiology
Academic year:

2023
Views:

101

Pages:

2
Author:

Yasin N.

PathogenesisIN SHORT : Ingestion - Gut - ileal mucosa - Submucosa - Phagocytosis - Multiplication withinmacrophages- Mesenteric Lymph node- Thoracic duct - Blood stream - Multiple organsIn detaila. Source - Contaminated food, water and milk or carriers, case of typhoid fever, carrier ofpathogen. LRisk Factors: Decrease in stomach acidity by taking antacids or infections such as helicobacterpyloriInflammatory bowel disease, suppression of intestinal flora by antibioticsThis can increase the chances of getting infectedb. Mode of Entry : IngestionC. Infective dose : 10^3-10^6 bacillid. Events:1. Bacilli reaches the gut2. Attach to microvilli of Ileal mucosa3. Penetrate lamina propria to reach submucosa4. Phagocytosis by PMNL and Macrophages5. They have ability to resist intracellular killing and multiply within the macrophagesand PMNL & multiplies6. Enters Mesenteric Lymph node & multipliesPathogenicity Island: Itsimply means series of contagious genes that codes for virulence, more of theseare present more will be the virulence7. Enters Bloodstream through thoracic duct - TRANSIENT/PRIMARY BACTEREMIA8. Further spreading occurs via RES system to Liver, Spleen, Bone Marrow,Gallbladder, Lymph nodes etc9. Multiplies within macrophages of the organ10. Massive BACTEREMIA - it takes about 7-14 days and onset of clinical diseaseNote : Gall bladder contains Bile which is a very good culture medium for growth ofbacteria, so they are continuously discharged into intestine and multiply in Peyer'spatches which can cause inflammation, necrosis and Ulcer (TYPHOID ULCER)Culture medium used- Mac Conkey's agar producing Non Lactose Fermenter (NLF)colonies.