GI infections Flashcards
Where in GI tract are streptococci usually found
- Stomach
- Duodenum
- Jejunum
Where in GI tract are Staphylococci normally found
- Stomach
- Duodenum
Physical and chemical defenses in GI tract?
- Enzymes in saliva and small bowel
- Acidic stomach environment
- Bile in small bowel
- Mucosa and mucin
Immune system GI specific defences
Secreted IgA
Peyer’s patches in SI
Risk factors for GI tract infection
- Immunodeficiency
- Poor sanitation
- Diabetes
- Unclean water
- Undercooked food
- Travel
bacterial characteristics of H. pylori
- Gram -ve spiral
- Bacillus
- Microaerophile, motile and urease positive
Signs and symptoms of H. pylori infection
- Epigastric pain, nausea, vomiting, haematemesis
- 20-30% population affected - faecal/oral oral/oral transmission
- Chronic gastritis; antrum or duodenal ulcer
Treatment for H.pylor infection
triple therapy antibiotics plus omeprazole
Causes of acute gastroenterisits
- Viral: Rotavirus, adenovirus, norovirus
- Bacterial: E.Coli, salmonella, shingella
- Toxins: C. difficile, S. aureus, B. cereus, C. perfrinegens
- Parasites: Giardia lambliem entamoeba histolytics
Investigation of gastroenteritis
- History and examination
- Blood cultures
- Stool samples
- Microscopu
- Culture
- Antigen detection
- Toxin
Characteristics of viral gastroenteritis
- Faecal/oral spread, incredibly infectious
- 24-48 hrs incubation, explosive diarrhoea
- Supportive managment e.g. ORT
Characteristics of Enterotoxigenic Bacterial Gastroenteritis
Enterotoxigenic
- Heat labile and stable toxins
- Abdominal pain
- RAPID 12hr incubation
- ORT
Characteristics of Enterohaemorrhagic Bacterial Gastroenteritis
- E. coli 157
- From mild diarrhoea to HUS in 8%(life-threatening)
- 2-10 day incubation
- Person/Person
- DO NOT give antibiotics
Subtypes and characteristics of salmonella
- Common: Enteridis
- Severe: Typhis, paratyphi…..sepsis
- Usually self-limiting diarrhoeal illness
- Diagnose via stool or blood
Ciprofloxacin if severe
Characteristics of shigella infection
- Subspecies: S. dysenteriae, S flexneri, S boydii
- Severe: Dysentry; haemorrhagic colitis, fluid loss, choxk
- Incubation 1-3 days
- Faecal/oral
- Stool
Campyolobacter infection characteristics
C. jejuni, C.coli
- From food, water, chicken
- 2-5 days
- Malaise, abdominal pain, fever, nausea, vomiting
- Diagnose with selective agar
Characteristics of parasitic GI
Cryptosporidium parvum, Giardia lambia, Entamoeba histolytica
Water borne due to faecal contamination
7-10 days
Giardia/entamoeba: metronidazole
Cryptosporidium: Self-limiting
Two main forms of liver infections and their causes
-
Heaptitis
- Inflammation of the liver by hep viruses
-
Liver abscesses
- Amoebic (entamoeba)
- Pyogenic(polymicrobial)
Pre-icteric clinical features of viral hepatitis
=preceding appearance of jaundice
- Malaise
- Anorexia
- Nausea
- Abdominal discomfort
- Pyrexia
Icteric features of viral hepatitis
- Pale stool; pigments not leaving via faeces
- Dark urine; Increased bilrubin in blood, filtered in kidneys
- Jaundice, from increased bilrubin
Characteristics of HAV
- Positive single stranded RNA genome
- Unenveloped
Characteristics of HBV
- DNA genome
- Partially double stranded
- Complete circle of dna with incomplete complementary strand
- Partially double stranded
- 3 antigens
- Surface HBsAg
- Envelope lipid
- Core HBcAg
- Surface HBsAg
- HBeAg
Characteristics of HCV
- Positive single stranded RNA
- Related to yellow fever, dengue
- Enveloped
Non-viral causes of hepatitis
Leptospirosis
Brucellosis
Spread, Clinical features and prevention of Hep A
Spread: Faecal oral via food, water
Features:
- Asymptomatic in children
- Acute icteric hepatitis; potentially fulminant
Prognosis: If survived, immunity gained
Vaccination
Spread of HBV
Perinatal
Sexual MSM
Parenteral: Unsafe injections, transfusions
Clinical features/outcomes of HBV in adults
Acute:
- Subclinical most common
- Acute icteric hepatisis indistinguishable from hep A
- Fulminant hepatitis more common in B than A
-
Chronic infection 10%
- Healthy, unaware
- Chronic hepatitis; immune response, death of hepatocytes
- Cirrhosis 20-30 yeards
- Cancer
Outcomes of HBV in neotates
- Subclinical
- Acute icteric hep
- Fulminant hep
- Chronic infection: 90%
- Immune system isnt mature
- Cirrhosis; death in 30-40s
- Passed on vertically
Detecting HBV
3 antigens:
HBsAg: shows infection, not when.
- Over 6 mnths is chronic
HBcAg
HBeAg
3 corresponding antibodies
IgM Anti-HBc: Shows recent exposure to antigen
- If negative, chronic hepatitis
Distinguishing between different non a, non b hepatitis
Diagnosis of Hep C
- Genetically diverse, chance of false negative
-
Anti-HCV detection
- Infection at some time
-
HCV RNA detection
- Current infection
Causes of cholesystitis
=infection of gall bladder
- Seconary to gall stones
- Gut organisms
Features of cholesystitis/cholangitis
Abdominal pain
Rigors
Fever
Jaundice
Virus causing splenomegaly
EBV
Pancreatitis due to:
Gallstones, alcohol
Secondary to bacterial infection
