GI infections Flashcards by Peter Weir

Where in GI tract are streptococci usually found

Stomach
Duodenum
Jejunum

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Where in GI tract are Staphylococci normally found

Stomach
Duodenum

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Physical and chemical defenses in GI tract?

Enzymes in saliva and small bowel
Acidic stomach environment
Bile in small bowel
Mucosa and mucin

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Immune system GI specific defences

Secreted IgA

Peyer’s patches in SI

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Risk factors for GI tract infection

Immunodeficiency
Poor sanitation
Diabetes
Unclean water
Undercooked food
Travel

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bacterial characteristics of H. pylori

Gram -ve spiral
Bacillus
Microaerophile, motile and urease positive

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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

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Treatment for H.pylor infection

triple therapy antibiotics plus omeprazole

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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

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Investigation of gastroenteritis

History and examination
Blood cultures
Stool samples
- Microscopu
- Culture
- Antigen detection
- Toxin

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Characteristics of viral gastroenteritis

Faecal/oral spread, incredibly infectious
24-48 hrs incubation, explosive diarrhoea
Supportive managment e.g. ORT

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Characteristics of Enterotoxigenic Bacterial Gastroenteritis

Enterotoxigenic

Heat labile and stable toxins
Abdominal pain
RAPID 12hr incubation
ORT

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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

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Subtypes and characteristics of salmonella

Common: Enteridis
Severe: Typhis, paratyphi…..sepsis
Usually self-limiting diarrhoeal illness
Diagnose via stool or blood

Ciprofloxacin if severe

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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

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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
3 antigens
- Surface HBsAg
  - Envelope lipid
- Core HBcAg
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:** 1. **Subclinical** most common 2. **Acute icteric hepatisis** indistinguishable from hep A 3. **Fulminant hepatitis** more common in B than A 4. **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