GI tract infections Flashcards
(31 cards)
Outline host defence mechanisms to prevent GI tract infections
Physical and chem barriers- stomach acid, digestive enzymes, mucous lining and mucin
Continuous movement
Immune system- secreted IgA and Peyer’s patches
List common inhabitants of the stomach
Candida Streptococcus Lactobacilli H pylori Peptostreptococcus
List common inhabitants of the duodenum, jejunum and proximal ileum
Lactobacillus
Streptococcus
List common inhabitants of the colon
Enterobacterium
Bifidobacrerium
Clostridium
bacteroides
List common inhabitants of the distal ileum
Clostridium Streptococcus Clostridium Actinomycinae Corynebacteria
List risk factors for infectious disease of the GI tract
Immunodeficiency Poor sanitation Unclean water Undercooked food Travel to high risk areas
Outline the clinical features, investigations and management of H pylori
Chronic gastritis
Duodenal ulcer disease
Inflam response
Assoc with gastric adenocarcinoma
Urease breath test, endoscopy, gastric biopsy, serology
Treatment- triple therapy and proton pump inhibitor
List the main organisms causing acute diarrhoeal diseases
Viral- adenovirus, rotavirus, norovirus
Bac- E coli, salmonella, Shigella, V cholera
Toxins- C difficile, s aureus, B cereus
Parasites- giardia, entamoeba, cryptosporidium
List the main organisms causing food associated diarrhoea
Campylobacter
Salmonella
E coli
Bacillus staphylococcus and clostridium
List the main organisms causing travel associated diarrhoea
Contaminated food or water Bac and parasites E coli most common Salmonella, Shigella, V cholerae, Campylobacter Giardia and entomoeba
Outline investigation of gastroenteritis
History and examination Blood cultures Stool -> microscopy-> ova, cysts, parasites -> culture-> salmonella, shigella -> antigen detection-> rotavirus, adenovirus -> toxin testing-> c.diff
Outline viral gastroenteritis
Faecal-oral spread Explosive diarrhoea, often with vomiting - Incubation 24-48 hrs Detect by antigen testing/PCR Rehydration
Outline E Coli
Common, most strains don’t cause GE
Enterotoxigenic, invasive, pathogenic, haemorrhagic do
TOXIGENIC- traveller’s diarrhoea
12 hr incubation
Outline campylobacter
Diarrhoea, abdo cramps, vom From raw/poorly cooked food- chicken (BBQ) 2-5 day incubation Culture with selective agar Self limiting
Outline salmonella
Enteriditis- cause GE, self limiting
Typhi and paratyphi- typhoid or paratyphoid fever- IV ceftriaxone
Outline shigella
Several species
S dysenteriae- severe
Bloody diarrhoea, HUS
1-3 days incubation
Outline parasites
Water borne
Give metronidazole
Outline clostridium difficile
Anaerobic spores- survive and spread- germinate into cells
Vegetative cells prod toxins
Colonise without disease- WORSEN WITH ANTIBIOTICS
give Metronidazole or Vancomycin
Outline the clinical features of viral hepatitis
Hep A B C E
A and E faecal oral, BCD- paraentral and sex
Inflam of liver- vital
Icteris= jaundice
Pre icteric- malaise, anorexia, nausea, RUQ discomfort, pyrexia
Icteric features- pruritis, pale stools, dark urine, jaundice
List the non viral causes of hepatitis
Leptospirosis
Bucellosis
What is hepatitis secondary to?
EBV
cytomegalovirus
Outline Hep A, its transmission, epidemiology and prevention
Simple virus
+ve ssRNA genome
Faecal oral transmission
Contam food/water
Early childhood, less severe
Prevent- take care with food and water
Vaccination is with whole killed virus
Outline Hep B, its transmission, epidemiology and prevention
Unusual virus, DNA not RNA, partially double stranded
Encodes a few proteins- Core Ag (capsid), surface Ag, eAg in some patients
Transmission: perinatal (mother to baby), sexual, paraentral- unsafe injections and transfusions
Virus in blood and bodily fluids
300m HBV carriers worldwide, uneven distribution
Prevent:
- Passive immunity- Hep B immunoglobulin
- Active immunisation- Hep B vacccine- HbS Ag only- induces anti Hb 90% effective
- UK- selective vaccine- low prevalence, only at risk groups vaccinated- healthcare/sex workers, drug users, sexual partners and offspring of carrier
Outline Hep C, its transmission, epidemiology and prevention
Flavirus- RNA- same as yellow fever
Dengue, West Nile etc
1-6 genotypes- most genetically diverse in humans
With >30% diff in genome sequence
>100 subtypes worldwide
Quasispecies- closely related sequences in an individual
Transmission- paraenteral
Blood borne viruses- infection, transfusion, needles, Egypt
Massive gen diversity- false negatives on diagnosis
Genotypes vary in pathogenicity and therapy response
Chronic- males- elderly, alcohol intake increased
