INF1 - E. GI INFECTIONS-COVERED Flashcards
1
Q
where can bacteria enter the body
A
- resp tract
- GI tract (includes mouth!)
- urogenital tract
- breaks in skin surface
2
Q
what causes food borne illnesses
A
- viruses (norovirus, hepatitis A) - most common cause of gastro-enteritis
- bacteria (salmonella, campylobacter)
- parasites (tapeworms in contaminated food)
- prions (BSE in cattle and therefore in contaminated meat)
- chemicals
3
Q
how to GI pathogens infect us
A
- microbes live in GIT
- released in faeces of animals/humans
- ingested of organisms and toxins by humans by food, fluids, fingers
- organisms multiply and toxins produced, infection remains localised in GIT = diarrhoea/vomiting
or - organsims invade/ toxins absorbed and infection spreads = systemic infection symptoms
- pathogen excreted in faeces
4
Q
how does bacteria attach to host cells
A
Loose association of bacteria to mucous layer then attachment and entry of bacteria into epithelial cell, bacteria can then enter bloodstream
- direct protein-protein interaction
- indirect interaction with slime layer or capsule
- fimbriae and pili on surface of bacteria
5
Q
what are exotoxins
A
- secreted extracellularly by gram-ve and gram+ve cells
- proteins and heat labile
- ie: cytolytic toxins, A-B toxins, superantigen toxins
- if systemic: highly toxic, antigenic, fever, adhesion to specific host cell receptors
6
Q
what are enterotoxins (entero/enteric = intestine)
A
- form of exotoxin
- secretion of fluid into lumen of small intestine
- proteins and heat stable
- produced by enteric pathogens: V. cholera, E. coli
7
Q
what are endotoxins
A
- LPS present on cell wall of gram-ve bacteria (cell lysis)
- breakdown of LPS gives rise to lipid A, core polysaccharide, O-polysaccharide
- fever and diarrhoea, reduced white blood count, release of cytokines, infammation
8
Q
what is the microbiome
A
ecological community of commensal, symbiotic and pathogenic microorganisms found in and on all multicellular organisms
9
Q
what is microbiota
A
specific micro-organism living at a specific site ie - gut microbiota
10
Q
what does the microbiome do
A
- involved in maturation and development of our immune system
- involved in metabolism of some nutrients that we can’t perform ourselves
- competition and habitat filtering: colonisation resistance
- conversion of fibre into fermentation products: nutrition
- detection of metabolites by host cell receptors: immune education
- if balance is disrupted = colonisation/over-population of certain microbes, infection and disease
11
Q
what does the GIT microflora consist of
A
- 10^14 bacteria
- majority in lower GIT (anaerobic compared to upper GIT which is aerobic)
- bacteria, archaea, fungi, bacteriophages
- one of the most dense and complex microbial ecosystems
12
Q
what is the role of the GI microbiota
A
- digest materials by producing enzymes the host doesn’t and provide important materials
- indigestable plant sugars converted into short chain fatty acids
- biotin (vitamin B7) - coenzyme for carboxylase enzymes
- panthotenic acid (vitamin B5) - essential for production of nucleotides
- folic acid (vitamin B9) - essential for production of nucleotides
- precursor to vitamin K - required for blood clotting - compete with pathogenic microorganisms
- reduces risk of colonisation by pathogenic microorganism via competition
- removes nutrients
- changes extracellular pH - influences immune system
- improves response to pathogenic bacteria
- modulates the function of the T-cells in gut epithelium
13
Q
what are probiotics
A
- microorganisms that live in gut (bacteria and yeast)
- probiotic foods contain beneficial organisms that help colonise and populate gut
- foods: yoghurt, tempeh (any fermented food)
14
Q
what are prebiotics
A
- indigestible food ingredients that act as a food source for probiotics
- foods: leeks, garlic, onion, legumes
15
Q
what infections can you get in the GIT
A
- mouth: periodontal disease
- stomach: gastric ulcer disease and gastroenteritis
- intestines: gastroenteritis, diarrhoea, dysentery, enterocolitis (C.diff)
