L30 - Introduction To The Human Microbiota And Barriers To Infection Flashcards
What is the microbiome?
Microorganisms present on all of our body surfaces
What is microbiota?
Groups of microorganisms living in a specific environment
What is microbiota like?
- not usually harmful, often vital to health
- individuals microbiota usually unique
- indigenous human commensals
What are indigenous human commensals like?
- beneficial for bacter and the host
- provides some protection against pathogens
What is the gut microbiome essential for?
Essential for breakdown of our food
What does the gut microbiome do?
synthesise essential vitamins B12 and vitamin K
What does reserach suggest the gut microbiome is invovled in?
Obesity, allergies, mental health, immune disorders, etc.
What are opportunistic pathogens?
Indigenous human commensals causing harm when the status quo perturbed
What are examples of opportunistic pathogens?
- burn patients - pseudomonous aeruginosa, gram neg
- colonic bacteria - UTI - Ecoli, gram neg
- skin flora - wound infection - staph, gram pos
- oral flora - tooth decat - strep, gram pos
What are normal human microbiota?
- skin
- upper resp tract - nose and throat
- lower resp tract
- digestive system - mouth/stomach/SI/LI
- urinary tract
- adult femal genital tract
What are the 3 microenvironments that the skin is divided into?
- dry skin - arms and legs
- moist skin areas - armpits
- areas rich in sebaceous glands
What are natural colonisers to skin?
Gram pos bacteria // staph, strept
What is the microbiota in the nose and throat?
- extensive bacteria flora
- natural colonisers - strept, staph, //neiseria and haemophilus
What causes bacterial meningitis in the nose and throat?
- streptococcus pneumoniae
- neisseria memningitidis
- haemophilus influenza
What is the lower respiratory tract like?
- usually sterile
- common site of infection // chest infection, pneumonia, tuberculosis (mycobacterium tuberculosis)
What is the mouth (digestive system) microbiota like?
- gingival groove - anaerobes // bacteroides,, actinomyces = gum disease
- tooth enamel - facultative aerobes // strep = plaque, tooth decay
- cheek and gums - facultative aerobes // strep = colonise saliva
What is the stomach (digestive system)microbiota like?
Acidic <10cfu/ml
Helibacter pylori
What is the small intestine (digestive system) microbiota like?
- duodenum - 10^3-10^4 cfu/ml, still acidic/still enzymes
- ileum - 10^5-10^7 cfu/ml, less acidic
What is the large intestine (digestive system) microbiota like?
- 10^12 microorgs/g faeces
- gram pos, and gram neg bacteria 3000 dif species
- anaerobes and facultative anerobes // bacteroides fragilis, enterococcus faecalis, e.coli
What is the urinary tract microbiota like?
- kidneys, ureters and bladder - usually sterile
- urethra - lightly colonised, staphylococcus epidermidis
- frequent site of UTI, E.coli, enterococcus faecalis, proteus mirabilis
What is the adult femal genital tract microbiota like?
- complex microbiota
- depends ona ge, childbirth, menopause and menstrual cycle
- // lactobacillus pH 5.5-6.5, candida albicans
What are non specific defences agsint infection?
Barriers
- skin
- mucosal surface
- blood and tissues
What are defences like in commensals?
Pathogen must compete with natural microflora for adhesion sites and food
What are probiotics?
Live microorgs that prevent/treat conditions // antibiotic associated dirrhoea
What are prebiotics?
Chemicals that induce growth/activity of microorgs - promote health
What are the defences of skin?
- epidermis
- sebaceous gland (associated with hair follicles)
- skin associated lymphoid tissue (SALT)
- sweat gland
What is epidermis like as a defence of skin?
- physical barrier
- dry, acidic
- shedding cells
- indigenous bacteria - dec colonisation
What are sebaceou glands like as defence of skin?
Lysosyme
What are SALTs like as a defence of skin?
Induces local inflammatory response
What are sweat glands like as defence of skin?
Lysozyme
What are the defences of mucosal surfaces?
- mucus
- epithelium
- mucosal associated lymphoid tissue (MALT)
What is mucus like as a defence of mucosal surfaces?
- traps bacteria
- lysosyme kills gram pos bacteria
- lactorferrin binds iron
- lactoperxodase kills bacteria
What is epithelium like as defence of mucosal surfaces?
- physical barrier
- shedding cells
- cilia
- indigenous bacteria - dec colonisation
What is MALT like as defence of mucosal surfaces?
Induces local inflammatory response
What are barriers to infection?
- eyes
- skin
- trachea
- lungs
- blood and lymph
- stomach
- digestive tract
- genital tract
- urinary tract
How are eyes as a barrier to infection?
Washing by tears, lysozyme
How is skin as a barrier to infection?
- normal flora
- swear
- antimicrobial fatty acids
How is trachea as a barrier to infection?
Mucus and cilia to move microbes out of the body
How are blood and lymph as a barrier to infection?
Proteins beneath skin inhibit microbial growth
How are lungs as a barrier to infection?
mucus and phagocytes prevent invasion
How is the stomach as a barrier to infection?
Low ph inhibits microbial growth
How is the digestive tract as a barrier to infection?
- microbial growth inhibited by rapif pH change
- normal flora, enzymes, and bacteriocins prevent infection
How is the genital tract as a barrier to infection?
Normal flora, acidic environment
How is the urinary tract as a barrier to infection?
Urine acidicty and flushing prevents microbial growth
What are non specific defences of blood and tissue?
from myeloid stem cell
- basophil - inflammation
- neutrophil and eosionphil - kill bacteria
(Polymorphonuclear PMN leukocytes, granulocytes)
- monocytes - phagocytosis, produce cytokines
- induce inflammatory response
- present antigen to Tcells
What are the events in phagocytosis?
- chemotaxis
- adherence
- ingestion
- phagosome
- fusion
- killing of microbe
- discharge
What do lysosomes contain?
- digestive enzymes
- defensins
- enzymes of respiratory burst
What are other non specific defences of tissue and blood?
- complement
- transferrin
- mannose-binding lectin
What is the complemet system?
- biochemical cascade
- activated following infection
What are the steps in the complement system?
- lysis - complement to target cell
- opsonisation - phagocytosis
- activation of inflammatory response - extravasation, degranulation
- clearane of immune complexes - ag-ab complex in phagocyte
What does transgerrin do as a defence of tissue and blood?
binds iron
What does mannose binding lectin do as a defence of tissue and blood?
- soluble factor made after infection
- binds to patterns on microbial surfaces
- inc complement activation
- inc opsonisation
