12- Human Microbiology Flashcards
Overview: Normal human microbiome
- microorganisms usually associated with human body tissue
- colonization begins at birth
- microbiomes changes over time: depending on the condition the host is subject to
Most organism are commensal, few beneficial, even less parasitic
Epidermis
Skin
Composed of:
-dead outerlayer
-living actively replicating innerlayer
Sebatious and Apocrine sweat glands
Secretes: - Salt water - Various amounts of proteins - Lipids - Sugars Secretions has an antimicrobial effect thanks to lipids and proteins
Dead cell outer skin layer
Creates a tough outer barrier to prevent penetration of microorganism
Generally dry and acidic: does not support the growth of microorganisms
Skin ducts
Secretious ducts cary a small colony of well adapted gram-possitive bacteria:
Skin duct microbiome
Secretes : bacteriocin, and aerotolerant propionobacterium acnes Inhabitants : - Yeast -Molds -Bacteria
Bacteriocon
kills incoming microorganic competitors, and protects against harmful bacterial colonization
Oral cavity microbiome
heterogeneous microbial habitat : both aerobic and anaerobic niches
High nutrient concentration promotes growth
Teeth: structure
Outer miniral matrices : Enamel
Enamel surrounds living tissue: dentin and pulp
Dental placke formation
bacteria attaches to acidic glycoproteins deposited from saliva
extensive growth of microbes (streptococci) -> thick bacterial layer : plaque
Streptococcus mutants
synthesizes extracellular polysaccharides : Dextran ferments lactose (along with lactobacteria) -> produces lactic acid
Dextrain
synthesized by streptococcus mutant
extra cellular polysaccharide
aids in bacterial attachement to tooth surface
Lactic acid: plaque formation
lactic acid produced by Streptococcus mutants and lactobacteria degrades tooth enamel
Solubilizes calcium
Stomach : major processes
secretion of acid: HCl
digestion of macromolecules
pH: 2
Small intestine : major processes
continued digestion & absorption of : - monosaccharides - amino acids - fatty acids - water pH: 4-5
Large intestine : major processes
absorption of bile acids, vit B12
pH: 7
Gastrointestinal [GI] tract of humans
colonization begins at birth
mibiomes differ in different areas of the GI determined by :
- diet
- physical environment
Colonizing the GI tract
Prevented by the acidity in the stomach, dueodenum, and S intestine
Organism in food may be protected
Microorganisms in the colon
mostly strict anaerobes/ facultative nanaerobes Organisms: - Bacterioides - enteric bacteria (E. coli) - yeasts - anaerobic protozoa (Entamoeba coli) Variability between individuals
Microorganism in the colon: function
Digest :
- complex carbohydrates (cellulose, starch)
Produce: VFA’s (volatile fatty acids)
Microorganism in the large intestine : function
Ferment : volatile fatty acids
Produce gasses : CO2 & H2
Methanogens : convert CO2 and H2 -.> CH4
Sulfate reducers & cysteine/methionine fermenters: produce H2S
Nutrients produced by intestinal microorganisms
- amino acids
- vitamins: B12, K, thiamine, riboflavin
Applications of GI tract microbiome
Microorganisms contribute to the maturing of the Gi tracts Microbiome affect: - early development - health - predisposition to disease (obesity)
Microbiomae of the nose and nasopharynx
- staphylococci
- streptococci
- corynebacteria
Pathogens in the nasopharynx
The nasopharynx may contain pathogens under control by the immune system:
- Streptococci pneumoniae
- Haemophilus influenza
- neisseria meningitidis
Upper respiratory tract
- Sinuses
- Nasopharynx
- Pharynx
- Oral cavity
- Larynx
Lower respiratory tract
- Trachea
- Bronci
- Lungs
Until recent studies LRT was considered microbiomeless : low biomass
Genitourinary tracts
Men & women : generally free of microorganisms
Regular urine flushing
Urethra pathogens
Possibly from GI tract: may cause disease
altered condition cause colonization-> disease
Vaginal tract microbiome
Variety of microbiomes depending on age
the vaginal tracts and glycogen
Glycogen concentrations controlled by hormones
Glycogen is degreaded by microorganisms -> lactic acid
Vaginal pH: 4.5
Sterile zones of the human body :
- blood
- spinal fluid
- internal urinary tract (bladder, kidneys)
- Peritoneal cavity (gut cavity)
- Pleural cavity (lung cavity)
- Sinuses
- Interior regions of other body tissue (bones, muscles…)
