Normal Microbiota

Define 'normal microbiota':

organisms that colonize the body's surfaces in a state of health

Define 'colonisation':

establishment at a site in the body

Define 'microbiota':

all the organisms in a given community

Define 'microbiome':

all the genes present within a microbiota

Define symbiosis:

two or more organisms co-existing in close physical association

What is mutalism?

where both organisms benefit from symbiosis

What is neutralism?

where neither organism derives benefit or harm from symbiosis

What is commensalism?

where one organism benefits and the other derives neither benefit nor harm from symbiosis

What is parasitism?

where one organism (parasite) benefits at the expense of the other host

What is dysbiosis?

a pathobiont shift in microbiota causing a disease state

What does pathobiont mean?

can cause pathogenic harm under certain circumstances

What is a non-sterile site?

a site with normal flora

What is a sterile site?

a site with no normal flora

Give 5 non-sterile sites found in the body:

1) conjunctiva of the eyes

2) skin

3) vagina

4) nasopharynx

5) GI tract

Give 3 mechanisms used by sterile sites to maintain sterility:

1) surface cleaning

2) barriers

3) physical separation

Give an example of a sterile site that uses surface cleaning to maintain sterility:

lower respiratory tract

Give an example of a sterile site that uses barriers to maintain sterility:

the upper genital tract protected by the cervix

Give 4 examples of sterile sites that use physical separation to maintain sterility:

1) pleural cavity

2) peritoneal cavity

3) spinal cord

4) meninges

Describe the potential risk of contamination when taking blood for blood cultures:

passing a needle through the skin (non-sterile) to a sterile site

Describe the potential risk of contamination when taking sputum samples:

the sputum is obtained by expectoration of lower airway secretions (sterile site) through the upper airway (non-sterile site)

Describe the potential risk of contamination when taking urine samples:

urine is passed from the bladder and upper urinary tract (sterile sites) and through the terminal urethra (non-sterile site)

How is the potential for contamination minimised when taking urine samples?

taking a mid-stream urine sample (MSU)

What is tissue tropism?

the propensity for a particular organism to grow in a particular habitata

Give 5 physical variables effecting tissue tropism at different growth sites:

1) pH

2) moisture

3) temperature

4) O2 availability

5) nature of surface

Give 3 species of normal flora found on this skin:

1) coagulase-native Staphylococcus

2) Staphylococcus aureus

3) Cutibacterium acnes

True or false: the bacteria on the skin near any orifice may be similar to those in the orifice

true

Describe the skin as a growth site (3)

1) aerobic

2) nutrient poor

3) variable temperature

What name is given to the V shaped crevice that surrounds each tooth?

Gingival crevice

Describe the gingival crevice as a growth site: (3)

1) anaerobic

2) bathed in nutrients

3) constant temperature

Give three groups of bacteria found in gingival crevices:

1) Viridans

2) anaerobes

3) red complex bacteria

What are Viridans?

oral streptococci

Give 5 examples of red complex bacteria:

1) Aggregatibacter actinomycetemcomitans

2) Treponema donticola

3) Prevotella intermedia

4) Tannerella forsythia

5) Porphyromonas gingivalis

Give 5 examples of normal flora found in the pharynx:

1) Streptococcus pyogenes

2) Haemophilus influenzae

3) Streptococcus pneuomoniae

4) Neisseria meningitidis

5) Staphylococcus aureus

Describe the normal flora of the vagina before puberty:

the vagina is colonised by skin flora and lower GI flora (mainly E. coli)

Describe the changes to vaginal flora after puberty:

1) glycogen is produced due to circulating oestrogens

2) Lactobacillus subsequently colonises the vagina as it ferments glycogen

3) fermentation of glycogen maintains an acidic pH of 3, preventing the overgrowth of other species

Give two types of aerobic bacteria found in the acidic region of the stomach:

1) Lactobacilli

2) H. pylori

Which type of bacteria is more abundant in the colon - aerobes or anaerobes?

anaerobes

Give two examples of abundant anaerobes found in the colon:

1) Clostridiums

2) Bacteriodes

Give an example of an aerobic bacteria found in the colon:

Escherichia coli

How does normal flora benefit our metabolim?

flora is involved in the synthesis of secondary metabolites and vitamins

What two vitamins do enteric bacteria secrete, aiding our metabolism:

vitamins K and B12

Give two ways in which normal flora provide resistance to colonisation from pathogens:

1) some flora can manipulate the environment e.g. lowering the pH

2) some flora can produce antibacterial agents

What is a becateriocin?

a protein produced by a bacteria that acts against bacteria of other strains

How does normal flora aid our immune regulation?

it helps maintain balance between pro and anti-inflammatory factors

Give two ways in which normal flora are beneficial in the nose:

1) aid mucous production

2) secretion of anti-microbial chemicals

Give two ways in which normal flora are beneficial in the mouth:

1) assists digestion

2) ward off other pathogens

Give one way in which normal flora are beneficial in the lungs:

lubricates pulmonary tissues

Give one way in which normal flora are beneficial in the stomach:

prevents gastric complications

Give one way in which normal flora are beneficial in the colon:

digestion of complex carbohydrates

Give one way in which normal flora are beneficial in the sexual organs:

maintains pH and H2O2 production to kill microbes

Give one way in which normal flora are beneficial in the skin:

fortifies the immune system

Give three examples of intestinal short chain fatty acids produced by normal flora that help maintain general health:

1) acetate

2) butyrate

3) propionate

Give 4 ways in which intestinal short chain fatty acids maintain health:

1) helps to inhibit enteropathogens

2) provides energy to epithelial cells

3) promotes mucin production

4) affects gut hormone production and regulates appetite

What is the most common cause of Clostridium difficile infection?

antibiotic treatment disrupting normal colonic microflora

Give 3 broad treatment methods for dysbiosis:

1) probiotics

2) prebiotics

3) faecal transplants

What are probiotics?

live microbes applied to or ingested into the body intended to exert a beneficial effect

What are prebiotics?

nutrients that encourage the growth of beneficial microbes

What is overgrowth (type of dysbiosis)?

excessive growth at a normal site

What is translocation (type of dysbiosis)?

presence of microbes at the wrong site, often by the spread from one surface to another or inoculation intoa normal sterile site

What is cross-infection (type of dysbiosis)?

the transfer of microbes to a hospital patient with a different infection