MCB E4: Commensals

1. our normal microbiota

2. our disease resistance mechanisms

A healthy human system is maintained by two major components

Pathogen

disease producing microorganism

Virulence

determined by quantitative measure on severity of pathogen

Colonization

healthy carrier but not infected by pathogen

Infection

situation where microbe colonizes and then establishes __ leading to disease.

Disease

damage or injury to host

Loose association

microbe is shed on daily basis

Tight cell-to-cell interaction

where microbial cells firmly attach to carbohydrates, lipids, or proteins on host cells

Normal specific interaction

methanogens adhere to receptors in the gut

Abnormal specific interaction

pathogen firmly attached to receptors in the gut

Normal flora

the microbes normally found at an anatomical site

commensals

relationship where one partner benefits, while the other partner may or may not benefit but is not harmed. Is situational

1. shape/train immune system and responses

2. prevent attachment and/or colonization by pathogens

3. defend system by producing molecules that kill/inhibit the growth of pathogens

4. different commensals, within a group of microbes control the growth of each other

beneficial roles of commensals

situational or opportunistic

commensalism can be ?

1. overgrowth of commensals (UTIs or brochitis)

2. pathogens attach to commensals that enter human system

examples of opportunistic commensals

positive

Most commensals are G_ attached within microscopic crevices in the skin and not easily removed with washing. ex sweat and follicular glands are major colonization sites

negative

Most transients on exposed skin are G_ that do not grow well in the dry environment found on the skin

staph epidermidis, corynebacteria, proprionibacterium, yeast and other G-

what are examples of skin commensals?

G+ facultatives

what gram stain is staph epidermidis and corynebacteria

Proprionibacterium

• G+ anaerobe

• colonizes skin glands, breaking down host lipids

• generates body odor

• takes advantage of hormonal overproduction

staph epidermidis and aureus

what organism would reside in the nostrils, where it is cooler, O2, and many receptors

Nasopharynx

• tonsillar crypts

• anaerobes,

• 5-15% healthy carriers

• Strep, corynebacteria, neisseria, and haemophilus

Oropharynx (throat back of mouth)

• a-hemo strep: normal flora

• B-hemo strep: strep throat, can be carried by healthy individuals

no

does the lower respiratory tract have normal flora

mucociliary blanket and phagocytic cells that reside in the respiratory tract

what are ways that the lower respiratory tract removes microbes?

Mucociliary blanket

way that respiratory tract removes microbes: moves particles upward cough reflex dislodges particle

Biofilm

• extracellular polysaccharide dextran

• adherence to hums and teeth

• causes dental caries: strep mutans, lactobacillus

• causes periodontal disease: bacteroides, campylobacter

plaque

biofilm that has hardened due to calcium and magnesium encrustation

no

can you culture the stomach’s normal flora?

flora of the stomach, helicobacter pylori

what causes peptic ulcer disease?

• pass through stomach quickly

• embedded in fatty food particles

• ingested in bulk

How can transient microbes avoid being killed by stomach acid

the colon

which organ has the largest microbial population in the body

bacteriocins

small antimicrobial peptides produced by the normal flora that kill or inhibit the growth of pathogens

e coli

commensal that generates bacteriocins that can kill clostridia

no bacteria, but viruses

can bacteria be found in the kidneys

yes has a microbiome, but differs from male to female

can bacteria be found in the bladder

upper is no, but lower contains both G+ and G-

can bacteria be found in the male genital tract

acid tolerant lactobacilli predominate which kill bacteriocins that kill pathogens. Numbers change with hormones, stress and antibiotics

can bacteria be found in the female genital tract

commensals

occuys physical space on/in the human body which limits pathogen attachment and colonization. Secretes products/regulatory metabolites that affect other members of the microbiome as well as host.

1. chronic kidney disease

2. cardiovascular complications

3. abnormal immunity

healthy microbiome can prevent?

innate immunity

non-specific mechanisms

Adaptive immunity

specific mechanisms

Immune system

large network of cells, tissues, organs, cytokines, receptors, and more

antigen

foreign body that induces an immune response against something

Immunity

ability to resist a particular disease or infection

non-specific immune response

• intrinsic always on

• innate stimulated by inflammation

• generalized resistance

• no memory, does not improve with repeated exposure

Specific immune response

• adaptive or required immunity

• specific resistance to a specific foreign agent: antigen

• has memory: improves with repeated exposure to antigen

PRRs- pattern Recognition receptors

early non-specific detection of foreign molecules is largely based on a system of_

pro-inflammatory molecules

stimulation of PRRs causes cells to produce? cytokines/chemokines

Pathogen Associated Molecular Patterns

what does PAMP stand for

PAMP

includes LPS, peptidoglycan, lipoteichoic acid, flagella, nucleic acids

white blood cells or leukocutes

• involved in innate immunity

• found in blood, lymphatics, lymph nodes, etc

• all have PRRs on their surface but their responses differ

Dendritic cells

• phagocytic cells that have the major role in innate immunity

• produces cytokines, present immunogenic substances to other cells

• bridges innate immune response and adaptive response

when number of PRRs and cytokines reach a certain level the adaptive immune response is triggered

what bridges adaptive and innate immune response

Complement System C’

• composed of 9 soluble factors found in blood

• innate response- cell can be cleaved after binding to the cell walls of bacteria

• starts chain reaction leading to cleave of other complement factors

when the last 4 complement proteins generate a pore in the cell wall of the bacteria

when does total death occur in the complement system