Bacteriology and Oral Diseases; pptx 8

pathogenies and strep

Pathogenicity

The ability to cause disease

Virulence

The extent of pathogenicity

Attenuation

The decrease or loss of virulence; attenuated bacteria or virus can be made to be studied or for injections to expose to body

ID50

Infectious dose for 50% of the test population

LD50

Lethal dose (of a toxin) for 50% of the test population

Susceptibility

Lack of resistance to a disease

Resistance

Ability to ward off disease

Nonspecific resistance

Defenses against any pathogen; basically innate immune system

Specific resistance

Immunity, resistance to a specific pathogen; basically adaptive immune system

portals of entry for virulent organism

• Respiratory tract

• blood and vector-borne

• urogenital tract

• ocular surface

• gastrointestinal tract

• skin 

T/F if bacteria enter into any one of these portals of entry, they are guaranteed to infect the host

False, there are many mechanism in each portal of entry that can still block the bacteria 

First line of defense

• Intact skin

• mucous membranes and their secretions

  • they shed (coughing, etc) getting rid of bacteria

• normal microbiota

Second line of defense

• phagocytic white blood cells

• inflammation

• fever

• antimicrobial substances

Third line of defense

• specialized lymphocytes: B cells and T cells

• antibodies

what parts are non specialized? (first line of defense, second line of defense, Third line of defense)

first line of defense and second line of defense

what parts are specialized? (first line of defense, second line of defense, Third line of defense)

Third line of defense

what can this image show u?

this shows u the different mechanisms in different cavities that can block bacteria, etc

*good reference 

skin

epidermis consists of tightly packed cells with keratin (protective portein)

Mucous membranes

• ciliary escalator: microbes trapped in mucus are transported away form the lungs

• lacrimal apparatus: washes eye

• saliva: washes microbes off

• Urine: Flows out

• Vaginal sections: flows out

Chemical factors

• fungistatic fatty acid in sebum

• lysozyme in perspiration, tears, saliva, and tissue fluids

• low pH (1.2-3.0) of gastric juice

• transferrin’s in blood find iron

• Nitric oxide inhibits ATP production

Normal microbiota

Microbial antagonism/competitive exclusion: normal microbiota compete with pathogens

*this is really important in preventing disease, when bacteria are wiped of when taking antibiotics u become very susceptible to infection 

what are the characteristics that a pathogen needs?

• need to be able to be exposed to other organisms

• ability to adhere

• ability to invade 

• ability to colonize and grow

• either invasive or toxic

  • this results in tissue damage and/or disease

how can we see how a pathogen goes through the body

using bioluminescence(this emits a light that can be detected) or fluorescents(needs to shine a light directly). tagging the pathogen and seeing the light go through the body; IVIS

non-specific colonization mechanisms

does not require receptor (e.g capsule, EPS, things that can stick)

specific colonization mechanisms

requires receptors

Adhesions/ligands bind to receptors on host cells

good review for other bacteria’s and their specifics for binding

Host immune evasion

• ability to avoid phagocytosis

• intercellular growth

• production of proteases(enzymes in general) against antibodies

• biofilm and microbial cell clusters (such as in UTI’s)

  • some bacteria, this is the only virulence factor they have 

Enzymes produced by pathogens

pathogens produce a variety of enzymes that enhance virulence by breaking down or altering host tissue to provide access and nutrients 

*pic has examples of enzymes

Coagluase

coagulate blood

Kinases

Digest fibrin clots

hyaluronidase

hydrolyses hyaluronic acid

collagenase

hydrolyzes collagen

IgA proteases

destory IgA antibodies

siderophores

take iron from host, iron - bring proteins

antigenic variation

alter surface proteins; *not an enzyme

protease

breaks down proteins; can also sometimes use the pieces of the broken down protein as a food source

Toxin

Substances that contribute to pathogenicity

Toxigenicity

ability to produce a toxin

toxemia

presence of toxin the host’s blood

toxoid

Inactivated toxin used in a vaccine

Antitixon

antibodies against a specific toxin 

if you are infected to a bacteria that produces a toxin in your body what do physicians do?

they will give you an antibiotic for the bacteria and an antitoxin for the toxin the bacteria produced

Exotoxins

toxins that are produced and secreted form bacteria

• produced by living/growing cells

• the toxins are always proteins

• they do not cause fevers

• can be neutralized by antitoxins/antibodies

• have a small LD50

  • very toxic

what is the source of exotoxins in bacteria?

mostly gram +, but some gram - can also produce them

what are the different categories of exotoxins

• cytolytic toxins

• AB toxins

• Superantigen toxins 

cytolytic toxins

• secreted soluble toxins that damage host cells cytoplasmic membranes causing cell lysis, basically your homolosine

  • proteins that are secreted by bacteria

    • e.g type 1 secretion system

• will bind to the phospholipid of the host membrane (on slide)

• bind to membranes of mammalian cells(lipid) and puncture a hole in the cell causing it to lysis(Dr. Kadouri’s words)

  • this is done to scavenge the fe from the RBC

what is an example of a bacteria that produces a cytolytic toxins

aa or A. actinomycetemcomitans; they produce a leukotoxin, acts as a virulence factor as a means to protect itself from pnms/white blood cells

leukotoxins

cytolytic toxin that is produced and secreted by cytolytic toxin A. actinomycetemcomitans (aa) and is a protein that can bind to white blood cells ———- specifically to activated pnms (bind to lymphocyte function antigen - 1 (LFA-1) on the pnms which is what allows the pnms to go into tissues from blood)

• binds to LFA-1 and inserts into target cell membrane

• several LtxA monomers multimerize and form a pore or disruption in membrane

• pore/disruption causes leakage or membrane collapse

• at high doses LtxA = necrosis (holes in membrane); low doses = apoptosis

basically exotoxins that bind to and disrupt the membrane on cells, basically melting it

at high doses LtxA

causes necrosis (holes in membrane)

low doses of LtxA

causes apoptosis

what are pnms?

polymorphonuclear leukocytes; involved in:

• Phagocytosis: PMNs engulf and destroy pathogens, such as bacteria and viruses.

• Inflammation: They release chemicals that promote inflammation, attracting other immune cells to the site of infection.

• Tissue repair: PMNs help clean up debris and damaged cells, facilitating tissue healing.

• Maintaining homeostasis: PMNs help regulate the immune system and prevent excessive inflammation.

AB toxins

toxin that consists of 2 subunits, which work together to bind, infiltrate and inhibite protein synthesis

why are AB toxins called AB toxins?

because it conceits of 2 subunits, A and B

AB toxins - A

crosses the membrane thanks to the help of B and plays a role in inhibiting protein synthesis

AB toxins - B

binds to host cell surface receptor and facilitates the transfer of the A subunit across the membrane

what kind of toxins does diphtheriae secrete?

AB toxins

diphtheriae

gram + bacteria that usually causes infection on mucal membranes (usually in throat and sometimes in GI tract) and will be distributed throughout the body that can cause heart, liver kidney damage. death is causes by the actual toxin and can be treated using a antitoxin and antibiotic

there is a vaccine for it that most peopel have taken

what kind of a toxins are botulinum and tetanus toxins and what bacteria produces them?

Clostridium botulinum produces them and they are AB toxins

botulinum and tetanus toxins

• very potent neurotoxin, 1mg can kill >1 million guinea pigs (humans 2 nanograms per kg of bodyweight)

• the spreading of the toxin will cause paralysis leading to death

how does botulinum toxin work?

will bind to presynaptic membranes on motor neurons at neuromuscular junctions and block the release of acetylcholine, acetylcholine is responsible for muscle contractions and this can cause many issues like trouble breathing, etc. basically causes a paralysis

how is Botox done?

It is done by injecting toxins(usually botulinum toxin) into the muscle nerves which relaxes the muscles; wrinkles form due to muscle contractions in that area, if you relax the muscle they will go away 

what kind of issues can arise form incorrect use of botox?

too much can kill the nerve

wrong spot injected can have face paralysis 

tetanus toxins

AB exotoxin, neurotoxin; transported to neurons in the spinal cord to bind to ganglioside lipids which then blocks glycine release which is important for inhibition of neurotransmitters. This will lead to an over accumulation of acetylcholine which will lead to twitching paralysis and muscles which are constantly contracting; treated with antibiotics and antitoxins

what is the first sign of tetanus toxins?

locked jaw

Enterotoxins

exotoxins that specifically affect the small intestine, causing changes in intestinal permeability that lead to diarrhea and vomiting

can be caused by Gram + or - 

what causes food poisoning?

bacteria that grow in the GI tract or the toxins that bacteria produce (Enterotoxins)

T/F Enterotoxins are AB toxins

True

how do Enterotoxins work?

the b subunit binds to GM1 which are glycolipids on the membrane of intestinal epithelial cells this causes a chain to activate adenylate cyclase which is an enzymes what converts ATP to cAMP which regulators cell compounds involved in ion balance. When cAMP levels go up, chloride ions are secreted to the lumen and water follows it into the lumen resulting int massive amounts of fluid loss and sever diarrhea

1. messes with regulatory compounds for ion balance (increase in cAMP)

2. causes salts to leave the the blood instead of go into the blood

3. water flows the salt into the lumen of the small intestine (GI tract)

4. a lot of water loss

*a representation of what normally happens in lumen of intestines is shown in picture

Superantigen toxins

a toxin capable of over-activating the immune system which can cause toxic shock syndrome. These toxins directly bind to MHC-II and TCR and bridging them, which puts theses complexes in contact with each other for much longer than normal causing T cells to release a large number of cytokines. this cytokine storm is what causes toxic shock syndrome 

• overstimulate the immune system

• causes toxic shock

*25 superantigens known to date

endotoxins

• only produces by gram (-) bacteria; they are the LPS on gram (-) bacteria

• works very similarly to superantigens in that it over stimulates the immune system putting you in septic shock

• they are NOT secreted, they are on the surface of the cell, can still be present on dead cells and still stimulate an immune response 

• they are made of sugars, not proteins

• can cause fever and increase permeability of blood vessels, lowering bp

  • the lowering of bp will cause septic shock and the lower of bp basically causes organ failer 

• can also cause platelets to aggregate which can cause blood clots, which can lead to a stroke

looking at this picture of a LPS (endotoxin) what part(s) induces the toxic effect?

the lipid A portion (yellow)

looking at this picture of a LPS (endotoxin) what part(s) make the complex water soluble?

the o-specific polysaccharide and core polysaccharide (purple and red)

what part of the LPS stabilizes the molecule?

the core polysaccharide (red)

what part of the LPS does the body make antibodies against when u are vaccinated?

the o-specific polysaccharide (purple)

what is something that endotoxins/LPS do that exotoxins don’t and why?

produce a fever and this is because macrophages take in the bacteria and as a response to the LPS will produce cytokines (IL-1, Interleukin - 1 ) which will inducing the hypothalamus to produce prostaglandins, raising your temperature (fever)

T/F Endotoxins are proteins just like exotoxins

false, they are sugars

Limulus amebocyte lysate assay (LAL)

this assay is used to check to make sure no LPS is present when making drugs from bacteria, etc.

• amebocyte from horseshoe crab are used to detect endotoxins

• presence of endotoxins cause aggregation and lysis of amebocyte to extract a precipitating gal

  • can detect as little as 10pg/ml lps

chart comparing endo- and exo- toxins 

REVIEW, REVIEW, REVIEW

salmonella virulence factors (said u don’t have remember this? 0:41:42, last lecture video with kadouri)

has many virulence factors

• causes food poisoning 

• have siderophores

• produce enterotoxins

• LPS

• capsule

• pili and fimbria

• virulence plasmid, allowing for resistance or changing or gene expression

phylogeny of Gram + bacteria

• low G+C

• High G+C

level of G and C in DNA

low G+C gram positive bacteria

• mycoplasma

• bacillus

• staphylococcus

• streptococcus

• Lactococcus

• enterococcus

• lactobacillus

• clostridium

high G+C gram positive bacteria

• mycobacterium

• streptomyces

Viridians streptococci

• streptococcus

• Lactococcus

• enterococcus

• lactobacillus

all produce acid and associated with caries

staphylococcus bacteria

(mainly staph aureus), these are the bacteria that cause the most infections in humans out of all other G+ bacteria, kills thousands of people all the time because of how many virulence factors these bacteria have 

rounds cells that are clustered together 

• staph - cluster together

• coccus/cocci - round cells

• G +

• 0.5-1.5 um

• nonmotile (nonflagilated)

• factitively anaerobic

  • can be found causing infection in many different parts of the body

• can grow in high salt (10% NaCl)

• 18 - 40 degrees C

  • explains why they can cause a lot of food poisoning 

• part of the normal flora (nasal, skin)

  • bc can grow in higher salt areas

what the are 2 most important staphylococcus bacteria for humans in infection and where do they grow

• staphylococcus epidermidis

  • skin

• staphylococcus aureus

  • nose

staphylococcus epidermidis virulence factors

does not have a lot of virulence factors and it mainly only has the ability to:

• poly-N-acetylglucosamine

  • allows for attachment to biomaterials

  • biofilm formation

  • protection from antimicrobial killing

  • protection form phagocytosis 

• make a very thick EPS/biofilm

• most infections are device related

was always considered a commensal bacteria(not pathogenetic) but when started to use more medical devices can be accidentally injected into body making it a pathogen 

staphylococcus epidermidis can cause what kinds of infections?

• cause infections in device infections

• cause bacteremia

staphylococcus aureus can cause what kinds of infections?

• skin infections

• Device infections

• infections in people that have Burn and wound

• pneumonia - lung infection

• urinary tract infections

• bacteriemia

• necrotizing fasciitis - produce proteolytic enzyme (breaks down tissue)

• meningitis - brain infection

• Osteomyelitis - bone infection 

• endocarditis

• sepsis

• food poisoning

• toxic shock syndrome

staphylococcus aureus virulence factors allow it to do what?

• survival in many different environment

• invasion and attachment

  • surface/cell/tissue attachment

• avoiding the immune system and immune detection

  • avoiding opsonization

  • avoiding phagocytosis

  • cell invasion

• produce toxins

• produce enzymes 

staphylococcus aureus virulence factors ( there a SOOOOOO MANY)

• can be transferred from touch 

• can survive in many different environments

• produce a capsule (all do)

  • avoid immune system

  • bind to tissue

• ability to produce a slime layer

  • good for forming a biofilm

• very thick peptidoglycan

  • more resistant to desiccation and stresses

  • 50% peptidoglycan in weight

  • in MRSA mecA codes for PBP2 that doesn’t bind penicillin

    • another penicillin binding protein

  • can help prevent antibiotics and other mechanisms from entering 

• has huge amount of proteins on surface allowing for the binding on almost anything on body

  • Teichoic acid

    • run through entire peptidoglycan

  • MSCRAMMS

    • microbial surface components recognizing adhesive matrix molecules

  • laminin binding protein

  • fibronectin binding protein

  • collagen binding protein

  • elastin binding protein

• has peptidoglycan associated protein

  • protein A - mechanism to avoid immune system

    • coats the surface of S. Aurus

    • very high affinity for binding the Fc receptor of IgG

      • v structure binds to bacterial surface on the opposite configuration, making the antibody nonfunctional

    • can prevent opsonization and phagocytosis

    • can inhibit antibody mediated clearance 

  • coagulase - forms blood clots around the bacteria, protecting it 

    • cell bound clumping factor - surface protein on S. aureus

    • cell free coagulase

    • converts fibrinogen to insoluble fibrine, which causes clumping and aggregation

    • coagulase - can cause the formation of a protective fibrin layer around the cell 

• Extracellular enzymes (these allow for breaking down of tissue)

  • staphylokinase- dissolves fibrin clots

    • not all staph have this

  • hyaluronidase - hydrolyzes hyaluronic acid in connective tissue

  • lipase - hydrolyzes lipids

  • deoxyribonuclease - hydrolyzes DNA

  • Fatty acid modifying enzyme (FAME)

• a lot of different exotoxins (4 different hemolysins it can produce)(toxins that puncture membranes)

  • α toxin (α hemolysin)

    • produced by most S. aureus strains

    • toxic to many cells

    • forms pores in cell membrane and causes tissue damage

  • β toxin

    • produced by most S. aureus strains

    • hydrolysis of membranes

  • δ toxin

    • produced by all S. aureus strains

    • nonspecific membrane toxin 

  • γ toxin

    • produced by most S. aureus strains

    • lyse neutrophils and macrophages 

• additional exotoxins (not hemolysins)

  • Exfoliating toxin - protease (break down tissue)

    • serine protease that can degrade structural component of the epidermis

    • staphylococcal scalded skin syndrome (SSSS)

      • can grow deep in skin and this can happen

      • secondary infection can form after or during

  • enterotoxins - major water loss

    • associated with food poisoning

    • heat stable - 10 degree C 30 min

    • resistant to gastric enzymes

    • causes inflammation of the gastric tissue, diarrhea and vomiting 

  • TSST-1

    • toxic shock syndrome toxin -1

      • superantigens, which bind to macrophages and interact with T-cells and results in the release of cytokines-shock and high fever and organ failure 

        • reason for changing of tampons 

what is this picture showing?

it is a summary of the virulence factors of staphylococcus aureus without the specific details

how to test for S. aureus?

coagulase identification test, taking the bacteria samples on slide, mixed with rabbit plasma/serum, then put into tube. If S. aurus will produce coagulase making a blood clot like gel at the bottom of the tube

if you are testing a bacteria and it is catalase positive and coagulase positive, what bacteria is it?

S. aureus; the catalase positive tells you it a staphylococcus bacteria and coagulase positive is a trait of aureus bacteria giving you that conclusion 

what staphylococcus aureus strains are the worst

• HA-MRSA (hospital acquired) (methicillin resistant staph aureus)

  • can usually be acquired in hospital settings

  • typically found in immunodeficient patients

  • need to use gentamicin for treatment

    • IV

• CA-MRSA

  • Community acquired

    • can be found almost anywhere

  • typically found in healthy individuals

looks like a spider bite on skin

how can u tell the difference between streptococcus and staphylococcus?

by performing catalase test, putting both bacteria on a glass and putting hydrogen peroxide on top, if the sample begins to fizzle and get bubble means it produces catalase and is able to break down hydrogen peroxide, this makes it the staphylococcus bacteria

S. Mutans virulance factors

• transmitted from main care giver

• adherence to tooth surface

  • Antigen I/II - binding to acquired salivary pellicle on tooth surface

  • GBP - make glucans

  • GTF - coaggregate and auto aggregate binding with the glucans

• production of extracellular polysaccharide

• acidogenesis

• aciduricity 

After step mutans make acidogenic or cariogenic plaque (low pH plaque) what other bacteria come and attach?

• Streptococcus sanguis

• lactobacilli

• Lactococcus

• taracoccus

these can make the situation worse as all of these bacteria produce and like to live in acidic environments

what bacteria can form GTF(glucosyltransferase)

• streptococcus

• Lactococcus

• lactobacillus

what biological properties of saliva influence the caries process?

1. mechanical washing

   1. removes debris of food so bacteria cant ferment it and wash away the bacteria

2. buffering

   1. buffers the pH, raising the pH, decrease the time of low pH

3. antibacterial activity

   1. lysozyme

   2. lactoferrin 

4. aggregation of bacteria

   1. IgA

5. remineralization of enamel

   1. salts (calcium and phosphate)

      1. allowing for recalcification of lesions like white spots 

conditions/mechanism associated with mechanical washing in saliva

• flow rate

  • different flow rates in different parts of oral cavity

  • due to gravity 

• xerostomia

  • condition with no saliva flow

  • takes away the benefits of the saliva

    • people that take medication

      • alpha blockers

      • methamphetamines

• circadian rhythm

  • low saliva flow at night compared to day

    • reason for bad breath and dry mouth

    • gives bacteria a good time to ferment if any food is still present and you don’t brush