Lecture 16 Host Microbe Interactions Flashcards
Symbiosis
Living together
Mutualism
Both partners benefit
What kind of symbiosis is this:
In large intestine, some bacteria synthesize vitamin K and B which host can absorb, bacteria are supplied with warmth, energy source
Mutualism
Commensalism
One partner benefits, other is UNHARMED
Parasitism
One organism benefits, other is HARMED
microbiome is different after what births?
Vaginal birth, caesarian birth
Dysbiosis
Imbalance in microbiome
Dysbiosis can be _____ induced
Antibiotic
Main benefit of microbiome
Protection against pathogens
When microbiome is suppressed (during antibiotics), pathogens may _____, cause disease
Colonize
Antibodies against normal microbiota may also bind to _____
Pathogens
Colonization
Microbe establishing itself and multiplying
Infection
Colonization of pathogen
Infection can be _____ or _____
Subclinical, infectious disease
Subclinical
No symptoms or mild symptoms
Infectious disease
Prevents normal function, damages host
Difference between infection and disease
Infection: First step, occurs when pathogen enters body and begins to multiply
Disease: cells in body are damaged as a result of infection, symptoms appear
_____ are subjective effects experienced by patient
Symptoms
_____ are objective evidence that can be observed/measured
Signs
Initial infection is called _____
Primary infection
Damage can predispose individual to developing a _____ infection
Secondary
Pathogenicity
Ability of pathogen to cause disease
Primary pathogen
Microbe that causes disease in otherwise healthy individual
Opportunistic pathogen
Microbe causes disease only when immune system is compromised
Virulence
Degree of pathogenicity
Virulence factors
Substances that allow microorganism to cause disease
Communicable disease
easily spread from one host to another
infectious dose
number of microbes necessary to establish infection
What does ID 50 mean?
Number of cells required to infect 50% of test animals
Incubation period
Time between infection and onset
Illness
Signs and symptoms of disease are prevalent
Prodomal
Vague symptoms
Convalescence
Recuperation, recovery from disease
Acute infections
Symptoms develop quickly, last a short time
What type of infection is strep throat
Acute infection
Chronic infection
Develop slowly, last for months or years
Latent infections
never completely eliminated, microbe exists in host tissues without causing symptoms
Chickenpox and tuberculosis are what type of infection
Latent infections
Staphylococcus is what type of infection
Localized
Systemic infection
Agent spread throughout body
Bacteremia
Bacteria circulating in blood
_____ leads to sepsis
Bacterermia
Toxemia
Toxins circulating in blood
Viremia
Viruses circulating in blood
Koch’s postulates
Microorganism must be present in every case of disease
organism must be grown in pure culture from diseased host
Same disease must be produced when pure culture is introduced into susceptible hosts
organisms must be recovered from experimentally infected host
Limits of koch’s postulates
Some organisms can’t be grown in laboratory medium
infected individuals do not always have symptoms
Suitable animal hosts not always available for testing
humans may be only affected host species
Molecular koch’s postulate
modern day version that takes into account limitations
Virulance factor gene is identified
mutating gene in vitro to disrupt function should reduce virulence
reversion or replacement of gene should restore virulence
can test on an appropriate animal model of infection
Pathogens and hosts generally evolve towards _____
Balanced pathogenicity
Balanced pathogenicity
Pathogen becomes less virulent while host becomes less susceptible
Adherence
Adhesions attach to host cell receptor
Adhesions are located where
Tips of fimbrae
What is the binding of adhesions
Highly specific
What happens after adhesion
Colonization and establishment of disease
colonization and establishment of disease
microbe may produce _____ to bind iron
competes with _____, _____ of host
Siderophores
lactoferrin, transferrin
colonization and establishment of disease
Microbe must avoid _______
rapid pili turnover, antigenic variation _______
secretory IgA
IgA protease
Establishing an infection steps
Adherence
Colonization
Immune avoidance
Damage to host
Exit and infect new host
delivering effector proteins to host cells
secretion systems in some gram _______
Gram negatives
Delivering effector proteins in host cells
What type of secretion system
Type III
effector proteins induce changes in _______
Cytoskeleton structure
Pathogen induces _______ cells to engulf them via endocytosis
Non phagocytic
Actin molecules in host cells rearrange, causing _______
membrane ruffling
What is the entry point for most pathogens
Mucous membrane
What process happens in mucous membranes
Exploiting antigen sampling processes
in EASP, _______ samples material
MALT
hiding within a host cell allows what?
avoidance of complement proteins, phagocytes, antibodies
shigella directs transfer from intestinal epithelial cell to adjacent cells by causing host cell _______
actin polymerization
What prevents encounters with phagocytes?
C5a peptidase
What does C5a peptidase do?
degrades chemoattractant C5a
What does membrane damaging toxins do?
kill phagocytes, other cells
s. pyogenes makes _______
Streptolysin O
Avoiding recognition and attachment
capsules interfere with _______, some bind host’s regulatory proteins that inactivate _______
Opsonization, C3b
M protein
Cell wall of S. pyogenes that binds regulatory protein that prevents C3b inactivation
Fc receptors
bind Fc region of antibodies, interfering with their function as opsonins
What bacteria makes Fc receptors
S. Aureus
Surviving within phagocytes allows pathogens to
Avoid antibodies, control immune responses, move throughout body
escape from phagosome is prior to
lysis with lysosome
Escape from phagosome:
Some pathogens escape phagosome before it fuses with lysosomes. The bacteria then multiple within cytoplasm and
Preventing phagosome-lysosome fusion:
avoid destruction
Survive within phagolysosome
Few can survive destructive environment in phagolysosome
serum resistant bacteria: organism binds complement regulatory proteins to avoid _______
MAC
Avoiding recognition by antibodies
_______ cleaves IgA
found in mucus, secretions
IgA protease
Antigenic variation
Alter structure of surface antigens, stays ahead of antibody production
Mimicking host molecules
Cover surface with molecules similar to those found in host cell, appear to be “self”
Direct effects
Toxins produced
Indirect effects
Immune response
Damage may help pathogen to_______
Exit and spread
Exotoxins
Proteins with specific damaging effects
Exotoxins are secreted into tissue following _______
Bacterial lysis
Most exotoxins destroyed by
Heating
Toxoids
Inactived toxins
Antitoxin
Suspension of neutralizing antibodies
Neurotoxins
effect nervous system
Enterotoxins
Cause intestinal disturbance
cytotoxins
Damage variety of cell types
A-B toxins
A subunit is toxic/active
B subunit binds to target cell
What subunit determines cell type to be infected?
B subunit
Membrane damaging toxins
Cytotoxins that disrupt eukaryotic cytoplasmic membranes, lyse cells
Pore-forming toxins
insert into membranes, form pores
What is a pore forming toxin
Streptolysin O from streptococcus pyogenes
Phospholipases
Hydrolyze phospholipids of membrane
What is a phospholipase
A-toxin of clostridium perfingens
Superantigens
Stimulate high number of Th cells, causing Cytokine stork
Superantigens simultaneous bind _____ and _____-
MHC class II and T cell receptor
Toxic effect is from ______
massive cytokine release
Many antigens undergo ______ after superantigens, thereby suppresing the immune system
apoptosis
Endotoxin is a ______ found in outer membrane of gram ______ cell wall
LPS, negative
______ triggers inflammatory response
lipid A
When lipid A is systemic, causes widespread response, ______
Septic shock
______ is heat stable
Lipid A
______ detects endotoxin
Limulus amoebocyte lysate
Exotoxins from both gram negatives and positives are ______
potent, heat inactivated
Endotoxins from gram negatives are ______
heat stable
