UNIT 8: HOST MICROORGANISM INTERACTION Flashcards
o Growth and multiplication of microorganisms that cause damage to the host
o Bodily invasion of pathogenic microorganisms that reproduce, multiply, and then cause disease through local injury, toxin secretion, or An-Ab reaction to the host
Infection
caused by microorganisms from the microbiota of the host
Autogenous infection
result of medical treatment or procedure
iatrogenic infection
affects immunocompromised host
Opportunistic infection
hospital-acquired infection
nosocomial infection
4 common types of nosocomial infection
-UTI
-Lung infection (Pneumonia)
-Surgical site infection
-Bloodstream infection
disease that occurs occasionally
sporadic
it is when a disease is constantly present at some rate of occurrence in a particular location
endemic
a larger than normal number of diseased or infected individuals in a particular location
epidemic
a larger than normal number of diseased or infected individuals that occurs over a relatively short period
outbreak
an epidemic that spans the world
pandemic
a person who carries the etiologic agent but shows no apparent signs or symptoms of infection or disease
carrier
harbors the microorganism temporarily for a few days or weeks
casual / acute / transient carrier
remain infected for a relatively long time, throughout its entire life (Typhoid Bacillus)
chronic carrier
remain infected for a relatively long time, throughout its entire life (Typhoid Bacillus)
chronic carrier
recovered from infection but continuous to harbor larger numbers of the pathogen
convalescent carrier
overt clinical case of the disease
active carrier
what are phases of infectious diseases?
Incubation Period
Prodromal Period
Clinical or Illness Period
Decline Period
Convalescence Period or Period of Recovery
time between the exposure to a pathogenic organism and the onset of symptoms
incubation period
a phase where there is appearance of signs and symptoms
Prodromal Period
a phase where there is peak of characteristic signs and symptoms
Clinical or Illness Period
phase where signs and symptoms begin to subside as the host’s condition improves
Decline Period
phase wherein the host is recuperating towards full recovery
Convalescence Period or Period of Recovery
A microorganism responsible for causing infection or infectious disease
Causative / Etiologic Agent
Organism capable of producing disease
Pathogen
A quantitative measure of the degree of pathogenicity of a particular microorganism
Virulence
Microorganism that does not cause disease; may be part of the normal flora
Nonpathogenic
An agent capable of causing disease only when the host’s resistance is impaired
Opportunistic pathogen
examples of opportunistic pathogen
-PAE
- Stenotrophomonas maltophilia
Means by which etiologic agents are brought in contact with the human host
mode of transmission
A non-living entity that is contaminated with the etiologic agent and as such is the mode of transmission for that agent
Vehicle / Fomite
A living entity (animal, insect, or plant) that transmits the etiologic agent
Vector
An animal or plant that harbors or nourishes another organism
Host
An organism which is dependent on another organism for food and shelter
Parasite
any type of epidemiologic investigation that involves data collection for characterizing circumstances surrounding the incidence or prevalence of a particular disease or infection
Surveillance
The state of disease and its associated effects on the host
morbidity
Death resulting from disease
mortality
Laboratory-based characterization of etiologic agents designed to establish their relatedness to one another during a particular outbreak or epidemic
Strain typing
Origin of the etiologic agent or location from which they disseminate
Reservoir
The etiologic agent responsible for an epidemic or outbreak originates from a single source or reservoir
Common source
association of two organisms living in close proximity
Symbiosis
refers to a mutually beneficial relationship between two species
mutualism
a relationship wherein the parasite derives benefits from the host without causing injury or harm to the host
commensalism
a relationship whereby one organism derives benefits at the expense of another
parasitism
ability of the organism to produce disease
pathogenicity
large groups of genes that are associated with pathogenicity and are located on the
bacterial chromosome
pathogenicity islands
the ability of the organism to enter host tissues , multiply, and spread faster
invasiveness
ability of the organism to produce toxins
toxigenity
non-poisonous forms of toxins which can be
used for vaccination
toxoid
preparation of toxoid
- by aging
- by exposure to heat
- by exposure to 50% alcohol, formaldehyde, and dilute acids
general stages of microbial-host interaction
- physical encounter between host and microorganism
- microorganism colonization of host surface(s)
- microorganism entry, invasion, and dissemination
- outcome
microorganisms that are commonly found on or in body sites of healthy persons
normal / indigenous / usual flora
microorganisms that colonize an area for months or years
resident microbial flora
microorganisms that are present at a site temporarily represent
transient flora
presence of flora depends on what factors?
- physiologic factors or temperature
- moisture
- presence of certain nutrients and inhibitory substances
roles of microbial flora?
- provide a first line of defense against microbial pathogens
- assists in digestion and absorption of nutrients; also synthesis of Vitamin K
- play a role in toxin degradation
- contribute to maturation of the immune system
ability of a microbe to produce disease in a susceptible individual
pathogenicity
are organisms recognized to cause disease in healthy immunocompetent individuals
true pathogens
examples of true pathogens?
Yersinia pestis
Bacillus anthracis
cause disease if the host is immunocompromised
opportunistic pathogens
o relative ability of a microorganism to cause disease or the degree of pathogenicity
o measured by the numbers of microorganisms necessary to cause infection in the host
virulence
Microbial Virulence Factors
a. Inhibiting phagocytosis
b. Facilitating adhesion to host cells or tissues
c. Enhancing intracellular survival after phagocytosis
d. Damaging tissue through the production of toxins and extracellular enzymes
o Mask the cell surface structures that are recognized by receptors on the surface of the phagocytic cell
o Inhibits the activation of complement by masking structures to which complement proteins bind
capsule
o found in the cell wall of Staphylococcus aureus
o Interfering with the binding of the host’s antibodies to the surface of the organism
o Binds to the Fc portion of IgG preventing opsonization and phagocytosis by turning the antibody around on the surface
Protein A
heat resistant and acid resistant protein, mediates attachment to host epithelial cell and helps resist phagocytosis
M protein
resists digestion during phagocytosis; the bacteria can even multiply inside macrophages
Mycolic acid
o produced by Streptococci
o lyse red blood cells and induce toxic effects on WBC
hemolysins
o realesed by pathogenic staphylococci
o cause lysosomal discharge into cell cytoplasm
leukocidins
- Staphylococcal leukocidin
- Lethal to leukocytes and contributes to the
invasiveness of the organism
Panton-Valentine
Cell surface structures that mediate attachment
adhesins
enable bacteria to adhere to host cell
surfaces, offering resistance by attachment to target cells and
increasing the organism’s colonizing ability
fimbriae (pili)
what are the main adhesins in bacteria?
-fimbriae (pili)
-surface polysaccharides
Use lactoferrin as a source of iron
meningococci
organisms that produce an IgA protease that
degrades the IgA found at mucosal
surfaces
H. influenzae,
N. gonorrhoeae, and
N. meningitides
Circumvent host antibodies by
shifting key cell surface antigens
Borrelia spp.
microorganisms able to multiply intracellularly
Chlamydia, Mycobacterium,
Brucella, and Listeria
ability of microorganism to penetrate and grow in tissues
invasion
ability of disease or organisms to spread to distant sites
dissemination
a highly invasive organism that
may not disseminate
Clostridium perfringens
poisonous substances produced by organisms that interact with host cells, disrupting normal metabolism and causing harm
Toxins
soluble substances that liquefy the hyaluronic acid of the connective tissue matrix, helping to spread bacteria in tissues, promoting the dissemination of infection
Proteases and Hyaluronidases
breaks down collagen, which
forms the connective tissue of
muscles and other body organs
and tissues
collagenase
hydrolyzes hyaluronic acid, a type
of polysaccharide that holds
together certain cells of the body,
particularly cells of the connective
tissue helping the organism spread
from its initial site of infection
hyaluronidase
example of organisms in hyaluronidase
Streptococcus pyogenes (cellulitis)
Clostridium perfringens (gas gangrene)
produced by S. aureus and
accelerates the conversion of
fibrinogen to a fibrin clot
coagulase
Destroy IgA antibodies found on
secretions
immunoglobulin A protease
Destroy neutrophilic leukocytes and macrophages
Leukocidin
2 subunits of exotoxin?
- nontoxic (binds the toxin to the host cells)
- toxic
T or F
exotoxins are produced by both gram-negative and gram-positive bacteria
T
- Encoded by phages, plasmids, or transposons→most toxic
substances - Good antigens and induce the production of antibodies
called “ANTITOXINS”
toxin gene
when exotoxin polypeptides are treated with formaldehyde (or acid or heat), these endotoxin polypeptides can be converted to what?
toxoids (which are used in protective vaccines)
examples of toxoids include:
- Diphtheria toxin
- Tetanospamin
- Botulism toxin
- Heat labile enterotoxin by E. coli, Vibrio, and Bacillus
- Verotoxin
- Erythrogenic toxin
- Tree toxins of B. anthracis (ef, pa, lf)
- Toxic shock syndrom toxin 1 (TSST-1)
transcribe ef, pa, lf
- edema factor
- protective antigen
- lethal factor
3 principal types of exotoxin on the basis of structure and function?
- A-B toxin
- Membrane-Disrupting Toxin
- Supernantigen
Consists of two domains or subunits, one responsible for binding to the cell and entry into the cell and the other
possessing the toxic activity
A-B toxin
cause lysis of host cells by disrupting their plasma membrane; some form protein channels in the plasma membrane (S. aureus); others disrupt the phospholipid portion of the membrane (C. perfringens)
Membrane-Disrupting toxins
Example of Membrane-Disrupting toxins?
- Leukocidins
- Hemolysins
antigens that provoke a very intense immune response; non-specifically stimulate the proliferation of immune
cells called T cells, which in turn secrete enormous amounts of cytokines
Superantigens
inhibits protein synthesis and
affects the heart, nerve tissue, and liver
diphtheria toxin
neurotoxin that blocks nerve
impulse transmission, causing flaccid paralysis, especially in infants → FLOPPY BABY
botulinum toxin
produce “EXFOLIATIN” which causes rash and massive skin peeling or exfoliation
Streptococcus pyogenes and Staphylococcus aureus
give 3 examples of superantigens?
- Diphtheria toxin
- Botulinum toxin
- Streptococcus pyogenes and Staphylococcus aureus
Neurotoxin; prevents the transmission of nerve impulses ➡️ flaccid paralysis
Clostridium botulinum - botulism
Neurotoxin, blocks nerve impulses to muscle relaxation pathway ➡️ spastic paralysis
Clostridium tetani - tetanus
Cytotoxin, inhibits protein synthesis (esp. in nerve, heart, and kidney cells)
Corynebacterium diphtheriae - Diphtheria
Causes skin layers to separate and slough off (scalded skin)
Staphylococcus aureus - scalded skin syndrome
Enterotoxin, causes secretion of large amounts of fluids and electrolytes that result in diarrhea
Vibrio cholerae - cholera
bacterium associated with traveler’s diarrhea?
- Enterotoxigenic E. coli (ETEC)
- Shigella spp.
composed of the LPS portion of the outer membrane on the cell wall of gram-negative bacteria
endotoxins
role of endotoxins?
- stimulate the fever centers of the hypothalamus (1hr after exposure)
- hypotension (30 mins after exposure) ➡️ shock
- initiates coagulation ➡️ DIC (Disseminated Intravascular Coagulation)
- severe neutropenia
- activate macrophage, complement, and has adjuvant effect on protein antigens
- stimulates interferon production and causes changes in carbohydrates, lipids, iron, and sensitivity to epinephrine
microorganisms that are capable of penetrating normal, healthy skin
Leptospira spp.
Francisella tularensis
Treponema spp.
primary mechanical barrier to infection
healthy, intact skin
o low-molecular-weight (approximately 20,000 D) enzyme
that hydrolyzes the peptidoglycan layer of bacterial cell walls
o found in serum, tissue fluids, tears, breast milk, saliva, and sweat
lysozyme
- found in mucous secretions of the respiratory, genital, and digestive tracts
- serve as opsonins, fix complement and neutralize the infecting organism
secretory IgA
- low-molecular-weight cationic proteins in serum
- lethal against gram-positive bacteria and are released from platelets during coagula.on
ß-lysins
inhibits proliferation of viruses
interferon
compete with pathogens for nutrients and space
indigenous microbial flora
substances that inhibit the growth of closely related bacteria
bacteriocins
Particle is taken into the cytoplasm and enclosed within a vacuole called
phagosome
Phagosome fuses with lysosomes = ?
phagolysosome
Lysosomes release their contents into the phagosome → ?
degranulation
myeloperoxidase, proteases, cathepsin, lactoferrin,
lysozyme, and elastase ➡️ necessary for the killing and digestion of the engulfed particles
lysosomes
CARDINAL SIGNS OF INFLAMMATION:
redness
swelling
heat
pain
loss of function
CHEMICAL MEDIATORS OF INFLAMMATION
histamine
kinins
leukotrienes
prostaglandins
acute phase reactants
cytokines
mechanism whereby the body is able to protect itself from invasion by disease-causing organisms
immunity
consists of numerous cells and protein molecules that are responsible for recognizing and removing these foreign substances
immune system
constituents of the adaptive or specific immune response
lymphocytes and antibodies
primary effector cell in
cell-mediated immunity
t lymphocytes
microorganism mot is thru dog-bite and cat-bite infec.ons
Pasteurella multocida
Inhibits transpeptidation and cell wall synthesis
beta lactam
Inhibits translocation and elongation of peptidoglycan layer
vancomycin
Inhibits synthesis of peptidoglycan precursors
bacitracin
Acts only on growing cells and can either be a bactericidal or bacteriostatic
isoniazid
