-
An organisms ability to cause a disease is called it’s
pathogenicity.
-
The degree of pathogenicity is called it’s
virulence.
-
In order for a microorganism to cause disease it must:
- Gain access to the host
- Adhere to the host tissues
- Penetrate or evade the hosts defenses
- Damage tissues and cause disease
-
The way in which a pathogen gains entrance to a host is called its
portal of entry.
-
portal of entry are :
- Mucus Membranes:Respiratory tract,GI tract,Genitourinary tract,Conjunctiva
- Skin:Parenteral route
-
Many organisms have a preferred portal of entry which is a prerequisite to a ___
disease
-
Preferred Portal of Entry - Salmonella typhi
- digestive system (disease )
- skin (no disease)
-
Preferred Portal of Entry - Streptococcus
- respiratory system (disease)
- Digestive system (no disease)
-
Preferred Portal of Entry - Bacillus anthracis
more than one
-
How virulent a microbe is expressed in terms of its ___
LD50 : number of microbes in a dose which will kill 50% of test animals injected
-
The dose required to produce a demonstrable infection is indicated by ___
ID50
-
LD50 & ID50 are used to ___
compare virulence of organisms to each other
-
Portal of entry - Bacillus anthracis ID50
- Skin : 10-50 Endospores
- Inhalation : 10,000-20,000 Endospores
- Ingestion : 250,000-1,000,000 Endospores
-
Which organisms is the most virulent?
The lower the LD50 the more virulent the organism or toxin is.
-
Most pathogenic bacteria cause disease by penetrating tissues not by
simply attaching to them
-
Several factors that contribute to an organisms ability to invade a tissue :
- Capsules
- Cell wall components
- Enzymes
-
M protein resists phagocytosis eg ___
Streptococcus pyogenes
-
Opa protein inhibits T helper cells eg ___
Neisseria gonorrhoeae
-
Mycolic acid (waxy lipid) resists digestion eg ___
Mycobacterium tuberculosis
-
Organism which Prevent phagocytosis
- Streptococcus pneumoniae
- Haemophilus influenzae
- Bacillus anthracis
-
___ Coagulates fibrinogen
Coagulase
-
___ Digest fibrin clots
Kinases
-
___ Hydrolyzes hyaluronic acid
Hyaluronidase
-
___ Hydrolyzes collagen
Collagenase
-
___ Destroy IgA antibodies
IgA proteases
-
If a pathogen overcomes a hosts defenses it can damage tissues in four basic ways :
- 1 Direct Damage
- 2 Production of Toxins
- 3 Induction of hypersensitivity reactions
- 4 Using the hosts nutrients
-
To obtain free iron some pathogen secretes proteins called ___
siderophores
-
___ are poisonous substances produced by certain microorganisms
Toxins
-
The capacity of an organism to produce a toxin is called its ___
Toxigenicity.
-
___ is a condition of toxins in the blood
Toxemia
-
___ is inactivated toxin used in a vaccine
Toxoid
-
___ Antibodies against a specific toxin
Antitoxin
-
There are two types of toxins ___ & ___
-
Source of exotoxin is ___
Mostly Gram +
-
Exotoxin is the byproduct of ___
growing cells
-
Exotoxin is made up of ___
Protein
-
Exotoxin causes fever y/n ?
No
-
Exotoxin is nutralized by antitoxin y/n ?
yes
-
-
Main 6 Exotoxin representative
- 1 Diphtheria toxin
- 2 Erythogenic Toxin
- 3 Botulinum toxin
- 4 Tetanus toxin
- 5 Vibrio enterotoxins
- 6 Staphylococcal enterotoxins
-
Source of Endotoxins
Gram -tive
-
Endotoxins' relation to microbes
outer membrane
-
Endotoxins chemistry
Lipid A
-
Endotoxins causes fever y/n?
yes
-
Endotoxins is nutralized by Antitoxin y/n?
No
-
LD50 of Endotoxins
Relatively Large
-
___ are small circular pieces of DNA separate from the main chromosome which are capable of independent replication.
Plasmids
-
___ Can be transferred between organisms
- Resistance factors
- Virulence factors
-
___ are bacteria viruses
Bacteriophages
-
Bacteriophages can incorporate their DNA into the host-Lysogeny by ___
Lysogenic conversion
-
Viruses avoid a hosts immune response by ___
- 1 They grow inside cells
- 2 Specialized attachment
- 3 Some attack the immune system itself
-
___ visible effects of viral infection
Cytopathic effects
-
Those that result in cell death are called ___ effects
cytocydal
-
Those that damage the cell but do not kill it are called ___ effects
non-cytocydal
|
|