Microbiology Lecture - Chapter 15 Micorbial mechanisms of pathogenicity
Virulence is ____________.
The degree of pathogenicity - better or worse of being a pathogen.
Pathogenicity is _______________.
ability to cause to disease
Virulence depends on many factors such as _________.
Type of organism
How bad the infection is
Virulence factors- age, environment, temp, diet, nutrients
is it healthy
age, temp etc
How do microorganisms can entry into host?
portals of entry
What are portals of entry?
1. Skin- largest organ of the body, best physical barrier ( some organisms can penetrate the skin hookworms and fungi)
2. Gastrointestinal tract- (2)
3. Respiratory tract (1)
4. Genitourinary tract (3)
5. Parenteral route- bypassing the skin barrier through openings in the skin
The virulence of a microbe is often expressed in ______ and ________.
ID 50-infectious dose for 50% of a sample population
LD 50-lethal dose the amount required to cause death in 50% of a sample population
Adhesion is required to __________.
Gain entry into a host
majority have adhesins
microbes have adhesins on their cell surface
-specific for receptors on host cells
-made of proteins, lipoproteins or glycoproteins
Host cell receptor typically sugars
capsules-strategy to attach to system
resistant to antibiotics -impenetrable
food when food is scarce
M protein-streptococcus pyagenes- help microbes attach to endothelial cells and they are on cell surface and fimbriae
mycolic acids- waxy impenetrable- allows microbes to resist phagocytosis (microbacterium-TB)
Exoenzymes- coagulases- forms a clot around bacterium to evade phagocytosis- protects itself from immune cells
Kineses-enzyme that dissolves clot and allows them to travel to another part of the body
Hyaluronideses-break down polysaccharide that holds cells together
Collagenese- breaks down collagen- intermediate tissue
IgA protenase- breaks down antibodies of host
Antigenic variation is ______________.
Allows the microbes to change the adhesins it carries on its cell surfaces
quick change artist
some microbes have several genes that codes for adhesins
can change their exterior so immune system can't detect it
The 2 major types of toxins are _____________.
Endotoxins and exotoxins
minute amounts extremely lethal
most are enzymes
numerous deleterious effects
at times toxins cause disease not bacteria
Bacteria causes ____________ and toxins cause _______________ .
infection and intoxication
Three major types of toxins:
1. A-B toxins disrupt protein synthesis
2. superantigens- stimulate large amount of immune response cells - causing toxic shock
3. Membrane disrupting toxins
form protein channels - lysis of host cells
dissolve membrane lipids
Endotoxins are gram _________.
affects temp controlling region of your brain reset to higher temperature is fever
The toxic component found on outer membrane of gram (-) cell
only when gram (-)cell lysis are they a problem because they release lipid A and lipid A is the toxic component of gram (-) cells