Microbiology Chapter 15

what is the pathway for microbial mechanisms of pathogenicity

portals of entry

penetration/ evasion of host defenses

damage to host cells

portals of exit

what is pathogenicity

the ability to cause disease

what is virulence

the degree of pathogenicity

what are the three portals of entry

mucous membrane

skin

parenteral route

what is meant by parental route

deposited directly into tissues when barriers are penetrated

what is ID50? what does it measure

infectious dose for 50% of a sample population

measures virulence of a microbe

what is LD50? what does it measure

lethal dose for 50% of a sample population

measures potency of a microbe/toxin

what is adherence

when a pathogen attaches to a host tissue

how does the pathogen attach to the host cell

adhesins (ligands) on the pathogen bind to receptors on the host cells

what are the three ligands

1. glycocalyx
2. fimbriae
3. membrane proteins

microbes form …

biofilms

what is a biofilm

communities that share nutrients

what is a capsule made of

glycocalyx

what does capsules impair

phagocytosis

what are there components of the cell wall we should know

m protein

opa protein

waxy lipid

what does m protein resist

phagocytosis

what does the opa protein allow

attachment to host cells

what is the waxy lipid layer made of and what does it help resist

mycolic acid

digestion

what are coagulases

coagulate fibrinogen

what are kinases

digest fibrin clots

what are hyaluronidase

digests polysaccharides that hold cells together

what are collagenases

breaks down collagen

what are IgA proteases

destroy IgA antibodies (found in mucus membrane)

what is antigenic variation

pathogens alter their surface antigens

what are invasins

surface proteins produced by bacteria that rearrange actin filaments of the cytoskeleton

what does invasins cause

membrane ruffling

what do biofilms play a role in

evading phagocytes

biofilm bacteria are more resistant to …

phagocytosis and antibiotics

what are biofilm bacteria shielded by

extracellular polymeric substance of biofilm (EPS)

what are siderophores

proteins or molecules secreted by pathogens that bind iron more tightly than host cells

what molecule is required for most pathogenic bacteria

iron

what are the two consequences of siderophores

disrupts that host cell function

uses host cell nutrients

what are toxins

poisonous substances produced by microorganisms

what is toxigenicity

ability of a microorganism to produce a toxin

what is toxemia

presence of toxin in the host’s blood

what is intoxications

presence of toxin without microbial growth

what are exotoxins

proteins produced and secreted by bacteria

what are the two consequences of exotoxins

destroy host cells

inhibit metabolic functions

what are antitoxins

antibodies against specific exotoxins

what are toxoids

inactivated exotoxins used in vaccines

what are A-B toxins

contain an enzyme component (A part) and a binding component (B part)

inhibit protein synthesis

what are genotoxins

damage DNA by causing mutations, disrupting cell division and can lead to cancer

what are superantigens

cause an intense immune response due to release cytokines from host cells

cause symptoms of fever, nausea, vomiting, diarrhea, shock, and death

what are membrane-disrupting toxins

lyse host cells by disrupting plasma membranes

what are three membrane-disrupting toxins

leukocidins

hemolysins

streptolysins

endotoxins are only found in … bacteria

gram negative

what is the portion of lipopolysaccharides (LPS) of gram-negative bacteria

lipid A

what are plasmids

carry genes for toxins, production of antibiotics or resistance genes and other enzymes

what is lysogenic conversion

changes characteristics of microbe due to incorporation of a prophage

lysogenic conversion uses …

specialized transduction

what are two pathogen properties of viruses

cytopathic effects

alpha and beta interferons

what are cytopathic effects

visible effects of viral infections on a cell

what are alpha and beta interferons produced by and what do they protect

produced by virally-infected cells

protect neighboring cells from viral infection

what are the 5 portals of exit

respiratory tract

gastrointestinal tract

genitourinary tract

skin

blood