L3 Microbial Pathogenesis and Mechanisms of Virulence Flashcards
pathogenicity
ability to cause disease
virulence
degree of damage or disease resulting from infection
infectivity
likelihood of causing infection and or disease with exposure to a particular poison
rhinovirus
ss + RNA, naked virion causes common cold high infectivity, low virulence
influenza virus
ss - RNA, segmented enveloped causes flu moderate infectivity, greater virulence, host dependent
ebola
ss -RNA, enveloped causes hemorrhagic fever high infectivity, high virulence
endogenous acquisition transmission of microbial agents
escape from location where it is part of the normal microbiome
exogenous acquisition transmission of microbial agents
person to person, animal to person (zoonoses), insect to person, environmental
conceptual framework for infectious diseases
- encounter 2. entry 3. spread 4. multiplication 5. damage 6. outcome
microbial virulence factors
increase virulence NOT REQUIRED FOR GROWTH OUTSIDE OF THE CELL 3 main categories 1. structures involved in attachment, adherence and invasion 2. toxins involved in cell or tissue damage 3. processes involved in immune avoidance
bacterial pili
aka fimbriae filamentous structures extending from the bacterial surface - sponsor initial adherence to host cells or extracellular matrix (specific or non-specific) - polymers of bacterial proteins known as pilins
TYPE IV pili
specific type of bacteria pili (there are many types of pili) extend, bind, and retract promote surface motility, micro-colony, and biofilm formation, adherence of host cells and immune evasion
flagella versus pili
- both are filamentous appendages - pili are shorter, increased number, and thinner - flagella composed of flagellin - pili are composed of pilins
E coli, O157: H7 what is the H7
type of flagella
T/F Only pili and not flagella are virulence factors?
false both are just different structures and functions
specialized bacterial secretion systems are important for gram +/gram - bacteria
gram - bacteria can use type III, type IV and V systems to inject substrates into other cells
T3SS
aka bacterial nanomachines specialized bacterial secretion systems inserts toxins inserts receptors
viral attachment
mediated by proteins on surface of virion; proteins engage receptor on host cells and then endocytose
capsid proteins on naked/encapsulated viruses
naked
glycoprotein spikes on naked/enveloped viruses
enveloped
HIV
- ssRNA, enveloped virus - 2-part glycoprotein spike in the viral envelope (GP120 and GP41) - bind CD4 on human T-cell - conformational change allows contact with co-receptor
Endotoxin
- lipopolysaccharide (LPS) - gram - outermembrane - lipid and saccaride portion
which portion of the endotoxin is toxic?
- lipid portion - potent stimulator of innate immune response
PAMPs (pathogen-associated molecular patterns)
located on the pathogens
bacterial PAMPS engage extracellular/intracellular TLRs?
extracellular
viral PAMPS engage extracellular/intracellular TLRs?
intracellular
exotoxins
- secreted toxins produced by Gram + and - bacteria - toxin genes are frequently encoded on plasmids or bacteriophages
A + B exotoxin
A- active B- binding
A + B Toxin mediated diseases
DTP 1. diphtheria 2. tetanus 3. pertussis (whopping cough)
DTaP
vaccine for DTP
toxoid
(inactivated toxins) prevents toxin mediated disease
pore-forming toxins
poke holes in host cell membrane
superantigens
toxins that can cause toxic shock ex. engage T-cells and antigen presenting cells (MHCII cells) in the adaptive immune system resulting in nonspecific recognition of antigens bypasses antigen specificity and leads to increased T-cells and cytokine storm
examples of superantigens
staphylococcal and streptococcl
immune avoidance by microbial pathogens
structures and processes important examples: 1. antigen variation 2. polysaccharide capsules 3. biofilms
polysaccharide capsules
structural way of how microbial pathogens can avoid immune system extracellular component of gram + and - bacteria that can avoid phagocytosis and avoid immune recognition
herpes viruses travel from the periphery to dorsal root ganglion and are latent in __________ and why is this important
sensory neurons immune avoidance by microbial pathogens
immune avoidance by microbial pathogens structures
- bacterial and fungal polysaccharide capsules 2. antigens that induce blocking antibodies 3. molecules that inactivate antibodies 4. molecules that mimic host structures and are not recognized as foreign
immune avoidance by microbial pathogens process
- antigen variation 2. avoiding immune surveillance 3. suppressing immune response
- Match the following bacterial structures with their primary role(s) in pathogenesis. A. Pili B. Polysaccharide capsule C. LPS D. Staphylococcal Protein A Immune avoidance Attachment to host cells Stimulates innate immune responses Thwarts phagocytosis
A. Attachment to host cells B. Immune avoidance; Thwarts phagocytosis C. Stimulates innate immune responses D. Immune avoidance
- The A subunit of Cholera Toxin has which of the following activities? Explain the consequences of this activity. A. Increases adenylate cyclase activity B. Forms pores in epithelial cell membranes C. Acts as an endotoxin D. Acts as a superantigen
Increases adenylate cyclase activity
