L8: Bacterial Pathogenicity Flashcards
_____: Sum of the characteristics that allow bacterium to produce disease (biochemical, structural, genetic)
Virulence
What are the two primary bacterial defense strategies?
1.Colonize and invade host surfaces
2. Evade complement, phagocytes, and antibody response
True or False: For a pathogen to penetrate intact skin, there has to either be disruption of skin (catheter, surgery) or transmission by arthropods (B. burdorfi, Lyme)
True
What do most bacteria have that makes it easier for mucin to trap them?
Mucin binding surface
What three features do bacteria that are able to EVADE trapping by mucin have?
- Lack mucin receptors
- Make mucin-degrading enzymes (hydrolases)
- Move between mucin strands
True or False: Colonic bacteria (clostridia, enterobacteria, B. fragilis) tend to be good at evading trapping by mucin layer
True
_____: small cysteine-rich cationic proteins, a natural bactericidal, that create PORES in bacterial membranes + diffuse through porins and peptidoglycan to reach CYTOPLASMIC MEMBRANE
Defensins
____, which has a negative charge, binds defensins and prevents them from reaching the cytoplasmic membrane
A. TLR
B. LPS
C. Olg gene
D. Bacterial membranes
B. LPS
What are two ways that the bacterial cell gets rid of defensins?
(hint: enzymes and pumps)
- Peptidase degrades it
- Cytoplasmic proteins pump them out
Which immunoglobulin molecule makes mucin sticky + binds bacterial antigens (via ABC and interact w/mucin via their Fc portions)?
A. sIgG Protease
B. sIGB Protease
C. sIGD Protease
D. sIGA Protease
D. sIGA Protease
Bacteria produce extracellular enzyme that
cleave ___ at hinge region, breaking links
between bacteria and mucin
IgA
What are the two type of microbial adhesion factors that exist?
Protein and Polysaccharide
Are Flagella, Fimbrae, Pili, S Layer, and Afimbrial polysaccharide or protein adhesions?
A. Polysaccharide Adhesions
B. Protein Adhesions
B. Protein Adhesions
True or False: The capsule and cell wall are protein adhesions
False - polysaccharide
True or False: Afimbriae, Flagella, Fibriae, and Pili are all appendages
True
Where in bacteria is the S Layer Found?
A. Cell envelope
B. Cell wall
C. Cytoplasm
D. Outer Membrane
A. Cell envelope
True or False: In medical situations, adhesions would be considered a major determinant of virulence for many pathogens
True
Which two rod-shape, hair-like protein structures on surface of
bacteria mediate attachment?
Pili and fimbriae
Tip structure of fimbriae and pili attaches specifically to receptor on host
cell, often carbohydrate residues of ____ or ___
glycoproteins or glycolipids
True or False: Fimbrae play vital role in conjugation ; comprise subunits
called pillin that forms a canal that allowed exchange of DNA between two bacterial cells; serves as receptors for certain viruses (bacteriophage)
False - Pili !
Which is found in greater abundance in the bacteria cell and is specialized for attachment of bacteria to its host?
A. Pili
B. Fimbriae
C. Flagella
B. Fimbriae
Pili are constantly lost and reformed (due to fragility). How does this help bacteria avoid host defenses?
Change pilus type by altering antigenicity
True or False: Pili and Fimbriae allow bacteria and host cell to form initial loose
contact, triggering mechanisms of tighter adherence
True
True or False: Mostly gram-positive pathogen (E.coli - urinary tract
infections and gastroenteritis), V. cholera,
P. aeruginosa, and Neisseria spp have fimbrae and pilli
False - gram negative!
After adhesion in a bacterial cell, there is ____ ____. What are the two outcomes?
signal transduction
- Host alters gene expression in response to adhesion binding
- +/- virulence genes of bacterial cell
_____: Cells surface proteins that do not form
pili
A. Apillus
B. Afimbrial
C. Aflagellar
B. Afimbrial
True or False: Afimbrial cells likely mediate WEAKER binding of bacterial and host cells
and may bind proteins on carbohydrates rather than host cells
False - Afimbrial cells likely mediate TIGHTER binding of bacterial and host cells
and may bind proteins on HOST CELLS
rather than carbohydrates
Yersinia, Neisseria, E. coli, and Strep/Staph all share which feature?
A. Apillus
B. Afimbrial
C. Aflagellar
B. Afimbrial
___: filamentous protein structures that provide swimming movement for most motile bacterial cells
A. Fibrae
B. Flagella
C. Pili
B. Flagella
Which pathogen has motility and is its determinant of virulence? (swims into intestinal mucosa to avoid being flushed out by peristaltic action of the gut)
A. Strepto
B. Staphylo
C. Vibrio
D. Enterbacteria
C. Vibrio
The distally located flagellar cap protein has been reported to function as adhesins in which three pathogens?
1) E.coli
2) P. aeruginosa
3) C. difficile
True or False: Flagella may also adhere to amoebae or connect two bacterial species
True
____: Proteins in outermost layer of cell envelope (underneath capsule if present) and has tiled appearance; can function as adhesions (!!)
S Layers
Which three pathogens have S Layers?
- Gram (+)
- Gram (-)
- Archea
How do S Layers contribute to bacterial virulence?
Protect bacterium against 1) complement and 2) phagocyte attack
Teichoic acids and gram-positive cell wall (as seen in Strep and Staph) are examples of ____ adhesions
A. Protein Adhesions
B. Polysaccharide Adhesions
B. Polysaccharide Adhesions
Capsule of Mycobacteria are also
recognized by host cell receptors to
promote ____
A. virulence
B. adherence
B. adherence
True or False: LPS/cell wall are polysaccharide adherins
True
___: Toxic components of the cell wall of Gram-
neg. and positive bacteria are central
mediators in the development of septic
shock
LPS
Why is iron concentration in
human body is low?
Mostly bound to: lactoferrin, transferrin, ferritin, and Hb
Bacteria secrete
siderophore, which carries ___
iron
Siderophores-iron
complexes are taken up by
special _____
receptors on the bacterial
surface
siderophores
What happens to iron-siderophore complexes that are internalized by bacteria?
Cleaved to release the iron inside the bacteria
True or False: Since free iron is scarce in tissue fluids and blood, bacterial siderophores compete effectively
for Fe3+ bound to lactoferrin and transferrin
True
What are two ways that bacteria remove iron?
- Bind and directly remove iron from host’s transferrin, lactoferrin, or Hb
- Bacteria make toxins, which kill host, leading to iron release
What is an example of a pathogen that does not require iron (iron abstinence) but uses other ions, such as: manganese?
A. Cholera
B. Vibrio
C. Borrelia burgdorgeri
D. Streptococcus
C. Borrelia burgdorgeri
What is the function of invasion?
Allows bacteria to gain deeper access into the host to
perpetuate the infection cycle
Which type of invasion occurs when a microbe breaks down the barriers of a tissue to disseminate in the host while remaining outside of host cells?
A. Intracellular Invasion
B. Extracellular Invasion
B. Extracellular Invasion
_____ degrade host’s extracellular molecules by producing elastase/collagenase, which aids tissue
invasion and is associated with keratitis, burn
tissue necrosis, and cystic fibrosis
A. P. aeruginosa
B. C. diff
C. E. Coli
D. Streptococcus
A. P. aeruginosa
Which five enzymes are secreted by beta-hemolytic Streptococcus and S. aureus to degrade host cell molecules?
- Hyaluronidase* : cleaves
proteoglycans in connective tissue - Streptokinase and Staphylokinase: breaks down fibrin clots
- Lipase: degrades accumulated host oils
- Nuclease: digests RNA and DNA
- Haemolysins: lyse erythrocytes and other cell types
S. aureus secretes ____, an enzyme that clots plasma, forming a sticky coat of fibrin around themselves; opposite effect of kinase
A. Lipase
B. Coagulase
C. Nuclease
D. Hyaluronidase
B. Coagulase
_____: A microbe penetrates the cells of a host tissue and gains access to the intracellular environment
A. Intracellular Invasion
B. Extracellular Invasion
A. Intracellular Invasion
Intracellular host invasion can be facilitated by which two aspects?
- Natural phagocytosis mechanisms (macrophage, neutrophil)
- Induced uptake: pathogens signals host cell to engulf adhered bacteria (type 3 secretion systems)
True or False: Salmonella and Shigella use type III
secretion systems
True
True or False: Host cells can be phagocytes (macrophages and neutrophils) or non-phagocytic cells (epithelial and endothelial)
True
What type of lifestyle do Chlamydia, Rickettsia, and
Mycobacterium have?
A. Facultative Intracellular
B. Obligate Intracellular
C. Anaerobic Intracellular
B. Obligate Intracellular
______is a facultative intracellular pathogen that persists for years and require extensive antibiotic therapy
A. Mycoplasm
B. Neiserria
C. Mycobacterium
tuberculosis
C. Mycobacterium
tuberculosis
What are the three general intracellular niches in which pathogens reside?
- Within phagolysome
- Within phagosome
- Within host cell cytosol
Chlamydia, Salmonella, Legionella, and Mycobacterium all:
A. prevent phagosome-lysosome fusion
B. escape from phagosome into cytoplasm
A. prevent phagosome-lysosome fusion
Where does Coxiella burnetti reside?
A. phagosome
B. phagolysome
C. host cell cytosol
B. phagolysome
Where do: Shigella, Listeria, and Rickettsia reside?
A. phagosome
B. phagolysosome
C. host cell cytosol
C. host cell cytosol
Escaping from phagosome into cytoplasm is
mediated by a bacterial protein that disrupts host’s
membranes either by degrading membranes or by
forming pores in the membrane
True or False: In addition to the host cell lysis, Shigella and Listeria utilize a pathway of cell-to-cell spread
True
- Involves extension of the infected cell into an adjacent cell, followed by membrane fusion
and formation of a bacteria-containing vacuole in the adjacent cell
Bacteria residing in macrophages and neutrophils may use these cells as _____ spread systemically via blood or lymphatic circulatory systems
vehicle to
Salmonella, Yersinia, and Brucella
move between tissue in which manner?
A. Lyse host membrane
B. Vehicle to spread
C. Cell to cell spread
B. Vehicle to spread
Chlamydia and Rickettsia:
A. lyse the host cell membrane
B. vehicle to spread
C. cell to cell spread
A. lyse the host cell membrane
- releasing infectious bacteria which attach to and invade adjacent cells
_____: network of polymers covering surface of
bacteria, usually polysaccharides (proteins)
Capsules
True or False: Capsules protect against host immune response (complement activation, phagocyte-mediated killing, and abx therapy) and leads to host mediated pathogenesis
True
What three pathogens utilize capsules?
- S. pneumoniae
- Neisseria
- P. aeruginosa
Some bacteria have capsule that resemble host
polysaccharide, such as: hyaluronic acid in _____ or sialic acid in ______
A. Neisseria and Salmonella
B. Neisseria and S. pyogenes
C. S. pyogenes and Neisseria
D. S. pyogenes and Salmonella
C. S. pyogenes and Neisseria
True or False: Bacterial capsules that resemble host polysaccharides, as in hyaluronic acid, is immunogenic
False - it is NOT immunogenic and host does NOT produce antibodies that opsonize capsular surface
True or False: Capsules may mediate specific or non-specific attachment
True
Which molecule is a reactive form of nitrogen made by some cells in the human body as an antibacterial defense?
NO
In E. coli, resistance to NO is mediated by ____, which is normally part of the respiratory system
flavohemoglobin
What is the function of flavohemoglobin?
Converts NO into NO3-
What are two LPS modifications that prevent formation of complement components?
- Sialic acid bound to O antigen (E. coli) or to LOS of Neisseria
- Changes in length of O antigen side chains prevents MAC killing (serum resistance)
Which two mechanisms prevent migration of phagocytes?
- Enzymes that degrade C5a, strategy for interfering with signaling function of complement
- Toxic proteins that kill phagocytes, inhibit migration, or reduce ox burst strength
What are the three major ways that pathogens evade host’s antibody response?
- Alter pilus protein
- Capsule that resembles host
- Bacteria coat themselves with host proteins (fibronectin or bind to Igg, e.g protein A or G)
______ helps bacteria evade antimicrobial peptides made by epithelial tissues in lungs (as part of innate immune response)
A. capsule shedding
B. capsule uncloaking
C. capsule evasion
A. capsule shedding
What are 2 host proteins that pathogens can coat themselves with to evade host antibody response?
Fibronectin
Immunoglobulin
- Note: these proteins bind Fc portion of antibodies but do not lead to bacteria opsonization
When Protein A binds to S. Aureus, the ___ portion of the IgG is not available for the receptor, leading the pathogen free to begin infecting cells
Fc portion
