Bacteriology (Exam 2) Flashcards
What population group is most susceptible to meningitis and pneumonia due to infections by Streptococcus agalactiae?
neonates
Prevention of complement activation/fixation by factor H is a function of what bacterial protien?
Streptococcus pyogenes M protein
Over 90% of staph areaus strains are resistant to what antibiotic?
penicillin
What bacterial virulence factor reduces phagocyte killing by converting hydrogen peroxide to water and oxygen?
catalase
What are two adhesins from Gram positive bacteria?
- fibronectin binding protein
- serin rich repeat protein
What is the function of exotoxins
-breakdown extracellular structures to promote movement and spread of extracellular microbes
What is the function of LPS on bacteria cells?
block access of the membrane attack complex to the bacterial plasma membrane
Are staphylococci gram + or -?
Gram positive
What variation of oxygen req is staph aureus?
Facultative anaerobe (O2 can be used if needed)
What bacterial species has a virulence factor that binds prothrombin
Staph aureus (coagulase)
What virulence factor of staph aureus causes puss formation?
leukocidin (forms pores in phagocytes)
converts plasminogen to plasmin, increasing invasion by digesting fibrin clots and cleaves C3b and IgG to inhibit phagocytosis
staphylokinase
What is an easy way to differentiate staph aureaus and epidermidis?
- aureus is hemolytic and gold colored
- epidermidis is non hemolytic and white colored
What bacteria cause folliculitis that turns to furuncles that turns to carbuncles that turns to bacteremia?
staph aureus (puss forming leukocidins)
What do superantigens do?
override the specificity of the T-cell response
What are TSSTs?
Toxic Shock Syndrome Toxins: mass activation of T-cells leads to mass activation of inflammatory cytokines
TSSTs are an example of…..
enterotoxin exotoxins (heat stable, chromosomal genes)
Tampons story is about
TSST, staphylococci?
What causes Staphylococcal scalded skin syndrome?
exfoliative toxins A and B (causes outer layer of skin to separate)
Where can nosocomial staphylococci found? What is a key feature of them?
- hospitals
- slime layer
What bacteria is associated with dental extraction risk?
staphylococcus epidermidis
60% of acute endocarditis is caused by….
staph aureus
80% of endocarditis with artificial heart valves is caused by….
staph epidermidis
Bacterial arthritis at any age is most frequently associated with…
staph aureus
What bacterial species is resistant to high temp and salt levels?
staph aureus
Pyogenes means…
puss forming
What streptococci are seen as diplococci?
strep pneumoniae
Diff between alpha and beta hemolysis?
Alpha: partial lysis (looks green, mitis and pneumoniae)
Beta: full lysis (clearing, pyogenes)
Strep pyogenes and strep galactiae are both…
hemolytic bacteria (pyogenes is A, galactiae is B)
What bacteria have M proteins?
Strep pyogenes
What are the two ways M proteins act as virulence factors?
- binds fibrinogen which blocks surface from complement proteins (factor H)
- binds complement control proteins to inhibit opsonins (C3 peptidase)
What are streptolysins?
cytotoxins secreted by strep pyogenes that disrupts plasma membranes of erythrocytes and phygocyte lysosomes
What virulence factor of strep pyogenes is responsible for scarlet fever?
superantigen SPE
Nectrotizing fasciitis is caused by…
strep pyogenes
Glomerulonephritis is a Type ___ hypersensitivity reaction.
Type III
Rheumatic fever is a Type ___ hypersensitivity reaction.
Type II
Strep galactiae can cause pneumonia in ________, meningitis and bacteremia in __________, and urinary tract infections in ____________.
pneumonia -> neonates less than 7 days
pneumonia and bacteremia -> neonates greater than 7 days
urinary tract infections -> pregnant women
What bacteria is considered a reservoir for antibiotic resistance?
enterococcus faecalis. High virulence, multiple plasmid and chromosomal Ab resistances
Only a certain type of strains of strep pneumoniae are virulent. What are they?
-encapsulated strains
How are klebsiella pneumonia and mycoplasma pneumonia different from pneumococcal pneumonia?
kleb and myco have no vaccine
What are three main virulence factors of streptococcal pneumoniae?
Hint: (blood, protection, protease)
- alpha hemolysis
- capsule
- secretory IgA protease
Meningitis risk due to ____________ seems to increase as we age.
strep pneumoniae
Are Neisseria gonorrhoeae gram positive or negative?
Gram negative (diplococci)
What is unique about neisseria sp cell membranes?
they have lipooligosaccharides instead of LPS (lack O antigen)
What makes N. gonorrhoeae reistant to vaccination?
phase and antigenic variation of pilin genes
Does N. gonorrhoeae have a capsule?
no
What two genes recombine to create a constantly changing pilus antigen on N. gonorrhoeae?
pilS randomly recombines with pilE for unlimited varients
What causes frequent variation in Opa expression in N. gonorrhoeae?
slipped strand mispairing
Why might a gram negative rod randomly not express genes for fimbriae?
phase variation: random flipping of promotor sequence. Flipped wrong way is off, flipped right way is on
Why might IgA have no effect on N. gonorrhoeae?
the bacteria are coated in Fab fragments that block complement activation and binding of other antibodies
What addition to lipooligosaccharide inhibits complement fixation to n. gonorrhoeae?
sialic acid
What part of N. gonorrhoeae causes secretion of pro-inflammatory cytokines?
shedding of endotoxin (LOS) which binds to TLR-4
Where does neisseria meningitidis replicate?
in subarachnoid space
What are the 4 main virulence factors of N. meningitidis?
- large capsule
- IgA protease
- Pili
- shedding of lots of endotoxin (LOS)
Are bacteroidales gram positive or negative?
gram negative
Are bacteroidales aerobes/anaerobes, pathogens/commensals?
- strict anaerobes
- commensals (opportunistic pathogens)
Why is bacteroides fragilis the most common isolated specimen from abscesses?
most oxygen resistant
What are the three virulence factors of Bacteroidales fragilis?
- superoxide dismutase
- catalase
- polysaccharide capsule
Bacteriodales cause what diseases?
- peritonitis
- pulmonary abscess
A disease that starts with 100’s of different species and few are left in the abscess stage.
-polymicrobial diseases (bacteroidales involved)
What are the last two types of microbes left towards the end stages of an abscess?
- facultative anaerobes
- some strict anaerobes (become predominant in last stage)
What organism causes scalded skin syndrome?
staphylococcus aureus
What bacterial virulence factor has an activity that results in creation of a fibrin coat around bacteria?
coagulase
What role does staphylokinase play for staphylococcus aureus?
cleaves C3B and IgG
What causes myocarditis in susceptible individuals?
rheumatic fever
Which organism undergoes phase variation of Opa proteins?
Neisseria gonorrhoeae
What factor in the most important in allowing intravascular survival of Neisseria meningitidis?
bacterial capsule
Why does Bacteroidales fragilis resist phagocytosis?
it has a capsule
