Common Bacterial Pathogens Flashcards
Staph. aureus: gram stain, carrier location, catalase?
gram positive cocci in clusters; carried in anterior nares and perineum; catalase positive
Staph. epidermidis: gram stain, carrier location, catalase?
gram positive cocci in chains or pairs; normal skin flora; catalase negative
Strep. pyogenes: gram stain, carrier location, catalase?
gram positive cocci in chains or pairs; strep throat; catalase negative
Strep. pneumoniae: gram stain, carrier location, catalase?
gram positive diplococci; normal UR flora; catalase negative
Staph. aureus pathogenicity?
pathogenic; cutaneous infections (folliculitis, boils, wound infections); foreign bodies and splinters; TSS; pneumonia; bacteremia/endocarditis
How does Staph. aureus persist in cutaneous infections? What is the treatment?
formation of a fibrinous capsule; drainage of the abscess
____ is an essential virulence factor that is assoc. with the formation of the fibrin capsule.
Coagulase
What is the major cytotoxic agent released by Staph. aureus?
Alpha-toxin
How does Alpha-toxin work?
it forms a beta-barrel pore
Why does Staph. aureus like foreign bodies?
they provide a surface for colonization and interferes w/ phagocytosis
What is a superantigen toxin?
antigens that cause non-specific activation of T-cells, leading to massive cytokine release
Superantigens can cause up to _____ of all T-cells to become activated, as compared to a normal antigen-induced T-cell response of _____.
25%; .0001-.001%
Name 3 staph toxin mediated diseases.
- TSS
- staph food poisoning
- scalded skin syndrome
What are the s/s of TSS?
high fever, low BP, malaise, confusion, rash resembling a sunburn
What can TSS lead to?
stupor, coma, multiple organ failure
What is the causative factor of TSS?
local Staph. aureus infection that produces toxin that circulates
What does the TSS rash look like, and what happens with it?
a sunburn over any part of the body, including lips, mouth, soles, and palms; it desquamates (peels off) after 10-14 days
What is Staph. food poisoning?
ingestion of preformed toxin in contaminated/improperly stored food
Staph. aureus pneumonia is common in _____.
health care acquired settings
What is the mortality of Staph. aureus pneumonia?
about 50%
Name one of the most common pathogens causing endocarditis/bacteremia.
Staph. aureus
What drugs can Staph. aureus be resistant to?
penicillin, methicillin, and vancomycin
What is an SSNA?
staph species, not aureus
Where do Staph. epidermidis normally live?
skin
Staph. epidermidis is usually a ____ infection involving _____.
localized; foreign body
What organism is assoc. with slime production?
Staph. epidermidis
What is the slime of Staph. epidermidis?
an extracellular glycocalyx allowing for adhesion and protective biofilm
What is Staph. epidermidis resistant to?
methicillin
Why is Staph. epidermidis hard to treat?
the biofilm is hard to penetrate and it’s resistant to methicillin
What diseases does Strep. pyogenes cause?
pharyngitis/strep throat, skin and wound infections
Name 2 post-streptococcal diseases.
- glomerulonephritis
2. Rheumatic fever
What is glomerulonephritis?
type 3 immunopathology: strep antigen-antibody complexes deposited in the kidney and accumulate in the BM
What is Rheumatic Fever?
autoimmune inflammatory disease; antigens cross react to myocardium and heart valves–NOT a colonization of bacteria
What is unique about Group A Strep skin infections?
they spread
What is the primary virulence factor in Strep. pyogenes?
M-protein
What is M-protein?
a surface protein on Strep. pyogenes that inhibits phagocytosis, kills PMNs, and enhances adherence to epi
What protects against M-protein?
antibodies
Where is Strep. pyogenes normally found?
in the pharynx
How does Strep. pneumoniae evade host defenses?
it has an antiphagocytic polysaccharide capsule
What is PPSV23?
pneumovax; protects against invasive Strep. pneumoniae
What diseases are invasive Strep. pneumoniae?
meningitis, bacteremia/septicemia, pneumonia
What diseases are noninvasive Strep. pneumoniae?
pneumonia, sinusitis, otitis media, bronchitis
What are the predisposing factors for Strep. pneumoniae?
young or old age, alcoholism, respiratory viral infections
Why is alcoholism a predisposing factor for Strep. pneumoniae?
it negatively affects the mucocilliary escalator
What is Prevnar?
the children’s pneumonia vaccine
What is Strep. pneumoniae resistant to?
penicillin
What does Viridans streptococci cause?
infective endocarditis and dental caries
Viridans streptococci are either ____ and turn green on blood agar plates, or are _____ and do not.
alpha-hemolytic; nonhemolytic
Where is Viridans streptococci normally found?
in the mouth
What does Viridans streptococci produce that allows it to adhere to teeth and heart valves?
dextrans
What do dextrans allow Viridans streptococci to do?
adhere to teeth and fibrin/platelets in damaged heart valves
What do Enterococcus faecalis/faecium cause?
UTIs, infections of surgical wounds, biliary tract infections, endocarditis
Where is Enterococcus faecalis/faecium normally found?
GI flora
What is Enterococcus faecalis/faecium resistant to?
vancomycin
What is a hospital-acquired infection called?
nosocomial infection
What is a nosocomial infection?
a hospital-acquired infection
The most common ____ in human disease are members of the genus Clostridium.
gram + rods
The most common gram + rods in human disease are members of the genus ____.
Clostridium
Clostridum are strict ____ and form ____, which are extremely resilient.
anaerobes; endospores
What diseases does Clostridium difficile cause?
hospital-acquired diarrhea and pseudomembranous colitis
What diseases does Clostridium tetani cause?
tetanus
What diseases does Clostridium botulinum cause?
botulism
What diseases does Clostridium perfringens cause?
gangrene and other tissue infections
What kind of toxin does C. diff produce?
an entertoxin and a cytotoxin
How is C. diff diagnosed?
ELISA or PCR of stool sample
Name 2 gram negative rods.
- E. coli
2. Pseudomonas aeruginosa
Name a gram negative cocci.
Neisseria gonorrhoeae
What bacteria family lack cell walls?
Mycoplasma and ureaplasma
