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38 Cards in this Set

  • Front
  • Back
Endotoxin is also called _ and it is part of _
LPS, part of gram neg.outer membrane
Toxic portion of LPS is _
Lipid A - released and becomes toxic after death of cell
LPS is heat _
Stable, and not strongly immunogenic
Mechanism of LPS
LPS activates macrophages and stimulates release of TNF and IL (IL1 - major mediator of fever). Macrophage activaion leads to tissue damage - can lead to shock and DIC
A-B components of exotoxin
B - binds to specific cell receptors to facilitate entry of component A
A - active toxic component
Damage cells from outside (alpha toxin of S. aureus makes pores in membranes)
Which toxin can be used as vaccine
Exotoxin - can be modified and turned into still immunogenic but no longer toxic
-Non essential
-Slime, polysaccharides
-Both gram + and gram - bacteria
-Protects bacteria against phagocytosis, immunogenic
Outer membrane
-Gram neg. bacteria ONLY
-Has LPS (endotoxin), lipid A (toxic),
Whats present in cell wall in gram + only?
Teichoic acids - stimulate TNF and IL 1 , also for attachment
Cell wall
Consists of peptidoglycan
-Gram + thick, gram neg. thin
-Consists of NAG and NAM
-Provides rigid support, shape and protection from osmotic damage
-Confers Gram reaction
-Inhibited by penicillin
Periplasmic space
-Gram neg. only
-"storage space" between inner and outer membranes
-Contains important enzymes ( like beta-lactamase)
-Also called fimbriae
-Can be common, sex or virulent
-Mostly in gram neg. bacteria
-Used for attachment and in conjugation
-Both gram + and gram neg.
-Can be used for motility
Lag phase
-Initial phase of bacterial growth
- Number of cells in the beginning is same as at the end
Log phase
-Rapid exponential growth
Stationary phase
Nutrients are being used up and toxic products begin to accumulate
-Number of new cells = number of dying cells
Obligate aerobes
-Require oxygen
-No fermentation
-Produces superoxide dismutase
Microaerophilic (example of organism)
Requires low but not full oxygen tension
- Campylobacter, Helicobacter
Facultative anaerobes
Will respire aerobically when oxygen is present and will use fermentation when oxygen is not - most bacteria
Obligate anaerobes
- Lack superoxide dismutase and catalase
-Cannot use electron chain
-Use fermentation only
-gram _
-arranged in _
Staph aureus - hemolysis and coagulase
Coagulase positive
Beta hemolysis
Staph aureus virulence factors and lab ID
-Protein A
Common diseases of Staph Aureus
-Infective endocarditis (IV drug users)
-Toxic shock syndrome
-Supurrative lesions
Staph aureus distinguishing characteristics
-Beta hemolysis, clusters of yellow gram + cocci on blood agar
-Catalase + , coagulase +
-Ferments mannitol on mannitol salt agar
Staph aureus reservoir
Normal flora of nasal mucosa and skin
Transmission of staph aureus
-Sneezing and hands contact
-Surgical wounds
-Foods associated with food poisoning
Pathogenesis of staph aureus
-Protein A inhibits phagocytosis, binds Fc portion of Ab
-Enterotoxin (A-E) - heat stable
-TSST- 1
-Coagulase - converts fibrinogen to fibrin clot
-Cytolytic toxins - toxin alpha of staph . aureus punches holes in cell membranes of human host
Exfoliatins - scalded skin syndrome and impetigo
Staph. aureus gastroenteritis
Enterotoxins preformed in food
-2-6 hours after ingestion - nausea, vomitting followed by diarrhea
Treatment of staph infection
Resistant to penicillin and most antibiotics - except methycillin
MRSA - resistant to methycillin too - use vancomycin
Gram _
Look like_
Gram neg.
Catalase neg.
Look like pairs or chains of cocci
S. pyogenes
-Group _
-Hemolysis _
-Sensitive to _
Beta hemolysis
Sensitive to bacitracin
Reservoir for Strep. pyogenes
Human throat and skin
Transmission of Strep. pyogenes
-Direct contact or respiratory droplets
Pathogenesis for Strep. pyogenes
M protein - antiphagocytic, used to type group A strep
Toxins of strep. pyogenes
Streptolysin O - immunogenic
Streptolysin S - non immunogenic
Both are hemo and cytolytic
Spreading factors for Strep. pyogenes
Streptokinase - breaks down fibrin clot
Strep. DNAse - liquiefied pus, extension of lesion
Hyaloronidase - important for spread in cellulitis