Microbiology exam I
Terms
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- 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 - Cytolysins
- 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
- Capsule
-
-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) - Pili
-
-Also called fimbriae
-Can be common, sex or virulent
-Mostly in gram neg. bacteria
-Used for attachment and in conjugation - Flagellum
-
-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 -
Staphylococcus:
-gram _
-catalase_
-arranged in _ -
-Positive
-Positive
-Clusters - Staph aureus - hemolysis and coagulase
-
Coagulase positive
Beta hemolysis - Staph aureus virulence factors and lab ID
-
-Protein A
-TSST-1
-Enterotoxins
-Exfoliatins
-Cytolysins - Common diseases of Staph Aureus
-
-Infective endocarditis (IV drug users)
-Abscesses
-Toxic shock syndrome
-Gastroenteritis
-Supurrative lesions
-Osteomyelitis - 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 -
Streptococcus:
Gram _
Catalase_
Look like_ -
Gram neg.
Catalase neg.
Look like pairs or chains of cocci -
S. pyogenes
-Group _
-Hemolysis _
-Sensitive to _ -
A
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