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Microbiology- Bacteriology
Staphylococcus (T Pierce)
27
Medical
Professional
09/02/2009

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Cards

Term
gram stain of Staph.
Definition
gram positive
Term
Growth medium of Staph.
Definition
5% sheep blood agar
Term
Taxonomy of Staph: family and genra
Definition
  • family: staphylococcaceae
  • genra
    • staphylococcus
    • gemella
Term
Key species of staph genus
Definition
  • S aureus
  • S epidermidis
  • S saprophyticus
Term
Staph physiology: morphology
Definition
  • gram positive cocci
  • multiplication in two dimensions with incomplete separation of daugther cells resulting in formation of clusters
Term

Staph physiology: growth/mode of metabolism

Definition
  • rapid growth of sharply defined, smooth opaque (light wont pass through colony) colonies on routine, nonselective media
  • white color of colonies
  • facultatively anaerobic (but given the choice, they would choose aerobic metabolism)
Term
Characteristics of staph
Definition
  • gram positive cocci, usually in clusters
  • positive for catalase
Term
Options for IDing staph aureus
Definition
  • slide coagulase test
    • if aureus, usually positive and occasionally negative
    • notice clumping of bacteria on test
  • tube coagulase test- positive
    • wait longer time than slide test, but you will see the same clumping
  • particle agglutination test- positive
    • detects both protein A:IgG interaction and coagulase, both causing particles to clump
  • biochemical test panel
Term
Appearance of negative particle agglutination test
Definition
milky suspension of particles
Term
Identifying coagulase negative staph.
Definition
  • slide coagulase test- usually negative
  • tube coagulase test- negative
  • biochemical test panel to ID species
Term
Compare colonies of S. aureus and S epidermis
Definition
  • S aureus- has yellow/gold color
  • S epidermidis- has white colonies (main coagulase negative staph species)
Term
S aureus: enzyme VF's and function
Definition
  • catalases- destroy hydrogen peroxide produced by cell defenses
  • coagulase- form fibrin clot (wall of site of infection)
  • hyaluroindases- CT dig. (so it can infiltrate tissue)
  • staphylokinase- fibrin clot lysis (allow spread)
  • lipase- lipid hydrolysis (attack defense mech. of sweat antimicrobial properties)
  • thermostable nuclease- nucleic acid polymer digestion (allow spread away from pus)
  • penicillinase- inactivation of penicillin
    • act as beta lactamase
Term
S aureus: toxin VF's and function
Definition
  • membrane active toxins- lyse RBC
    • more nutrients for baceria
  • Panton-Valentine leukocidin- lyses leukocytes
  • Exfoliatin- disrupt integrity of epidermis
  • TSS toxin 1- acts as superAg causing massive cytokine release
  • enterotoxin A thru E, G: induce vomitting
Term
Epidemiology of S aureus (aka where in body can it reside)
Definition
  • lives on:
    • skin
    • skin glands
    • mucous membranes
  • preferentially colonizes nares
Term
epidemiology of coagulase negative staph (aka where does it live)
Definition
  • live on:
    • skin
    • skin glands
    • mucous membranes
  • preferentially colonize:
    • skin (S epidermis) (S lugdunensis)
    • sweat glands (S haemolyticus)
    • mucus membrane (S saprophyticus)
Term
S aureus: virulence factors that are NOT enzymes or toxins and function
Definition
  • capsule- inhibition of phagocytosis
  • teichoic acid- adherence
    • part of cell wall
  • protein A- bind IgG at Fc portion
    • part of cell wall
Term
Coagulase negative Staph VF's
Definition
  • "slime"- facilitate biofilm formation (attach to "foreign bodies")
    • esp. in S. epidermidis
  • penicillinase- inactivate penicillin
Term
Different categories of S. aureus infections
Definition
  • localized
  • localized with rash
  • invasive infection
  • food poisoning
Term
Examples of localized infections of S. aureus
Definition
  • folliculitis (at hair follicle)
  • furuncles aka boil (aka enlarged folliculitis)
  • carbuncles (clusters of furuncles)
  • impetigo (superficial infection of skin usually at mouth or nose)
  • cellulitis (infection of tissue)
Term
Examples of localized infection with rash caused by S aureus
Definition
  • scalded skin syndrome (bad sun burn that opens up deeper layers of skin to infection)
  • TSS (
Term
Ex. of invasive infection caused by S aureus
Definition
  • endocarditis (infection of heart valve)
  • pneumonia
  • osteomyelitis (S aureus number one cause of it)
  • septic arthritis
Term
Examples of Coagulase negative Staph infections
Definition
  • prosthetic valve endocarditis
  • catheter associated bacteremia
  • CNS shunt infection
  • prosthetic device associated infection
  • peritoneal dialysis catheter (associated peritonitis)
  • UTI (number two cause of UTI in women is S. saprophyticus)
Term
Lab diagnosis of Staph
Definition
  • gram stain
  • real time PCR- detect staph DNA sequences
  • microarray testing
    • simultaneous ID of several staph. species and VF's
  • culture
    • nonselective media (5% sheep blood agar and chocolate agar)
    • selective medium
      • mannitol salt agar
Term
Antimicrobial resistant types of staph
Definition
  • oxacillin R (if you detect this, it is the equivalent of detecting MRSA)
  • vancomyocin R
  • inducible clindamycin R
Term
Lab indications of oxacillin resistance
Definition
  • growth on oxacillin agar
  • cefoxitin disk diffusion testing
  • oxacillin MIC determination (what conc. of oxacillin is needed to inh. growth of organism)
  • mecA gene product (penecillin binding protein 2a) (PBP2a) detection by latex particle agglutination
  • mecA gene detection by PCR
Term
Lab tests to det. vancomyocin resistance
Definition
  • grow on vancomycin agar
  • vancomycin MIC determination
Term
Lab tests to detect inducible clindamycin resistance
Definition
  • Antibiotic for skin, soft tissue infections
  • detect via D zone test
    • zone that look likes letter D
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