7.6 STAPHYLOCOCCUS SP Flashcards
2 family and 3 species
Micrococcaceae
Staphylococcaceae
- S. aureus: white opaque
- Coagulase negative : just white
Staphylococcus - S. saprophyticus
reminder of what media is usd for urine one m,ore in her slide
BA
CLED
MAC
PEA
Chromogenic
GROWTH OF STAPHYLOCOCCUS
BA: small white (opaque), gold; beta- or gamma-hemolytic
CLED: can be LF or NLF
MAC: no growth: inhibits gram +
PEA: small white (opaque), gold, inhibits gram -
All species will demonstrate good growth after 18-24 hours
All species are facultative anaerobes and mesophilic
how can you distinguish the opaque white and plain white
in the well opaque will look chalky while white jsut look whote
staph is never what color
grey
what kind of unique hemolyiss can happen
double zone beta hemolosysi
IDENTIFICATION OF STAPHYLOCOCCACEAE
gram and shape
Gram stain: Gram positive cocci in
clusters
Cocci are very round (divide via many axes)
IDENTIFICATION OF MICROCOCCACEAE
shape and gram
Gram stain: Gram positive cocci in
tetrads
Cocci are very round (divide via many axes)
STAPHYLOCOCCUS AUREUS
Normal flora of nose, nasopharynx, skin, perineum
Endogenous and person-to-person transmission
Nosocomial and community-acquired antimicrobial resistance
i.e. MRSA (Methicillin-resistant Staphylococcus aureus)
Causes infection due to many virulence factors: dont need to know which
Localized skin infections:
Impetigo, folliculitis, furuncles, and carbuncles
STAPHYLOCOCCUS AUREUS
wound vs deep infection
wound
* Can be community or
nosocomially acquired
* Can be extremely dangerous
and lead to necrosis or
intense suppuration
* Often found with S. pyogenes
deep
* Bacteremia, endocarditis,
osteomyelitis, joints, deep
organs, lungs, tissues (invasive)
* Scalded skin syndrome in
neonates
* Food poisoning
* TSS
STAPHYLOCOCCUS AUREUS color and hemo
WHITE OP BH
MICROCOCCUS SP.
Normal flora of human skin, mucosa,
and oropharynx
Rarely associated with infection
Typical lemon-yellow coloration
STAPHYLOCOCCUS SAPROPHYTICUS
Normal flora of skin and GUT
Only associated with UTI in young, sexually active females
Community-acquired (not nosocomial like most other coagulasenegative Staphylococcus infections
STAPHYLOCOCCUS SAPROPHYTICUS
color and hemo
WHITE NH
COAGULASE-NEGATIVE STAPHYLOCOCCUS
Includes a group of bacteria with the same genus but several different
species
We only determine species under specific circumstances (i.e. CSF)
Normal flora of skin and mucous membranes
Less virulent than S. aureus
Opportunistic, endogenous, and person-to-person transmission
Most infections are nosocomial and associated with implanted medical
devices
Invasive procedures provide opportunity
Common contaminants of specimens because they are “ubiquitous
colonizers”
COAGULASE-NEG STAPHYLOCOCCUS
colorn and hemo
sm white NH
BIOCHEMICAL TESTS FOR STAPHYLOCOCCACEAE
5
catalase
Staphaurex
Tube Coagulase
Novobiocin Susceptibility
catalase test is the same as in previous / buble deue to catalse enzyme
microdase was FYI
coagulase test
Looking for the enzyme coagulase possessed by certain organisms
Staphylococcus aureus possesses coagulase in two forms..
Bound coagulase (clumping factor)
Free coagulase
LATEX AGGLUTINATION (STAPHAUREX®)
bound coagulase
Tests for clumping factor and protein A (found in 95% of all S. aureus)
Latex beads coated with fibrinogen and the Fc portion of IgG that specifically
binds to protein A
Fibrinogen will bind with the clumping factor on the bacterial cell wall and IgG will
bind with protein A
latex particle has fibrinogen and IgG attached and from the bacteria get the Protein A and Clumping factor if present
Positive: Staphylococcus aureus
Negative: All other Staphylococcus sp.
Note: Always confirm with a tube coagulase
black background
FREE (TUBE) COAGULASE
An extracellular protein enzyme possessed by S. aureus
Coagulase-reacting factor (CRF – a modified or derived thrombin molecule) in
plasma is activated and forms a CRF-coagulase complex
The complex reacts with fibrinogen to produce a fibrin clot
Positive: Staphylococcus aureus
Negative: Coagulase negative Staphylococcus
Must check at 3 hours because clot can form and then be dissolved by staphylokinase (would be false negative at 24 hours)
NOVOBIOCIN SUSCEPTIBILITY
Testing an organisms susceptibility to the antibiotic, novobiocin
Can visualize sensitivity to antibiotic by a zone of inhibition of bacteria growing
around a filter paper disc that has been impregnated with the antibiotic
Used to identify Staphylococcus saprophyticus from urine specimens ONLY
use of an MH and BA plate, QC cloudiness
Resistant: Staphylococcus saprophyticus
Susceptible: Other Staphylococcus sp.
greater than 16mm
have to streak in 3 planes
very nice summary at the end of the slides PRINT before the pathway
