Gram
Positive Cocci
Micrococaceae
Micrococci
Staphylococci
Stomatococci
Coagulase
Positive
Staphylococcus
aureus
-
bunches
of grapes
-butyrous
-Mannital
salt agar (yellow)
-catalase
positive
-Characteristics
that differentiate coagulase positive staphylococci
| organism |
Slide |
tube |
pyr |
thermostable
nuclease |
VP |
ornithine |
| S. aureus |
+ |
+ |
- |
+ |
+ |
- |
| S. lugdunenis |
+ |
- |
+ |
- |
+ |
+ |
| S.intermedius |
- |
+ |
+ |
+ |
- |
- |
| S.schleiferi |
+ |
- |
+ |
+ |
+ |
- |
S.aureus
Pathogen
skin,
wounds, pneumonia, osteomylitis,
endocarditis,
septic shock , toxic shock syndrome
food
poisoning-intoxication
Virulence
factors
cell
wall- tough
polysaccharide
capsule
protein
A
enzymes
toxins
superantigens-
immune modulators
exfoliatin-scalded
skin syndrome
-enterotoxin
-toxin
1 TSST-1-toxic shock syndrome
Antibiotic Resistance
- Most
strains are penicillin resistant
-beta
lactamase
-Also
resistant to synthetic B-lactamase penicillin, oxacillin, methicllin, nafcillin
-penicillin
binding protein in the cell wall
MRSA(Methicillin
Resistant S. aureus)
Detect
MRSA
1ug
oxacillin disk
on20%NaCL
to cation supplementedMueller Hinton
Broth
Screen
MRSA
6ug
oxacillin
on
4%NaClsupplemented Mueller Hinton Agar
Sensitive
to
Vancomycin
, rifampin
Carrier
State
-Reservoir
is hospitalized patients
-hospital
and nursing homes require
MRSA
screening
Strain
identification
-phage
typing
Coagulase
Negative
Infections
-compromised
host, cancer patients, neutropenic patients, indwelling catheters, shunts,
CAPD, UTI in sexual active young women
S.
epidermidis
Infections
-native
heart valves, intravenous catheters, artificial heart valves, CAPD, bacterial
adherence, prosthetic joints, CNS shunts
S.
saprohyticus
Urinary
Tract infections (UTI)
Novobiocin
resistant
5
ug disc<5mm diameter
Other coagulase
staphylococci identified by Staph TracTM, Micro Scan, Vitek
Infections
Prosthetic
devices:
S.warneri
S.
ludenesiscoagulase
positive
Compromised
hosts:
S.cohnii
S.haemolyticus
S.hominis
S.saccharolyticus
S.schleiferi
- coagulase positive
S.simulans
Coagulase negative staphylococci
Extracellular
products
hemolysins,
capsules, slime(adherence) , formation of a glycocalyx
UTI
suceptible to most antibiotics except nalidixic (gram - )
MRS-
resistant to Beta lactams and cephalosporin, imipenin
Stomatococcus
S.
mucilaginus
-encapsulated
normal flora of the oral cavity
-opportunist
in drug abusers
-sticky
capsule adheres to agar
-grows
well on 5% NaCL
-poor
growth on Mueller Hinton
-vancomycin
sensitive
Micrococci
-saprophytic,
pigmented
-tetrads
-opportunist
by accidental introduction
M.agilis
(motile)
M.kristinae
M.luteus
M.lylae
M.nishinominacnsis
M.roseus
M.sedentarius
M.varians
Differentiation
Catalase
+
Coagulase
-
-Not
lysed by lysostaphin
-resistant
to furazolidone
-contains
cytochrome e (modified oxidase test)
-susceptible
to 0.04 units of bacitracin
Selected
characteristics of coagulase negative staphylococci
PYR
clumping
factor
urease
maniton
sucrose
zone
of inhibition
10u<11mm
bacitracin
300u<10mm
polymyxin
5ug<12mm
nobobiocin