LAB 1 - Staphylococcus, Micrococcus & Similar Organisms Flashcards
Staphylococcus aureus causes … (3)
wound infections, boils, and impetigo
Staphylococcus lugdunensis produces ______; often resembles …
biofilm; S. aureus
S. epidermidis produces ______ and is often associated with…
biofilm; instrumentation procedures, prosthetic devices sp. prosthetic heart valves
cause subacute bacterial endocarditis; if seen in blood culture, think of this!
Ss. saprophyticus causes
UTI in young women
holy moly white
S. intermedius is a recent concern in … it is also considered _______
wound specimen; zoonotic (
T or F. S. intermedius is partial coagulase pos.
T!
Micrococcus
- closely resemble CND
- found in environment and as indigenous skin flora
sticky staph
Rothia mucilaginosa
Rothia mucilaginosa is normal flora of the …. and it is an _______ GPC that tends to form clusters and ______.
oral cavity; encapsulated; tetrads
T or F. R. mucilaginosa is rarely an opportunistic pathogen
T!
T or F. DNAse is positive for micrococcus
F! it is neg; unlike Staph which is pos
T or F. Staph is ox +
F! ox - but micrococcus is ox +
Tests that differentiate micrococcus from staphylococcus (4)
Ox (Staph ox-; Micrococcus ox +)
DNAse (Staph +; Mic -)
Bacitracin or TA (Staph R; Mic S >10mm)
OF test (Staph produce acid from glucose ana; Mic are oxidative glucose utilizes)
Why could GPC stain as GN?
- overdecol
- antibiotics given; damage cell wall
- old cultures = cell walls degraded
NEVER stain off plates with antibiotics
S. aureus is carried in the _____ of 20-40% of the general population
nose
T or F Mic are slower growing than Staph
T! also non-hem and larger cocci
Catalase is read within
ten seconds; to avoid false interpretations such as in Enterobacteriaceae
RBCs will produce a weakly positive catalase result.. why?
pseudoperoxidase; so sample from tops of colonies
catalase is a _______ similar in structure to hemoglobin present in most _______-containing aerobic and facultative anaerobic bacteria
hemoprotein; cytochrome-continuing
T or F. Coagulase should be performed off a nonselective agar
T
Slide coagulase tests for…
bound coagulase or clumping factor; present on the surface of the cell wall of most strains of S. aureus and acts directly upon fibrinogen in plasma causing rapid clumping or agglutination of the cells
read within 10 secs
if pos = presumptive S. aureus bc could be slide neg but tube pos
tube coag test
- free extracellular coagulase
- reacts with coagulase-reacting factor = produce thrombin-like complex that converts fibrinogen to fibrin causing clot formation in plasma
NOTE = FP or FN can occur with non-sterile plasma
DNase media
- contains DNA
- either methyl green (colourless around colonies if pos) or toluidine blue O as indicator (pink for pos)
This bacteria ferments mannitol
S. aureus
- mannitol salt agar test = selective/differential primary culture medium
- inhibits mixed flora/most bacteria except Staphylococcus sp.
- acid produced lowers pH; phenol red turns yellow
- other Staph and Mc do not ferment mannitol = reddish colonies
SEA
Staphylococcal enterotoxin A
- intoxication; performed; not detected in stool bc toxins are absorbed from the gut
