Micro Lab Stuff Flashcards
When members of the normal flora relocate to a different spot, what do they become?
Opportunists
**this is especially true in people who are immunocompromised or debilitated
If a patient is intubated and an infection results, what category does this infection fall into?
Iatrogenic infection
Normal Flora of the skin
Staphylococcus Epidermidis
Normal Flora of the nose
Staphylococcus Epidermidis (90%) Staphylococcus Aureus (20%)
Normal Flora of the mouth/throat
Viridans Streptococci (>50%) Niessiera Species Staphylococcus Epidermidis Corynebacterium Species (diphtheroids) Anaerobic
Normal Flora of the colon
Escherichia coli
Proteus Species
Enterococcus species
What is the purpose of doing a streak dilution?
- It allows you to identify individual colonies of homogenous species
What is alpha hemolysis?
Green hue produced by partial lysis of RBCs by bacteria
What is beta hemolysis?
Complete lysis of RBCs with CLEAR zone
non-hemolytic/gamma hemolytic?
No RBC lysis
What plate do you use for Gram (-) organisms?
EMB
What does lactose +/- mean?
EMB plate used:
Lactose +
- green if E. Coli
- Brownish if Klebsiella
Lactose -
- no color change
Why are MSA plates selective of staph?
- what is the differential?
- Only grow staph because they have such a high salt content
- Color change by fermentation = Staph. Aureus
- Otherwise its staph epidermidis
What 3 species can grow in high salt environments?
- Enterococcus
- Steptococci B
- Staphylococci
What does a POSITIVE COAGULASE TEST from a species isolated from a mannitol agar indicate?
- Staphylococcus Aureus
What chemical does a taxo P disc contain?
- taxo A?
Taxo P - Optochin - kills Streptococcus pneumoniae
Taxo A - Bacitracin - kills GAS (Streptococcus pyogenes)
Is staphylococcus epidermidis hemolytic?
NO
What does Sensitive, Intermediate, and Resistant refer to in Kirby-Bauer testing?
Sensitive - MIC is lower than attainable blood levels
Intermediate - MIC near maximum blood levels
Resistant - MIC above attainable blood levels
What is HA-MRSA and CA-MRSA?
- how do their rates compare with those of the general population .
Normal Populations:
5% of S. aureus isolates
HA-MRSA
- Health-care Associated MRSA
- 60% of S. aureus isolates
CA-MRSA
- Community Associated MRSA
- LESS drug resistant than HA-MRSA from less drug exposure
What tools to bacteria need to be Methacillin resistant?
- Low affinity penicillin-binding protein PBP2.
- encoded by mecA (mobile genetic element)
- encoded SCCmec (cassette chromosome mec)
Nosocomial infection
Infection occuring >48 hrs after being at the hospital
what is community associated infection?
Positive sample from outpatient or from an inpatient obtained
G(-), diplococci, mostly pairs
a. Neisseria spp
G(-), bacillus, lactose (+), green sheen
b. E. Coli
G(-) bacillus, lactose (+)
c. Klebsiella pneumoniae
G(-) bacillus, lactose (-)
d. Proteus spp
G(+) cocci, clusters, catalase (+), mannitol (+) (ferment)
e. Staph aureus
G(+) cocci, clusters, catalase (+), mannitol (-)
f. staph epidermidis
- G(+) cocci, chains, alpha-hemolytic, taxo P sens
g. strep pneumoniae
G(+) cocci, chains, alpha-hemolytic, Taxo P resis
h. Viridans strep
G(+) cocci, chains, non-hemolytic, salt sensitive
i. strep spp
- G(+) cocci, chains/pairs, non-hemo, salt resistant
j. enterococcus spp
G(+) cocci, chains, beta-hemo, Taxo A sensitive
k. strep pyogenes
G(+) cocci, chains, beta hemo, taxo A resis
l. other B-hemolytic strep
