Week 4- Staph, Throat, Wound Cultures

Question 1

General Facts of Staph sp:

Answer 1

found everywhere, normal flora of skin and mucous membranes, spread by direct contact, human pathogen

Question 2

What is the gram stain for Staph sp?

Answer 2

gram positive cocci in singles, pairs and clusters

Question 3

What is coagulase?

Answer 3

enzyme virulence factor binds fibrinogen and converts to insoluble fibrin causing organism to clump and adhere to host tissues.

Question 4

Which staph species is coagulase positive?

Answer 4

staph aureus (most other are negative)

Question 5

What are the three most common staph isolates?

Answer 5

Staph aureus, staph saprophyticus, staph sp coagulase negative (staph epidermis is most common coagulase negative species)

Question 6

Where is Staph Aureus considered normal flora?

Answer 6

skin and mucous membranes

Question 7

What are staph aureus’s virulence factors?

Answer 7

capsule, enzymes, toxins, protein A

Question 8

S.aureus: In a toxin-mediated disease, will you culture?

Answer 8

No. Examples of toxin-mediated diseases: scalded skin syndrome, toxic shock syndrome, food posioining

Question 9

S. aureus: do you culture suppurative infections?

Answer 9

yes. Examples of suppurative infections: impetigo, folliculitis, boils, wounds, septecemia, pnuemonia, endocarditis, septic arthritis, osteomyelitis, and nosocomial infections.

Question 10

S. aureus: Do you perform a susceptibility test?

Answer 10

yes! >90% are resistant to PCNs

Question 11

How should you treat most S. aureus?

Answer 11

With a penicillinase resistant PCN (methicillin, oxacilin, nafcillin)

Question 12

How should you treat HA-MRSA?

Answer 12

MRSA is oxacillin resistant. HA-MRSA should be treated with vancomycin.

Question 13

CA-MRSA treatment?

Answer 13

less resistant to antibiotics than HA-MRSA. drug choice depends on site.

Question 14

What is VISA and VRSA?

Answer 14

Vancomycin intermediate staph aureus. Vancomycin resistant staph aureus. Drug of choice is based on susceptibility results.

Question 15

Staph saprophyticus is coagulase…

Answer 15

negative

Question 16

What is the clinical significance of Staph saprophyticus

Answer 16

UTI infections, (especially young sexually active women)

Question 17

How do you diagnose staph saprophyticus?

Answer 17

Culture. Susceptibility testing is not usually done because of the lack of correlation between in vitro and in vivo.

Question 18

What are your treatment options for staph saprophyticus?

Answer 18

Oral cephalosporin, amox/clauvulante, fluroquinolone, bactrim, etc (see notes for all)

Question 19

What is the most frequently isolated staph sp coagulase neg?

Answer 19

staph epidermis

Question 20

What is the clinical significance of staph sp. coagulase neg? Where is staph sp neg coagulase considered normal flora?

Answer 20

prosethetic deives and intravascular cather infections. skin and mucous membranes!

Question 21

What virulence factors does staph epidermis have?

Answer 21

capsule, produces extracellular slime substance.

Question 22

What are some common infections caused by staph epidermis?

Answer 22

subacute bacterial endocartitis on prosthetics!! also, meningitis involving shunts and septicemia involving catheters. THINK PROSTHETICS!

Question 23

Staph epidermis: do you culture? do you do susceptibility testing?

Answer 23

yes, do blood culture. you will perform susceptibility testing if it is a presumed pathogen.

Question 24

how do you treat staph epidermis?

Answer 24

naficillin/oxacillin or vanco if those are resistant.

Question 25

What are the normal flora of the upper respiratory tract?

Answer 25

strep pneumonia, staph aureus, h. Influenza

Question 26

Should you ever do a comprehensive throat culture?

Answer 26

No! there are too many species present.

Question 27

What kind of culture might you do from the throat?

Answer 27

if you suspected diptheria (which is rare), and possibly group A strep although that is typically diagnosed via rapid strep test.

Question 28

What type of direct testing would you do in the throat?

Answer 28

direct antigen testing.

Question 29

throat speciman collection: What are the two swabs used for?

Answer 29

one swab for direct antigen testing, one swab for culture

Question 30

How should the throat swab be inserted?

Answer 30

without touching lips, teeth, tongue or cheeks

Question 31

What organisms can colonize a wound without causing disease?

Answer 31

staph aureus, various gram neg rods

Question 32

What method of wound culture collection is preferred?

Answer 32

aspirates are preferred to swabs. Draining wounds can lead to normal skin flora contamination.

Question 33

What are some macroscopic signs of anaerobic cultures?

Answer 33

purulent, large quanities of foul odor, black exudate, necrosis or gangrene.

Question 34

How can you provide speciman integrity to an anaerobic specimen collection?

Answer 34

reducing oxygen tension, expel all air..

Question 35

Describe open wound collections:

Answer 35

1. apply gloves, remove dressing carefully, swab edges with antiseptic. 2. aerobic=open sterile culture tub. anaerobic=swab from anaerobic culture tube. 3. transport immediatley.

Question 36

what is a sinus tract?

Answer 36

drainage system from internal abscess to external site.

Question 37

How should you collect a sinus tract specimen?

Answer 37

it is preferred to get an aspirate from within the tract, however, swabbing may be necessary if that cannot be obtained.

Question 38

With a closed abscess, you always want to…

Answer 38

decontaminate the surface area.

Question 39

What is the leading cause of cellulitis?

Answer 39

GAS (often a group A strep or s. aureus co-infection).

Question 40

Is a wound a screen or comprehensive report?

Answer 40

comprehensive