Blood & Cardiovascular

Question 1

Specimen volume

Answer 1

Adults: 10-20mL (1:5 ratio blood:medium). Can be up to 30mL
Children: 1-5mL(use pediatric bottle). Children have higher numbers of organism in bloodstreamm

Question 2

Media/Bottle

Answer 2

• High nutrition
• Charcoal or resin to adsorb antimicrobials
• Aerobic (5-10% CO2) or Anaerobic
• Specialty fungal/mycobacterial bottles
• Standard set: 1 aerobic, 1 anaerobic

Question 3

Anticoagulants used in blood culture

Answer 3

• All blood culture contain anticoagulants to inhibit blood clots
• Most effective: SPS (sodium polyanethol sulfonate) –> neutralize lysozyme, inhibit phagocytosis, inactivie antimicrobial, inhibits a part of complements. Can also inhibit some organism
• Don’t use: Heparin, EDTA, citrate as they are toxic to organisms

Question 4

Instrument & Incubation time for blood culture

Answer 4

• Monitoring in automated within 2 hours from withdrawn.

- Held for 5 days

Question 5

Falsely negative

Answer 5

Not enough CO2, too few/much organisms, slow metabolizing, improper media, high WBC count.

Question 6

Falsely positive

Answer 6

Maximize sensitivity
Very high WBC
Drug
Can perform acridine orange stain (to see poorly staining organisms: Campylobacter, Brucella, Francisella, Mycoplasma)
* If true positive –> GS, call caregiver.

Question 7

Subculture from positive blood culture

Answer 7

• GP: CA, SBA
• GN: Add MacConkey
• Mixed: Add selective media (CNA, PEA)
• Anaerobic: Add Brucella agar

Question 8

Presumptive ID

Answer 8

• Direct test from blood culture: coagulase, bile esculin & 6.5%, latex agglutination, bile solubility
• Other: PNA FISH, Microphage, BionaxNOW (Staph. aureus & MRSA)

Question 9

Fungemia

Answer 9

Candica spp.: grow well in media, not in blood culture as lack of O2

Question 10

Quantitative Blood Culture

Answer 10

• Used to determine if the infx is catheter
• Pour plate: 1ml pt’s blood + 10mL Agar
• Compare peripheral & catheter blood culture: > 10x –> catheter
• If a catheter sample goes Pos 4 hrs before peripheral sample –> line infection

Question 11

Common nosocomial bacteremias

Answer 11

• Staph. aureus & coagulase-neg Staph
• Enterococci
• Candida spp
• E. coli
• Klebsiella sp
• Pseudomonas spp
• Enterobacter spp

Question 12

BM infection

Answer 12

• Org cause bacteremia has access to bones can cause osteomyelitis
• Salmonella, Brucella, Coxiella, Histoplasma, Leishmania

Question 13

Lysis Centrifugation

Answer 13

• Blood drawn into Saponin tube to lyse WBCs, RBCs
• Centrifuge –> discard supernatant and plate sediment to solid media
• Pro: rapid recovery
• Cons: high rate of contamination, decrease detection of: S. pneumoniae, H. influenzae, L. monocytogenes, Anaerobic

Question 14

Bacteremia vs Septicemia

Answer 14

• Bacteremia: bacteria in the bloodstream - may not cause infection
• Septicemia: shows clinical signs and symptoms of infection

Question 15

3 types of bacteremia

Answer 15

• Transient: During common events
• Continuous: constant release into the bloodstream
• Intermittent: org released in bursts, cleared and release again

Question 16

Agents of Endocarditis

Answer 16

• Oral flora: Viridians streps.
• Skin flora: Staph. epidermidis, Coagulase-neg Staph, S. aureus
• HACEK: slow growth
• Abiotrophia
• Enterococcus

Question 17

Infection can cause negative endocarditis

Answer 17

• Rare organism (not cultured by standard method): Chlamydia, Coxiella, Bartonella, Brucella,
• Virus
• Fungus: Candida spp., Aspergillus spp., Pseudallescheria
• Inhibited by antibiotics used

Question 18

Recover of fastidious organism

Answer 18

• Serology:
• Alteration to media: Francisella (requires L-cysteine & dextrose)
• Special sub-culture: Campylobacter (micro-aerophillic), Strep.

Question 19

IV catheter-associated infection

Answer 19

Coagulase-neg Staph, S. aureus, GNR, Candida, Corynebacterium