Rapid ID of Blood Cultures

Question 1

Describe MALDI-TOF

Answer 1

Stands for matrix-assisted laser desorption ionization - time of flight mass spectrometry. It is rapid and cost effective means of identifying bacteria directly from isolated colonies and positive culture bottles based on protein markers. The protein markers measured are highly expressed proteins responsible for housekeeping functions such as 16s ribosomal proteins and transcription/translation factors.

Question 2

What are 2 ways bacteremia can occur?

Answer 2

1) Drainage from the primary focus by the lymphatic system into the vascular system.
2) Direct entry from needles, contaminated intravascular devices or graft material or trauma

Question 3

What are the most common foci or bacteremia and bacterial causes?

Answer 3

Intravascular devices, respiratory and urinary tracts and intra-abdominal infections. S. aureus and E. coli.

Question 4

What is the optimal method for blood culture collection for a person with suspected bacteremia?

Answer 4

1) Disinfect venipuncture site
2) Collect 2 sets: 2 different venipuncture sites, 2 bottles/site
3) Discard first few mLs of blood collected (may contain a skin blood that may contaminate sample with skin bacteria)
4) Collect at least 10 mLs of blood from adults, optimally 20-30 mLs to increase recovery
5) Once collected, the bottles should never be cooled below room temperature