Maldi-TOF

Question 1

Mass Spectrometry

Answer 1

• analysis of molecules to determine molecular weight

Question 2

MALDI-ToF

Answer 2

Matrix Assisted Laser Desorption Ionization-Time of Flight mass spec

Question 3

m/z

Answer 3

• mass to charge ratio (what is really measured in mass spec)

Question 4

how many approved MALDI-ToF systems?

Answer 4

• 2

Question 5

Strengths of Maldi-ToF

Answer 5

• sensitive: only need a few small colonies
• results in minutes after colonies disappear
• cost: $0.20 for consumables/sample
• automated
• no gram stain required
• works for gram positive, gram negative, yeast, and fungi

Question 6

Steps in MALDI-ToF

Answer 6

• Ionization
• blast sample with a pulse laser
• charged proteins and peptides come off and go through flight tube
• Acceleration through flight tube
• Detection
• Goal: examine proteins and large peptides that are characteristic of pathogenic organisms

Question 7

m/z is proportional to

Answer 7

• time of flight (ToF)

Question 8

How to think of MALDI-ToF

Answer 8

• think of the operation as a drag race between vehicles of different sizes, but all having identical engines
• Start line: orthogonal accelerator
• Finish line: TOF detector
• all ions are pulsed up the flight tube with the same kinetic energy (same engines/horsepower)
• since m= 2E/v^2, smaller vehicles/ions will reach the finish line/detector before larger ones

Question 9

Overall steps of MALDI-ToF

Answer 9

• colony picking
• smearing
• MALDI plate
• ToF-MS
• MALDI biotyper software
• identification

Question 10

Score value species vs genus MADI-ToF

Answer 10

• species: 2.000-3.000 - high confidence ID - Green
• genus: 1.700-1.999 - Low confidence ID - Yellow
• <1.70 - No identification possible - Red

Question 11

When low confidence or no ID and from direct transfer is there another step?

Answer 11

• yes

Question 12

Resistant bacteria can have _____ peaks

Answer 12

• more

Question 13

total time from urine collection to results for MALDI-ToF?

Answer 13

• 2-3 hours

Question 14

few steps from urine sample to maldi-tof

Answer 14

• collection
• concentrate, desalt, centrifuge
• centrifuge into pellet
• apply sample to MALD-ToF

Question 15

Time to Identification (TTI) with MALDI-ToF vs culture

Answer 15

• 1.45 days earlier

Question 16

Clinical Impact of MALDI-TOF: financial and hospital stays

Answer 16

• MALDI-ToF 2x cheaper to have and maintain in a hospital
• shorter hospital length of stay
• lower cost to patient

Question 17

MALDI-ToF as a Sepsityper

Answer 17

• can have results within 4 hours of a positive blood culture
• time is valuable in sepsis
• treatment fast
• use a blood culture, few extra steps before plating

Question 18

How does malditof categorize the bacteria?

Answer 18

• through peptides and proteins characteristic to specific organisms