Sensitivity of micro-organisms to inactivation

Question 1

What is the definition of disinfection?

Answer 1

Eliminates pathogens

Question 2

What is the definition of sanitisation?

Answer 2

Decreases the amount of micro-organism to a safe level

Question 3

What is the definition of bacteriCIDAL

Answer 3

KILLs the bacteria (no. of bacteria decrease)

Question 4

What is the definition of bacteriSTATIC

Answer 4

INHIBITS the growth of bacteria (no. of bacteria stay constant)

Question 5

When is a microorganism dead?

Answer 5

When it cannot grow and reproduce (in media that would normally support growth)

Question 6

What are the exceptions (counters) to microbial inactivation

Answer 6

Viable but non-culturable bacteria (VBNC)
Some organisms may recover in different environments
Organisms may retain enzymatic activity

(Microbial products can cause damage)

Question 7

How do you calculate the surviving fraction?

Answer 7

N(t)/N(0)

Question 8

How do you calculate the D-value from the inactivation constant?

Answer 8

D = 2.303/k

Question 9

How do you calculate the inactivation factor (IF)?

Answer 9

IF = N(0)/N(t)

IF = 10^(t/D) (t = process time)

Question 10

What is the definition of Minimal inhibitory concentration (MIC)?

Answer 10

Min. conc. of antimicrobial agent needed to inhibit growth under test conditions.

Question 11

What is the definition of Minimum bactericidal concentration (MBC)

Answer 11

Min. conc. of antimicrobial agent needed to kill an organism under test conditions.