1. If ratio of the growth in antibiotic containing media as

compared to control is less than 0.01 the isolate will be

termed as sensitive.

2. If ratio of the growth in antibiotic containing media as

compared to control is more than 0.01 the isolate will

be termed as resistant.

Example:

No. of colonies on antibiotic

containing media Ratio = _______________________________

 No. of colonies on control media

Sensitive if ratio is less than 0. 01

Resistant if ratio is more than 0.01

Border line if ratio is equal to 0.01

Remarks

1. Discolored, dislodged or contaminated medium

should not be used.

2. Good laboratory practices and hazard precautions

must be observed at all times.

3. Treat the specimen and used slants by immersing in

2% activated glutaraldehyde for at least 2 hours before

incineration and disposal.

Other Markers

Adenosine deaminase, a surrogate marker, for the

diagnosis of tuberculosis has also shown promise. It

is based on the measurement of activity of Adenosine

deaminase, an enzyme produced by lymphocytes. The

test has excellent sensitivity for TB meningitis and for

examining pleural infections.The sensitivity and specificity

is reported well above 90%, the test is easy to perform and

relatively inexpensive.