Remarks

1. Treat the unused specimen and contaminated

containers by immersing in 2% activated glutaraldehyde for at least 2 hours before incineration and

disposal.

2. Good laboratory practices and hazard precautions

must be observed at all times.

3. Discolored or contaminated reagent should not be

used.

4. The reagent containing the phosphate buffer may

appear turbid on prolonged storage at 2–8°C. Gently

warm at 25–30°C before usage to remove such a

appearance.

Effect of centrifugal force on positive smears/cultures

for mycobacteria

Specimen Relative Centrifugal Force (g)

1260 3000 3800

Positive smear 1.8% 4.5% 9.6%

Positive cultures 7.1% 11.2% 11.6%

Correlation of positive

smear/cultures

25% 4 0. % 82%

Thus, proper decontamination and preparation of

specimen is crucial to AFB detection by culture and AFB

staining.

Troubleshooting

Problem: False negative results in LJ media

Possible causes Solutions

1. Mucoid sputum exposed to 2% NaOH Contact time of 2% with sputum should be for only 20 minutes since prolonged

for longer duration period of contact may kill or injure the mycobacteria

2. Saliva used as specimen Thick yellowish green mucoid sputum collected from an early morning deep productive

cough should be used as a specimen

Contd...