Oxalic Acid Method

This is primarily used for laryngeal swabs, but is rather

unreliable in that it does not completely ensure the

destruction of untoward organisms.

The swab is simply left in oxalic acid for

30 minutes, and then smeared on the egg medium.

Trisodium Phosphate Method

This, too, is less preferable than Petroff’s method, because

it needs much longer incubation periods.

An equal quantity of sample and 10% trisodium

phosphate are incubated for 24 hours, after which the

container is centrifuged for 30 minutes and the supernatant

discarded.

The deposit is neutralized with 8% HCl using

bromothymol as indicator.

Other Pathogenic Mycobacteria

M. fortuitum

This bacillus has been isolated from soil and from

suppurative infections in men and animals and also in

Microbiology and Bacteriology 845

glandular infections. It grows rapidly and is not pathogenic

for guinea-pigs.