Cord formation in Mycobacterium abscessus

After treating with sodium hydroxide (4%) (Sigma), it was centrifuged at 3000 g under refrigerated conditions (at 4°C). The centrifuged deposit was diluted in 1 ml of sterile distilled water to prepare the bacterial suspension. Two slopes of the Lowenstein–Jensen (L-J) medium (Difco), one containing paranitrobenzoic acid (PNB, Sigma) and 7H9 broth medium were inoculated with 100 μl of the bacterial suspension. A small portion of the bacterial suspension (~20 μl) was examined microscopically, using the Ziehl-Neelsen (ZN) stain, to determine the presence of acid fast bacilli (AFB). The inoculated media were incubated at 37°C in a 5% CO2 incubator. The phenotypic characters of colonies were observed and smears were prepared from cultures grown on all 3 media. Culture isolates were tested by nitrate reductase test.