N-Acetyl-L-Cysteine Sputum Homogenization and Its Mechanism of Action on Isolation of Tubercle Bacilli

¹ Sanatorium Division, Boston City Hospital, Mattapan, Mass. and the Boston University School of Medicine, Infectious Diseases Section

The mechanism of action of acetyl cysteine on the isolation of mycobacteria from sputa was studied. Comparative experiments with 2% sodium hydroxide with and without acetyl cysteine showed that the final positive results are increased by 1.1%. In one-quarter of the positive plates the cultures presented more colonies where acetyl cysteine was used. Viscosimetric tests and pH measurements presented small differences between sputa digested with or without acetyl cysteine. The large increase in positive results obtained by other authors with 2% NaOH and acetyl cysteine compared with 4% NaOH seems to be due to the lower NaOH concentration and not to acetyl cysteine.

As acetyl cysteine does not significantly increase the percentage of positivity and only in a few cases improves liqudection, it is of little practical value as an adjunct substance to sodium hydroxide for sputum digestion.