TABLE 1.

Effect of exposure to acidified nitrite for 10 or 20 min on the viability of an M. ulcerans culture

Concn of acidified nitrite or citric acid alonea	pH of solution	Viable counts (log10, CFU/ml)b after exposure for the indicated time in medium:
		Without added protein			With protein addedc
		0 min	10 min	20 min	0 min	10 min	20 min
High
Acidified nitrite	3.00	6.5	<2	<2	7.2	<2	<2
Acid alone	3.00	6.5	6.6	6.8	7.2	7.2	6.8
Medium
Acidified nitrite	3.20	6.5	<2	<2	7.2	<2	<2
Acid alone	3.20	6.5	6.9	7.1	7.2	7.2	7.2
Low
Acidified nitrite	3.41	6.5	<2	<2	7.2	<2	<2
Acid alone	3.41	6.5	6.9	6.8	7.2	7.0	7.3

^aHigh concentrations, 1.7 M sodium nitrite and 0.9 M citric acid; medium concentrations, 0.9 M sodium nitrite and 0.4 M citric acid; low concentrations, 0.4 M sodium nitrite and 0.2 M citric acid.

^bMean results after 28 days of incubation. <2, no growth was observed on plates inoculated with 0.1 ml of the 10-times-diluted M. ulcerans suspension.

^cMiddlebrook 7H9 medium contained 5% BSA during exposure to acidified nitrite or citric acid.