TABLE 1.

Oxygen-dependent killing of leptospires^a

Treatment	Mean bacterial count (105 MPN) ± SD forb:
	Hardjoprajitno	Patoc1
None	4.4 ± 2.1	2.2 ± 2.9
MPO	3.7 ± 3.7	1.3 ± 1.8
H2O2	<0.01	<0.01
MPO + H2O2	<0.01	<0.01

^aLeptospires (strain Hardjoprajitno or Patoc1) were incubated for 30 min at 37°C in MEM (containing 0.126 M chloride), with or without the addition of 0.1 or 1.0 guaiacol unit of MPO (kindly provided by G. Zabucchi) and with different amounts of H₂O₂ as indicated. Incubation mixtures were tested for bacterial viability by using the microdilution test described previously for Borrelia burgdorferi (11), with the statistical elaboration described by Meynell and Meynell (17) for the calculations. As a positive control, E. coli bacteria were treated with MPO, H₂O₂, or MPO + H₂O₂, resulting in levels of viability of 100, 100, and 0%, respectively, as determined by measurements of the number of CFU. Viability counts were performed in triplicate in all cases.

^bMPN, most probable number.