TABLE 1.

Antimicrobial compounds and conditions inducing VSH-1

Treatment	Antimicrobial concn		hvp38 transcription (fold increase)a	VSH-1 productionb
	μg/ml	μM		DNA	EM
Control (untreated)			1	−	−
Mitomycin C	10	30	260	+	+
Metronidazole	0.5	2.5	720	+	+
	0.05	0.25	50	+	−
	0.005	0.025	7	−	−
Carbadox	0.5	1.9	290	+	+
	0.05	0.19	30	+	+
	0.005	0.019	14	−	−
H2O2		300	100	+	+

^aIncrease in hvp38 transcription over untreated (control) cultures. Levels of hvp38 mRNA in control cultures were arbitrarily standardized to a value of 1. An increase of 5-fold or greater in each of triplicate cultures undergoing a particular treatment was considered significant. The values are mean values for at least two experiments. The following antimicrobials at the indicated concentrations (μg/ml) were not found to stimulate hvp38 transcription: chlortetracycline (5, 10, 50), lincomycin (10, 50, 100), tylosin (500, 1,000), tiamulin (0.02, 0.1), virginiamycin (3), ampicillin (3, 15), ceftriaxone (30), vancomycin (500, 1,000), and florfenicol (2, 10, 20).

^bA culture was considered positive (+) for VSH-1 production if DNA extracted from spirochete cells contained a 7.5-kb band (Fig. 2) or if VSH-1 particles were detected by electron microscopy (EM) (Fig. 3).