Table 1.

MICs of various strains as a percentage of WT Y. pestis MIC

Strain genotypea	% mutant MIC/WT MICb
	TET	DOX	CHL	GMC	SMC	KAN	RIF	NAL	NOR	CIP	AMP	TMS	Bile	PMB
WT	100	100	100	100	100	100	100	100	100	100	100	100	100	100
lacZ	100	ND	100	ND	118	100	ND	ND	88	ND	ND	89	100	100
acrAB	10***	8***	18***	50***	49***	40***	34***	36***	NA	NA	35***	29***	<17***	23***
acrAB lacZ::acrAB	95	98	89	107	100	105	ND	103	91	ND	ND	84	100	100
tolC	10***	6***	16***	19***	17***	19***	31**	25***	NA	NA	22***	29***	ND	ND
tolC lacZ::kan	10***	4***	8***	24***	16***	R	ND	24***	NA	NA	ND	25***	<4***	0.1***
tolC::tolC lacZ::kan	100	ND	100	ND	88	ND	ND	ND	86	ND	ND	83	100	100
tolC/acrABc	100 (NS)	77 (NS)	100 (NS)	38***	34***	48 (NS)	91 (NS)	71 (NS)	NA	NA	67 (NS)	100 (NS)	23***	0.4***

^aGenes were deleted and complemented using splicing by overlap extension. In complemented strains, acrAB was inserted into the lacZ gene and tolC was inserted into the original deletion site after lacZ deletion by insertion of a kanamycin resistance gene. Boldface type denotes deletion strains.

^bMICs used to calculate percentages were an average of at least 3 experiments. Abbreviations: AMP, ampicillin; Bile, OxGall; CHL, chloramphenicol; CIP, ciprofloxacin; DOX, doxycycline; GMC, gentamicin; KAN, kanamycin; NAL, nalidixic acid; NOR, norfloxacin; RIF, rifampin; SMC, streptomycin; TET, tetracycline; TMS, trimethoprim-sulfamethoxazole; PMB, polymyxin B; NA, not available (the MIC was below the lowest value of 0.016 μg/ml on the Etest strip by 2 to 6 mm); ND, not determined; R, complete resistance due to kanamycin resistance gene chromosomal integration. Significance is denoted as follows: **, P value of 0.001 to 0.01; ***, P value of <0.001; NS, not significant. Boldface type denotes results for deletion strains.

^ctolC MIC as a percentage of the acrAB MIC.