Intrinsic and selected resistance to antibiotics binding the ribosome: analyses of Brucella 23S rrn, L4, L22, EF-Tu1, EF-Tu2, efflux and phylogenetic implications

Table 4 Determination and characterization of erythromycin and clindamycin MICs and molecular characterization of Brucella ery^R mutants.

Brucella ery ^R strains		ERY	ERY + PAβN	CL	CL + PAβN	Loci	Mutation
B. suis	WT	1.5	0.75	8	4	NA
	a	6	6	12	12	-
	b	6	6	12	12	ND
	c	4	6	8	8	-
	d	6	6	12	12	ND
	e	6	6	8	8	ND
B. canis	WT	0.5	0.094	8	0.5	NA
	a	2	0.32	8	1.0	-
	b	2	0.047	6	<0.016	-
	c	3	0.047	8	0.38	-
	d	3	0.047	4	0.125	-
	e	2	0.19	8	3	-
B. neotomae	WT	0.75	0.047	3	0.75	NA
	a	4	0.125	8	0.75	-
	b	3	0.125	6	2	ND
	c	2	0.064	6	1.5	-
	d	6	0.25	6	1.0	L22	6 bp indel, β-loop
	e	2	0.38	4	2	-
Propoise	WT	1.5	0.25	16	3	NA
	a	16	0.75	4	3	L4	G209A; Gly70Asp
	b	>256	>256	>256	>256	23S	A2058G (Ec)
	c	192	1.5	4	3	L4	Δ18aa (54–71)
	d	48	0.38	6	3	L4	G209A; Gly70Asp
	e	128	1.5	4	3	L4	Δ30aa (54–81)
Seal	WT	6	1.5	>256	48	NA
	a	24	12	96	96	-
	b	32	24	>256	>256	-
	c	>256	>256	16	16	L4	C217A; Arg73Ser
	d	128	16	>256	>256	-
	e	128	24	>256	>256	ND
Dolphin	WT	3	0.38	2	0.75	NA
	a	>256	128	1.0	1.5	L4	G209A; Gly70Asp
	b	>256	6	1.5	1.0	L4	C217T; Arg73Cys
	c	>256	192	1.5	1.5	L4	G209A; Gly70Asp
	d	>256	8	2.0	1.0	L4	C217T; Arg73Cys
	e	>256	8	1.5	1.0	ND

Mutants examined were isolates of B. suis biovar 1, B. canis, B. neotomae, and marine porpoise, seal and dolphin strains as per Table 1; WT, wild type; Ery, erythromycin; CL, clindamycin, PAβN, efflux inhibitor L-phenylalanine-L-arginine-β-naphthylamide; -, no mutation identified in any of three ribosomal loci examined; NA, not applicable; ND, sequence not determined.

ISSN: 1471-2180