TABLE 2.

Tetracycline MIC values for M. elsdenii strains

M. elsdenii strain(s)a	tet genotypeb	MIC (μg/ml)c
		Tet	Oxytet	Chlortet
24-50; 27-50; 33-54 (LC-1T; B159; T81)	No gene	4-8	8-16	2-8
Fern	tet(O)	64	64	256
25-50; 29-55	tet(W)	32-64	64	64-128
24-51; 27-51; 25-51; 31-55	tet(OW)	64	64-128	128-256
7-11 (2-9)	tet(OWO)-1	128	256	>256
24-53; 27-52; 33-56 (4-13; 7-12; 14-14; 15-5; 19-3; 20-11)	tet(OWO)-2	128	256->256	256->256

^aStrain 7-11 was used as a M. elsdenii tetracycline-resistant reference strain in the assays. Tetracycline MIC values for M. elsdenii strains enclosed by parentheses have been reported previously (26).

^bGenotypes are based on PCR assay results (Fig. 1; Table 1). Strains 27-51 and 25-51 had tet(OW)-1 and tet(OW)-2 genotypes, respectively, as identified by sequence analysis. Strains 25-50 and 29-55 had tet(W)-1 and tet(W)-2 genotypes, respectively.

^cTetracycline (Tet), oxytetracycline (Oxytet), and chlortetracycline (Chlortet) MIC values for NCCLS reference strain Bacteroides fragilis ATCC 25285 (Tc^s) were 2, 8, and 4 μg/ml, respectively. For B. thetaiotaomicron ATCC 29741 (Tc^r), the MIC value of all three antibiotics was 64 μg/ml.