TABLE 3.

Mechanisms of resistance for characterized tet and otr genes^a

Genes
Efflux
tet(A), tet(B), tet(C), tet(D), tet(E), tet(G), tet(H), tet(I), tet(J),  tet(Z), tet(30)btet(31)b
tet(K), tet(L)
otr(B), tcr3c
tetP(A)
tet(V)
tet(Y)d
Ribosomal protection
tet(M), tet(O), tet(S), tet(W)
tet(Q), tet(T)
otr(A), tetP(B),etetc
Emzymatic, tet(X)
Unknownf
tet(U), otr(C)

^aGrouped according to McMurry and Levy (173). 

^bFirst numbered genes (150). 

^cThese genes have not been given new designations (150). 

^dRelatedness to groups 1 to 6 is unclear, since the gene has not been studied extensively. 

^e tetP(B) is not found alone, and tetP(A) and tetP(B) are counted as one gene (164, 273). 

^ftet(U) has been sequenced but does not appear to be related to either efflux or ribosomal protection proteins; otr(C) has not been sequenced (207, 220).