Stability of dactimicin to aminoglycoside-modifying enzymes.

Dactimicin was active against strains expressing the activities of aminoglycoside acetylating enzymes [AAC(3)-II, III, IV and V, AAC(2'), AAC(6')-I and II], aminoglycoside-nucleotidylating enzymes [ANT(2"), AAD(3")] and aminoglycoside-phosphorylating enzymes [APH(3')-I-II and III], with the exception of AAC(3)-I and one staphylococcal AAC(6')-IV. Apparently this is the first report of one 6'-N-acetylating enzyme which modifies and inactivates dactimicin. The authors' data suggest that the differences in the behaviour of dactimicin, gentamicin and amikacin against the aminoglycoside-resistant strains tested were mainly due to the production of aminoglycoside-modifying enzymes. If the results are summarized, it may be concluded that dactamicin is the most stable to the majority of aminoglycoside-modifying enzymes demonstrated [APH(3'), APH(2"), APH(3"), ANT(2"), AAD(3"), AAC(2') and AAC(6')], with the exception of AAC(3)-I and staphylococcal AAC(6')-IV.