Inactivation of Lytic Transglycosylases Increases Susceptibility to Aminoglycosides and Macrolides by Altering the Outer Membrane Permeability of Stenotrophomonas maltophilia.

Stenotrophomonas maltophilia harbors six lytic transglycosylases (LTs): mltA, mltB1, mltB2, mltD1, mltD2, and slt LT deletion increased susceptibility of S. maltophilia to aminoglycosides (AGs) and macrolides, and the underlying mechanisms were investigated. The expression of AG-modifying enzymes and efflux pumps was evaluated by quantitative reverse transcription-PCR (qRT-PCR). Susceptibility to 1-N-phenylnaphthylamine, vancomycin, SDS, and bile salts was measured to assess outer membrane permeability. In conclusion, increased outer membrane permeability contributes to LT deletion-mediated increase in aminoglycoside and macrolide susceptibility.