KAATZ GW, MOUDGAL VV, SEO SM; Interscience Conference on Antimicrobial Agents and Chemotherapy (42nd : 2002 : San Diego, Calif.).

Abstr Intersci Conf Antimicrob Agents Chemother Intersci Conf Antimicrob Agents Chemother. 2002 Sep 27-30; 42: abstract no. C1-425.

Wayne State University School of Medicine, Detroit, MI.

BACKGROUND: SA may possess several non-NorA MDR efflux transporters. We produced a non-NorA MDR efflux mutant (SA-K2068) with a unique substrate profile that included C8-OMe FQs. METHODS: SA-K2068 was produced by passing SA 8325-4 on a moxifloxacin (MOX)/ethidium bromide (EtBr) gradient plate. MICs were determined +/- reserpine. QRDR regions were sequenced, and norA mRNA was quantitated. MOX uptake and EtBr efflux were measured fluorometrically, and enoxacin (ENOX) uptake radiometrically. Competition for EtBr efflux was assessed by following EtBr loss over time in cells loaded with EtBr plus 10-50 fold molar excesses (ME) of putative competitors. The effect of nigericin (N) and valinomycin (V) on EtBr efflux was determined. RESULTS: Resistance of SA-K2068 to FQs, EtBr, and other putative substrates was reversible by reserpine. No QRDR mutations were found, and norA expression was not altered. Reduced accumulation of MOX and enoxacin, and increased EtBr efflux, was observed and was reversible by CCCP, indicating that the pmf provided the energy for efflux. Tetraphenylphosphonium (TPP; 10-fold ME), MOX, GATI, and ENOX (all at 50-fold ME) interfered with EtBr efflux whereas chloramphenicol and linezolid (50-fold ME) did not. These data differed from those observed with SA-1199B (norA overexpresser), where only TPP at 10-fold ME interfered with EtBr efflux. N and V (2 microM) reduced NorA-mediated efflux of EtBr by ~90%, whereas this concentration caused a 46 and 78% reduction, respectively, in SA-K2068. CONCLUSIONS: These data suggest that the MDR efflux phenotype in SA-K2068 is mediated by a unique non-NorA pump having EtBr, TPP, C8-OMe FQs, and ENOX as substrates, and although more resistant to ionophores than NorA both components of the pmf appear important for the transport process. Competition experiments revealed that TPP was a more favorable substrate than MOX or ENOX.

Publication Types:

• Meeting Abstracts

Keywords:

• Aza Compounds
• Base Sequence
• Cations
• Enoxacin
• Ethidium
• Fluoroquinolones
• Microbial Sensitivity Tests
• Phenotype
• Quinolines
• Staphylococcus aureus
• genetics
• moxifloxacin

Other ID:

• GWAIDS0027078

UI: 102266702

From Meeting Abstracts