RESISTANCE OF VEILLONELLA TO HYDROSOLUBLE PRISTINAMYCINS - A POSSIBLEOUTER-MEMBRANE BARRIER EFFECT

An in vitro study on 25 Veillonella strains showed a consistent clinda mycin susceptibility with resistance to erythromycin and to the hydros oluble pristinamycins, quinupristin and dalfopristin and its 30:70 com bination, the synergistin RP59500. Double erythromycin-clindamycin dis k tests did not show any inducible resistance pattern. The addition of 10 or 50 mu g/mL of polymyxin B nonapeptide, an outer membrane permea bilizing agent, consistently reduced quinupristin and dalfopristin MIC s in most strains. This result suggests that the Veillonella outer mem brane may act as a permeability barrier to these antibiotics, as in th e case of other Gram-negative bacteria.