RESUMO
Letheen broth and Letheen agar have been investigated for their ability to act as neutralising and recovery media for wild-type and envelope mutants exposed to chlorhexidine diacetate and benzalkonium chloride. At high dilutions, untreated cells of the envelope mutant of Pseudomonas aeruginosa 799/61 were unable to produce colonies on Letheen agar. As a result of various procedures, it was concluded that dilution in Letheen broth and plating in Isosensitest agar was a suitable method for quenching cationic bactericides without harming the test strains, and that the increasing use of Gram-negative bacteria with outer membrane defects means that considerable care may be necessary in selecting media for evaluating bactericidal activity.
Assuntos
Compostos de Benzalcônio/farmacologia , Clorexidina/farmacologia , Escherichia coli/crescimento & desenvolvimento , Bactérias Gram-Negativas/crescimento & desenvolvimento , Pseudomonas aeruginosa/crescimento & desenvolvimento , Meios de Cultura , Escherichia coli/efeitos dos fármacos , Escherichia coli/genética , Bactérias Gram-Negativas/efeitos dos fármacos , Bactérias Gram-Negativas/genética , Mutação , Pseudomonas aeruginosa/efeitos dos fármacos , Pseudomonas aeruginosa/genéticaRESUMO
The effects of chlorhexidine diacetate and benzalkonium chloride on the cell surface of a chlorhexidine-sensitive (Pv 2) and a chlorhexidine-resistant (Pv 67) strain of Providencia stuartii are described. Low concentrations of chlorhexidine diacetate (10 mg/l and upwards) increased the hydrophobicity of Pv 2, whilst having little effect on Pv 67. Both strains were resistant to benzalkonium chloride but a concentration as low as 2 mg/l induced a significant increase in hydrophobicity in Pv 2, with 25-50 mg/l needed to induce a similar type of increase in Pv 67. The possible nature of the resistance is discussed.
Assuntos
Anti-Infecciosos Locais/farmacologia , Clorexidina/farmacologia , Proteus/efeitos dos fármacos , Providencia/efeitos dos fármacos , Compostos de Benzalcônio/farmacologia , Membrana Celular/efeitos dos fármacos , Resistência Microbiana a MedicamentosRESUMO
The sensitivities of Escherichia coli DCO (wild type) and DC2 (envelope mutant) and Pseudomonas aeruginosa 799 (wild-type) and 799/61 (envelope mutant) to preservatives and antibiotics have been determined. The outer membrane appears to play an important role in limiting the penetration of some, but not all, antibacterial agents.
