Characterization of intrinsic efflux activity of Enterococcus faecalis ATCC29212 by a semi-automated ethidium bromide method.
Enterococcus faecalis is recognized as a multidrug-resistant nosocomial pathogen. The phenotypic basis for this is largely uncharacterized. The intrinsic efflux system of the antibiotic-susceptible E. faecalis ATCC29212 strain was studied using a semi-automated method that assesses accumulation and efflux of the universal efflux pump substrate ethidium bromide (EB). The results show that the intrinsic efflux system of this Enterococcus strain is controlled by energy derived from the catabolism of glucose and the proton concentration of the medium. At pH 5, agents that inhibit efflux pumps in Gram-positive organisms and the proton gradient un-coupler CCCP do not increase accumulation nor inhibit efflux of EB. In contrast, at pH 8, where the proton concentration is 1,000-fold lower, these agents increase accumulation and efflux of EB. These results are relevant to infections produced by E. faecalis and subsequent antibiotic therapy with antibiotics to which the organism is known to be intrinsically resistant.
Spengler
Gabriella
G
Unit of Mycobacteriology, Instituto de Higiene e Medicina Tropical, Faculdade de Ciêncas e Tecnologia, Universidade Nova de Lisboa, Lisboa, Portugal.
Martins
Ana
A
Schelz
Zsuzsanna
Z
Rodrigues
Liliana
L
Aagaard
Lone
L
Martins
Marta
M
Costa
Sofia Santos
SS
Couto
Isabel
I
Viveiros
Miguel
M
Fanning
Séamus
S
Kristiansen
Jette E
JE
Molnar
Joseph
J
Amaral
Leonard
L
D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects; D024901:Drug Resistance, Multiple, Bacterial / Q000187:drug effects* / Q000502:physiology; D013293:Enterococcus faecalis / Q000187:drug effects* / Q000378:metabolism; D004996:Ethidium / Q000378:metabolism / Q000494:pharmacology*; D005947:Glucose / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000378:metabolism*; D008826:Microbial Sensitivity Tests; D012110:Reserpine / Q000494:pharmacology; D013881:Thioridazine / Q000494:pharmacology; D014475:Uncoupling Agents / Q000494:pharmacology
D026901:Membrane Transport Proteins; D014475:Uncoupling Agents; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D012110:Reserpine; D004996:Ethidium; D005947:Glucose; D013881:Thioridazine