Open AccessA Dose-Response Study of Antibiotic Resistance in Pseudomonas aeruginosa Biofilms
Author(s) -
Alexei Brooun,
Songhua Liu,
Kim Lewis
Publication year - 2000
Publication title -
antimicrobial agents and chemotherapy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.07
H-Index - 259
eISSN - 1070-6283
pISSN - 0066-4804
DOI - 10.1128/aac.44.3.640-646.2000
Subject(s) - pseudomonas aeruginosa , biofilm , microbiology and biotechnology , tobramycin , efflux , ciprofloxacin , antibiotic resistance , antibiotics , biology , multiple drug resistance , pseudomonadaceae , ofloxacin , bacteria , chemistry , gentamicin , biochemistry , genetics
Bacterial biofilms show enormous levels of antibiotic resistance, but little is known about the underlying molecular mechanisms. Multidrug resistance pumps (MDRs) are responsible for the extrusion of chemically unrelated antimicrobials from the bacterial cell. Contribution of the MDR-mediated efflux to antibiotic resistance ofPseudomonas aeruginosa biofilms was examined by using strains overexpressing and lacking the MexAB-OprM pump. Resistance ofP. aeruginosa biofilms to ofloxacin was dependent on the expression of MexAB-OprM but only in the low concentration range. Unexpectedly, biofilm resistance to ciprofloxacin, another substrate of MexAB-OprM, did not depend on the presence of this pump. Dose-dependent killing indicated the presence of a small “superresistant” cell fraction. This fraction was primarily responsible for very high resistance ofP. aeruginosa biofilms to quinolones. Bacterial cells recovered from a biofilm and tested under nongrowing conditions with tobramycin exhibited higher resistance levels than planktonic cells but lower levels than cells of an intact biofilm.