title: Increased bacterial adherence and biomass in Pseudomonas aeruginosa bacteria exposed to clarithromycin.
abstract: Long-term low-dose macrolides alter response in patients with chronic sessile Pseudomonas aeruginosa colonization. We examined the effect of clarithromycin on 1) adherence of P. aeruginosa cells and 2) biofilm formation. A suspended-coupon continuous-flow biofilm reactor model was used. Adherent P. aeruginosa bacteria were established for 24 h, immediately followed by a 24-h continuous-flow operation (CFO) phase with serial sampling. In addition, the effect of clarithromycin on adherent biomass was assessed quantitatively using a colorimetric assay. Isolates preexposed to clarithromycin were more adherent to the suspended coupons than nonexposed isolates (P=0.021). After 2 h of CFO, a 1.30+/-0.86 log colony-forming unit (CFU)/cm(2) decrease was observed in controls compared with a 0.08+/-0.55 log CFU/cm(2) decrease in isolates exposed to clarithromycin. Furthermore, a concentration-dependent increase in biofilm biomass was observed with the addition of clarithromycin in a standard mucoid P. aeruginosa strain (1-64 microg/mL, P<0.001) and 44 clinical P. aeruginosa strains (2 or 32 microg/mL, P<0.001). Clarithromycin increased bacterial adherence to the suspended coupons, and increased biomass was observed in isolates treated with clarithromycin.
authors.affiliation: University of Houston College of Pharmacy, Department of Clinical Sciences and Administration, Houston, TX 77030, USA. kgarey@uh.edu
authors.forename: Kevin W
authors.initials: KW
authors.lastname: Garey
authors.forename: Quynh P
authors.initials: QP
authors.lastname: Vo
authors.forename: Russell E
authors.initials: RE
authors.lastname: Lewis
authors.forename: Woranuch
authors.initials: W
authors.lastname: Saengcharoen
authors.forename: Mark T
authors.initials: MT
authors.lastname: LaRocco
authors.forename: Vincent H
authors.initials: VH
authors.lastname: Tam
mesh_terms: D000704:Analysis of Variance; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001422:Bacterial Adhesion / Q000187:drug effects* / Q000502:physiology; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D018533:Biomass; D017291:Clarithromycin / Q000494:pharmacology*; D003124:Colorimetry; D004305:Dose-Response Relationship, Drug; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000254:growth & development
chemical_list: D000900:Anti-Bacterial Agents; D017291:Clarithromycin