Comparative antimicrobial activities of antiseptic mouthrinses against isogenic planktonic and biofilm forms of Actinobacillus actinomycetemcomitans.
BACKGROUND
Bacteria contained in biofilms have been shown to have a decreased susceptibility to antimicrobial agents compared to those in planktonic form. Thus, in vitro biofilm models have been developed for screening oral antimicrobial formulations in an effort to produce findings more predictive of clinical activity. This study compared the antimicrobial activity of three mouthrinse formulations when tested against isogenic strains of Actinobacillus actinomycetemcomitans (Aa), one of which was a clinical isolate which forms tenacious biofilms in vitro and the other of which was a spontaneous variant which always grows planktonically.


METHODS
Biofilm-forming Aa strains CU1000 and NJ4300, obtained as clinical isolates, and their respective spontaneous planktonic variants, CU1060 and NJ4350, were grown under standard laboratory conditions and exposed for 15 s to either a negative control (phosphate buffered saline [PBS]), an essential-oil containing mouthrinse (Listerine Antiseptic [LA]), an amine fluoride/stannous fluoride-containing mouthrinse (Meridol [M]), or a triclosan and PVM/MA copolymer-containing mouthrinse (Plax [P]). The cells were then washed, serially diluted, plated, and incubated for enumeration of viable bacteria. Colony-forming units (CFU)/ml were log10 transformed and the mouthrinse groups were compared to the PBS group using analysis of variance.


RESULTS
All 3 mouthrinses produced statisically significant 99.99% reductions (p< or =0.0001) in both planktonic strains compared to the PBS control. Effects on the biofilm forms of the organisms were more variable. Exposure to LA produced statistically significant (p< or =0.0001) reductions in strains CU1000 and NJ4300 of 98.20% and 96.47%, respectively, compared to PBS. M and P produced much smaller reductions which were not statistically significant.


CONCLUSIONS
The results of this study, in which antimicrobial mouthrinses were tested against biofilm-forming and planktonic strains of the same organism, provide a clear demonstration of the resistance to antimicrobial agents conferred by biofilm formation and provide additional support for employing tests using biofilms to more accurately assess the relative activities of antiplaque agents in vitro.
Fine
D H
DH
Dental Research Center, New Jersey Dental School, Newark, NJ 07103, USA.
Furgang
D
D
Barnett
M L
ML
D016976:Aggregatibacter actinomycetemcomitans / Q000145:classification / Q000187:drug effects*; D000588:Amines / Q000494:pharmacology; D000704:Analysis of Variance; D000891:Anti-Infective Agents, Local / Q000494:pharmacology*; D001565:Benzoates / Q000494:pharmacology; D018441:Biofilms / Q000187:drug effects*; D002327:Cariostatic Agents / Q000494:pharmacology; D015169:Colony Count, Microbial; D003773:Dental Plaque / Q000382:microbiology / Q000517:prevention & control; D004338:Drug Combinations; D004352:Drug Resistance, Microbial; D006801:Humans; D016014:Linear Models; D008298:Maleates; D009067:Mouthwashes / Q000494:pharmacology*; D009822:Oils, Volatile / Q000494:pharmacology; D014677:Pharmaceutical Vehicles; D011095:Polyethylenes; D012459:Salicylates / Q000494:pharmacology; D012965:Sodium Chloride; D012967:Sodium Dodecyl Sulfate / Q000494:pharmacology; D013729:Terpenes / Q000494:pharmacology; D013997:Time Factors; D014002:Tin Fluorides / Q000494:pharmacology; D014260:Triclosan / Q000494:pharmacology
D000588:Amines; D000891:Anti-Infective Agents, Local; D001565:Benzoates; D002327:Cariostatic Agents; D004338:Drug Combinations; D008298:Maleates; D009067:Mouthwashes; D009822:Oils, Volatile; D014677:Pharmaceutical Vehicles; C070868:Plax; D011095:Polyethylenes; D012459:Salicylates; D013729:Terpenes; D014002:Tin Fluorides; C059813:Meridol; D012967:Sodium Dodecyl Sulfate; D012965:Sodium Chloride; D014260:Triclosan; C057473:Listerine; C043105:poly(methyl vinyl ether-co-maleic anhydride)