The In vitro Impact of Moxifloxacin and Gatifloxacin Concentration (0.5% v 0.3%) and the Addition of Benzalkonium Chloride on Antibacterial Efficacy Original Reearch Article

Purpoe Varied concentration of moxifloxacin (MOX) and gatifloxacin (GAT) and the addition of 0.005% benzalkonium chloride (BAK) were evaluated for eliminating taphylococcu aureu (A), Peudomona aeruginoa (PA), and coagulae-negative taphylococcu (CN). Deign In vitro laboratory invetigation. Method The time-kill urvival of A, PA, and CN were teted at one, two, three, ix, eight, and 24 hour to: (1) Mueller-Hinton broth, (2) BAK, (3) 0.5% MOX, (4) 0.5% GAT, (5) 0.3% MOX, (6) 0.3% GAT, (7) 0.3% GAT plu BAK, (8) 0.5% MOX plu BAK, (9) 8 μg/ml GAT, and (10) 8 μg/ml MOX. Antibiotic interaction (GAT and BAK) were determined by checkerboard teting. The outcome meaure were (1) time-to-kill, (2) killing-rate, and (3) fractional inhibitory concentration (FIC) indice. Reult MOX and GAT at either 0.5% or 0.3% had equivalent antibacterial effect. BAK alone or the addition of BAK to either antibiotic eliminated A and CN within one hour, wherea 0.3% GAT plu BAK eliminated bacteria fater than 0.5% MOX (P = .016). For PA, BAK alone had no antibacterial effect. The kill rate of MOX and GAT were equivalent. FIC indice indicated that GAT and BAK were indifferent againt A and CN, but antagonitic to PA. Concluion A a preervative, MOX and GAT have equivalent antibacterial activity with imilar killing rate. BAK appear to independently complement GAT for eliminating A and CN, but ha no effect on PA. The in vitro predictive clinical effect due to varied antibiotic concentration and the addition of BAK require confirmatory clinical tudie for validation.