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J.M. Blondeau, P. Hedlin, S.D. Borsos; The Antimicrobial Activity of Gatifloxcin (GAT) With or Without Benzalkonium Chloride (BAK) Against Ocular Bacterial Pathogens . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4880.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To compare gatifloxacin with and without benzalkonium chloride (BAK) against several ocular pathogens. Methods: Ocular and American Type Culture Collection (ATCC) control strains of Haemophilus influenzae (HI), Streptococcus pneumoniae (SP), Staphylococcus aureus (SA), Pseudomonas aeruginosa (PA) and E. coli (EC) were tested by microbroth dilution against GAT with or without BAK according to the guidelines recommended by the National Committee for Clinical Laboratory Standards (NCCLS) using Mueller–Hinton or Todd–Hewitt broth. Inoculated plates were incubated in ambient atmosphere for 18–20 hours at 35°C and the lowest concentration showing no growth was the MIC. Results: Varying concentrations of BAK were either held constantly or serially diluted along with GAT. MICs (µg/ml) for GAT alone versus with BAK against ATCC strains were as follows for the various organisms tested: SP 0.25 vs <0.001; HI 0.016 vs 0.004–0.008; PA 0.5 vs <0.004; EC <0.004 vs <0.004; SA 0.031–0.063 vs 0.004; For GAT vs GAT with BAK, MICs (µg/ml) against clinical ocular isolates were as follows: SP 0.25–0.5 vs <0.001; HI 0.008–0.016 vs 0.004–0.008. For clinical strains, 83% had at least 1 doubling dilution drop in the MIC in the presence of BAK as compared to SP where 100% of strains had a >7 doubling dilution decline in MICs. Conclusions: The presence of varying concentrations of BAK with GAT resulted in a reduction in MICs of both control strains and clinically ocular bacterial pathogens . BAK has an additive effect when used with GAT in reducing bacterial MICs and this observation may have important clinical implications.
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