Changes in drug susceptibility and the quinolone-resistance determining region of Staphylococcus epidermidis after administration of fluoroquinolones
Received 23 February 2009; received in revised form 28 May 2009; accepted 29 May 2009.
Purpose
To evaluate the correlation between changes in the susceptibility of bacteria and mutations in the quinolone-resistance determining region (QRDR) after 3 weeks of continuous fluoroquinolone instillation.
Setting
Miyata Eye Hospital, Miyazaki, Japan.
Methods
In this prospective randomized study, gatifloxacin 0.3% eyedrops or levofloxacin 0.5% eyedrops were administered for 1 week before cataract surgery and for 2 weeks after surgery. Samples were collected from the conjunctival sac before instillation of the antibiotic agent and 14 days after surgery. Susceptibility to the fluoroquinolones and gene mutations in the QRDR of the isolated Staphylococcus epidermidis were analyzed.
Results
The detection rate of S epidermidis was 27% in the gatifloxacin group (n=79 eyes) and 21% in the levofloxacin group (n=73 eyes) before instillation of the antibiotic and 6% and 19%, respectively, 14 days postoperatively. The susceptibility rates of S epidermidis strains to levofloxacin were statistically significantly lower after instillation than before antibiotic instillation, and the number of gene mutations in the QRDR was statistically significantly higher after instillation. There was no difference in the gatifloxacin group between before and after antibiotic instillation. In the 9 eyes in which S epidermidis was detected in samples taken before and after antibiotic instillation, most strains were genetically different from each other between the 2 time points.
Conclusions
Three-week continuous instillation of levofloxacin affected the indigenous bacterial flora in the conjunctival sac, suggesting possible induction of microbial substitution to fluoroquinolone-resistant S epidermidis. However, there was no change with gatifloxacin.
From Miyata Eye Hospital, (Miyanaga, Nejima, Miyai, Miyata), Miyazaki; Department of Ophthalmology and Visual Science (Miyanaga), Tokyo Medical and Dental University Graduate School of Medical and Dental Sciences, Tokyo; Department of Ophthalmology (Ohashi), Ehime University School of Medicine, Ehime; Division of Ophthalmology and Visual Science (Inoue), Faculty of Medicine, Tottori University, Tottori; and Laboratory for Clinical Investigation (Toyokawa) and Department of Infection Control and Prevention (Asari), Osaka University Hospital, Osaka, Japan
ABSTRACT