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EW RESIDENTS 66 September 2017 by Brandon Wong, MD, Vivek Patel, MD, and J. Bradley Randleman, MD potential effects this may have on bacterial resistance to antibiotics. Miyanaga et al. reported that 3-week continuous instillation of levofloxa- cin changed the normal bacterial flo- ra and led to higher resistance rates in S. epidermidis through a possible induction of fluoroquinolone resis- tance. 2 Similarly, after a 3-month follow-up, Nejima et al. found a 20% decrease in S. epidermidis suscepti- bility in patients with 1 month of postoperative levofloxacin treatment compared to 1-week postoperative treatment. 3 While these studies indicate short-term alterations of the bacterial environment and antibiot- ics susceptibility, to date there have not been any studies looking at the long-term effects on normal ocular flora after topical antibiotic use. In "Long-term effects of cataract surgery with topical levofloxacin on ocular bacterial flora," Ono et al. conducted a single-center, prospective study evaluating the long-term effects of topical antibi- otics on ocular bacterial flora after cataract surgery. The study looked at 50 patients undergoing cataract surgery who had topical levoflox- acin 1.5% instilled in the eye four times per day from preoperative day 3 to 1 month postop. All patients additionally received 3 days of oral cefcapene pivoxil (third generation cephalosporin) immediately after surgery. Bacterial scrapings from the conjunctival sac were obtained be- fore the start of topical levofloxacin, as well as at 0 (after last levofloxacin treatment), 3, 6, 9, and 12 months after postoperative levofloxacin in- stillation. Aerobic and anaerobic cul- tures were performed on scrapings, and each bacterial isolate underwent minimum inhibitory concentration (MIC) determinations of levofloxa- cin. The authors used mixed-effects models to compare the differences between number of bacterial species pre-surgery and other time points, as well as to compare the geometric mean MICs of levofloxacin on S. epidermidis and P. acnes at each visit pre-surgery. The authors report that all 50 patients completed 6 months and 48 patients completed 1 year of follow-up after last topical levoflox- acin instillation. Prior to administra- tion of levofloxacin, bacteria were isolated from 48 eyes. S. epidermidis (33.3%) and P. acnes (33.3%) were the most common species iso- lated before treatment. After last treatment with topical levofloxa- cin (month 0) the percent of eyes positive for bacterial isolates was significantly decreased (p<0.01); P. acnes was the predominant bacte- rial species detected. Compared to pre-surgery, there was no statistical difference in percent of eyes positive for bacteria 3, 6, 9, or 12 months after last levofloxacin treatment or in the bacterial diversity. The mean geometric MIC for S. epidermidis was significantly higher at 0 months compared to pre-surgery; there were no statistical differences between the initial and other time points. The MIC of P. acnes was not significant- ly different before or after topical levofloxacin. This study demonstrates the reduction of normal ocular flora diversity after extended levofloxa- cin use after cataract surgery as well as the ability of the ocular flora to regenerate after such use. There is a significant increase in the MIC of S. epidermis after topical levofloxacin administration for 1 month, and the MIC was not restored to retreat- ment levels until 6 months after last treatment. These findings not only indicate the potential for the development of antibiotic resistant bacteria (given the higher MIC after 1 month), they also demonstrate the long-term alterations in the micro- bial environment after long-term antibiotic use, which could have a significant impact on the normal flora. Interestingly, there was no observed change in MIC in P. acnes. The authors assert that the differ- ent MIC pattern observed between S. epidermidis and P. acnes could be attributed to differing replicating activity of the bacteria and bacterial location. They suggest the continu- ous turnover of susceptible P. acnes from the meibomian glands, as well as its transient movement through the conjunctival sac without repli- cating, may account for the lack of bacterial resistance seen after extended levofloxacin use. While this particular study did not look at the short-term use of topical antibi- otics, a study done by the same authors evaluated the MIC of S. Review of "Long-term effects of cataract levofloxacin on ocular bacterial flora" Long-term effects of cataract surgery with topical levofloxacin on ocular bacterial flora Takashi Ono, MD, Ryohei Nejima, MD, Takuya Iwasaki, MD, Yosai Mori, MD, Yukari Noguchi, COT, Akiko Yagi, BS, Hideaki Hanaki, PhD, and Kazunori Miyata, MD J Cataract Refract Surg. 2017;43(9). Article in press Purpose: To clarify the long-term effect of topical antibiotics on the ocular bacterial flora after cataract surgery. Setting: Miyata Eye Hospital, Miyazaki, Japan. Design: A single-centered, prospective case series study. Methods: Fifty patients who had cataract surgery between November 2014 and January 2015 were included. Levofloxacin (LVFX; 1.5%) was administered four times per day by topical instillation from preoperative day 3 to 1-month post-operation. The conjunctival sacs of patients were scraped before the procedure and at 0, 3, 6, 9, and 12 months after the last instillation. The samples were cultured and minimum inhibitory concentrations (MICs) of LVFX for Staphylococcus epidermidis and Propionibacterium acnes were evaluated using mixed effects models. Results: Diverse bacterial species, predominantly S. epidermidis and P. acnes, were isolated before the application of topical LVFX. Bacterial diversity was substantially reduced after the final topical LVFX application and subsequently increased after 3 months. However, the geometric mean LVFX MICs for S. epidermidis isolates were still significantly higher at 3 and 6 months than before treatment (p<0.01, p=0.03, respectively) and reached pre-treatment levels at 9 and 12 months after the last application. P. acnes did not show significant changes in geometric mean LVFX MIC over time. Conclusions: The restoration of the bacterial flora required more than 6 months after cataract surgery and topical LVFX. Vivek Patel, MD, USC residency program director Emerging bacterial resistance due to topical antibiotic prophylaxis is an important consideration for cataract surgeons. This month, I invited the USC residents to review this study on the longer-term consequences of drug resistance in this setting, which appears in the September issue of JCRS. —David F. Chang, MD, EyeWorld journal club editor EyeWorld journal club T he normal ocular flora in healthy individuals in- cludes a diverse spectrum of bacteria, including Staphylococcus epidermidis (S. epidermidis) and Propionibacterium acnes (P. acnes), which have previ- ously been identified as important pathogens causing endophthal- mitis following cataract surgery. Preoperative measures to prevent endophthalmitis include routine disinfection of the ocular surface with direct povidone-iodine as well as preoperative antibiotics. In Japan, a recent survey of cataract surgeons revealed 99% of respondents used preoperative topical antibiotics; after cataract surgery 6% used postopera- tive drops for less than 2 weeks, 30% used them for 2–4 weeks, and 63% used postoperative antibiotics for 1 month or more. 1 This prolonged use of antibiotics calls to question the

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