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Vincenzo Papa, Cristina Cannatella, Anna Rita Blanco, Marcello Santocono; Netilmicin for antibiotic prophylaxis before cataract surgery. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):283.
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© ARVO (1962-2015); The Authors (2016-present)
The most common source of pathogens in postoperative endophthalmitis is the patient’s own ocular surface flora. Topical applied antibiotics used for a brief preoperative regimen should eradicate conjunctival and eyelid bacteria. A cross-sectional case-only observational study (NCT02124603) was performed to determine the antibiotic susceptibility of the ocular surface bacterial flora isolated from patients undergoing cataract surgery and the effectiveness of topical antibiotic prophylaxis in eliminating preoperative bacteria.
120 consecutive patients scheduled for cataract surgery were enrolled (49 males and 71 females, mean age 72.3±8.4 years). Two weeks before surgery, conjunctival and lid margin cultures were obtained from the eye to be operated. Patients were treated starting 2 days before surgery with a topical broad spectrum antibiotic (0.3% netilmicin,1 drop tid). Cultures were repeated the day of surgery, just before povidone-iodine application. Bacteria were isolated using selective culture media and identified by biochemical tests. In vitro susceptibility for the commercially available topical antibiotics netilmicin (NET), moxifloxacin (MFX), chloramphenicol (CAF), levofloxacin (LFX), tobramycin (TOB), ofloxacin (OFX) and azythromicin (AZY) was determined using the disk susceptibility test. Eradication was defined as the disappearance of identified bacteria after antibiotic treatment. A descriptive analysis was performed.
Among 120 patients, 87 (72.5%) had positive bacterial growth: 32 were positive for lid margin, 14 for conjunctiva and 41 for both. A total of 131 isolates (125 Gram+ and 6 Gram-) were obtained: 92 (70%) were Coagulase-negative staphylococci (CNS). The overall susceptibility rate was: NET 94%, MFX 86%, CAF 74%, LFX 70%, TOB 59%, OFX 57%, AZY 15%. A detailed susceptibility rate for NET is shown in the figure. The 3-days application of NET was able to eradicate 98% and 91% of conjunctival and lid margin isolates, respectively (p<0.001, binomial test).
Despite controversy exists regarding the translation of in vitro data into clinical outcome, our data indicate that NET is the only tested antibiotic with an overall 90-plus percent in vitro susceptibility rate and that a 3-days preoperative course with NET is able to eliminate the majority of bacteria.
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