In eyes injected with prophylactic cefuroxime prior to cataract surgery, cases of endophthalmitis were related to drug resistance, according to a study published in the American Journal of Ophthalmology. This finding was compared with data showing that moxifloxacin-related endophthalmitis was associated with greater anterior chamber volume (ACV).
The key finding of the study was that all of the culture-positive cefuroxime cases demonstrated systemic-level resistance to the drug, investigators report.
The team reviewed 216,141 phacoemulsification surgeries performed between 2014 to 2019 and found 34 cases of endophthalmitis, including 13 eyes injected with cefuroxime, 19 with 0.1 mL of moxifloxacin 0.1%, 1 eye with 0.5 mL moxifloxacin 0.1%, and 1 eye with 1 mL moxifloxacin 0.1%. The group injected with moxifloxacin experienced an infection rate of .02% while the cefuroxime group had an infection rate of .013% (relative risk 1.62 with 95% confidence interval (CI) 0.82-3.20, P =.16).
In 14 of the 33 lab-tested cases, an organism was identified. Four of the 5 eyes injected with cefuroxime that were culture positive were cefuroxime resistant (2 Enterococcus, 1 Pseudomonas, 1 coagulase-negative Staphylococcus). Six of the 8 cases injected with 0.1 mL moxifloxacin and with a subsequent antibiogram were sensitive to drug (4 Streptococcus, 2 Staphylococcus aureus) and 1 was resistant (Enterococcus). One eye injected with 1 mL moxifloxacin resulted in infection with Streptococcus sensitive to the drug.
Compared with endophthalmitis-affected eyes from the cefuroxime group, those injected with 0.1 mL moxifloxacin had a greater mean preoperative anterior chamber depth (ACD, P =.03) and greater calculated pseudophakic ACV (P =.07). However, patients who developed endophthalmitis after receiving the ≥0.5 mL moxifloxacin had larger mean ACD (P =.009) and ACV (P =.002) than those who received the 0.1 mL moxifloxacin.
“Two explanations may account for this observation in moxifloxacin eyes: either bacteria entered the eye after the clearance of the drug from the anterior chamber or an insufficient dose of moxifloxacin was delivered to kill bacteria already present,” the researchers said, noting that the absence of sensitive endophthalmitis-causing bacteria reported in cefuroxime eyes lends more credibility to the latter explanation.
Limitations of the study include the reservoir for drug at the conclusion of surgery possibly being higher than estimated due to the elasticity and bowing back of the posterior capsule during inflation. Analysis of pseudophakic ACD and ACV in study eyes was also limited to indirect calculations rather than direct measurement since the study was retrospective.
The conclusion advocates for further study to determine “the optimal dose and concentration of moxifloxacin to prevent endophthalmitis following cataract surgery while avoiding toxicity to ocular structures.”
Shorstein NH, Liu L, Carolan JA, Herrinton L. Endophthalmitis prophylaxis failures in patients injected with intracameral antibiotic during cataract surgery. Am J Ophthalmol. Published online February 8, 2021. doi: 10.1016/j.ajo.2021.02.007