Gentamicin Can Reduce Incidence of Cataract Postoperative Endophthalmitis

Gentamicin-containing perfusion solution reduces the incidence of postoperative endophthalmitis in eyes following cataract surgery, according to research published in BMC Ophthalmology.

Researchers conducted a retrospective analysis to evaluate the effect of gentamicin in surgical perfusion solution on endophthalmitis incidence after cataract surgery. They compared patients who underwent cataract surgery without (control) or with gentamicin (80 μg/mL) in the surgical perfusion solution and examined endophthalmitis incidence within 30 days of the operation, isolated pathogenic bacteria strains and assessed their antibiotic sensitivity, and tested for drug-resistant genotypes in the pathogens.

The control group included 16,408 patients (47% men and 53% women; average age, 72.8±4.8 years). The gentamicin group included 21,469 patients (47% men and 53% women average age 73±3.9 years).

In the control group, endophthalmitis occurred in 13 patients, with a median onset time of 5 days, translating to an incidence rate of 0.8%. They isolated 13 pathogenic bacterial strains from the patient samples in this group, including 8 strains of Staphylococcus epidermidis, 1 Staphylococcus aureus, 1 Streptococcus pneumoniae, 1 Streptococcus bovis, 1 Enterococcus faecium, and 1 Morganella sp. 

Endophthalmitis occurred in 5 cases in the gentamicin group, with a median onset time of 3 days, translating to an incidence rate significantly lower than that in the control group of 0.2% (P =.016). The team isolated 5 strains of pathogenic bacteria in this group, including 2 strains of Enterococcus faecium, 1 Enterococcus faecalis, 1 Staphylococcus epidermidis, and 1 Staphylococcus aureus. 

The researchers report no significant difference in the proportion of Staphylococcus strains between the groups (P =.326) but found the proportion of Enterococci isolated from samples of the gentamicin group was higher than that in the control group (P =.044). They reported the identification of more gentamicin-sensitive strains than levofloxacin-sensitive strains (P =.018) and detection of an aminoglycoside-inactivating enzyme resistance gene in Enterococcus strains.

“We reported that gentamicin at a safe concentration can reduce the incidence of endophthalmitis after cataract surgery. However, the presence of gentamicin may also serve as selective pressure to provide survival advantages of gentamicin-resistant Enterococci. Therefore, a combination of antibiotics with different modes of actions may minimize the chance of drug resistance,” according to the researchers.

Limitations of the study included the numbers of pathogenic bacteria isolated in both groups and lack of functional confirmation of potential gentamicin-inactivating genes from resistant strains of Enterococci.