In vitro toxicity of netilmicin and ofloxacin on corneal epithelial cells

To evaluate the in vitro cytotoxic effect of the aminoglycoside antibiotic netilmicin on rabbit corneal epithelial cells (SIRC) compared with ofloxacin, a commonly used fluoroquinolone ocular antibiotic.

SIRC cell cultures were incubated for 8 to 72 h in the presence and absence of netilmicin (1.5, 3, and 6 mg/mL) and equal concentrations of ofloxacin. Cell viability in treated and untreated SIRC cells was measured by both neutral red and MTT colorimetric assays at 8, 24, and 72 h, whereas changes in cell morphology were examined at 8, 24, 48, and 72 hours by the use of phase-contrast microscopy.

Netilmicin, at all tested concentrations, failed to alter SIRC cell viability or morphology. In contrast, all concentrations of ofloxacin caused statistically significant dose- and time-dependent reductions in cell viability even after 8 h. After 72 h there was complete loss of cell viability. Morphologic examination of SIRC cells after 8 h of incubation with ofloxacin revealed that the fluoroquinolone antibiotic, at all concentrations, produced large numbers of dead cells, compromised intercellular contacts, and altered general morphology. After 48 h the cell monolayer was observed to be completely destroyed.

Netilmicin, at the concentrations used, is an antibiotic devoid of obvious cellular toxicity and may also be considered as a suitable first-choice drug in the treatment of those pathologies that compromise the integrity of the ocular surface.