Evaluation of ciprofloxacin used as an intranasal antibiotic

The objective of this research was to examine the effects of topical ciprofloxacin on cultured nasal epithelial cells of human origin.

Human nasal epithelial cells were collected from patients who voluntarily donated tissue left over following septorhinoplasty. The samples were from individuals without any indication of rhinosinusitis. An assay that may be employed to investigate toxic effects at the cellular level is MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide). This test reveals where DNA becomes fragmented, the nuclei condense, the outer cell membrane is altered, or the cytoskeleton appears disrupted. The present study employed this technique. Nasal epithelium in cell culture was exposed to ciprofloxacin for 24 hours at a temperature of 37°C, following which the MTT assay was undertaken before examining the cells by confocal microscopy to look for alterations indicating cytotoxicity. Another test of toxicity, the artificial scratch technique, was also used. Cells treated in this way were assessed using a light microscope.

The nasal epithelial cells in culture that were exposed to topical ciprofloxacin for 24 hours were less viable than controls and this result was statistically significant. For this length of exposure, the IC50 was calculated as 1.565 mg/mL. The peak reductions in cellular viability occurred with exposure at a concentration of 1.25 mg/mL and 0.625 mg/mL. These was only a mild decrease in viability at other concentrations, but these results were of statistical significance. The MTT assay and confocal microscopy confirmed this result. Cultured nasal epithelium not exposed to ciprofloxacin (i.e., controls) exhibited a compact morphological appearance when examined with confocal microscopy. The epithelial cells had a regular fusiform boundary, and the nuclei were intact. By contrast, the cultures with exposure to the antibiotic were of decreased size and their outline changed from fusiform to round. The epithelial cells cultures where scratch injury was induced were examined by light microscopy, the extent of closure of the denuded area being assessed after 24 hours. It was noted that the area opened up by the experimental scratch was not closed completely by 24 hours later. This result shows that ciprofloxacin decreases the viability of nasal epithelial cells.

Topical application of ciprofloxacin to the nasal lining is not recommended, since this resulted in decreased cellular viability, cellular shrinking and alteration in outline from fusiform to round in cultured nasal epithelial cells. These changes indicate that topically applied ciprofloxacin is toxic to nasal epithelial cells. The outcomes of this study should be studied and correlated in vivo models.