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Andreas Neher, MD; Roland Arnitz, MD; Michaela Gstöttner, MD; Dirk Schäfer, PhD; Eva-Maria Kröss; Markus Nagl, MD

Arch Otolaryngol Head Neck Surg. 2008;134(6):615-620.

Objective  To investigate the antimicrobial effect of dexamethasone phosphate, the endogenous antiseptic N-chlorotaurine (NCT), and their combination on ear, nose, and throat microorganisms.

Design  In vitro study.

Subjects  Strains of Staphylococcus aureus, Pseudomonas aeruginosa, Streptococcus milleri, Aspergillus flavus, and Aspergillus fumigatus.

Interventions  Bacterial and fungal strains were cultured with 0.1% dexamethasone with and without a low (0.1%) or high (1%) concentration of NCT. The killing effects of dexamethasone, NCT, and the combination were monitored.

Results  Dexamethasone killed S milleri and A flavus after incubation times of 24 to 48 hours. The low concentration of NCT caused a 90% reduction of S aureus and P aeruginosa within 30 minutes and 99.9% reduction within 50 minutes. The high concentration of NCT reduced viable counts of S aureus and P aeruginosa to the detection limit within 10 minutes. The low-concentration combination (0.1% dexamethasone and 0.1% NCT) showed significant (P < .01) synergistic killing of S aureus with 2- to 3-fold shorter killing times. The high-concentration combination (0.1% dexamethasone and 1% NCT) demonstrated more rapid killing than NCT alone in both S aureus and P aeruginosa.

Conclusions  With short and intermediate exposure times, the combination of dexamethasone and NCT showed significantly stronger antimicrobial effects than treatment with NCT alone. Significant killing of S milleri, A flavus, and A fumigatus was observed after extended exposure to dexamethasone. The combined application of dexamethasone and NCT might be a promising therapeutic option, producing high efficacy with low side effects.

Author Affiliations: Department of Otorhinolaryngology (Drs Neher, Arnitz, and Gstöttner) and Division of Hygiene and Medical Microbiology, Department of Hygiene, Microbiology and Social Medicine (Ms Kröss and Dr Nagl), Innsbruck Medical University, Innsbruck, Austria; and TalkingCells, Medical Clinic III, University Erlangen-Nuremberg, Erlangen, Germany (Dr Schäfer).