The pyruvate dehydrogenase complex at the epigenetic crossroads of acetylation and lactylation.

The pyruvate dehydrogenase complex (PDC) is remarkable for its size and structure as well as for its physiological and pathological importance. Its canonical location is in the mitochondrial matrix, where it primes the tricarboxylic acid (TCA) cycle by decarboxylating glycolytically-derived pyruvate to acetyl-CoA. Less well appreciated is its role in helping to shape the epigenetic landscape, from early development throughout mammalian life by its ability to "moonlight" in the nucleus, with major repercussions for human healthspan and lifespan. The PDC's influence on two crucial modifiers of the epigenome, acetylation and lactylation, is the focus of this brief review.

Microbiome and Otic Quinolone Levels Following Tympanoplasty Assessed by Gelatin Sponge Analysis.

OBJECTIVE: To determine if absorbable gelatin sponge (AGS) can be used to assess the posttympanoplasty microbiome and otic antibiotic exposure. STUDY DESIGN: Prospective. SETTING: Tertiary hospital. METHODS: Patients undergoing tympanoplasty were prospectively enrolled. Intraoperatively, AGS was applied to the medial ear canal/tympanic membrane (TM) for 1 minute after canal incision, then saved for analysis. Ear canals were packed with AGS at the end of surgery. Otic ofloxacin was administered until the first postoperative visit, when AGS was collected. Microbial presence was assessed by culture. Ofloxacin levels were assessed by liquid-chromatography mass-spectrometry. RESULTS: Fifty-three patients were included. AGS was collected in 92.9% of patients seen within 21 days compared to 70.8% of those seen at 22 to 35 days. At surgery, AGS yielded bacteria and fungi in 81% and 11%, respectively, including Staphylococcus species (55%) and Pseudomonas species (25%). Postoperatively, AGS yielded bacteria in 71% and fungi in 21% at the meatus, (staphylococci 57% and pseudomonas 25%). TM samples yielded bacteria in 69%, fungi in 6%, staphylococci in 53%, and pseudomonas in 19%. Ofloxacin concentration at the meatus was 248 µg/mL (95% confidence interval [CI]: 119-377) and at the TM was 126 µg/mL (95% CI: 58-194). Ofloxacin-resistant colonies were found in 75% of patients. CONCLUSION: Analysis of AGS is a viable technique for noninvasively studying healing metrics posttympanoplasty, including the microbiome and otic antibiotic exposure. Despite exposure to a high concentration of quinolones, the tympanoplasty wound is far from sterile, which may impact healing outcomes.

Tympanoplasty Healing Outcomes With Use of Postoperative Otic Quinolones.

OBJECTIVE: Tympanoplasty usually results in tympanic membrane perforation (TMP) closure, but healing may be suboptimal (e.g., excess scarring). Factors that have been linked to impaired TM healing have become widely adopted (especially, postoperative use of quinolone ear drops). The aim of this study is to assess the frequency of suboptimal tympanoplasty healing with the use of otic quinolones postoperatively. STUDY DESIGN: Retrospective chart review. SETTING: Tertiary care facility. PATIENTS: One hundred patients undergoing tympanoplasty for TMP. INTERVENTIONS: Tympanoplasty +/- canalplasty. MAIN OUTCOME MEASURES: Healing complications (e.g., granulation tissue, TMP, myringitis, bone exposure, lateralization, anterior blunting, medial canal fibrosis, and canal stenosis) and hearing loss. METHODS: Charts were reviewed for postoperative healing issues and hearing outcomes at 1 to 2 years postoperatively. RESULTS: TMP closure was found in 93.2%, but 34.2% had healing issues at 1 to 2 years postoperatively, with 20.6% having adverse healing outcomes (perforation (6.9%), granulation tissue (6.9%), medial fibrosis (4.1%), and myringitis, bone exposure, and webbing (all 1.4%). Another 13.7% had notable postoperative issues, such as protracted otorrhea (11.0%), otitis externa (9.6%), otitis media (1.4%), and atelectasis (2.7%). No medical, surgical, or patient factors impacted outcomes. Average air-bone gap at 1 to 2 years did not differ between patients with and without healing issues and patients with other postoperative issues ( p = 0.5). CONCLUSIONS: Suboptimal healing is common after tympanoplasty. There may be significant opportunity to improve post-tympanoplasty healing beyond improving the TMP closure rate.

Cytotoxicity of Tetracyclines in Human Tympanic Membrane Fibroblasts.

HYPOTHESIS: Tetracyclines are less cytotoxic to tympanic membrane (TM) fibroblasts than quinolones. BACKGROUND: Use of quinolone ear drops after tympanostomy tube placement and for acute otitis externa has been linked to an increased risk of TM perforation. This has been verified in animal models. Cell culture studies have shown quinolones to be highly toxic to TM fibroblasts. Tetracyclines are a potential alternative to quinolones as they have been used to treat acute otitis externa and are thought to be nontoxic to the inner ear. We aimed to determine if tetracyclines are cytotoxic to TM fibroblasts. METHODS: Human TM fibroblasts were treated with 1:10 dilutions of ofloxacin 0.3%, ciprofloxacin 0.3%, doxycycline 0.3 and 0.5%, minocycline 0.3 and 0.5%, tetracycline 0.3 and 0.5%, or dilute HCl (control), twice within 24 hours or four times within 48 hours. After 2 hours of treatment, cells were returned to growth media. Cells were observed with phase-contrast microscopy until cytotoxicity was measured. RESULTS: Fibroblasts had lower survival with ciprofloxacin 0.3% and doxycycline 0.5% treatment compared with the control after 24 and 48 hours (all p < 0.0001). Fibroblasts treated with minocycline 0.5% had increased cell survival after 24 hours. Minocycline 0.3 and 0.5% showed increased TM fibroblast survival after 48 hours (all p < 0.0001). Phase-contrast images mirrored the cytotoxicity findings. CONCLUSIONS: Tetracyclines are less toxic to cultured TM fibroblasts than ciprofloxacin. Fibroblast tetracycline toxicity is drug and dose specific. Minocycline shows the most promise for possible otic applications in which fibroblast toxicity is a concern.

Effects of quinolone and poloxamer otic suspension on rat tympanic membranes.

OBJECTIVES: Commercial quinolone ear drops (0.3%) delivered twice daily for 10 days cause tympanic membrane perforations (TMPs) in rats. We aimed to evaluate if a single application of 6% quinolone in poloxamer causes TMPs in rats. METHODS: Rats were randomized to 5 groups (10/group), with one ear receiving a single otic instillation of 16% poloxamer 407 or 188 (as found in a commercial otic preparation and a wound dressing), or ofloxacin, ciprofloxacin, or neomycin at 6% in suspension with 16% poloxamer 407. The contralateral ear received saline. Rats were assessed over 42 days. RESULTS: No TMPs were seen in ears treated with saline, poloxamer 407 or 188, or in ears treated with ofloxacin-, ciprofloxacin-, or neomycin-poloxamer suspension. White precipitates were observed on the canal or tympanic membrane of ciprofloxacin and ofloxacin-treated ears. Precipitates were more common in ciprofloxacin-treated ears until day 10 (p < 0.0001 to p = 0.0004). Tympanic membrane surface irregularities, were also observed mostly in the ciprofloxacin-treated ears from day 3-42 (p = 0.03 to p = 0.0033). CONCLUSIONS: Quinolone in poloxamer otic preparations may be a safer therapeutic alternative to conventional quinolone ear drops in ears with intact TMs, particularly those felt to be at risk for developing TMPs.

Efficacy of Topical Epinephrine in Tympanoplasty.

OBJECTIVES/HYPOTHESIS: To compare the hemostatic effects of commonly used concentrations of topical epinephrine in tympanoplasty. STUDY DESIGN: Prospective, randomized, controlled clinical trial. METHODS: Patients undergoing tympanoplasty were randomized to receive topical epinephrine at 1:1,000 or 1:10,000. With the investigators blinded, hemostasis was assessed with a modified Boezaart scale. Vasoconstriction was measured by laser Doppler. Blood pressure and pulse were tracked. RESULTS: Thirty patients, 4 to 84 years old, were studied, with 15 patients per group. Boezaart scores dropped a mean of 67% and 62% with 1:1,000 and 1:10,000, respectively (P = .44). Capillary blood flow decreased a mean of 50.4% and 50.9% with 1:1,000 and 1:10,000, respectively (P = .95). The mean change in heart rate and mean arterial pressure after topical epinephrine exposure were -4.9 and -0.73 beats per minute (P = .15), and -0.60 and -0.73 mmHg (P = .96) for 1:1,000 and 1:10,000 respectively. No adverse events occurred in either group. CONCLUSIONS: Topical epinephrine at 1:10,000 has hemostatic efficacy comparable to 1:1,000 in tympanoplasty. Although both concentrations appear safe, use of topical epinephrine 1:10,000 should be considered over 1:1,000 to minimize the potential for adverse events. LEVEL OF EVIDENCE: 2 Laryngoscope, 131:2319-2322, 2021.

Rat Model of External Auditory Canal Stenosis.

HYPOTHESIS: Circumferential electrocautery injury of the rat external auditory canal (EAC) can induce a reproducible animal model of acquired stenosis. BACKGROUND: Acquired EAC stenosis may occur as a result of chronic inflammation or trauma to the EAC skin and is characterized by narrowing of the EAC, retention of debris, and hearing loss. Treatment is surgery but it is often complicated by restenosis. A reliable and inexpensive animal model of EAC stenosis has not been described. There have been no studies correlating the extent of EAC injury with the extent of stenosis. METHODS: Rats received a 25, 50, or 75% circumferential EAC injury with electrocautery. The extent of resulting stenosis was quantified 21 days following injury. The nature of the injury and healing response was assessed with histology. RESULTS: A 25% circumferential injury led to 4 to 34% stenosis (mean, 13%), 50% injury resulted in 43 to 100% stenosis (mean, 73%), and 75% injury resulted in 94 to 100% stenosis (mean=99%, p < 0.0001). The 50% circumferential injury produced 30 to 75% stenosis in five of eight ears, the remainder had >75% stenosis. Wounded ears showed evidence of intact cartilage and epithelium, with increased thickness of the subepithelial layer and localized fibrosis. CONCLUSIONS: Electrocautery injury in the ventral aspect of the rat EAC resulted in reproducible EAC stenosis. This rat model may be useful in studying therapy to prevent acquired EAC stenosis due to acute injury. The correlation of the extent of injury (circumference) with resulting stenosis may inform clinical management of EAC injuries.

The Effects of Steroids on Survival of Mouse and Human Tympanic Membrane Fibroblasts.

OBJECTIVE: Tympanic membrane (TM) fibroblast cytotoxicity of quinolone ear drops is enhanced by dexamethasone and fluocinolone. Hydrocortisone has not been evaluated. We aimed to assess the effects of these 3 steroids on mouse and human TM fibroblast survival. STUDY DESIGN: In vitro. SETTING: Academic laboratory. SUBJECTS AND METHODS: Mouse and human TM fibroblasts were exposed to hydrocortisone, dexamethasone, or fluocinolone at concentrations in commercial ear drops (1%, 0.1%, or 0.025%, respectively) and at steroid potency equivalents (1%, 0.033%, or 0.0033%, respectively), or dilute ethanol (control), twice within 24 hours or 4 times within 48 hours for 2 hours each time. Cells were observed with phase-contrast microscopy until the cytotoxicity assay was performed. RESULTS: Mouse and human TM fibroblasts treated with any of the steroids had lower survival after 24 and 48 hours compared to control (all P < .0001). After 24 hours, viability of mouse fibroblasts treated with the steroids was not different (P > .05), while treatment with hydrocortisone decreased human TM fibroblast viability (P < .0001). After 48 hours, at concentrations found in ear drops and at equivalent steroid potency, dexamethasone and fluocinolone had similar survival in mouse and human fibroblasts (all P > .05), but hydrocortisone had lower survival in both mouse (P = .02 and P < .0001) and human (P < .0001) fibroblasts. Phase-contrast images mirrored the cytotoxicity findings. CONCLUSION: Steroids found in commercial ear drops reduce survival of mouse and human TM fibroblasts. Hydrocortisone appears to be more cytotoxic than the more potent steroids, dexamethasone and fluocinolone. These findings should be considered when assessing clinical outcomes of ototopical preparations.

Cytotoxicity of Ear Drop Excipients in Human and Mouse Tympanic Membrane Fibroblasts.

OBJECTIVE: Commercial ear drops contain ingredients reported to be inactive. We sought to evaluate such excipients for possible cytotoxicity on human and mouse tympanic membrane (TM) fibroblasts. STUDY DESIGN: Prospective, in vitro. SETTING: Tertiary academic center. SUBJECTS AND METHODS: Mouse and human TM fibroblasts were treated with 1:10 dilutions of benzalkonium chloride (BKC) 0.0025%, 0.006%, or 0.01%; benzyl alcohol 0.9%; polysorbate 80 (PSB) 2.5%; glycerin 2.4%; povidone 0.2%; or water (control), twice within 24 hours or 4 times within 48 hours, for 2 hours each time. Cells were placed back in growth media after the treatments. Cells were observed with phase-contrast microscopy until the cytotoxicity assay was performed. RESULTS: Mouse fibroblasts had lower survival in only the PSB-treated cells compared to the control (P < .0001) after 24 hours. After 48 hours, PSB killed nearly all mouse fibroblasts (P < .0001). BKC decreased fibroblast survival in a dose-dependent manner (P < .001). In human TM fibroblasts, all excipients except povidone and benzyl alcohol after 24 hours and povidone after 48 hours reduced cell survival compared to control (P = .012 to P < .0001). The cytotoxicity of BKC in human TM fibroblasts was also dose dependent (<.0001). PSB was less cytotoxic to human fibroblasts. Phase-contrast images mirrored the cytotoxicity findings. CONCLUSION: Polysorbate 80 and benzalkonium chloride, at concentrations found in commercial ear drops, may be cytotoxic to human and mouse TM fibroblasts. "Inactive" ingredients may need to be considered when evaluating clinical outcomes with commercial ear drops.

Commercial Quinolone Ear Drops Cause Perforations in Intact Rat Tympanic Membranes.

HYPOTHESIS: Commercial quinolone ear drops may promote the development of perforations (TMPs) in intact tympanic membrane (TMs). BACKGROUND: Quinolone ear drops have been associated with TMPs after myringotomy +/- tube placement in a drug-specific manner and potentiation by steroids. METHODS: Rats were randomized to six groups (10/group), with one ear receiving otic instillation of dexamethasone, ofloxacin, ciprofloxacin, ofloxacin + dexamethasone, ciprofloxacin + dexamethasone, or neomycin + polymyxin + hydrocortisone-all commercial formulations and at standard clinical concentrations-and the contralateral ear receiving saline, twice daily for 10 days. TMs were assessed over 42 days. RESULTS: No TMPs were seen in ears treated with saline, dexamethasone, or neomycin. At day 10, TMPs were seen in one of 10 ofloxacin- and three of 10 ciprofloxacin + dexamethasone-treated ears (p = 0.038). At day 14, the ofloxacin TMP healed. In contrast, the three ciprofloxacin + dexamethasone TMPs remained and one new TMP developed in this group. A ciprofloxacin and an ofloxacin + dexamethasone-treated ears also had TMPs (p = 0.023). By day 21, the ofloxacin + dexamethasone TMP and two of four of the ciprofloxacin + dexamethasone TMPs healed but two new TMPs were seen in ciprofloxacin + dexamethasone ears (p = 0.0006). At day 28, 1 of 10 ciprofloxacin and 4 of 10 ciprofloxacin + dexamethasone-treated ears had TMPs (p = 0.0006). By day 35, only one ciprofloxacin + dexamethasone had TMP (p = 0.42). All TMPS were healed at day 42. CONCLUSIONS: Application of commercial quinolone ear drops can cause TMPs in intact TMs. This effect appears to be drug-specific and potentiated by steroids.

Microbiome Analysis of Cholesteatoma by Gene Sequencing.

OBJECTIVE: To compare the microbial flora of cholesteatoma and normal middle ears using gene-based sequencing analysis. STUDY DESIGN: Controlled ex vivo human study. SETTING: Academic, tertiary medical center. SUBJECTS AND METHODS: Brush, swab, and tissue samples were each taken from cholesteatoma matrix and uninvolved tissue in patients with previously untreated, acquired cholesteatoma (n = 19) or middle ear mucosa from patients undergoing cochlear implantation with no history of cholesteatoma or previous middle ear surgery (control; n = 12). DNA was isolated from specimens then 16S rRNA gene sequencing was performed. RESULTS: There was no difference in microbial yield between the sampling methods. Cholesteatoma specimens had lower relative abundance of 14 bacterial species compared with controls including Acidovorax sp., Bacillus sp., Masillia sp., Moraxella osloensis, Phenylobacterium conjunctum, Sphingomonas sp., and Staphylococcus epidermidis (all p < 0.05). Alternaria sp. were present on nearly all the specimens. Alternaria sp. and Cladosporium herbarum (both p ≤ 0.05) were lower in the cholesteatoma compared with control group. There was no difference in the relative abundance of any bacteria or fungi between the cholesteatoma matrix and uninvolved middle ear mucosa. CONCLUSIONS: Microbiome of cholesteatoma matrix is largely similar to adjacent mucosa. This differs from healthy ears. Further study is needed to understand if middle ear microbiome may impact cholesteatoma pathogenesis or treatment.

Prevention of Chlorhexidine Ototoxicity With Poloxamer in Rats.

OBJECTIVE: Skin preparations, like chlorhexidine, are toxic to the inner ear, preventing their use as a preoperative skin disinfectant in the presence of a nonintact eardrum (e.g., perforation or tube). We aimed to determine if a poloxamer gel applied over perforated eardrums could prevent chlorhexidine ototoxicity. STUDY DESIGN: Controlled, in vivo. SETTING: Academic research laboratory. SUBJECTS AND METHODS: Bilateral myringotomies were performed on 20 Sprague-Dawley rats. Half had poloxamer placed over both eardrums before treatment. All rats had chlorhexidine instilled in one ear and saline in the other. Auditory brainstem response thresholds were measured before and 2- and 4-weeks posttreatment. Cochlear hair cell damage was assessed using scanning electron microscopy. RESULTS: Ears with chlorhexidine without poloxamer had significant hearing loss, 37 to 50 dB worse than the other three ear treatments at 2 and 4 weeks posttreatment, at all tested frequencies (4, 18, 16, and 24 kHz; all p < 0.0001). No significant hearing loss was observed in ears that were treated with poloxamer and chlorhexidine (-2 to 8 dB) and the results were not different from the ears that received saline, with or without poloxamer (-2.5 to 8 dB and 5-17 dB; p > 0.05). Electron microscopy showed far more outer hair cell damage in the no poloxamer + chlorhexidine ears compared with the other three treatments. CONCLUSION: The use of a poloxamer barrier may be an effective approach to prevent ototoxicity before chlorhexidine disinfection of the ear with a nonintact tympanic membrane.

Effects of Common Ear Drops on Tympanic Membrane Healing in Rats.

Objective Ciprofloxacin + dexamethasone ear drops have been associated with higher rates of tympanic membrane perforations than ofloxacin. This was thought to be an effect of the steroid; however, ciprofloxacin (sans steroid) has been found to be more toxic to tympanic membrane fibroblasts than ofloxacin in vitro. This study aimed to compare the effect of these agents on tympanic membrane healing in vivo. Study Design Controlled animal study. Setting Academic research laboratory. Methods Perforations were created in 54 rats with a carbon dioxide laser. Rats were randomized to 6 groups (9/group), with 1 ear receiving ofloxacin, ciprofloxacin, dexamethasone, ofloxacin + dexamethasone, ciprofloxacin + dexamethasone, or neomycin, and the contralateral ear receiving saline twice daily for 10 days. Healing was assessed over 40 days. Results Ofloxacin did not delay healing relative to saline. All other treatments delayed healing relative to ofloxacin at day 10 ( P < .0001). Dexamethasone and ofloxacin + dexamethasone delayed healing up to day 14 ( P < .0001). Neomycin and ciprofloxacin + dexamethasone further delayed healing up to day 28 ( P = .009) and day 35 ( P = .043), respectively. All eardrums healed by day 10 with ofloxacin, day 20 with ciprofloxacin, day 28 for dexamethasone, and day 35 for ofloxacin + dexamethasone. At day 40, 2 of 9 ciprofloxacin + dexamethasone-treated eardrums had not healed. All saline-treated eardrums in the ofloxacin, ciprofloxacin, dexamethasone, and ofloxacin + dexamethasone groups were healed by day 14, but this was delayed to day 20 in the ciprofloxacin + dexamethasone group ( P = .007). Conclusions Ototopical quinolones delay rat tympanic membrane healing in a drug-specific manner, with ciprofloxacin having a greater impact than ofloxacin. This effect is potentiated by steroids.

Cytotoxicity of Ciprofloxacin and Steroids in Mouse Tympanic Membrane Fibroblasts.

Objective Ciprofloxacin, commonly given as eardrops, has been shown to adversely affect tympanic membrane fibroblasts. Dexamethasone potentiates this effect. A newly available eardrop contains ciprofloxacin and fluocinolone, a more potent steroid. We evaluated the cytotoxic effects of this preparation on mouse tympanic membrane fibroblasts. Study Design Prospective, in vitro. Setting Academic laboratory. Subjects and Methods In experiment 1, fibroblasts were exposed to 1:10 dilutions of commercially available 0.3% ofloxacin, 0.3% ciprofloxacin, 0.3% ciprofloxacin + 0.1% dexamethasone, 0.3% ciprofloxacin + 0.025% fluocinolone, or dilute hydrochloric acid (control), twice within 24 hours. In experiment 2, cells were also treated with the dilutions of the pure form of dexamethasone 0.1% or fluocinolone 0.025%, alone and in combination with ofloxacin or ciprofloxacin. Cells were exposed to the solutions for 2 hours each time and were placed back in growth media after the treatments. Cells were observed with phase-contrast microscope until the cytotoxicity assay was performed. Results Survival of fibroblasts treated with ofloxacin was not different from the control. Fibroblasts treated with ciprofloxacin, ciprofloxacin + dexamethasone, or ciprofloxacin + fluocinolone had much lower survival (all P < .0001). Cells treated with ciprofloxacin + fluocinolone had lower survival than ciprofloxacin ( P < .0001) and ciprofloxacin + dexamethasone ( P = .0001). Steroids alone also decreased fibroblast survival compared to control ( P < .0001). The combination of dexamethasone or fluocinolone with ciprofloxacin, but not ofloxacin, further decreased fibroblast survival ( P < .0001). Phase-contrast images mirrored the cytotoxicity findings. Conclusion Tympanic membrane fibroblast cytotoxicity of ciprofloxacin is potentiated by corticosteroids. This effect may be deleterious when treating a healing perforation but beneficial when treating granulation tissue on the tympanic membrane.

Evaluation of Mitoquinone for Protecting Against Amikacin-Induced Ototoxicity in Guinea Pigs.

HYPOTHESIS: Mitoquinone (MitoQ) attenuates amikacin ototoxicity in guinea pigs. BACKGROUND: MitoQ, a mitochondria-targeted derivative of the antioxidant ubiquinone, has improved bioavailability and demonstrated safety in humans. Thus, MitoQ is a promising therapeutic approach for protecting against amikacin-induced ototoxicity. METHODS: Both oral and subcutaneous administrations of MitoQ were tested. Amikacin-treated guinea pigs (n = 12-18 per group) received water alone (control) or MitoQ 30 mg/l-supplemented drinking water; or injected subcutaneously with 3 to 5 mg/kg MitoQ or saline (control). Auditory brainstem responses and distortion product otoacoustic emissions were measured before MitoQ or control solution administration and after amikacin injections. Cochlear hair cell damage was assessed using scanning electron microscopy and Western blotting. RESULTS: With oral administration, animals that received 30 mg/l MitoQ had better hearing than controls at only 24 kHz at 3-week (p = 0.017) and 6-week (p = 0.027) post-amikacin. With subcutaneous administration, MitoQ-injected guinea pigs had better hearing than controls at only 24 kHz, 2-week post-amikacin (p = 0.013). Distortion product otoacoustic emission (DPOAE) amplitudes were decreased after amikacin injections, but were not different between treatments (p > 0.05). Electron microscopy showed minor difference in outer hair cell loss between treatments. Western blotting demonstrated limited attenuation of oxidative stress in the cochlea of MitoQ-supplemented guinea pigs. CONCLUSIONS: Oral or subcutaneous MitoQ provided limited protection against amikacin-induced hearing loss and cochlear damage in guinea pigs. Other strategies for attenuating aminoglycoside-induced ototoxicity should be explored.

Efficacy of common reagents for killing ticks in the ear canal.

OBJECTIVE: To determine if widely available solutions can effectively kill ticks that may be found in the human ear canal. METHODS: This study was prospective, controlled and blinded animal study. Lone star ticks (Amblyomma americanum), both nymphal and adult, were submerged in one of four preparations (acetone, isopropyl alcohol 70%, ethanol 95%, or 4% lidocaine) in test tubes (n = 20 per group) for 20 minutes. Ticks were agitated by intermittent probing. Activity of the nymphal ticks was directly observed while those of the adult ticks was video-recorded during the exposure period. Two blinded investigators viewed the videos of adult ticks and during the exposure period to determine the time until death (ie, movement cessation). Mortality was assessed immediately after exposure, and confirmed 24 and 48 hours after exposure. RESULTS: Acetone killed ticks most rapidly (nymph mean time = 185.1 s; adult mean time = 562.9 s). Isopropyl alcohol 70% (nymphs, 328.9 s; adults, 1128.4 s) and ethanol 95% (nymphs, 294 s; adults, 1129.4 s) took longer to kill the ticks. All ticks treated with 4% lidocaine survived. These differences were significant (nymphs, P < .0001; adults, P < .0001). CONCLUSIONS: Acetone was the fastest acting and most effective reagent, followed by ethanol and isopropyl alcohol. These solutions may prove useful in otoacariasis with an intact tympanic membrane. LEVEL OF EVIDENCE: N/A.

Mitochondria-Targeted Antioxidant Mitoquinone Reduces Cisplatin-Induced Ototoxicity in Guinea Pigs.

Objective To determine if mitoquinone (MitoQ) attenuates cisplatin-induced hearing loss in guinea pigs. Study Design Prospective and controlled animal study. Setting Academic, tertiary medical center. Subjects and Methods Guinea pigs were injected subcutaneously with either 5 mg/kg MitoQ (n = 9) or normal saline (control, n = 9) for 7 days and 1 hour before receiving a single dose of 10 mg/kg cisplatin. Auditory brainstem response thresholds were measured before MitoQ or saline administration and 3 to 4 days after cisplatin administration. Results Auditory brainstem response threshold shifts after cisplatin treatment were smaller by 28 to 47 dB in guinea pigs injected with MitoQ compared with those in the control group at all tested frequencies (4, 8, 16, and 24 kHz, P = .0002 to .04). Scanning electron microscopy of cochlear hair cells showed less outer hair cell loss and damage in the MitoQ group. Conclusion MitoQ reduced cisplatin-induced hearing loss in guinea pigs. MitoQ appears worthy of further investigation as a means of preventing cisplatin ototoxicity in humans.

Microflora of Retained Intracochlear Electrodes from Infected Cochlear Implants.

Objectives Cochlear implant infections may be refractory to medical management and require device removal with subsequent reimplantation. During device removal, the intracochlear electrode array is commonly left in place to prevent obliteration of the cochlear lumen. If the electrode is colonized with pathogens, this risks contaminating the replacement implant. In this study, we compare the microorganisms detected on infected cochlear implants against those on the retained electrode using culture and microbial gene-sequencing techniques. Study Design Prospective single-cohort study. Setting Tertiary medical center. Subjects and Methods Six patients with refractory cochlear implant infections had the receiver-stimulator and extracochlear electrode removed to facilitate treatment of the infection. The intracochlear electrode was removed at (delayed) reimplantation. Implant specimens were analyzed by microbial culture and 16S DNA gene sequencing. Results Staphylococcus aureus was the organism most commonly identified. None of the 6 patients' intracochlear electrodes yielded microbes by culture. Two intracochlear electrodes revealed bacterial species, and 1 revealed fungal species by gene sequencing. There was no correlation between the microbes on the infected extracochlear implants and the retained intracochlear electrodes. All subjects underwent reimplantation after resolution of their infections. One of 6 subjects developed a second infection after reimplantation, with S aureus in the primary and secondary infections. Conclusions The intracochlear electrodes of infected cochlear implants carry a low microbial burden. Preserving intracochlear electrodes upon removal of infected cochlear implants appears to carry a low risk of contaminating a replacement cochlear implant.

Collagen and α-Tubulin of Mouse Tympanic Membrane Fibroblasts Treated with Quinolones and Aminoglycosides.

Objective To assess collagen and α-tubulin levels of mouse tympanic membrane fibroblasts treated with quinolone and aminoglycoside antibiotics at concentrations found in eardrops. Study Design Prospective controlled cell culture study. Setting Academic tertiary medical center. Subjects Mouse tympanic membrane fibroblasts. Methods In experiment 1, fibroblasts were treated with the following for 24 or 48 hours: phosphate-buffered saline (negative control), dilute hydrochloric acid (positive control), 0.5% gatifloxacin, or commercially available 0.3% ciprofloxacin, 0.3% ciprofloxacin + 0.1% dexamethasone, 0.3% ofloxacin, 0.5% moxifloxacin, 0.3% gentamicin, or 3.5 mg/mL of neomycin + polymyxin B sulfate + hydrocortisone. In experiment 2, cells were treated with the pure form of gatifloxacin, gentamicin, ofloxacin, or ciprofloxacin. Cells were observed with phase-contrast microscope until harvested. Proteins were extracted for Western blotting with antibodies against collagen α1 type I (collagen 1A1) and α-tubulin, and for densitometry to quantify levels. Results Collagen and tubulin levels in fibroblasts treated with ofloxacin, moxifloxacin, gatifloxacin, or gentamicin for 24 hours were not different from the saline control. Fibroblasts treated with neomycin + polymyxin B + hydrocortisone, ciprofloxacin + dexamethasone, or ciprofloxacin for 24 hours had lower collagen 1A1 and α-tubulin levels (all P < .001) than the negative control. After 48 hours, fibroblasts treated with neomycin + polymyxin B sulfate + hydrocortisone, ciprofloxacin + dexamethasone, ciprofloxacin, or moxifloxacin had lower collagen 1A1 ( P ≤ .007) and α-tubulin ( P < .0001; except ciprofloxacin, P = .033) as compared with control. In experiment 2, only cells treated with ciprofloxacin had lower collagen 1A1 and α-tubulin levels and cell viability (all P < .0001) than control. Cytotoxicity assay and phase-contrast images mirrored the protein findings. Conclusion The adverse impact of topical antibiotic exposure on tympanic membrane collagen and tubulin protein levels is drug specific. This may be important for selection of ototopical therapy.