The appropriate medical management of methicillin-resistant Staphylococcus aureus in chronic suppurative otitis media

Different Bacteria and their Antibiotic Sensitivity Patterns in Patients of Chronic Otitis Media-Active Mucosal Disease at a Secondary Care Centre in Delhi

Chronic Otitis Media is characterized by distinct bacteriology compared with Acute Otitis Media, with COM being highly likely to harbor multiple bacteria of anaerobic and aerobic types of organisms (Cameron and Hussam K. El-Kashlan, xxx). In some patients, chronic infection with otorrhea will persist despite aggressive medical therapy. With the large number of cases of COM which presents to Sanjay Gandhi Memorial Hospital, and a majority being resistant to the common medications, we decided to undertake this study to have a better understanding of the bacterial epidemiology, the resistance, and what antibiotic to use in such cases. To determine the prevalence of different bacteriological agents and their antibiotic sensitivity pattern in patients of Chronic Otitis Media-Active Mucosal Disease presenting to ENT OPD at Sanjay Gandhi Memorial Hospital, Mangolpuri, Delhi. An observational cross-sectional study of 200 patients. After an initial examination, two sterile cotton swab sticks were introduced to collect pus samples from the medial part of the external auditory canal. The swabs were sent to the microbiology lab for Gram Staining, Culture, and Biochemical Tests, for identification of the different bacteriological agents and their antibiotic sensitivity patterns. Most common organism seen was Pseudomonas aeruginosa, followed by Staphylococcus aureus, Klebsiella pneumoniae, Proteus mirabilis, mixed bacterial growth, and Candida spp. If regular monitoring of bacteriological profile is done in each hospital, this will help us to choose the antibiotics in a better manner and hence prevent the appearance of newer resistant strains.

Outcomes of Mastoidectomy With Antibiotic Catheter Irrigation for Patients With Draining Ventilation Tubes

OBJECTIVES

To evaluate the effectiveness of mastoidectomy with antibiotic catheter irrigation in patients with chronic tympanostomy tube otorrhea.

METHODS

A chart review of adult and pediatric patients with persistent tympanostomy tube otorrhea who had failed outpatient medical management and underwent mastoidectomy with placement of a temporary indwelling catheter for antibiotic instillation was performed. Patients were retrospectively followed for recurrent drainage after 2 months and outcomes were categorized as resolution (0-1 episodes of otorrhea or otitis media with effusion during follow-up), improvement (2-3 episodes), or continued episodic (>3 episodes).

RESULTS

There were 22 patients and 23 operated ears. Median age was 46 years (interquartile range, IQR = 29-65). The median duration of otorrhea from referral was 5.5 months (IQR = 2.8-12). Following surgery, 14 ears had resolution of drainage, 6 had improvement, and 3 had episodic. The observed percentage of resolved/improved ears (87%) was significant (P = .0005, 95% CI = 67.9%-95.5%). Median follow-up time was 25 months (IQR = 12-59). Pre and postoperative pure tone averages improved (difference of medians = -3.3 dB, P = .02) with no significant difference in word recognition scores (P = .68). Methicillin-resistant Staphylococcus aureus was the most common isolated microbe while no growth was most frequently noted on intraoperative cultures.

CONCLUSIONS

Mastoidectomy with antibiotic catheter irrigation may be an effective surgical strategy, and single stage alternative to intravenous antibiotics, for select patients with persistent tube otorrhea who have failed topical and oral antibiotics.

Mapping of audiometric analysis with microbiological findings in patients with chronic suppurative otitis media (CSOM): a neglected clinical manifestation

Otitis media (OM) is an umbrella term for a number of conditions associated with middle ear inflammation. Chronic suppurative otitis media (CSOM), a type of OM, is characterized by long-term middle ear infection with perforated ear drum and otorrhea. The most common outcome associated with it is acquired hearing impairment in infected individuals which ultimately affects their cognitive and scholastic developments. Clinically, CSOM is thought to be a sequel of re-occurring episodes of Acute otitis media (AOM). Pseudomonas aeruginosa and Staphylococcus aureus are found to be the predominant pathogenic isolates in these patients. However, with the emergence of antibiotic resistance amongst these pathogens, the adequate evaluation and treatment of this condition has become more problematic. The disease has also been recognized as one of the neglected tropical clinical manifestations with high prevalence in school-age children, especially in poor or underprivileged countries. Moreover, untreated cases have further worsened the situation by contributing to various life-threatening complications. Thus, effective treatment and surgical strategies, as well as strengthening of hearing care algorithms along with the discovery of novel animal models for advanced clinical research, can jointly help to fight this disease. In this regard, mapping of the audiological analysis with microbiological findings in CSOM patients may help elucidate the frequency that favors growth of specific pathogens. Knowledge about this potential correlation can then support timely detection of the infection, which is perceived as one of the emerging approaches for its management. In addition to these strategies, creating a true sense of awareness among people can also help mitigate this pathological condition by facilitating early identification, prevention, and treatment. This review discusses the incidence, pathogenesis, investigations, complications, and available treatment modalities associated with CSOM.

Evaluation of the current bacteriological profile and antibiotic sensitivity pattern in chronic suppurative otitis media

OBJECTIVE

To determine the current microbiological profile of chronic suppurative otitis media (CSOM), their antimicrobial sensitivity, their resistance pattern to locally available antibiotics and the appropriate antibiotic against isolated microorganisms causing CSOM.

METHODS

This cross-sectional study involved 91 ear swab specimens obtained from patients clinically diagnosed with active CSOM. Swabs were cultured for microbial identification according to a standard protocol. We performed antibiotic susceptibility testing, using the modified Kirby-Bauer disc diffusion method, and the diameter of the inhibition zone was interpreted based Clinical Laboratory Standards Institute guidelines.

RESULTS

Microbial growth was seen in 85 (93.4%) samples, but 6 (6.6%) samples had no growth. Among the samples with growth, 63 (69.2%) were monomicrobial, 13 (14.3%) were polymicrobial, and 9 (9.9%) were of mixed growth with more than three microorganisms. The most common bacteria isolated was Pseudomonas aeruginosa (32.6%) followed by Staphylococcus aureus (16.9%) and Klebsiella spp. (5.6%). The most sensitive antibiotics against P aeruginosa were ceftazidime, meropenem, piperacillin-tazobactam, and cefepime. S aureus showed the highest sensitivity toward rifampin, cefoxitin, and fusidic acid.

CONCLUSIONS

The bacteriological profile of CSOM showed a high prevalence of P aeruginosa, followed by S aureus and Klebsiella spp. with different distributions in different age groups. We observed a declining pattern of their antibiotic sensitivity. It is important to be aware of the current trend of the bacteriological profiles and to revise the antibiotic regime according to both the sensitivity and age groups.Level of Evidence: NA.

In Situ 3D-to-2D Transformation of Manganese-Based Layered Silicates for Tumor-Specific T1-Weighted Magnetic Resonance Imaging with High Signal-to-Noise and Excretability

Recently, Mn(II)-based T₁-weighted magnetic resonance imaging (MRI) contrast agents (CAs) have been explored widely for cancer diagnosis. However, the "always-on" properties and poor excretability of the conventional Mn(II)-based CAs leads to high background signals and unsatisfactory clearance from the body. Here, we report an "in situ three-dimensional to two-dimensional (3D-to-2D) transformation" method to prepare novel excretable 2D manganese-based layered silicates (Mn-LSNs) with extremely high signal-to-noise for tumor-specific MR imaging for the first time. Our observations combined with density functional theory (DFT) calculations reveal that 3D metal (Mn, Fe, Co) oxide nanoparticles are initially formed from the molecular precursor solution and then in situ transform into 2D metal (Mn, Fe, Co)-based layered silicates triggered by the addition of tetraethyl orthosilicate, which provides a time-saving and versatile way to prepare novel 2D silicate nanomaterials. The unique ion-exchangeable capacity and high host layer charge density endow Mn-LSNs with an "ON/OFF" pH/GSH stimuli-activatable T₁ relaxivity with superb high signal-to-noise (640-, 1200-fold for slightly acidic and reductive changes, respectively). Further in vivo MR imaging reveals that Mn-LSNs exhibit a continuously rapid T₁-MRI signal enhancement in tumor tissue and no visible signal enhancement in normal tissue, indicating an excellent tumor-specific imaging. In addition, Mn-LSNs exhibit a rapid excretion from the mouse body in 24 h and invisible organ toxicity, which could help to solve the critical intractable degradation issue of conventional inorganic CAs. Moreover, the tumor microenvironment (pH/GSH/H₂O₂) specific degradability of Mn-LSNs could help to improve the penetration depth of particles into the tumor parenchyma. Developing this novel Mn-LSNs contrast agent, together with the already demonstrated capacity of layered silicates for drug and gene delivery, provides opportunities for future cancer theranostics.

Prevalence and etiological agents for chronic suppurative otitis media in a tertiary hospital in Tanzania

OBJECTIVE

Chronic suppurative otitis media is among the most common otological condition reported in otorhinolaryngology practice commonly attributing to preventable hearing loss. The aim of this study was to determine the prevalence and etiological agents for chronic suppurative otitis media in our department.

RESULTS

A total of 5591 patients were recruited in this study and only 79 (1.4%) had chronic suppurative otitis media. A male preponderance 43 (54.4%) was noted in this study and the left ear (58.2%) was more commonly affected compared to the right ear. Central perforation was the commonest pattern of presentation and was reported in 53% of cases though none had attic perforation. Of the 81 processed ear swabs, microbial growth was seen in majority 80 (98.8%) whilst one sample showed no microbial growth whereas 52.5% had polymicrobial growth. Among the isolates, most were gram negative species accounting for 59.7% while gram positive bacteria accounted for 25.6% and fungi accounted for 14.7%. Most of these isolates were facultative anaerobes. Klebsiella pneumoniae (20.2%) was the commonest isolates while Escherichia coli and Pseudomonas aeruginosa were equally least isolated (10.9%). Tested isolates were most sensitive to Ciprofloxacin, Gentamycin, Ceftriaxone and Amikacin and least sensitive to Amoxicillin/clavulanic acid and Ampicillin.

A microbiome case-control study of recurrent acute otitis media identified potentially protective bacterial genera

Background

Recurrent acute otitis media (rAOM, recurrent ear infection) is a common childhood disease caused by bacteria termed otopathogens, for which current treatments have limited effectiveness. Generic probiotic therapies have shown promise, but seem to lack specificity. We hypothesised that healthy children with no history of AOM carry protective commensal bacteria that could be translated into a specific probiotic therapy to break the cycle of re-infection. We characterised the nasopharyngeal microbiome of these children (controls) in comparison to children with rAOM (cases) to identify potentially protective bacteria. As some children with rAOM do not appear to carry any of the known otopathogens, we also hypothesised that characterisation of the middle ear microbiome could identify novel otopathogens, which may also guide the development of more effective therapies.

Results

Middle ear fluids, middle ear rinses and ear canal swabs from the cases and nasopharyngeal swabs from both groups underwent 16S rRNA gene sequencing. The nasopharyngeal microbiomes of cases and controls were distinct. We observed a significantly higher abundance of Corynebacterium and Dolosigranulum in the nasopharynx of controls. Alloiococcus, Staphylococcus and Turicella were abundant in the middle ear and ear canal of cases, but were uncommon in the nasopharynx of both groups. Gemella and Neisseria were characteristic of the case nasopharynx, but were not prevalent in the middle ear.

Conclusions

Corynebacterium and Dolosigranulum are characteristic of a healthy nasopharyngeal microbiome. Alloiococcus, Staphylococcus and Turicella are possible novel otopathogens, though their rarity in the nasopharynx and prevalence in the ear canal means that their role as normal aural flora cannot be ruled out. Gemella and Neisseria are unlikely to be novel otopathogens as they do not appear to colonise the middle ear in children with rAOM.

Electronic supplementary material

The online version of this article (10.1186/s12866-018-1154-3) contains supplementary material, which is available to authorized users.

Comparative antibacterial activity of topical antiseptic eardrops against methicillin-resistant Staphylococcus aureus and quinolone-resistant Pseudomonas aeruginosa

OBJECTIVE

Aural irrigation using antiseptic solutions can be an effective medical treatment of chronic suppurative otitis media (CSOM) owing to the increasing prevalence of antibiotic-resistant CSOM infections. In the present study, we compared the antimicrobial activities of 100% Burow's solution, 50% Burow's solution, 2% acetic acid, vinegar with water (1:1), and 4% boric acid solution against methicillin-resistant Staphylococcus aureus (MRSA), methicillin-susceptible S. aureus (MSSA), quinolone-resistant Pseudomonas aeruginosa (QRPA), and quinolone-susceptible P. aeruginosa (QSPA) in vitro.

METHODS

We examined the antimicrobial activities of five antiseptic solutions against MRSA, MSSA, QRPA, and QSPA. The antimicrobial activities of the solutions were calculated as a percentage of the surviving microorganisms by dividing the viable count in each antiseptic solution with that in control. The time (D10 value) required for each of the five solutions to inactivate 90% of the microorganism population was also investigated.

RESULTS

Burow's solution exhibited the highest antimicrobial activity and the lowest D10 value against MRSA, MSSA, QRPA, and QSPA, followed by 2% acetic acid, vinegar with water (1:1), and 4% boric acid solution.

CONCLUSION

Our results indicate that Burow's solution has the most potent activity against bacteria including antibiotic-resistant strains. Twofold dilution of the solution is recommended to avoid ototoxicity.

Current concepts in the pathogenesis and treatment of chronic suppurative otitis media

Otitis media (OM) is an inflammation of the middle ear associated with infection. Despite appropriate therapy, acute OM (AOM) can progress to chronic suppurative OM (CSOM) associated with ear drum perforation and purulent discharge. The effusion prevents the middle ear ossicles from properly relaying sound vibrations from the ear drum to the oval window of the inner ear, causing conductive hearing loss. In addition, the inflammatory mediators generated during CSOM can penetrate into the inner ear through the round window. This can cause the loss of hair cells in the cochlea, leading to sensorineural hearing loss. Pseudomonas aeruginosa and Staphylococcus aureus are the most predominant pathogens that cause CSOM. Although the pathogenesis of AOM is well studied, very limited research is available in relation to CSOM. With the emergence of antibiotic resistance as well as the ototoxicity of antibiotics and the potential risks of surgery, there is an urgent need to develop effective therapeutic strategies against CSOM. This warrants understanding the role of host immunity in CSOM and how the bacteria evade these potent immune responses. Understanding the molecular mechanisms leading to CSOM will help in designing novel treatment modalities against the disease and hence preventing the hearing loss.

Role of Acetic Acid Irrigation in Medical Management of Chronic Suppurative Otitis Media: A Comparative Study

Chronic otitis media is persistent and insidious disease. It is one of the most common bacterial infections in the field of otolaryngology having significant economic and individual repercussion. Medical management of chronic suppurative otitis media (CSOM) for dry ear is essential before surgical treatment. The objective is to consider the most appropriate medical treatment modalities for patients of CSOM. To assess results of acetic acid irrigation and topical and systemic antibiotic in CSOM and consider, the most appropriate medical management. This study was conducted prospectively from Nov 2011 to Sep 2013 in 100 patients of CSOM (tubotympanic type). Patient included in the present study were divided in two groups. In one group patients were treated with aural toilet and irrigation with acetic acid and in other group patients were treated with topical and systemic antibiotic. After a follow up period of 3 months duration results were assessed on the basis of absence of discharge, healing of perforation and status of middle ear. Otorrhoea resolution in group treated with acetic acid was 84 % and healing of perforation was noted in 26 % while failure rate of 16 % was noted. In group treated with topical and systemic antibiotic 58 % of patient shows otorrhoea resolution, 14 % achieve healing of perforation and 32 % had failure. Medical management of CSOM without Cholesteatoma by frequent aural cleaning and irrigation using dilute acetic acid can be more desirable choice as compared to the topical and oral antibiotics.

Preparation of levofloxacin thermo-sensitive gel and clinical application in the treatment of suppurative otitis media

CONCLUSION

The levofloxacin thermo-sensitive gel prepared using 17% poloxamer 407 (P407) can successfully treat suppurative otitis media (SOM) through the well-controlled release of levofloxacin targeted against the inflammation.

OBJECTIVE

To evaluate the preparation method and therapeutic effect of levofloxacin thermo-sensitive gel used in the treatment of SOM.

METHODS

The phase inversion temperatures of 16%, 17%, 18%, 19%, and 20% P407 or P407 solution with 3 mg/ml levofloxacin were determined and the one close to 34(°)C was selected as the optimal concentration. Then a model of SOM was induced by injection of 0.1 ml Staphylococcus aureus (1 × 10(8)/L) in the left ear of 32 Sprague Dawley (SD) rats. Normal saline injected in the right ear was used as the control. Then rats were treated with 0.1 ml normal saline (group A), levofloxacin (group B), P407 (group C), and levofloxacin thermo-sensitive gel (group D) (n = 8). The tympanic membranes were evaluated by otoscopy and hematoxylin and eosin (H&E) staining.

RESULTS

The optimal concentration of P407 was 17% and the release of levofloxacin in thermo-sensitive gel followed zero-order kinetics. Levofloxacin thermo-sensitive gel and levofloxacin drops could both alleviate the local inflammation in the first 3 days, but levofloxacin drops could not inhibit the recurrence of SOM, while the levofloxacin gel performed continuous drug delivery into inflammation without recurrence.

Panel 7: Treatment and comparative effectiveness research

BACKGROUND AND OBJECTIVES

Otitis media (OM) is one of the most common reasons for antibiotic treatment in children. Controversies regarding antibiotic treatment for OM have accumulated in the past decade, and there seem to be more dilemmas than certainties. The objectives of this article are to provide the state-of-the art review on achievements in treatment of all different stages of OM, including acute otitis media (AOM), otitis media with effusion (OME), and chronic suppurative otitis media, and to outline the future research areas.

DATA SOURCES

PubMed, Ovid Medline, the Cochrane Database, and Clinical Evidence (BMJ Publishing).

REVIEW METHODS

All types of articles related to OM treatment published in English between January 2007 and June 2011 were identified. A total of 286 articles related to OM treatment were reviewed by the panel members; 114 relevant quality articles were identified and summarized.

RESULTS

New evidence emerged on beneficial results of antibiotic treatment, compared with observation of AOM in young children who were diagnosed based on stringent criteria. In OME, the main results were related to a nonsignificant benefit of adenoidectomy versus tympanostomy tube placement alone in the treatment of chronic OME in younger children. Other modalities of OM treatment were studied and described herein.

CONCLUSIONS AND IMPLICATIONS FOR PRACTICE

Significant progress has been made in advancing the knowledge on the treatment of OM. Areas of potential future research have been identified and outlined.

Minimal inhibitory concentration of natural vinegar and of aluminium acetate-tartrate solution

HYPOTHESIS

Vinegar and aluminium acetate preparations are used for treatment of ear infections. It is instrumental to know the minimal inhibitory concentration to get effective remedies. This study was performed to assess the lowest dilution of vinegar (specified content, 6% acetic acid) and aluminium acetate-tartrate solution (specified content, 1.4% aluminium and 6% acetic acid) to determine the minimum inhibitory concentration against bacteria commonly found in chronic ear infections.

BACKGROUND

Laboratory study on 2 samples of aluminium acetate-tartrate and on 1 sample of natural white wine vinegar on antibacterial effects against Staphylococcus aureus, Staphylococcus epidermidis, Proteus vulgaris, Pseudomonas aeruginosa, and Escherichia coli.

METHODS

Performing of a susceptibility testing-determination of the minimum inhibitory concentration (MIC) with the method of microbouillon dilution (DIN 58940 part 7).

RESULTS

Acetic acid was found to be effective in vitro in concentrations of 0.1% to 0.2% against the tested bacteria; aluminium acetate-tartrate solution was found to be effective in vitro in concentrations of 1.25% to 2.5% against the tested bacteria.

CONCLUSION

Vinegar respectively acetic acid diluted with water and aqueous aluminium acetate-tartrate solution could be effective ototopic preparations caused by one of the tested bacteria. For its effectiveness, an acid pH not higher than 4.5 is essential. Experiments with aluminium acetate-tartrate preparations on animals and clinical trials are required to obtain information about the response rates in ear infections and about any adverse effects.

Unique microbiology of chronically unstable canal wall down tympanomastoid cavities: considerations for surgical revision

OBJECTIVE

To review the microbiology of open tympanomastoid cavities in patients who underwent revision surgery due to chronic instability.

METHODS

This paper describes a retrospective chart review of surgical revision cases of chronically unstable open mastoid cavities. Patient records from 2000 to 2010 were reviewed for the type of organism cultured, antimicrobial resistance and the presence of cholesteatoma.

RESULTS

In total, 121 revision surgical procedures were performed on 101 patients. Seventy-nine procedures involved culture specimen processing, 37 of which were positive. The most commonly cultured organism was Staphylococcus aureus, which was more than twice as common as any other pathogen. The presence of cholesteatoma had no impact on the likelihood of a positive culture or polymicrobial culture. Antimicrobial-resistant pathogens were uncommon.

CONCLUSION

A positive culture was not an overwhelmingly common characteristic of unstable tympanomastoid cavities. Furthermore, antimicrobial resistance did not appear to play an essential role in leading patients towards revision open mastoid surgery.

Layered double hydroxides as efficient drug delivery system of ciprofloxacin in the middle ear: an animal study in rabbits

Chronic otitis media is a common disease often accompanied by recurrent bacterial infections. These may lead to the destruction of the middle ear bones such that prostheses have to be implanted to restore sound transmission. Surface coatings with layered double hydroxides (LDHs) are evaluated here as a possibility for drug delivery systems with convenient advantages such as low cytotoxicity and easy synthesis. Male New Zealand White rabbits were implanted with Bioverit(®) II middle ear prostheses coated with the LDH Mg(4)Al(2)(OH)(12)(SO(4))(2)·6H(2)O impregnated with ciprofloxacin. 12 (group 1) were directly infected with Pseudomonas aeruginosa and another 12 (group 2) 1 week after the implantation. Clinical outcome, blood counts, histological analyses and microbiological examination showed an excellent antimicrobial activity for group 1, whereas this effect was attenuated in animals where infection was performed 1 week after implantation. This is the first study to demonstrate an efficient drug delivery system with an LDH coating on prostheses in the middle ear.

Efficacy of a topical suspension of bacterial antigens for the management of chronic suppurative otitis media

The aim of this study was to compare the efficacy and safety of a topical suspension of bacterial antigens for the management of chronic suppurative otitis media (CSOM). Two-hundred ten patients with CSOM were enrolled in this study. The patients were divided into two numerically equal groups and randomized to receive a topical suspension of bacterial antigens, Lantigen B (group A), or placebo (group B), according to the following protocol: 5 drops thrice a day for 12 consecutive weeks in the external acoustic duct. The topical suspension of bacterial antigens and placebo were administered by identical, anonymous dispensers in order to maintain double-blind conditions. Before, at the end and 3 months, and after the end of the treatment, all patients who entered in the study underwent pure tone audiometry, microscopic examination of ears, microbiological examination of the ear swab, aural suctioning and subjective assessment of symptoms by visual analog scale. In group A, we saw a statistically significant improvement in the different items measured. A topical suspension of bacterial antigens was significantly more effective than placebo in the treatment of CSOM.

MRSA otorrhea: A case series and review of the literature

Methicillin-resistant Staphylococcus aureus (MRSA) has become an increasingly common cause of difficult-to-treat head and neck infections. We report a retrospective analysis of 3 cases of MRSA otorrhea treated in our clinic between 2007 and 2009. Culture analysis of otorrhea isolates revealed MRSA infections with identical drug sensitivities. Treatment success was achieved using combinations of linezolid with gentamicin ear drops for 3 to 4 weeks or trimethoprim/sulfamethoxazole (TMP/SMX) with gentamicin drops for 6 weeks. This study illustrates the importance of determining individual drug sensitivities for optimal treatment and maintaining current knowledge of the local MRSA strains. Empiric combination therapy of TMP/SMX with gentamicin is an effective first-line treatment for MRSA otorrhea. Regional differences in clindamycin sensitivities warrant clinical discretion. Fluoroquinolones should be avoided because of high rates of resistance unless culture sensitivity determines that they are appropriate. First-line agents for severe infections include combination therapy with vancomycin or linezolid.

Auditory Function After Application of Ototopical Vancomycin and Mupirocin Solutions in a Murine Model

Objective. To determine whether mupirocin (440 µg/mL) and vancomycin otic drops (25 mg/mL) show evidence of ototoxicity in CBA/J mice immediately following a 7-day course of daily intratympanic (IT) injections and 1 month following treatment.

Study Design. Nonrandomized controlled trial.

Setting. Academic hospital laboratory.

Subjects. Twenty CBA/J mice.

Results. Mean auditory brainstem response (ABR) thresholds increased in all drug- and saline-treated ears immediately after 7 days of IT injections but returned to baseline for most stimulus frequencies by 30 days later. This finding appeared to be correlated with the presence and subsequent resolution of tympanic membrane (TM) perforations and granulation tissue at the injection sites. Mupirocin-treated ears showed no significant difference in ABR thresholds compared to saline-treated ears. No significant differences were noted between vancomycin- and saline-treated ears, but there was a significant interaction between testing day and stimulus frequency ( P < .001). Further analysis revealed that ABR thresholds at 32 kHz remained significantly elevated in vancomycin-treated mice despite the resolution of TM perforations and granulation tissue 30 days after completion of IT injections (95% confidence interval, −13.5 to −5.5, P < .01).

Conclusion. Although IT application of mupirocin solution (440 µg/mL) caused no significant change in the ABR thresholds in a murine model, vancomycin solution (25 mg/mL) resulted in high-frequency threshold elevations in both the ear directly injected and the contralateral ear. Mupirocin solution may be beneficial in managing otitis externa and media caused by resistant pathogens. Further studies of ototopical vancomycin are needed to define parameters governing its safe use.