Breakdown of the round window membrane permeability barrier evoked by streptolysin O: possible etiologic role in development of sensorineural hearing loss in acute otitis media

The Impact of Early Childhood Otitis Media on Hearing Abilities: A Scoping Review

OBJECTIVES

Otitis media (OM) is among the most common childhood diseases. Many studies have suggested that recurrent OM episodes during early childhood can have long-lasting adverse effects on essentially every level of the auditory system. However, the literature on this topic is heterogeneous and results are mixed. Hence, a need exists to structure the available evidence. Here, a scoping review was conducted, aiming to (1) map the many different outcome measures used to assess the long-term impact of OM, (2) appraise the quality of the available OM documentation, and (3) provide a summary of the available evidence and its potential link with OM documentation.

DESIGN

Original articles were identified through systematic searches in the PubMed, Embase, and Cochrane Library databases. To be included, studies were required to assess the long-term impact of resolved early childhood OM on hearing abilities. Two reviewers independently screened studies for inclusion. A data charting form, developed by author LVY, was used to extract information about the publication (year, journal, country of data collection) and study characteristics (sample size, outcome measures, OM documentation).

RESULTS

The search identified 16,267 records, out of which 94 articles were included. Most of the current evidence is based on retrospective data from high-income countries, using a wide range of outcome measures. The retrospective study design poses challenges for thorough OM documentation, especially regarding OM history of the controls. A narrative synthesis showed consistently elevated audiometric thresholds in the extended high-frequency range and poorer gap detection abilities in children with a history of early childhood OM. Mixed results were found in terms of speech perception and binaural unmasking.

CONCLUSIONS

This scoping review demonstrates the breadth of the literature on this topic. A wide range of outcome measures have been used, and the quality of OM documentation varies greatly across studies. Variability of the literature results may-at least to some extent-be explained by inadequate OM documentation, recruitment bias, and variability in the time since the last OM episode. Recommendations for future research are provided.

Immuno-surveillance and protection of the human cochlea

Background

Despite its location near infection-prone areas, the human inner ear demonstrates remarkable resilience. This suggests that there are inherent instruments deterring the invasion and spread of pathogens into the inner ear. Here, we combined high-resolution light microscopy, super-resolution immunohistochemistry (SR-SIM) and synchrotron phase contrast imaging (SR-PCI) to identify the protection and barrier systems in the various parts of the human inner ear, focusing on the lateral wall, spiral ganglion, and endolymphatic sac.

Materials and methods

Light microscopy was conducted on mid-modiolar, semi-thin sections, after direct glutaraldehyde/osmium tetroxide fixation. The tonotopic locations were estimated using SR-PCI and 3D reconstruction in cadaveric specimens. The sections were analyzed for leucocyte and macrophage activity, and the results were correlated with immunohistochemistry using confocal microscopy and SR-SIM.

Results

Light microscopy revealed unprecedented preservation of cell anatomy and several macrophage-like cells that were localized in the cochlea. Immunohistochemistry demonstrated IBA1 cells frequently co-expressing MHC II in the spiral ganglion, nerve fibers, lateral wall, spiral limbus, and tympanic covering layer at all cochlear turns as well as in the endolymphatic sac. RNAscope assays revealed extensive expression of fractalkine gene transcripts in type I spiral ganglion cells. CD4 and CD8 cells occasionally surrounded blood vessels in the modiolus and lateral wall. TMEM119 and P2Y12 were not expressed, indicating that the cells labeled with IBA1 were not microglia. The round window niche, compact basilar membrane, and secondary spiral lamina may form protective shields in the cochlear base.

Discussion

The results suggest that the human cochlea is surveilled by dwelling and circulating immune cells. Resident and blood-borne macrophages may initiate protective immune responses via chemokine signaling in the lateral wall, spiral lamina, and spiral ganglion at different frequency locations. Synchrotron imaging revealed intriguing protective barriers in the base of the cochlea. The role of the endolymphatic sac in human inner ear innate and adaptive immunity is discussed.

Audiometric evaluation in different clinical presentations of otitis media

OBJECTIVES

To assess the hearing thresholds in acute otitis media, otitis media with effusion and chronic otitis media (non-suppurative, non-cholesteatomatous suppurative and cholesteatomatous) and to compare the hearing outcomes with non-diseased ears (in bilateral cases) or contralateral healthy ears (in unilateral cases), since hearing loss is the most frequent sequel of otitis media and there is no previous study comparing the audiometric thresholds among the different forms of otitis media.

METHODS

Cross sectional, controlled study. We performed conventional audiometry (500-8000Hz) and tympanometry in patients with otitis media and healthy individuals (control group). Hearing loss was considered when the hearing thresholds were > 25 dBHL.

RESULTS

Of the 112 patients diagnosed with otitis media (151 ears), 48 were men (42.86%) and 64 were women (57.14%). The average age was 42.72 years. Of those, 25 (22.32%) were diagnosed as AOM, 15 (13.39%) were diagnosed with OME and the remaining 72 (63.28%) were diagnosed with COM (non-suppurative COM, n=31; suppurative COM, n=18; cholesteatomatous COM, n=23). As compared with controls, all forms of otitis media had significantly higher bone-conduction thresholds (500-4000Hz). Conductive hearing loss was the most frequent type of hearing loss (58.94%). However, the number of patients with mixed hearing loss was also relevant (39.07%). We noted that the presence of sensorioneural component occurred more frequently in 1) Higher frequencies; and 2) In groups of otitis media that were more active or severe in the inflammatory/infective standpoint (AOM, suppurative COM and cholesteatomatous COM).

CONCLUSION

All types of otitis media, even those with infrequent episodes of inflammation and otorrhea, had worse bone conduction thresholds as compared with nondiseased ears (p<0.01). We observed worse hearing outcomes in ears with recurrent episodes of otorrhea and in ears with AOM, especially in high frequencies.

Determinants of Cochlear Dysfunction in Chronic Otitis Media: Mucosal Disease

The nature of association between chronic otitis media (COM)-mucosal disease and sensorineural hearing loss is controversial. Identifying the risk factors which influence the bone conduction threshold in these patients can help the clinician in counselling the patients for surgery at the earliest to achieve optimum hearing outcomes. The present study was undertaken to determine the association between COM-mucosal disease and cochlear dysfunction. The study also aimed at identifying the determinants and their influence on the bone conduction thresholds of the diseased ear. In this study, 72 patients with unilateral chronic otitis media-mucosal disease were enrolled consecutively. All patients were enquired in detail about their presenting ear symptoms. All the patients underwent a pure tone audiogram in a sound treated room. Patients were categorised into two groups according to the presence of conductive hearing loss only or with a sensorineural component. The bone conduction thresholds were calculated and compared for frequencies at 0.5, 1, 2 and 4 kHz. The average hearing threshold for air conduction and bone conduction were calculated across 0.5, 1 and 2 kHz. Bone conduction threshold more than 20 decibels (dB) in any of the frequencies were considered significant and indicative of having sensorineural hearing loss component. The contralateral healthy ear served as control to cancel out the confounding factors such as presbyacusis, noise induced hearing loss, congenital hearing loss, etc. Multivariate linear regression models were used to evaluate the relationships between bone conduction thresholds and chronic otitis media-mucosal disease. In the present study, 18.05% of participants had a sensorineural component. The difference between the bone conduction threshold in the diseased ear and normal ear ranged from 5.41 dB at 0.5 kHz to 3.77 dB at 4 kHz (p < 0.001). Bone conduction thresholds at 4 kHz were greater than that for speech frequencies (p < 0.5). 84.6% of participants with sensorineural component had a disease duration of less than 5 years and the remaining 15.4% had a duration of greater than 15 years. There was no statistically significant difference in the incidence of sensorineural component based on the site of the perforation (p = 0.341). 21.9% of participants who used topical antibiotic drops developed a sensorineural component, while 15% of participants who did not use antibiotic ear drop preparation developed a sensorineural component. Multivariate linear regression analysis revealed that increasing age was the only factor associated with increase in bone conduction thresholds of the diseased ear (p = 0.002). Chronic otitis media- mucosal disease appears to be associated with higher bone conduction thresholds, signifying cochlear dysfunction. A statistically significant higher bone conduction thresholds are seen across 0.5 to 4 kHz in the diseased ears compared to the normal ears, signifying the vulnerability of the inner ear against chronic otitis media. In our analysis increasing age is the most significant predisposing factor associated with higher bone conduction thresholds. Higher frequencies are more affected than lower speech frequencies. Sensorineural hearing loss can occur early in the disease process and early surgical intervention in COM-mucosal disease is recommended to prevent increase in bone conduction thresholds and achieve optimum hearing outcomes.

Presentation, Management, and Hearing Outcomes of Labyrinthine Fistula Secondary to Cholesteatoma: A Systematic Review and Meta-analysis

OBJECTIVE

The current study systematically reviewed the literature to compare auditory outcomes of patients treated for labyrinthine fistula (LF) based on characteristics of disease and surgical management.

DATABASES REVIEWED

PubMed, Scopus, Web of Science.

METHODS

Original series (at least five cases) published from 2000 reporting management and hearing results of LF secondary to cholesteatoma were included. Proportion and odds-ratio (OR) meta-analyses were conducted through inverse variance random-effects models based on logit transformation.

RESULTS

The prevalence of LF is estimated to be 7% (95% confidence interval [CI], 5-9%). Fistulae involving the lateral semicircular canal (90%; 95% CI, 87-93%) and larger than 2 mm (53%; 95% CI, 43-64%) were common, whereas membranous involvement was less frequent (20%; 95% CI, 12-30%). Complete removal of the cholesteatoma matrix overlying the LF was mostly applied. Bone conduction (BC) preservation was frequently achieved (81%; 95% CI, 76-85%); new-onset postoperative anacusis was rarely reported (5%; 95% CI, 4-8%). A higher chance of BC preservation was associated with sparing the perilymphatic space (OR, 4.67; 95% CI, 1.26-17.37) or membranous labyrinth (OR, 4.56; 95% CI, 2.33-8.93), exclusive lateral semicircular canal involvement (OR, 3.52; 95% CI, 1.32-9.38), smaller size (<2 mm; OR, 3.03; 95% CI, 1.24-7.40), and intravenous steroid infusion (OR, 7.87; 95% CI, 2.34-26.42).

CONCLUSION

LF occurs in a significant proportion of patients with cholesteatoma. In the past two decades, complete removal of the cholesteatoma matrix followed by immediate sealing has been favored, supported by the high proportion of BC preservation. Hearing preservation depends primarily on characteristics of the LF, and specific surgical strategies should be pursued. Intraoperative and postoperative intravenous steroid infusion is recommended.

Analysis of tinnitus severity and associated risk factors in patients with chronic otitis media: data from the multinational collaborative Chronic Otitis Media Questionnaire-12 study

BACKGROUND

Subjective tinnitus is a common symptom, and there is often an underlying otological cause. This study investigated the degree of tinnitus-related annoyance in patients with chronic otitis media and analysed whether associations with tinnitus severity exist.

METHOD

The multinational collaborative Chronic Otitis Media Questionnaire-12 study collected prospective data on 478 adult patients suffering from chronic otitis media across 9 otology referral centres in 8 countries. Based on this dataset, we investigated tinnitus severity using participant responses to item 7 of a native version of the Chronic Otitis Media Questionnaire-12.

RESULTS

With respect to tinnitus severity, 23.8 per cent, 17.4 per cent, 15.5 per cent, and 43.4 per cent of participants reported no, minor, moderate, and major inconvenience or greater, respectively. The absence of ear discharge, absence of cholesteatoma, and poorer disease-specific health-related quality-of-life were associated with increased tinnitus severity in patients with chronic otitis media, whereas age, hearing disability and geographical region showed no association.

CONCLUSION

This analysis provided novel insight into potential risk factors for tinnitus in patients with chronic otitis media.

Relation between otitis media and sensorineural hearing loss: a systematic review

OBJECTIVES

This systematic review summarises the evidence on the correlation between recurrent acute otitis media (rAOM) or chronic suppurative otitis media (CSOM) and sensorineural hearing loss (SNHL).

RESEARCH METHODS

PubMed, Embase and Cochrane Library databases were searched from inception to 15 January 2021. Two authors independently identified articles, extracted data and performed quality assessment for included studies. Studies comparing the sensorineural hearing levels of patients with a history of rAOM/CSOM for >3 months to a control group were included.

RESULTS

Screening of 4168 articles lead to inclusion of two case-control studies (control-group: patients non-OM) and seven cohort-studies (control group: contralateral ear). Quality assessment indicated considerable risk of bias in all studies. Reported populations varied (sample size 13-607, mean age 22-41.5 years, mean duration of disease 6.1-12.4 years). The OR for SNHL in the OM-group was 3.30-7.86 (95% CI 1.16 to 9.40, p<0.05) in cohort studies (n=2), and 0.05 (95% CI 0 to 0.78, p<0.05) in a case-control study. Mean/median bone conduction thresholds were respectively 1.19-32.21/0-10 dB higher on all frequencies (0.5-4 kHz) for the OM-group in four cohort studies (p<0.05). Two other studies reported no statistical test outcomes.

CONCLUSION

Due to the high risk of bias of included studies, effect estimates heterogeneity and suboptimal research designs, no conclusion on the correlation between OM and SNHL can be made. It emphasises the need for future prognostic studies.

Clinical evaluation of the vestibular impairment using video head impulse test In children with acute otitis media

OBJECTIVES

The objectives of the present study were to evaluate the vestibular impairment in children with acute otitis media (AOM) and dizziness by using video head impulse test (vHIT) and to compare their results with healthy children.

METHODS

The study included two groups of subjects. The patient group consisted of 34 pediatric patients with AOM and dizziness and the control group consisted of 35 healthy children, age between 4 and 15. The age, gender, mean vHIT gains and gain asymmetry values were compared between groups for each canal. In both groups, mean vHIT gains were compared between the right and left sides. Additionally, mean vHIT gains and the presence of saccades according to AOM stages were analyzed.

RESULTS

The comparison of vHIT gains between affected and unaffected sides in patients revealed a significant decrease only in the anterior canal plane on the affected side. Covert saccades were observed in 32% of the patients. When comparing the AOM stages and the presence of saccades in patients, no difference was detected between stages.

CONCLUSION

vHIT is a useful vestibular test for the evaluation of vestibular impairment in children with an applicability rate of 92% in healthy children and 70% in patients with AOM and dizziness. The patients with AOM and dizziness are presented with a decrease in vHIT gains and the presence of cover saccades only in vertical canal planes, supporting that slight vestibular impairment in these patients may represent pathologic vHIT results only in vertical canal planes.

The Relation of Sudden Sensorineural Hearing Loss in Pediatric Patients With Recurrent Otitis Media: A Nested Case-control Study Using a National Sample Cohort

OBJECTIVE

The risk of sudden sensorineural hearing loss (SSNHL) was suggested to be increased in chronic otitis media patients. This study expanded previous findings by using pediatric patients with recurrent otitis media.

STUDY DESIGN

A nested case-control study.

SETTING

Participants in the Korean National Health Insurance Service-National Sample Cohort that were less than 15 years old from 2002 to 2004 were included.

PATIENTS

Overall, 24,226 patients with ≥ 5 instances of otitis media were 1:1 matched with a group controlled for age, sex, income, and region of residence.

MAIN OUTCOME MEASURE

The occurrence of SSNHL was followed until 2013. The hazard ratio (HR) for SSNHL was analyzed in the otitis media patients using a stratified Cox proportional hazard regression model. Matching variables were stratified. The histories of sinusitis and atopic dermatitis were adjusted. Subgroup analysis was performed according to age and sex.

RESULTS

Overall, 0.14% (33/24,226) of the otitis media group and 0.06% (14/24,226) of the control group had SSNHL (p = 0.006). The otitis media group had a higher adjusted HR for SSNHL than the control group (adjusted HR = 2.13, 95% CI = 1.13-4.02). According to age, the 10- to 14-year-old group showed a 9.07-fold higher HR for SSNHL than the control group (95% CI = 1.14-72.54). According to sex, the female group showed a 3.74-fold higher HR for SSNHL than the control group (95% CI = 1.24-11.29).

CONCLUSION

Recurrent otitis media in children was related to the onset of SSNHL.

Nanoparticle-based drug delivery in the inner ear: current challenges, limitations and opportunities

Hearing loss is the most common neurosensory impairment worldwide. While conductive hearing loss can be managed by surgery, the management of sensorineural hearing loss (SNHL), related to the damage of sensory cells of the inner ear is more challenging to manage medically. Many causes of SNHL such as sudden idiopathic SNHL, Meniere's disease, noise-induced hearing loss, autoimmune hearing loss or hearing loss from exposure to ototoxic substances can benefit from delivery of otoprotective drugs to the inner ear. However, systemic drug delivery through oral, intravenous and intramuscular methods leads to undesirable side effects due to the inner ear's limited blood supply and the relatively poor penetration of the blood-inner ear barrier (BLB). Therefore, there has been an increased interest for the targeted drug delivery to the inner ear using nanoparticles. Drug delivery through nanoparticles offers several advantages including drug stabilization for controlled release and surface modification for specific targeting. Understanding the biocompatibility of nanoparticles with cochlea and developing novel non-invasive delivery methods will promote the translation of nanoparticle-mediated drug delivery for auditory disorders from bench to bedside.

Cochlear Fistula in Chronic Otitis Media without Cholesteatoma

Cochlear fistula in the chronic otitis media (COM) without cholesteatoma is an extremely rare with only a few cases reported in the literature to this date. We describe a case of cochlear fistula observed in a female with COM without cholesteatoma. This report presents the first clinical case of a transtympanic iatrogenic trauma by habitual cotton swabs probably causing cochlear fistula.

Acute otitis media associated bilateral sudden hearing loss: case report and literature review

Background:

Sudden sensorineural hearing loss is a rare otological condition with potential for dire outcomes including permanent hearing loss. Although the majority of cases are deemed idiopathic, bilateral sudden sensorineural hearing loss represents a rare subset typically related to systemic conditions, with higher morbidity and mortality. A controversial association with acute otitis media has been reported, with few bilateral cases published in the literature.

Case report:

A very rare case of bilateral sudden sensorineural hearing loss associated with acute otitis media is described, with a review of the literature.

Conclusion:

The limited evidence available suggests that acute otitis media with tinnitus and/or bacterial pathology may have an increased risk of sudden sensorineural hearing loss, which is consistent with the case described. Although there is no sufficiently powered published evidence to provide definitive treatment guidelines, the literature reviewed suggests that early myringotomy and antibiotics may greatly improve treatment outcomes.

Pathologic Changes of the Peripheral Vestibular System Secondary to Chronic Otitis Media

OBJECTIVE

To evaluate the histopathologic changes of dark, transitional, and hair cells of the vestibular system in human temporal bones from patients with chronic otitis media.

STUDY DESIGN

Comparative human temporal bone study.

SETTING

Otopathology laboratory.

SUBJECTS AND METHODS

To compare the density of vestibular dark, transitional, and hair cells in temporal bones with and without chronic otitis media, we used differential interference contrast microscopy.

RESULTS

In the chronic otitis media group (as compared with the age-matched control group), the density of type I and type II hair cells was significantly decreased in the lateral semicircular canal, saccule, and utricle (P < .05). The density of type I cells was also significantly decreased in the chronic otitis media group in the posterior semicircular canal (P = .005), but that of type II cells was not (P = .168). The mean number of dark cells was significantly decreased in the chronic otitis media group in the lateral semicircular canal (P = .014) and in the posterior semicircular canal (P = .002). We observed no statistically significant difference in the density of transitional cells between the 2 groups (P > .1).

CONCLUSION

The findings of our study suggest that the decrease in the number of vestibular sensory cells and dark cells could be the cause of the clinical symptoms of imbalance of some patients with chronic otitis media.

Effect of intratympanic steroid administration on sensorineural hearing loss associated with acute otitis media

OBJECTIVE

To evaluate a small cohort of patients who presented with symptoms and signs consistent with acute infective sensorineural hearing loss who were treated with intratympanic steroids.

METHOD

Seven patients received a 7-day course of oral antibiotics and oral prednisolone followed by 3 intratympanic injections of methylprednisolone and 1 week of topical dexamethasone drops.

RESULTS

Hearing improved in 57 per cent of patients (four out of seven). The mean improvement in this group was 24 dB (range, 10-52 dB). The magnitude of the sensorineural hearing loss at presentation was less in those who responded to intratympanic steroid therapy than in non-responders (mean pure tone average of 30 dB versus 65 dB pre-intratympanic steroids, and 14 dB versus 83 dB post-intratympanic steroids, respectively).

CONCLUSION

The results of our study suggest that intratympanic steroids provide a valuable contribution to the treatment of acute infective sensorineural hearing loss and may provide additional benefit by virtue of a concentrated local steroid effect in patients who do not respond to antibiotics.

An Overview of Nanoparticle Based Delivery for Treatment of Inner Ear Disorders

Nanoparticles offer new possibilities for inner ear treatment as they can carry a variety of drugs, protein, and nucleic acids to inner ear. Nanoparticles are equipped with several functions such as targetability, immuno-transparency, biochemical stability, and ability to be visualized in vivo and in vitro. A group of novel peptides can be attached to the surface of nanoparticles that will enhance the cell entry, endosomal escape, and nuclear targeting. Eight different types of nanoparticles with different payload carrying strategies are available now. The transtympanic delivery of nanoparticles indicates that, depending on the type of nanoparticle, different migration pathways into the inner ear can be employed, and that optimal carriers can be designed according to the intended cargo. The use of nanoparticles as drug/gene carriers is especially attractive in conjunction with cochlear implantation or even as an inclusion in the implant as a drug/gene reservoir.

Role of pore-forming toxins in bacterial infectious diseases

Pore-forming toxins (PFTs) are the most common bacterial cytotoxic proteins and are required for virulence in a large number of important pathogens, including Streptococcus pneumoniae, group A and B streptococci, Staphylococcus aureus, Escherichia coli, and Mycobacterium tuberculosis. PFTs generally disrupt host cell membranes, but they can have additional effects independent of pore formation. Substantial effort has been devoted to understanding the molecular mechanisms underlying the functions of certain model PFTs. Likewise, specific host pathways mediating survival and immune responses in the face of toxin-mediated cellular damage have been delineated. However, less is known about the overall functions of PFTs during infection in vivo. This review focuses on common themes in the area of PFT biology, with an emphasis on studies addressing the roles of PFTs in in vivo and ex vivo models of colonization or infection. Common functions of PFTs include disruption of epithelial barrier function and evasion of host immune responses, which contribute to bacterial growth and spreading. The widespread nature of PFTs make this group of toxins an attractive target for the development of new virulence-targeted therapies that may have broad activity against human pathogens.

Pseudo-sudden deafness

OBJECTIVES

We describe the symptom complex and management of a clinical entity we refer to as "pseudo-sudden deafness," which is an episode of acute otitis media that leads to sensorineural hearing loss with reduced speech discrimination.

METHODS

We included 8 adult patients with audiometrically confirmed, asymmetric sensorineural hearing loss with decreased speech discrimination that presented after an episode of acute otitis media. Magnetic resonance imaging ruled out retrocochlear disease. Both physical examination and myringotomy helped confirm the diagnosis of serous otitis media (SOM). Myringotomy, tympanostomy tubes, oral antibiotics, and otic antibiotic-steroid drops were used to treat the SOM. Oral steroids were used to treat the sensorineural component.

RESULTS

Pretreatment and posttreatment audiograms showed an improvement in speech discrimination score, pure tone thresholds, or both after treatment for underlying SOM and sensorineural hearing loss in 6 of the 8 patients.

CONCLUSIONS

Patients who present with an acute onset of unilateral sensorineural hearing loss with decreased speech discrimination may be mistakenly thought to have idiopathic sudden sensorineural hearing loss when, in fact, they may have an SOM-induced phenomenon that is potentially reversible. The distinguishing feature is a preexisting otitis media, which must be treated first, before the administration of steroids.

RAB-5- and RAB-11-dependent vesicle-trafficking pathways are required for plasma membrane repair after attack by bacterial pore-forming toxin

Pore-forming toxins (PFTs) secreted by pathogenic bacteria are the most common bacterial protein toxins and are important virulence factors for infection. PFTs punch holes in host cell plasma membranes, and although cells can counteract the resulting membrane damage, the underlying mechanisms at play remain unclear. Using Caenorhabditis elegans as a model, we demonstrate in vivo and in an intact epithelium that intestinal cells respond to PFTs by increasing levels of endocytosis, dependent upon RAB-5 and RAB-11, which are master regulators of endocytic and exocytic events. Furthermore, we find that RAB-5 and RAB-11 are required for protection against PFT and to restore integrity to the plasma membrane. One physical mechanism involved is the RAB-11-dependent expulsion of microvilli from the apical side of the intestinal epithelial cells. Specific vesicle-trafficking pathways thus protect cells against an attack by PFTs on plasma membrane integrity, via altered plasma membrane dynamics.

Spiral ligament fibrocyte-derived MCP-1/CCL2 contributes to inner ear inflammation secondary to nontypeable H. influenzae-induced otitis media

Background

Otitis media (OM), one of the most common pediatric infectious diseases, causes inner ear inflammation resulting in vertigo and sensorineural hearing loss. Previously, we showed that spiral ligament fibrocytes (SLFs) recognize OM pathogens and up-regulate chemokines. Here, we aim to determine a key molecule derived from SLFs, contributing to OM-induced inner ear inflammation.

Methods

Live NTHI was injected into the murine middle ear through the tympanic membrane, and histological analysis was performed after harvesting the temporal bones. Migration assays were conducted using the conditioned medium of NTHI-exposed SLFs with and without inhibition of MCP-1/CCL2 and CCR2. qRT-PCR analysis was performed to demonstrate a compensatory up-regulation of alternative genes induced by the targeting of MCP-1/CCL2 or CCR2.

Results

Transtympanic inoculation of live NTHI developed serous and purulent labyrinthitis after clearance of OM. THP-1 cells actively migrated and invaded the extracellular matrix in response to the conditioned medium of NTHI-exposed SLFs. This migratory activity was markedly inhibited by the viral CC chemokine inhibitor and the deficiency of MCP-1/CCL2, indicating that MCP-1/CCL2 is a main attractant of THP-1 cells among the SLF-derived molecules. We further demonstrated that CCR2 deficiency inhibits migration of monocyte-like cells in response to NTHI-induced SLF-derived molecules. Immunolabeling showed an increase in MCP-1/CCL2 expression in the cochlear lateral wall of the NTHI-inoculated group. Contrary to the in vitro data, deficiency of MCP-1/CCL2 or CCR2 did not inhibit OM-induced inner ear inflammation in vivo. We demonstrated that targeting MCP-1/CCL2 enhances NTHI-induced up-regulation of MCP-2/CCL8 in SLFs and up-regulates the basal expression of CCR2 in the splenocytes. We also found that targeting CCR2 enhances NTHI-induced up-regulation of MCP-1/CCL2 in SLFs.

Conclusions

Taken together, we suggest that NTHI-induced SLF-derived MCP-1/CCL2 is a key molecule contributing to inner ear inflammation through CCR2-mediated recruitment of monocytes. However, deficiency of MCP-1/CCL2 or CCR2 alone was limited to inhibit OM-induced inner ear inflammation due to compensation of alternative genes.

Potential role for lipopolysaccharide in congenital sensorineural hearing loss

Congenital sensorineural hearing loss (SNHL) is common. In the Western world, the incidence is 1-3 per 1000 live births. The aetiology encompasses genetic and non-genetic factors accounting for 55 % and 45 % of cases, respectively. Reports that describe the contribution of intrauterine infection to the occurrence of congenital SNHL are limited, and comparative analysis of the different pathogens is lacking. Lipopolysaccharide (LPS), a product of bacteriolysis, has been demonstrated to be associated with inner ear damage in experimental studies. To elucidate the potential role of this toxin in congenital SNHL and to identify the pathogenesis and transmission routes, we reviewed the literature. We speculate that different routes of exposure to LPS in utero may result in congenital inner ear damage.

Sensorineural hearing loss in patients with chronic otitis media

Chronic otitis media is generally associated with some degree of hearing loss, which is often the patient's chief complaint. This hearing loss is usually conductive, resulting from tympanic membrane rupture and/or changes in the ossicular chain due to fixation or erosion caused by the chronic inflammatory process. When cholesteatoma or granulation tissue is present in the middle ear cleft, the degree of ossicular destruction is even greater. An issue that has recently gained attention is additional sensorineural hearing loss due to chronic otitis media. While the conductive loss can be minimized through surgery, sensorineural hearing loss constitutes a permanent after effect, attenuated only through the use of a hearing aid. However, a few groups have reported a decrease in sensorineural function in these patients as well. This survey study performed at a referral center evaluates the occurrence of sensorineural hearing loss in ambulatory patients with this disease. We reviewed the files of patients with unilateral chronic otitis media. One hundred and fifty patients met the inclusion criteria: normal otoscopy and normal hearing in the contralateral ear.

MAIN OUTCOME MEASURE

bone-conduction threshold averages were calculated for frequencies of 500, 1,000, 2,000, 3,000 and 4,000 Hz, with comparison between the normal ear and the ear with chronic otitis media. Thresholds were examined separately for each frequency. The bone-conduction threshold averages for the normal side were lower than those for the ear with chronic otitis media. The threshold shift was statistically significant for each frequency (P<0.0001, Student's t test). There were differences between the groups when analyzed for age (500 and 1,000 Hz) or the presence of cholesteatoma (1,000 Hz). This study shows that chronic otitis media is associated with a decrease in cochlear function.

Toll-like receptor 2-dependent NF-kappaB activation is involved in nontypeable Haemophilus influenzae-induced monocyte chemotactic protein 1 up-regulation in the spiral ligament fibrocytes of the inner ear

Inner ear dysfunction secondary to chronic otitis media (OM), including high-frequency sensorineural hearing loss or vertigo, is not uncommon. Although chronic middle ear inflammation is believed to cause inner ear dysfunction by entry of OM pathogen components or cytokines from the middle ear into the inner ear, the underlying mechanisms are not well understood. Previously, we demonstrated that the spiral ligament fibrocyte (SLF) cell line up-regulates monocyte chemotactic protein 1 (MCP-1) expression after treatment with nontypeable Haemophilus influenzae (NTHI), one of the most common OM pathogens. We hypothesized that the SLF-derived MCP-1 plays a role in inner ear inflammation secondary to OM that is responsible for hearing loss and dizziness. The purpose of this study was to investigate the signaling pathway involved in NTHI-induced MCP-1 up-regulation in SLFs. Here we show for the first time that NTHI induces MCP-1 up-regulation in the SLFs via Toll-like receptor 2 (TLR2)-dependent activation of NF-kappaB. TLR2(-/-)- and MyD88(-/-)-derived SLFs revealed involvement of TLR2 and MyD88 in NTHI-induced MCP-1 up-regulation. Studies using chemical inhibitors and dominant-negative constructs demonstrated that it is mediated by the IkappaKbeta-dependent IkappaBalpha phosphorylation and NTHI-induced NF-kappaB nuclear translocation. Furthermore, we demonstrated that the binding of NF-kappaB to the enhancer region of MCP-1 is involved in this up-regulation. In addition, we have identified a potential NF-kappaB motif that is responsive and specific to certain NTHI molecules or ligands. Further studies are necessary to reveal specific ligands of NTHI that activate host receptors. These results may provide us with new therapeutic strategies for prevention of inner ear dysfunction secondary to chronic middle ear inflammation.

Characterization of rat spiral ligament cell line immortalized by adenovirus 12-simian virus 40 hybrid virus

OBJECTIVES

Spiral ligament fibrocytes play an important role in inner ear ion homeostasis and are classified into several subtypes according to expression of specific enzymes such as Na+, K+ -ATPase, Ca++ -ATPase, and carbonic anhydrase. Although our understanding of the cell and molecular biology of spiral ligament fibrocytes has increased over time, access to these cells still remains a significant hurdle hindering future studies. In this study, we aimed to establish a rat spiral ligament cell line with minimal disruption of the original characteristics.

METHODS

The primary spiral ligament fibrocytes were exposed to adenovirus 12-simian virus 40 hybrid virus for immortalization. Karyotypic analysis was performed after stabilization of the infected cells, and the population doubling time was compared to that of the primary cell. The cell line was characterized by immunolabeling and electron microscopy.

RESULTS

We describe the establishment and characterization of a line of type I spiral ligament fibrocytes immortalized with an adenovirus 12-simian virus 40 hybrid virus.

CONCLUSIONS

This cell line can be a useful research tool for investigating the role of spiral ligament fibrocytes in homeostasis and inflammation of the inner ear.

Evaluation of the mouse model for acute otitis media

Various animal models have been employed for otitis media research. The mouse has been studied less, in spite of its many advantages. To better understand the suitability of the mouse for studies of otitis media, an evaluation was made of its middle ear inflammatory processes following inoculation with heat-killed Streptococcus pneumoniae (strain 6A), one of the three most common bacteria to cause otitis media in the human. A total of 94 BALB/c mice were injected transtympanically with three concentrations of heat-killed bacteria (10(4), 10(6), and 10(9) organisms per ml) and inflammation evaluated with both histologic examination and auditory brainstem response audiometry. Dose-related measures of the time course of inflammation showed it was maximal at 3 days. PBS-injected control mice also demonstrated some degree of middle ear inflammation. Therefore, inflammation measures from PBS injected mice were used as the threshold above which histologic inflammatory changes would be considered a response to bacteria. These quantitative comparisons of bacterial and PBS inoculations revealed the most significant middle ear measures of inflammation were amount of fluid in the middle ear, tympanic membrane thickness, and number of inflammatory cells. The induction of middle ear inflammation in the mouse demonstrated the applicability of this model for investigations of otitis media.

Efficacy of Gene Transfer through the Round Window Membrane: An in vitro Model

The viral vector-transgene soaked gelatin-sponge method has been shown to be successful in mediating transgene expression across an intact round window membrane (RWM) in mouse in vivo. However, there are many confounding factors which make it difficult to evaluate the role of the RWM in gene transfer. We have created an in vitro model to test the feasibility of gene delivery through an intact RWM. The round window including the bony niche of a CD1 mouse was removed under an operating microscope and fixed with adhesive on the base of a petri dish through which a hole had been drilled. Toluidine blue was injected into the niche containing a hyaluronic acid ester sponge against the round window membrane. The niche was closed with a fascia. A plastic tube containing PBS was fixed on the opposite side, from where the samples were collected at different time points. The concentration of toluidine blue was evaluated spectrophotometrically. An adenoviral vector containing green fluorescent protein (GFP) marker gene was injected into the niche. Samples were collected from the opposite side at different time points. The presence of the vector was studied with GFP PCR. We also modulated the permeability of the RWM by treating it with clinically applicable detergents, histamine or silver nitrate. Silver nitrate and trichloracetic acid caused destruction of the surface epithelium of the RWM as shown by light microscopy. Both toluidine blue and adenoviral vectors passed through the RWM in a time-dependent fashion. RWM cells expressed GFP after Ad-GFP treatment. The permeability of the RWM was decreased after treatment with different detergents, histamine or silver nitrate. RWM offers an atraumatic route to the inner ear. Compared with more invasive gene delivery methods, this technique represents a safer and clinically more viable route of cochlear gene delivery.

Spiral ligament fibrocytes release chemokines in response to otitis media pathogens

CONCLUSION

Spiral ligament fibrocytes (SLFs) may be involved in the innate immune response of the inner ear by producing chemoattractants for recruiting inflammatory cells such as neutrophils and monocytes.

OBJECTIVE

The purpose of this study was to investigate the cellular responses of SLFs when challenged by inflammatory stimuli such as components of otitis media pathogens or proinflammatory cytokines.

MATERIALS AND METHODS

To detect released inflammatory cytokines and chemokines, cells were treated for 48 h with whole lysates of nontypable Haemophilus influenzae (NTHi), Streptococcus pneumoniae, or with interleukin 1 alpha (IL-1alpha). The culture medium was then collected and applied to protein arrays. To compare mRNA levels of chemokines, total RNA was extracted after 3 h of treatment with the above agents, and quantitative real-time PCR was performed.

RESULTS

Protein array analysis showed that in response to NTHi or S. pneumoniae, rat SLFs released monocyte chemotactic protein 1, macrophage inflammatory protein 3 alpha, TNF-alpha, and cytokine-induced neutrophil chemoattractant 2 and 3. Treatment with IL-1alpha, on the other hand, resulted in release of MCP-1 but not the other molecules. Tissue inhibitor of metalloproteinase 1 and vascular endothelial growth factor were released regardless of the inflammatory stimulus used.

Efficacy of gene transfer through the round window membrane: an in vitro model

The viral vector-transgene soaked gelatin-sponge method has been shown to be successful in mediating transgene expression across an intact round window membrane (RWM) in mouse in vivo. However, there are many confounding factors which make it difficult to evaluate the role of the RWM in gene transfer. We have created an in vitro model to test the feasibility of gene delivery through an intact RWM. The round window including the bony niche of a CD1 mouse was removed under an operating microscope and fixed with adhesive on the base of a petri dish through which a hole had been drilled. Toluidine blue was injected into the niche containing a hyaluronic acid ester sponge against the round window membrane. The niche was closed with a fascia. A plastic tube containing PBS was fixed on the opposite side, from where the samples were collected at different time points. The concentration of toluidine blue was evaluated spectrophotometrically. An adenoviral vector containing green fluorescent protein (GFP) marker gene was injected into the niche. Samples were collected from the opposite side at different time points. The presence of the vector was studied with GFP PCR. We also modulated the permeability of the RWM by treating it with clinically applicable detergents, histamine or silver nitrate. Silver nitrate and trichloracetic acid caused destruction of the surface epithelium of the RWM as shown by light microscopy. Both toluidine blue and adenoviral vectors passed through the RWM in a time-dependent fashion. RWM cells expressed GFP after Ad-GFP treatment. The permeability of the RWM was decreased after treatment with different detergents, histamine or silver nitrate. RWM offers an atraumatic route to the inner ear. Compared with more invasive gene delivery methods, this technique represents a safer and clinically more viable route of cochlear gene delivery.

[Cochlear involvement in acute otitis media]

OBJECTIVE

An experimental design with mice has been realized to understand the origin of sensorial hearing loss related to infectious processes in the middle ear. Our aim is to study if the cilliated cells in the Corti organ's are lost after one or more acute otitis media.

MATERIAL AND METHODS

For that, thirty Sprague-Dawley mice have been divided in two groups. In the first one, we have induced one acute otitis media, in the second group we have induced two infections of this kind.

RESULTS

The statistic study shows that the loss of the cilliated cells is greater in the basal turn of the mice is cochlea, in the first group (alpha=0,020) and also in the second (alpha=0,038). We've noticed in the first group the near absence of injury in the middle turn, but in all samples of the second group we found that injury (alpha=0,002).

CONCLUSIONS

In acute otitis media, the loss of ciIliated cells are mainly in the basal turn of the mice is cochlea, and affects the middle turn when the infection is repeated.

Fistula of the cochlear labyrinth in noncholesteatomatous chronic otitis media

OBJECTIVE

To discuss the clinical aspects and management of promontory fistula of the cochlear labyrinth.

STUDY DESIGN

Case report and review of the literature.

SETTING

University hospital, tertiary referral center.

PATIENT, INTERVENTION, AND RESULTS

The authors describe an unusual case of cochlear fistula localized to the promontory discovered during tympanoplasty for noncholesteatomatous chronic otitis media in a 59-year-old woman. Bone conduction was slightly impaired after operation and hearing improved after a revision myringoplasty performed for reperforation.

CONCLUSION

Erosion of the bone of the labyrinth can also be observed in noncholesteatomatous otitis media. The presence of a fistula is not always associated with profound hearing loss. Overlying pathologic tissue can be removed without damaging the membranous labyrinth.

Role of glucocorticoids in ototopical antibiotic-steroid preparations in the treatment of chronic suppurative otitis media

BACKGROUND

It is conventional to use antibiotic-steroid combination eardrops, although the advantage of steroid combination has not been substantiated. The present prospective randomized comparative study is designed to assess the role of glucocorticoids in ototopical antibiotic-steroid preparations in the treatment of chronic suppurative otitis media (CSOM).

METHODS

Pre-treatment clinical assessment, bacteriology of the middle ear discharge and pure tone audiogram were done. CSOM with organisms sensitive to gentamicin were treated either with plain gentamycin (GM) or gentamycin steroid combination (GM-S) eardrops for a period of 3 weeks. Post-treatment clinical, bacteriological and audiogram response was recorded 1 week after discontinuing the eardrops. The post-treatment clinical improvement, bacteriologic improvement and changes in hearing threshold at speech frequencies were analyzed by using unpaired Student's t test and chi(2) tests.

RESULTS

The most common organism associated with CSOM was Pseudomonas aeruginosa (33.92%). Clinical improvement was seen in 87.7 and 86.5% cases but bacteriological improvement in only 82.5 and 75% of cases treated with GM and GM-S (p >0.05), respectively. On comparing the pre- and post-treatment pure tone audiograms in 95 patients, 28.9% treated with GM and 30% with GM-S showed deterioration in bone conduction threshold above 5 dB (p >0.05) at speech frequencies. The mean increase in bone conduction in the two groups was 7.7 and 8.57 dB (p >0.05), respectively.

CONCLUSIONS

Our results indicate that there is no difference in the clinical and bacteriological improvement or ototoxicity either with topical GM or GM-S. Hence, we conclude that it is unnecessary to combine steroids with topical antibiotic preparations for the management of CSOM.

Intracochlear perfusion of pneumolysin, a pneumococcal protein, rapidly abolishes auditory potentials in the Guinea pig cochlea

OBJECTIVE

Bacterial meningitis and chronic suppurative otitis media caused by Streptococcus pneumoniae are associated with considerable otological morbidity. Specifically, sensorineural hearing loss is a permanent sequela in a third of those who contract pneumococcal meningitis. Pneumolysin, a pneumococcal protein, has been implicated as one of the main virulence/cytotoxic factors. Its pathogenicity is intimately dependent on an ability to form transmembrane pores on binding with cholesterol in target tissues.

MATERIAL AND METHODS

We perfused wild-type pneumolysin, at a number of different concentrations, into the guinea pig cochlea and used electrocochleography to characterize the effects of this cytolytic exotoxin in the organ of Corti.

RESULTS

Intracochlear perfusion of pneumolysin (10 microg/50 microl) reduced the compound action potential of the auditory nerve within seconds. The cochlear microphonics (f1=8 kHz, f2=9.68 kHz) and their distortion product (2f1-f2) were also reduced, albeit in a slightly less dramatic fashion. At lower concentrations (1 microg/50 microl), a selective and earlier effect on inner hair cells was observed.

CONCLUSIONS

These results clearly show that significant ototoxicity ensues when sensory cells of the organ of Corti are exposed to pneumolysin (and complete cochlear death when the concentration is high enough). Toxicity is dose-dependent and appears to be site-sensitive. This may have implications for any possible future protective strategies against pneumococcal disease in the ear.

Induction of apoptosis in the vestibule of guinea pigs after middle ear inoculation with lipopolysaccharide (LPS)

OBJECTIVE

During the process of apoptosis, double-stranded DNA is broken into single-stranded DNA (ssDNA) by the action of caspases and caspase activated deoxyribonuclease (CAD). We immunohistochemically examined the apoptotic changes induced by endotoxin in the vestibule of guinea pigs.

METHODS

Lipopolysaccharide (LPS) (5 mg/ml, 0.2 ml), a bacterial endotoxin, was transtympanically injected into the middle ear. 48 h after injection of LPS, animals were sacrificed by intracardiac perfusion of fixative. The temporal bones were then removed and immunohistochemically stained for ssDNA, CAD and caspase 3.

RESULTS

ssDNA was detected after 48 h in the dark cell area of the LPS group, not in the sensory epithelium. CAD was observed both in the dark cell area and the sensory epithelium. Caspase 3 was also detected both in the dark cell area and the sensory epithelium.

CONCLUSION

Our findings suggest that apoptosis is involved in the dysfunction of the vestibule under inflammatory conditions.

Role of mannitol in reducing postischemic changes in distortion-product otoacoustic emissions (DPOAEs): a rabbit model

OBJECTIVES

The aim of this study was to observe the effects of mannitol, administered topically at the round window (RW), on cochlear blood flow (CBF) and distortion-product otoacoustic emission (DPOAE) after repeated episodes of cochlear ischemia.

METHODS

Ten young rabbits were used for this study. Reversible ischemic episodes within the cochlea were induced by directly compressing the internal auditory artery (IAA). CBF was measured using a laser-Doppler (LD) probe positioned at the RW niche. DPOAEs were measured at 4, 8, and 12 kHz geometric mean frequency (GMF) using 60 dB sound pressure level (SPL) primary tone stimuli. In five test ears, mannitol was administered topically at the RW for 30 minutes before the IAA compressions. In five control ears, the IAA compressions were undertaken without application of RW medication. Each ear underwent three 5 minute IAA compressions with a 60 minute rest period between compressions.

RESULTS

In the control animals, it was observed that a progressive reduction in DPOAE level followed each successive IAA compression at all three test frequencies. The reduction in DPOAE amplitudes was consistently greater at the higher test frequencies. In the test rabbits, the RW administration of mannitol resulted in significantly less reduction in DPOAE level measures after repeated IAA compressions. For example, 30 minutes after reperfusion at 12 kHz GMF, DPOAE levels in the control ears were reduced by 1.5, 6.0, and 16 dB, compared with 1.5, 4.0, and 6.0 dB in the mannitol test ears.

CONCLUSIONS

Mannitol appears to exert a protective effect on cochlear function after periods of ischemia. The RW appears to be an efficacious route for topical administration of mannitol into the inner ear.

Sensorineural hearing loss in chronic otitis media

OBJECTIVE

To determine whether chronic suppurative otitis media may cause sensorineural hearing loss.

METHODS

The files of 121 patients with unilateral chronic suppurative otitis media were reviewed in a retrospective study. Air conduction and bone conduction threshold averages were calculated over the speech frequencies (500 Hz, 1,000 Hz, and 2,000 Hz). Thresholds at 4 kHz were examined separately but in a similar way. Multiple linear regression models were used to clarify the relationships between sensorineural hearing loss and chronic otitis media.

RESULTS

Chronic suppurative otitis media was seen to be associated with sensorineural hearing loss. When age and normal side were corrected for, pure-tone threshold and bone conduction threshold at either the speech frequencies or at 4 kHz increased gradually according to the duration of the chronic suppurative otitis media. The threshold shift was more accentuated as age increased. The sensorineural hearing loss at 4 kHz seemed to be higher than that at the speech frequencies.

CONCLUSIONS

The inner ear is vulnerable against chronic suppurative otitis media. Older age increases this vulnerability. The proximity of the sensory cells to the potential source of harm (inflamed middle ear) may mean higher exposure, as reflected by the fact that sensory cells processing higher frequencies are more seriously damaged.

Immunoreactivity for myeloperoxidase (MPO) in the vestibule after the injection of bacterial lipopolysaccharide into the middle ear

OBJECTIVE

In this study, the effect of endotoxin on the vestibule of the ear of guinea pigs was immunohistochemically examined.

METHODS

Bacterial lipopolysaccharide was injected into the middle ear transtympanically. After 48 h, the animals were sacrificed by intracardiac perfusion of fixative; then, the temporal bones were removed and processed for immunohistochemical staining with the anti-myeloperoxidase antibody.

RESULTS

Myeloperoxidase could be detected after 48 h in the sensory epithelium and the dark cell area.

CONCLUSION

It is reported that radical oxygen species, which are cytotoxic, are detected under inflammatory conditions. Our results suggest that myeloperoxidase and reactive oxygen species are involved in vestibular dysfunction under inflammation.

Detection of apoptotic change in the lipopolysaccharide (LPS)-treated cochlea of guinea pigs

This study was undertaken to examine, electrophysiologically and immunohistochemically, the effect of endotoxin on the guinea pig cochlea. A bacterial endotoxin (lipopolysaccharide, LPS, 5 mg/ml, 0.2 ml) was injected into the middle ear trans-tympanically. The electrocochleograms were continuously recorded from before to 48 h after the injection with an electrode inserted into the facial canal. Then, the animals were sacrificed by intracardiac perfusion of a fixative, temporal bones were removed and immunohistochemically stained for single-stranded DNA (ssDNA) and caspase 3 (CPP32). ssDNA was detected at 48 h in the stria vascularis and spiral ligament. CPP32 was observed in the stria vascularis, the spiral ligament and the organ of Corti. The threshold of the compound action potential increased significantly at 48 h in the LPS group. These results suggest that the activation of CPP32 and fragmentation of DNA are involved in the dysfunction of the cochlea observed under inflammatory conditions.

Effects of common topical otic preparations on the morphology of isolated cochlear outer hair cells

Otic drops are commonly used not only for otitis externa but also for otorrhea in the presence of tympanostomy tube or tympanic membrane perforation. Many studies have demonstrated the ototoxicity of common otic preparations such as Cortisporin otic drops. Recent studies have suggested the use of fluoroquinolone antibiotic drops as an alternative owing to their excellent antimicrobial coverage and no ototoxic effect. The purpose of this study was to assess the relative ototoxicity of four common otic preparations by direct exposure to isolated cochlear outer hair cells (OHCs). OHCs from adult chinchilla cochlea were exposed to standard bathing solution (control), Cortisporin, Cipro HC, Ciloxan, and Floxin. The cells were observed using an inverted microscope, and the images recorded in digital still-frame and video, and analyzed on the Image Pro-Plus 3.0 program. As measured by time to cell death and change in morphology of OHCs, Cortisporin was most toxic to OHCs. Among the fluoroquinolone drops, Floxin was more toxic than Ciloxan or Cipro HC.

Changes of the compound action potential (CAP) and the expression of inducible nitric oxide synthase (iNOS/NOS II) in the cochlea under the inflammatory condition(1)

In this study, the effect of endotoxin on the guinea pig cochlea has been examined electrophysiologically and immunohistochemically. Bacterial lipopolysaccharide (LPS, 5 mg/ml, 0.2 ml) was injected into the middle ear trans-tympanically. The electrocochleograms were measured before, immediately upon, and 3, 6 and 12 h after the injection continuously with an electrode inserted into the facial canal. After each measurement, some of the animals were killed with an intracardiac perfusion of fixative, temporal bones were removed and were immunohistochemically examined for inducible nitric oxide synthase (iNOS/NOS II). On serial paraffin section, iNOS could be detected first after 3 h in the lateral wall, the supporting cells of the organ of Corti and in cells of the spiral ganglion and was observed up to 12 h. After the injection of LPS, the threshold of compound action potential became significantly worse after 12 h in the LPS group. These changes became evident first at higher frequency (8 kHz). These results suggest that iNOS-generated NO is involved in the cochlea dysfunction under inflammatory conditions.

Hearing preservation with labyrinthine ablation in otitis media

OBJECTIVES

Iatrogenic fenestration of the inner ear in the presence of otitis media is commonly associated with permanent hearing loss. Hearing can generally be preserved when the vestibular labyrinth is ablated in a controlled manner in noninflamed ears. The purpose of this study was to examine the feasibility of hearing preservation with violation of the inner ear in the presence of middle ear inflammation.

STUDY DESIGN

Prospective and controlled animal model.

METHODS

Otitis media was induced bilaterally in pigmented guinea pigs with transtympanic injection of Streptococcus pneumoniae, nontypeable Haemophilus influenzae, or formalin-killed nontypeable H influenzae. Two to 4 days after injection, the horizontal canal of one ear was transected and sealed. Hearing was tested before and after labyrinthine ablation.

RESULTS

Otitis media was induced in all ears. Bacterial cultures were positive in 19 of 20 S pneumoniae-injected ears, and in 10 of 16 nontypeable H influenzae-injected ears. One week after surgery, elevation of click thresholds (> 15 dB) was encountered in none of the fenestrated or unfenestrated S pneumoniae-infected ears, in two of six unfenestrated and three of six fenestrated nontypeable H influenzae-infected ears, and in one of five killed-nontypeable H influenzae-injected ears both with and without fenestration.

CONCLUSIONS

These data suggest that ablation of a semicircular canal in the presence of middle ear inflammation or infection does not necessarily lead to profound sensorineural hearing loss. Hearing loss associated with iatrogenic violation of the semicircular canals may be more dependent on factors other than the presence of nonspecific middle ear inflammation.

Biological properties of pneumolysin

Pneumolysin is a thiol-activated membrane-damaging toxin produced by Streptococcus pneumoniae. The toxin plays a role in virulence of the pneumococcus in animal models of infection. Pneumolysin has a range of biological activity including the ability to lyse eukaryotic cells and to interfere with the function of cells and soluble molecules of the immune system. The use of purified native and mutant toxin and of isogenic mutants of the pneumococcus expressing altered versions of the toxin has allowed the contribution of the various activities of this multifunctional toxin to virulence to be defined.

Otitis media: the chinchilla model

Streptococcus pneumoniae infection and disease have been modeled in several animal species including infant and adult mice, infant and adult rats, infant Rhesus monkeys, and adolescent and adult chinchillas. Most are models of sepsis arising from intravenous or intraperitoneal inoculation of bacteria, and a few were designed to study disease arising from intranasal infection. Chinchillas provide the only animal model of middle ear pneumococcal infection in which the disease can be produced by very small inocula injected into the middle ear (ME) or intranasally, and in which the disease remains localized to the ME in most cases. This model, developed at the University of Minnesota in 1975, has been used to study pneumococcal pathogenesis at a mucosal site, immunogenicity and efficacy of pneumococcal capsular polysaccharide (PS) vaccine antigens, and the kinetics and efficacy of antimicrobial drugs. Pathogenesis experiments in the chinchilla model have revealed variation in ME virulence among different pneumococcal serotypes, enhancement of ME infection during concurrent intranasal influenza A virus infections, and natural resolution of pneumococcal otitis media (OM) without intervention. Research has explored the relative contribution of pneumococcal and host products to ME inflammation. Pneumococcal cell wall components and pneumolysin have been studied in the model. Host inflammatory responses studied in the chinchilla ME include polymorphonuclear leukocyte oxidative products, hydrolytic enzymes, cytokine and eicosanoid metabolites, and ME epithelial cell adhesion and mucous glycoprotein production. Both clinical (tympanic membrane appearance) and histopathology (ME, Eustachian tube, inner ear) endpoints can be quantified. Immunologic and inflammatory studies have been facilitated by the production of affinity-purified antichinchilla immunoglobulin G (IgG), IgM, and secretory IgA polyclonal antibody reagents, and the identification of cross-reactivity between human and chinchilla cytokines, and between guinea pig and chinchilla C3. Alteration of ME mucosa by pneumococcal neuraminidase and alteration of ME epithelial cell (MEEC) surface carbohydrates during intranasal pneumococcal infection have been demonstrated. Pathogenesis studies have been aided by cultured chinchilla MEEC systems, in which the ability of platelet activating factor and interleukin (IL)-1 beta to stimulate epithelial mucous glycoprotein synthesis has recently been demonstrated. Because chronic OM with effusion is characterized by presence of large amounts of mucous glycoprotein in the ME, pneumococcus may have an important role in both acute and chronic ME disease. Both unconjugated PS and PS-protein-conjugated vaccines are immunogenic after intramuscular administration without adjuvant in chinchillas. Passive protection studies with human hyperimmune immunoglobulin demonstrated that anti-PS IgG alone is capable of protecting the chinchilla ME from direct ME challenge with pneumococci. Active PS immunization studies demonstrated protection following direct ME and intranasal pneumococcal challenge with and without concurrent influenza A virus infection. An attenuated influenza A virus vaccine also showed protection for pneumococcal OM. Antimicrobial treatment of acute OM has been based almost exclusively on empirical drug use and clinical trials without a foundation of ME pharmacokinetics. Studies in the chinchilla model have started to bring a rational basis to drug selection and dosing. Microassays have been developed using high-pressure liquid chromatography for many relevant drugs. Studies have explored the in vivo ME response in pneumococcal OM to antimicrobial drugs at supra- and sub-minimum inhibitory concentration (MIC), the effect of concurrent influenza A virus infection on ME drug penetration, and the effect of treatment on sensorineural hearing loss produced by pneumococcal OM.

What inner ear diseases cause benign paroxysmal positional vertigo?

Benign paroxysmal positional vertigo (BPPV) originating from the posterior semicircular canal (pSCC) is a common vestibular disorder that is easy to diagnose and usually easy to treat. The majority of patients with BPPV have no known inner ear disease; they have "primary" or "idiopathic" BPPV. However, a minority does have objective evidence of an inner ear disease on the same side as the BPPV and this group has "secondary" or "symptomatic" BPPV. Previous publications differ on the prevalence of secondary BPPV and about the types of inner ear diseases capable of causing it. In order to determine what proportion of patients have secondary as opposed to primary BPPV and which inner ear diseases are capable of causing secondary BPPV, we searched our database for the 10-year period from 1988 to 1997 and found a total of 2847 patients with BPPV. Of these, 81 (3%) had definite pSCC-BPPV secondary to an ipsilateral inner ear disease. Sixteen had Menière's disease, 24 had an acute unilateral peripheral vestibulopathy, 12 had a chronic unilateral peripheral vestibulopathy, 21 had chronic bilateral peripheral vestibulopathy and 8 had unilateral sensorineural hearing loss. It seems that any inner ear disease that detaches otoconia and yet does not totally destroy pSCC function can cause BPPV and that a case can be made for audiometry and caloric testing in all patients with BPPV.

Antibiotics in chronic suppurative otitis media: a bacteriologic study

Conservative medical management of chronic suppurative otitis media (CSOM) is an important step in achieving a dry ear. Topical antibiotic ear drops and aural toilet form the mainstay of medical management of noncholesteatomatous CSOM. This study analyzes the causal organisms and their sensitivity to various antibiotics. Out of 382 swabs examined, the major organisms isolated were Pseudomonas aeruginosa (27.2%), followed by Staphylococcus aureus (23.6%). The sensitivity of P. aeruginosa was 100% to ceftazidime, 98.9% to ciprofloxacin, 96.3% to gentamicin, and 95.4% to polymyxin B, whereas the sensitivity of S. aureus was 98.6% to ciprofloxacin, 97.4% to cloxacillin sodium, 96.5% to cotrimoxazole, and 90.7% to gentamicin. Pseudomonas aeruginosa was almost completely resistant to ampicillin (97.6%) and chloramphenicol (96.6%), whereas S. aureus was almost completely resistant to ampicillin (73.8%) and polymyxin B (98.3%). Among the available topical antibiotic preparations for use in the ear, we found that ciprofloxacin and gentamicin are the best choices.

Bacterial cytolysin perturbs round window membrane permeability barrier in vivo: possible cause of sensorineural hearing loss in acute otitis media

The passage of radioiodinated streptolysin-O (SLO) and albumin through the round window membrane (RWM) was studied in vivo. When applied to the middle ear, SLO became quantitatively entrapped in this compartment and no passage to the cochlea occurred. However, flux of radioiodinated albumin through the toxin-damaged RWM was observed. We propose that the passage of noxious macromolecules, such as proteases, from a purulent middle-ear effusion may be facilitated by pore-forming toxins, resulting in cochlear damage and sensorineural hearing loss.