Topical Therapy Failure in Chronic Suppurative Otitis Media is Due to Persister Cells in Biofilms

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

OBJECTIVE

To determine if absorbable gelatin sponge (AGS) can be used to assess the posttympanoplasty microbiome and otic antibiotic exposure.

STUDY DESIGN

Prospective.

SETTING

Tertiary hospital.

METHODS

Patients undergoing tympanoplasty were prospectively enrolled. Intraoperatively, AGS was applied to the medial ear canal/tympanic membrane (TM) for 1 minute after canal incision, then saved for analysis. Ear canals were packed with AGS at the end of surgery. Otic ofloxacin was administered until the first postoperative visit, when AGS was collected. Microbial presence was assessed by culture. Ofloxacin levels were assessed by liquid-chromatography mass-spectrometry.

RESULTS

Fifty-three patients were included. AGS was collected in 92.9% of patients seen within 21 days compared to 70.8% of those seen at 22 to 35 days. At surgery, AGS yielded bacteria and fungi in 81% and 11%, respectively, including Staphylococcus species (55%) and Pseudomonas species (25%). Postoperatively, AGS yielded bacteria in 71% and fungi in 21% at the meatus, (staphylococci 57% and pseudomonas 25%). TM samples yielded bacteria in 69%, fungi in 6%, staphylococci in 53%, and pseudomonas in 19%. Ofloxacin concentration at the meatus was 248 μg/mL (95% confidence interval [CI]: 119-377) and at the TM was 126 μg/mL (95% CI: 58-194). Ofloxacin-resistant colonies were found in 75% of patients.

CONCLUSION

Analysis of AGS is a viable technique for noninvasively studying healing metrics posttympanoplasty, including the microbiome and otic antibiotic exposure. Despite exposure to a high concentration of quinolones, the tympanoplasty wound is far from sterile, which may impact healing outcomes.

Epidemiology of Chronic Suppurative Otitis Media in the United States

OBJECTIVE

This study aimed to evaluate the prevalence, incidence, and associated demographic factors of chronic suppurative otitis media (CSOM), utilizing a nationwide healthcare claims database.

METHODS

This retrospective study utilized outpatient administrative claims data from the IBM MarketScan Research Database from 2007 to 2021. The database (11 246 909 584 claims with 148 147 615 unique patients) includes health data from the private-sector, Medicare/Medicaid, managed care providers, and EMR providers. Included patients had a diagnosis of CSOM based on ICD-9-CM and ICD-10-CM codes. Prevalence and health utilization were estimated by age, gender, and geographic region.

RESULTS

In the United States, the estimated CSOM prevalence and incidence was 0.46% and 0.03%, respectively. Among CSOM patients (n = 679 906), mean age (SD) was 8.1 (15.4) years, and 52.8% were male. Most patients (81.1%) were aged 0 to 10 years. CSOM prevalence was lower in females (OR = 0.64, 95% CI 0.64-0.65, P < .001), less common in older age (OR = 0.94, 95% CI 0.94-0.94, P < .001), and highest in the South region (OR = 2.08, 95% CI 2.06-2.09, P < .001).

CONCLUSION

Our results show CSOM prevalence (0.46%) is similar to other developed countries. CSOM prevalence was highest in those aged 0 to 10 years, in males and in the South region. Of note, prevalence and cost are likely significantly underestimated given limitations in accurate ICD-CM coding and the exclusion of uninsured patients. Further epidemiological studies are warranted to characterize the impact of CSOM on the US healthcare system.

PANEL 3: Otitis media animal models, cell culture, tissue regeneration & pathophysiology

OBJECTIVE

To review and summarize recently published key articles on the topics of animal models, cell culture studies, tissue biomedical engineering and regeneration, and new models in relation to otitis media (OM).

DATA SOURCE

Electronic databases: PubMed, National Library of Medicine, Ovid Medline.

REVIEW METHODS

Key topics were assigned to the panel participants for identification and detailed evaluation. The PubMed reviews were focused on the period from June 2019 to June 2023, in any of the objective subject(s) or keywords listed above, noting the relevant references relating to these advances with a global overview and noting areas of recommendation(s). The final manuscript was prepared with input from all panel members.

CONCLUSIONS

In conclusion, ex vivo and in vivo OM research models have seen great advancements in the past 4 years. From the usage of novel genetic and molecular tools to the refinement of in vivo inducible and spontaneous mouse models, to the introduction of a wide array of reliable middle ear epithelium (MEE) cell culture systems, the next five years are likely to experience exponential growth in OM pathophysiology discoveries. Moreover, advances in these systems will predictably facilitate rapid means for novel molecular therapeutic studies.

ISOM 2023 research Panel 4 - Diagnostics and microbiology of otitis media

OBJECTIVES

To identify and review key research advances from the literature published between 2019 and 2023 on the diagnosis and microbiology of otitis media (OM) including acute otitis media (AOM), recurrent AOM (rAOM), otitis media with effusion (OME), chronic suppurative otitis media (CSOM) and AOM complications (mastoiditis).

DATA SOURCES

PubMed database of the National Library of Medicine.

REVIEW METHODS

All relevant original articles published in Medline in English between July 2019 and February 2023 were identified. Studies that were reviews, case studies, relating to OM complications (other than mastoiditis), and studies focusing on guideline adherence, and consensus statements were excluded. Members of the panel drafted the report based on these search results.

MAIN FINDINGS

For the diagnosis section, 2294 unique records screened, 55 were eligible for inclusion. For the microbiology section 705 unique records were screened and 137 articles were eligible for inclusion. The main themes that arose in OM diagnosis were the need to incorporate multiple modalities including video-otoscopy, tympanometry, telemedicine and artificial intelligence for accurate diagnoses in all diagnostic settings. Further to this, was the use of new, cheap, readily available tools which may improve access in rural and lowmiddle income (LMIC) settings. For OM aetiology, PCR remains the most sensitive method for detecting middle ear pathogens with microbiome analysis still largely restricted to research use. The global pandemic response reduced rates of OM in children, but post-pandemic shifts should be monitored.

IMPLICATION FOR PRACTICE AND FUTURE RESEARCH

Cheap, easy to use multi-technique assessments combined with artificial intelligence and/or telemedicine should be integrated into future practice to improve diagnosis and treatment pathways in OM diagnosis. Longitudinal studies investigating the in-vivo process of OM development, timings and in-depth interactions between the triad of bacteria, viruses and the host immune response are still required. Standardized methods of collection and analysis for microbiome studies to enable inter-study comparisons are required. There is a need to target underlying biofilms if going to effectively prevent rAOM and OME and possibly enhance ventilation tube retention.

Overcoming barriers: a review on innovations in drug delivery to the middle and inner ear

Despite significant advances in the development of therapeutics for hearing loss, drug delivery to the middle and inner ear remains a challenge. As conventional oral or intravascular administration are ineffective due to poor bioavailability and impermeability of the blood-labyrinth-barrier, localized delivery is becoming a preferable approach for certain drugs. Even then, localized delivery to the ear precludes continual drug delivery due to the invasive and potentially traumatic procedures required to access the middle and inner ear. To address this, the preclinical development of controlled release therapeutics and drug delivery devices have greatly advanced, with some now showing promise clinically. This review will discuss the existing challenges in drug development for treating the most prevalent and damaging hearing disorders, in particular otitis media, perforation of the tympanic membrane, cholesteatoma and sensorineural hearing loss. We will then address novel developments in drug delivery that address these including novel controlled release therapeutics such as hydrogel and nanotechnology and finally, novel device delivery approaches such as microfluidic systems and cochlear prosthesis-mediated delivery. The aim of this review is to investigate how drugs can reach the middle and inner ear more efficiently and how recent innovations could be applied in aiding drug delivery in certain pathologic contexts.

Eradication of Bacterial Persister Cells By Leveraging Their Low Metabolic Activity Using Adenosine Triphosphate Coated Gold Nanoclusters

Bacteria first develop tolerance after antibiotic exposure; later genetic resistance emerges through the population of tolerant bacteria. Bacterial persister cells are the multidrug-tolerant subpopulation within an isogenic bacteria culture that maintains genetic susceptibility to antibiotics. Because of this link between antibiotic tolerance and resistance and the rise of antibiotic resistance, there is a pressing need to develop treatments to eradicate persister cells. Current anti persister cell strategies are based on the paradigm of "awakening" them from their low metabolic state before attempting eradication with traditional antibiotics. Herein, we demonstrate that the low metabolic activity of persister cells can be exploited for eradication over their metabolically active counterparts. We engineered gold nanoclusters coated with adenosine triphosphate (AuNC@ATP) as a benchmark nanocluster that kills persister cells over exponential growth bacterial cells and prove the feasibility of this new concept. Finally, using AuNC@ATP as a new research tool, we demonstrated that it is possible to prevent the emergence of antibiotic-resistant superbugs with an anti-persister compound. Eradicating persister cells with AuNC@ATP in an isogenic culture of bacteria stops the emergence of superbug bacteria mediated by the sub-lethal dose of conventional antibiotics. Our findings lay the groundwork for developing novel nano-antibiotics targeting persister cells, which promise to prevent the emergence of superbugs and prolong the lifespan of currently available antibiotics.

Influence of CX3CR1 Deletion on Cochlear Hair Cell Survival and Macrophage Expression in Chronic Suppurative Otitis Media

OBJECTIVE

Our objective was to determine whether the receptor CX3CR1 is necessary for the recruitment of macrophages to the cochlea in chronic suppurative otitis media (CSOM) and if its deletion can prevent hair cell loss in CSOM.

BACKGROUND

CSOM is a neglected disease that afflicts 330 million people worldwide and is the most common cause of permanent hearing loss among children in the developing world. It is characterized by a chronically discharging infected middle ear. We have previously demonstrated that CSOM causes macrophage associated sensory hearing loss. The receptor CX3CR1 is expressed on macrophages, which have been shown to be increased at the time point of outer hair cell (OHC) loss in CSOM.

METHODS

In this report, we examine the influence of CX3CR1 deletion (CX3CR1-/-) in a validated model of Pseudomonas aeruginosa (PA) CSOM.

RESULTS

The data show no difference in OHC loss between the CX3CR1-/- CSOM group and CX3CR1+/+ CSOM group (p = 0.28). We observed partial OHC loss in the cochlear basal turn, no OHC loss in the middle and apical turns in both CX3CR1-/- and CX3CR1+/+ CSOM mice at 14 days after bacterial inoculation. No inner hair cell (IHC) loss was found in all cochlear turns in all groups. We also counted F4/80 labeled macrophages in the spiral ganglion, spiral ligament, stria vascularis and spiral limbus of the basal, middle, and apical turn in cryosections. We did not find a significant difference in the total number of cochlear macrophages between CX3CR1-/- mice and CX3CR1+/+ mice (p = 0.97).

CONCLUSION

The data did not support a role for CX3CR1 macrophage associated HC loss in CSOM.

Povidone-Iodine Fails to Eradicate Chronic Suppurative Otitis Media and Demonstrates Ototoxic Risk in Mice

HYPOTHESIS

Commercially available povidone-iodine solution can eliminate biofilms and persister cells rapidly in in vivo achievable concentrations without inducing ototoxicity.

BACKGROUND

Chronic suppurative otitis media (CSOM) is a substantial global problem. Current treatment options often induce a temporary remission without leading to a permanent cessation of symptoms secondary to the treatments' inability to eliminate persister cells. Povidone-iodine has been shown to be able to clear biofilm and planktonic cells in in vitro assays, but there are reports of ototoxic effects limiting its clinical utility.

METHODS

Bacterial and biofilm growth with quantification by spectrophotomer, murine auditory brainstem response (ABR), and distortion product otoacoustic emissions, immunohistochemistry, in vivo povidone-iodine treatment of murine CSOM, persister cell assay.

RESULTS

Commercially available 10% povidone-iodine solution is able to completely eradicate multiple clinical strains of Pseudomonas aeruginosa and Staphylococcus aureus in vitro with 10 minutes of exposure. Mice that have received a transtympanic injection of 1% povidone-iodine solution did not have significantly different auditory brainstem response or distortion product otoacoustic emission results compared with the control. Mice that received a povidone-iodine scrub or 10% povidone-iodine solution had significantly worsened hearing (25- and 13-dB increase in threshold, respectively; p < 0.05). In vivo CSOM infection recurred in all mice after the completion of treatment with 10% povidone-iodine solution, and there was no improvement in the bacterial load after treatment, indicating in vivo failure of therapy.

CONCLUSION

Povidone-iodine solution is effective at eliminating biofilm and persister cells in vitro at in vivo achievable concentrations but fails in vivo most likely because of kinetics of distribution in vivo. Even if drug distribution could be improved, the therapeutic window is likely to be too small given that the diluted solution does not have ototoxic potential, whereas while the scrub variant, which contains detergents, and the undiluted solution are ototoxic after a single treatment.

Chronic suppurative otitis media causes macrophage-associated sensorineural hearing loss

Background

Chronic suppurative otitis media (CSOM) is the most common cause of permanent hearing loss in children in the developing world. A large component of the permanent hearing loss is sensory in nature and our understanding of the mechanism of this has so far been limited to post-mortem human specimens or acute infection models that are not representative of human CSOM. In this report, we assess cochlear injury in a validated Pseudomonas aeruginosa (PA) CSOM mouse model.

Methods

We generated persisters (PCs) and inoculated them into the mouse middle ear cavity. We tracked infection with IVIS and detected PA using RT-PCR. We assessed cochlear damage and innate immunity by Immunohistochemistry. Finally, we evaluated cytokines with multiplex assay and quantitative real-time PCR.

Results

We observed outer hair cell (OHC) loss predominantly in the basal turn of the cochlear at 14 days after bacterial inoculation. Macrophages, not neutrophils are the major immune cells in the cochlea in CSOM displaying increased numbers and a distribution correlated with the observed cochlear injury. The progression of the morphological changes suggests a transition from monocytes into tissue macrophages following infection. We also show that PA do not enter the cochlea and live bacteria are required for cochlear injury. We characterized cytokine activity in the CSOM cochlea.

Conclusions

Taken together, this data shows a critical role for macrophages in CSOM-mediated sensorineural hearing loss (SNHL).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02585-w.

Anti-persister and Anti-biofilm Activity of Self-Assembled Antimicrobial Peptoid Ellipsoidal Micelles

Although persister cells are the root cause of resistance development and relapse of chronic infections, more attention has been focused on developing antimicrobial agents against resistant bacterial strains than on developing anti-persister agents. Frustratingly, the global preclinical antibacterial pipeline does not include any anti-persister drug. Therefore, the central point of this work is to explore antimicrobial peptidomimetics called peptoids (sequence-specific oligo-N-substituted glycines) as a new class of anti-persister drugs. In this study, we demonstrate that one particular antimicrobial peptoid, the sequence-specific pentamer TM5, is active against planktonic persister cells and sterilizes biofilms formed by both Gram-negative and Gram-positive bacteria. Moreover, we demonstrate the potential of TM5 to inhibit cytokine production induced by lipopolysaccharides from Gram-negative bacteria. We anticipate that this work can pave the way to the development of new anti-persister agents based on antimicrobial peptoids of this class to simultaneously help address the crisis of bacterial resistance and reduce the occurrence of the relapse of chronic infections.

Gold nanocluster adjuvant enables the eradication of persister cells by antibiotics and abolishes the emergence of resistance

Persister cells are responsible for relapses of infections common in cystic fibrosis and chronic suppurative otitis media (CSOM). Yet, there are no Food and Drug Administration (FDA) approved antibiotics to eradicate persister cells. Frustratingly, the global preclinical bacterial pipeline does not contain antibacterial agents targeting persister cells. Therefore, we report a nontraditional antimicrobial chemotherapy strategy based on gold nanoclusters adjuvant to eradicate persister cells by existing antibiotics belonging to that different class. Compared to killing with antibiotics alone, combining antibiotics and AuNC@CPP sterilizes persister cells and biofilms. Enhanced killing of up to 4 orders of magnitude in a validated mouse model of CSOM with Pseudomonas aeruginosa infection was observed when combining antibiotics and AuNC@CPP, informing a potential approach to improve the treatment of CSOM. We established that the mechanism of action of AuNC@CPP is due to disruption of the proton gradient and membrane hyperpolarization. The method presented here could compensate for the lack of new antibiotics to combat persister cells. This method could also benefit the current effort to slow resistance development because AuNC@CPP abolished the emergence of drug-resistant strains induced by antibiotics.

Survey on phenotypic resistance in Enterococcus faecalis: comparison between the expression of biofilm-associated genes in Enterococcus faecalis persister and non-persister cells

BACKGROUND

Phenotypic resistance is considered as a serious therapeutic challenge for which a definitive remedy has not been discovered yet. Biofilm and persister cell formation are two well-studied phenotypic resistance phenomena, leading to the recalcitrance and relapse of different types of chronic infections. The presence of persister cells in biofilm structures seems to be one of the main factors contributing to the relapse of infections and treatment failure. Given the dormant and inert nature of persister cells, they can be easy targets for the immune system factors. Biofilm formation can be a survival strategy for the defenseless persister cells. Thus, this study was aimed to evaluate the expression of biofilm-associated genes in Enterococcus faecalis persister and non-persister cells.

METHODS

Vancomycin susceptibility and biofilm formation ability were investigated among 95 E. faecalis clinical isolates using microtiter broth dilution and microtiter plate assays, respectively. PCR was used to determine the presence of biofilm-related genes (gelE, esp, and agg) among the vancomycin-susceptible, biofilm producer E. faecalis isolates (91 isolates). Minimum bactericidal concentration for biofilms (MBCB) were determined for vancomycin using the MTP assay. Bacterial persister assay was performed using an enzymatic lysis assay. Finally, the expression of biofilm-related genes was compared between the persister and non-persister isolates of E. faecalis using real-time qPCR.

RESULTS

E. faecalis isolates showed a high level of susceptibility (95.8%) to vancomycin (MIC < 1 µg/mL). The gelE, esp, and agg genes were found in 91 (100%), 72 (79.12), and 74 (81.32) of the isolates, respectively. All the E. faecalis isolates were tolerant to vancomycin in the biofilm condition, showing a MBCB of > 2500 µg/mL. Based on the enzymatic lysis assay, only 3 isolates, out of the 91, had the ability to form persister cells. The expression of biofilm-associated genes was higher among the persister compared to non-persister E. faecalis isolates.

CONCLUSIONS

Biofilm-associated persister cells indicated a high vancomycin tolerance compared to non-persister cells. Moreover, persister isolates showed a higher tendency for biofilm formation and a higher expression level of the biofilm-associated genes, compared to non-persister isolates.

Long-Term Health Utilization and Outcomes in Chronic Suppurative Otitis Media

OBJECTIVE

To report health utilization patterns and outcomes of medical and surgical management in patients with chronic suppurative otitis media (CSOM).

STUDY DESIGN

Retrospective cohort.

SETTING

Academic otology clinic.

METHODS

This study included 175 patients with CSOM with a first clinic visit at our institution between March 2011 and November 2016. All patients displayed a diagnosis of CSOM by International Classification of Diseases code, had at least 1 episode of active CSOM (defined as perforation with otorrhea), and had a documented history of chronic ear infections. The mean age was 49.5 ± 1.5 years, 53% were female, and mean follow-up time was 3.5 ± 0.3 years.

RESULTS

Patients had an average of 9.5 ± 0.5 otology visits, 4.7 ± 0.4 prescriptions, and 1.7 ± 0.1 surgeries, with estimated per patient cost ranging from $3927 to $20,776. Under medical management, 69% of patients displayed recurrence of disease, with a median time to recurrence of 4 months. For tympanoplasty and tympanomastoidectomy, median time to recurrence was similar at 5 and 7 years, respectively (P = .73). At the most recent visit, the prevalence of all patients with CSOM displaying moderate or worse sensorineural hearing loss (SNHL) was 41%.

CONCLUSIONS

CSOM represents a major public health issue with high health care utilization and associated costs. Surgery is superior to medical therapy for achieving short- to medium-term inactive disease. Patients with CSOM display a high SNHL burden.