Tea tree oil: in vitro efficacy in otitis externa

A review on antimicrobial strategies in mitigating biofilm-associated infections on medical implants

Biomedical implants are crucial in providing support and functionality to patients with missing or defective body parts. However, implants carry an inherent risk of bacterial infections that are biofilm-associated and lead to significant complications. These infections often result in implant failure, requiring replacement by surgical restoration. Given these complications, it is crucial to study the biofilm formation mechanism on various biomedical implants that will help prevent implant failures. Therefore, this comprehensive review explores various types of implants (e.g., dental implant, orthopedic implant, tracheal stent, breast implant, central venous catheter, cochlear implant, urinary catheter, intraocular lens, and heart valve) and medical devices (hemodialyzer and pacemaker) in use. In addition, the mechanism of biofilm formation on those implants, and their pathogenesis were discussed. Furthermore, this article critically reviews various approaches in combating implant-associated infections, with a special emphasis on novel non-antibiotic alternatives to mitigate biofilm infections.

The biofilm characteristics and management of skin flap infection following cochlear implantation

Objective

This study aims to assess the frequency, bacteriology, biofilm characteristics and management of skin flap infection (SFI) following cochlear implantation (CI).

Methods

The study enrolled 1,251 patients receiving CI in the First Affiliated Hospital of Fujian Medical University between August 2001 and March 2021. Scanning electron microscopy (SEM) was utilised to characterise the aetiology of infection. A proposed classification system was applied to optimise treatments for post-operative skin flap infection.

Results

After CI, SFI was reported in 16 patients (1.28%) and occurred more frequently in patients under 6 years of age. Of all SFI cases Staphylococcus aureus was the most common pathogen for flap infection, with 8 cases (50%) and bacterial biofilm was evident within the jelly-like substance on the surface of implanted devices in SFI patients. A two-stage classification was proposed to optimise the treatment schemes. Conservative therapy was recommended for stage I cases and surgical treatment for stage II patients.

Conclusions

Paediatric patients are more susceptible to SFI after CI, which may be attributed to the formation of bacterial biofilm. The proposed classification can facilitate the management of SFI.

In vitro antibacterial activity of the manuka essential oil from Leptospermum scoparium combined with Tris-EDTA against Gram-negative bacterial isolates from dogs with otitis externa

BACKGROUND

The increasing prevalence of antimicrobial resistance among bacteria in dogs with otitis externa has led to a need for novel therapeutic agents.

HYPOTHESIS/OBJECTIVE

To examine the antibacterial effects of manuka oil combined with ethylenediaminetetraacetic acid-tromethamine (Tris-EDTA) against Gram-negative bacteria isolates from dogs with otitis externa.

METHODS AND MATERIALS

A total of 53 clinical isolates including Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae ssp. pneumoniae and Proteus mirabilis. Antimicrobial susceptibility was determined using disk diffusion; the minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of manuka essential oil, with or without Tris-EDTA, were investigated.

RESULTS

A total of 44 isolates were resistant to at least one antibiotic and 19 strains were multidrug-resistant, with resistance to at least one agent in three or more antimicrobial classes. The MICs and MBCs of manuka oil alone were ≥1% (v/v) and ≥2% (v/v), respectively. There was no antimicrobial effect of Tris-EDTA (1.125:0.3 mg/mL) without manuka oil. However, the combination of manuka oil with Tris-EDTA significantly decreased the MICs (ranging from 0.06% to 0.5%, v/v; P < 0.001) and MBCs (ranging from 0.06% to 1%, v/v; P < 0.001). There also was no significant difference between multidrug-resistant and nonresistant bacterial isolates in terms of the antimicrobial activity of manuka oil with Tris-EDTA.

CONCLUSIONS AND CLINICAL IMPORTANCE

The study findings suggest that manuka oil, especially when combined with Tris-EDTA, may be a promising alternative therapeutic option for Gram-negative otic pathogens. Clinical studies are needed to assess potential for in vivo ototoxic effects and efficacy.

In vitro and in vivo efficacy of tea tree essential oil for bacterial and yeast ear infections in dogs

ABSTRACT: Otitis externa is a common complaint in dogs. Bacteria and yeasts are commonly involved and may perpetuate inflammatory reactions inside the ear canal. Otoscopy, cytological examination of secretion and microbiological culture embody forms of diagnosis. Cytology also has great use in accessing treatment evolution. Therapy usually consists of cleaning ear canals and subsequent use of antibiotics or antifungal products. As some of them may cause hypersensitivity and even ototoxicity, searching for new pharmacological bases is currently necessary and justifies this study, which aimed to evaluate in vitro and in vivo efficacy of tea tree essential oil for bacterial and yeast ear infections in dogs. Twenty-eight dogs from a particular shelter in Cuiabá (Mato Grosso, Brazil), presenting clinical signs of otitis externa, were enrolled in this clinical trial. In all of them, clinical and cytological evaluations, as well as culture and susceptibility testing of the affected ears were carried out. From each dog, one ear was treated with 5% tea tree essential oil lotion and the other with standard otic formulation, according to the type of infection (bacterial, yeast or both). In vitro susceptibility testings of all ear cultures, to the same drugs used in treatment, were also carried out. Culture results showed 62.5% bacterial and fungal infection, 33.9% bacterial infection and 3.6% fungal infection, from the 56 ear samples collected. The most common microorganisms isolated were Staphylococcus intermedius, Staphylococcus aureus, Proteus mirabilis and Malassezia pachydermatis. Gram-positive bacteria were susceptible to gentamycin in 60.5% and resistant in 16.3% of the samples. Five percent tea tree essential oil formulation produced a 5mm clear zone of inhibition around the disks in one of the 63 samples evaluated. Pure (100%) tea tree essential oil formulation produced a 10mm clear zone of inhibition around the disks in four of the 63 samples evaluated, a 9mm zone in three samples, an 8mm zone in 16 samples, a 7mm zone in seven samples, a 6mm zone in two samples and there was no clear zone in 31 samples. Inhibition zones were produced by strains of Staphylococcus intermedius, Staphylococcus hyicus, Corynebacterium sp., Proteus mirabilis and Enterobacter sp. tea tree essential oil ear solution significantly induced remission of clinical signs both in bacterial and yeast ear infections. It also reduced as much Malassezia pachydermatis ear infection as the nystatin solution used in this study, while gentamycin solution showed better antibacterial effect. More studies should be conducted to evaluate in vitro diffusion properties of tea tree essential oil. Good antimicrobial spectrum and the absence of adverse reactions confirm the importance of developing a tea tree formulation as an alternative therapy for ear infections in dogs.

Salvaging cochlear implant after wound infection: Well worth a try

BACKGROUND

Cochlear implant (CI)-related wound infections are known to happen even years after the implant procedure and present a challenging clinical situation. Due to the formation of biofilm on the implant surface such infections are difficult to eradicate. Invariably explantation of the device is required for wound healing.

METHOD

A 10-year-old patient presented with recurrent CI-related wound infection 8 years after implantation. The implant was salvaged with wound debridement and treating it with tea tree oil which is known for its biofilm eradicating properties. It was then covered with double layer of vascularised soft tissue. Combination of intravenous vancomycin and oral rifampicin known for their efficacy in biofilm-related infection was also used.

RESULTS

The implant could be salvaged using this novel technique of treating the implant with a biofilm eradicating agent, wound debridement, double layer vascularised soft tissue cover, and long-term antibiotics.

CONCLUSION

Agents having anti-biofilm activity when used in conjunction with surgical debridement and judicious antimicrobial therapy can be used for salvaging the implant and limiting the morbidity associated with these infections.

Antibacterial and Antifungal Activity of Essential Oils against Pathogens Responsible for Otitis Externa in Dogs and Cats

Background: Essential oils (EOs) are recommended by some veterinarians to treat otitis externa in pets, but data about their efficacy in scientific literature are very scant. Methods: Nine commercial EOs, from roman chamomile (Anthemis nobilis L.), star anise (Illicium verum), lavender (Lavandula hybrida), litsea (Litsea cubeba (Lour.) Pers.), basil (Ocimum basilicum L.), oregano (Origanum vulgare L. subsp. hirticum), rosemary (Rosmarinus officinalis L.), clary sage (Salvia sclarea L.), and thyme (Thymus vulgaris L.) were tested against bacterial and fungal pathogens previously isolated from dogs and cats with otitis externa. In particular, the analyses were carried out against Pseudomonas aeruginosa, Staphylococcus aureus, Staphylococcus pseudointermedius, Aspergillus niger, Aspergillus fumigatus, Aspergillus terreus, Candida albicans, Candida tropicalis, Trichosporon sp., and Rhodotorula sp. Results:O. vulgare and S. sclarea showed superior antibacterial activity, even if not against all the strains. Trichosporon sp., C. albicans, and A. terreus were insensitive to most Eos, while other yeasts and molds showed different degrees of sensitivity. In particular, most fungi were inhibited by O. vulgare and R. officinalis. Conclusions: The obtained results suggest that some EOs could be included in treatment as an alternative therapeutic option in bacterial otitis complicated by fungi, in association with conventional drugs.

A case report of a cochlear implant infection - A reason to explant the device?

CLINICAL PRESENTATION

Case history of a paediatric patient with a cochlear implant and a surgical site infection that developed as a result of acute otitis media is presented.

INTERVENTION

After conservative management including wound debridement it was decided to explant a functioning device.

OBJECTIVE AND IMPORTANCE

In a number of cases, it is necessary to remove the infected albeit functioning device, especially in the event of formation of the biofilm has occurred. It is necessary to review and evaluate the methods with which these major complications are routinely managed with the aim to increase the survival ratio for the implanted device.

Assessment of ototoxicity of tea tree oil in a chinchilla animal model

OBJECTIVE

The aim of the present study is to examine the effects of tea tree oil on hearing function and cochlear morphology after intratympanic administration in a chinchilla animal model.

METHODS

Nine chinchillas received intratympanic injection of 3% tea tree oil dissolved in olive oil in one ear, whereas the contralateral control ear received olive oil only. Outcome measures included auditory brainstem responses conducted before treatment and at 10 days and 30 days following the injection. Post-mortem cochlear morphology was assessed using scanning electron microscopy.

RESULTS

At 10 and 30 days following the injection, there was no significant change in auditory brain response thresholds at 8, 16, 20 or 25kHz. Scanning electron microscopy imaging showed no damage to auditory hair cells.

CONCLUSION

Tea tree oil (3%) does not appear to be ototoxic in a chinchilla animal model. Future preclinical and clinical studies are required to establish the effectiveness of TTO in treating otitis.

Clinical Practice Guideline

Objective

This clinical practice guideline is an update and replacement for an earlier guideline published in 2006 by the American Academy of Otolaryngology—Head and Neck Surgery Foundation. This update provides evidence-based recommendations to manage acute otitis externa (AOE), defined as diffuse inflammation of the external ear canal, which may also involve the pinna or tympanic membrane. The variations in management of AOE and the importance of accurate diagnosis suggest a need for updating the clinical practice guideline. The primary outcome considered in this guideline is clinical resolution of AOE.

Purpose

The primary purpose of the original guideline was to promote appropriate use of oral and topical antimicrobials for AOE and to highlight the need for adequate pain relief. An updated guideline is needed because of new clinical trials, new systematic reviews, and the lack of consumer participation in the initial guideline development group. The target patient is aged 2 years or older with diffuse AOE. Differential diagnosis will be discussed, but recommendations for management will be limited to diffuse AOE, which is almost exclusively a bacterial infection. This guideline is intended for primary care and specialist clinicians, including otolaryngologists–head and neck surgeons, pediatricians, family physicians, emergency physicians, internists, nurse practitioners, and physician assistants. This guideline is applicable in any setting in which patients with diffuse AOE would be identified, monitored, or managed.

Action Statements

The development group made strong recommendations that (1) clinicians should assess patients with AOE for pain and recommend analgesic treatment based on the severity of pain and (2) clinicians should not prescribe systemic antimicrobials as initial therapy for diffuse, uncomplicated AOE unless there is extension outside the ear canal or the presence of specific host factors that would indicate a need for systemic therapy. The development group made recommendations that (1) clinicians should distinguish diffuse AOE from other causes of otalgia, otorrhea, and inflammation of the external ear canal; (2) clinicians should assess the patient with diffuse AOE for factors that modify management (nonintact tympanic membrane, tympanostomy tube, diabetes, immunocompromised state, prior radiotherapy); (3) clinicians should prescribe topical preparations for initial therapy of diffuse, uncomplicated AOE; (4) clinicians should enhance the delivery of topical drops by informing the patient how to administer topical drops and by performing aural toilet, placing a wick, or both, when the ear canal is obstructed; (5) clinicians should prescribe a non-ototoxic preparation when the patient has a known or suspected perforation of the tympanic membrane, including a tympanostomy tube; and (6) clinicians should reassess the patient who fails to respond to the initial therapeutic option within 48 to 72 hours to confirm the diagnosis of diffuse AOE and to exclude other causes of illness.

Assessment and management of chronic otitis externa

PURPOSE OF REVIEW

Chronic otitis externa (COE) remains a frustrating problem for both patient and physician. The end stage of disease, medial fibrosing otitis externa, is very challenging to repair. New and old therapies and promising approaches to the treatment of this often recalcitrant problem are presented in this review.

RECENT FINDINGS

Tacrolimus, a nonsteroidal immunosuppressant, and fluocinolone acetonide oil 0.01%, a medium-high potency steroid preparation, may offer additional therapeutic options in the struggle against this inflammatory ear canal/skin condition of often unknown cause. Relative potencies of many steroid preparations will be presented along with several treatment strategies for controlling COE. Underlying autoimmune problems such as Sjögren's disease, sarcoidosis, and amyloidosis must be searched and, if present, addressed and treated for resolution of symptoms. Cutting edge therapies, including use of bacteriophages and inflammatory proteases, will also be reviewed.

SUMMARY

No single therapy will be successful for every patient with COE. The search for an underlying cause, the removal of all possible irritants to the ear canal skin (e.g. Q-tips, water), debridement, and both topical and occasionally, systemic therapy will control (not cure …) the disease process in the vast majority of patients.

Treatment of a cochlear implant biofilm infection: a potential role for alternative antimicrobial agents

OBJECTIVE

This study aimed to investigate antimicrobial treatment of an infected cochlear implant, undertaken in an attempt to salvage the infected device.

METHODS

We used the broth microdilution method to assess the susceptibility of meticillin-sensitive Staphylococcus aureus isolate, cultured from an infected cochlear implant, to common antimicrobial agents as well as to novel agents such as tea tree oil. To better simulate in vivo conditions, where bacteria grow as microcolonies encased in glycocalyx, the bactericidal activity of selected antimicrobial agents against the isolate growing in biofilm were also compared.

RESULTS

When grown planktonically, the S aureus isolate was susceptible to 17 of the 18 antimicrobials tested. However, when grown in biofilm, it was resistant to all conventional antimicrobials. In contrast, 5 per cent tea tree oil completely eradicated the biofilm following exposure for 1 hour.

CONCLUSION

Treatment of infected cochlear implants with novel agents such as tea tree oil could significantly improve salvage outcome.

The influence of essential oils on the process of wound healing: a review of the current evidence

This paper reports on a literature review of evidence on the influence of essential oils on wound healing and their potential application in clinical practice. It focuses mainly on tea tree, lavender, chamomile, thyme and ocimum oils.

Clinical practice guideline: acute otitis externa

OBJECTIVE

This guideline provides evidence-based recommendations to manage diffuse acute otitis externa (AOE), defined as generalized inflammation of the external ear canal, which may also involve the pinna or tympanic membrane. The primary purpose is to promote appropriate use of oral and topical antimicrobials and to highlight the need for adequate pain relief.

STUDY DESIGN

In creating this guideline, the American Academy of Otolaryngology-Head and Neck Surgery Foundation (AAO-HNSF) selected a development group representing the fields of otolaryngology-head and neck surgery, pediatrics, family medicine, infectious disease, internal medicine, emergency medicine, and medical informatics. The guideline was created with the use of an explicit, a priori, evidence-based protocol.

RESULTS

The group made a strong recommendation that management of AOE should include an assessment of pain, and the clinician should recommend analgesic treatment based on the severity of pain. The group made recommendations that clinicians should: 1) distinguish diffuse AOE from other causes of otalgia, otorrhea, and inflammation of the ear canal; 2) assess the patient with diffuse AOE for factors that modify management (nonintact tympanic membrane, tympanostomy tube, diabetes, immunocompromised state, prior radiotherapy); and 3) use topical preparations for initial therapy of diffuse, uncomplicated AOE; systemic antimicrobial therapy should not be used unless there is extension outside of the ear canal or the presence of specific host factors that would indicate a need for systemic therapy. The group made additional recommendations that: 4) the choice of topical antimicrobial therapy of diffuse AOE should be based on efficacy, low incidence of adverse events, likelihood of adherence to therapy, and cost; 5) clinicians should inform patients how to administer topical drops, and when the ear canal is obstructed, delivery of topical preparations should be enhanced by aural toilet, placing a wick, or both; 6) when the patient has a tympanostomy tube or known perforation of the tympanic membrane, the clinician should prescribe a nonototoxic topical preparation; and 7) if the patient fails to respond to the initial therapeutic option within 48 to 72 hours, the clinician should reassess the patient to confirm the diagnosis of diffuse AOE and to exclude other causes of illness. And finally, the panel compiled a list of research needs based on limitations of the evidence reviewed.

CONCLUSION

This clinical practice guideline is not intended as a sole source of guidance in evaluating patients with AOE. Rather, it is designed to assist clinicians by providing an evidence-based framework for decision-making strategies. It is not intended to replace clinical judgment or establish a protocol for all individuals with this condition and may not provide the only appropriate approach to the diagnosis and management of this problem.

SIGNIFICANCE

This is the first, explicit, evidence-based clinical practice guideline on acute otitis externa, and the first clinical practice guideline produced independently by the AAO-HNSF.