Abstract
Objective
The aim of this study was to determine the presence and nature of bacterial flora on hearing aids and the ears of this population. We wonder if the microbiology of the ears with hearing aid wearing differs from the other ear.
Setting
Tertiary referral center.
Design
A prospective, clinical study.
Subjects and methods
Three samples were taken, one from the surface of the hearing aid’s ear mold; one from the hearing aid-wearing ear canal and the last one from the ear without hearing aid. Samples were cultured to determine qualitatively and quantitatively the pathogenic microorganisms present.
Results
A total of 123 samples, obtained from 41 hearing aid users, were analyzed. Methicillin-resistant coagulase-negative staphylococci, methicillin-susceptible Staphylococcus aureus , methicillin-resistant S. aureus , Pseudomonas aeruginosa , Escherichia coli , Acinetobacter species, Staphylococcus auricularis , and Stenotrophomonas maltophilia were identified organisms.
Conclusions
We identified unexpected microorganisms both on hearing aids and hearing aid using ears. This study demonstrates that using hearing aid alters the ear canal flora. To avoid otitis externa, it is important to use an appropriate hygiene routine to clean and disinfect hearing aids and ear molds.
1
Introduction
Hearing aids have been identified as a potential source of microbial transmission .The reported annual incidence of acute otitis externa varies between 1:100 and 1:250 in the general population, with a seasonal and regional variability . Several microbiological analyses characterize Pseudomonas aeruginosa as the most common causative bacteria in acute otitis externa, followed by Staphylococcus aureus .
The use of hearing aid ear molds is a predisposing factor to the development of otitis externa. Aside from the increased humidity that results from wearing a hearing aid ear mold, it has been postulated that the presence of polymicrobial flora in ear molds may be an etiological agent for the development of otitis externa in humans. Some of the microorganisms are consistent with what is normally found in the ear but many of the recovered microorganisms are not and are considered unhygienic.
The ear is a moist place and hearing aids are worn in the ear; bacteria and other microorganisms can easily grow on hearing aid surfaces. A wide range of bacteria and fungi have been found to grow on hearing aid surfaces. Recent researches related to hearing aid hygiene has shed new light on how patients need to properly clean their hearing aids and/or earmolds.
Microorganisms may be transmitted in a variety of ways; contact transmission remains the most common means of cross-contamination and possible disease transmission. Contact transmission occurs when a clinician or patient touches another individual or object; removing a hearing aid from a patient’s ear or accepting hearing aid from a patient with bare hands may allow inadvertent cross-infection via contact transmission. Cerumen is not considered an infectious agent unless it is contaminated with blood or mucus. However, due to its color and viscosity, visual detection of blood or ear drainage contaminants cannot be made with predictable accuracy and, therefore, cerumen should be treated as if it is a potentially infectious agent .
In the absence of previous studies, the purpose of this investigation was to document the presence of pathogenic bacterial and/or fungal microorganisms on the surface of custom hearing aids.
2
Subjects and methods
Twenty-four hearing-impaired men and 17 hearing-impaired women, ranging from 10 to 82 years of age, participated in this study. Patients were all using one type of hearing aids [in the canal (ITC)]. Potential subjects who arrived at the clinic for routine follow-up were informed of the purpose of the study and asked to volunteer. Every volunteer had given an informed consent. Ethical committee approvation was taken from Haydarpaşa Numune Education and Research Hospital. None of the patients attending the clinic had suffered from acute otitis externa. All swabs were taken in the same climate to avoid seasonal colonization differences. They were taken in the spring. We wanted to take samples in the same climate to equalize the conditions.
Three samples were taken, one from the surface of the hearing aid’s ear mold; one from the hearing aid-wearing ear canal and the last one from the ear without hearing aid. We have collected the samples with cotton swabs. Before taking the samples we did not clean the ear or remove the serumen. The samples were added to Stuart transport medium and transported to the microbiology test laboratory. The swabs were plated on blood agar plate, MacConkey agar, and chocolate agar separately and the plates were incubated at 37 °C for 24 h.All isolates were identified using standard microbiological methods and the Vitek 2 system, an automated assay (BioMérieux, France). For pathogenic bacteria antimicrobial susceptibility test was performed and interpreted via disk diffusion method, as recomended by the Clinical and Laboratory Standards Institute (CLSI), and the Vitek 2 system .
2
Subjects and methods
Twenty-four hearing-impaired men and 17 hearing-impaired women, ranging from 10 to 82 years of age, participated in this study. Patients were all using one type of hearing aids [in the canal (ITC)]. Potential subjects who arrived at the clinic for routine follow-up were informed of the purpose of the study and asked to volunteer. Every volunteer had given an informed consent. Ethical committee approvation was taken from Haydarpaşa Numune Education and Research Hospital. None of the patients attending the clinic had suffered from acute otitis externa. All swabs were taken in the same climate to avoid seasonal colonization differences. They were taken in the spring. We wanted to take samples in the same climate to equalize the conditions.
Three samples were taken, one from the surface of the hearing aid’s ear mold; one from the hearing aid-wearing ear canal and the last one from the ear without hearing aid. We have collected the samples with cotton swabs. Before taking the samples we did not clean the ear or remove the serumen. The samples were added to Stuart transport medium and transported to the microbiology test laboratory. The swabs were plated on blood agar plate, MacConkey agar, and chocolate agar separately and the plates were incubated at 37 °C for 24 h.All isolates were identified using standard microbiological methods and the Vitek 2 system, an automated assay (BioMérieux, France). For pathogenic bacteria antimicrobial susceptibility test was performed and interpreted via disk diffusion method, as recomended by the Clinical and Laboratory Standards Institute (CLSI), and the Vitek 2 system .
3
Results
A total of 123 samples, obtained from 41 hearing aid users, were analyzed. Seventeen female and 24 male patients (age range 10–82 years, mean 45.5 years) included in the study.
Various organisms were recovered from cultures. Methicillin-sensitive coagulase-negative staphylococci (MSSCoN) were isolated from the samples considered as normal flora of the ear. Different forms of pathogenic bacteria and Candida spp. were isolated from the hearing aid surfaces and hearing aid-wearing ears cultures. Methicillin-resistant coagulase-negative staphylococci (MRSCoN), methicillin-sensitive S. aureus (MSSA), methicillin-resistant S. aureus (MRSA), P. aeruginosa , Escherichia coli , Acinetobacter spp., Staphylococcus auricularis , Stenotrophomonas maltophilia , Candida spp and Candida albicans were identified organisms and all were accompanying with the hearing aid growth ( Table 1 ).
| Microorganisms | Ear with aid ( n ) | Hearingaid ( n ) | Ear without aid ( n ) |
|---|---|---|---|
| Gram negative | |||
| E. coli | 2 | 2 | 1 |
| Acinetobacter spp. | 1 | 1 | – |
| S. maltophilia | 1 | 1 | – |
| P. aeruginosa | 2 | 2 | – |
| Gram positive | |||
| MRSCoN | 9 | 9 | – |
| MSSA | 3 | 3 | 1 |
| MRSA | 2 | 2 | – |
| S. auricularis | 1 | 1 | – |
| Fungal isolates | |||
| C. albicans | 1 | 1 | – |
| Candida spp. | 3 | 3 | 1 |
| Total | 25 | 25 | 3 |
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