AiM  Vol.9 No.7 , July 2019
Characterization of the Ear Canal Bacterial Flora Present in Hearing Aids (HA) Wearing Subjects
Abstract: The use of hearing aids (HA) is considered a predisposing factor for ear microbial infections. We undertook this study to compare the presence and nature of the microbial flora inhabiting of ears of HA and non-HA (nHA) users. Swab samples of the ears of HA and nHA users were collected from the Institute of Otolaryngology, “Cattolica del Sacro Cuore” University “Agostino Gemelli”, Rome, Italy. Swab samples were taken from the ear canal of 57 HA and 33 nHA users. The components of the microbial flora present on each swab sample were identified and characterized at the level of species. A total of 41 different bacterial species were identified. A statistically significant prevalence of polymicrobial communities was found in ears presenting signs of inflammation (2.5 ± 1.7 vs 2.1 ± 1.3; P = 0.02) and in HA users (2.3 ± 1.2 vs 1.7 ± 1.0; P = 0.002). Few putative pathogens were detected. Candida albicans spp. was not isolated in our study. A small number of swab samples presented no microbial growth. Bacterial species isolated from HA users with and without inflammation were assayed for the ability to form biofilm. Among gram-positive and gram-negative bacteria, S. aureus, CoNS, P. aeruginosa and K. pneumoniae were found to be strong biofilm producers. S. aureus and P. aeruginosa, isolated only from the ears of HA and nHA users presenting signs of inflammation, were further analyzed for their antibiotic-resistance profile and characterized by the Multilocus Sequence Typing (MLST) assay. The highest rates of antibacterial resistance were in S. aureus to penicillin (75.5%) and in P. aeruginosa, to amoxicillin-clavulanic acid, cefotaxime, ertapenem, tigecycline and trime-thoprim-sulfamethoxazole (100%). Moreover, three S. aureus strains (37.5%) were methicillin-resistant (MRSA). Of the eight S. aureus isolates, we identified six sequence types (ST) indicating that 75% are likely independent clones. For what it concerned P. aeruginosa, six different STs were assigned. Interestingly, two out of the six strains presented newly identified ST values. This study sheds new light on the combined effect of the presence of HA devices and signs of external ear inflammation on the composition of the ear bacterial flora. Our results reinforce the need to practice careful hygiene of HA devices to prevent serious ear canal infections.
Cite this paper: Aleandri, M. , Ambrosi, C. , Lepanto, M. , Conte, A. , Marazzato, M. , Longhi, C. , Nicoletti, M. , Zagaglia, C. , Goldoni, P. , Bussu, F. , Anzivino, R. , Gallus, R. , Battista, M. , Conte, M. , Palamara, A. (2019) Characterization of the Ear Canal Bacterial Flora Present in Hearing Aids (HA) Wearing Subjects. Advances in Microbiology, 9, 616-628. doi: 10.4236/aim.2019.97038.

[1]   Gates, G.A. and Mills, J.H. (2005) Presbycusis. The Lancet, 366, 1111-1120.

[2]   Karaca, C.T., AkÇay, S.S., Toros, S.Z., Oysu, C., Verim, A., Çelebi, S. and Aksaray, S. (2013) External Auditory Canal Microbiology and Hearing Aid Use. American Journal of Otolaryngology, 34, 278-281.

[3]   Orji, F.T., Onyero, E. and Agbo, C.E. (2014) The Clinical Implications of Ear Canal Debris in Hearing Aid Users. Pakistan Journal of Medical Sciences, 30, 483-487.

[4]   Rosenfeld, R.M., Schwartz, S.R., Cannon, C.R., Roland, P.S., Simon, G.R., Kumar, K.A., Huang. W.W., Haskell, H.W. and Robertson, P.J. (2014) Clinical Practice Guideline: Acute Otitis Externa Executive Summary. Otolaryngology—Head and Neck Surgery, 150, 161-168.

[5]   Schaefer, P. and Baugh, R.F. (2012) Acute Otitis Externa: An Update. American Family Physician, 86, 1055-1061.

[6]   Stroman, D.W., Roland, P.S., Dohar, J. and Burt, W. (2001) Microbiology of Normal External Auditory Canal. Laryngoscope, 111, 2054-2059.

[7]   Frank, D.N., Spiegelman, G.B., Davis, W., Wagner, E., Lyons, E. and Pace, N.R. (2003) Culture-Independent Molecular Analysis of Microbial Constituents of the Healthy Human Outer. European Journal of Clinical Microbiology, 41, 295-303.

[8]   Raza, S.A., Denholm, S.W. and Wong, J.C. (1995) An Audit of the Management of Acute Otitis Externa in an ENT Casualty Clinic. The Journal of Laryngology & Otology, 109, 130-133.

[9]   Battikhi, M.N. and Ammar, S.I. (2004) Otitis Externa Infection in Jordan. Clinical and Microbiological Features. Saudi Medical Journal, 25, 1199-1203.

[10]   Gerchman, Y., Patichov, R. and Zeltzer, T. (2012) Lipolytic, Proteolytic, and Cholesterol-Degrading Bacteria from the Human Cerumen. Current Microbiology, 64, 588-591.

[11]   Kelly, K.E. and Mohs, D.C. (1996) The External Auditory Canal. Anatomy and Physiology. Otolaryngologic Clinics of North America, 29, 725-739.

[12]   Walshe, P., Rowley, H. and Timon, C. (2001) A Worrying Development in the Microbiology of Otitis Externa. Clinical Otolaryngology and Allied Sciences, 26, 218-220.

[13]   Roland, P.S. (2002) Chronic Suppurative Otitis Media: A Clinical Overview. Ear, Nose & Throat Journal, 81, 8-10.

[14]   Geyer, M., Howell-Jones, R., Cunningham, R., et al. (2011) Health Protection Agency GP Microbiology Laboratory Use Group Consensus of Microbiology Reporting of Ear Swab Results to Primary Care Clinicians in Patients with Otitis Externa. British Journal of Biomedical Science, 68, 174-180.

[15]   Ahmad, N., Etheridge, C., Farrington, M. and Baguley, D.M. (2007) Prospective Study of the Microbiological Flora of Hearing Aid Moulds and the Efficacy of Current Cleaning Techniques. The Journal of Laryngology & Otology, 121, 110-113.

[16]   Eden, P.A., Schmidt, T.M., Blakemore, R.P. and Pace, N.R. (1991) Phylogenetic Analysis of Aquaspirillummagnetotacticum Using Polymerase Chain Reaction-Amplified 16SrRNA-Specific DNA. International Journal of Systematic Bacteriology, 41, 324-325.

[17]   Enright, M.C., Day, N.P., Davies, C.E., Peacock, S.J. and Spratt, B.G. (2000) Multilocus Sequence Typing for Characterization of Methicillin-Resistant and Methicillin-Susceptible Clones of Staphylococcus aureus. Journal of Clinical Microbiology, 38, 1008-1015.

[18]   Curran, B., Jonas, D., Grundmann, H., Pitt, T. and Dowson, C.G. (2004) Development of a Multilocus Sequence Typing Scheme for the Opportunistic Pathogen Pseudomonas aeruginosa. Journal of Clinical Microbiology, 42, 5644-5649.

[19]   Conte, M.P., Longhi, C., Marazzato, M., Conte, A.L., Aleandri, M., Lepanto, M.S., Zagaglia, C., Nicoletti, M., Aloi, M., Totino, V., Palamara, A.T. and Schippa, S. (2016) The Adherent/Invasive Escherichia coli Strain LF82 Invades and Persists in Human Prostate Cell Line RWPE-1, Activating a Strong Inflammatory Response. Infection and Immunity, 17, 3105-3113.

[20]   Stepanovic, S., Vukovic, D., Hola, V., Di Bonaventura, G., Djukic, S., Cirkovic, I. and Ruzicka, F. (2007) Quantification of Biofilm in Microtiter Plates: Overview of Testing Conditions and Practical Recommendations for Assessment of Biofilm Production by Staphylococci. APMIS, 115, 891-899.

[21]   McWilliams, C.J., Smith, C.H. and Goldman, R.D. (2012) Acute Otitis Externa in Children. Canadian Family Physician, 58, 1222-1224.

[22]   Paluch-Oles, J., Magrys, A., Koziol-Montewka, M., Niedzielski, A., Niedzwiadek, J., Niedzielska, G. and Kotowski, M. (2011) The Phenotypic and Genetic Biofilm Formation Characteristics of Coagulase-Negative Staphylococci Isolates in Children with Otitis Media. International Journal of Pediatric Otorhinolaryngology, 75, 126-130.

[23]   Berni, E., Scott, L.A., Jenkins-Jones, S., Hanka De Voogd, H., Rocha, M.S., Butler, C.C., Morgan, C.L., Craig, J. and Currie, C.J. (2016) Non-Response to Antibiotic Treatment in Adolescents for Four Common Infections in UK Primary Care 1991-2012: A Retrospective, Longitudinal Study. Antibiotics, 5, 25.

[24]   Torretta, S., Drago, L., Marchisio, P., Mattina, R., Clemente, I.A. and Pignataro, L. (2011) Diagnostic Accuracy of Nasopharyngeal Swabsin Detecting Biofilm-Producing Bacteria in Chronic Adenoiditis: A Preliminary Study. Otolaryngology—Head and Neck Surgery, 144, 784-788.

[25]   Morita, Y., Tomida, J. and Kawamura, Y. (2014) Responses of Pseudomonas aeruginosa to Antimicrobials. Frontiers in Microbiology, 4, 422.