Author(s)

Marta Aleandri¹, Cecilia Ambrosi^1,2, Maria Stefania Lepanto¹, Antonietta Lucia Conte¹, Massimiliano Marazzato¹, Catia Longhi¹, Mauro Nicoletti³, Carlo Zagaglia¹, Paola Goldoni¹, Francesco Bussu⁴, Roberta Anzivino⁴, Roberto Gallus⁵, Maria Pina Battista⁴, Maria Pia Conte^1*, Anna Teresa Palamara^6,7

¹Department of Public Health and Infectious Diseases, “Sapienza” University of Rome, Rome, Italy.
²Dani Di Giò Foundation-Onlus, Rome, Italy.
³Department of Medical, Oral and Biotechnological Sciences, University “G. D’Annunzio”, Chieti, Italy.
⁴Institute of Otolaryngology, “Cattolica del Sacro Cuore” University Agostino Gemelli Polyclinic, Rome, Italy.
⁵Otolaryngology, Mater Olbia Hospital, Olbia, Italy.
⁶Department of Public Health and Infectious Diseases, “Sapienza” University of Rome, Laboratory Affiliated to Institute Pasteur Italia, Cenci-Bolognetti Foundation, Rome, Italy.
⁷San Raffaele Pisana, IRCCS, Telematic University, Rome, Italy.

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.

Ear Bacterial Flora, Hearing Aids, Acute Otitis Externa

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. and 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.