{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,20]],"date-time":"2026-04-20T16:03:07Z","timestamp":1776700987529,"version":"3.51.2"},"reference-count":40,"publisher":"MDPI AG","issue":"22","license":[{"start":{"date-parts":[[2025,11,17]],"date-time":"2025-11-17T00:00:00Z","timestamp":1763337600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"ortuguese Foundation for Science and Technology","award":["UIDB\/CVT\/00772\/2020"],"award-info":[{"award-number":["UIDB\/CVT\/00772\/2020"]}]},{"name":"ortuguese Foundation for Science and Technology","award":["LA\/P\/0059\/2020"],"award-info":[{"award-number":["LA\/P\/0059\/2020"]}]},{"name":"ortuguese Foundation for Science and Technology","award":["UIDB\/00153\/2020"],"award-info":[{"award-number":["UIDB\/00153\/2020"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Animals"],"abstract":"<jats:p>Canine otitis externa is a common and recurrent ear infection in dogs, often caused by bacterial pathogens, and complicated by increasing antimicrobial resistance. The analysis of bacterial isolates from dogs with otitis externa revealed a predominance of Staphylococcus pseudintermedius, representing 41% of all cases, followed by Staphylococcus aureus (23%), and Pseudomonas aeruginosa (19%). Other less frequently isolated organisms included Escherichia coli, Streptococcus canis, and Proteus mirabilis. These results highlight the significant role of S. pseudintermedius in the pathogenesis of otitis externa in dogs, as well as the relevance of Gram-negative opportunistic pathogens like P. aeruginosa, which exhibits the highest recurrence rate, with 90% of the cases associated with highly resistant to \u03b2-lactams (93% for amoxicillin\u2013clavulanic acid; &gt;70% for third-generation cephalosporins). P. mirabilis showed complete resistance to tetracycline, partial resistance to doxycycline, and reduced susceptibility to carbapenems, nitrofurantoin, and polymyxin B. S. canis exhibited limited resistance to erythromycin and clindamycin, while S. epidermidis displayed extensive multidrug resistance, including \u03b2-lactams, fluoroquinolones, sulfonamides, and polymyxins. These findings highlight the high prevalence of multidrug-resistant pathogens in canine otitis externa, emphasizing the need for culture-guided therapy and raising concerns regarding One Health, due to potential zoonotic transmission and dissemination of genetic determinants of antimicrobial resistance.<\/jats:p>","DOI":"10.3390\/ani15223317","type":"journal-article","created":{"date-parts":[[2025,11,18]],"date-time":"2025-11-18T09:58:42Z","timestamp":1763459922000},"page":"3317","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["Bacterial Agents and Antimicrobial-Resistance Patterns in Canine Otitis Externa"],"prefix":"10.3390","volume":"15","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-8857-4038","authenticated-orcid":false,"given":"S\u00f3nia","family":"Saraiva","sequence":"first","affiliation":[{"name":"Department of Veterinary Sciences, University of Tr\u00e1s-os-Montes and Alto Douro, 5000-801 Vila Real, Portugal"},{"name":"Animal and Veterinary Research Center (CECAV), University of Tr\u00e1s-os-Montes and Alto Douro, 5000-801 Vila Real, Portugal"},{"name":"Associate Laboratory of Animal and Veterinary Sciences (AL4AnimalS), 5000-801 Vila Real, Portugal"},{"name":"Microbiology and Antibiotic Resistance Team (MicroART), University of Tr\u00e1s-os-Montes and Alto Douro, 5000-801 Vila Real, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0009-0000-4884-0963","authenticated-orcid":false,"given":"Rita","family":"Calouro","sequence":"additional","affiliation":[{"name":"Animal and Veterinary Research Center (CECAV), University of Tr\u00e1s-os-Montes and Alto Douro, 5000-801 Vila Real, Portugal"},{"name":"Associate Laboratory of Animal and Veterinary Sciences (AL4AnimalS), 5000-801 Vila Real, Portugal"},{"name":"Microbiology and Antibiotic Resistance Team (MicroART), University of Tr\u00e1s-os-Montes and Alto Douro, 5000-801 Vila Real, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2326-6226","authenticated-orcid":false,"given":"Telma","family":"de Sousa","sequence":"additional","affiliation":[{"name":"Microbiology and Antibiotic Resistance Team (MicroART), University of Tr\u00e1s-os-Montes and Alto Douro, 5000-801 Vila Real, Portugal"},{"name":"Department of Genetics and Biotechnology, University of Tr\u00e1s-os-Montes and Alto Douro, 5000-801 Vila Real, Portugal"},{"name":"Functional Genomics and Proteomics Unit, University of Tr\u00e1s-os-Montes and Alto Douro, 5000-801 Vila Real, Portugal"},{"name":"Associated Laboratory for Green Chemistry, University NOVA of Lisbon, 1099-085 Caparica, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2146-5627","authenticated-orcid":false,"given":"Maria de Lurdes Enes","family":"Dapkevicius","sequence":"additional","affiliation":[{"name":"Faculty of Agricultural and Environmental Sciences, University of the Azores, 9500-321 Angra do Hero\u00edsmo, Portugal"},{"name":"Institute of Agricultural and Environmental Research and Technology (IITAA), University of the Azores, 9500-321 Angra do Hero\u00edsmo, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8769-8103","authenticated-orcid":false,"given":"Jo\u00e3o R.","family":"Mesquita","sequence":"additional","affiliation":[{"name":"School of Medicine and Biomedical Sciences (ICBAS), Porto University, 4050-313 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7196-4179","authenticated-orcid":false,"given":"Ana C.","family":"Coelho","sequence":"additional","affiliation":[{"name":"Department of Veterinary Sciences, University of Tr\u00e1s-os-Montes and Alto Douro, 5000-801 Vila Real, Portugal"},{"name":"Animal and Veterinary Research Center (CECAV), University of Tr\u00e1s-os-Montes and Alto Douro, 5000-801 Vila Real, Portugal"},{"name":"Associate Laboratory of Animal and Veterinary Sciences (AL4AnimalS), 5000-801 Vila Real, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0925-689X","authenticated-orcid":false,"given":"Patr\u00edcia","family":"Poeta","sequence":"additional","affiliation":[{"name":"Department of Veterinary Sciences, University of Tr\u00e1s-os-Montes and Alto Douro, 5000-801 Vila Real, Portugal"},{"name":"Animal and Veterinary Research Center (CECAV), University of Tr\u00e1s-os-Montes and Alto Douro, 5000-801 Vila Real, Portugal"},{"name":"Associate Laboratory of Animal and Veterinary Sciences (AL4AnimalS), 5000-801 Vila Real, Portugal"},{"name":"Department of Genetics and Biotechnology, University of Tr\u00e1s-os-Montes and Alto Douro, 5000-801 Vila Real, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2025,11,17]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"895","DOI":"10.1111\/jsap.13351","article-title":"Outcomes, Complications and Risk Factors Following Fluoroscopically Guided Transcondylar Screw Placement for Humeral Intracondylar Fissure","volume":"62","author":"Carwardine","year":"2021","journal-title":"J. Small Anim. Pract."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"4","DOI":"10.1186\/s40575-023-00128-x","article-title":"Demography and Disorders of English Cocker Spaniels under Primary Veterinary Care in the UK","volume":"10","author":"Engdahl","year":"2023","journal-title":"Canine Med. Genet."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"S10","DOI":"10.2460\/javma.23.01.0002","article-title":"Managing Recurrent Otitis Externa in Dogs: What Have We Learned and What Can We Do Better?","volume":"261","author":"Nuttall","year":"2023","journal-title":"J. Am. Vet. Med. Assoc."},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Hemida, M.B.M., Vuori, K.A., Borgstr\u00f6m, N.C., Moore, R., Rosendahl, S., Anturaniemi, J., Estrela-Lima, A., and Hielm-Bj\u00f6rkman, A. (2023). Early Life Programming by Diet Can Play a Role in Risk Reduction of Otitis in Dogs. Front. Vet. Sci., 10.","DOI":"10.3389\/fvets.2023.1186131"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"7","DOI":"10.1186\/s40575-021-00106-1","article-title":"Frequency and Predisposing Factors for Canine Otitis Externa in the UK\u2014A Primary Veterinary Care Epidemiological View","volume":"8","author":"Volk","year":"2021","journal-title":"Canine Med. Genet."},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Rosales, R.S., Ram\u00edrez, A.S., Moya-Gil, E., de la Fuente, S.N., Su\u00e1rez-P\u00e9rez, A., and Poveda, J.B. (2024). Microbiological Survey and Evaluation of Antimicrobial Susceptibility Patterns of Microorganisms Obtained from Suspect Cases of Canine Otitis Externa in Gran Canaria, Spain. Animals, 14.","DOI":"10.3390\/ani14050742"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"51","DOI":"10.1111\/j.1748-5827.1997.tb02987.x","article-title":"New Combination for the Therapy of Canine Otitis Externa: I Microbiology of Otitis Externa","volume":"38","author":"Kiss","year":"1997","journal-title":"J. Small Anim. Pract."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"422","DOI":"10.1111\/j.1365-3164.2009.00853.x","article-title":"Histological Changes in the External Ear Canal of Dogs with Otitis Externa","volume":"20","author":"Huang","year":"2009","journal-title":"Vet. Dermatol."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"21","DOI":"10.33262\/anatomiadigital.v7i1.2.2926","article-title":"Comparaci\u00f3n Del Tratamiento de Fitoterapia vs Tratamiento Convencional de Otitis Bacteriana \u201cCocos\u201d En Perros","volume":"7","author":"Ortiz","year":"2024","journal-title":"Anatom\u00eda Digit."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"435","DOI":"10.1007\/s11259-010-9417-y","article-title":"Identification and Antimicrobial Susceptibility Patterns of Bacteria Causing Otitis Externa in Dogs","volume":"34","author":"Malayeri","year":"2010","journal-title":"Vet. Res. Commun."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"23","DOI":"10.17555\/jvc.2017.02.34.1.23","article-title":"Identification and Antimicrobial Susceptibility of Bacteria Isolated from Dogs with Chronic Otitis Externa","volume":"34","author":"Park","year":"2017","journal-title":"J. Vet. Clin."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"43","DOI":"10.1111\/avj.12007","article-title":"Identification and Antibiotic Susceptibility of Bacterial Isolates from Dogs with Otitis Externa in Australia","volume":"91","author":"Bugden","year":"2013","journal-title":"Aust. Vet. J."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"e121","DOI":"10.1017\/S0950268818003278","article-title":"Antimicrobial Resistance Patterns of Bacteria Isolated from Dogs with Otitis","volume":"147","author":"Cazeau","year":"2019","journal-title":"Epidemiol. Infect."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"105399","DOI":"10.1016\/j.micpath.2022.105399","article-title":"High Rates of Multidrug Resistance in Bacteria Associated with Small Animal Otitis: A Study of Cumulative Microbiological Culture and Antimicrobial Susceptibility","volume":"165","author":"Martins","year":"2022","journal-title":"Microb. Pathog."},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Garcias, B., Batalla, M., Vidal, A., Dur\u00e1n, I., and Darwich, L. (2025). Trends in Antimicrobial Resistance of Canine Otitis Pathogens in the Iberian Peninsula (2010\u20132021). Antibiotics, 14.","DOI":"10.3390\/antibiotics14040328"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"42","DOI":"10.1046\/j.1472-765x.2000.00759.x","article-title":"Antimicrobial Susceptibility of Staphylococci Isolated from Otitis Externa in Dogs","volume":"31","author":"Lilenbaum","year":"2000","journal-title":"Lett. Appl. Microbiol."},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Kwon, J., Yang, M.-H., Ko, H.-J., Kim, S.-G., Park, C., and Park, S.-C. (2022). Antimicrobial Resistance and Virulence Factors of Proteus Mirabilis Isolated from Dog with Chronic Otitis Externa. Pathogens, 11.","DOI":"10.3390\/pathogens11101215"},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Hur, B.A., Hardefeldt, L.Y., Verspoor, K.M., Baldwin, T., and Gilkerson, J.R. (2020). Describing the Antimicrobial Usage Patterns of Companion Animal Veterinary Practices; Free Text Analysis of More than 4.4 Million Consultation Records. PLoS ONE, 15.","DOI":"10.1371\/journal.pone.0230049"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"81","DOI":"10.30972\/vet.2221826","article-title":"First Report of a Linezolid-Resistant MRSA (Methicillin Resistant Staphylococcus aureus) Isolated from a Dog with a Severe Bilateral Otitis in Portugal","volume":"22","author":"Seixas","year":"2011","journal-title":"Rev. Vet."},{"key":"ref_20","first-page":"337","article-title":"Clonality of Methicillin-Resistant Staphylococcus aureus and Methicillin-Resistant Staphylococcus pseudintermedius Isolated from Healthy and Sick Companion Animals and Humans in Portugal. Poster session","volume":"18","author":"Couto","year":"2012","journal-title":"Clin. Microbiol. Infect."},{"key":"ref_21","unstructured":"European Committee on Antimicrobial Susceptibility Testing (EUCAST) (2025). Breakpoint Tables for Interpretation of MICs and Zone Diameters, Version 15.0., EUCAST."},{"key":"ref_22","unstructured":"Clinical and Laboratory Standards Institute (CLSI) (2025). Performance Standards for Antimicrobial Susceptibility Testing, CLSI Supplement\u2009M100. [35th ed.]."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"1084","DOI":"10.1111\/jam.14868","article-title":"Changes in the Ear Canal Microbiota of Dogs with Otitis Externa","volume":"130","author":"Kasai","year":"2021","journal-title":"J. Appl. Microbiol."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"1173","DOI":"10.2460\/ajvr.1999.60.09.1173","article-title":"Effects of Ear Type, Sex, Age, Body Weight, and Climate on Temperatures in the External Acoustic Meatus of Dogs","volume":"60","author":"Huang","year":"1999","journal-title":"Am. J. Vet. Res."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"117","DOI":"10.2478\/acve-2024-0009","article-title":"Molecular Prevalence of MecA and MecC Genes in Coagulase-Positive Staphylococci Isolated from Dogs with Dermatitis and Otitis in Belgrade, Serbia: A One Year Study","volume":"74","author":"Radalj","year":"2024","journal-title":"Acta Vet. Beogr."},{"key":"ref_26","first-page":"29170","article-title":"First Identification of Methicillin-Resistant Staphylococcus pseudintermedius Strains among Coagulase-Positive Staphylococci Isolated from Dogs with Otitis Externa in Trinidad, West Indies","volume":"5","author":"Dziva","year":"2015","journal-title":"Infect. Ecol. Epidemiol."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"468","DOI":"10.1111\/vde.12382","article-title":"Prior Antimicrobial Use as a Risk Factor for Resistance in Selected Staphylococcus pseudintermedius Isolates from the Skin and Ears of Dogs","volume":"27","author":"Zur","year":"2016","journal-title":"Vet. Dermatol."},{"key":"ref_28","first-page":"168","article-title":"Epidemiological Study of Dogs with Otitis Externa in Cape Breton, Nova Scotia","volume":"58","author":"Perry","year":"2017","journal-title":"Can. Vet. J."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"183","DOI":"10.1016\/j.jiph.2023.10.041","article-title":"Epidemiologic Case Investigation on the Zoonotic Transmission of Methicillin-Resistant Staphylococcus pseudintermedius among Dogs and Their Owners","volume":"16","author":"Teixeira","year":"2023","journal-title":"J. Infect. Public Health"},{"key":"ref_30","doi-asserted-by":"crossref","unstructured":"D\u00e9gi, J., Morariu, S., Simiz, F., Herman, V., Beteg, F., and D\u00e9gi, D.M. (2024). Future Challenge: Assessing the Antibiotic Susceptibility Patterns of Staphylococcus Species Isolated from Canine Otitis Externa Cases in Western Romania. Antibiotics, 13.","DOI":"10.3390\/antibiotics13121162"},{"key":"ref_31","doi-asserted-by":"crossref","unstructured":"Lynch, S.A., and Helbig, K.J. (2021). The Complex Diseases of Staphylococcus pseudintermedius in Canines: Where to Next?. Vet. Sci., 8.","DOI":"10.3390\/vetsci8010011"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"42","DOI":"10.1136\/vr.101426","article-title":"Frequency of Isolation and Antibiotic Resistance of Staphylococcal Flora from External Otitis of Dogs","volume":"173","author":"Imre","year":"2013","journal-title":"Vet. Rec."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"3255","DOI":"10.2147\/IDR.S272733","article-title":"Methicillin-Resistant Staphylococcus aureus (MRSA): One Health Perspective Approach to the Bacterium Epidemiology, Virulence Factors, Antibiotic-Resistance, and Zoonotic Impact","volume":"13","author":"Algammal","year":"2020","journal-title":"Infect. Drug Resist."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"1511","DOI":"10.17582\/journal.pjz\/20211101121137","article-title":"Genetic Characterization of Methicillin Resistant Staphylococcus pseudintermedius in Dogs and Cats in Cyprus: Comparison of MRSP and MRSA Results","volume":"54","author":"Tamakan","year":"2022","journal-title":"Pak. J. Zool."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"102","DOI":"10.1016\/j.vetmic.2017.11.024","article-title":"Prevalence and Mechanisms of Resistance to Fluoroquinolones in Pseudomonas aeruginosa and Escherichia coli Isolates Recovered from Dogs Suffering from Otitis in Greece","volume":"213","author":"Vingopoulou","year":"2018","journal-title":"Vet. Microbiol."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"1434","DOI":"10.1590\/S1517-83822011000400027","article-title":"In Vitro Antimicrobial Resistance of Pseudomonas aeruginosa Isolated from Canine Otitis Externa in Rio de Janeiro, Brazil","volume":"42","author":"Penna","year":"2011","journal-title":"Braz. J. Microbiol."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"2499","DOI":"10.14202\/vetworld.2022.2499-2505","article-title":"Antibiotic Resistance Profiles and Activity of Clove Essential Oil (Syzygium aromaticum) against Pseudomonas aeruginosa Isolated of Canine Otitis","volume":"15","author":"Costa","year":"2022","journal-title":"Vet. World"},{"key":"ref_38","doi-asserted-by":"crossref","unstructured":"de Sousa, T., Machado, S., Cani\u00e7a, M., Ramos, M.J.N., Santos, D., Ribeiro, M., H\u00e9braud, M., Igrejas, G., Alves, O., and Costa, E. (2025). Pseudomonas aeruginosa: One Health Approach to Deciphering Hidden Relationships in Northern Portugal. J. Appl. Microbiol., 136.","DOI":"10.1093\/jambio\/lxaf037"},{"key":"ref_39","doi-asserted-by":"crossref","unstructured":"Secker, B., Shaw, S., and Atterbury, R.J. (2023). Pseudomonas spp. in Canine Otitis Externa. Microorganisms, 11.","DOI":"10.3390\/microorganisms11112650"},{"key":"ref_40","doi-asserted-by":"crossref","unstructured":"Leonard, C., Thiry, D., Taminiau, B., Daube, G., and Fontaine, J. (2022). External Ear Canal Evaluation in Dogs with Chronic Suppurative Otitis Externa: Comparison of Direct Cytology, Bacterial Culture and 16S Amplicon Profiling. Vet. Sci., 9.","DOI":"10.3390\/vetsci9070366"}],"container-title":["Animals"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2076-2615\/15\/22\/3317\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,11,18]],"date-time":"2025-11-18T10:26:02Z","timestamp":1763461562000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2076-2615\/15\/22\/3317"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,11,17]]},"references-count":40,"journal-issue":{"issue":"22","published-online":{"date-parts":[[2025,11]]}},"alternative-id":["ani15223317"],"URL":"https:\/\/doi.org\/10.3390\/ani15223317","relation":{},"ISSN":["2076-2615"],"issn-type":[{"value":"2076-2615","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,11,17]]}}}