26d30a521fce67460cd10f290e58cd9e antibiotics-15-00678.pdf d2807d4417a9ca49b8047efe4e89b5b7e4195ef7 antibiotics-15-00678.pdf 36b4f74f750c836c7226d72d190cd8bb6c47d5ada5a6af81353756280522470b antibiotics-15-00678.pdf Title: Evolution and Antimicrobial Resistance Profiles of Klebsiella spp. Infections in Companion Animals in the Iberian Peninsula Subject: Background/Objectives: Antimicrobial resistance (AMR) in companion animals is an increasing concern within the One Health framework, particularly regarding opportunistic pathogens such as Klebsiella spp. This retrospective study evaluated the epidemiology, antimicrobial susceptibility profiles, and temporal resistance trends of Klebsiella spp. infections in dogs and cats across the Iberian Peninsula. Methods: A total of 809 clinical isolates collected between 2016 and 2024 and submitted to a private diagnostic laboratory in Barcelona were analysed. Results: Klebsiella pneumoniae was the predominant species (70%), more frequently identified in cats (76%) than in dogs (68%). Dermatological and respiratory samples exhibited the highest prevalence of multidrug-resistant (MDR) isolates. Overall MDR prevalence was high, particularly in cats (51.1%; 95% CI 41.1–60.9%) compared with dogs (38.4%; 95% CI 34.1–42.8%) although it was not statistically significant. K. pneumoniae generally exhibited higher resistance rates than K. oxytoca, particularly to amoxicillin/clavulanic acid, first-/second-generation cephalosporins, third-/fourth-generation cephalosporins (3/4th GC), fluoroquinolones, and tetracyclines. In both bacterial species, resistance rates were consistently higher among feline isolates. In contrast, aminoglycosides and phenicols retained high activity against most isolates. Temporal analysis revealed a significant increasing resistance trend to amoxicillin/clavulanic acid, which is particularly concerning given the widespread use of this antimicrobial as a first-line treatment in small animal practice. However, resistance trend to aminoglycosides showed a significant decline. No significant temporal changes were detected for 3/4th GC and fluoroquinolones, suggesting the persistence of resistant populations within companion animals. Resistance to aminoglycosides and phenicols remained comparatively low in this study. Whereas critically important category B antimicrobials, such as 3/4th GC and fluoroquinolones, exhibited low to moderate effectiveness, raising concerns about their empirical use. Conclusions: These findings highlight the substantial AMR and MDR burden of K. pneumoniae in companion animals in the Iberian Peninsula and reinforce the need for prudent antimicrobial use, routine susceptibility testing, and integrated One Health surveillance strategies. Keywords: Klebsiella pneumoniae; Klebsiella oxytoca; dogs; cats; AMR evolution; Spain Author: María Jiménez-Serrano, Anna Vidal, Inma Duran, Chiara Seminati and Laila Darwich Creator: LaTeX with hyperref Producer: pdfTeX-1.40.25; modified using OpenPDF 1.4.2 CreationDate: Fri Jul 10 08:50:20 2026 CEST ModDate: Fri Jul 10 08:54:41 2026 CEST Custom Metadata: yes Metadata Stream: no Tagged: no UserProperties: no Suspects: no Form: none JavaScript: no Pages: 16 Encrypted: no Page size: 595.276 x 841.89 pts (A4) Page rot: 0 File size: 1807922 bytes Optimized: no PDF version: 1.7 name type encoding emb sub uni object ID ------------------------------------ ----------------- ---------------- --- --- --- --------- GUQELQ+URWPalladioL-Bold Type 1 Custom yes yes yes 75 0 FNIDFJ+VnURWPalladioL Type 1 Custom yes yes yes 76 0 EIFPJP+URWPalladioL-Roma Type 1 Custom yes yes yes 77 0 OGEDFJ+URWPalladioL-Ital Type 1 Custom yes yes yes 78 0 JXTTWW+URWPalladioL-BoldItal Type 1 Custom yes yes yes 79 0 JXPXXJ+EURM10 Type 1 Builtin yes yes yes 129 0 ALDOLK+PalatinoLinotype TrueType WinAnsi yes yes no 159 0 ALDOLK+PalatinoLinotype TrueType WinAnsi yes yes no 173 0 ALDOLK+PalatinoLinotype TrueType WinAnsi yes yes no 181 0 ALDOLK+PalatinoLinotype TrueType WinAnsi yes yes no 199 0 ALDOLK+PalatinoLinotype TrueType WinAnsi yes yes no 237 0 TAQQTO+CMSY10 Type 1 Builtin yes yes yes 307 0 Jhove (Rel. 1.28.0, 2023-05-18) Date: 2026-09-30 03:57:18 CEST RepresentationInformation: antibiotics-15-00678.pdf ReportingModule: PDF-hul, Rel. 1.12.4 (2023-03-16) LastModified: 2026-09-29 14:31:34 CEST Size: 1807922 Format: PDF Version: 1.7 Status: Well-Formed and valid SignatureMatches: PDF-hul MIMEtype: application/pdf PDFMetadata: Objects: 412 FreeObjects: 1 IncrementalUpdates: 0 DocumentCatalog: ViewerPreferences: HideToolbar: false HideMenubar: false HideWindowUI: false FitWindow: true CenterWindow: false DisplayDocTitle: false NonFullScreenPageMode: UseNone Direction: L2R ViewArea: CropBox ViewClip: CropBox PrintArea: CropBox PageClip: CropBox PageLayout: SinglePage PageMode: UseNone Outlines: Item: Title: Introduction Item: Title: Results Item: Title: Discussion Item: Title: Materials and Methods Children: Item: Title: Data Source and Management Item: Title: Bacterial Characterization & Antimicrobial Susceptibility Testing Item: Title: Statistical Analyses Item: Title: References Info: Title: Evolution and Antimicrobial Resistance Profiles of Klebsiella spp. Infections in Companion Animals in the Iberian Peninsula Author: María Jiménez-Serrano, Anna Vidal, Inma Duran, Chiara Seminati and Laila Darwich Subject: Background/Objectives: Antimicrobial resistance (AMR) in companion animals is an increasing concern within the One Health framework, particularly regarding opportunistic pathogens such as Klebsiella spp. This retrospective study evaluated the epidemiology, antimicrobial susceptibility profiles, and temporal resistance trends of Klebsiella spp. infections in dogs and cats across the Iberian Peninsula. Methods: A total of 809 clinical isolates collected between 2016 and 2024 and submitted to a private diagnostic laboratory in Barcelona were analysed. Results: Klebsiella pneumoniae was the predominant species (70%), more frequently identified in cats (76%) than in dogs (68%). Dermatological and respiratory samples exhibited the highest prevalence of multidrug-resistant (MDR) isolates. Overall MDR prevalence was high, particularly in cats (51.1%; 95% CI 41.1–60.9%) compared with dogs (38.4%; 95% CI 34.1–42.8%) although it was not statistically significant. K. pneumoniae generally exhibited higher resistance rates than K. oxytoca, particularly to amoxicillin/clavulanic acid, first-/second-generation cephalosporins, third-/fourth-generation cephalosporins (3/4th GC), fluoroquinolones, and tetracyclines. In both bacterial species, resistance rates were consistently higher among feline isolates. In contrast, aminoglycosides and phenicols retained high activity against most isolates. Temporal analysis revealed a significant increasing resistance trend to amoxicillin/clavulanic acid, which is particularly concerning given the widespread use of this antimicrobial as a first-line treatment in small animal practice. However, resistance trend to aminoglycosides showed a significant decline. No significant temporal changes were detected for 3/4th GC and fluoroquinolones, suggesting the persistence of resistant populations within companion animals. Resistance to aminoglycosides and phenicols remained comparatively low in this study. Whereas critically important category B antimicrobials, such as 3/4th GC and fluoroquinolones, exhibited low to moderate effectiveness, raising concerns about their empirical use. Conclusions: These findings highlight the substantial AMR and MDR burden of K. pneumoniae in companion animals in the Iberian Peninsula and reinforce the need for prudent antimicrobial use, routine susceptibility testing, and integrated One Health surveillance strategies. 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