Antimicrobial Susceptibility in Chicken-Associated Commensal Bacteria and Assembly-Linked Resistance-Gene Profiling of Escherichia coli from Northern Hungary

Kerek, Ádám; Tornyos, Gergely Álmos; Szarka, Edit; Husz, Levente Hunor; Hetyésy, Máté; Kovács, László; Jerzsele, Ákos

doi:10.3390/antibiotics15101002

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Antimicrobial Susceptibility in Chicken-Associated Commensal Bacteria and Assembly-Linked Resistance-Gene Profiling of Escherichia coli from Northern Hungary

by

Ádám Kerek

^1,2,*

,

Gergely Álmos Tornyos

^1,2,

Edit Szarka

^1,2,

Levente Hunor Husz

^1,2,

Máté Hetyésy

^1,2,

László Kovács

^2,3

and

Ákos Jerzsele

^1,2

¹

Department of Pharmacology and Toxicology, University of Veterinary Medicine Budapest, H-1078 Budapest, Hungary

²

National Laboratory of Infectious Animal Diseases, Antimicrobial Resistance, Veterinary Public Health and Food Chain Safety, University of Veterinary Medicine Budapest, H-1078 Budapest, Hungary

³

Department of Animal Hygiene, Herd Health and Mobile Clinic, University of Veterinary Medicine Budapest, H-1078 Budapest, Hungary

^*

Author to whom correspondence should be addressed.

Antibiotics 2026, 15(10), 1002; https://doi.org/10.3390/antibiotics15101002

Submission received: 15 September 2026 / Revised: 4 October 2026 / Accepted: 7 October 2026 / Published: 9 October 2026

(This article belongs to the Special Issue Beta-Lactam Resistance: Epidemiology and One Health Dynamics)

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Abstract

Background/Objectives: Regional antimicrobial-resistance surveillance can be strengthened by linking phenotypic susceptibility data with genomic evidence. We characterized chicken-associated commensal bacteria from Northern Hungary and examined resistance-gene evidence in available Escherichia coli assemblies. Methods: Broth-microdilution minimum inhibitory concentration (MIC) data were available for 166 bacterial isolates collected in 2022–2023. Among the 69 E. coli isolates in this collection, 24 had corresponding draft whole-genome assemblies, defined here as assembled contig sets that had not been resolved into closed genomes; these assemblies were linked to the MIC records of the same isolates. Analyses included MIC distributions, descriptive correlations, principal component analysis, assembly-quality assessment, resistance-gene profiling, and sequence-context analysis. Results: The collection comprised 26 Staphylococcus spp., 71 Enterococcus spp., and 69 E. coli isolates. In E. coli, ceftriaxone MIC₅₀ and MIC₉₀ values were 0.031 and 512 µg/mL, respectively. Five assemblies contained bla_CTX-M-1-labelled intervals that were identical across 876 bp and corresponded to ceftriaxone MICs of 32–1024 µg/mL. In E. coli isolate 1316, seven resistance-gene calls co-occurred within a 12,933-bp region of one contig. Assembly quality varied substantially, and the draft assembly of E. coli isolate 832 was unsuitable for reliable gene-negative interpretation. Conclusions: The dataset showed heterogeneous susceptibility profiles and identifiable resistance-gene contexts. These findings support isolate-linked phenotypic and genomic surveillance while avoiding population-level, transmission, or clinical resistance classifications unsupported by the available data.

Keywords: antimicrobial resistance; laying hens; Escherichia coli; Enterococcus; Staphylococcus; minimum inhibitory concentration; antimicrobial resistance genes; bla_CTX-M; Northern Hungary

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MDPI and ACS Style

Kerek, Á.; Tornyos, G.Á.; Szarka, E.; Husz, L.H.; Hetyésy, M.; Kovács, L.; Jerzsele, Á. Antimicrobial Susceptibility in Chicken-Associated Commensal Bacteria and Assembly-Linked Resistance-Gene Profiling of Escherichia coli from Northern Hungary. Antibiotics 2026, 15, 1002. https://doi.org/10.3390/antibiotics15101002

AMA Style

Kerek Á, Tornyos GÁ, Szarka E, Husz LH, Hetyésy M, Kovács L, Jerzsele Á. Antimicrobial Susceptibility in Chicken-Associated Commensal Bacteria and Assembly-Linked Resistance-Gene Profiling of Escherichia coli from Northern Hungary. Antibiotics. 2026; 15(10):1002. https://doi.org/10.3390/antibiotics15101002

Chicago/Turabian Style

Kerek, Ádám, Gergely Álmos Tornyos, Edit Szarka, Levente Hunor Husz, Máté Hetyésy, László Kovács, and Ákos Jerzsele. 2026. "Antimicrobial Susceptibility in Chicken-Associated Commensal Bacteria and Assembly-Linked Resistance-Gene Profiling of Escherichia coli from Northern Hungary" Antibiotics 15, no. 10: 1002. https://doi.org/10.3390/antibiotics15101002

APA Style

Kerek, Á., Tornyos, G. Á., Szarka, E., Husz, L. H., Hetyésy, M., Kovács, L., & Jerzsele, Á. (2026). Antimicrobial Susceptibility in Chicken-Associated Commensal Bacteria and Assembly-Linked Resistance-Gene Profiling of Escherichia coli from Northern Hungary. Antibiotics, 15(10), 1002. https://doi.org/10.3390/antibiotics15101002

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Antimicrobial Susceptibility in Chicken-Associated Commensal Bacteria and Assembly-Linked Resistance-Gene Profiling of Escherichia coli from Northern Hungary

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