Antimicrobial Susceptibility Profiles of Commensal Escherichia coli Isolates from Turkeys in Hungarian Poultry Farms Between 2022 and 2023

Abstract

Background: The global spread of antimicrobial resistance (AMR) has prompted the critical importance of regular monitoring. Escherichia coli, a widely distributed facultative anaerobic pathogen, is significant both in terms of the clinical diseases that it causes and as a reservoir of antimicrobial resistance, with notable implications for both animal and public health. Within the poultry industry, the turkey sector is an emerging and internationally significant branch. Methods: Our objective was to assess the antimicrobial resistance profile of commensal Escherichia coli strains isolated from large-scale turkey flocks in Hungary using minimum inhibitory concentration (MIC) determination. Results: A total of 470 isolates were analyzed, revealing that 61.5% of the strains were resistant to amoxicillin, while 18.5% were resistant to amoxicillin-clavulanic acid. The resistance observed against enrofloxacin (62.8%) and ceftriaxone (24%) is concerning. Comparison with human resistance data showed a similar resistance rate for amoxicillin and ampicillin, as well as amoxicillin-clavulanic acid and cephalosporins. However, for other active substances, the situation was significantly worse in veterinary medicine. Conclusions: The lower resistance to amoxicillin-clavulanic acid indicates that most strains are β-lactamase producers. Our findings underscore the necessity of regular and comprehensive surveillance, which can establish temporal trends over time. Incorporating data on antibiotic usage into future studies could facilitate the exploration of relevant correlations. Additionally, the next-generation sequencing of multidrug-resistant strains could help elucidate the genetic basis of resistance.

Keywords: Escherichia coli; Hungary; MIC; antimicrobial resistance; minimum inhibitory concentration; poultry; turkeys.

Figure 1

The regional distribution of Escherichia coli strains (n = 470) isolated from turkeys across the seven administrative regions of Hungary.

Figure 2

Susceptibility profile of Escherichia coli samples isolated from turkeys (n = 470) to active substances of animal and public health importance.

Figure 3

A comparison of commensal Escherichia coli strains isolated from turkeys and available human resistance data.

Figure 4

Correlation analysis of antimicrobial resistance rates of Escherichia coli strains isolated from turkeys (n = 470) by drug substance.

Figure 5

Cluster analysis of Escherichia coli strains isolated from turkeys (n = 470), the classification of samples by region, antimicrobial resistance, and color coding are shown below the horizontal axis. Different colors are shown in the figure to facilitate separation of the main clusters. The colored bar at the bottom of the dendrogram represents the regional origin of each isolate, corresponding to the color scheme in the legend. Each vertical segment in this bar denotes an individual isolate, and its color indicates the administrative region from which it was collected. This allows for a quick visual assessment of how isolates from different regions cluster together or remain dispersed across multiple clusters.

Figure 6

Principal component analysis (PCA) of the samples according to the distribution of the samples in three main clusters after cluster analysis-based antimicrobial resistance. Samples classified as Cluster 1 are shown in purple, Cluster 2 in green, and Cluster 3 in yellow.