Revista Cienﬁca, FCV-LUZ / Vol. XXXV Recibido: 26/10/2025 Aceptado: 02/02/2026 Publicado: 05/03/2026 UNIVERSIDAD DEL ZULIA Serbiluz Sistema de Servicios Bibliotecarios y de Información Biblioteca Digital Repositorio Académico 1 of 8 Revista Cienﬁca, FCV-LUZ / Vol. XXXVI UNIVERSIDAD DEL ZULIA Serbiluz Sistema de Servicios Bibliotecarios y de Información Biblioteca Digital Repositorio Académico Phenotypic characterizaon of gentamicin-resistant Escherichia coli strains isolated from raw chicken meat samples in Türkiye: A public health concern Caracterización fenopica de cepas de Escherichia coli resistentes a la gentamicina aisladas de muestras de carne cruda de pollo en Turquía: Un problema de salud pública Seyda Şahin Department of Food Hygiene and Technology, Faculty of Veterinary Medicine, Sivas Cumhuriyet University, 58140, Sivas, Türkiye. *Corresponding author: seydasahin@cumhuriyet.edu.tr ABSTRACT The inappropriate use of anbiocs in poultry producon is considered to have contributed to the global increase and disseminaon of muldrug-resistant pathogens. The objecve of this study was to determine the occurrence of gentamicin- resistant Escherichia coli strains isolated from chicken meat samples and to evaluate their anmicrobial resistance proﬁles in Sivas province, Türkiye. A total of hundred fresh chicken meat samples (breast, drumsck, and wings) were collected from September to December 2022. Aﬅer pre-enrichment of the samples material in buﬀered peptone water, the broths were streaked onto Tryptone Bile X-Glucuronide agar containing 8 µg/mL gentamicin. Anmicrobial suscepbility tesng was performed using the broth microdiluon method to determine minimum inhibitory concentraons. A total of 50 gentamicin- resistant E. coli strains were isolated from chicken meat samples. The strains showed high resistance to Ampicillin (100 %), followed by Trimethoprim/Sulfamethoxazole (88 %) and Ciproﬂoxacin (64 %), respecvely. Muldrug-resistance was found in 96 % (n = 48) of the isolates. All gentamicin-resistant E. coli strains were suscepble to Amikacin, Carbapenems, and β-lactam/β-lactamase inhibitor combinaons. The presence of resistant E. coli in raw chicken meat conﬁrms its potenal role of as source for the spread of anmicrobial resistance and muldrug-resistant strains in retail food. This study highlights the importance of connuous monitoring of E. coli strains isolated from raw chicken meat within the framework of the public health concept. Key words: Anmicrobial resistance; chicken meat; Escherichia coli; gentamicin-resistant, muldrug-resistant strains; public health RESUMEN El uso inapropiado de anbiócos en la producción avícola se considera que ha contribuido al aumento y la diseminación global de patógenos resistentes a múlples fármacos. El objevo de este estudio fue determinar la presencia de Escherichia coli resistente a la gentamicina aislada de muestras de carne de pollo, centrándose en sus perﬁles de resistencia a los anmicrobianos en la provincia de Sivas, Turquía. Se recolectaron y analizaron cien muestras de piezas de pollo fresco (pechuga, muslo y alas). Las muestras se recolectaron entre sepembre y diciembre de 2022. Después del enriquecimiento previo del material de muestra en agua de peptona tamponada, el caldo se sembró en agar Triptona Bilis X-glucurónido que contenía 8 µg/mL de gentamicina. Las pruebas de suscepbilidad a los anmicrobianos se realizaron ulizando el método de concentraciones inhibitorias mínimas por microdilución en caldo. Se aislaron un total de 50 cepas de E. coli resistente a la gentamicina de muestras de carne de pollo. Las cepas de E. coli mostraron una alta resistencia a la Ampicilina (100 %), seguida de Trimetoprima/sulfametoxazol (88 %) y Ciproﬂoxacina (64 %), respecvamente. Las cepas de E. coli resistente a la gentamicina presentaron una tasa de mulrresistencia del 96 % (n = 48). Todas las cepas de E. coli resistente a la gentamicina fueron suscepbles a la Amikacina, los Carbapenémicos y las combinaciones de β-lactámicos/ inhibidores de β-lactamasa. Se conﬁrma que la E. coli presente en muestras de carne cruda de pollo es una fuente potencial de propagación de la resistencia a los anmicrobianos y de cepas mulrresistentes. En este estudio se destaca la importancia del monitoreo connuo de cepas de E. coli aisladas de carne cruda de pollo en el marco del concepto de salud pública. Palabras clave: Resistencia a los anmicrobianos; carne de pollo; Escherichia coli; resistente a la gentamicina; cepas mulrresistentes; salud pública https://doi.org/10.52973/rcfcv-e362837

Revista Cienﬁca, FCV-LUZ / Vol. XXXVI UNIVERSIDAD DEL ZULIA Serbiluz Sistema de Servicios Bibliotecarios y de Información Biblioteca Digital Repositorio Académico INTRODUCTION Anmicrobial resistance (AMR) connues to pose a global threat to public health, and resistance in zoonoc pathogens is of parcular importance for food safety [1]. According to the World Health Organizaon (WHO) reports resistant bacteria belonging to the order Enterobacterales, such as Escherichia coli (E. coli), Klebsiella pneumoniae, and Salmonella spp., are common pathogens in both humans and farm animals [1]. Anbiocs have been used in livestock farming since the 1950s for purposes such as growth promoon, treatment, and disease prevenon. The rate of anmicrobial use is reported to be 73 % in intensive animal husbandry [2]. The use of anmicrobials as growth promoters in poultry feed has been prohibited in both the European Union (EU) and Türkiye since 2006 [3 , 4]. These restricons have signiﬁcantly reduced anmicrobial usage in food-producing animals. Indeed, following the implementaon of these regulaons, anmicrobial use in the EU has decreased by 43.0 % [5]. Despite these measures, it is esmated that 99,502 tons of anmicrobials were used globally in 2020 and this number is expected to rise to 107,472 tons by 2030, with Asian countries accounng for the majority of users [6]. E. coli, a member of the order Enterobacterales, is a natural inhabitant of the intesnal microbiota in humans and animals. Nevertheless, pathogenic strains can cause various infecons [7]. Food-borne AMR E. coli isolates are parcularly concerning due to their ability to disseminate resistance genes via horizontal gene transfer, thereby posing signiﬁcant risks to public health [8]. Numerous studies have shown that E. coli strains isolated from poultry, producon environment, and derived products exhibit high resistance to mulple classes of anbiocs, reﬂecng a crical global health issue [9 , 10 , 11 , 12]. Consequently, the EU, through a direcve issued in 2021, designated E. coli, as an indicator microorganism for monitoring anmicrobial resistance in the intesnal ﬂora of farm animals [11 , 12 , 13]. Gentamicin (CN), an aminoglycoside (AG) anbioc, is widely used in both human and veterinary medicine for the treatment of bacterial infecons owing to its broad-spectrum acvity. Notably, aminoglycosides are included in the WHO list of crical important anbiocs, highlighng the need for prudent use to preserve their eﬀecveness [14 , 15 , 16 , 17]. However, its therapeuc use in poultry producon has led to the emergence and disseminaon of gentamicin-resistant (CN R ) E. coli strains [16]. Previous studies have revealed that CN resistance can spread from poultry farms to humans through the food chain [16 , 18]. In Canada, CN resistance was detected in E. coli isolates of both human and poultry origin [16]. Researchers found that the prevalence of CN R E. coli isolates from poultry sources (e.g., clinical samples, feces/manure, and cecal contents) was 18.3 % between 2009-2013, and 18.4 % between 2014-2017, while the prevalence among E. coli isolates from retail chicken meat increased from 14.0 % to 21.4 %, suggesng a signiﬁcant upward trend over me [16]. This data indicates that the prevalence of CN R E. coli isolates from chicken meat sold for sale is increasing. In addion to direct CN exposure, resistance to CN may also be maintained through co-selecon driven by the use of other anmicrobial classes in poultry producon. Genomic invesgaons within a One Health framework have demonstrated that CN resistance genes are frequently co-located with resistance determinants to β-lactams, sulfonamides, and ﬂuoroquinolones (FQ) on mobile genec elements shared between human and poultry associated E. coli populaons. This suggests that the use of non-aminoglycoside anmicrobials at the farm level may indirectly select for CN R strains throughout the agri-food chain [16]. In Türkiye, although the AMR proﬁles of E. coli strains isolated from poultry, poultry producon environments, and poultry products have been invesgated, there is limited informaon regarding CN resistance paerns and underlying mechanisms [9 , 19 , 20]. A recent study Şahin et al. [12], reported a CN rate of 15.8 % among E. coli strains isolated from poultry cecal samples collected from diﬀerent poultry companies [12]. One of the primary mechanisms involved in CN R is the presence of genes encoding aminoglycoside-modifying enzymes (AMEs), such as aac(3)-IIa, aac(6’)-Ib, and ant(2’’)-Ia, which reduce the eﬃcacy of the anbioc [21]. The horizontal transmission of these genes through mobile genec elements represents a global public health concern [14]. In parcular, contaminaon from chicken meat serves as a signiﬁcant vehicle for the transmission of resistant strains to humans, emphasizing the importance of this issue within the framework of food safety and the One Health approach [22]. Therefore, the present study aimed to determine the anmicrobial resistance proﬁles of phenotypically CN R E. coli strains isolated from chicken meat in Türkiye. The suscepbility of the isolates to various anbiocs was assessed based on minimum inhibitory concentraon (MIC) values. The study contributes to the phenotypic characterizaon of CN R E. coli strains from chicken meat samples and provides valuable insights into the potenal public health risks associated with these resistance paerns. MATERIALS AND METHODS Chicken meat sample collecon and isolaon of gentamycin- resistant E. coli A total of 100 raw chicken meat samples (breast, drumsck, and wings) were collected from various supermarkets, local markets and butchers in Sivas region of Türkiye from September to December 2022. For the isolaon of E. coli, 10 g of sample was asepcally each chicken meat (breast, drumsck and wing) using sterile instruments. The sample was transferred into 90 mL of sterile Buﬀered Peptone Water (BPW; Oxoid CM0509, United Kingdom) and homogenized for 1-2 min using a stomacher (Interscience Bag Mixer 400, France). The homogenates were incubated at 37 ± 1 °C for 24 h in incubator (Binder BD115, Germany) [23]. Following incubaon, 100 µL of the enrichment culture was plated onto Tryptone Bile X-Glucuronide agar (TBX; Oxoid CM0945, United Kingdom) supplemented with 8 µg/mL CN (Sigma-Aldrich, St. Louis, MO, USA) and incubated at 37 ± 1 °C for 24 h. Aﬅer incubaon typical green colonies presumed to be E. coli (one colony per sample) were sub-cultured on Columbia Agar supplemented with 5 % sheep blood (CBA; Oxoid CM0331, United Kingdom) and incubated at 37 ± 1 °C for 24 h [24]. Pure colonies were preserved in Tryptone Soya Broth (TSB; Oxoid CM0129, United Kingdom) containing 20 % glycerol and stored at -20 °C in deep freezer (Bosch GSN33VWE0N, Poland). Idenﬁcaon of E. coli isolates was performed using Matrix-Assisted Laser Desorpon Ionizaon-Time of Flight Mass Spectrometry (MALDI-TOF MS; Bruker Daltonics GmbH & 2 of 8

Gentamicin-resistant E. coli in chicken meat samples / Seyda Şahin UNIVERSIDAD DEL ZULIA Serbiluz Sistema de Servicios Bibliotecarios y de Información Biblioteca Digital Repositorio Académico Co. KG, Bremen, Germany). For MALDI-TOF MS idenﬁcaon, a fresh bacterial colony grown on CBA was transferred onto a polished steel target plate and overlaid with 1 µL of α-cyano-4- hydroxycinnamic acid matrix soluon. Aﬅer air-drying, spectra were acquired using the Bruker Biotyper system according to the manufacturer’s instrucons, and idenﬁcaon was performed by comparison with the reference database. Only isolates with MALDI-TOF MS scores ≥ 2.3 were accepted as E. coli at the species level [25]. Preliminary conﬁrmaon of CN R E. coli strains was carried out using the disk diﬀusion method, and deﬁnive phenotypic resistance assessment was performed by the broth microdiluon technique to determine MIC values, in accordance with the guidelines of the European Commiee on Anmicrobial Suscepbility Tesng (EUCAST) [26]. Anmicrobial suscepbility tesng using broth microdiluon The in vitro anmicrobial suscepbility of the CN R E. coli strains was determined using broth microdiluon with the BD Phoenix™ automated test panels (NMIC-433, Becton Dickinson, Sparks, MD, USA). All suscepbility tests were performed according to the manufacturer’s instrucons. Each E. coli strains was tested against the following anmicrobial agents: Amikacin (AK), CN, Ampicillin (AMP), Amoxicillin/Clavulanate (AMC), Ampicillin/ Sulbactam (A/S), Piperacillin/Tazobactam (P/T), Cefazolin (CFZ), Cefuroxime (CXM), Ceﬅriaxone (AXO), Ceﬅazidime (CAZ), Cefepime (FEP), Ceﬅolozane/Tazobactam(C/T), Ciproﬂoxacin (CIP), Levoﬂoxacin (LEV), Ertapenem (ETP), Imipenem (IMI), Meropenem (MERO), Colisn (CT), Tigecycline (TGC) and Trimethoprim/Sulfamethoxazole (SXT). The CT, TGC, C/T, P/T, ETP, IMI, and MERO are authorized for use in human medicine. These anmicrobials were included in the study because they are part of the standardized NMIC surveillance panel. Anmicrobial suscepbility tesng was performed in accordance with the recommendaons of the EUCAST [26]. MIC values were interpreted using EUCAST epidemiological cut-oﬀ values (ECOFF). Isolates with MIC values at or below the ECOFF were classiﬁed as wild-type (WT), indicang the absence of acquired resistance mechanisms, whereas isolates with MIC values above the ECOFF were classiﬁed as non-wild-type (NWT). For descripve purposes, WT isolates were considered phenotypically suscepble, while NWT isolates were considered resistant. Muldrug resistance (MDR) was deﬁned as resistance to three or more anmicrobial classes. The E. coli ATCC 25922 was used as a quality control strain, as recommended by EUCAST. RESULTS AND DISCUSSION Anmicrobial suscepbility tesng of CN R E. coli strains (n = 50) obtained from chicken meat samples revealed varying levels of resistance to across diﬀerent classes of anbiocs. The highest resistance rates were found for 100 % to AMP and 88 % to SXT. High levels of resistance were also detected against 64 % to CIP, 62 % to LEV, 50 % to AMC and CFZ, 48 % to AXO and CXM, and 42 % to A/S, respecvely. The lowest resistance rates were 2 % to CT and TGC (TABLE I; FIG. 1). On the other hand, all E. coli strains were found to be suscepble to AK, C/T, P/T ETP, IMI, and MERO. In the present study, 96 % (n = 48) of the strains exhibited resistance to at least three diﬀerent classes of anbiocs and were therefore classiﬁed as MDR. These results demonstrate that mulple anbioc resistance is widespread among chicken derived CN R E. coli strains. The high resistance rates against β-lactam, folate pathway inhibitor, and FQ anbiocs, in addion to CN resistance, highlight the potenal public health risks associated with the consumpon of contaminated chicken meat (TABLE I). FIGURE 1. MIC based anmicrobial suscepbility proﬁles of CN R E. coli strains from chicken meat. Amikacin (AK), Gentamicin (CN), Ampicillin (AMP), Amoxicillin/Clavulanate (AMC), Ampicillin/Sulbactam (A/S), Piperacillin/Tazobactam (P/T), Cefazolin (CFZ), Cefuroxime (CXM), Ceﬅriaxone (AXO), Ceﬅazidime (CAZ), Cefepime (FEP), Ceﬅolozane/ Tazobactam(C/T), Ciproﬂoxacin (CIP), Levoﬂoxacin (LEV), Ertapenem (ETP), Imipenem (IMI), Meropenem (MERO), Colisn (CT), Tigecycline (TGC) and Trimethoprim/Sulfamethoxazole (SXT) R: Resistant S: Suscepble 3 of 8

Revista Cienﬁca, FCV-LUZ / Vol. XXXVI UNIVERSIDAD DEL ZULIA Serbiluz Sistema de Servicios Bibliotecarios y de Información Biblioteca Digital Repositorio Académico TABLE I MIC distribuon of gentamicin-resistant Escherichia coli strains from chicken meat samples (n; %) Anbioc Class Anmicrobial Agent ECOFF Value (μg/mL) MIC Range (µg/mL) R S n (%) Aminoglycoside Amikacin (AK) > 8 8-32 0 50 (100 %) Gentamicin (CN) > 2 2-8 50 (100 %) 0 β-lactam Penicillins Ampicillin (AMP) > 8 4-16 50 (100 %) 0 1 st Generaon Cephalosporins Cefazolin (CFZ) > 4 4-32 25 (50 %) 25 (50 %) 2 nd Generaon Cephalosporins Cefuroxime (CXM) > 8 4-16 24 (48 %) 26 (52 %) 3 rd Generaon Cephalosporins Ceﬅazidime (CAZ) > 4 1-8 19 (38 %) 31 (62 %) Ceﬅriaxone (AXO) > 2 1-4 24 (48 %) 26 (52 %) 4 th Generaon Cephalosporins Cefepime (FEP) > 4 1-8 8 (16 %) 42 (84 %) 3 rd Generaon Cephalosporins with β-lactamase inhibitors Ceﬅolozane/Tazobactam (C/T) > 2 2/4-8/4 0 50 (100 %) Aminopenicillins with β- lactamase inhibitors Piperacillin/Tazobactam (P/T) > 8 4/4-16/4 0 50 (100 %) Amoxicillin/Clavulanate (AMC) > 8 2/2-16/2 25 (50 %) 25 (50 %) Ampicillin/Sulbactam (A/S) > 8 1/8- 8/8 21 (42 %) 29 (58 %) Fluoroquinolones Ciproﬂoxacin (CIP) > 0.5 0.0625-1 32 (64 %) 18 (36 %) Levoﬂoxacin (LEV) > 1 0.5-2 31 (62 %) 19 (38 %) Polymyxins Colisn (CT) > 2 1-4 1 (2 %) 49 (98 %) Carbapenems Ertapenem (ETP) > 0.5 0.25-1 0 50 (100 %) Imipenem (IMI) > 4 0.25-8 0 50 (100 %) Meropenem (MERO) > 8 0.125-8 0 50 (100 %) Glycylcycline Tigecycline (TGC) > 0.5 0.5-2 1 (2 %) 49 (98 %) Folate pathway inhibitors Trimethoprim/ Sulfamethoxazole (SXT) > 4 2/38- 8/152 44 (88 %) 6 (12 %) n = 50 strains. R: Resistance S: Suscepble n: number of isolates; %: percentage of isolates. Breakpoints were applied according to EUCAST. ECOFF: Epidemiological cut-oﬀ values Gentamicin a member of the aminoglycoside anbioc class, is an important anmicrobial agent widely used in both Veterinary Medicine and human healthcare. It has long been applied in poultry producon, parcularly for the treatment of sepcemia, colibacillosis, and respiratory tract infecons caused by E. coli [27]. However, because of its requirement for parenteral administraon and the potenal risk of ssue residues, the use of CN in the poultry sector has been reportedly declined in recent years [28]. Despite this, the high rate of resistant strains sll being isolated indicates the extensive historical use of CN and the genec transferability of aminoglycoside resistance. CN resistance is most commonly mediated by AMEs, including aminoglycoside acetyltransferases, O-nucleodyltransferases, and O-phosphotransferases, which enzymacally inacvate the drug [16]. CN resistance is oﬅen mediated by plasmid- borne resistance genes. These plasmids may co-harbor genes conferring resistance not only to aminoglycosides but also to β-lactam, folate pathway inhibitor, and FQ anbiocs [29]. The localizaon of these resistance genes on mobile genec elements facilitates their horizontal transfer and long- term maintenance in the agri-food chain, even in the absence of current selecve pressure [30]. Although the use of CN in Türkiye is currently subject to strict regulatory control in line with EU regulaons, relavely high resistance rates are sll reported. Indeed, CN resistance among E. coli isolates from diﬀerent poultry farms have been reported to range between 9.8 and 22.9 % [12]. This observaon may reﬂect the impact of historical anmicrobial use and the persistence of aminoglycoside resistance genes within poultry-associated bacterial populaons. Due to the absence of maximum residue limits for CN in poultry within the EU, in ovo administraon or any other applicaon of CN in poultry producon is not permied [31]. Consequently, low levels of CN resistance are generally reported among poultry-associated E. coli isolates in the EU, reﬂecng the eﬀecveness of regulatory restricons and anmicrobial monitoring policies. Furthermore, the level of CN resistance in indicator E. coli isolates from broilers and faening turkeys across EU Member States has been reported to be consistently low, ranging between 2.8 % and 3.5 % [32]. In contrast, higher frequencies of CN resistance have been reported in convenonally raised poultry in countries where in ovo CN use has historically been pracced, such as the United States [33]. Davies et al. [33] demonstrated that CN resistance was signiﬁcantly more prevalent among E. 4 of 8

Gentamicin-resistant E. coli in chicken meat samples / Seyda Şahin UNIVERSIDAD DEL ZULIA Serbiluz Sistema de Servicios Bibliotecarios y de Información Biblioteca Digital Repositorio Académico coli isolates from convenonally raised broilers and suggested that the use of CN supplemented in ovo vaccines may act as an important selecve factor for resistance development in poultry producon systems [18 , 33 , 34]. The present study analyzed retail chicken meat rather than on-farm samples, CN R E. coli detected at the retail level may originate from colonized birds carrying resistant strains from the producon phase, which can persist through slaughter and processing. In this context, the use of CN supplemented in ovo vaccines has been suggested as a potenal factor for the inial selecon of resistant E. coli in broilers, which may subsequently contaminate carcasses and meat products along the food chain. In addion, cross-contaminaon during slaughtering, processing, and retail handling may further contribute to the presence of resistant bacteria in chicken meat. Together, these observaons highlight that CN resistance detected in poultry meat likely reﬂects cumulave eﬀects of anmicrobial use pracces and food chain dynamics rather than a single point source. The nonexistent resistance to AK found in this study is in line with what is known about the structure of this aminoglycoside. AK is a semisynthec aminoglycoside that was made to avoid most AMEs. These enzymes are the main way that this class of anbiocs can become resistant. AK, in contrast to other aminoglycosides, is predominantly resistant to enzymac inacvaon by acetyltransferases, phosphotransferases, and nucleodyl transferases. Resistance to AK is primarily linked to acetylaon facilitated by aminoglycoside 6-N-acetyltransferase type Ib, an enzyme encoded by genes commonly found on mobile genec elements like plasmids, integrons, and transposons in Gram-negave bacteria. The lack of phenotypic resistance to AK in this isolates may indicate the limited prevalence of such resistance determinants in poultry associated E. coli, alongside the constrained applicaon of amikacin in food-producing animals [35 , 36]. In addion to CN R E. coli, the present study was found a similarly high rate of phenotypic resistance to β-lactam, folate pathway inhibitor, and FQ anbiocs (TABLE I). Therefore, the detecon of CN R E. coli in retail poultry meat suggests a potenal role of poultry products as reservoirs for MDR bacteria, although contaminaon may occur at various points along the food chain, from producon to retail handling. However, one of the limitaons of this study is that resistance was evaluated only at the phenotypic level, and aminoglycoside resistance genes were not examined genotypically. The ﬁndings of this study are generally consistent with reports from several studies. Although direct comparison of AMR prevalence between broiler isolates derived from (e.g., cecal or farm samples) and retail chicken meat is limited by diﬀerences in sampling matrices, several studies, including our previous ﬁndings on poultry cecal isolates in Türkiye, indicate that AMR E. coli is already established at the producon level [12 , 37 , 38]. The detecon of resistant E. coli in retail poultry meat reported in mulple studies further suggests that these resistant populaons may persist and be disseminated along the agri-food chain, from primary producon to market products. For instance, in a recent comparave analysis of convenonal and anbioc-free retail chicken meat, E. coli was detected in approximately 20.3 % of samples, and MDR resistance (38.2 %), including resistance to AMP, SXT, and TET was prevalent across both producon systems, highlighng persistent AMR in poultry meat products [39]. Similarly, in a study from Romania analyzing chicken meat, E. coli isolates frequently exhibited high resistance rates to mulple anbioc classes including TET (80 %), AMP (80 %), SMX (73,33 %), CHL (70 %), nalidixic acid (NAL) (60 %), CIP (56.66 %), CTX (46.66 %), CAZ (43.33 %) and CN (40 %), underscoring the public health relevance of AMR in poultry meat. Moreover, more than 70 % of the isolates proved to be MDR [40]. Consistent with previous work retail poultry products, these ﬁndings emphasize that AMR in poultry meat reﬂects a complex interplay of producon pracces, bacterial contaminaon, and food chain dynamics rather than a single point source [41]. It is esmated that in most developed countries, approximately 50-80 % of all anbiocs produced are administered to food-producing animals [5]. Anmicrobials such as AMP, SXT, and TET have long been used in veterinary medicine to prevenon and treatment in food animals [12]. According to the WHO classiﬁcaon, AMP, SMX, and TET are categorized as “highly important anmicrobials” due to their essenal role in human medicine [17]. According to the latest report from the EU, E. coli strains have shown the highest resistance rates to AMP, SXT and TET [30]. In the present study, CN R E. coli strains exhibited 100 % resistance to AMP, 88 % to SXT, 64 % to CIP, and 62 % to LEV. These ﬁndings suggest that CN R E. coli strains may serve as an important reservoir for anmicrobial resistance genes across diﬀerent anbioc classes. Furthermore, resistance to CIP and NAL has also been reported as widespread among poultry isolates in European countries [32], which could exert selecon pressure explaining the high percentage of resistance observed in the present study. The ﬁndings of this study regarding the resistance proﬁles of E. coli strains are largely consistent with the data reported by the European Food Safety Authority (EFSA) and the European Centre for Disease Prevenon and Control (ECDC) [36]. These results conﬁrm the high levels of resistance of E. coli strains to AMP, SXT, and CIP as well as the limited resistance to CT, TGC. All CN R E. coli strains showed 100 % suscepbility to P/T, C/T, and carbapenems (ETP, IMI, and MERO). This is a posive ﬁnding, as these anmicrobials are primarily reserved for human medicine and are not authorized for use in livestock producon. The limited resistance found likely reﬂects reduced selecve pressure in the poultry sector, highlighng the eﬀecveness of anmicrobial stewardship and regulatory policies [36]. However, sporadic detecon of resistance to last resort anmicrobials, including the idenﬁcaon of TGC resistant and mcr-1 E. coli in poultry and poultry meat samples in Türkiye, underscores the need for connuous and integrated anmicrobial resistance surveillance along the agri-food chain [1 , 36 , 40 , 42 , 43]. Fluoroquinolones are commonly used as ﬁrst-line anbiocs in the treatment of E. coli infecons [44]. These agents are widely prescribed to manage bacterial infecons in humans, poultry and other animals. Enroﬂoxacin (ENR), a member of the FQ class is frequently administered by veterinarians to prevent early chick mortality and reduce disease transmission [45]. 5 of 8

Revista Cienﬁca, FCV-LUZ / Vol. XXXVI UNIVERSIDAD DEL ZULIA Serbiluz Sistema de Servicios Bibliotecarios y de Información Biblioteca Digital Repositorio Académico However, E. coli strains obtained from poultry meat in Türkiye have been reported to exhibit high levels of resistance, reaching up to 100 %, to quinolones/FQ including CIP, ENR, LEV, Nalidixic acid (NAL), and Norﬂoxacin [9]. These ﬁndings should serve as a warning to the poultry industry to exercise cauon in the use of FQ during producon. In this context, further studies with larger sample sizes are needed to beer determine the prevalence and mechanisms of FQ resistance. In the present study, resistance to FQ anbiocs was showed at 64 % for CIP and 62 % for LEV (TABLE I). EFSA/ ECDC [36] reported similarly high resistance rates, with 54.3 % CIP resistance detected in in E. coli isolates from broilers. Similarly, high levels of resistance to FQ have also been reported by Braelan et al. [40] in E. coli isolates obtained from chicken meat samples in Romania, with a CIP resistance rate of 56.66 %. In addion, Habib et al. [46] found that 80 % of supermarket chicken meat derived extended-spectrum β-lactamase (ESBL)- producing E. coli isolates in the United Arab Emirates were resistant to CIP. These ﬁndings support the global nature of FQ resistance among E. coli in poultry products and align with the high CIP resistance observed in the present study. Trimethoprim/Sulfamethoxazole shows bacteriostac properes when used alone; however, its combinaon produces a bactericidal eﬀect by successively inhibing two enzymes in the folate synthesis pathway [47]. In the present study, resistance to SXT was detected in 88 % CN R E. coli strains. Similarly, several studies have been reported high levels of SXT resistance in E. coli isolates from chicken meat samples in Brazil and Romania [39 , 40]. According to recent reports, Aminopenicillin resistance is common among commensal E. coli isolates from food-producing animals in EU countries. The prevalence was reported as 44.7 % in broilers and 55.2 % in turkeys [48]. AMC, which belongs to the aminopenicillin class, has been commercially available since 1981 and is widely used in European countries to treat a variety of infecons in both humans and animals. However, this extensive use may contribute to the development of acquired resistance in both pathogenic and commensal bacteria [49]. The ﬁndings from this study revealed that resistance to AMC was 50 % among CN R E. coli strains. In addion, resistance to third- generaon cephalosporins was found to be 38-48 % of the isolates for CAZ and AXO, respecvely. It has been reported that AMC resistance may facilitate the selecon and disseminaon of ESBL and AmpC β-lactamase producing bacteria due to its overlapping acvity spectrum with second and parally third- generaon cephalosporins [12 , 49]. These results are consistent with the ﬁndings of the present study. However, there remains a lack of comprehensive data on how the AMC combinaon speciﬁcally selects for resistance in animals. CONCLUSION This study demonstrated that raw chicken meat available for consumers in Türkiye was frequently contaminated with CN R E. coli strains. The research provides comprehensive phenotypic data on CN R E. coli strains collected from chicken meat samples in Sivas province, Türkiye. A high prevalence of resistance to AMP, SXT and CIP was found, indicang resistance to mulple classes of anmicrobials among the strains. These ﬁndings suggest that the consumpon of undercooked chicken meat or foods cross-contaminated with CN R E. coli strains may pose a signiﬁcant risk to public health and highlight the need for connuous monitoring and responsible anmicrobial use in poultry producon. In this context, more research ulizing MIC based techniques would provide a beer assessment of resistance phenotypes and improve surveillance of AMR in the poultry food chain. Taken together, these ﬁndings highlight that AMR in the poultry food chain is not conﬁned to a single producon stage or country. Accordingly, eﬀecve control strategies should rely on coordinated, policy based acons supported by governmental regulaons. In parallel, prevenve measures such as improved biosecurity, vaccinaon, and beer hygiene are essenal to reduce the reliance on anmicrobials. Conﬂict of interest The author declare no potenal conﬂicts of interest. Ethics approval Ethical approval is not required for this study. 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