Introduction

Salmonella is one of the most common causes of bacterial foodborne illness in humans (Galán-Relaño et al., 2023). The occurrence of Salmonella contamination is a major challenge to the poultry industry and regulatory authorities since it is considered the leading cause for foodborne infections worldwide (CDC, 2024; Pavelquesi et al., 2023). Nontyphoidal Salmonella spp. are frequently detected in food of animal sources, mainly poultry meat and eggs (Al-Qadiri et al., 2008; Castro-Vargas et al., 2020). In the United States, it was reported that nontyphoidal Salmonella infection is the most prevalent bacterial foodborne disease (Akil and Ahmad, 2019). In another study in the United States, the organism was isolated from 8.6% of chicken breast samples; more than 73.1% of the isolated Salmonella spp. exhibited resistance to more than one antibiotic, and 48.1% exhibited resistance to more than three types of antibiotics (multi drug resistance (MDR)) (Mujahid et al., 2023).

Foodborne infection by Salmonella can be severe and poses an additional public health burden when the detected isolates are resistant to antibiotics (NARMS, 2024). Chicken meat is the principal foodborne mode of transmission for Salmonella spp. and the cause of most salmonellosis cases (Dewey-Mattia et al., 2018). Several studies indicated that approximately 25% of the salmonellosis cases are transmitted through contaminated raw poultry (Chai et al., 2017; Smadi and Sargeant, 2013). Transmission routes of Salmonella spp. are contaminated feed, unhygienic farming, slaughtering, processing, and packing practices, and the risk for infection is exacerbated through transportation, storage, retailing, and handling or preparation by consumers. Nevertheless, poultry may act as a primary Salmonella reservoir contaminating chicken meat and eggs (Chai et al., 2017).

As a public health concern, emerging antibiotic resistance by foodborne pathogens is a global challenge since AMR bacteria may elicit a life-threatening illness. Globally, it is estimated that Salmonella is associated with 700,000 deaths. Of these, 23,000 mortalities take place annually in the United States (Dadgostar, 2019; Nair et al., 2018). Many recent studies reported a progressive increase in the occurrence of resistance to commonly used antibiotics of Salmonella spp. isolated from humans or animals (Borges et al., 2019; Pavelquesi et al., 2023; Perin et al., 2020). Isolates of Salmonella spp. showing MDR involved in infections contain genes that code for antibiotic resistance such as bla_TEM (beta-lactam-resistance gene (RG)), sul1 and sul2 (sulfonamide RGs), and tetB (tetracycline RG) (Cunha-Neto et al., 2018).

It was reported that nontyphoidal Salmonella isolates that are resistant to widely used antibiotics such as ampicillin, ceftriaxone, ciprofloxacin, fluoroquinolones, cephalosporin, sulfonamides, and tetracyclines were responsible for most of the hospitalizations and mortalities (Li et al., 2013; Mukherjee et al., 2019; Pavelquesi et al., 2023, Zhu et al., 2017). Since it is difficult to eliminate Salmonella from its reservoir, it is essential to target Salmonella spp. in the animal food supply chain, apply strict precautionary measures, and develop new treatment strategies to reduce public health risk.

This study is one of few studies to detect the occurrence of Salmonella in the slaughterhouse and retail market in Jordan. Therefore, the study aimed to investigate the occurrence and the antibiotic resistance profiles of Salmonella spp. in chilled raw chicken meat collected from retail markets and from poultry slaughter facilities.

Materials and Methods

Sample collection

Between October 2022 and August 2024, a total of 700 chilled raw chicken meat samples were collected under aseptic conditions (International Standard method (ISO) 17604:2015; ISO/TS 17728:2015) as follows: (i) eviscerated chicken carcasses at the main broiler chicken abattoirs (n= 200); (ii) eviscerated chicken carcasses from the retail markets (n= 400), and (iii) chicken breasts (n = 100) from the retail markets (supermarkets, small grocery stores, and butcher shops). Samples were kept refrigerated during transportation (<8°C) and were microbiologically examined within 4 h.

Bacterial isolation and serotyping

Chicken meat samples of 25 g were diluted in 225 mL of sterile buffered peptone water (BPW) (Oxoid, CM1049), then 10-fold sequentially diluted and examined for aerobic plate count (APC) by spread plating 0.1 mL of the serially diluted sample in duplicate on tryptone soy agar (TSA) plates (Oxoid, CM0131). Plates were enumerated after being incubated at 30°C for 72 h, and the counts were determined and reported as Log₁₀ CFU/g of the sample (ISO 4833-2:2013).

The process of detecting, isolating, and identifying Salmonella spp. was conducted according to the ISO method (ISO 6579-1:2017). Pre-enrichment in a nonselective medium was conducted in triplicate with a 25-g chicken sample being homogenized in 225 mL of sterile BPW. The sample with BPW was aseptically placed in a stomacher sterile strainer-filter bag and pounded using a stomacher for 2 min, and then incubated at 37°C for 18 h. Thereafter, aliquots of 0.1 mL of the pre-enrichment BPW were transferred into 10 mL of Rappaport-Vassiliadis soya peptone (RVS broth) (Oxoid, CM0866) and Muller-Kauffmann tetrathionate-novobiocin broth (MKTTn broth) (Oxoid, CM1048), respectively. The inoculated RVS and MKTTn broths were incubated at 41 and 37°C for 24 h, respectively. Then, 1 mL of the incubated RVS and MKTTn broths were consecutively diluted (10-fold) and a 100 µl aliquot of each 10⁻² dilution was then sub-cultured by streaking onto xylose lysine deoxycholate (XLD) agar (Oxoid, CM0469) and Salmonella Shigella (SS) agar (Oxoid, CM0099) as differential selective media. Eventually, the plates were incubated at 37°C for 24 h. Presumptive Salmonella isolates were further confirmed by sub-culturing onto lysine iron (LI) agar (Oxoid, CM0381) and triple sugar iron (TSI) agar (Oxoid, CM0277). Positive cultures were then serotyped by agglutination test for Salmonella antigens (Oxoid Salmonella latex test, FT0203). Serotyping screening to identify Salmonella Typhimurium and Salmonella Enteritidis was carried out using agglutination test for O and H antigens (Thermo Fisher Scientific-Remel R30953101, R30952901).

Antimicrobial susceptibility testing

Salmonella inocula (invA gene-positive strains) were prepared as a suspension from Mueller-Hinton broth (Oxoid, CM0405) with turbidity equivalent to a 0.5 McFarland standard (10⁸ CFU/mL), adjusted using a spectrophotometer set at 625 nm. Ten classes of antibiotics were used to test for the susceptibility of the isolated Salmonella spp. for the antibiotics used in salmonellosis infection (Clinical and Laboratory Standards Institute (CLSI), 2020; Hudzicki, 2009). The abbreviations and concentrations of these antimicrobial agents (AGs) according to Thermo Fisher Scientific-Oxoid are beta-lactam antibiotics: ampicillin (AMP, 10 μg) and amoxicillin/clavulanic acid (AMC, 20/10 μg); beta-lactam cephalosporin antibiotics: ceftazidime (CAZ, 30 μg) and cefotaxime (CTX, 30 μg); aminoglycoside gentamicin (CN, 10 μg); protein synthesis inhibitors: chloramphenicol (C, 30 μg) and tetracycline (TE, 30 μg); beta-lactam carbapenem imipenem (IPM, 10 μg); sulfonamide sulfafurazole (SF, 300 μg); and fluoroquinolone ciprofloxacin (CIP, 5 μg). All the antimicrobial disks were obtained from Thermo Fisher Scientific-Oxoid (CT0003B, CT0223B; CT0412B; CT0166B; CT0024B; CT0013B; CT0054B; CT0455B; CT0075B; and CT0425B, respectively). For comparison purposes (control), Escherichia coli ATCC 25922 was used. Salmonella isolates’ vulnerability to the action of antibiotics was depicted as resistant (R), intermediate (I), or susceptible (S), according to the CLSI (2020) guidelines. Salmonella spp. that were resistant to three or more antimicrobials were defined as MDR (NARMS, 2017).

Molecular verification and detection of antimicrobial resistance genes

Salmonella total genomic DNA was extracted from the recovered isolates cultivated in Mueller-Hinton broth at 37°C for 18 h using PureLink™ Genomic DNA Mini Kit (K182002) (Thermo Fisher Scientific) following the manufacturer’s instructions. The extracted DNA was qualitatively and quantitatively analyzed using 1.5% (w/v) agarose gel electrophoresis and Nano Drop One Microvolume UV-Vis Spectrophotometer (Thermo Scientific, Asheville, NC), respectively. PCR amplification was performed using SimpliAmp™ Thermal Cycler (Thermo Fisher Scientific). The amplified PCR products were examined through 1.5% (w/v) agarose gel electrophoresis. Ultraviolet (UV) light was used to visualize the separated DNA fragments on the gel with a 100 bp marker.

Molecular verification of Salmonella positive isolates was carried out by detection of Salmonella-specific invasive encoding gene (invA). PCR amplification targeting the invA gene, known for its role in bacterial invasion, was conducted following the method described by Rahn et al. (1992). Molecular confirmation of Salmonella spp. was achieved using specific primers that produced a 284 bp amplicon: F139 forward primer (5'-GTGAAATTATCGCCACGTTCGGGCAA-3') and R141 reverse primer (5'-TCATCGCACCGTCAAAGGAACC-3').

Salmonella isolates that elicited resistance to a class of AGs were examined for the presence of RGs using a PCR technique. The presence of RGs associated with bla_TEM for beta-lactams, tetB for tetracycline, and sul1 and sul2 for sulfonamide was detected by PCR amplification. The primer sequences, predicted sizes, and thermocycling conditions for PCR amplification of the studied RGs are depicted in Table 1.

Statistical analysis

The Statistical Analytical System (SAS, 2011) (SAS Inst. Inc., Cary, N.C., USA) package (version 8.2) was used to determine statistically significant differences (P < 0.05) between the prevalence rate of Salmonella spp. in correlation with (i) verification method (latex agglutination vs. invA gene) and (ii) different source and type of chicken meat using Chi-square (χ²) test. Pairwise comparisons of means (post hoc test) was performed to determine significant differences (P < 0.05) between the mean of APCs with the Tukey-Kramer adjustment.

Results and Discussion

Prevalence of Salmonella spp. isolates

This is one of few studies in Jordan that intended to demarcate the incidence of Salmonella and to examine the resistance of the isolates to commonly used antibiotics from chilled raw chicken meat samples obtained from broiler chicken abattoirs and retail markets. Out of 700 samples, a total of 106 (15.14%) isolates tested were positive for Salmonella-(invA) gene (Table 2). All the isolated Salmonella were identified by biochemical methods and confirmed by discerning the Salmonella-invasive specific gene (invA). Several previous studies used this gene to confirm the presence of Salmonella in poultry meat (Ahaduzzamana et al., 2021; Boubendir et al., 2021; Li et al., 2013). There was a significant difference (P<0.05) in the prevalence rate of isolates verified by latex agglutination as compared with PCR techniques. The Salmonella-specific (invA) gene was detected in 14.5% (29/200) of chicken carcass samples collected from abattoirs, 16.25% (65/400) of chicken carcasses from retail markets, and 12.0% (12/100) of chicken breast samples collected from retail markets (Table 2). Serotyping indicated that a total of less than 4% of the recovered isolates were identified as S. Typhimurium and S. Enteritidis.

In a recent study that aimed to examine the occurrence of Salmonella spp. in a poultry slaughterhouse in Jordan, Salmonella spp. were confirmed in 15.47% out of 635 samples collected, in which 50 (56.2%), 2 (2.2%), and 1 (1.1%) of the isolates were identified as Salmonella Infantis, S. Enteritidis, and S. Typhimurium, respectively (Gharaibeh, et al., 2024). This study pointed out that Salmonella spp. were recoverable at the highest rate (37.8 %) from the post-chiller and the lowest (3%) when using the farm drag swab method.

In the current study, chicken carcass samples collected from retail markets showed the highest degree of contamination, while the skinless chicken breast samples had the lowest. The reasons behind the lower prevalence in chicken breast could be because of the removal of skin that harbors Salmonella as well as the use of food sanitizers and UV light at various stages of processing and packaging that provides bactericidal and bacteriostatic activity. In a study by Golden and Mishra (2020), the prevalence rate of Salmonella spp. increased from 14.3% in broiler chickens to 19.0–23.0% in retail chicken. In another study in China, the overall occurrence of Salmonella in chicken meat during the slaughtering process at an abattoir was 30.14%, where the organism was isolated at the rate of 48.0%, 18.8%, 31.3%, and 14.0% from cecal content, chicken carcasses, chicken meat cuts, and frozen chicken meat, respectively. The predominant serotypes of Salmonella were S. Enteritidis and S. Typhimurium. In comparison, the occurrence of Salmonella in chicken meat after the slaughtering process and before transportation and distribution was 18.0% in 2017, 12.6% in 2018, and 15.1% in 2019 (Pavelquesi et al., 2023). In the United States, samples of raw chicken breast taken from retail markets were reported to be contaminated by Salmonella (4.2%) and Campylobacter (8.6%), in which a total of 10.82% of samples contained one or both bacterial species (Mujahid et al., 2023). The variations in the prevalence rates of Salmonella spp. in different countries and between versatile studies that addressed the same issue could be attributed to the variations in poultry farming practices, method of sampling and sampling seasons, and the differences in detection and isolation methods applied. According to microbiological criteria for the Near East issued by Food and Agriculture Organization of the United Nations & World Health Organization (FAO/WHO, 2002), Salmonella should not be detected even in 1 g sample of raw poultry meat. To some extent, it is impractical to avoid contamination by Salmonella, since multiple contamination sources are possible throughout the farming, slaughtering, processing, and distribution supply chain. Nevertheless, it is important to confirm that S. Enteritidis and S. Typhimurium are not detected in chicken meat (FAO/WHO, 2002), and the target approach is to minimize cross contamination using a preventive control strategy based on target risk promoted by global food safety management systems such as HACCP/HARPC and ISO 22000.

In the current study, APC provided a general indication of microbial contamination and the hygienic conditions applied during processing, distribution, and marketing. A total microbial count of less than 6.0 Log₁₀ CFU/g (Table 2) was observed for chicken meat in this study, which was within the acceptable microbiological criteria for chilled poultry meat (FAO/WHO, 2002). However, as evident in Table 2, the occurrence of Salmonella in raw chicken exceeds the reference standards, making it necessary to reduce the level of raw chicken contamination with Salmonella.

Antimicrobial susceptibility testing

Table 3 and Figure 1 show the susceptibility of 106 Salmonella isolates to 10 classes of AGs, revealing that more than 98% of the isolates were resistant to one or more of the tested AGs, and only 1.9% were susceptible to all tested drugs. High resistance rates were observed against beta-lactams group of ampicillin (75.5%) and amoxicillin/clavulanic acid (45.3%); sulfonamide-sulfafurazole (66.0%); tetracycline (61.3%); and ciprofloxacin (42.5%). However, the isolates exhibited lower level of resistance toward cefotaxime (24.5%), chloramphenicol (19.8%), imipenem (11.3%), ceftazidime (9.4%), and gentamicin (7.5%). Gentamicin showed the highest efficacy against all isolated Salmonella, where 80.2% of the isolates exhibited sensitivity to the antibiotic. Gharaibeh et al. (2024) reported that Salmonella detected in chicken samples collected from an abattoir in Jordan showed high degrees of resistance against ciprofloxacin, tetracycline, sulfamethoxazole/trimethoprim, and ampicillin. A lower level of resistance was elicited against cefotaxime, gentamicin, and ceftazidime. Several studies reported high resistance rate among Salmonella isolates detected in chicken meat against beta-lactams (ampicillin), sulfonamide, and tetracycline (Gharaibeh et al., 2024; Li et al., 2013; Mujahid et al., 2023; Pavelquesi et al., 2023; Punchihewage-Don et al., 2024; Zhu et al., 2017); amoxicillin/clavulanic acid (Pavelquesi et al., 2023); and ciprofloxacin and quinolone-nalidixic acid (Gharaibeh et al., 2024; Vinueza-Burgos et al., 2016; Voss-Rech et al., 2017; Zhu et al., 2017), whereas Salmonella isolates showed lower level of resistance with a variation in sensitivity to gentamicin, cefotaxime, chloramphenicol, imipenem, and ceftazidime according to the same studies.

Figure 1. Prevalence of antibiotic resistance among Salmonella isolates (%) recovered from chilled raw chicken meat at chicken abattoirs and local markets in Jordan.

A growing tendency of resistance to extended spectrum beta-lactam cephalosporins (ESBLs) was reported in Enterobacteriaceae worldwide (Dierikx et al., 2010). Bacteria resistant to ESBLs are often isolated from the intestinal tract of animals and have been isolated from poultry, turkey, cattle, swine, cats, dogs, horses, and wild animals (Costa et al., 2006; Hasman et al., 2005;; Li et al., 2007; Nair et al., 2018; Vo et al., 2006). According to the Food and Drug Administration (FDA), Salmonella spp. isolated from ground beef showed remarkable level (38.5%) of resistance to ceftriaxone (a broad-spectrum cephalosporin antibiotic) and were MDR (FDA, 2017).

ESBLs producing Salmonella act to cleave the beta-lactam ring to inactivate such antimicrobials (Chon et al., 2015). This may limit medical treatment of salmonellosis using cephalosporins as drugs of choice. The decrease in susceptibility of Salmonella to antibiotics commonly used to treat salmonellosis could be because of the use of these drugs extensively in both human and veterinary medicine (CDC, 2019; Lai et al., 2014; Voss-Rech et al., 2017). A considerable surge in resistance of Salmonella spp. to protein synthesis inhibitors, tetracyclines, and bacteriostatic sulfonamides, which are used as broad-spectrum agents was reported in several studies (Nair et al., 2018; Pavelquesi et al., 2021). Antibiotics are sometimes illegally or irresponsibly used as growth promoter additives in animal feed. Also, antibiotics are broadly used in veterinary medicine. These factors may have contributed to the progressive increase in antibiotic resistance, which may pose a serious public health threat. Hence, it is necessary to preclude potential causes of antibiotic resistance and control the transfer of antibiotic-resistant microbes from livestock to the human population. One study reported that resistance of Salmonella spp. to antibiotics was more prevalent in conventional poultry farms compared to nonconventional (antibiotic-free) farms (Gebreyes et al., 2006).

As shown in Figure 1, 41.5% (n = 44) of recovered Salmonella spp. were resistant to three or more of the studied antimicrobials and are considered to be MDR isolates. Resistance to up to seven categories of antimicrobials was found in 2.8% of isolates, presenting a health concern considering the cross connection between broiler farms, slaughtering environments, and distribution and sale of human food. Several studies from different geographical areas have confirmed high rates of MDR (>50% of isolates) in recovered Salmonella from broiler and layer farms, abattoirs, and in poultry meat (Furukawa et al., 2017; Gharaibeh et al., 2024; Moe et al., 2017; Mujahid et al., 2023; Pavelquesi et al., 2023; Perin et al., 2020; Sodagari et al., 2015; Zhu et al., 2017).

The emergence of MDR foodborne bacteria is a global health problem, and there is a need to control the overuse or misuse of antimicrobials in animal husbandry, which could be a major factor driving the increase in the incidence of MDR bacteria. Strict application of good agricultural practices and systems of food safety were proven to be effective in controlling MDR Salmonella food infection, otherwise higher morbidity and mortality rates may occur from microbial foodborne illnesses. It is also beneficial to review the 2016–2017 NARMS Integrated Summary, which provides consolidated antimicrobial susceptibility testing (AST) data collected in the United States. Data were grouped from clinical isolates of human origin, intestinal isolates from food-producing animals at slaughterhouses, samples collected at slaughter as part of (PR/HACCP) testing, and from different types of raw meats collected at retail markets in 18 states (Mujahid et al., 2023; NARMS, 2017).

Detection of antimicrobial RGs

As shown in Table 4, the occurrence rate of bla_TEM RG was 92.5% and 52.1% among Salmonella isolates found phenotypically resistant to ampicillin and amoxicillin/clavulanic acid, respectively. The genotypic results were in agreement with those of phenotypic AST. As previously discussed, the increasing resistance to ESBLs has been observed in Enterobacteriaceae because of the effect of ESBL enzymes, in which bla_TEM is one of the most prevalent ESBL genes (Chon et al., 2015; Li et al., 2013; Zhu et al., 2017). It was indicated that Salmonella spp. recovered from chicken that are resistant to beta-lactams exhibited more than 96% bla_TEM prevalence (Moawad et al., 2017). A study carried out in Jordan indicated that ESBL genes have been identified in the recovered Salmonella isolates for samples collected from an integrated poultry abattoir, in which bla_TEM was identified as the most prevalent gene in 88.8% of the isolates (Gharaibeh et al., 2024). In another study, it was possible to identify bla_TEM in 93.4% of Salmonella isolated from broiler chickens at different slaughtering processes. bla_TEM was present in 93.4% of the beta-lactam-resistant isolates, whereas bla_CTX-M gene has been recognized in 12.7% of the isolates, and both genes were identified in 11.4% of the recovered isolates (Zhu et al., 2017).

The emerging ESBL-producing Salmonella isolates carry beta-lactam RG, which are located in transferable genetic components, (transposons, integrons, and plasmids). Hence, horizontal gene transfer (HGT) could be one of the mechanisms through which Salmonella species acquire novel genetic material, with this being the most common way for bacteria to become resistant to antimicrobials (Michaelis and Grohmann, 2023). However, some difference in results regarding the prevalence of bla_{TEM gene} among beta-lactam-resistant Salmonella could reflect different restrictions and strategies of using antibiotics applied in different countries (Sabry et al., 2020).

In the current study, among 65 phenotypically tetracycline-resistant Salmonella isolates, 89.2% (n = 58) harbored the tet(B) RG, which is considered to be a gene specific to Gram-negative bacteria (McMillan et al., 2019). The tet genes may confer resistance to tetracycline, doxycycline, and minocycline by encoding membrane-associated tetracycline efflux protein pumps that are associated with plasmids and transposons (Roberts and Schwarz, 2016). Among 98 tetracycline-resistant Salmonella spp. recovered from broiler chickens at different stages in the slaughtering process in China, 85.7% of isolates harbored at least one tet gene. The tet(C) and tet(B) genes were the most concurrent and prevalent (71.4 and 50%, respectively) (Zhu et al., 2017). Thakur et al. (2007) studied the antibiotic resistance patterns of Salmonella isolated from swine farms. Environmental samples in the form of swabs were collected from intensive and extensive farms. High resistance profiles of Salmonella spp. against tetracycline and streptomycin (78.5 and 31.5%, respectively) were reported, with S. Typhimurium var. Copenhagen showing the highest resistance against different types of antibiotics.

Among 70 sulfonamide-resistant Salmonella spp., 38.6% and 90.0% of resistant isolates harbored sul1 and sul2 genes, respectively. The mechanism of sulfonamide resistance is attributed to the possession of the sul genes (sul1, sul2, and sul3) that results in the overproduction of an insensitive form of dihydropteroate synthetase enzyme that counteracts the action of sulfonamides (Alcaine et al., 2007; Huovinen et al., 1995). These genes have been detected in major Salmonella serogroups, including S. Typhimurium S. Enteritidis, S. Hadar, and S. Heidelberg (Alcaine et al., 2007; Huovinen et al., 1995). Salmonella isolates resistant to sulfadimethoxine and trimethoprim-sulfamethoxazole combination were commonly isolated from poultry farms, which are considered the main reservoirs of antimicrobial-resistant bacteria (Chen and Jiang, 2014; Liljebjelke et al., 2017, Nair et al., 2018). Zhu et al. (2017) found that sul2 gene had the highest occurrence (97.8%), followed by sul3 (50.5%) and sul1 (50.5%) among sulfonamide-resistant Salmonella isolates recovered from broiler chicken samples.

In the present study, it was noticed that genes that code for antimicrobial-RGs (bla_TEM, tet(B), sul1 and sul2) were also detected in some of the recovered isolates. Nonetheless, these isolates showed intermediate and susceptible patterns to the tested antimicrobials. This might be because DNA sequences were entirely unexpressed or expressed at an inadequate level in vitro. Antibiotic RGs in the silent state have been detected in seafood-associated nontyphoidal Salmonella isolates in the south-west coast of India, in which 40% of chloramphenicol-susceptible strains carried the catA1 gene (Deekshit et al., 2012). RGs were also detected in susceptible and intermediately susceptible Salmonella spp. recovered from chilled chicken available in the local market in Brazil. Of the recovered Salmonella, 23.1% of the of sulfonamide-sensitive Salmonella harbored sul2 RG, 19.3% of the isolates that were sensitive or showed intermediate sensitivity to tetracycline carried the tet(B) gene, and 6.4% of the isolates that had sensitive or intermediate reaction to β-lactams had the bla_CTX gene (Pavelquesi et al., 2023). Since some antimicrobial RGs are considered to be silent in vitro, these genes could transfer and spread through horizontal gene or become active in vivo, particularly under the selective effect of antimicrobial use, and could become active after being conveyed to a new host (Adesiji et al., 2014; Deekshit et al., 2012; Stasiak et al., 2021; Yaqoob et al., 2007).

Conclusion

This study revealed different prevalence patterns of Salmonella spp. recovered from raw chicken meat. Contamination of chicken with Salmonella could be unavoidable, since multiple contamination sources may harbor the microbe during farming, slaughtering, processing, and marketing. Nevertheless, the strategy of achieving Salmonella-free raw chicken meat should become a high priority because of the emergence of antimicrobial-resistant strains. Salmonella isolates exhibited a phenotypic resistance against beta-lactams, sulfonamide, tetracycline, and ciprofloxacin. The antimicrobial-RGs bla_TEM, tet(B), sul1, and sul2 were detected among Salmonella isolates with the genotypic results tracking phenotypic AST. As it was evident in the current study, raw broiler chicken could serve as a major source of MDR Salmonella. Strict control of the use of antibiotics is prudent, since the overuse or misuse of antimicrobials in animal husbandry may trigger a recurrent occurrence of MDR bacteria that could otherwise result in higher morbidity and mortality rates because of Salmonella foodborne infections.