Cefotaxime-, Ciprofloxacin-, and Extensively Drug-Resistant Escherichia coli O157:H7 and O55:H7 in Camel Meat

The present study aimed to explore for the first time the occurrence and the antimicrobial resistance profiles of E. coli O157:H7 and O55:H7 isolates in camel meat in Egypt. Among the 110 camel meat samples examined using standardized microbiological techniques, 10 (9.1%) and 32 (29.1%) were positive for E. coli O157:H7 and E. coli O55:H7, respectively. In total, 24 isolates were verified as E. coli O157:H7, while 102 isolates were confirmed serologically as E. coli O55:H7. Multiplex PCR revealed the existence of eaeA, stx1, stx2, and EHEC-hlyA among E. coli O157:H7 and O55:H7 isolates (n = 126) at various percentages. According to their resistance against 14 antibiotics, 16.7% and 83.3% of O157:H7 isolates and 8.6% and 76.5% of O55:H7 isolates were classified into extensively drug-resistant and multi-drug-resistant, respectively, whereas 29.4% and 22.2% of E. coli isolates were resistant to cefotaxime and ciprofloxacin, respectively. The study results emphasize that camel meat may be a vehicle for multi- and extensively drug-resistant E. coli O157:H7 and O55:H7 strains, indicating a potential threat to public health. Further studies based on the molecular evidence of the antimicrobial resistance genes and enrolling a larger number of samples are recommended for a better understanding of the antimicrobial resistance phenomenon of camel-meat-originating pathogenic E. coli strains.


Introduction
Enterohemorrhagic Escherichia coli (EHEC) O157 serotype is a well-documented human foodborne pathogen able to produce diarrhea, hemorrhagic colitis (HC), and hemolytic uremic syndrome (HUS) in consumers in both developing and industrialized countries [1]. The main elements associated with the EHEC O157 pathogenicity include Shiga toxins 1 and 2 (encoded by stx1 and stx2 genes), intimin (encoded by eae gene), and EHEC hemolysin (encoded by Ehly gene). Most of the Shiga-toxin-producing Escherichia coli (STEC) O157 isolates have eae and stx2 genes [2].
Although the EHEC O157:H7 have been incriminated in most outbreaks of HC and HUS, several outbreaks caused by STEC serotype O55:H7 have been recorded in many countries. Outbreaks of HUS caused by STEC serotype O55:H7 occurred in England between 2014 and 2018 [3]. Sporadic outbreaks with E. coli O55:H7 have been reported in the Czech Republic, Italy, and Germany [4]. In July 2014, in Dorset County, England, 31 cases were linked to the O55:H7 outbreak: 13 (42%) of those patients suffered from HUS,

Collection of Samples
A total of 110 camel meat samples taken from 110 different camel carcasses were collected throughout November 2021 to March 2022 from different camel-butcher shops distributed in Beheira Governorate, Egypt. The samples (500 g each) were taken from the thigh region and were individually and aseptically packaged into a plastic bag, labeled with a number, and transferred in an icebox to the Laboratory of Food Hygiene and Control Department, Faculty of Veterinary Medicine, Mansoura University, where the microbiological examinations were performed.

Isolation and Identification of E. coli Strains
A total of 25 g from each harvested sample was aseptically homogenized with 225 mL of modified tryptone soya broth (CM0989; Oxoid-Thermo Fisher Scientific Inc., St. Leon Roth, Germany) containing vancomycin at a final concentration of 40 mg/mL. The resultant homogenate was subsequently incubated at 37 • C for 18 h. Next, the enriched culture was streaked onto sorbitol Mac Conkey agar (CM0813; Oxoid-Thermo Fisher Scientific Inc.) previously supplemented with cefixime and potassium tellurite (SR0172; Oxoid-Thermo Fisher Scientific Inc.). The plates were then incubated for 24 h at 37 • C and the grown presumptive E. coli O157:H7 and E. coli O55:H7 colorless colonies (sorbitol nonfermenting) were selected. Five to ten colonies were taken and sub-cultured onto nutrient agar (CM0003; Oxoid-Thermo Fisher Scientific Inc.) slopes for further characterization. A total of 280 colonies (colorless) were exposed to biochemical tests designed for E. coli identification, including indole, methyl red, Voges-Proskauer, and citrate tests. Typical E. coli O157:H7 and E. coli O55:H7 isolates exhibited positive reactions for indole production and methyl red tests as well as negative reactions for each of the Voges-Proskauer and citrate utilization tests. The enterohemolytic phenotype of the strains isolated was determined through the streaking of E. coli colonies on blood agar plates that contained 5% washed sheep erythrocytes, followed by incubation at 37 • C. The occurrence of a narrow hemolysis zone within 18-24 h clarifies a positive result [17].

Serological Identification of E. coli Isolates
E. coli O157:H7 and E. coli O55:H7 isolates were serologically characterized by using a rapid diagnostic E. coli antisera kit (Denka Seiken Co., Ltd., Tokyo, Japan) designed for diagnosis of the enteropathogenic serotypes, according to the manufacturer instructions. The serological characterization was performed at the Food Analysis Center, Faculty of Veterinary Medicine, Benha University, Egypt. The biochemically confirmed E. coli strains were further tested by PCR for identification of the rfb O157 marker gene of E. coli O157 using the specific primer set: F: 5'-GCGGAACAAAACCATGTGCA-3' and R: 5'-ACTGGCCTTGTTTCGATGAG-3', which was previously constructed by Sallam et al. [13] to yield an 800 bp DNA size specific for the rfb O157 gene. A twenty-five-microliter reaction mixture comprising 12.5 µL of DreamTaq Green Master Mix (Thermo Scientific, St. Leon Roth, Germany), 1 µL from each of the forward and reverse primer (10 pmol each), 1 µL of the extracted genomic DNA as a template, and 9.5 µL RNase free water added to the 25 µL final volume. The PCR amplification condition included an initial denaturation step at 96 • C for 4 min, followed by 30 cycles E. coli O157:H7 and E. coli O55:H7 strains (n = 126) isolated from camel meat were examined for the evidence of some virulence genes specific for pathotyping of the diarrheagenic E. coli as eaeA, stx1, stx2, and EHEC-hlyA. The primer sequences constructed for PCR reactions of the stx1 (614 bp) and stx2 (779 bp) genes, according to Dhanashree and Mallya [18], were 5'-acactggatgatctcagtgg-3' for stx1 forward, 5'-ctgaatccccctccattatg-3' for stx1 reverse, 5'-ccatgacaacggacagcagtt-3' for stx2 forward, and 5'-cctgtcaactgagcagcactttg-'3 for stx2 reverse. Moreover, the constructed sequences of the primer set used for PCR amplification of each gene were as follows: 5'-gtggcgaatactggcgagact-3' for sense and 5'ccccattctttttcaccgtcg-3'for antisense to yield an 890-bp DNA fragments for eaeA [19], whereas the primer set sequences for PCR amplification of hylA gene were 5'-acgatgtggtttattctgga-'3 for sense and 5'-cttcacgtgaccatacatat-'3 for antisense to yield a DNA size of 165 bp [20].

Molecular
Multiplex PCR of 50 µL volume containing 25 µL of DreamTaq Green Master Mix (Thermo Scientific, St. Leon Roth, Germany); 1 µL from each the sense and antisense primer (10 pmol each) specific for each of the stx1, stx2, eaeA, and hylA virulent genes (8 µL in total); 2.5 µL of E. coli genomic DNA as a template; and 14.5 µL RNase-free water added to a final volume of 50 µL. Multiplex PCR for stx1, stx2, eaeA, and hylA genes consisted of an initial denaturation step for 3 min at 95 • C, followed by 35 cycles of denaturation at 95 • C for 20 s, annealing at 58 • C for 30 s, and polymerization at 72 • C for 90 s. The final cycle was followed by 72 • C for 5 min as an extension step.

Prevalence of the Isolated E. coli Strains in Camel Meat Samples
Among the 110 camel meat samples tested, 10 (9.1%) samples were positive for E. coli O157:H7, which was present either alone (n = 4) or coexisting with E. coli O55:H7 (n = 6), while 32 (29.1%) camel meat samples were found positive for E. coli O55:H7, which existed either alone (n = 26) or as a mixed contamination (n = 6) with E. coli O157:H7 strains ( Figure 1). Data about the prevalence of E. coli O157:H7 and/or E. coli O55:H7 in camel meat are very limited. A study conducted on 50 camel meat samples in Iran [23] indicated that only one (2.0%) sample was contaminated with E. coli O157. Likewise, Hassan et al. [24] could not detect the enteropathogenic E. coli in any of the 15 camel meat samples examined in Qaliubiya Governorate, Egypt, although they could detect it in 13.3% (2/15), 13.3% (2/15), and 33.3% (5/15) of camel spleen, liver, and kidney samples, respectively. In the fecal sample taken from healthy camels, however, E. coli O157:H7 was isolated from 19 (19%) of 100 camels' fecal specimens collected from 100 apparently healthy camels in the middle of Iraq [25], while it was present in 3.3% from the fecal samples taken from 140 healthy camels at a slaughterhouse in the United Arab Emirates [26].

Prevalence of the Isolated E. coli Strains in Camel Meat Samples
Among the 110 camel meat samples tested, 10 (9.1%) samples were positive for E. coli O157:H7, which was present either alone (n = 4) or coexisting with E. coli O55:H7 (n = 6), while 32 (29.1%) camel meat samples were found positive for E. coli O55:H7, which existed either alone (n = 26) or as a mixed contamination (n = 6) with E. coli O157:H7 strains ( Figure  1). Data about the prevalence of E. coli O157:H7 and/or E. coli O55:H7 in camel meat are very limited. A study conducted on 50 camel meat samples in Iran [23] indicated that only one (2.0%) sample was contaminated with E. coli O157. Likewise, Hassan et al. [24] could not detect the enteropathogenic E. coli in any of the 15 camel meat samples examined in Qaliubiya Governorate, Egypt, although they could detect it in 13.3% (2/15), 13.3% (2/15), and 33.3% (5/15) of camel spleen, liver, and kidney samples, respectively. In the fecal sample taken from healthy camels, however, E. coli O157:H7 was isolated from 19 (19%) of 100 camels' fecal specimens collected from 100 apparently healthy camels in the middle of Iraq [25], while it was present in 3.3% from the fecal samples taken from 140 healthy camels at a slaughterhouse in the United Arab Emirates [26]. The relatively higher incidence of E. coli O157:H7 (9.1%) and E. coli O55:H7 (28.6%) among the tested camel meat samples in this study may be attributed to the cross-contamination of such organisms that normally inhabitant the gut of food animals including camels and are shed out with the animal feces, and therefore, it is very likely that E. coli can pollute the meat during the slaughtering process, especially if a faulty evisceration takes place, and also from the contaminated hide. In this context, Elder et al. [27] revealed a significant association between fecal and hide prevalence of EHEC O157 and cattle carcass contamination by such organisms. The relatively higher incidence of E. coli O157:H7 (9.1%) and E. coli O55:H7 (28.6%) among the tested camel meat samples in this study may be attributed to the cross-contamination of such organisms that normally inhabitant the gut of food animals including camels and are shed out with the animal feces, and therefore, it is very likely that E. coli can pollute the meat during the slaughtering process, especially if a faulty evisceration takes place, and also from the contaminated hide. In this context, Elder et al. [27] revealed a significant association between fecal and hide prevalence of EHEC O157 and cattle carcass contamination by such organisms.

Molecular Characterization and Virulence Genes
Distribution among E. coli O157:H7 and E. coli O55:H7 Isolated from Camel Meat Serological identification of E. coli isolates indicated that 102 isolates were serotyped as O55:H7, while only 24 isolates were serotyped as O157:H7. The twenty-four E. coli O157:H7 isolates were further confirmed by PCR as positive for the existence of the rfb O157 -specific gene, which was detected at 800 bp size (Figure 2a). Both E. coli O157:H7 and E. coli O55:H7 isolates (n = 126) were examined by multiplex PCR for the existence of eaeA, stx1, stx2, and Serological identification of E. coli isolates indicated that 102 isolates were serotyped as O55:H7, while only 24 isolates were serotyped as O157:H7. The twenty-four E. coli O157:H7 isolates were further confirmed by PCR as positive for the existence of the rfbO157 -specific gene, which was detected at 800 bp size (Figure 2a). Both E. coli O157:H7 and E. coli O55:H7 isolates (n = 126) were examined by multiplex PCR for the existence of eaeA, stx1, stx2, and EHEC-hlyA, which were identified at the expected molecular sizes of 890 bp, 614 bp, 779 bp, and 165 bp, respectively (Figure 2b).

Shiga Toxin Genes (stx1 and stx2)
Shiga toxin 2 (stx2) was the most prevalent virulence gene detected in STEC O157:H7 and O55:H7 isolated from camel meat in the current investigation, where it was identified in 97.6% (123/126) of the isolates. On the other hand, only 27.8% (35/126) of the isolates harbored stx1 (Table 1). Among the 123 stx2-positive E. coli O157:H7 and O55:H7 strains tested in the present study, 32 (25.4%) strains harbored both stx1 and stx2 genes, while 91 (72.2%) strains harbored stx2 while lacking stx1 (Table 1). It was previously pointed out that the strains harboring the stx2 gene are possibly more severe than those harboring the stx1 gene or even the strains containing both stx1 and stx2 [28,29]. Studies have revealed that stx2 is the most significant virulence element linked with severe illnesses and that stx2-carrying strains are more commonly correlated with HUS than the strains carrying stx1 [30,31]. Actually, stx2 is described to be 1000 times more cytotoxic compared to stx1 towards the micro-vascular endothelial cells of human kidneys [32].
The existence rate along with the association of stx1 and stx2 genes in STEC strains from food of animal origin varied from one study to another. Lee et al. [33], in Korea, found that 64% of the STEC strains obtained from fresh beef carried stx2, whereas 14% carried both stx1 and stx2. Beutin et al. [34], in Germany, identified stx2 in 81% and stx1 in 40% of the STEC strains recovered from fresh meat samples. Mora et al. [35], in Spain, showed that 28 (29%) of the 96 STEC isolates recovered from minced beef possessed stx1 genes, 49 (51%) carried stx2 genes, and 19 (20%) carried both stx1 and stx2. Slanec et al. [36], in another study in Germany, reported that 70.7%, 9.3%, and 20.0% of the 75 STEC strains isolated from animal origin foodstuffs carried stx2, stx1, and both stx1 and stx2, respectively. Additionally, Eid et al. [37] found that all of the three (100%) instances of E. coli O55:H7 obtained from broiler chicken in Egypt were positive for stx1, while two (66.7%) of them were positive for the stx2 gene. Contrary to our results, Rahimi et al. [23] revealed that the sole E. coli O157 isolate recovered from camel meat in Iran was lacking stx1 and stx2 virulent genes. Even if the striking findings of the virulence pattern of the isolated E. coli strains in the present study can be considered suggestive, strengthening the occurrence of positive results recorded in other surveys with different detection rates, further investigations that focus on the evidence of other virulence genes/factors (e.g., elt, est, daaD, invE, Eagg, or astA genes) and enrolling a larger number of isolates are still necessary for a comprehensive understanding of the pathogenicity of the camel meat origin E. coli strains.

Intimin (eaeA) and Enterohemolysin (hlyA) Genes
The eaeA is the gene that encodes the intimin adherence factor, which is considered an outer membrane protein necessary for the intimate attachment of E. coli to the intestinal mucosa of the host. The human pathogenic E. coli isolates are mostly positive for the eae gene. In the present study, the intimin (eaeA) gene was the second most prevalent virulence gene after stx2, where it was detected in 85.7% (108/126) of the isolates. On the other hand, 43.7% (55/126) of the isolates harbored hlyA genes ( Table 1). The eaeA gene existed in all of the 24 (100%) E. coli O157:H7 and in 84 (82.4%) of the 102 E. coli O55:H7 isolates isolated from the camel meat investigated in this study. Likewise, Sallam et al. [13], in Egypt, indicated that 93.3% (14/15) of the E. coli O157 strains recovered from beef products were positive for the eaeA gene. Similarly, Cagney et al. [38] identified the eae gene in 95.3% (41/43) of E. coli O157:H7 isolates obtained from meat products in Ireland. Moreover, Chapman et al. [39] detected the eae gene in all (100%) of the 72 E. coli O157:H7 strains recovered from raw beef and lamb products in the UK. Conversely, a low existence rate of 26% (25/96) was determined for the eae gene in STEC strains from minced beef in Spain [35], while a much lower prevalence rate of 5% was found among the isolated STEC strains recovered from samples of fresh meat harboring eaeA genes [34]. Nonetheless, Eid et al. [37] found that one (33.3%) of the three E. coli O55:H7 strains recovered from broiler chicken in Egypt was positive for the eaeA gene, while Barlow et al. [40] failed to detect the eaeA gene in the any of the meat-products-originating STEC strains (n = 184) obtained in Australia. A strong association has been clarified by several publications between the presence of the eae gene and the competency of STEC isolates to induce severe infections in humans, especially HUS and bloody diarrhea [28,41,42]. In the present study, the association of eaeA and stx2 genes was determined in all (100%) of the 24 E. coli O157:H7 and in 84 (82.4%) of the 102 E. coli O55:H7, while the association of the eaeA gene and stx1 was determined in 15 (62.5%) of the 24 E. coli O157:H7 and in 17 (16.7%) of the 102 E. coli O55:H7. Lee et al. [33] found that 7% and 14% of the STEC strains recovered from beef harbored both stx1 and eae and both stx2 and eae, respectively.
The EHEC-hlyA is another principal agent implicated in the virulence of E. coli. In the present survey, 19 (79.2%) of the 24 E. coli O157:H7 and 36 (35.3%) of the 102 E. coli O55:H7 isolates were positive for EHEC-hlyA gene, with a general prevalence of 43.7% (55/126) among the 126 STEC isolates tested (Table 1). EHEC-hlyA gene was detected at a higher prevalence rate of 93.3% (14/15) among the isolated E. coli O157 strains from beef products in Egypt [13]. A study conducted on beef and mutton meat in Hamedan, Iran, indicated that the single E. coli O157:H7 isolate as well as the nine (9/57; 15.8%) non-O157:H7 isolated strains were positive for the hlyA gene [43]. A lower detection rate of 25% (2/8) was also detected for the hlyA gene among the STEC strains obtained from cattle meat in Iran [16]. Similarly, a lower positive rate of 18.2% (2/11) for hlyA was determined in E. coli O55:H7 isolated from different meat products in Saudi Arabia [14]. Contrary to our findings, Rahimi et al. [23] revealed that the sole E. coli O157 isolate from camel meat in Iran was deficient in eaeA and ehlyA virulent genes. In the same country, the markedly genetic resistance of the human-originating E. coli strains was recently demonstrated in a study conducted by Jomehzadeh et al. [44].
The most frequent profile of the virulence gene detected in E. coli isolates from camel meat was stx2 and eaeA. Therefore, our isolated strains should be considered pathogenic for humans since the capability of STEC to induce severe illness and their potential to cause outbreaks of infection are associated with stx2-positive strains. Antimicrobial-resistant bacteria are considered a serious problem that has received significant attention worldwide due to their ability to obstruct the treatment of severe infections in human patients [45]. In the present study, all (100%) of the obtained E. coli O157:H7 and E. coli O55:H7 isolates displayed absolute resistance to at least three antibiotics from different classes, namely clindamycin (lincomycins class), penicillin (penicillins class), and erythromycin (macrolydes class) ( Table 2), which are commonly used in the veterinary medicine. Furthermore, very high resistance rates of 92.9%, 71.4%, and 48.4% was observed regarding tetracycline, ampicillin, and sulfamethoxazole-trimethoprim, respectively (Table 2). Tetracyclines and beta-lactam antibiotics such as ampicillin are still frequently used, especially in livestock treatment in Egypt [46]. The recorded high resistance towards tetracycline, ampicillin, and sulfamethoxazole-trimethoprim in this survey was consistent with previous studies on E. coli strains isolated from beef in Egypt [47,48]. Furthermore, the aminoglycosides, including amikacin and gentamicin, are extensively used in animal husbandry as broad-spectrum antibiotics and as growth promoters. The recovered E. coli O157:H7 and E. coli O55:H7 isolates displayed a resistance rate of 39.7% and 16.7% towards amikacin and gentamicin, respectively (Table 2). In a previous study in Ethiopia, 100% of E. coli O157:H7 isolated from raw cattle meat were susceptible to amikacin and gentamicin [49].
Third-generation cephalosporin antibiotics such as cefotaxime and ceftriaxone have been widely used in the management of infections caused by Gram-negative bacteria [50]. In the present study, 84.9%, 29.4%, and 3.97% of the identified E. coli O157:H7 and E. coli O55:H7 isolates were resistant to cephalothin (first-generation cephalosporin), cefotaxime, and ceftriaxone (Table 2), respectively. On the contrary, all E. coli O157:H7 isolates from cattle in Tunisia were sensitive to cefotaxime [51]. Our results are in line with those reported in a previous study conducted in Italy by Grispoldi et al. [52], who found that 89.7% of E. coli from bovine lymph nodes were resistant to cephalothin, which is recognized as an effective antimicrobial against Gram-negative as well as Gram-positive bacteria. Furthermore, a relatively lower resistance rate of 57% was observed in E. coli serovars isolated from bovine origin meat samples (four cows and three buffaloes) in Egypt against cephalothin [53]. Interestingly, despite the two third-generation cephalosporins, namely ceftriaxone and cefotaxime, being similar in their antibacterial spectrum, indications, and route of administration, the isolates examined showed a resistance rate of 29.4% against cefotaxime and a resistance rate of only 3.97% against ceftriaxone (Table 2), which may be attributed to the difference in the administration dose and elimination half-life between the two antibiotics (ceftriaxone: 2 g once a day with half-life elimination of 8.8 h versus cefotaxime: 2 g every 4 h, 1.2 h) [54,55]. Likewise, Gums et al. [56] revealed that the nonmeningeal Streptococcus pneumoniae isolates were more susceptible to ceftriaxone than to cefotaxime. The higher resistance rate of the identified E. coli O157:H7 and E. coli O55:H7 isolates in the present study against cefotaxime constitutes a potential threat for public health and indicates the crucial requirement for the cautious administration of antibiotics in the veterinary medicine.
Fluoroquinolones are extensively used against a wide variety of Gram-positive and Gram-negative bacteria. In this study, the identified E. coli O157:H7 and E. coli O55:H7 isolates (n = 126) revealed high resistance rates of 22.2% and 8.7% toward ciprofloxacin (second-generation quinolone) and levofloxacin (third-generation quinolone), respectively ( Table 2), which is in agreement with the resistance rates found in a previous study conducted in Saudi Arabia by El-Ghareeb et al. [57], who found 17.6% of E. coli isolates obtained from minced camel meat were resistant to ciprofloxacin. In contrast, Sabala et al. [46], in Egypt, found that all of the E. coli isolates (n = 150) from raw beef samples were susceptible to ciprofloxacin. The resistance rates of the identified E. coli O157:H7 and E. coli O55:H7 isolates (n = 126) against imipenem, which is recognized as a first-line drug in the treatment of human infections, were 5.56%. Conversely, none of the examined E. coli isolates (n = 150) from raw beef samples were resistant to carbapenem antimicrobials (imipenem and meropenem) [46].
Interestingly, 16.7% (4/24) and 83.3% (20/24) of the identified E. coli O157 isolates in the present study were categorized, based on their resistance profiles against the 14 different antimicrobials tested, into extensively drug-resistant (XDR) and multi-drug resistant (MDR), respectively, with a mean MAR index of 0.497 (Table 3), while 4.9%, 18.6%, and 76.5% of the identified E. coli O55:H7 isolates (n = 102) were categorized, according to their resistance profiles toward the 14 different antibiotics examined, into pan-drug resistant (PDR), extensively drug-resistant (XDR), and multi-drug resistant (MDR), respectively, with a mean MAR index of 0.527 (Table 3). Surprisingly, 3.97% (5/126) of E. coli isolates (all belong to E. coli O55:H7 serovars) exhibited resistance towards all of the 14 tested antibiotics, with a MAR index equal to 1.0 (Table 3). This finding could constitute a potential threat to public health. The average MAR index for E. coli O157:H7 and O55:H7 isolates in the present study was 0.514 (Table 3). E. coli isolates with a MAR index of >0.2 indicate a misuse and overuse of antibiotics, while E. coli isolates with a MAR index of 0.4 and above indicate human fecal contamination [58]. Therefore, it is crucial to establish monitoring systems that impose a rational usage of antibiotics in veterinary medicine for protecting public health from the spreading of multidrug-resistant bacteria to humans via animal-origin foodstuffs.  Altogether, the recorded overall antimicrobial resistance pattern of the isolated camelmeat-originating pathogenic E. coli strains can be considered worrisome in the present study, which largely agrees with results of other studies carried out in other regions of the world. These results strengthen the fact that the antimicrobial resistance phenomenon has become a significant threat to human and veterinary medicine. However, the recorded differences in terms of susceptibility towards the tested antimicrobials can be markedly influenced by the number of enrolled samples, study design, the used testing methodologies, and guidelines in interpreting the results, etc. Furthermore, supplementary studies focusing on continuous monitoring for the presence of pathogenic E. coli strains in camel meat combined with the testing of their resistance towards a wider variety of antimicrobials are still recommended.

Conclusions
The results of the present survey highlighted that the camel meat marketed in Beheira Governorate, Egypt, is contaminated with multi-and extensively drug-resistant Shiga toxigenic Escherichia coli (STEC) O157:H7 and O55:H7 strains, with an average MAR index for the isolates of 0.497 and 0.527, respectively, which emphasizes the necessity to optimize the use of the antibiotics in human and veterinary medicine. However, for a better understanding of the antimicrobial resistance phenomenon, in the case of the camel-meat-originating E. coli pathogenic strains, further investigations based on the screening of the antimicrobial resistance genes in a larger number of samples are still required. The study also elucidated that the most frequent profile of the virulence gene detected in E. coli O157:H7 and O55:H7 isolates from camel meat included stx2 and eaeA, indicating that the isolated strains have the potential to cause severe infection in humans.

Data Availability Statement:
The data presented in this study are available on request from the corresponding author.