Phenotypic Characteristics and Genetic Diversity of Salmonella enterica Serotype Derby Isolated from Human Patients and Foods of Animal Origin

Survival of Twelve Pathogenic and Generic Escherichia coli Strains in Agricultural Soils as Influenced by Strain, Soil Type, Irrigation Regimen, and Soil Amendment

Biological soil amendments of animal origin (BSAAO) play an important role in agriculture but can introduce pathogens into soils. Pathogen survival in soil is widely studied, but data are needed on the impacts of strain variability and field management practices. This study monitored the population of 12 Escherichia coli strains (generic, O157, and non-O157) in soils while evaluating the interactions of soil type, irrigation regimen, and soil amendment in three independent, greenhouse-based, randomized complete block design trials. Each E. coli strain (4-5 log10 CFU/g) was homogenized in bovine manure amended or nonamended sandy-loam or clay-loam soil. E. coli was enumerated in 25 g samples on 0, 0.167 (4 h), 1, 2, 4, 7, 10, 14, 21, 28, 56, 84, 112, 168, 210, 252, and 336 days postinoculation (dpi). Regression analyses were developed to understand the impact of strain, soil type, irrigation regimen, and soil amendment on inactivation rates. E. coli survived for 112 to 336 dpi depending on the treatment combination. Pathogenic and generic E. coli survived 46 days [95% Confidence interval (CI) = 20.85, 64.72; p = 0.001] longer in soils irrigated weekly compared to daily and 146 days (CI = 114.50, 184.50; p < 0.001) longer in amended soils compared to unamended soils. Pathogenic E. coli strains were nondetectable 69 days (CI = 39.58, 98.66, p = 0.015) earlier than generic E. coli strains. E. coli inactivation rates demonstrated a tri-phasic pattern, with breakpoints at 26 dpi (CI = 22.3, 29.2) and 130 dpi (CI = 121.0, 138.1). The study findings demonstrate that using bovine manure as BSAAO in soil enhances E. coli survival, regardless of strain, and adequate food safety practices are needed to reduce the risk of crop contamination. The findings of this study contribute data on E. coli concentrations in amended soils to assist stakeholders and regulators in making risk-based decisions on time intervals between the application of BSAAO and the production and harvest of fruits and vegetables.

Genomic Characterization of Salmonella enterica serovar Weltevreden Associated with Human Diarrhea

Salmonella Weltevreden is an emerging pathogen associated with human diarrhea, and knowledge of the genomics and epidemiology of this serovar is still limited. In this study, we performed whole-genome sequencing of 96 S. Weltevreden isolates recovered from diarrheal patients and 62 isolates from food animals in China between 2006 and 2017. Together, with an additional 199 genome sequences of S. Weltevreden published in NCBI, we performed an analysis on all 357 S. Weltevreden genome sequences. Our results demonstrated that the majority of S. Weltevreden from diarrheal patients from China (97.92%, 94/96) and the other regions in the world (94.97%, 189/199) identified in this study were sequence type (ST) 365. The remaining types were ST3771 (n = 3), ST22 (n = 1), ST155 (n = 1), and ST684 (n = 1). In addition, ST365 was also widely recovered from animals, food, and environmental samples in different regions of the world. Phylogenetic analysis and pulsed-field gel electrophoresis (PFGE) revealed that S. Weltevreden from diarrheal patients was closely related to those recovered from food and environmental specimens. We also showed that S. Weltevreden did not exhibit severe antimicrobial resistance profiles, suggesting administering antibiotics is still effective for controlling the agent. Interestingly, we found that S. Weltevreden strains carried a number of virulence factor genes, and a 100.03-kb IncFII(S) type plasmid was widely distributed in S. Weltevreden strains. Elimination of this plasmid decreased the bacterial capacity to infect both Caco-2 cells and C57BL/6 mice, suggesting the importance of this plasmid for bacterial virulence. Our results contribute to the understanding of the epidemiology and virulence of S. Weltevreden. IMPORTANCE Salmonella Weltevreden is a pathogen associated with human diarrheal diseases found across the globe. However, knowledge of the genomics and epidemiology of this pathogen is still limited. In this study, we found S. Weltevreden sequence type (ST) 365 is commonly recovered from diarrheal patients in China and many other regions of the world, and there is no major difference between the Chinese isolates and the global isolates at the phylogenetic level. We also demonstrated that ST365 was widely recovered from animal, food, and environmental samples collected in different, global regions. Importantly, we discovered an IncFII(S) type plasmid commonly carried by S. Weltevreden strains of human, animal, and food origins, and this plasmid is likely to contribute to the bacterial pathogenesis. These findings enhance our understanding of the emergence of S. Weltevreden involved in diarrheal outbreaks and the global spread of S. Weltevreden strains.

Prevalence, Characterization, and Pathogenicity of Salmonella enterica Subspecies enterica Serovar Derby from Yaks in the Aba Tibetan Autonomous Prefecture, China

Simple Summary

Salmonella spp. is a very important pathogen in the livestock industry and public health, which poses a major threat to global public health. Yaks and their by-products have a significant economic status in the Qinghai–Tibetan Plateau. The aim of this study was to investigate the prevalence of salmonella in yak farms and to conduct a molecular characterization and tests on its pathogenicity in mice with the use of salmonella isolated from yaks with diarrhea as well as from drinking water samples. The prevalence of salmonella was 19.75% of 162 samples collected from yak farms, and all isolates were found to belong to the serovar of Salmonella Derby and ST40. All Salmonella Derby isolates from both fecal and drinking water samples from 13 farms were clonally related based on SNP alignment. Salmonella Derby was still detected positively in the feces of model mice on day 24 post-injection. This study reports the prevalence of Salmonella Derby in yaks with diarrhea and in their drinking water. In addition, the pathogenicity of the S. Derby in mice was investigated. Findings suggest that Salmonella Derby excreted by diarrheic yaks is a source of contamination for other yaks and the environment and is highly pathogenic to mice. Seeing that Salmonella Derby has become one of the most common Salmonella serovars, this situation gives rise to further risk from the potential spread of food-borne diseases.

Abstract

Salmonella enterica subsp. enterica serovar Derby (S. Derby) is one of the numerous non-typhoidal Salmonella serovars and has been recognized as a food-borne pathogen. In 2019, outbreaks of salmonellosis were reported in 13 yak farms in the Aba Tibetan Autonomous Prefecture, China. A total of 32 salmonella strains were isolated from 162 fecal samples of yaks with diarrhea as well as from drinking water samples. The isolates were subjected to serovar identification, animal experiments, and whole-genome sequencing (WGS) analyses. The serovar of all the isolates was S. Derby, and the sequence types (STs) were ST40. The analysis of the differences of single-nucleotide polymorphisms (SNPs) showed that the salmonella strains isolated from 13 farms were clonally related. Animal experiments showed that the lethal dose (LD₅₀) was 4.57 × 10⁷ CFU (colony-forming units); the shedding time of S. Derby in mice was 24 days; the bacterial loads in spleen were higher than those in other organs (ileum, liver, and cecum). Pathological analyses by hematoxylin and eosin (H&E) staining revealed obvious damage in the spleen, liver, and intestine. These results indicate that the S. Derby from yaks can cause infection in mice.

Characterization of Salmonella serotypes prevalent in asymptomatic people and patients

Background

Infection with Salmonella enterica usually results in diarrhea, fever, and abdominal cramps, but some people become asymptomatic or chronic carrier as a source of infection for others. This study aimed to analyze the difference in serotype, antimicrobial resistance, and genetic profiles between Salmonella strains isolated from patients and those from asymptomatic people in Nantong city, China.

Methods

A total of 88 Salmonella strains were collected from patients and asymptomatic people from 2017 to 2018. Serotyping, antimicrobial susceptibility testing, and PFGE analysis were performed to analyze the characteristics of these strains.

Results

Twenty serotypes belonging to 8 serogroups were identified in the 88 Salmonella strains. S. Typhimurium remained to be the predominant serotype in strains from both patients and asymptomatic people. Among the 27 strains from patients, S. Enteritidis and S. Rissen were shown as the other two major serotypes, while S. London, S. Derby, and S. Meleagridis were demonstrated as the other significant serotypes among the 61 strains from asymptomatic people. Antimicrobial resistance testing revealed that 84.1% of strains from both resources were multi-drug resistant. PFGE displayed a highly discriminative ability to differentiate strains belonging to S. Derby, S. Typhimurium, etc., but could not efficiently differentiate serotypes like S. Enteritidis.

Conclusions

This study’s results demonstrated that S. Typhimurium could cause human infection in both symptomatic and asymptomatic state; S. London, S. Derby, and S. Meleagridis usually cause asymptomatic infection, while S. Enteritidis infection mainly results in human diseases. The high multi-drug resistance rate detected in the antimicrobial resistance and diverse PFGE profiles of these strains implied that the strains were isolated from different sources, and the increased surveillance of Salmonella from both patients and asymptomatic people should be taken to control the disease.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06340-z.

Molecular Typing of Salmonella by Pulsed-Field Gel Electrophoresis

Salmonella is recognized as a major human foodborne pathogen and threat to public health world widely. It is important to carry out epidemiological investigations to determine the primary sources of bacterial contamination. Pulsed-field gel electrophoresis (PFGE) is an important method of the molecular typing, and play an important role in tracking the sources of infection and epidemic control. The PFGE is currently considered as "gold standard" of molecular typing methods for bacterial foodborne pathogen. Here, we describe the PFGE protocol to type the Salmonella from pork.

Identification of Novel Sensitive and Reliable Serovar-Specific Targets for PCR Detection of Salmonella Serovars Hadar and Albany by Pan-Genome Analysis

The accurate and rapid classification of Salmonella serovars is an essential focus for the identification of isolates involved in disease in humans and animals. The purpose of current research was to identify novel sensitive and reliable serovar-specific targets and to develop PCR method for Salmonella C2 serogroups (O:8 epitopes) in food samples to facilitate timely treatment. A total of 575 genomic sequences of 16 target serovars belonging to serogroup C2 and 150 genomic sequences of non-target serovars were analysed by pan-genome analysis. As a result, four and three specific genes were found for serovars Albany and Hadar, respectively. Primer sets for PCR targeting these serovar-specific genes were designed and evaluated based on their specificity; the results showed high specificity (100%). The sensitivity of the specific PCR was 2.8 × 10¹–10³ CFU/mL and 2.3 × 10³–10⁴ CFU/mL for serovars Albany and Hadar, respectively, and the detection limits were 1.04 × 10³–10⁴ CFU/g and 1.16 × 10⁴–10⁵ CFU/g in artificially contaminated raw pork samples. Furthermore, the potential functions of these serovar-specific genes were analysed; all of the genes were functionally unknown, except for one specific serovar Albany gene known to be a encoded secreted protein and one specific gene for serovars Hadar and Albany that is a encoded membrane protein. Thus, these findings demonstrate that pan-genome analysis is a precious method for mining new high-quality serovar-targets for PCR assays or other molecular methods that are highly sensitive and can be used for rapid detection of Salmonella serovars.

Characterization of Salmonella Resistome and Plasmidome in Pork Production System in Jiangsu, China

The prevalence of antimicrobial resistance in zoonotic Salmonella is a significant ongoing concern over the world. Several reports have investigated the prevalence of Salmonella infections in the farm animals in China; however, there is only limited knowledge about the Salmonella cross-contamination in the slaughterhouses. Moreover, the application of genomic approaches for understanding the cross-contamination in the food-animal slaughterhouses is still in its infancy in China. In the present study, we have isolated 105 Salmonella strains from pig carcasses and environment samples collected from four independent slaughterhouses in Jiangsu, China. All the Salmonella isolates were subjected to whole genome sequencing, bioinformatics analysis for serovar predictions, multi-locus sequence types, antimicrobial resistance genes, and plasmid types by using the in-house Galaxy platform. The antimicrobial resistance of Salmonella isolates was determined using a minimal inhibitory concentration assay with 14 antimicrobials. We found that the predominant serovar and serogroup was S. Derby and O:4(B), with a prevalence of 41.9 and 55%, respectively. All the isolates were multidrug-resistant and the highest resistance was observed against antimicrobials tetracycline (95.4%) and trimethoprim and sulfamethoxazole (90.9%). Additionally, the colistin-resistant determinant mcr-1 gene was detected in five (4.8%) strains. Our study demonstrated the prevalence of antimicrobial resistance in Salmonella strains isolated from pig slaughterhouses in China and suggested that the genomic platform can serve as routine surveillance along with the food-chain investigation.

Antimicrobial resistance and molecular characterization of Salmonella enterica serovar Corvallis isolated from human patients and animal source foods in China

In this study, 205 Salmonella enterica serovar Corvallis strains were obtained from humans and foods from Guangdong, Guangxi, and Shanghai in China from 2009 to 2017 to assess drug resistance and molecular epidemiology. These isolates displayed high rates of resistance to sulfisoxazole (94.15%) and tetracycline (77.56%). Surprisingly, the rate of resistance to ciprofloxacin reached 21.46%. Moreover, 63.9% of the strains displayed multidrug resistance. Detection of quinolone genes showed that 97.56% of the strains had single mutations (T57S) in parC. The plasmid-mediated quinolone resistance (PMQR) genes qnrS, aac(6')-Ib-cr, and qnrB, were also detected. The extended spectrum β-lactamase (ESBLS) gene that was most common among the isolates was bla_TEM-1 (18.05%). These S. Corvallis isolates are the first to date, that have been reported to possess bla_CTX-M-55 or bla_NDM-5. Additionally, 95.61% of isolates were biofilm producers. The streptomycin resistance rate was higher in strong biofilm producers (87.50%) than in moderate (37.93%) and weak (26.49%) biofilm producers. Pulsed-field gel electrophoresis (PFGE) showed that some strains from different sources had the same genotype. These isolates may be transmitted to humans through food and therefore the monitoring of these isolates should be strengthened in China.

Antibiotic Resistance Profiles of Salmonella Recovered From Finishing Pigs and Slaughter Facilities in Henan, China

With the increase in commercial pig farming, there is a simultaneous increase in the use of antibiotics for prophylaxis as well as therapeutics in China. In this study, we evaluated the prevalence and resistance diversity of salmonellae isolated from feces of asymptomatic, live and slaughtered pigs. We analyzed 1,732 pig fecal samples collected over 8 months, at Henan province of China. The salmonellae were isolated and identified by PCR. They were serotyped using commercial antisera and assayed for the MIC of 16 antibiotics by broth microdilution method. The average prevalence of Salmonella was 19.4% (95% CI: 17.6–21.4). Large farms (herd size ≥1,000) were found to have a higher prevalence as compared to the small- and medium-scale farms (p < 0.0001). The prevalence of salmonellae in samples collected from the farms [11.77% (95% CI: 10.1–13.6)] and from the slaughterhouse [45.23% (95% CI: 40.3–50.30)] was statistically different (p < 0.0001). Uncommon serovars of Salmonella such as Agama and common serovars such as Derby and Typhimurium were isolated. High resistance (>80%) was recorded toward ciprofloxacin (100%), tetracycline (99.4%), doxycycline (97%), sulfamethoxazole (85.8%), ampicillin (81.6%), and amoxicillin (80.4%). Multidrug resistance (MDR) to four, five, and seven classes of antibiotics was recorded to be approximately 25% in the most prevalent serovar like Derby. We conclude that the presence of alarmingly high resistance, toward the critical antibiotics such as fluoroquinolones and beta-lactams, in large swine farms in China, should draw public attention. These results highlight the need for continued antibiotic stewardship programs for judicious use of critical antibiotics in animal health as well as for producing safe pork.

Characterization of ciprofloxacin-resistant and ESBL-producing Salmonella enteric serotype Derby in Eastern China

Background

Fluoroquinolone resistance and ESBL-production are concurrently found in a limited number of Salmonella serotypes. The present study was aimed to characterize fluoroquinolone-resistant and ESBL-producing Salmonella enteric serotype Derby (S. Derby) isolates in terms of antimicrobial susceptibility, relevant genetic mechanisms, and PFGE.

Results

From 2013 to 2017 in Ningbo China, 52 S. Derby isolates were identified out of 826 non-typhoidal Salmonella isolates from patient feces, food, and environmental water samples. Three S. derby isolates were identified to be fluoroquinolone-resistant and ESBL-producing with cefotaxime MIC of 64 μg/mL and ciprofloxacin MIC of 4 μg/mL. The three isolates contained the same genetic structure of quinolone resistance, including a silent gyrA mutation S (TCC) 83S (TCT) and three PMQR genes qnrB, qnrS and aac(6′)-Ib-cr. As withβ-lactams resistance mechanisms, two isolates contained bla_TEM, bla_OXA, and bla_CTX-M genes and one isolate contained bla_OXA and bla_CTX-M genes. Additionally, two isolates displayed more identical PFGE pattern than the third isolate, whereas three isolates showed the same plasmid profile of I1, W and P by PCR-based replicon typing. The conjugation experiment showed no dissemination of β-lactam resistance by direct contact among isolates; the transformation experiment failed to transfer plasmid conferring ampicillin resistance to E. coli DH5a.

Conclusion

The present study demonstrates the emerging fluoroquinolone-resistant and ESBL-producing S. Derby in both humans and the environment. Seeing that S. Derby has become one of the most common Salmonella serotypes, this situation gives rise to a new major risk of food-borne diseases.

Experimental infection of pigs by Salmonella Derby, S. Typhimurium and monophasic variant of S. Typhimurium: Comparison of colonization and serology

Salmonella serovars Derby, Typhimurium and the monophasic variant of Salmonella Typhimurium are the most frequently isolated serovars in pigs in France. To compare the excretion patterns, seroconversion to Salmonella and contamination of the organs of pigs inoculated with strains of all three serovars, we conducted an experimental trial with 28 SPF piglets. Four were used as a negative control, while the other 24 were divided equally into three groups. Each group was inoculated at 7 weeks of age with a different strain: S. Derby (SDb), S. Typhimurium (ST), and the monophasic variant of S. Typhimurium (mST). Fecal and blood samples were collected twice a week up until necropsy, on 21 days post-inoculation (DPI) for half of each group and 49 DPI for the remaining piglets. During necropsy, the tonsils, mesenteric lymph nodes and various intestinal contents were collected from each pig. Salmonella bacteria were quantified in CFU/g by a bacteriological method, and levels of Salmonella antibodies were measured using an ELISA Kit. Piglets inoculated with mST continuously excreted Salmonella in their feces throughout the trial. For each of the other serovars, one piglet was Salmonella-negative on one DPI. The quantity of Salmonella excreted was statistically different between the group inoculated with ST and mST (p < 0.05), but no differences were found between the other serovars. The tonsils, cecum and jejunum were the most contaminated organs in all groups. Seroconversion for all the piglets was completed by different DPI: 28 for ST, 31 for mST and 38 for SDb. No major differences were found in terms of excretion and colonization among the studied serovars.

Salmonella control in poultry flocks and its public health impact

An increase in confirmed human salmonellosis cases in the EU after 2014 triggered investigation of contributory factors and control options in poultry production. Reconsideration of the five current target serovars for breeding hens showed that there is justification for retaining Salmonella Enteritidis, Salmonella Typhimurium (including monophasic variants) and Salmonella Infantis, while Salmonella Virchow and Salmonella Hadar could be replaced by Salmonella Kentucky and either Salmonella Heidelberg, Salmonella Thompson or a variable serovar in national prevalence targets. However, a target that incorporates all serovars is expected to be more effective as the most relevant serovars in breeding flocks vary between Member State (MS) and over time. Achievement of a 1% target for the current target serovars in laying hen flocks is estimated to be reduced by 254,400 CrI95[98,540; 602,700] compared to the situation in 2016. This translates to a reduction of 53.4% CrI95[39.1; 65.7] considering the layer-associated human salmonellosis true cases and 6.2% considering the overall human salmonellosis true cases in the 23 MSs included in attribution modelling. A review of risk factors for Salmonella in laying hens revealed that overall evidence points to a lower occurrence in non-cage compared to cage systems. A conclusion on the effect of outdoor access or impact of the shift from conventional to enriched cages could not be reached. A similar review for broiler chickens concluded that the evidence that outdoor access affects the occurrence of Salmonella is inconclusive. There is conclusive evidence that an increased stocking density, larger farms and stress result in increased occurrence, persistence and spread of Salmonella in laying hen flocks. Based on scientific evidence, an impact of Salmonella control programmes, apart from general hygiene procedures, on the prevalence of Campylobacter in broiler flocks at the holding and on broiler meat at the end of the slaughter process is not expected.

Non-typhoidal Salmonella in the Pig Production Chain: A Comprehensive Analysis of Its Impact on Human Health

Salmonellosis remains one of the most frequent foodborne zoonosis, constituting a worldwide major public health concern. The most frequent sources of human infections are food products of animal origin, being pork meat one of the most relevant. Currently, particular pig food production well-adapted and persistent Salmonella enterica serotypes (e.g., Salmonella Typhimurium, Salmonella 1,4,[5],12:i:-, Salmonella Derby and Salmonella Rissen) are frequently reported associated with human infections in diverse industrialized countries. The dissemination of those clinically-relevant Salmonella serotypes/clones has been related to the intensification of pig production chain and to an increase in the international trade of pigs and pork meat. Those changes that occurred over the years along the food chain may act as food chain drivers leading to new problems and challenges, compromising the successful control of Salmonella. Among those, the emergence of antibiotic resistance in non-typhoidal Salmonella associated with antimicrobials use in the pig production chain is of special concern for public health. The transmission of pig-related multidrug-resistant Salmonella serotypes, clones and/or genetic elements carrying clinically-relevant antibiotic resistance genes, frequently associated with metal tolerance genes, from pigs and pork meat to humans, has been reported and highlights the contribution of different drivers to the antibiotic resistance burden. Gathered data strengthen the need for global mandatory interventions and strategies for effective Salmonella control and surveillance across the pig production chain. The purpose of this review was to provide an overview of the role of pig and pork meat in human salmonellosis at a global scale, highlighting the main factors contributing to the persistence and dissemination of clinically-relevant pig-related Salmonella serotypes and clones.

Prevalence, Serotypes, and Antimicrobial Resistance Profiles Among Salmonella Isolated from Food Catering Workers in Nantong, China

Salmonella is a worldwide foodborne pathogen causing human disease. Food handlers, who are potential carriers of Salmonella, may transmit the pathogen to consumers through food. To determine the prevalence of Salmonella enterica serovars among food handlers working in the catering industry in Nantong, China, a total of 214,542 food handlers' fecal samples were tested for Salmonella in the Nantong CDC (Centers for Disease Control) from 2012 to 2017. Among those tested, 193 (0.09%) were identified to be positive for Salmonella, and the highest detection rate was 0.16% during the period of July to September. Serotyping analysis showed that Salmonella enterica serovar Typhimurium was the predominant serotype (16.1%), followed by Salmonella Derby (13.5%), Salmonella Enteritidis (11.4%), and Salmonella London (11.4%). The high detection rate of Salmonella Derby was probably closely related to its high prevalence of the serotype in pork, which is the primary meat consumed by the Chinese. Antibiotic susceptibility analysis demonstrated that 73.4% of the isolates were multidrug-resistant (MDR) strains with predominant resistance to ampicillin (AMP, 64.6%), followed by resistance to sulfisoxazole (SUL, 58.1%), nalidixic acid (55.8%), and tetracycline (TET, 44.5%). Therefore, MDR Salmonella strain carriage among food handlers working in the catering industry might be a potential source of human salmonellosis, especially for the predominant MDR genotype isolates (32.3%) with resistance to AMP, SUL, and TET.

High-levels of resistance to quinolone and cephalosporin antibiotics in MDR-ACSSuT Salmonella enterica serovar Enteritidis mainly isolated from patients and foods in Shanghai, China

In this study, 2887 Salmonella strains were mainly obtained from patients and foods in Shanghai from 2006 to 2014 in order to assess the susceptibility to 16 antibiotics. Among them, 3.8% (110/2887) S. Enteritidis isolates were shown to have an ACSSuT (ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, and tetracycline) resistance pattern. The resistance genes of ACSSuT included sul2 (74.55%), flo (67.27%), tetA (49.09%), and aph(3)-IIa (46.36%). In addition, class 1 integron profiles were detected in 9 isolates, and 55.6% (5/9) were shown to carry resistant genes against aminoglycosides and sulfonamides. Moreover, these isolates had a high rate of resistance to nalidixic acid (95.29%), cefotaxime (70.64%), cefepime (58.72%), and ceftazidime (48.62%). Detection of quinolone genes showed that 93.64% (103/110) of the strains had gyrA single mutations (D87G, D87Y, D87N, S83Y, and S83F), where D87G was the dominant mutation in 55.45% isolates. 19.1% (21/110) isolates carried plasmid-mediated quinolone resistance (PMQR) genes (qnrB and aac(6')-Ib-cr), and the most prevalent was qnrB. Furthermore, we also detected ESBLS genes. The most common were bla_CTX-M-55 (57.27%) followed by bla_TEM (23.6%) and bla_OXY (4.55%). Mart, prot6E, steB, fimA, and sopE2 genes (100%) were the most in these isolates. The strains in the dominant PFGE profiles of G1 were all co-resistant to quinolones, cephalosporins, and ACSSuT, and were isolated from different sources. This suggests that existence of these genes lead to the emergence of high-levels of resistance to quinolone and cephalosporin in these ACSSuT resistance pattern isolates. And these isolates are transmitted between humans and food.