Characteristics of Integrons and Associated Gene Cassettes in Antibiotic-Resistant Escherichia coli Isolated from Free-Ranging Food Animals in China

Characterization of antibiotic resistance genes and mobile genetic elements in Escherichia coli isolated from captive black bears

The objective of this study was to analyze the antimicrobial resistance (AMR) characteristics produced by antibiotic resistance genes (ARGs), mobile genetic elements (MGEs) and gene cassettes in Escherichia coli isolated from the feces of captive black bears. Antimicrobial susceptibility testing was performed by using the disk diffusion method, and both MGEs and integron gene cassettes were detected by polymerase chain reaction. Our results showed that 43.7% (62/142) of the isolates were multidrug resistant strains and 97.9% (139/142) of the isolates were resistant to at least one antibiotic. The highest AMR phenotype was observed for tetracycline (79.6%, 113/142), followed by ampicillin (50.0%, 71/142), trimethoprim-sulfamethoxazole (43.7%, 62/142) and cefotaxime (35.9%, 51/142). However, all isolates were susceptible to tobramycin. tetA had the highest occurrence in 6 ARGs in 142 E. coli isolates (76.8%, 109/142). Ten mobile genetic elements were observed and IS26 was dominant (88.0%, 125/142). ISECP1 was positively associated with five β-lactam antibiotics. ISCR3/14, IS1133 and intI3 were not detected. Seventy-five E. coli isolates (65 intI1-positive isolates, 2 intI2-positive isolates and 8 intI1 + intI2-positive isolates) carried integrons. Five gene cassettes (dfrA1, aadA2, dfrA17-aadA5, aadA2-dfrA12 and dfrA1-aadA1) were identified in the intI1-positive isolates and 2 gene cassettes (dfrA1-catB2-sat2-aadA1 and dfrA1-catB2-sat1-aadA1) were observed in the intI2-positive isolates. Monitoring of ARGs, MGEs and gene cassettes is important to understand the prevalence of AMR, which may help to introduce measures to prevent and control of AMR in E. coli for captive black bears.

Determining the prevalence and genetic diversity of plasmid-mediated sulfonamide resistance in Escherichia coli from commercial broiler samples

Sulfonamides are commonly used antibacterials in commercial poultry, contributing toward the development of multidrug-resistant (MDR) phenotypes among Escherichia coli and that has emerged as global concern. The current study aimed to assess the sulfonamide resistance among isolated E. coli strains among commercial broilers. The bacterial strains were identified from fecal samples (n = 100) using selective media, followed by initial identification based on biochemical profiles. The susceptibility was determined by measuring the minimum inhibitory concentration (MIC) against sulfamethoxazole. The study also evaluated mobile genetic elements (MGEs), the mediators of antibiotic resistance, by amplification of plasmid DNA using specific primer PCR. Additionally, the isolates were subjected to multilocus sequence typing (MLST) analysis to investigate the genetic diversity among E. coli carrying sulfonamide resistance genes. The results revealed that 58% (58/100) E. coli strains were resistant to sulfonamides, with 36.20% (21/58) of the strains exhibiting an MIC breakpoint ≥512 µg/mL. PCR analysis showed that 42.85% (9/21) of the strains harbored the sul-1 gene, while 38.09% (8/21) carried the sul-2 gene, and 19.04% (4/21) had both genes. No isolate showed the presence of the sul-3 gene. Furthermore, class 1 and class 2 integrons were identified among 80.95% (17/21) and 19.04% (4/21) of the strains, respectively. MLST analysis confirmed that the strains belonged to sequence types (STs) including ST1638, ST155, ST48, ST350, ST23, ST156, and ST746. These findings underscore the diversity among E. coli strains in commercial poultry, which poses a significant risk.

Prevalence, molecular characterization of integrons and its associated gene cassettes in Klebsiella pneumoniae and K. oxytoca recovered from diverse environmental matrices

The high prevalence of infections arising from Klebsiella species is related to their ability to acquire and disseminate exogenous genes associated with mobile genetic elements such as integrons. We assessed the prevalence, diversity, and associated gene cassettes (GCs) of integrons in Klebsiella species. The isolates recovered from wastewater and hospital effluents, rivers, and animal droppings were identified using the conventional Polymerase Chain Reaction (PCR) with primers targeting the gryA, pehX, and 16S-23S genes. The antimicrobial resistance profile and the Extended-Spectrum and Metallo β-lactamases production were carried out using standard microbiological techniques. PCR, DNA sequencing analyses, and Restriction Fragment Length Polymorphism were used to characterize the integrons and their associated GCs. Furthermore, the genotypic relationships between the different isolated K. pneumoniae were determined using Enterobacterial Repetitive Intergenic Consensus (ERIC)-PCR. About 98% (51/52) of the confirmed isolates harboured an integrase gene, with 80% intI1, while the remaining 20% concurrently harboured intI1 and intI2, with no intI3 observed. About 78% (40/51) of the bacterial strains were positive for a promoter, the P2R2, investigated, while 80% (41/51) harboured at least one of the qacEΔ1 and sul1. Three different GCs arrangements identified were aac(6')-Ib, aadA1-dfrA1, and dfrA1-sat2. At a similarity index of 60%, the ERIC-PCR fingerprints generated were categorized into nine clusters. Our study is the first to reveal the features of integrons in Klebsiella spp. recovered from environmental sources in the Eastern Cape Province, South Africa. We conclude that the organisms' sources are repositories of integrons harbouring various gene cassettes, which can be readily mobilized to other microorganisms in similar or varied niches.

The sulfonamide-resistance dihydropteroate synthase gene is crucial for efficient biodegradation of sulfamethoxazole by Paenarthrobacter species

Sulfonamide antibiotics (SAs) are serious pollutants to ecosystems and environments. Previous studies showed that microbial degradation of SAs such as sulfamethoxazole (SMX) proceeds via a sad-encoded oxidative pathway, while the sulfonamide-resistant dihydropteroate synthase gene, sul, is responsible for SA resistance. However, the co-occurrence of sad and sul genes, as well as how the sul gene affects SMX degradation, was not explored. In this study, two SMX-degrading bacterial strains, SD-1 and SD-2, were cultivated from an SMX-degrading enrichment. Both strains were Paenarthrobacter species and were phylogenetically identical; however, they showed different SMX degradation activities. Specifically, strain SD-1 utilized SMX as the sole carbon and energy source for growth and was a highly efficient SMX degrader, while SD-2 did could not use SMX as a sole carbon or energy source and showed limited SMX degradation when an additional carbon source was supplied. Genome annotation, growth, enzymatic activity tests, and metabolite detection revealed that strains SD-1 and SD-2 shared a sad-encoded oxidative pathway for SMX degradation and a pathway of protocatechuate degradation. A new sulfonamide-resistant dihydropteroate synthase gene, sul918, was identified in strain SD-1, but not in SD-2. Moreover, the lack of sul918 resulted in low SMX degradation activity in strain SD-2. Genome data mining revealed the co-occurrence of sad and sul genes in efficient SMX-degrading Paenarthrobacter strains. We propose that the co-occurrence of sulfonamide-resistant dihydropteroate synthase and sad genes is crucial for efficient SMX biodegradation. KEY POINTS: • Two sulfamethoxazole-degrading strains with distinct degrading activity, Paenarthrobacter sp. SD-1 and Paenarthrobacter sp. SD-2, were isolated and identified. • Strains SD-1 and SD-2 shared a sad-encoded oxidative pathway for SMX degradation. • A new plasmid-borne SMX resistance gene (sul918) of strain SD-1 plays a crucial role in SMX degradation efficiency.

Characterization of piggery farm waste-borne bacterial transposable elements associated with antimicrobial resistance phenotypes

Even though there is a link between antibiotic resistance and the presence of transposable elements few research has looked at the prevalence and distribution of transposable elements/ integrons in piggery farm samples. Present study identified the presence of six transposable elements namely Tn6763 (Accession number: OQ565300), Tn6764, (Accession number: OQ565299), Tn6765 (Accession number: OQ409902), Tn2003 (Accession number: OQ503494), Tn6072 (Accession number: OQ565298) and Tn6020 (Accession number: OQ503493) in piggery farm waste from India which are belongs to Enterobacteriaceae family. In a conjugative experiment, Klebsiella isolates carrying Tn6020 having the resistant phenotypes for nalidixic acid was used as donor cells while Escherichia coli DH5α Cells carrying chloramphenicol resistant plasmid was employed as recipient cells. Transconjugant bacterial colonies were shown to carry the Tn6020 transposable elements with both nalidixic acid (donor cell origin) and chloramphenicol (recipient cell origin) resistant antibiotic phenotypes. Given the presence of transposable elements in 21.4% of resistant Enterobacteriaceae strains, preventative measures are vital for avoiding the spread of mobile genetic resistance determinants in the piggery sector and to monitor their emergence.

Effects of Two Feeding Patterns on Growth Performance, Rumen Fermentation Parameters, and Bacterial Community Composition in Yak Calves

The health of young ruminants is highly dependent on early rumen microbial colonization. In this study, the effects of milk replacer on growth performance, rumen fermentation, and the rumen microflora in yak calves were evaluated. Sixty yak calves (body weight = 22.5 ± 0.95 kg, age = 30 ± 1 d) were assigned to the CON group (breastfed) or TRT group (milk replacer fed) and evaluated over 120 d. At 120 d, ruminal fluid samples were collected from 14 calves and then conducted for rumen fermentation and microbiota analyses. There was no difference in growth performance; however, calf survival was higher in the TRT group than in the CON group. The concentration of total volatile fatty acids and the molar proportion of butyric acid and lactic acid were increased with milk replacer feed in the TRT group (p < 0.05), but iso-valeric acid concentration was highest in the CON group (p < 0.05). Firmicutes and Bacteroidetes were the most dominant phyla in the CON and TRT groups, respectively. In the TRT group, Bacteroidetes, Prevotellaceae, Bacteroidia, Bacteroidetes, and Prevotella_1 were the dominant flora in the rumen of calves. The relative abundances of various taxa were correlated with rumen fermentation parameters; the relative abundance of Quinella and iso-butyrate levels were positively correlated (r = 0.57). The relative abundances of the Christensenellaceae_R-7_group and A/P were positively correlated (r = 0.57). In summary, milk replacer is conducive to the development of the rumen microflora, the establishment of rumen fermentation function, and the implementation of early weaning in yaks.

First study on virulence genes, antimicrobial resistance, and integrons in Escherichia coli isolated from cage, free-range, and organic commercial eggs in Phayao Province, Thailand

Background and Aim:

Antimicrobial resistance (AMR) is a global problem that affects human and animal health, and eggs can act as a vehicle for pathogenic and non-pathogenic resistant bacteria in the food chain. Escherichia coli is an indicator of food contamination with fecal materials as well as the occurrence and levels of AMR. This study aimed to investigate the presence of AMR, integrons, and virulence genes in E. coli isolated from eggshell samples of three egg production systems, from supermarkets in Thailand.

Materials and Methods:

A total of 750 hen’s egg samples were purchased from supermarkets in Phayao Province: Cage eggs (250), free-range eggs (250), and organic eggs (250). Each sample was soaked in buffered peptone water (BPW), and the BPW samples were incubated at 37°C for 18–24 h. All samples were tested for E. coli by the standard conventional culture method. Then, all identified E. coli were tested for antimicrobial susceptibility to 15 antimicrobial agents by the agar disk diffusion method. All E. coli strains were subsequently found to have virulence genes and Classes 1 and 2 integrons by polymerase chain reaction.

Results:

Among the eggshell samples, 91 samples were identified as having E. coli (cage eggs, 24 strains; free-range eggs, 27 strains; and organic eggs, 40 strains). Then, among the E. coli strains, 47 (51.6%) were positive for at least one virulence gene. The proportion of AMR in the eggshell samples was 91.2% (83/91), and streptomycin (STR), ampicillin (AMP), and tetracycline (TET) had a high degree of resistance. Among the E. coli strains, 27 (29.7%) strains were positive for class 1 or 2 integrons, and integron-positive strains were commonly found in STR-, AMP-, and TET-resistant strains. Multidrug resistance (MDR) was detected in 57.1% (52/91) of the E. coli strains, with STR-AMP-TET (5.5%) as the most frequent pattern. The proportion of MDR in cage eggs was 75.0% (18/24), which was higher than in both free-range and organic eggs. On the other hand, 53.2% (25/47) of E. coli carrying virulence genes had MDR, distributed across the production systems as follows: Cage eggs, 76.9% (10/13); free-range eggs, 63.6% (7/11); and organic eggs, 34.8% (8/23).

Conclusion:

Escherichia coli was detected in eggshell samples from all three egg production systems. The high level of virulence genes, AMR, and integrons indicated the possibility of dissemination of AMR among pathogenic and commensal E. coli through eggshells. These findings could be a major concern to farmers, food handlers, and consumers, especially regarding raw egg consumption.

Descriptive Analysis of Circulating Antimicrobial Resistance Genes in Vancomycin-Resistant Enterococcus (VRE) during the COVID-19 Pandemic

COVID-19 offers ideal premises for bacteria to develop antimicrobial resistance. In this study, we evaluated the presence of several antimicrobial resistance genes (ARG) in vancomycin-resistant Enterococcus (VRE) isolated from rectal swabs from patients at a hospital in Cluj-Napoca, Romania. Rectal swabs were cultivated on CHROMID^® VRE (bioMérieux, Marcy—l’ Étoile, France) and positive isolates were identified using MALDI-TOF Mass Spectrometry (Bruker Daltonics, Bremen, Germany) and further analyzed using the PCR technique for the presence of the following ARGs: van A, van B, tet(M), tet(L), ermB, msrA, mefA, aac(6′)-Im, aph(2)-Ib, ant(4′)-Ia, sul1, sul2, sul3, and NDM1. We isolated and identified 68 isolates of Enterococcus faecium and 11 isolates of Enterococcus faecalis. The molecular analysis showed 66 isolates positive for the vanA gene and eight positive for vanB. The most frequent association of ARG in VRE was vanA-tet(M)-ermB. There was no statistically significant difference between Enterococcus faecium and Enterococcus faecalis regarding ARGs. Our work proves that during the COVID-19 pandemic, highly resistant isolates of Enterococcus were present in patients in the intensive care unit; thus, better healthcare policies should be implemented for the management and control of these highly resistant isolates in the future.

High Prevalence of Antimicrobial Resistance and Integron Gene Cassettes in Multi-Drug-Resistant Klebsiella pneumoniae Isolates From Captive Giant Pandas (Ailuropoda melanoleuca)

Multi-drug-resistant Klebsiella pneumoniae (MDR K. pneumonia) is increasingly being reported with corresponding increase in morbidity and mortality all over the world. However, limited information is available concerning MDR K. pneumonia in giant pandas. The objective of this study was to grasp the drug resistance profile of MDR K. pneumonia isolated from giant pandas. A total of 182 K. pneumoniae isolates were collected from fresh feces of 94 captive giant pandas of different ages and sex and separated by season. We performed a standard disk diffusion antimicrobial susceptibility test with the isolates and further evaluated the antibiotic resistance genes (ARGs) of multi-drug-resistant strains by high-throughput quantitative PCR. In addition, we then analyzed mobile genetic elements (MGEs), integron gene cassettes, and the multi-locus sequence typing of multi-drug-resistant strains by PCR. Antimicrobial susceptibility testing results demonstrated that a total of 30 (16.5%) K. pneumoniae isolates showed multiple drug resistances. The thirty MDR K. pneumonia isolates were mainly resistant to amoxicillin (100.0%), doxycycline (86.7%), chloramphenicol (60.0%), compound trimethoprim (60.0%) and trimethoprim (56.7%). Fifty different types of antibiotic resistance genes were found, which included a total of 671 antibiotic resistance genes, in the 30 multi-drug-resistant isolates. The top ten resistance genes were: vanTC-02, aacC, blaCTX-M-04, blaSHV-01, blaSHV-02, ampC-04, blaOXY, tetD, blaTEM and tetA-02. Thirteen mobile genetic elements were detected, of which IS26 (96.67%) and intI1 (96.67%) had the highest frequency. The thirty MDR K. pneumonia isolates were negative for the traA, traF, tnsA, IS1133, ISpa7, ISkpn6, intI2 and intI3 genes. Moreover, a further investigation of integrons revealed that two types of specific gene cassettes (dfrA12 + orfF + aadA2 and dfrA12 + orfF) were identified in class 1 integrons. Multi-locus sequence typing results showed that 22 STs in the thirty MDR K. pneumonia isolates were identified, the main type was ST37 (5/30). Our results illustrate that effective surveillance and strict biosecurity strategies should be taken to prevent the spread of multi-drug-resistant bacteria, and monitor the emergence of mobile genetic elements and integrons.

High Prevalence and Factors Associated With the Distribution of the Integron intI1 and intI2 Genes in Scottish Cattle Herds

Integrons are genetic elements that capture and express antimicrobial resistance genes within arrays, facilitating horizontal spread of multiple drug resistance in a range of bacterial species. The aim of this study was to estimate prevalence for class 1, 2, and 3 integrons in Scottish cattle and examine whether spatial, seasonal or herd management factors influenced integron herd status. We used fecal samples collected from 108 Scottish cattle herds in a national, cross-sectional survey between 2014 and 2015, and screened fecal DNA extracts by multiplex PCR for the integrase genes intI1, intI2, and intI3. Herd-level prevalence was estimated [95% confidence interval (CI)] for intI1 as 76.9% (67.8-84.0%) and intI2 as 82.4% (73.9-88.6%). We did not detect intI3 in any of the herd samples tested. A regional effect was observed for intI1, highest in the North East (OR 11.5, 95% CI: 1.0-130.9, P = 0.05) and South East (OR 8.7, 95% CI: 1.1-20.9, P = 0.04), lowest in the Highlands. A generalized linear mixed model was used to test for potential associations between herd status and cattle management, soil type and regional livestock density variables. Within the final multivariable model, factors associated with herd positivity for intI1 included spring season of the year (OR 6.3, 95% CI: 1.1-36.4, P = 0.04) and watering cattle from a natural spring source (OR 4.4, 95% CI: 1.3-14.8, P = 0.017), and cattle being housed at the time of sampling for intI2 (OR 75.0, 95% CI: 10.4-540.5, P < 0.001). This study provides baseline estimates for integron prevalence in Scottish cattle and identifies factors that may be associated with carriage that warrant future investigation.

Distribution and association of antimicrobial resistance and virulence traits in Escherichia coli isolates from healthy waterfowls in Hainan, China

There are rising concerns about microbes harboring antibiotic resistance genes (ARGs) and virulence-associated genes (VAGs) in humans and food-producing animals. Moreover, ARGs are considered as emerging environmental pollutants, posing probable life-threatening complications in humans and animals. Commensal Escherichia coli (E. coli) strain can carry a large number of VAGs, which may become opportunistic pathogen. The objective of this study was to determine the prevalence and possible association of ARGs and VAGs in E. coli isolates from clinically healthy waterfowls in China's tropical island, Hainan. For this purpose, 311 non-repeating E. coli isolates were evaluated for phenotypic drug resistance linked with ARGs. Additionally, strains were examined for subsequent resistance and virulence genes by uniplex or multiplex PCR and sequencing. Overall, 89 types of antibiotic resistance patterns were analysed, while 25 ARGs and 23 VAGs were observed, of which qnrS (99.4%) and iucD (99.7%) were the most commonly found genes, respectively. Significant positive associations were observed among ARGs and VAGs (p<0.05, OR>1). The strongest association between resistance and virulence gene was observed for qnrS and iss (OR, 76.25; 95% CI, 4.02-1445.42). Our results propose that waterfowls serve as a reservoir of E. coli carrying multi ARGs and various ExPEC associated VAGs. Therefore, this study provides necessary information on the occurrence and possible associations of ARGs and VAGs in healthy waterfowls, which may act as a reference for the regulatory use of antibiotics to stop the direct or indirect spread of these resistant and potential virulent microbes to natural environment.

Detection of mobile genetic elements in multidrug-resistant Klebsiella pneumoniae isolated from different infection sites in Hamadan, west of Iran

Objective

Klebsiella pneumoniae is one of most opportunistic pathogens that can be related to nosocomial infections. Increased acquisitions of multidrug resistance in this bacterium as well as the transfer of genes to other strains have caused concern. Integrons play key role in the acquisition and the spread of resistance genes. The aim of this study was evaluated the frequency of resistance genes sulI, sulII, tetA, tetB, class I (intI gene), class II integrons (intII gene) and the association between multidrug resistance and the presence of integrons in K. pneumoniae.

Results

Antibiotics susceptibility test was performed on 126 of K. pneumoniae isolates. Also, DNA extraction was done and genes were detected using PCR method. In this study, 67 isolates (53%), carrying both the sulI and sulII genes. Forty-five percent tetracycline-resistant isolates were tetA or tetB positive. The prevalence of intI gene was 96%, while only sixteen isolate harboring intII gene (12.5%). Our results showed the high prevalence of integrons in MDR K. pneumoniae, indicating the important role of these genes in the transmission of antibiotic resistance.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13104-021-05748-9.

Characterization and resistant determinants linked to mobile elements of ESBL-producing and mcr-1-positive Escherichia coli recovered from the chicken origin

The spread of antimicrobial resistance (AMR) in Escherichia coli is a complex process linked with various mobile genetic elements (MGEs) like plasmids, transposons, and integrons. This study aimed to determine the co-occurrence of ESBL and mcr-1 and their physical linkage with MGEs in E. coli. E. coli strains of chicken origin were obtained from different commercial farms of eastern China from 2010 to 2011. Antimicrobial sensitivity testing, identification of different antibiotic-resistant genes (ARGs), and prevalence and evidence involvement of integrons, ISEcp1, ISCR1, and ISApl1, were determined. A multiplex PCR was used to detect virulence genes and the phylogenetic clustering of isolates. Conjugation experiments, plasmid replicon typing were performed to know the transferability of ARGs and MGEs. A total of 83.33% of isolates were found to be multidrug-resistant (MDR). The incidence rate of bla_CTX-M, bla_SHV,bla_TEM, and mcr-1 was found to be 30%, 10.95%, 8.09%, and 36.66%, respectively. The most prevalent combination was noticed for mcr-1 and bla_CTX-M 73%, whereas the most prominent bla_CTX-M alleles found, were bla_CTX-M-55 46%, followed by bla_CTX-M-14 31%, and bla_CTX-M-15 13%. The frequency of ISEcp1, ISCR1, ISApl1, and int1 was 27.77%, 53.70%, 51.85%, and 70.37% respectively. Most β-lactamases, especially bla_CTX-M, bla_SHV, and bla_TEM, were associated with ISEcp1, ISCR1, and Integron 1, whereas the ISAPl1-mcr-1 segment was observed in mcr-1-positive E. coli isolates. Phylogrouping revealed that group A was the most predominant phylotype, whereas the common virulence genes detected in these isolates were EHEC, EAEC, and EPEC. Conjugation assay also indicated that multiple genetic elements were involved; common plasmids identified were FIB 61.11%, followed by IncHI2 48.14%, and FrepB 33.33%. Propagation of such MDR strains carrying multiple resistance elements among the bacterial population is a threat of worry.

Dissemination of antibiotic resistance genes (ARGs) via integrons in Escherichia coli: A risk to human health

With the induction of various emerging environmental contaminants such as antibiotic resistance genes (ARGs), environment is considered as a key indicator for the spread of antimicrobial resistance (AMR). As such, the ARGs mediated environmental pollution raises a significant public health concern worldwide. Among various genetic mechanisms that are involved in the dissemination of ARGs, integrons play a vital role in the dissemination of ARGs. Integrons are mobile genetic elements that can capture and spread ARGs among environmental settings via transmissible plasmids and transposons. Most of the ARGs are found in Gram-negative bacteria and are primarily studied for their potential role in antibiotic resistance in clinical settings. As one of the most common microorganisms, Escherichia coli (E. coli) is widely studied as an indicator carrying drug-resistant genes, so this article aims to provide an in-depth study on the spread of ARGs via integrons associated with E. coli outside clinical settings and highlight their potential role as environmental contaminants. It also focuses on multiple but related aspects that do facilitate environmental pollution, i.e. ARGs from animal sources, water treatment plants situated at or near animal farms, agriculture fields, wild birds and animals. We believe that this updated study with summarized text, will facilitate the readers to understand the primary mechanisms as well as a variety of factors involved in the transmission and spread of ARGs among animals, humans, and the environment.

Diverse Gene Cassette Arrays Prevail in Commensal Escherichia coli From Intensive Farming Swine in Four Provinces of China

Multiple-drug resistance bacteria containing antimicrobial resistance genes (ARGs) are a concern for public health. Integrons are bacterial genetic elements that can capture, rearrange, and express mobile gene cassettes responsible for the spread of ARGs. Few studies link genotype and phenotype of swine-related ARGs in the context of mobile gene cassette arrays among commensal Escherichia coli (E. coli) in nonclinical livestock isolates from intensive farms. In the present study, a total of 264 isolates were obtained from 330 rectal swabs to determine the prevalence and characteristics of antibiotic-resistant gene being carried by commensal E. coli in the healthy swine from four intensive farms at Anhui, Hebei, Shanxi, and Shaanxi, in China. Antimicrobial resistance phenotypes of the recovered isolates were determined for 19 antimicrobials. The E. coli isolates were commonly nonsusceptible to doxycycline (75.8%), tetracycline (73.5%), sulfamethoxazole-trimethoprim (71.6%), amoxicillin (68.2%), sulfasalazine (67.1%), ampicillin (58.0%), florfenicol (56.1%), and streptomycin (53.0%), but all isolates were susceptible to imipenem (100%). Isolates [184 (69.7%)] exhibited multiple drug resistance with 11 patterns. Moreover, 197 isolates (74.6%) were detected carrying the integron-integrase gene (intI1) of class 1 integrons. A higher incidence of antimicrobial resistance was observed in the intI1-positive E. coli isolates than in the intI1-negative E. coli isolates. Furthermore, there were 17 kinds of gene cassette arrays in the 70 integrons as detected by sequencing amplicons of variable regions, with 66 isolates (94.3%) expressing their gene cassettes encoding for multiple drug resistance phenotypes for streptomycin, neomycin, gentamicin, kanamycin, amikacin, sulfamethoxazole-trimethoprim, sulfasalazine, and florfenicol. Notably, due to harboring multiple, hybrid, and recombination cassettes, complex cassette arrays were attributed to multiple drug resistance patterns than simple arrays. In conclusion, we demonstrated that the prevalence of multiple drug resistance and the incidence of class 1 integrons were 69.7 and 74.6% in commensal E. coli isolated from healthy swine, which were lower in frequency than that previously reported in China.

Detection of Tn7-Like Transposons and Antibiotic Resistance in Enterobacterales From Animals Used for Food Production With Identification of Three Novel Transposons Tn6813, Tn6814, and Tn6765

Enterobacterales are widely distributed in the gastro-intestinal system of animals and may cause opportunistic infections. Worse still, multidrug-resistant Enterobacterales also poses a serious threat to public health. Tn7-like transposons have been found in several species of the Enterobacterales order and play an important role in dissemination of antibiotic resistance. This study aimed to investigate the distribution and genetic characterization of Tn7-like transposons in Enterobacterales isolates from food animals and their association with antibiotic resistance. Enterobacterales isolated from the samples were identified and classified according to the 16S rDNA sequence. Tn7-like transposons and associated integrons were detected by polymerase chain reaction (PCR) and sequencing. The antibiotic resistance of each Tn7-like transposon positive isolate was detected according to the Kirby-Bauer disk diffusion method. Then, six representative strains were selected to study the genetic environment by whole-genome sequencing (WGS). In total, we isolated 377 Tn7-like transposons positive strains of Enterobacterales. Class 2 integrons were detected in 99.5% of the isolates, and there were high frequency mutation sites especially in base 535, a stop mutation. Many isolates (54.9%) were multidrug-resistant and observed high resistance rates to trimethoprim/sulfamethoxazole and streptomycin. Among these strains, we found three new types of Tn7-like transposons, named Tn6813, Tn6814, and Tn6765. This is the first comprehensive survey that shows Tn7-like transposons in Enterobacterales from animals used for food production in different regions of China. This study also provides an insight into the horizontal transfer of resistance genes associated with Tn7-like transposons.

Presence and Transfer of Antimicrobial Resistance Determinants in Escherichia coli in Pigs, Pork, and Humans in Thailand and Lao PDR Border Provinces

This study aimed to investigate antimicrobial resistance (AMR) characteristics of Escherichia coli isolates from pig origin (including pigs, pig carcass, and pork) and humans in Thailand and Lao People's Democratic Republic (PDR) border provinces. The majority of the E. coli isolates from Thailand (69.7%) and Lao PDR (63.3%) exhibited multidrug resistance. Class 1 integrons with resistance gene cassettes were common (n = 43), of which the most predominant resistance gene cassette was aadA1. The percentage of extended-spectrum beta-lactamase (ESBL) producers was 3.4 in Thailand and 3.2 in Lao PDR. The ESBL genes found were bla_CTX-M14, bla_CTX-M27, and bla_CTX-M55, of which bla_CTX-M55 was the most common (58.6%). Ser-83-Leu and Asp-87-Asn were the predominant amino acid changes in GyrA of ciprofloxacin-resistant isolates. Twenty-two percent of all isolates were positive for qnrS. Class 1 integrons carrying aadA1 from pigs (n = 1) and ESBL genes (bla_CTX-M55 and bla_CTX-M14) from pigs (n = 2), pork (n = 1), and humans (n = 7) were located on conjugative plasmids. Most plasmids (29.3%) were typed in the IncFrepB group. In conclusion, AMR E. coli are common in pig origin and humans in these areas. The findings confirm AMR as One Health issue, and highlight the need for comprehensive and unified collaborations within and between sectors on research and policy.

High prevalence of multi-drug resistances and diversity of mobile genetic elements in Escherichia coli isolates from captive giant pandas

The purpose of this study was to characterize the antimicrobial resistance produced by mobile genetic elements and integron gene cassettes in Escherichia coli isolated from the feces of captive giant pandas. We performed a standard disk diffusion antimicrobial susceptibility test with 84 E. coli isolates and further evaluated the mobile genetic elements and integron gene cassettes. The antimicrobial susceptibility test demonstrated that 43.37% (36/84) of the isolates showed multiple drug resistances. The E. coli isolates mainly showed resistance to aztreonam (86.90%, 73/84) and amoxicillin/clavulanic acid (80.95%, 68/84). The most frequently observed resistance patterns were ampicillin/amoxicillin-clavulanic acid (13.10%, n = 11), and doxycycline/amoxicillin-clavulanic acid (4.76%, n = 4). Further analyses detected 11 mobile genetic elements, of which merA (54/84, 64.30%) had the highest frequency. All isolates were negative for intI3, traA, tnpU, traF, tnp513, tnsA, ISkpn7, ISpa7, ISkpn6, and ISCR1. We further analyzed antimicrobial resistance-related integrons among 30 E. coli isolates (the 27 intI1-positive isolates and the 3 intI2-positive isolates); six gene cassette profiles (dfrA17+aadA5, aadA2, dfrA12+aadA2, dfrA1+aadA1, dfrA1, and aadA1) were identified in the 27 intI1-positive isolates, but not in the three intI2-positive ones. Our study sheds light on the prevalence of multiple drug resistances and the diversity of mobile genetic elements in E. coli isolates, and highlights the necessity to monitor antibiotic resistance in more E. coli strains from captive giant pandas.

Emergence of Escherichia coli isolates producing NDM-1 carbapenemase from waterfowls in Hainan island, China

Carbapenems are traditionally recognized to be the last resort drugs to treat infections due to MDR organisms such as E. coli. As such, the emergence of New Delhi metallo-β-lactamase-producing E. coli strains have become a challenging threat to the public health. In this regard, we examined the molecular characteristics of carbapenem-resistant E. coli (CRE) isolated from waterfowls in China's tropical island, Hainan. A total of 311 single E. coli strains were obtained from 20 various farms of healthy ducks and geese in 2 districts of Hainan island. The CRE strains were initially identified via phenotypic resistance and modified Hodge test. PCR assay and subsequent nucleotide sequencing were used to detect different types of carbapenemase encoding genes (bla_NDM, bla_VIM, bla_IMP, bla_OXA and bla_KPC). In addition, MLST and PFGE analyses were also performed. Among the 311 E. coli strains, 8 strains were detected to produce a single type of carbapenemase i.e. NDM-1 (2.6%). A total of 5 sequence types (STs) were observed, of which ST10 was the most prevalent accounting for 37.5% (3/8). Moreover, these 8 isolates yielded 6 different PFGE clusters but showed approximately related PFGE types, suggesting the propagation of similar clone between the farms. This is the first report on the identification of NDM-1-producing E. coli from waterfowls in Hainan island, China. Our results emphasize the need for better efforts to control the further spread of NDM-1-producing E. coli strains in this tropical island.

Class 1 integrons as predominant carriers in Escherichia coli isolates from waterfowls in Hainan, China

This study was conducted to determine the prevalence of integrons and associated gene cassettes in Escherichia coli (E. coli) isolates from waterfowls in Hainan, China. The antimicrobial resistance profile of the isolates was examined by using disc diffusion test. In addition, PCR, RFLP, plasmid replicon typing and DNA sequencing analyses were used for the characterization of integrase genes (class 1, 2 and 3) and associated gene cassettes. Approximatively, 90% of the isolates were positive for the integrase genes by PCR. Specifically, class 1 and class 2 integrons were found in 252 (81%) and 7 (2.3%) strains, respectively. While 21 (6.7%) isolates were positive for both class 1 and class 2 integrons. However, none of the isolate was positive for the class 3 integrons. In addition, 5 various cassette arrays, dfrA1-orfC, aadA2, aadA1, dfrA1-aadA1, and dfrA1-orfC- aadA1, were found within the variable regions (VRs) of class 1 integron isolates. While only single cassette array, dfrA1-sat2- aadA1, was identified within VRs of class 2 integron isolates. We identified incF plasmid as the most common plasmid type, which was detected in 81 of 243 VRs containing isolates. This study is the first report showing the baseline characteristics of integrons in E. coli isolates from waterfowls in Hainan, China. Our results provide evidence of the waterfowl birds as a reservoir of class 1 and class 2 integrons carrying antibiotic resistance gene cassettes. Therefore, strict preventive measures should be taken to avoid the spread of mobile genetic resistance elements in waterfowls in China.

Diverse Mobile Genetic Elements and Conjugal Transferability of Sulfonamide Resistance Genes (sul1, sul2, and sul3) in Escherichia coli Isolates From Penaeus vannamei and Pork From Large Markets in Zhejiang, China

High prevalence rates of sulfonamide resistance genes sul1, sul2, and sul3 have been observed in Gram-negative bacteria isolated from humans, domestic animals, and aquaculture species worldwide. We investigated the distribution characteristics, location, conjugative transferability, and genetic environments of sul genes from Escherichia coli isolates collected from Penaeus vannamei and pork samples from three large markets in Zhejiang, China. The prevalence rates of sul genes in sulfonamide-resistant E. coli isolates from P. vannamei and pork samples were 90.0 and 88.6%, respectively, and the prevalence of sul1 and sul2 was significantly higher than that of sul3 (p < 0.05). Twenty-four representative sul-positive E. coli isolates were analyzed in detail. Southern blot hybridization confirmed that sul genes of E. coli isolates were located on plasmids and/or chromosomes. Transfer of resistance through conjugation was observed in all 18 E. coli isolates harboring sul genes on plasmids. Replicon typing identified seven different incompatibility groups and IncF was the dominant replicon type among sul gene-containing plasmids from both sources. PCR walking analysis indicated that 87.5% (35/40) of sul gene-related fragments carried insertion sequences (ISs) belonging to a variety of families in diverse sites, with IS26 occurring most frequently. In addition, the sul1 gene was detected mainly in fragments carrying class 1 integrons. Co-location on the same fragment with resistance genes that may contribute to the persistence and dissemination of sul1 and/or sul2 genes. The diversity of mobile genetic elements and resistance genes adjacent to sul3 was much lower than those adjacent to sul1 and sul2, especially those located in chromosomes, which reduced the transmission potential of the sul3 gene. In conclusion, combined with the results of clonal relatedness analysis by PFGE and MLST of 24 representative E. coli isolates from P. vannamei and pork samples, it showed that a small number of sul genes were vertically transmitted among E. coli from P. vannamei and that horizontal gene transfer was likely the main transmission mechanism of sul genes from both sources. Our results provide important information to better understand the risk of transmission of sul genes from seafood and meat to humans.

Antimicrobial resistance and prevalence of diarrheagenic Escherichia coli (DEC), in diarrheic yaks of Tibetan Plateau, China

This study was conducted to test the distribution of diarrheagenic Escherichia coli (DEC) associated genes in fecal isolates from diarrheic yaks of a high remote region of China. Briefly, we obtained 203 fecal samples from diarrheic adult yaks and E. coli strains were isolated and identified via standard methods The antibiotic sensitivity of isolates was determined via disk diffusion method and polymerase chain reaction (PCR) was used to detect the DEC virulence associated genes. Results of the current study showed a high rate of resistance to tetracycline (93.6%) and low rate of resistance to ofloxacin (16.7%) antibiotics. Meanwhile, five different diarrheagenic associated virulence traits were detected including; EAEC (11.80%), EHEC (25.62%), EIEC (17.18%), EPEC (36.92%) and ETEC (11.36%). Moreover, E. coli isolates were positive for all tested DEC associated virulence genes ranging from 1.48% to 33%. Additionally, four isolates were positive for more than one virulence genes. In conclusion, our investigation showed a relatively low number of E. coli virulence genes isolated from diarrheic Tibetan yaks, which could be attributed to the high altitude induced harsh environmental conditions that may not help in the growth and survival of pathogenic organisms. In addition, this study highlights the high level of antibiotic resistance in yaks, therefore; preventive measures should be taken to monitor the antibiotic usage in Tibet region of China.