Food Animals In China Research Articles

Lactobacillus salivarius and Berberine Alleviated Yak Calves' Diarrhea via Accommodating Oxidation Resistance, Inflammatory Factors, and Intestinal Microbiota.

Yaks are important food animals in China; however, bacterial diarrheal diseases frequently occur on the plateau, with limited effective therapies. The objective of this research was to evaluate the effectiveness of Lactobacillus salivarius (LS) and berberine in alleviating diarrhea in yak calves. For this purpose, eighteen healthy yak calves were divided into control (JC), infected (JM), and treatment (JT) groups. Yaks in the JT group were treated with 2 × 1010 CFU/calf L. salivarius and 20 mg/kg berberine, and yaks in the JM and JT groups were induced with multi-drug-resistant Escherichia coli. The results showed that the weight growth rate in the JM group was significantly lower than that in the JC and JT groups. The diarrhea score in the JM group was significantly higher than that in both the JC and JT groups. Additionally, the contents of T-AOC, SOD, GSH-Px, and IL-10 were significantly lower in the JM group than those in the JC and JT groups, while MDA, TNF-α, IL-1β, and IL-6 were significantly higher in the JM group. Microbiota sequencing identified two phyla and twenty-seven genera as significant among the yak groups. Notably, probiotic genera such as Faecalibaculum and Parvibacter were observed, alongside harmful genera, including Marvinbryantia and Lachnospiraceae UCG-001. Our findings indicate that treatment with L. salivarius and berberine significantly reduced diarrhea incidence, improved growth performance, and positively modulated intestinal microbiota, which could provide novel insights for developing new therapies for ruminant diarrhea.

Polymyxin Resistance in Salmonella: Exploring Mutations and Genetic Determinants of Non-Human Isolates.

Until 2015, polymyxin resistance was primarily attributed to chromosomal mutations. However, with the first report of mobile colistin resistance (mcr-1) in commensal Escherichia coli from food animals in China, the landscape has changed. To evaluate the presence of polymyxin resistance in Salmonella spp., a drop screening test for colistin and polymyxin B was carried out on 1156 isolates of non-human origin (animals, food, and the environment), received in Brazil, between 2016 and 2021. Subsequently, 210 isolates with resistant results in the drop test were subjected to the gold-standard test (broth microdilution) for both colistin and polymyxin B. Whole-genome sequencing (WGS) of 102 resistant isolates was performed for a comprehensive analysis of associated genes. Surprisingly, none of the isolates resistant to colistin in the drop test harbored any of the mcr variants (mcr-1 to mcr-10). WGS identified that the most common mutations were found in pmrA (n= 22; T89S) and pmrB (n = 24; M15T, G73S, V74I, I83A, A111V). Other resistance determinants were also detected, such as the aac(6')-Iaa gene in 72 isolates, while others carried beta-lactamase genes (blaTEM-1blaCTX-M-2, blaCMY-2). Additionally, genes associated with fluoroquinolone resistance (qnrB19, qnrS1, oqxA/B) were detected in 11 isolates. Colistin and polymyxin B resistance were identified among Salmonella from non-human sources, but not associated with the mcr genes. Furthermore, the already-described mutations associated with polymyxin resistance were detected in only a small number of isolates, underscoring the need to explore and characterize unknown genes that contribute to resistance.

Current status and trends in antimicrobial use in food animals in China, 2018–2020

Antimicrobial resistance poses a significant threat to global public health, and excessive antimicrobial use (AMU) in animals is a major contributing factor. We used national AMU data for food animals to examine the current status and trends for AMU in food animals in China from 2018–2020. In 2020, China used 32,776.30 tons of antimicrobials in food animals, amounting to 165 g of antimicrobials per ton of animal products. AMU in China increased throughout the 2018–2020 study period; however, the data still showed a consistent and notable reduction from those of 2017, coinciding with the implementation of the China National Action Plan for Combating Animal Antimicrobial Resistance. Among the antimicrobials used, tetracyclines, macrolides and β-lactams (including β-lactam inhibitors) were the most commonly used in food animals. Analysis by antimicrobial class revealed shifts in usage patterns, such as decreased tetracycline use and increased macrolide and β-lactam use. Furthermore, the use of antimicrobial growth promoters decreased sharply, from 51.78% in 2018 to 28.7% in 2020. Compared with AMU data from other countries, China used more antimicrobials, but the values were relatively lower when adjusted for population correction units. These findings highlight China's remarkable efforts in combating antimicrobial resistance and promoting antimicrobial stewardship, thus contributing significantly to global initiatives.

Comprehensive profiling of serotypes, antimicrobial resistance and virulence of Salmonella isolates from food animals in China, 2015-2021.

Salmonella is a ubiquitous foodborne pathogen and mainly transmitted to human farm-to-fork chain through contaminated foods of animal origin. In this study, we investigated the serotypes, antimicrobial resistance and virulence of Salmonella from China. A total of 617 Salmonella isolates were collected from 4 major food animal species across 23 provi nces in China from 2015-2021. Highest Salmonella prevalence were observed in Guangdong (44.4%) and Sandong (23.7%). Chickens (43.0%) was shown to be the major source of Salmonella contamination, followed by pigs (34.5%) and ducks (18.5%). The number of Salmonella increased significantly from 5.51% to 27.23% during 2015-2020. S. Derby (17.3%), S. Enteritidis (13.1%) and S. Typhimurium (11.4%) were the most common serotypes among 41 serotypes identifiedin this study. Antibiotic susceptibility testing showing that the majority of the Salmonella isolates were resistant to neomycin (99.7%), tetracycline (98.1%), ampicillin (97.4%), sulfadiazine/trimethoprim (97.1%), nalidixic acid (89.1%), doxycycline (83.1%), ceftria xone (70.3%), spectinomycin (67.7%), florfenicol (60.0%), cefotaxime (52.0%) and lomefloxacin (59.8%). The rates of resistance to multiple antibiotics in S. Derby and S.Typhimurium were higher than that in S. Enteritidis. However, the rate of resistance to fosfomycin were observed from higher to lower by S. Derby, S. Enteritidis, and S. Typhimurium. Biofilm formation ability analysis found that 88.49%of the Salmonella were able to produce biofilms, of which 236 Salmonella isolates were strong biofilm producer. Among the 26 types of antibiotics resistance genes (ARGs) were identified in this study, 4 ARGs (tetB,sul2,aadA2, and aph(3')-IIa) were highly prevalent. In addition, 5 β-lactam resistance genes (bla TEM, bla SHV, bla CMY-2, bla CTX-M, and bla OXA) and 7 quinolone resistance genes (oqxA, oqxB, qnrB, qnrC, qnrD, qnrS, and qeqA) were detected among these isolates. 12 out of 17 virulence genes selected in this study were commonly presented in the chromosomes of tested isolate, with a detection rate of over 80%, including misL, spiA, stn, pagC, iroN, fim, msgA, sopB, prgH, sitC, ttrC, spaN. This study provided a systematical updating on surveillance on prevalence of Salmonella from food animals in China, shedding the light on continued vigilance for Salmonella in food animals.

Genome-based risk assessment for foodborne Salmonella enterica from food animals in China: A One Health perspective

Salmonella is one of the most common causes of foodborne bacterial disease. Animal-borne foods are considered the primary sources of Salmonella transmission to humans. However, genomic assessment of antimicrobial resistance (AMR) and virulence of Salmonella based on One Health approach remains obscure in China. For this reason, we analyzed the whole genome sequencing data of 134 Salmonella isolates recovered from different animal and meat samples in China. The 134 Salmonella were isolated from 2819 samples (4.75 %) representing various sources (pig, chicken, duck, goose, and meat) from five Chinese provinces (Zhejiang, Guangdong, Jiangxi, Hunan, and Qinghai). AMR was evaluated by the broth dilution method using 13 different antimicrobial agents, and results showed that 85.82 % (115/134) of isolates were resistant to three or more antimicrobial classes and were considered multidrug-resistant (MDR). Twelve sequence types (STs) were detected, with a dominance of ST469 (29.85 %, 40/134). The prediction of virulence genes showed the detection of cdtB gene encoding typhoid toxins in one isolate of S. Muenster recovered from chicken, while virulence genes associated with type III secretion systems were detected in all isolates. Furthermore, plasmid-type prediction showed the abundance of IncFII(S) (13/134; 9.7 %) and IncFIB(S) (12/134; 8.95 %) in the studied isolates. Together, this study demonstrated the ability to use whole-genome sequencing (WGS) as a cost-effective method to provide comprehensive knowledge about foodborne Salmonella isolates in One Health surveillance approach.

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.

Plasmid and chromosomal copies of blaCMY-2 mediate resistance to third-generation cephalosporins in Escherichia coli from food animals in China

The use of antimicrobials in food animals is the major determinant for the propagation of resistant bacteria in the animal reservoir. The objective of this study was to investigate the presence and distribution of third-generation cephalosporin (3GC) -resistant and plasmid-mediated AmpC (pAmpC)-producing Escherichia coli isolated from food animals in Southern China. In total, 744 3GC-resistant and 40 blaCMY-2-positive E. coli strains were recovered from 1656 food animal fecal samples across five rearing regions. The blaCMY-2 genes were located on IncC, IncFIB or IncI1 type plasmids in 12 E. coli isolates. In the other 22 isolates, S1-PFGE and hybridization analyses revealed that the blaCMY-2 gene was chromosomally located and demonstrated a high prevalence of the chromosomally encoded blaCMY-2 gene in E. coli. Plasmid stability and growth curve experiments demonstrated that IncI1, IncC and IncFIB plasmids can exist stably in the host bacteria and with a low growth burden and may be the reason these plasmids can be widely disseminated in breeding environments. Whole genome sequencing indicated that ISEcp1 and IS1294 played important roles in blaCMY-2 transfer to both plasmids and the chromosome. Our study confirmed that blaCMY-2 mediated resistance of food animal-derived E. coli to 3GC and highlights the urgent need for appropriate monitoring programmes.

Escherichia fergusonii, an Underrated Repository for Antimicrobial Resistance in Food Animals.

ABSTRACTA total of 1,400 samples of food animals (pigs, chickens, and ducks) were collected between July and September 2019 in China to uncover the prevalence of E. fergusonii and its potential role in the evolution of antimicrobial resistance (AMR). An isolation of E. fergusonii was performed and pulsed-field gel electrophoresis (PFGE) was used to uncover the genetic relationship. The AMR of E. fergusonii isolates was comprehensively characterized using broth microdilution-based antimicrobial susceptibility testing, S1-PFGE, southern hybridization, whole-genome sequencing, and in-depth bioinformatics analysis. As a result, a total of 133 E. fergusonii isolates were obtained. These isolates could be grouped into 41 PFGE subclades, suggesting a diverse genetic relationship. The resistance phenotypes of sulfafurazole (97.74%) and tetracycline (94.74%) were the most frequently found. Of the E. fergusonii isolates, 51.88% were extended spectrum beta-lactamase (ESBL)-positive. Forty-three different AMR genes were revealed based on 25 genome sequences harboring mcr-1. Briefly, aph(6)-Id, aph(3′′)-Ib and tet(A) genes were the most frequently observed, with the highest rate being 76.00% (19/25). Three mcr-1-harboring plasmids were identified after Nanopore sequencing, including pTB31P1 (IncHI2-IncHI2A, 184,652 bp), pTB44P3 (IncI2, 62,882 bp), and pTB91P1 (IncHI2-IncHI2A, 255,882 bp). Additionally, 25 E. fergusonii isolates harboring mcr-1 were clustered together with other E. fergusonii isolates from different regions and sources available in GenBank, suggesting a possible random process of mcr-1 transmission in E. fergusonii. In conclusion, E. fergusonii is widespread in food animals in China and might be an important reservoir of AMR genes, especially mcr-1, and facilitate the evolution of AMR.IMPORTANCE E. fergusonii, a member of the genus Escherichia, has been reported to transmit via the food chain and cause diseases in humans. However, the prevalence of multidrug-resistant E. fergusonii, especially mcr-1-positive E. fergusonii isolates, has rarely been reported. Here, we collected 1,400 samples from food animals in three provinces of China and obtained 133 E. fergusonii isolates (9.5%). We found that the prevalence of E. fergusonii isolates was diverse, with high levels of antimicrobial resistance. Among them, 18.8% E. fergusonii isolates carried the colistin resistance gene mcr-1. Thus, E. fergusonii may facilitate the evolution of colistin resistance as a reservoir of mcr-1. As far as we know, the prevalence and AMR of E. fergusonii in the food animals in this study was first reported in China. These findings increase our understanding of the role of E. fergusonii in public health and the evolution of antibiotic resistance.

Capsular Genotype and Lipooligosaccharide Class Associated Genomic Characterizations of Campylobacter jejuni Isolates From Food Animals in China.

Campylobacter jejuni (C. jejuni) is the leading causative agent of gastroenteritis and Guillain–Barré syndrome (GBS). Capsular polysaccharide (CPS) and lipooligosaccharide (LOS) contribute to the susceptibility of campylobacteriosis, which have been concern the major evaluation indicators of C. jejuni isolates from clinical patients. As a foodborne disease, food animal plays a primary role in the infection of campylobacteriosis. To assess the pathogenic characterizations of C. jejuni isolates from various ecological origins, 1609 isolates sampled from 2005 to 2019 in China were analyzed using capsular genotyping. Strains from cattle and poultry were further characterized by LOS classification and multilocus sequence typing (MLST), compared with the isolates from human patients worldwide with enteritis and GBS. Results showed that the disease associated capsular genotypes and LOS classes over-represented in human isolates were also dominant in animal isolates, especially cattle isolates. Based on the same disease associated capsular genotype, more LOS class types were represented by food animal isolates than human disease isolates. Importantly, high-risk lineages CC-22, CC-464, and CC-21 were found dominated in human isolates with GBS worldwide, which were also represented in the food animal isolates with disease associated capsular types, suggesting a possibility of clonal spread of isolates across different regions and hosts. This is the first study providing genetic evidence for food animal isolates of particular capsular genotypes harbor similar pathogenic characteristics to human clinical isolates. Collective efforts for campylobacteriosis hazard control need to be focused on the zoonotic pathogenicity of animal isolates, along the food chain “from farm to table.”

Prevalence of Salmonella and Antimicrobial Resistance in Isolates from Food Animals - Six PLADs, China, 2019.

What is already known about this topic? Salmonella causes acute and chronic diseases in food animals, and infected food animals are one of the most important source of human infection. What does this report contribute? The prevalence of Salmonella was 10.5% in chicken samples, 24.4% in pig, 23.3% in duck, and 29.4% in milk. Salmonella isolates were highly resistant to ampicillin (59.60%). What are the implications for public health practices? Data on Salmonella infections among food animals in China could help identify sources and factors related to the spread of Salmonella in food animals and food production chains.

Quantifying Human Health Risks from Virginiamycin Use in Food Animals in China.

Virginiamycin (VM), a streptogramin antibiotic, has been used to promote healthy growth and treat illnesses in farm animals in the United States and other countries. The combination streptogramin Quinupristin-Dalfopristin (QD) was approved in the United States in 1999 for treating patients with vancomycin-resistant Enterococcus faecium (VREF) infections. Many chickens and swine test positive for QD-resistant E. faecium, raising concerns that using VM in food animals might select for streptogramin-resistant strains of E. faecium that could compromise QD effectiveness in treating human VREF infections. Such concerns have prompted bans and phase-outs of VM as growth promoters in the United States and Europe. This study quantitatively estimates potential human health risks from QD-resistant VREF infections due to VM use in food animals in China. Plausible conservative (risk-maximizing) quantitative risk estimates are derived for future uses, assuming 100% resistance to linezolid and daptomycin and 100% prescription rate of QD to high-level (VanA) VREF-infected patients. Up to one shortened life every few decades to every few thousand years might occur in China from VM use in animals, although the most likely risk is zero (e.g., if resistance is not transferred from bacteria in food animals to bacteria infecting human patients). Sensitivity and probabilistic uncertainty analyses suggest that this conclusion is robust to several data gaps and uncertainties. Potential future human health risks from VM use in animals in China appear to be small or zero, even if QD is eventually approved for use in human patients.

The first isolation of Clostridium difficile RT078/ST11 from pigs in China.

We investigated the molecular characteristics and antimicrobial susceptibility of Clostridium difficile isolated from animals in China. We obtained 538 rectal swabs from pigs, chickens and ducks in 5 provinces during 2015 and 2016. C. difficile isolates were characterized by detection of toxin genes, multilocus sequence typing and ribotyping. And antimicrobial susceptibility testing was performed using the agar dilution method. Out of 538 samples, 44 (8.2%) were C. difficile positive with high prevalence in pigs (n = 31). Among these, 39 (88.6%) were toxigenic including 14 (31.8%) that were A+B+CDT+ and 13 (29.5%) A+B+. The remaining 12 (27.3%) were A-B+. We identified 7 ST types and 6 PCR ribotypes. The most predominant type was ST11/RT078 with toxin profile A+B+CDT+ and all were isolated from piglets with diarrhea. ST109 isolates possessed two different toxigenic profiles (A-B-CDT- and A-B+CDT-) and although it was not the most prevalent sequence type, but it was widely distributed between chickens, ducks and pigs in the 5 provinces. All C. difficile isolates were fully susceptible to vancomycin, metronidazole, fidaxomicin, amoxicillin/clavulanate and meropenem but retained resistance to 4 or 5 of the remaining antibiotics, especially cefotaxime, tetracycline, ciprofloxacin, cefoxitin. The RT078/ST11 isolates were simultaneously resistant to cefotaxime, tetracycline, cefoxitin, ciprofloxacin and imipenem. This is the first report of the molecular epidemiology of C. difficile isolated from food animals in China. We identified the epidemic strain RT078/ST11 as the predominate isolate among the animals we screened in our study.

Comparative characterization of nontyphoidal Salmonella isolated from humans and food animals in China, 2003–2011

Food animals are major reservoirs from which specific pathogenic Salmonella strains emerge periodically. Probing the identity and origin of such organisms is essential for formulation of highly-focused infection control measures and analysis of factors underlying dissemination of such strains. In this work, the genetic and phenotypic features of animal and human clinical isolates collected at different geographical localities in China during the period 2003–2011 were characterized and compared. Animal-specific serotypes were identified, with S. Enteritidis, S. Cremieu and S. Fyris being recovered almost exclusively from chicken, ducks and pigs respectively. Nevertheless, only four serotypes were commonly found to be transmitted among both animal and human clinical isolates: S. Enteritidis, S. Typhimurium, S. Derby and S. Indiana. Strains of the serotypes S. Enteritidis and S. Typhimurium not only accounted for up to 50% of all human clinical isolates tested, but often shared identical genetic profiles with the animal isolates. Using a recently identified mobile efflux gene, oqxAB, as genetic marker for assessing the efficiency of transmission between animal and human isolates, we demonstrated that a newly emerged genetic trait could be simultaneously detectable among both animal and human clinical isolates. Findings in this work show that transmission of Salmonellae between animal and human is highly efficient and serotype dependent.

The prevalence of colistin resistance in Escherichia coli and Klebsiella pneumoniae isolated from food animals in China: coexistence of mcr-1 and blaNDM with low fitness cost

Increasing colistin resistance is a global concern because colistin is used as a last resort for the treatment of carbapenem-resistant Enterobacteriaceae infections. The plasmid-mediated colistin resistance gene, mcr-1 was found in distinct bacterial species isolated from humans, animals, and the environment. In this study, farms in four different agricultural provinces in China were investigated to determine the occurrence of the antimicrobial resistance and related genes. A total of 373 Escherichia coli and 54 Klebsiella pneumoniae were isolated from 510 non-duplicated samples. Of the E. coli and K. pneumoniae isolates, 72.7% and 66.7%, respectively, were susceptible to colistin. Isolates resistant to colistin comprised 46.6% of the samples isolated from Shandong, and 17.8% and 16.4% of the samples from Jilin and Henan, respectively. Twenty-six carbapenem-resistant E. coli isolates were resistant to colistin, in which both mcr-1 and blaNDM were present. Specifically, the co-existence was found in isolates from animals and sewage. Most of the resistance genes were located on plasmids and were 40–244 kilobases. Growth curves of transconjugants carrying mcr-1, blaNDM-1, blaNDM-4, blaNDM-5, and blaNDM-9 showed a low fitness cost compared with the recipient. In conclusion, mcr-1 was widespread in E. coli and K. pneumoniae isolated from farms in China. Co-existence of mcr-1 and blaNDM-9 was identified in different sequence types of E. coli with low fitness cost from various origins, indicating an urgent need to take measures for decreasing dissemination.

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

We investigated the occurrence of integrons in antibiotic-resistant Escherichia coli strains isolated from free-ranging food animals, including yaks, piglets, and chickens, in China, and characterized the gene cassettes harbored within the integrons. We examined 432 E. coli strains that exhibited resistance to at least one class of antibiotics. Integrase genes and associated gene cassettes were characterized by polymerase chain reaction (PCR) analysis, restriction fragment-length polymorphism, DNA sequencing, conjugation experiments, and plasmid analysis. Twenty-nine (6.7%) integrons were amplified from the 432 antimicrobial-resistant (AMR) isolates evaluated. Specifically, class 1 and 2 integrons were detected in 26 (6%) and 3 (0.7%) strains, respectively. Meanwhile, 6 different gene cassettes, dfrA1, dfr12, aadA1, aadA2, sat1, and orfF, were detected within 6 variable regions (VRs), of which the dfrA1 + aadA1 array was the most common, identified in 12 of 26 class 1 integrons (46.1%). Meanwhile, only one class 2 integron contained a cassette, and the remaining two contained undetermined VRs. Finally, a conjugation assay confirmed the transfer of 4 different types of class 1 integrons into recipient strains, with plasmid sizes ranging from 20 to 30kb. This is the first report examining the baseline AMR characteristics of E. coli within an extensive farming system of livestock animals in China. Given that integrons were detected in >6% of resistant E. coli strains, precautionary measures are required to prevent the spread of mobile genetic resistance determinants in food animals and monitor their emergence.

High Prevalence of Colistin Resistance and mcr-1 Gene in Escherichia coli Isolated from Food Animals in China.

The objective of this study was to determine the minimal inhibitory concentration of colistin for Escherichia coli from food animals and the possible underlying colistin resistance mechanisms. During 2007–2014, 4,438 E. coli isolates of food animal origins were collected. The susceptibility of colistin was tested by the agar dilution method. Mutations in pmrA, pmrB, and mgrB and the presence of mcr-1 gene were determined by PCR and DNA sequencing. Complementation experiments were carried out to evaluate the contribution of the mutations to colistin resistance. There was a high frequency of colistin resistance in E. coli from pigs on farm (24.1%) and at slaughter (24.3%) in 2013–2014, followed by chickens on farm (14.0%) and at slaughter (9.5%). The resistance frequency of E. coli in cow isolates was the lowest (0.9%). MIC distribution for colistin showed that most isolates (75.2%) were distributed at 0.25 mg/L–0.5 mg/L, followed by 4 mg/L–8 mg/L (16.8%). Compared with the isolates from pigs and chickens recovered during 2013–2014, E. coli isolates collected during 2007–2008 (5.5%) and 2010–2011 (12.4%) showed significantly lower frequency of colistin resistance (P < 0.05). DNA sequencing and complementation experiments failed to detect any insertion inactivation or mutation in pmrA, pmrB, and mgrB associated with colistin resistance. However, 91.0% colistin-resistant isolates were positive for mcr-1. The high frequency of colistin resistance and mcr-1 gene among E. coli isolates from food animals in China urged the need to minimize potential risks of colistin resistance development and the spread of mcr-1 gene.

Surveillance of antimicrobial resistance among Escherichia coli from chicken and swine, China, 2008–2015

The objective of this study was to investigate the antimicrobial resistance trend in Escherichia coli from food animals in China. During 2008–2015, a total of 15,130 E. coli were isolated from chicken and swine from seven provinces. The susceptibilities of these isolates to nine classes of antimicrobial agents were determined using broth microdilution susceptibility method. The findings of this study include: (1) multi-drug resistance was highly prevalent in E. coli; (2) these E. coli isolates showed high resistant rate (>80%) to several old drugs, including ampicillin, tetracycline and sulfisoxazole; (3) increasing resistance to colistin, florfenicol and ceftiofur was observed; (4) the E. coli isolates from different provinces had different resistance patterns. All these data highlight the rising problem of antimicrobial resistance. It is urgent to improve the management of animal production and enhance the proper use of antimicrobials in China as well as the other countries.

Plasmid-Mediated Colistin Resistance in Animals and Humans in China

Polymyxins — polymyxin B and polymyxin E (colistin) — are drugs of last resort in treating multidrug-resistant gram-negative infections. Previously, colistin resistance was attributed to chromosomal mutations and was not known to disseminate widely. Prompted by an observed increase in colistin resistance in isolates from food animals in China, investigators sought the mechanism. They ultimately identified plasmid-mediated colistin resistance (MCR-1) in Escherichia coli from a …

Emergence of plasmid-mediated colistin resistance mechanism MCR-1 in animals and human beings in China: a microbiological and molecular biological study

Until now, polymyxin resistance has involved chromosomal mutations but has never been reported via horizontal gene transfer. During a routine surveillance project on antimicrobial resistance in commensal Escherichia coli from food animals in China, a major increase of colistin resistance was observed. When an E coli strain, SHP45, possessing colistin resistance that could be transferred to another strain, was isolated from a pig, we conducted further analysis of possible plasmid-mediated polymyxin resistance. Herein, we report the emergence of the first plasmid-mediated polymyxin resistance mechanism, MCR-1, in Enterobacteriaceae. The mcr-1 gene in E coli strain SHP45 was identified by whole plasmid sequencing and subcloning. MCR-1 mechanistic studies were done with sequence comparisons, homology modelling, and electrospray ionisation mass spectrometry. The prevalence of mcr-1 was investigated in E coli and Klebsiella pneumoniae strains collected from five provinces between April, 2011, and November, 2014. The ability of MCR-1 to confer polymyxin resistance in vivo was examined in a murine thigh model. Polymyxin resistance was shown to be singularly due to the plasmid-mediated mcr-1 gene. The plasmid carrying mcr-1 was mobilised to an E coli recipient at a frequency of 10(-1) to 10(-3) cells per recipient cell by conjugation, and maintained in K pneumoniae and Pseudomonas aeruginosa. In an in-vivo model, production of MCR-1 negated the efficacy of colistin. MCR-1 is a member of the phosphoethanolamine transferase enzyme family, with expression in E coli resulting in the addition of phosphoethanolamine to lipid A. We observed mcr-1 carriage in E coli isolates collected from 78 (15%) of 523 samples of raw meat and 166 (21%) of 804 animals during 2011-14, and 16 (1%) of 1322 samples from inpatients with infection. The emergence of MCR-1 heralds the breach of the last group of antibiotics, polymyxins, by plasmid-mediated resistance. Although currently confined to China, MCR-1 is likely to emulate other global resistance mechanisms such as NDM-1. Our findings emphasise the urgent need for coordinated global action in the fight against pan-drug-resistant Gram-negative bacteria. Ministry of Science and Technology of China, National Natural Science Foundation of China.

Increasing prevalence of extended-spectrum cephalosporin-resistant Escherichia coli in food animals and the diversity of CTX-M genotypes during 2003–2012

The aim of this study was to investigate the trends and the diversity of CTX-M types of extended-spectrum β-lactamase (ESBL) in Escherichia coli isolated from food animals in China over a ten-year period. From 2003 to 2012, 2815 E. coli isolates collected from diseased animals (chickens, pigs, and waterfowl) were screened for the prevalence of CTX-M genes. CTX-M-positive isolates were tested for their susceptibilities to 10 antimicrobial agents and the clonal relationship of CTX-M-producing E. coli isolates was also assessed. Overall, 677 (20.1%) of the 2815 E. coli isolates carried CTX-M genes. Eighteen different types of CTX-M ESBLs were identified, with CTX-M-14, CTX-M-55, and CTX-M-65 being the most dominant genotypes. The occurrence of CTX-M-producing E. coli increased significantly from 5.7% in 2003–2005 to 35.3% in 2009–2012 (p<0.0001). High genetic heterogeneities were observed in the CTX-M-producing E. coli isolates. Most CTX-M-producing strains were also resistant to other classes of antimicrobials. Compared to isolates carrying CTX-M-9 subgroup of ESBLs, isolates carrying CTX-M-1 subgroup ESBLs showed significantly higher resistance rates to ceftazidime, amikacin, and fosfomycin (p<0.01). The study reported the dramatic increase of CTX-M ESBLs in E. coli isolated from animals overtime in China. The increasing incidence of CTX-M-55 with high hydrolytic activity against ceftazidime and the widely spread co-resistance in CTX-M-producing isolates alarm the serious antimicrobial resistance situation in China and highlight the need for urgent control strategies to limit the dissemination of those resistant genes in China.