Prevalence and multilocus sequence typing of Clostridium perfringens isolated from 4 duck farms in Shandong province, China

Distribution of antibiotic resistance genes and their pathogen hosts in duck farm environments in south-east coastal China

Livestock farms are major reservoirs of antibiotic resistance genes (ARGs) that are discharged into the environment. However, the abundance, diversity, and transmission of ARGs in duck farms and its impact on surrounding environments remain to be further explored. Therefore, the characteristics of ARGs and their bacterial hosts from duck farms and surrounding environment were investigated by using metagenomic sequencing. Eighteen ARG types which consist of 823 subtypes were identified and the majority conferred resistance to multidrug, tetracyclines, aminoglycosides, chloramphenicols, MLS, and sulfonamides. The floR gene was the most abundant subtype, followed by sul1, tetM, sul2, and tetL. ARG abundance in fecal sample was significantly higher than soil and water sample. Our results also lead to a hypothesis that Shandong province have been the most contaminated by ARGs from duck farm compared with other four provinces. PcoA results showed that the composition of ARG subtypes in water and soil samples was similar, but there were significant differences between water and feces samples. However, the composition of ARG subtypes were similar between samples from five provinces. Bacterial hosts of ARG subtypes were taxonomically assigned to eight phyla that were dominated by the Proteobacteria, Firmicutes, Bacteroidetes, and Actinobacteria. In addition, some human bacterial pathogens could be enriched in duck feces, including Enterococcus faecium, Acinetobacter baumannii, and Staphylococcus aureus, and even serve as the carrier of ARGs. The combined results indicate that a comprehensive overview of the diversity and abundance of ARGs, and strong association between ARGs and bacterial community shift proposed, and benefit effective measures to improve safety of antibiotics use in livestock and poultry farming. KEY POINTS: • ARG distribution was widespread in the duck farms and surroundings environment • ARG abundance on the duck farms was significantly higher than in soil and water • Human bacterial pathogens may serve as the vectors for ARGs.

Emergence of genetic diversity and multi-drug resistant Clostridium perfringens from wild birds

BACKGROUND

Clostridium perfringens (C. perfringens) is an important zoonotic microorganism that can cause animal and human infections, however information about the prevalence status in wild birds of this pathogenic bacterium is currently limited.

RESULT

In this study, 57 strains of C. perfringens were isolated from 328 fecal samples of wild birds. All the isolates were identified as type A and 70.18% of the isolates carried the cpb2 gene. Antimicrobial susceptibility testing showed that and 22.80% of the isolates were classified as multidrug-resistant strains. The MLST analysis of the 57 isolates from wild birds was categorized into 55 different sequence types (STs) and clustered into eight clonal complexes (CCs) with an average of 20.1 alleles and the Simpson Diversity index (Ds) of 0.9812, and revealed a high level of genetic diversity within the C. perfringens populations. Interestingly, the isolates from swan goose were clustered in the same CC while isolates from other bird species were more scattered suggesting that a potential difference in genetic diversity among the C. perfringens populations associated with different bird species.

CONCLUSION

C. perfringens exhibits a wide range of host adaptations, varying degrees of antimicrobial resistance, and a high degree of genetic diversity in wild birds. Understanding the prevalence, toxin type, antimicrobial resistance, and genetic diversity of C. perfringens in wildlife populations is essential for developing effective strategies for disease control and management.

Genomic analysis of Clostridium perfringens type D isolates from goat farms

C. perfringens type D strains are the leading cause of enterotoxaemia in ruminants such as goats, sheep, and cattle. However, there has been no prior research on the genomic characteristics of C. perfringens type D strains from various regions in China. Here, we investigated the antibiotic resistance, genomic characteristics, and phylogenetic relationship of C. perfringens type D isolates recovered from goat farms in Shaanxi, Gansu, and Ningxia provinces. The antibiotic resistance test indicated that the isolates displayed high minimum inhibitory concentration (MIC) values to sulfafurazole, whereas the other antibiotics tested, such as penicillin, enrofloxacin, and florfenicol, worked well on them. Additionally, only tetracycline resistance genes [tetA(P) and tetB(P)] were identified from the isolates. A collective of 13 toxin genes, including etx and cpe were detected among the isolates. Sequence comparison revealed that the etx and cpe genes shared high sequence identities, and they could coexist on a pCW3-like plasmid, representing a potential risk to both animal breeding and public health. Phylogenetic analysis using core genome multi-locus sequence typing (cgMLST) and core genome single nucleotide polymorphisms (SNPs) revealed the close genetic relationship and potential regional/transregional transmission of the C. perfringens type D isolates in Shaanxi and Gansu provinces. Furthermore, pan-genomic analysis suggested the functional differences at the protein-coding gene level, although isolates from the same source shared a close genetic relationship. In conclusion, this study indicated the antibiotic resistance, virulence markers, potential transregional transmission, and genomic diversity of C. perfringens type D strains from various regions in China, which could provide references for the prevention of C. perfringens foodborne diseases and further research.

Genome-wide association analysis explores the genetic loci of amino acid content in duck's breast muscle

BACKGROUND

Amino acids are the basic components of protein and an important index to evaluate meat quality. With the rapid development of genomics, candidate regions and genes affecting amino acid content in livestock and poultry have been gradually revealed. Hence, genome-wide association study (GWAS) can be used to screen candidate loci associated with amino acid content in duck meat.

RESULT

In the current study, the content of 16 amino acids was detected in 358 duck breast muscles. The proportion of Glu to the total amino acid content was relatively high, and the proportion was 0.14. However, the proportion of Met content was relatively low, at just 0.03. By comparative analysis, significant differences were found between males and females in 3 amino acids, including Ser, Met, and Phe. In addition, 12 SNPs were significantly correlated with Pro content by GWAS analysis, and these SNPs were annotated by 7 protein-coding genes; 8 significant SNPs were associated with Tyr content, and these SNPs were annotated by 6 protein-coding genes. At the same time, linkage disequilibrium (LD) analysis was performed on these regions with significant signals. The results showed that three SNPs in the 55-56 Mbp region of chromosome 3 were highly correlated with the leader SNP (chr3:55526954) that affected Pro content (r2 > 0.6). Similarly, LD analysis showed that there were three SNPs in the 21.2-21.6 Mbp region of chromosome 13, which were highly correlated with leader SNP (chr13:21421661) (r2 > 0.6). Moreover, Through functional enrichment analysis of all candidate genes. The results of GO enrichment analysis showed that several significant GO items were associated with amino acid transport function, including amino acid transmembrane transport and glutamine transport. The results further indicate that these candidate genes are closely associated with amino acid transport. Among them, key candidate genes include SLC38A1. For KEGG enrichment analysis, CACNA2D3 and CACNA1D genes were covered by significant pathways.

CONCLUSION

In this study, GWAS analysis found a total of 28 significant SNPs affecting amino acid content. Through gene annotation, a total of 20 candidate genes were screened. In addition, Through LD analysis and enrichment analysis, we considered that SERAC1, CACNA2D3 and SLC38A1 genes are important candidate genes affecting amino acid content in duck breast muscle.

Prevalence and Antibiotic Resistance Profile of Clostridium perfringens Isolated from Pork and Chicken Meat in Vietnam

Clostridium perfringens is one of the most important zoonotic pathogens as it can cause food poisoning in humans and necrotic enteritis in both animals and humans. Meat, especially pork and chicken meat, is considered the main vehicle for the transmission of C. perfringens from animals to humans. The purpose of this study was to determine the prevalence, toxinotype, and antimicrobial resistance profile of C. perfringens isolated from pork and chicken meat sold in Vietnam. The isolation results showed that 15/50 (30%) of pork samples and 8/50 (16%) of chicken meat samples were contaminated with C. perfringens. The isolates exhibited their highest resistance rate to tetracycline (21/23; 91.30%) and clindamycin (10/23; 43.48%). On the contrary, their lowest resistance rates were observed in response to imipenem (2/23; 8.70%) and cefoxitin (1/23; 4.35%). In particular, 34.78% (8/23) of C. perfringens isolates were identified to be multidrug-resistant strains. The results of toxin genotyping indicated that all isolates were positive for the cpa gene and belonged to type A.

Toxin gene detection and antibiotic resistance of Clostridium perfringens from aquatic sources

Clostridium perfringens is a zoonotic opportunistic pathogen that produces toxins that can cause necrotic enteritis and even "sudden death disease". This bacterium is widely distributed in the intestines of livestock and human, but there are few reports of distribution in aquatic animals (Hafeez et al., 2022). In order to explore the isolation rate of C. perfringens and the toxin genes they carry, 141 aquatic samples, including clams (Ruditapes philippinarum), oysters (Ostreidae), and mud snails (Bullacta exerata Philippi), were collected from the coastal areas of Shandong Province, China. C. perfringens strains were tested for cpa, cpb, etx, iap, cpb2, cpe, netB, and tpeL genes. 45 clam samples were boiled at 100 °C for 5 min before bacteria isolation. 80 strains were isolated from 141 samples with the positive rate being 57 %.And the positive rates of cooked clams was 87 % which was higher than the average. In detection of 8 toxin genes, all strains tested cpa positive, 3 strains netB positive, and 2 cpb and cpe, respectively. 64 strains were selected to analyze the antibiotic resistance phenotype of 10 antibiotics. The average antibiotic resistance rates of the strains to tetracycline, clindamycin, and ampicillin were 45 %, 20 %, and 16 % respectively, and the MIC of 4 strains to clindamycin was ≥128 μg/mL. A high isolation rate of C. perfringens from aquatic animals was shown, and it was isolated from boiled clams for the first time, in which cpe and netB toxin genes were detected for the first time too. The toxin encoded by cpe gene can cause food poisoning of human, thus the discoveries of this study have certain guiding significance for food safety. Antibiotics resistant C. perfringens of aquatic origin may arise from transmission in the terrestrial environment or from antibiotic contamination of the aquaculture environment and is of public health significance.

Characterization and multilocus sequence typing of Clostridium perfringens isolated from patients with diarrhoea and food poisoning in Tai'an region, China

OBJECTIVES

Clostridium perfringens (C. perfringens) is a significant opportunistic pathogen. This study aims to examine the occurrence of C. perfringens in patients with diarrhoea and food poisoning and compare the genetic similarities with strains found in poultry retail markets and poultry farms in the same city (Tai'an, China).

METHODS

Clostridium perfringens was isolated from 30 human faecal samples and genotyped using multiplex PCR. The antimicrobial susceptibility test was conducted using the Kirby-Bauer disk diffusion method. Genetic relationships were analysed through Multi-locus sequence typing (MLST) and Phylogenetic analysis.

RESULTS

The positive rate of C. perfringens was found to be 96.67%. Among the positive samples, 91.67% of the faecal samples from patients with food poisoning contained type F strains of C. perfringens, while only 16.67% of the samples from diarrhoea cases contained type F. The drug susceptibility test revealed that the majority of isolates displayed broad-spectrum antimicrobial resistance. Out of the 57 isolates tested for drug susceptibility, 89.47% demonstrated resistance to at least three antibiotics. The MLST results indicated that strains originating from the same host and environment tended to be more closely related. However, certain strains associated with food poisoning and diarrhoea in patients shared the same ST and CC as some strains found in the retail market. These strains were also found to be phylogenetically similar to some retail market strains, suggesting potential risks to human health.

CONCLUSIONS

Therefore, it is crucial to enhance the management of poultry retail markets in order to mitigate these associated risks.

A Broad-Spectrum Phage Endolysin (LysCP28) Able to Remove Biofilms and Inactivate Clostridium perfringens Strains

Clostridium perfringens is a gram-positive, anaerobic, spore-forming bacterium capable of producing four major toxins which cause disease symptoms and pathogenesis in humans and animals. C. perfringens strains carrying enterotoxins can cause food poisoning in humans and are associated with meat consumption. An endolysin, named LysCP28, is encoded by orf28 from C. perfringens bacteriophage BG3P. This protein has an N-terminal glycosyl-hydrolase domain (lysozyme) and a C-terminal SH3 domain. Purified LysCP28 (38.8 kDa) exhibited a broad spectrum of lytic activity against C. perfringens strains (77 of 96 or 80.21%), including A, B, C, and D types, isolated from different sources. Moreover, LysCP28 (10 μg/mL) showed high antimicrobial activity and was able to lyse 2 × 10⁷ CFU/mL C. perfringens ATCC 13124 and C. perfringens J21 (animal origin) within 2 h. Necessary due to this pathogenic bacterium's ability to form biofilms, LysCP28 (18.7 μg/mL) was successfully evaluated as an antibiofilm agent in both biofilm removal and formation inhibition. Finally, to confirm the efficacy of LysCP28 in a food matrix, duck meat was contaminated with C. perfringens and treated with endolysin (100 µg/mL and 50 µg/mL), which reduced viable bacteria by 3.2 and 3.08 units-log, respectively, in 48 h at 4 °C. Overall, the endolysin LysCP28 could potentially be used as a biopreservative to reduce C. perfringens contamination during food processing.

Prevalence, Antibiotic Resistance, Toxin-Typing and Genotyping of Clostridium perfringens in Raw Beef Meats Obtained from Qazvin City, Iran

Background: Clostridium perfringens is one of the highest prevailing spore-forming foodborne pathogens, which is widely distributed and causes severe disease and outbreaks in humans and animals. Raw meat and poultry are the main vehicles of this pathogen. In this study, we investigated the prevalence, antibiotic resistance pattern, toxin-encoding genes and genetic diversity of C. perfringens isolates from raw whole and minced meat samples purchased from local markets in Qazvin city, Iran (the source of beef cattle production was also located in Qazvin city, Iran). Methods: We used conventional culture-based and Kirby–Bauer disk diffusion and conventional and arbitrary primer PCR methods. Results: A total of 18 C. perfringens strains were isolated from 133 raw meat samples (13.53%). Up to 44.4 and 55.5% of these isolates were detected in raw minced and whole meat samples, respectively. We found that 72.2, 66.6, 61.1, 37.8 and 33.3% of the C. perfringens isolates were resistant to ampicillin, tetracycline, amoxicillin, ciprofloxacin and chloramphenicol antibiotics, respectively. Multidrug resistance was found in 38% of the isolates. Among the four main toxin genes evaluated, the Cpa gene was detected in all isolates, and 61.1% of the isolates were mostly recognized as type A C. perfringens. High levels of genetic diversity were observed among the isolates, and they were classified into five distinct groups. Conclusions: The isolates from whole meat samples were more resistant to antibiotics. However, toxin genes were more detected in the isolates from minced meat samples. Our findings suggest that contamination of raw meat products with multidrug resistant C. perfringens could be regarded as one of the concerning pathogens in these products. Comprehensive monitoring of C. perfringens isolates is strongly recommended.

Virulent phage vB_CpeP_HN02 inhibits Clostridium perfringens on the surface of the chicken meat

Clostridium perfringens is a well-known pathogen that causes foodborne disease. With a high prevalence of contamination in food, an efficient strategy is needed to decontaminate those contaminated foods and control the emergence of foodborne disease. In this study, the C. perfringens-specific lytic phage vB_CpeP_HN02 (designated as phage HN02) was isolated from chicken feces. Electron microscopy and phylogenetic analysis suggested that phage vB_CpeP_HN02 is a novel phage of the family Podoviridae. Phage HN02 had good pH (5-11) and temperature tolerance (< 70 °C). Phage HN02 exhibited a broad host range of C. perfringens isolates (42.86%). The complete genome of the phage HN02 was sequenced and revealed a linear double-stranded DNA genome. The 17,754-bp genome (GenBank MW815121) with average GC content of 28.2% includes 22 predicted open reading frames, of which only 10 were annotated with known functions. Phylogenetic analysis of the available C. perfringens phage major capsid protein demonstrated that phage HN02 is closely related to virulent C. perfringens phage phi24R and CPD2. When phage HN02 was applied to chicken meat samples stored at 4 °C for 72 h with 1 × 10⁶ to 1 × 10⁹ PFU/g, 95% to 99% of C. perfringens were inactivated on chicken meat surfaces after storage at 4 °C for 72 h, respectively. It should be noted that C. perfringens could be completely lysed by a high dose of phage HN02 (1 × 10¹⁰ PFU/g) after 48 h treatment in chicken samples. Through the lytic activity testing, phage HN02 showed good antimicrobial effects, and can be used as an antibacterial agent for biocontrol of C. perfringens in meat products.

Investigation of Clostridium perfringens in small-scale commercial broiler flocks in Mymensingh district of Bangladesh

Background and Aim

Necrotic enteritis (NE) is one of the most prevalent diseases in broiler poultry caused by Clostridium perfringens connected with significant economic losses. A cross-sectional survey was conducted in Mymensingh district of Bangladesh to assess the prevalence of C. perfringens through toxinotyping molecular assay and confirm the risk factors for NE, including antimicrobial-resistant (AMR) status of the isolates.

Materials and Methods

We included 40 small-scale commercial broiler farms randomly selected from two subdistricts of Mymensingh district of Bangladesh. As an individual sample, 240 cloacal swabs, and as a pooled sample, 40 drinking water, 40 workers' hand washing, 40 litter swab, and 40 feed samples were collected and evaluated by culture, biochemical, and molecular assays. A pretested semi-structured interview questionnaire was employed to capture flock-level data on risk factors from the farm owners. The flock-level data on risk factors were assessed through univariable and multivariable logistic regression analyses with p<0.05 was considered statistically significant.

Results

Overall flock-level prevalence of C. perfringens was estimated to be 10.3% (95% confidence interval [CI] 7.5-13.6%). Litter swab (pooled) was found to be highly contaminated with C. perfringens (25.0%, 95% CI: 12.7-41.2%) followed by the cloacal swab (10.4%, 95% CI: 6.9-15.0%) and feed sample (5.0%, 95% CI: 0.6-16.9%). History of coccidia infection (Adjusted odds ratio =33.01, 95% CI: 2.14-507.59, p=0.01) was significantly associated with flock-level C. perfringens infection status. In this study, 78.1% isolates were found as multidrug-resistant as they demonstrated resistance to 3-5 antimicrobial agents.

Conclusion

Evidence-based control options need to be taken through the uses of prebiotics and probiotics, biosecurity, and hygienic measurement, including control of coccidia infection, is needed to lessen the NE infection and AMR related to this pathogen in small-scale commercial broiler poultry.

Prevalence and multilocus sequence typing of Clostridium perfringens isolated from different stages of a duck production chain

Clostridium perfringens (C. perfringens) is a zoonotic microorganism and rarely reported in duck production chain. This study aimed to investigate prevalence, serotype distribution, antibiotic resistance and genetic diversity of C. perfringens at different stages of a duck production chain. In total, 319 samples were collected from a large-scale rearing and slaughter one-stop enterprise in Weifang, China, of which 42.95% of samples were positive for C. perfringens. All isolates were genotype A. Cpe and cpb2 genes were found in 2.54% and 24.87% of the isolates, respectively. Antimicrobial susceptibility testing revealed that 55.47% of the isolates resistant to at least 5 classes of commonly used antibiotics. Multilocus sequence typing (MLST) results showed that 65 representative isolates were divided into 47 sequences types (STs), 33.85% of them were included into four clonal complexes (CC). Some of isolates from breeding and slaughtering stages were distributed in the same CC or ST, indicating duck products may be contaminated by C. perfringens originated from the breeding stage. Part of duck isolates were distributed in the same CC as human isolates and systemically close with human isolates. The high contamination rates of duck products, the isolates with multi-drug antibiotic resistance or the cpe gene, and the close relationship between strains from human and ducks, indicated potential public health risks, not only control measures at slaughtering stage but also at rearing stage should be considered to reduce this risks.

Clonal diversity of Clostridium perfringens human clinical isolates with various toxin gene profiles based on multilocus sequence typing and alpha-toxin (PLC) typing

OBJECTIVES

Clostridium perfringens is a common anaerobic pathogen causing enteritis/enterocolitis and wound infections in humans. We analyzed clonal diversity and toxin gene prevalence in C. perfringens clinical isolates from humans in northern Japan.

METHODS

Prevalence of nine toxin genes was analyzed for 585 C. perfringens isolates from patients collected for 20-month period between May 2019 and December 2020 by molecular methods. Sequence type (ST) based on multilocus sequence typing (Xiao's scheme) and alpha-toxin (PLC) sequence type were determined for a total of 124 isolates selected in the present study along with those in our previous study (2017-2018).

RESULTS

Toxinotypes A (68.2%) was the most frequent, followed by F (31.6%), and G (0.2%), while additional toxin genes encoding binary enterotoxin (BEC/CPILE) and beta2 toxin were identified in one and six isolates, respectively. Among the 124 isolates with various toxin gene profiles, 62 STs including 53 novel types were identified, revealing the presence of six clonal complexes (CCs) consisting of 27 STs. Most of enterotoxin gene (cpe)-positive isolates belonged to CC36, CC41, and CC117. Based on 22 key amino acids in alpha toxin sequence, four PLC types (I-IV) including 21 subtypes were classified, and their relation to individual STs/CCs was clarified. Two isolates harboring bec/cpile belonged to different STs (ST95, ST131) and PLC types (If, IVb), indicating distribution of this toxin gene to distinct lineages.

CONCLUSIONS

The present study revealed the diversity in C. perfringens clones of human origin with various toxin gene profiles represented by ST/CC and PLC type.

Prevalence and characterization of Clostridium perfringens isolated from different chicken farms in China

Clostridium perfringens (C. perfringens) is a common pathogenic microorganism present in nature, which can cause animal and human diseases, such as necrotizing enteritis (NE) in poultry. Little is known about the current prevalence status of C. perfringens from poultry farms of different types and regions in China. From December 2018 to August 2019, we investigated the prevalence, genotype distribution and drug resistance of C. perfringens from Guangdong, Pingyin, Tai'an and Weifang. A total of 622 samples were collected and processed for C. perfringens isolation, among which 239 (38.42%) samples were determined to be positive for C. perfringens. A total of 312 isolates of C. perfringens were recovered (1-5 strains were isolated for each positive sample), and 98.72% of the isolates were identified as type A, while the others were type F. Antimicrobial susceptibility testing revealed that 47.71% of the isolates were resistant to at least five classes of commonly used antibiotics. Multilocus sequence typing (MLST) showed that 74 representative isolates were divided into 63 sequence types (STs), and the Simpson's diversity index (Ds) of the STs for the five farms was 0.9799. 37.84% of the isolates were classified into seven clonal complexes (CC1-CC7), and the isolates from the same farm were more concentrated in the minimum spanning tree. In addition, some cloaca isolates and feed isolates were distributed in the same ST or CC; this result indicates that the C. perfringens in chicken can come from the environment (feed etc.).

Prevalence and multilocus sequence typing of Clostridium perfringens isolated from retail chicken products and diseased chickens in Tai'an region, China

Background

Clostridium perfringens is an important zoonotic microorganism, which can cause diseases in animals and humans under suitable conditions. Contamination of C. perfringens in chicken products has been reported worldwide, but the genetic diversity and relationship of isolates were seldom analyzed.

Objectives

The current study was undertaken to investigate the prevalence of C. perfringens from retail chicken products and sick chickens with suspected necrotic enteritis (NE) in Tai'an area, China.

Methods

In total, 295 samples were collected from Tai'an large poultry retail market and veterinary hospital in 2018, then the isolates were tested for toxin genes, drug resistance and multilocus sequence typing (MLST).

Results

Overall, 138 (46.78%) samples were determined to be positive for C. perfringens, and 99.37% of the isolates were identified as C. perfringens type A, with the remaining isolates being type F; 18.99% of the isolates were positive for cpb2 gene. Antimicrobial susceptibility testing revealed that 52.27% of the isolates from poultry retail market and diseased chickens showed multiple antibiotic resistance. MLST results showed that 50 analyzed isolates can be divided into 39 sequences types (STs), clustered in three clonal complexes (CCs) and 23 singletons. Although most of the isolates belong to type A, considerable genetic diversity can be observed, with the Simpson's diversity index up to 0.9181. MLST results and phylogenetic analysis showed that a portion of the isolates from humans and chickens were assigned to the same clusters in the phylogenetic tree or found to be in the same CCs, indicating the chicken isolates and the human isolates are related in certain stratification.

Conclusions

This study showed that the contamination rate of C. perfringens in the local retail chicken products was relatively high. Most of the isolates exhibit broad‐spectrum antimicrobial resistance. The high antibiotic resistance of C. perfringens isolates and the relationship between isolates from human and chicken indicated potential public health risks.

Evaluation of different antigenic preparations against necrotic enteritis in broiler birds using a novel Clostridium perfringens type G strain

OBJECTIVE

Keeping in view, the constraints faced by the Indian broiler industry with lack of a suitable vaccine against Necrotic Enteritis (NE), a study has been proposed to explore the prevalence and detail characterization of C. perfringens type G in NE suspected broiler chicken in the process of suitable vaccine development.

METHODS

Intestinal scrapings/faecal contents of NE suspected broiler chickens were screened to establish the prevalence of C.perfringens type G in broiler birds. A most pathogenic, highly resistant type G isolate of C. perfringens, bearing both tpeL and gapC gene was selected for preparation of three different vaccine formulations, and to evaluate their immunogenic potential in broiler birds.

RESULTS

Screening of clinical samples of NE suspected broiler birds revealed C. perfringens type G, bearing gapC gene in 51.22% samples, of which 47.62% revealed tpeL gene. Seven of the tpeL^pos type G isolates were comparatively more pathogenic for mice, of which, one exhibited multidrug resistance towards ciprofloxacin, norfloxacin, tetracycline and levofloxacin. The sonicated supernatant (SS) prepared from the selected tpeL and gapC positive isolate could maintain a significantly higher protective IgG response than toxoid and bacterin preparation from the 21st to 28^thday of age in immunized birds.

CONCLUSION

The additional TpeL toxin in C. perfringens type G has been proved to be an additional key biological factor in the pathogenesis of NE in broiler chickens. Considering the release of more immunogenic proteins, the SS proved to be a better immunogenic preparation against NE with a multiple immunization dose.

Tracing Clostridium perfringens strains along the chicken production chain from farm to slaughter by multilocus sequence typing

The current study is undertaken to characterize the prevalence, genotypes distribution, antibiotic resistance and genetic diversity of Clostridium perfringens (C. perfringens) collected from different stages of a chicken production chain. In total, 579 samples from a broiler farm and 378 samples from the slaughterhouse were collected from a large-scale rearing and slaughter one-stop enterprise in Weifang, China, between June and July 2019, of which 30.40% of the samples from farm and 54.50% of samples from slaughterhouse were determined to be positive for C. perfringens, respectively. The contamination of chicken products was relatively serious, with the total positive rate of carcasses at 59.73%; the positive rate of carcass samples was the highest in the evisceration process, which might be the critical point of C. perfringens contamination. A total of 476 isolates of C. perfringens were recovered; and 99.58% of recovered isolates were identified as type A, with the remaining isolates being type G. Antimicrobial susceptibility testing revealed that 97.15% of the isolates showed multiple antibiotic resistance and 67.89% of them were resistant to at least five classes of commonly used antibiotics. Multilocus sequence typing results of 91 representative isolates showed that the isolates can be divided into 74 sequences types (STs); 40.66% of the isolates can be included into seven clonal complexes (CCs). Although most of the isolates were classified as type A, considerable genetic diversity was observed, with the Simpson's diversity index of ST up to 0.9902. Some isolates from farm stage and slaughter stage were distributed in the same ST or CC, indicating that chicken products may be contaminated by the same ST or CC of C. perfringens originated from the farm stage. The high contamination rates of chicken products and the widespread multiple antibiotic resistance of isolates indicated potential public health risks, control measures at rearing and slaughtering stage should be considered to reduce this risk.

Prevalence of avian-origin mcr-1-positive Escherichia coli with a potential risk to humans in Tai'an, China

Multidrug-resistant (MDR) Escherichia coli are responsible for difficult-to-treat infections. We sought to determine the prevalence and characteristics of MDR E. coli strains isolated from poultry and clinical patients in the same geographical region. Eighty-seven E. coli strains were isolated from poultry with perihepatitis lesions at different slaughterhouses, and 356 nonrepetitive E. coli strains were isolated from clinical patients. All samples were continuously collected from October to December 2017 in Tai'an, China. The presence of the mcr-1 gene in the strains was assessed by PCR. The genetic relationships of the polymyxin (POL)-resistant E. coli strains were analyzed by pulsed-field gel electrophoresis and multilocus sequence typing. The results indicate that the POL resistance rate for the E. coli isolates from poultry was 31.03% (27 of 87), whereas the human-origin E. coli isolates were 100% sensitive to POL. The mcr-1 gene and extended-spectrum β-lactamase bla_CTX-M-14 genes were identified in all 27 POL-resistant avian-origin E. coli isolates. Our pulsed-field gel electrophoresis analysis suggested that the 27 strains were represented by 14 pulsotypes, among which there were 3 strains each with A, E, I, and K pulsotypes, and 1 to 2 strains represented by the other 10 pulsotypes. Furthermore, multilocus sequence typing molecular typing identified 16 sequence types, including 4 ST156 strains, 3 ST533 strains, and 1 to 2 strains represented by the remaining 14 sequence types. In summary, the E. coli strains isolated in the Tai'an area all showed the MDR phenotype, the rate of which for poultry was higher than that for humans. No POL-resistant human-origin E. coli strains were identified in the clinical patients. Our study reveals that poultry-derived MDR mcr-1-positive E. coli strains may pose a potential risk to humans, and the surveillance findings presented herein will be conducive to our understanding of the prevalence and characteristics of mcr-1-positive E. coli strains in the Tai'an area.