Diversity of Clostridium perfringens isolates from various sources and prevalence of conjugative plasmids

Molecular characteristics and phylogenetic analysis of Clostridium perfringens from different regions in China, from 2013 to 2021

Clostridium perfringens (C. perfringens) is a significant foodborne pathogen and a common cause of intestinal diseases in both animals and humans. Our study investigated MLST, phenotypic antimicrobial resistance profiles, and resistance genes among isolates from human, animal and food. 186 C. perfringens isolates were obtained from nine provinces in China between 2013 and 2021. Additionally, some specific ST complexes were analyzed by cgMLST and cgSNP to investigate genetic relatedness. MLST indicated the most prevalent STs of C. perfringens of human and animal origin were as follows: ST221 (5/147), ST62 (4/147), ST408 (4/147), and ST493 (4/147) were predominant in humans, while ST479 (5/25) was the major type in animals. Within the same ST complex, genetically unrelated relationships or potential clustering/transmission events were further recognized by cgMLST and cgSNP, illustrating that these two methods are valuable in defining outbreaks and transmission events. All tested isolates were susceptible to vancomycin and meropenem. The rates of resistance to metronidazole, penicillin, cefoxitin, moxifloxacin, and chloramphenicol were low (metronidazole: 1.08%; penicillin: 9.68%; cefoxitin: 0.54%; moxifloxacin: 6.45%; and chloramphenicol: 3.76%). Interestingly, 49.66% of human origin were clindamycin-resistant, and 18.2% were penicillin-insensitive. Importantly, the portion of MDR isolates was significantly lower than in previous reports. The study provides an overview of the epidemiological characteristics of C. perfringens with different origins and hosts in China. C. perfringens demonstrated remarkable genetic diversity and distinct molecular features compared to antibiotic-resistance profiles from other studies.

TMT labeled comparative proteomic analysis reveals spleen active immune responses during Clostridium perfringens type C infected piglet diarrhea

Background

Clostridium perfringens (C. perfringens) type C is the principal pathogenic clostridia of swine, frequently causing hemorrhagic diarrhea, even necrotic enteritis in piglets, leading to severe economic loss for swine industr ies worldwide. However, there are no specific and effective prevention measures. Therefore, clarifying the molecular mechanisms of hosts against pathogenesis infection is very important to reduce the incidence of C. perfringens type C infected piglet diarrhea disease.

Methods

We performed an TMT labeling-based quantitative spleen proteomic analysis of the control group (SC), tolerance group (SR) and susceptible group (SS) to identify the differentially expressed proteins (DEPs), and screened potential molecular markers of piglet spleen tissues in response to C. perfringens type C infection.

Results

In this study, a total of 115, 176 and 83 DEPs were identified in SR vs SC, SS vs SC, and SR vs SC, respectively, which may play the important regulatory roles in the process of piglet spleens in response toC. perfringens type C-infected diarrhea diseases. GO enrichment analysis revealed that the DEPs were mostly significantly enriched in acute inflammatory response, defense response, antimicrobial response, transporter activity, cellular metabolic process and so on, and KEGG pathway enrichment analysis showed that the significantly enriched immune related pathways of the PPAR signaling pathway, IL-17 signaling pathway, antigen processing and presentation, which hints at the immune defense process of piglet spleen against C. perfringens infection. This study helps to elucidate the protein expressional pattern of piglet spleen against C. perfringens type C-infected diarrhea disease, which can contribute to the prevention and control for pig diarrhea disease and the further development of diarrhea resistant pig breeding.

Tracing Clostridium perfringens strains from beef processing of slaughter house by pulsed-field gel electrophoresis, and the distribution and toxinotype of isolates in Shaanxi province, China

The purpose of this study was to investigate the distribution and specify the transmission and cross-contamination of Clostridium perfringens (C. perfringens) in the beef slaughtering and butchering process. The prevalence of 21.2% (150/708) yielded 208 isolates of C. perfringens, including 80.8% type A and 19.2% type D, 0.4% (3/708) samples carried both type A and D strains, and 72.5% type D isolates carried both cpe and atyp.cpb2 genes. C. perfringens were identified through the whole slaughtering process but no type F (cpe and cpa isolates) was found. 69 isolates were further analyzed and classified into 28 PFGE genotypes and clade I contained 94.2% isolates and 24 PFGE genotypes, which showed the genetic diversity and epidemic correlation. Our study traced C. perfringens contamination along the handling processes and showed a gradually ascending contamination rate during the whole process, revealing widespread cross-contamination from the feces and hides of slaughtered cattle to the carcass in the slaughtering workshop, so as from tools and personnel to meat of the cutting workshops. Strains from different slaughterhouses (regions) have high homology, and type A is the predominant toxinotype. It is necessary to monitor and control several key points of cross-contamination during slaughtering process to reduce a risk of C. perfringens infection.

Multilocus sequence typing of Clostridium perfringens strains from neonatal calves, dairy workers and associated environment in India

Clostridium perfringens is a globally recognized zoonotic pathogen. We report isolation and genotyping of C. perfringens from neonatal calves, dairy workers and their associated environment in India. A total of 103 fecal samples from neonatal calves, 25 stool swabs from the dairy workers and 50 samples from their associated environment were collected from two dairy farms. C. perfringens was detected in 26 out of 103 (25.2%) neonatal calf samples, 7 out of 25 (28%) human stool samples and 17 out of 50 (34%) environmental samples. C. perfringens type A strains were predominant in neonatal calves (24/26; 92.3%) and associated environment (15/17; 88.2%). In contrast, strains from dairy workers mostly belonged to type F (5/7; 71.4%), which also carried the beta2 toxin gene. Seventeen strains were analyzed by multilocus sequence typing (MLST) for studying genotypic relationship along with 188 C. perfringens strains available from public databases. A total of 112 sequence types (STs) were identified from 205 C. perfringens strains analyzed. A Clonal complex (CC) represented by three STs (ST 98, ST 41 and ST 110) representing predominantly type F (18/20 strains) were mostly associated with human illnesses. Among predominant STs, ST 54 was associated with enteritis cases in foals and dogs and ST 58 associated with necrotic enteritis in poultry. Seventeen Indian strains were assigned to 13 STs. Genetic relatedness among strains of calves, dairy worker and associated environments indicate inter-host transfers and zoonotic spreads.

Evidence for Infections by the Same Strain of Beta 2-toxigenic Clostridium perfringens Type A Acquired in One Hospital Ward

This study conducts a comparative phenotypic and genetic analysis of C. perfringens strains isolated from two patients hospitalized at the same time in 2017 in the surgical ward of the Provincial Specialist Hospital in Włocławek (Kujawsko-Pomorskie Province) who developed necrotizing soft tissue infections (NSTI). To explain the recurring cases of this infection, a comparative analysis was performed for these strains and the ones originating from infections recorded at the same hospital in three patients with gas gangrene in 2015. The two C. perfringens isolates studied in 2017 (8554/M/17 from patient No. 1 and 8567/M/17 from patient No. 2) had identical biochemical profiles. A comparison of research results using multiplex PCR from 2017 with a genetic analysis of strains from 2015 enabled us to demonstrate that the strains currently studied have the genes encoding the same toxins (α and β2) as the two strains analyzed in 2015: no. 7143 (patient No. 3) and no. 7149 (patient No. 2). A comparative analysis of the strain profiles obtained with pulsed-field gel electrophoresis (PFGE) in 2017 with the results from 2015 has found one identical and genetically unique restriction profile, corresponding to one clone of C. perfringens comprising of two strains: no. 8567/M/17 (patient No. 2 in 2017) and no. 7143 (patient No. 3 in 2015). The epidemiological data and detailed analysis of the course of both events suggest that this clone of C. perfringens possibly survived in adverse conditions of the external environment in the operating block of this hospital for many months.

Genomic analysis on broiler-associated Clostridium perfringens strains and exploratory caecal microbiome investigation reveals key factors linked to poultry necrotic enteritis

Background

Clostridium perfringens is a key pathogen in poultry-associated necrotic enteritis (NE). To date there are limited Whole Genome Sequencing based studies describing broiler-associated C. perfringens in healthy and diseased birds. Moreover, changes in the caecal microbiome during NE is currently not well characterised. Thus, the aim of this present study was to investigate C. perfringens virulence factors linked to health and diseased chickens, including identifying putative caecal microbiota signatures associated with NE.

Results

We analysed 88 broiler chicken C. perfringens genomes (representing 66 publicly available genomes and 22 newly sequenced genomes) using different phylogenomics approaches and identified a potential hypervirulent and globally-distributed clone spanning 20-year time-frame (1993-2013). These isolates harbored a greater number of virulence genes (including toxin and collagen adhesin genes) when compared to other isolates. Further genomic analysis indicated exclusive and overabundant presence of important NE-linked toxin genes including netB and tpeL in NE-associated broiler isolates. Secondary virulence genes including pfoA, cpb2, and collagen adhesin genes cna, cnaA and cnaD were also enriched in the NE-linked C. perfringens genomes. Moreover, an environmental isolate obtained from farm animal feeds was found to encode netB, suggesting potential reservoirs of NetB-positive C. perfringens strains (toxinotype G). We also analysed caecal samples from a small sub-set of 11 diseased and healthy broilers for exploratory microbiome investigation using 16S rRNA amplicon sequencing, which indicated a significant and positive correlation in genus Clostridium within the wider microbiota of those broilers diagnosed with NE, alongside reductions in beneficial microbiota members.

Conclusions

These data indicate a positive association of virulence genes including netB, pfoA, cpb2, tpeL and cna variants linked to NE-linked isolates. Potential global dissemination of specific hypervirulent lineage, coupled with distinctive microbiome profiles, highlights the need for further investigations, which will require a large worldwide sample collection from healthy and NE-associated birds.

Diversity of CRISPR/Cas system in Clostridium perfringens

Clostridium perfringens is an important pathogen of human and livestock infections, posing a threat to health. The horizontal gene transfer (HGT) of plasmids that carry toxin-related genes is involved in C. perfringens pathogenicity. The CRISPR/Cas system, which has been identified in a wide range of prokaryotes, provides acquired immunity against HGT. However, information about the CRISPR/Cas system in Clostridium perfringens is still limited. In this study, 111 C. perfringens strains with publicly available genomes were used to analyze the occurrence and diversity of CRISPR/Cas system and evaluate the potential of CRISPR-based genotyping in this multi-host pathogen. A total of 59 out of the 111 genomes harbored at least one confirmed CRISPR array. Four CRISPR/Cas system subtypes, including subtypes IB, IIA, IIC, and IIID systems, were identified in 32 strains. Subtype IB system was the most prevalent in this species, which was subdivided into four subgroups displaying subgroup specificity in terms of cas gene content, repeat sequence content, and PAM. We showed that the CRISPR spacer polymorphism can be used for evolutionary studies, and that it can provide discriminatory power for typing strains. Nevertheless, the application of this approach was largely limited to strains that contain the CRISPR/Cas system. Spacer origin analysis revealed that approximately one-fifth of spacers showed significant matches to plasmids and phages, thereby suggesting the implication of CRISPR/Cas systems in controlling HGT. Collectively, our results provide new insights into the diversity and evolution of CRISPR/Cas system in C. perfringens.

The prevalence of plasmid-coded cpe enterotoxin, β2 toxin, tpeL toxin, and tetracycline resistance in Clostridium perfringens strains isolated from different sources

Clostridium perfringens, an anaerobic, spore-forming bacterium, causes infections in humans and animals by producing several toxins encoded by genes found either on the chromosomes or on diverse plasmids. The plasmids may code for more than one toxin gene or antimicrobial-resistance gene. In this study, the prevalence of the β2, cpe and tpeL toxin genes and the tetA(P), tetB(P) and tetM tetracycline-resistance genes, in 56 strains of C. perfringens type A isolated from diseased domestic animals and 15 strains isolated from chickens, was compared with that in 74 strains isolated from other sources. The frequency of chromosome-associated cpe enterotoxin genes was higher in strains not isolated from diseased domestic animals; however, plasmid-associated cpe genes were found in strains from some animal sources more than others. Enterotoxin production was detected in some strains that had chromosomal or plasmid cpe genes, but not in all. The percentages of strains carrying β2 toxin genes among chicken, swine, human patient and soil isolates were higher than those among bovine, canine and food isolates. The incidence of the tpeL toxin gene was lower than that of the β2 gene. Phenotypic resistance to tetracycline was found in more than 50% of the porcine, bovine, and canine isolates, which carried a wide range of plasmids of 2-100 kb size, most of which had the tcpH clostridial transfer gene. PCR amplified tetA(P) and tetB(P) genes from most isolates from diseased animals. Some strains that carried <40 kb plasmids and had the tcpH gene also had one or more toxin genes or tetracycline-resistance gene. This study shows that the prevalence of plasmid-borne toxins and antimicrobial resistance genes varied among C. perfringens strains isolated from different sources. Plasmids of smaller size than those previously reported in strains of C. perfringens type A may also harbor toxin genes and antimicrobial-resistance genes.

Prevalence, toxin gene profile, antibiotic resistance, and molecular characterization of Clostridium perfringens from diarrheic and non-diarrheic dogs in Korea

Clostridium perfringens causes diarrhea and other diseases in animals and humans. We investigated the prevalence, toxin gene profiles, and antibiotic resistance of C. perfringens isolated from diarrheic dogs (DD) and non-diarrheic dogs (ND) in two animal hospitals in Seoul, Korea. Fecal samples were collected from clinically DD (n = 49) and ND (n = 34). C. perfringens was isolated from 31 of 49 DD (63.3%) and 21 of 34 ND dogs (61.8%). All C. perfringens strains were positive for the α toxin gene, but not for the β, ε, or ι toxin genes; therefore, all strains were identified as type A C. perfringens. All isolates were cpe-negative, whereas the β2 toxin gene was identified in 83.9% and 61.9% of isolates from DD and ND, respectively. Most isolates were susceptible to ampicillin (94%), chloramphenicol (92%), metronidazole (100%), moxifloxacin (96%), and imipenem (100%). However, 25.0% and 21.2% of isolates were resistant to tetracycline and clindamycin, respectively. Molecular subtyping of the isolated strains was performed by using pulsed-field gel electrophoresis. Fifty-two isolates were classified into 48 pulsotypes based on more than 90% similarity of banding patterns. No notable differences were observed among the isolates from DD and ND.

Pulsed-field gel electrophoresis of enterotoxic Clostridium perfringens type A isolates recovered from humans and animals in Kolkata, India

Clostridium perfringens is one of the most important globally recognised gastroenteric pathogen in humans as well as animals. The present study was aimed to know the similarities/divergence among C. perfringens type A isolates of human and animal origin using the pulsed-field gel electrophoresis (PFGE) as a molecular tool. The enterotoxic isolates obtained by screening of human diarrhoeal cases (n = 130), diarrhoeal cases of pig (n = 52) and goat (n = 50), meat samples viz., pork (n = 59) and chevon (n = 57) were characterized by standard cultural and biochemical methods followed by PCR Assays. Accordingly, a total of 11 C. perfringens type A characterized isolates (16S rRNA+, cpa+, cpb2+ and cpe+) recovered from human diarrhoeal cases (n = 3); diarrhoeal cases of pig (n = 2) and goat (n = 2); meat samples viz. pork (n = 2) and chevon (n = 2) were examined employing PFGE. The observed clustering pattern in PFGE analysis showed the relatedness between isolates from diarrhoeal goat and chevon (90-100%); diarrhoeal pig and pork (65-68%); moreover, isolates from human diarrhoeal cases were exhibiting lineage to cases from goat and pig diarrhoea as well pork and chevon by 62-68% relatedness. The outcome of the present study indicates the probable contamination of this pathogen to the human food chain through faeces from suspected food animals viz. goat and pig and their improperly cooked meat.

Effects of Bile Acids and Nisin on the Production of Enterotoxin by Clostridium perfringens in a Nutrient-Rich Medium

Clostridium perfringens is the second most common cause of bacterial foodborne illness in the United States, with nearly a million cases each year. C. perfringens enterotoxin (CPE), produced during sporulation, damages intestinal epithelial cells by pore formation, which results in watery diarrhea. The effects of low concentrations of nisin and bile acids on sporulation and toxin production were investigated in C. perfringens SM101, which carries an enterotoxin gene on the chromosome, in a nutrient-rich medium. Bile acids and nisin increased production of enterotoxin in cultures; bile acids had the highest effect. Both compounds stimulated the transcription of enterotoxin and sporulation-related genes and production of spores during the early growth phase. They also delayed spore outgrowth and nisin was more inhibitory. Bile acids and nisin enhanced enterotoxin production in some but not all other C. perfringens isolates tested. Low concentrations of bile acids and nisin may act as a stress signal for the initiation of sporulation and the early transcription of sporulation-related genes in some strains of C. perfringens, which may result in increased strain-specific production of enterotoxin in those strains. This is the first report showing that nisin and bile acids stimulated the transcription of enterotoxin and sporulation-related genes in a nutrient-rich bacterial culture medium.

Probing Genomic Aspects of the Multi-Host Pathogen Clostridium perfringens Reveals Significant Pangenome Diversity, and a Diverse Array of Virulence Factors

Clostridium perfringens is an important cause of animal and human infections, however information about the genetic makeup of this pathogenic bacterium is currently limited. In this study, we sought to understand and characterise the genomic variation, pangenomic diversity, and key virulence traits of 56 C. perfringens strains which included 51 public, and 5 newly sequenced and annotated genomes using Whole Genome Sequencing. Our investigation revealed that C. perfringens has an "open" pangenome comprising 11667 genes and 12.6% of core genes, identified as the most divergent single-species Gram-positive bacterial pangenome currently reported. Our computational analyses also defined C. perfringens phylogeny (16S rRNA gene) in relation to some 25 Clostridium species, with C. baratii and C. sardiniense determined to be the closest relatives. Profiling virulence-associated factors confirmed presence of well-characterised C. perfringens-associated exotoxins genes including α-toxin (plc), enterotoxin (cpe), and Perfringolysin O (pfo or pfoA), although interestingly there did not appear to be a close correlation with encoded toxin type and disease phenotype. Furthermore, genomic analysis indicated significant horizontal gene transfer events as defined by presence of prophage genomes, and notably absence of CRISPR defence systems in >70% (40/56) of the strains. In relation to antimicrobial resistance mechanisms, tetracycline resistance genes (tet) and anti-defensins genes (mprF) were consistently detected in silico (tet: 75%; mprF: 100%). However, pre-antibiotic era strain genomes did not encode for tet, thus implying antimicrobial selective pressures in C. perfringens evolutionary history over the past 80 years. This study provides new genomic understanding of this genetically divergent multi-host bacterium, and further expands our knowledge on this medically and veterinary important pathogen.

Impact of pre-application treatment on municipal sludge composition, soil dynamics of antibiotic resistance genes, and abundance of antibiotic-resistance genes on vegetables at harvest

In many jurisdictions sludge recovered from the sewage treatment process is a valued fertilizer for crop production. Pre-treatment of sewage sludge prior to land application offers the potential to abate enteric microorganisms that carry genes conferring resistance to antibiotics. Pre-treatment practices that accomplish this should have the desirable effect of reducing the risk of contamination of crops or adjacent water with antibiotic resistance genes carried in these materials. In the present study, we obtained municipal sludge that had been subjected to one of five treatments. There were, anaerobic-digestion or aerobic-digestion, in both instances with and without dewatering; and heat-treatment and pelletization. Each of the five types of biosolids was applied to an agricultural field at commercial rates, following which lettuce, carrots and radishes were planted. Based on qPCR, the estimated antibiotic gene loading rates were comparable with each of the five biosolids. However, the gene abundance in soil following application of the pelletized biosolids was anomalously lower than expected. Following application, the abundance of antibiotic resistance genes decreased in a generally coherent fashion, except sul1 which increased in abundance during the growing season in the soil fertilized with pelletized biosolids. Based on qPCR and high throughput sequencing evidence for transfer of antibiotic resistance genes from the biosolids to the vegetables at harvest was weak. Clostridia were more abundant in soils receiving any of the biosolids except the pelletized. Overall, the behavior of antibiotic resistance genes in soils receiving aerobically or anaerobically-digested biosolids was consistent and coherent with previous studies. However, dynamics of antibiotic resistance genes in soils receiving the heat treated pelletized biosolids were very different, and the underlying mechanisms merit investigation.

Isolation of Clostridium perfringens type A from wild bharals (Pseudois nayaur) following sudden death in Tibet, China

Dozens of wild bharals died suddenly in Tibet. Necropsy showed severe congestion and hemorrhage in multiple organs, with large numbers of Gram-positive bacilli. Strains of Clostridium perfringens type A were isolated from the different organs and the intestinal contents. The other possible pathogens were ruled out by PCR.

Acinetobacter lactucae sp. nov., isolated from iceberg lettuce (Asteraceae: Lactuca sativa)

Strain NRRL B-41902T and three closely related strains were isolated from iceberg lettuce. The strain was found to consist of strictly aerobic, Gram-stain-negative rods that formed cocci in late stationary phase. 16S rRNA gene sequence analysis showed that strain NRRL B-41902T was most closely related to species within the genera Acinetobacter, and that a grouping of it and the three other closely related strains was most closely related to the type strain of Acinetobacter pittii, which was also confirmed through a phylogenomic analysis. Moreover, in silico DNA-DNA hybridization analysis revealed a substantial amount of genomic divergence (39.1 %) between strain NRRL B-41902T and the type strain of A. pittii, which is expected if the strains represent distinct species. Further phenotypic analysis revealed that strain NRRL B-41902T was able to utilize a combination of l-serine, citraconic acid and citramalic acid, which differentiated it from other, closely related Acinetobacter species. Therefore, strain NRRL B-41902T (=CCUG 68785T) is proposed as the type strain of a novel species, Acinetobacter lactucae sp. nov.