butyricum type E toxin: a novel environmental association with pet terrapins

Infant Botulism: In Search of Clostridium botulinum Spores

Infant botulism is now the most common form of human botulism in Canada and the United States. Infant botulism is a severe neuroparalytic disease caused by ingestion of the spore-forming neurotoxic clostridia, including Clostridium botulinum that colonize the large intestine and subsequently produce botulinum neurotoxin in situ. It has been over a century since the first surveys documenting the ubiquitous prevalence of C. botulinum in soils around the world. Since then, honey has been identified as the only well-known risk factor for infant botulism despite a multitude of international environmental surveys isolating C. botulinum spores from ground soil, aquatic sediments, and commonly available infant foods. Associations of infant botulism cases with confirmed sources of C. botulinum exposure have primarily implicated outdoor soil and indoor dust, as well as commonly ingested foods including honey, dry cereals, and even powdered infant formula. Yet the origin of infection remains unknown for most infant botulism cases. This review summarizes the various surveys from around the world for C. botulinum in environmental soils and sediments, honey, and other infant foods, as well as laboratory-confirmed associations with documented infant botulism cases. Additional factors are also discussed, including the composition of infant gut microbiota and the practice of breastfeeding. We make several recommendations to better identify sources of exposure to C. botulinum spores that could lead to effective preventive measures and help reduce the incidence of this rare but life-threatening disease.

Probiotic-related Clostridium butyricum bacteremia: a case report and literature review

We report three cases of Clostridium butyricum bacteremia associated with taking C. butyricum-related probiotics. We performed a literature review and found 11 cases of C. butyricum bacteremia including our cases. Nine cases related to probiotics. We should consider that probiotics may infect clinically unstable patients.

Duration of Fecal Excretion of Clostridium Botulinum and Botulinum Neurotoxin in Patients Recovering from Infant Botulism

This study sought to determine duration of fecal excretion of Clostridium botulinum organisms and neurotoxin after onset of infant botulism in 66 affected infants. Median excretion was longer for type A than type B patients (organisms: 5.9 vs 3.5 weeks, toxin: 4.8 vs 1.6 weeks, respectively). Toxin excretion always ceased before organism excretion. Antibiotic therapy did not affect duration of excretion.

Genomic and Phenotypic Characterization of Clostridium botulinum Isolates from an Infant Botulism Case Suggests Adaptation Signatures to the Gut

In early life, the immature human gut microbiota is prone to colonization by pathogens that are usually outcompeted by mature microbiota in the adult gut. Colonization and neurotoxin production by a vegetative Clostridium botulinum culture in the gut of an infant can lead to flaccid paralysis, resulting in a clinical outcome known as infant botulism, a potentially life-threatening condition. Beside host factors, little is known of the ecology, colonization, and adaptation of C. botulinum to the gut environment. In our previous report, an infant with intestinal botulism was shown to be colonized by neurotoxigenic C. botulinum culture for 7 months. In an effort to gain ecological and evolutionary insights into this unusually long gut colonization by C. botulinum, we analyzed and compared the genomes of C. botulinum isolates recovered from the infant feces during the course of intoxication and isolates from the infant household dust. A number of observed mutations and genomic alterations pinpointed at phenotypic traits that may have promoted colonization and adaptation to the gut environment and to the host. These traits include motility, quorum-sensing, sporulation, and carbohydrate metabolism. We provide novel perspectives and suggest a tentative model of the pathogenesis of C. botulinum in infant botulism.

Novel Putative Transposable Element Associated with the Subtype E5 Botulinum Toxin Gene Cluster of Neurotoxigenic Clostridium butyricum Type E Strains from China

Previously, a whole-genome comparison of three Clostridium butyricum type E strains from Italy and the United States with different C. botulinum type E strains indicated that the bont/e gene might be transferred between the two clostridia species through transposition. However, transposable elements (TEs) have never been identified close to the bont/e gene. Herein, we report the whole genome sequences for four neurotoxigenic C. butyricum type E strains that originated in China. An analysis of the obtained genome sequences revealed the presence of a novel putative TE upstream of the bont/e gene in the genome of all four strains. Two strains of environmental origin possessed an additional copy of the putative TE in their megaplasmid. Similar putative TEs were found in the megaplasmids and, less frequently, in the chromosomes of several C. butyricum strains, of which two were neurotoxigenic C. butyricum type E strains, and in the chromosome of a single C. botulinum type E strain. We speculate that the putative TE might potentially transpose the bont/e gene at the intracellular and inter-cellular levels. However, the occasional TE occurrence in the clostridia genomes might reflect rare transposition events.

Infant Botulism: Checklist for Timely Clinical Diagnosis and New Possible Risk Factors Originated from a Case Report and Literature Review

Infant botulism is a rare and underdiagnosed disease caused by BoNT-producing clostridia that can temporarily colonize the intestinal lumen of infants less than one year of age. The diagnosis may be challenging because of its rareness, especially in patients showing atypical presentations or concomitant coinfections. In this paper, we report the first infant botulism case associated with Cytomegalovirus coinfection and transient hypogammaglobulinemia and discuss the meaning of these associations in terms of risk factors. Intending to help physicians perform the diagnosis, we also propose a practical clinical and diagnostic criteria checklist based on the revision of the literature.

Descriptive Epidemiology of Infant Botulism in California: The First 40 Years

OBJECTIVE

To ascertain the descriptive epidemiology of infant botulism, the flaccid paralysis that results when neurotoxigenic Clostridium species produce botulinum toxin (BoNT) in the infant colon, in its first 40 years following initial recognition in California in 1976.

STUDY DESIGN

Cases were defined by laboratory identification of BoNT and/or neurotoxigenic Clostridium species in patients' feces. Parents were interviewed using a structured questionnaire. Descriptive epidemiologic characteristics were compared between 1976-1996 and 1997-2016.

RESULTS

From 1976-2016, 1345 cases of infant botulism occurred in 45 of 58 California counties (6.5 cases/100 000 live-births/year) caused by BoNT types A, B, Ba, Bf, and F; 88% of cases were ≤6 months of age and 51% were female. Cases were white (84.2%), Asian (8.9%), other races (3.8%), and African American (2.8%); 29.4% of cases were Hispanic. More than 99% of cases were hospitalized. Case occurrence peaked in summer-fall. Of 8 designated geographic regions, the Central Coast counties had 3 times the statewide incidence in both 20-year time periods. Breast-fed patients (83%) were more than twice as old at onset as formula-fed patients (median, 4.4 vs 1.7 months, respectively; P < .001). BoNT/A cases were older at onset than BoNT/B cases (median, 3.8 vs 2.9 months, respectively; P < .001).

CONCLUSIONS

Comprehensive continuous surveillance of infant botulism for 40 years in a large, diversely populated state identified fundamental epidemiologic characteristics of this uncommon illness. Unusual features included greater than 99% case hospitalization, absence of male preponderance, and a distinctive age distribution.

Establishment and evaluation of a method for efficient screening of Clostridium butyricum

At present, the traditional methods for the screening of Clostridium butyricum are not sufficiently selective and efficient. Therefore, it is necessary to establish a targeted and efficient screening method for the detection of C. butyricum. Bioinformatics was used in this study to find C. butyricum specific genes, and species-specific primers were designed based on the conserved regions of the targeted genes, followed by optimization of the PCR conditions. Methodological evaluation was carried out, and the results were compared with the traditional screening method based on Trypticase Sulfite Neomycin (TSN) selective medium. A high-efficiency PCR screening method, targeting C. butyricum species-specific primers, was established. The method was confirmed to have high specificity and sensitivity towards C. butyricum cut-off CFU 10³. Compared with the traditional method, the screening success rate of C. butyricum strains increased from 0.61 to 81.91%. The PCR screening method could quickly and accurately detect C. butyricum in samples and dramatically improve screening efficiency.

Public Health Risk Associated with Botulism as Foodborne Zoonoses

Botulism is a rare but severe neurological disease in man and animals that is caused by botulinum neurotoxins (BoNTs) produced by Clostridium botulinum and atypical strains from other Clostridium and non-Clostridium species. BoNTs are divided into more than seven toxinotypes based on neutralization with specific corresponding antisera, and each toxinotype is subdivided into subtypes according to amino acid sequence variations. Animal species show variable sensitivity to the different BoNT toxinotypes. Thereby, naturally acquired animal botulism is mainly due to BoNT/C, D and the mosaic variants CD and DC, BoNT/CD being more prevalent in birds and BoNT/DC in cattle, whereas human botulism is more frequently in the types A, B and E, and to a lower extent, F. Botulism is not a contagious disease, since there is no direct transmission from diseased animals or man to a healthy subject. Botulism occurs via the environment, notably from food contaminated with C. botulinum spores and preserved in conditions favorable for C. botulinum growth and toxin production. The high prevalence of botulism types C, D and variants DC and CD in farmed and wild birds, and to a lower extent in cattle, raises the risk of transmission to human beings. However, human botulism is much rarer than animal botulism, and botulism types C and D are exceptional in humans. Only 15 cases or suspected cases of botulism type C and one outbreak of botulism type D have been reported in humans to date. In contrast, animal healthy carriers of C. botulinum group II, such as C. botulinum type E in fish of the northern hemisphere, and C. botulinum B4 in pigs, represent a more prevalent risk of botulism transmission to human subjects. Less common botulism types in animals but at risk of transmission to humans, can sporadically be observed, such as botulism type E in farmed chickens in France (1998-2002), botulism type B in cattle in The Netherlands (1977-1979), botulism types A and B in horses, or botulism type A in dairy cows (Egypt, 1976). In most cases, human and animal botulisms have distinct origins, and cross transmissions between animals and human beings are rather rare, accidental events. But, due to the severity of this disease, human and animal botulism requires a careful surveillance.

Type F Infant Botulism: Investigation of Recent Clusters and Overview of This Exceedingly Rare Disease

From 1976 to 2016, neurotoxigenic Clostridium baratii type F caused 18 (<0.5%) reported US infant botulism cases. Six cases occurred during 2012-2013; no common source was identified. Type F infant botulism mostly occurs in very young infants and typically presents more rapidly and severely than illness caused by types A and B botulinum neurotoxin.

Type E Botulinum Neurotoxin-Producing Clostridium butyricum Strains Are Aerotolerant during Vegetative Growth

Botulinum neurotoxins, the causative agents of the potentially fatal disease of botulism, are produced by certain Clostridium strains during vegetative growth, usually in anaerobic environments. Our findings indicate that, contrary to current understanding, the growth of neurotoxigenic C. butyricum strains and botulinum neurotoxin type E production can continue upon transfer from anaerobic to aerated conditions and that adaptation of strains to oxygenated environments requires global changes in proteomic and metabolic profiles. We hypothesize that aerotolerance might constitute an unappreciated factor conferring physiological advantages on some botulinum toxin-producing clostridial strains, allowing them to adapt to otherwise restrictive environments.

Clostridium butyricum, the type species of the genus Clostridium, is considered an obligate anaerobe, yet it has been shown to grow in the presence of oxygen. C. butyricum strains atypically producing the botulinum neurotoxin type E are the leading cause of type E human botulism in Italy. Here, we show that type E botulinum neurotoxin-producing C. butyricum strains growing exponentially were able to keep growing and producing toxin in vitro upon exposure to air, although less efficiently than under ideal oxygen-depleted conditions. Bacterial growth in air was maintained when the initial cell density was higher than 10³ cells/ml. No spores were detected in the cultures aerated for 5 h. To understand the biological mechanisms allowing the adaptation of vegetative cells of C. butyricum type E to oxygen, we compared the proteome and metabolome profiles of the clostridial cultures grown for 5 h under either aerated or anaerobic conditions. The results indicated that bacterial cells responded to oxygen stress by slowing growth and modulating the expression of proteins involved in carbohydrate uptake and metabolism, redox homeostasis, DNA damage response, and bacterial motility. Moreover, the ratio of acetate to butyrate was significantly higher under aeration. This study demonstrates for the first time that a botulinum neurotoxin-producing Clostridium can withstand oxygen during vegetative growth.

IMPORTANCE Botulinum neurotoxins, the causative agents of the potentially fatal disease of botulism, are produced by certain Clostridium strains during vegetative growth, usually in anaerobic environments. Our findings indicate that, contrary to current understanding, the growth of neurotoxigenic C. butyricum strains and botulinum neurotoxin type E production can continue upon transfer from anaerobic to aerated conditions and that adaptation of strains to oxygenated environments requires global changes in proteomic and metabolic profiles. We hypothesize that aerotolerance might constitute an unappreciated factor conferring physiological advantages on some botulinum toxin-producing clostridial strains, allowing them to adapt to otherwise restrictive environments.

Clostridia and necrotizing enterocolitis in preterm neonates

Necrotizing enterocolitis (NEC) is the most severe life threatening gastrointestinal disease among preterm neonates. NEC continues to account for substantial morbidity and mortality in neonatal intensive care units worldwide. Although its pathogenesis remains incompletely elucidated, NEC is recognized as a multifactorial disease involving intestinal unbalanced inflammatory response, feeding strategies, and bacterial colonization. Epidemiological studies, clinical signs, and animal models support the participation of anaerobic bacteria, particularly clostridia species, in NEC development. Colonization by clostridia seems particularly deleterious. The present review is the opportunity to propose an update on the role of clostridia and NEC.

Development of immunodetection system for botulinum neurotoxin serotype E

Background & objectives

Botulism, a potentially fatal paralytic illness, is caused by the botulinum neurotoxins (BoNTs) secreted by Clostridium botulinum. It is an obligate anaerobic, Gram-positive, spore-forming bacterium. BoNTs are classified into seven serotypes based on the serological properties. Among these seven serotypes, A, B, E and, rarely, F are responsible for human botulism. The present study was undertaken to develop an enzyme-linked immunosorbent assay (ELISA)-based detection system for the detection of BoNT/E.

Methods

The synthetic gene coding the light chain of BoNT serotype E (BoNT/E LC) was constructed using the polymerase chain reaction primer overlapping method, cloned into pQE30UA vector and then transformed into Escherichia coli M15 host cells. Recombinant protein expression was optimized using different concentrations of isopropyl-β-D-1-thiogalactopyranoside (IPTG), different temperature and the rBoNT/E LC protein was purified in native conditions using affinity column chromatography. The purified recombinant protein was checked by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and further confirmed by western blot and matrix-assisted laser desorption ionization-tandem time-of-flight (MALDI-TOF). Polyclonal antibodies were generated against rBoNT/E LC using Freund's adjuvant in BALB/c mice and rabbit. Sandwich ELISA was optimized for the detection of rBoNT/E LC and native crude BoNT/E, and food matrix interference was tested. The developed antibodies were further evaluated for their specificity/cross-reactivity with BoNT serotypes and other bacterial toxins.

Results

BoNT/E LC was successfully cloned, and the maximum expression was achieved in 16 h of post-induction using 0.5 mM IPTG concentration at 25°C. Polyclonal antibodies were generated in BALB/c mice and rabbit and the antibody titre was raised up to 128,000 after the 2^nd booster dose. The developed polyclonal antibodies were highly specific and sensitive with a detection limit about 50 ng/ml for rBoNT/E LC and 2.5×10^[3] MLD₅₀ of native crude BoNT/E at a dilution of 1:3000 of mouse (capturing) and rabbit (revealing) antibodies. Further, different liquid, semisolid and solid food matrices were tested, and rBoNT/E LC was detected in almost all food samples, but different levels of interference were detected in different food matrices.

Interpretation & conclusions

There is no immune detection system available commercially in India to detect botulism. The developed system might be useful for the detection of botulinum toxin in food and clinical samples. Further work is in progress.

Infant botulism: Two case reports and electroneuromyogram findings

Botulism is an uncommon severe neuromuscular disorder. We report two recent cases of confirmed infant botulism diagnosed in an 11-week and a 5-month-old infant along with electroneuromyogram (ENMG) findings. Then, we discuss the EMG features of infant botulism. In severe forms of infant botulism, presence of these features might help decide to use botulinum immune globulin. To our knowledge, case 1 is the first case reported in France based on confirmed dust contamination.

Effects of Megaplasmid Loss on Growth of Neurotoxigenic Clostridium butyricum Strains and Botulinum Neurotoxin Type E Expression

Clostridium butyricum strains that atypically produce the botulinum neurotoxin type E (BoNT/E) possess a megaplasmid of unknown functions in their genome. In this study, we cured two botulinum neurotoxigenic C. butyricum type E strains of their megaplasmids, and compared the obtained megaplasmid-cured strains to their respective wild-type parental strains. Our results showed that the megaplasmids do not confer beta-lactam resistance on the neurotoxigenic C. butyricum type E strains, although they carry several putative beta-lactamase genes. Instead, we found that the megaplasmids are essential for growth of the neurotoxigenic C. butyricum type E strains at the relatively low temperature of 15°C, and are also relevant for growth of strains under limiting pH and salinity conditions, as well as under favorable environmental conditions. Moreover, the presence of the megaplasmids was associated with increased transcript levels of the gene encoding BoNT/E in the C. butyricum type E strains, indicating that the megaplasmids likely contain transcriptional regulators. However, the levels of BoNT/E in the supernatants of the cured and uncured strains were similar after 24 and 48 h culture, suggesting that expression of BoNT/E in the C. butyricum type E strains is not ultimately controlled by the megaplasmids. Together, our results reveal that the C. butyricum type E megaplasmids exert pleiotropic effects on the growth of their microbial hosts under optimal and limiting environmental conditions, and also highlight the possibility of original regulatory mechanisms controlling the expression of BoNT/E.

Laboratory Investigation of the First Case of Botulism Caused by Clostridium butyricum Type E Toxin in the United States

We report here the laboratory investigation of the first known case of botulism in the United States caused by Clostridium butyricum type E. This investigation demonstrates the importance of extensive microbiological examination of specimens, which resulted in the isolation of this organism.

Genomic Epidemiology of Clostridium botulinum Isolates from Temporally Related Cases of Infant Botulism in New South Wales, Australia

Infant botulism is a potentially life-threatening paralytic disease that can be associated with prolonged morbidity if not rapidly diagnosed and treated. Four infants were diagnosed and treated for infant botulism in NSW, Australia, between May 2011 and August 2013. Despite the temporal relationship between the cases, there was no close geographical clustering or other epidemiological links. Clostridium botulinum isolates, three of which produced botulism neurotoxin serotype A (BoNT/A) and one BoNT serotype B (BoNT/B), were characterized using whole-genome sequencing (WGS). In silico multilocus sequence typing (MLST) found that two of the BoNT/A-producing isolates shared an identical novel sequence type, ST84. The other two isolates were single-locus variants of this sequence type (ST85 and ST86). All BoNT/A-producing isolates contained the same chromosomally integrated BoNT/A2 neurotoxin gene cluster. The BoNT/B-producing isolate carried a single plasmid-borne bont/B gene cluster, encoding BoNT subtype B6. Single nucleotide polymorphism (SNP)-based typing results corresponded well with MLST; however, the extra resolution provided by the whole-genome SNP comparisons showed that the isolates differed from each other by >3,500 SNPs. WGS analyses indicated that the four infant botulism cases were caused by genomically distinct strains of C. botulinum that were unlikely to have originated from a common environmental source. The isolates did, however, cluster together, compared with international isolates, suggesting that C. botulinum from environmental reservoirs throughout NSW have descended from a common ancestor. Analyses showed that the high resolution of WGS provided important phylogenetic information that would not be captured by standard seven-loci MLST.