Characterization of a neurotoxigenic Clostridium butyricum strain isolated from the food implicated in an outbreak of food-borne type E botulism

A Family Outbreak of Type E Botulism Caused by Contaminated Vacuum-Packed Ambient-Stored Chili Chicken Feet in Zhangjiakou, China

The epidemiological investigation and laboratory-based confirmation were performed on samples from a family botulism outbreak in Zhangjiakou, Hebei province, China. Forty-four samples, including 14 samples (leftover food, and swabs taken of both food packaging bags and dishes, and serum and vomitus of the victims) related to outbreak and 30 causative food products after outbreak, were collected and analyzed. Isolation, bacterial identification, toxin detection, and whole-genome sequencing of Clostridium spp. cultured from the latter samples and animal assays were performed. Mice injected with the cultures of the leftover chili chicken feet, together with the inner layer of its packaging bag, the plate for serving it, and supernatant of two patients' serum that demonstrated the typical signs of botulism. The polyvalent anti-botulinum neurotoxin (BoNT) and the monovalent anti-BoNT/E exhibited protective effects when administered to mice. Three Clostridium botulinum cultures were obtained and verified to be positive for BoNT/E. The whole genome analysis of the isolates revealed that the classic bont/e gene orfX cluster was found to be located on the chromosomes of all three isolates. Single nucleotide polymorphism analysis suggested that these might be from the same source. Our findings indicated that this botulism outbreak occurred following the ingestion of vacuum-packed chili chicken feet contaminated with BoNT/E produced by C. botulinum.

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.

Botulism outbreak in a rural Ethiopia: a case series

BACKGROUND

Foodborne botulism, a toxin-mediated illness caused by Clostridium botulinum, is a public health emergency. Types A, B, and E C. botulinum toxins commonly cause human disease. Outbreaks are often associated with homemade and fermented foods. Botulism is rarely reported in Africa and has never been reported in Ethiopia.

CASE PRESENTATION

In March 2015, a cluster of family members from the Wollega, Oromia region, western Ethiopia presented with a symptom constellation suggestive of probable botulism. Clinical examination, epidemiologic investigation, and subsequent laboratory work identified the cause of the outbreak to be accidental ingestion of botulinum toxin in a traditional chili condiment called "Kochi-kocha," cheese, and clarified butter. Ten out of the fourteen family members who consumed the contaminated products had botulism (attack rate 71.4%) and five died (case fatality rate of 50%). Three of the patients were hospitalized, they presented with altered mental status (n = 2), profound neck and truncal weakness (n = 3), and intact extremity strength despite hyporeflexia (n = 3). The remnant food sample showed botulinum toxin type A with mouse bioassay and C. botulinum type A with culture. Blood drawn on day three of illness from 2/3 (66%) cases was positive for botulinum toxin type-A. Additionally, one of these two cases also had C. botulinum type A cultured from a stool specimen. Two of the cases received Botulism antitoxin (BAT).

CONCLUSION

These are the first confirmed cases of botulism in Ethiopia. The disease occurred due to the consumption of commonly consumed homemade foods. Definite diagnoses of botulism cases are challenging, and detailed epidemiologic and laboratory investigations were critical to the identification of this case series. Improved awareness of botulism risk and improved food preparation and storage may prevent future illnesses. The mortality rate of botulism in resource-limited settings remains high. Countries should make a concerted effort to stockpile antitoxin as that is the easiest and quickest intervention after outbreak detection.

Identity and hydrocarbon degradation activity of enriched microorganisms from natural oil and asphalt seeps in the Kurdistan Region of Iraq (KRI)

A previous cultivation-independent investigation of the microbial community structure of natural oil and asphalt seeps in the Kurdistan Region of Iraq (KRI) revealed the dominance of uncultured bacterial taxa belonging to the phyla Deferribacterota and Coprothermobacterota and the orders Thermodesulfobacteriales, Thermales, and Burkholderiales. Here we report on a cultivation-dependent approach to identify members of these groups involved in hydrocarbon degradation in the KRI oil and asphalt seeps. For this purpose, we set up anoxic crude oil-degrading enrichment cultures based on cultivation media known to support the growth of members of the above-mentioned taxonomic groups. During 100-200 days incubation periods, nitrate-reducing and fermentative enrichments showed up to 90% degradation of C₈-C₁₇ alkanes and up to 28% degradation of C₁₈-C₃₃ alkanes along with aromatic hydrocarbons. Community profiling of the enrichment cultures showed that they were dominated by diverse bacterial taxa, which were rare in situ community members in the investigated seeps. Groups initially targeted by our approach were not enriched, possibly because their members are slow-growing and involved in the degradation of recalcitrant hydrocarbons. Nevertheless, the enriched taxa were taxonomically related to phylotypes recovered from hydrocarbon-impacted environments as well as to characterized bacterial isolates not previously known to be involved in hydrocarbon degradation. Marker genes (assA and bssA), diagnostic for fumarate addition-based anaerobic hydrocarbon degradation, were not detectable in the enrichment cultures by PCR. We conclude that hydrocarbon biodegradation in our enrichments occurred via unknown pathways and synergistic interactions among the enriched taxa. We suggest, that although not representing abundant populations in situ, studies of the cultured close relatives of these taxa will reveal an unrecognized potential for anaerobic hydrocarbon degradation, possibly involving poorly characterized mechanisms.

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 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.

A Three Monoclonal Antibody Combination Potently Neutralizes Multiple Botulinum Neurotoxin Serotype E Subtypes

Human botulism is most commonly caused by botulinum neurotoxin (BoNT) serotypes A, B, and E. For this work, we sought to develop a human monoclonal antibody (mAb)-based antitoxin capable of binding and neutralizing multiple subtypes of BoNT/E. Libraries of yeast-displayed single chain Fv (scFv) antibodies were created from the heavy and light chain variable region genes of humans immunized with pentavalent-toxoid- and BoNT/E-binding scFv isolated by Fluorescence-Activated Cell Sorting (FACS). A total of 10 scFv were isolated that bound one or more BoNT/E subtypes with nanomolar-level equilibrium dissociation constants (K_D). By diversifying the V-regions of the lead mAbs and selecting for cross-reactivity, we generated three scFv that bound all four BoNT/E subtypes tested at three non-overlapping epitopes. The scFvs were converted to IgG that had K_D values for the different BoNT/E subtypes ranging from 9.7 nM to 2.28 pM. An equimolar combination of the three mAbs was able to potently neutralize BoNT/E1, BoNT/E3, and BoNT/E4 in a mouse neutralization assay. The mAbs have potential utility as therapeutics and as diagnostics capable of recognizing multiple BoNT/E subtypes. A derivative of the three-antibody combination (NTM-1633) is in pre-clinical development with an investigational new drug (IND) application filing expected in 2018.

Necrotizing enterocolitis associated with Clostridium butyricum in a Japanese man

Case

Necrotizing enterocolitis (NEC) caused by Clostridium butyricum is common in neonates; however, a case of NEC in adults has not been previously reported. An 84‐year‐old Japanese man developed C. butyricum‐related NEC during hospitalization for treatment of stab wounds to the left side of the neck and lower abdomen, without organ damage, and concomitant pneumonia.

Outcome

The patient developed acute onset of emesis accompanied by shock during his admission; partial resection of the small intestine was carried out due to necrosis. Pathologic findings showed mucosal necrosis and extensive vacuolation with gram‐positive rods in the necrotic small intestine. Blood culture tests revealed C. butyricum infection. The patient's condition improved after the surgery. He was moved to a rehabilitation hospital on day 66.

Conclusion

This study suggests that hospitalized adult patients who receive antibiotic treatment are at risk for NEC.

Safety assessment of the Clostridium butyricum MIYAIRI 588® probiotic strain including evaluation of antimicrobial sensitivity and presence of Clostridium toxin genes in vitro and teratogenicity in vivo

Probiotics are live microorganisms ingested for the purpose of conferring a health benefit on the host. Development of new probiotics includes the need for safety evaluations that should consider factors such as pathogenicity, infectivity, virulence factors, toxicity, and metabolic activity. Clostridium butyricum MIYAIRI 588® (CBM 588®), an anaerobic spore-forming bacterium, has been developed as a probiotic for use by humans and food animals. Safety studies of this probiotic strain have been conducted and include assessment of antimicrobial sensitivity, documentation of the lack of Clostridium toxin genes, and evaluation of CBM 588® on reproductive and developmental toxicity in a rodent model. With the exception of aminoglycosides, to which anaerobes are intrinsically resistant, CBM 588® showed sensitivity to all antibiotic classes important in human and animal therapeutics. In addition, analysis of the CBM 588® genome established the absence of genes for encoding for α, β, or ε toxins and botulin neurotoxins types A, B, E, or F. There were no deleterious reproductive and developmental effects observed in mice associated with the administration of CBM 588®. These data provide further support for the safety of CBM 588® for use as a probiotic in animals and humans.

Detection of Clostridium botulinum neurotoxin genes (A-F) in dairy farms from Northern Germany using PCR: A case-control study

Classical botulism in cattle mainly occurs after ingestion of feed contaminated with preformed toxin. In 2001 a form of botulism ("visceral botulism") was postulated to occur after ingestion of Clostridium (C.) botulinum cells or spores, followed by colonization of the intestine, and local production of botulinum neurotoxin (BoNT) causing chronic generalized disease. To verify the potential role of C. botulinum in the described syndrome, a case-control study was conducted, including 139 farms. Fecal samples, rumen content, water and silage samples were collected on each farm. Real time BoNT gene PCR assays were conducted after enrichment in RCM (Reinforced Clostridial Medium) at 37 °C and conventional PCRs after enrichment in MCM (Modified Cooked Meat Medium) at 30 °C. Furthermore, a direct detection of BoNT genes without prior enrichment was attempted. BoNT A, B, C, D, E and F genes were detected in animal samples from 25 (17.99%), 3 (2.16%), 0 (0.0%), 2 (1.44%), 1 (0.72%), and 3 (2.16%) farms, respectively. Eleven feed samples were positive for BoNT A gene. By enrichment a significant increase in sensitivity was achieved. Therefore, this should be an essential part of any protocol. No significant differences regarding BoNT gene occurrence could be observed between Case and Control farms or chronically diseased and clinically healthy animals within the particular category. Thus, the postulated form of chronic botulism in cows could not be confirmed. This study supports the general opinion that C. botulinum can occasionally be found in the rumen and intestine of cows without causing disease.

Evolution of Chromosomal Clostridium botulinum Type E Neurotoxin Gene Clusters: Evidence Provided by Their Rare Plasmid-Borne Counterparts

Analysis of more than 150 Clostridium botulinum Group II type E genomes identified a small fraction (6%) where neurotoxin-encoding genes were located on plasmids. Seven closely related (134–144 kb) neurotoxigenic plasmids of subtypes E1, E3, and E10 were characterized; all carried genes associated with plasmid mobility via conjugation. Each plasmid contained the same 24-kb neurotoxin cluster cassette (six neurotoxin cluster and six flanking genes) that had split a helicase gene, rather than the more common chromosomal rarA. The neurotoxin cluster cassettes had evolved as separate genetic units which had either exited their chromosomal rarA locus in a series of parallel events, inserting into the plasmid-borne helicase gene, or vice versa. A single intact version of the helicase gene was discovered on a nonneurotoxigenic form of this plasmid. The observed low frequency for the plasmid location may reflect one or more of the following: 1) Less efficient recombination mechanism for the helicase gene target, 2) lack of suitable target plasmids, and 3) loss of neurotoxigenic plasmids. Type E1 and E10 plasmids possessed a Clustered Regularly Interspaced Short Palindromic Repeats locus with spacers that recognized C. botulinum Group II plasmids, but not C. botulinum Group I plasmids, demonstrating their long-term separation. Clostridium botulinum Group II type E strains also carry nonneurotoxigenic plasmids closely related to C. botulinum Group II types B and F plasmids. Here, the absence of neurotoxin cassettes may be because recombination requires both a specific mechanism and specific target sequence, which are rarely found together.

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.

The long journey of botulinum neurotoxins into the synapse

Botulinum neurotoxins (BoNT) cause the disease botulism, a flaccid paralysis of the muscle. They are also very effective, widely used medicines applied locally in sub-nanogram quantities. BoNTs are released together with several non-toxic, associated proteins as progenitor toxin complexes (PCT) by Clostridium botulinum to become highly potent oral poisons ingested via contaminated food. They block the neurotransmission in susceptible animals and humans already in nanogram quantities due to their specific ability to enter motoneurons and to cleave only selected neuronal proteins involved in neuroexocytosis. BoNTs have developed a sophisticated strategy to passage the gastrointestinal tract and to be absorbed in the intestine of the host to finally attack neurons. A non-toxic non-hemagglutinin (NTNHA) forms a binary complex with BoNT to protect it from gastrointestinal degradation. This binary M-PTC is one component of the bi-modular 14-subunit ∼760 kDa large progenitor toxin complex. The other component is the structurally and functionally independent dodecameric hemagglutinin (HA) complex which facilitates the absorption on the intestinal epithelium by glycan binding. Subsequent to its transcytosis the HA complex disrupts the tight junction of the intestinal barrier from the basolateral side by binding to E-cadherin. Now, the L-PTC can also enter the circulation by paracellular routes in much larger quantities. From here, the dissociated BoNTs reach the neuromuscular junction and accumulate via interaction with polysialo gangliosides, complex glycolipids, on motoneurons at the neuromuscular junction. Subsequently, additional specific binding to luminal segments of synaptic vesicles proteins like SV2 and synaptotagmin leads to their uptake. Finally, the neurotoxins shut down the synaptic vesicle cycle, which they had exploited before to enter their target cells, via specific cleavage of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins, which constitute the core components of the cellular membrane fusion machinery.

Fatal outbreak of botulism in Greenland

Botulism commonly occurs when the anaerobic, gram-positive bacterium Clostridium botulinum, under suitable conditions, produces botulinum neurotoxins. Named A-F, these toxins are the immediate causative agent of the clinical symptoms of symmetrical, descending neurological deficits, including respiratory muscle paralysis. We present five cases of foodborne botulism occurring in Greenland, two with fatal outcome, caused by ingestion of tradionally preserved eider fowl. In the cases of the survivors, antitoxin and supportive care, including mechanical ventilation, were administered. In these cases recovery was complete. Microbiological assays, including toxin neutralization bioassay, demonstrated the presence of neurotoxin E in two survivors. The third survivor was shown by PCR to have the BoNT type E gene in faeces. This is the first report of cases of fatal botulism in Greenland. It underscores the importance of prompt coordinated case management effort in a geographically isolated area such as Greenland.

Draft Genome Sequence of Clostridium butyricum Strain NOR 33234, Isolated from an Elderly Patient with Diarrhea

Clostridium butyricum is one of the species frequently present in patients’ stool samples. However, the identification of this species is sometimes difficult. Here, we present the draft genome of Clostridium butyricum NOR 33234, which was isolated from a patient with suspected Clostridium difficile infection-associated diarrhea and resembles Clostridium clostridioforme in biochemical tests.

Growth Limiting pH, Water Activity, and Temperature for Neurotoxigenic Strains of Clostridium butyricum

Some rare strains of Clostridium butyricum carry the gene encoding the botulinal type E neurotoxin and must be considered as possible hazards in certain types of food. The limiting growth conditions for C. butyricum were determined in peptone yeast glucose starch (PYGS) broth incubated anaerobically at 30°C for up to 42 days. The minimum pH values permitting growth depended on the acidulant and strain. Organic acids were more effective at inhibiting growth than HCl as expected. The lowest pH values at which growth of toxigenic and nontoxigenic strains of C. butyricum was observed in broth acidified with HCl were 4.1 and 4.2, respectively. In organic acids, however, the minimum pH varied between 4.4 and 5.1 depending on acid type and concentration. The minimum water activity for growth of toxigenic strains of C. butyricum was 0.96. The minimum growth temperatures of the toxigenic strains of C. butyricum (ca 10-11°C) were somewhat higher than for non-toxigenic ones (8°C). It was concluded that control of toxigenic C. butyricum in the food industry needs to allow for the greater pH tolerance of this species compared with proteolytic C. botulinum.

Foodborne botulism in Canada, 1985-2005

During 1985-2005, a total of 91 laboratory-confirmed outbreaks of foodborne botulism occurred in Canada; these outbreaks involved 205 cases and 11 deaths. Of the outbreaks, 75 (86.2%) were caused by Clostridium botulinum type E, followed by types A (7, 8.1%) and B (5, 5.7%). Approximately 85% of the outbreaks occurred in Alaska Native communities, particularly the Inuit of Nunavik in northern Quebec and the First Nations population of the Pacific coast of British Columbia. These populations were predominantly exposed to type E botulinum toxin through the consumption of traditionally prepared marine mammal and fish products. Two botulism outbreaks were attributed to commercial ready-to-eat meat products and 3 to foods served in restaurants; several cases were attributed to non-Native home-prepared foods. Three affected pregnant women delivered healthy infants. Improvements in botulism case identification and early treatment have resulted in a reduction in the case-fatality rate in Canada.

Analysis of Clostridium botulinum serotype E strains by using multilocus sequence typing, amplified fragment length polymorphism, variable-number tandem-repeat analysis, and botulinum neurotoxin gene sequencing

A total of 41 Clostridium botulinum serotype E strains from different geographic regions, including Canada, Denmark, Finland, France, Greenland, Japan, and the United States, were compared by multilocus sequence typing (MLST), amplified fragment length polymorphism (AFLP) analysis, variable-number tandem-repeat (VNTR) analysis, and botulinum neurotoxin (bont) E gene sequencing. The strains, representing environmental, food-borne, and infant botulism samples collected from 1932 to 2007, were analyzed to compare serotype E strains from different geographic regions and types of botulism and to determine whether each of the strains contained the transposon-associated recombinase rarA, involved with bont/E insertion. MLST examination using 15 genes clustered the strains into several clades, with most members within a cluster sharing the same BoNT/E subtype (BoNT/E1, E2, E3, or E6). Sequencing of the bont/E gene identified two new variants (E7, E8) that showed regions of recombination with other E subtypes. The AFLP dendrogram clustered the 41 strains similarly to the MLST dendrogram. Strains that could not be differentiated by AFLP, MLST, or bont gene sequencing were further examined using three VNTR regions. Both intact and split rarA genes were amplified by PCR in each of the strains, and their identities were confirmed in 11 strains by amplicon sequencing. The findings suggest that (i) the C. botulinum serotype E strains result from the targeted insertion of the bont/E gene into genetically conserved bacteria and (ii) recombination events (not random mutations) within bont/E result in toxin variants or subtypes within strains.

Identification of novel linear megaplasmids carrying a ß-lactamase gene in neurotoxigenic Clostridium butyricum type E strains

Since the first isolation of type E botulinum toxin-producing Clostridium butyricum from two infant botulism cases in Italy in 1984, this peculiar microorganism has been implicated in different forms of botulism worldwide. By applying particular pulsed-field gel electrophoresis run conditions, we were able to show for the first time that ten neurotoxigenic C. butyricum type E strains originated from Italy and China have linear megaplasmids in their genomes. At least four different megaplasmid sizes were identified among the ten neurotoxigenic C. butyricum type E strains. Each isolate displayed a single sized megaplasmid that was shown to possess a linear structure by ATP-dependent exonuclease digestion. Some of the neurotoxigenic C. butyricum type E strains possessed additional smaller circular plasmids. In order to investigate the genetic content of the newly identified megaplasmids, selected gene probes were designed and used in Southern hybridization experiments. Our results revealed that the type E botulinum neurotoxin gene was chromosome-located in all neurotoxigenic C. butyricum type E strains. Similar results were obtained with the 16S rRNA, the tetracycline tet(P) and the lincomycin resistance protein lmrB gene probes. A specific mobA gene probe only hybridized to the smaller plasmids of the Italian C. butyricum type E strains. Of note, a ß-lactamase gene probe hybridized to the megaplasmids of eight neurotoxigenic C. butyricum type E strains, of which seven from clinical sources and the remaining one from a food implicated in foodborne botulism, whereas this ß-lactam antibiotic resistance gene was absent form the megaplasmids of the two soil strains examined. The widespread occurrence among C. butyricum type E strains associated to human disease of linear megaplasmids harboring an antibiotic resistance gene strongly suggests that the megaplasmids could have played an important role in the emergence of C. butyricum type E as a human pathogen.

Modulation of urinary bladder innervation: TRPV1 and botulinum toxin A

The persisting interest around neurotoxins such as vanilloids and botulinum toxin (BoNT) derives from their marked effect on detrusor overactivity refractory to conventional antimuscarinic treatments. In addition, both are administered by intravesical route. This offers three potential advantages. First, intravesical therapy is an easy way to provide high concentrations of pharmacological agents in the bladder tissue without causing unsuitable levels in other organs. Second, drugs effective on the bladder, but inappropriate for systemic administration, can be safely used as it is the case of vanilloids and BoNT. Third, the effects of one single treatment might be extremely longlasting, contributing to render these therapies highly attractive to patients despite the fact that the reasons to the prolonged effect are still incompletely understood. Attractive as it may be, intravesical pharmacological therapy should still be considered as a second-line treatment in patients refractory to conventional oral antimuscarinic therapy or who do not tolerate its systemic side effects. However, the increasing off-label use of these neurotoxins justifies a reappraisal of their pharmacological properties.

Multiplex PCR for detection of botulinum neurotoxin-producing clostridia in clinical, food, and environmental samples

Botulinum neurotoxin (BoNT), the most toxic substance known, is produced by the spore-forming bacterium Clostridium botulinum and, in rare cases, also by some strains of Clostridium butyricum and Clostridium baratii. The standard procedure for definitive detection of BoNT-producing clostridia is a culture method combined with neurotoxin detection using a standard mouse bioassay (SMB). The SMB is highly sensitive and specific, but it is expensive and time-consuming and there are ethical concerns due to use of laboratory animals. PCR provides a rapid alternative for initial screening for BoNT-producing clostridia. In this study, a previously described multiplex PCR assay was modified to detect all type A, B, E, and F neurotoxin genes in isolated strains and in clinical, food, environmental samples. This assay includes an internal amplification control. The effectiveness of the multiplex PCR method for detecting clostridia possessing type A, B, E, and F neurotoxin genes was evaluated by direct comparison with the SMB. This method showed 100% inclusivity and 100% exclusivity when 182 BoNT-producing clostridia and 21 other bacterial strains were used. The relative accuracy of the multiplex PCR and SMB was evaluated using 532 clinical, food, and environmental samples and was estimated to be 99.2%. The multiplex PCR was also used to investigate 110 freshly collected food and environmental samples, and 4 of the 110 samples (3.6%) were positive for BoNT-encoding genes.

An overview of type E botulism in China

The geographical distribution of C. botulinum type E and its associated disease, type E botulism in China, is different from that in other areas of the world. Cases of type E botulism generally arise in costal regions. In China, however, type E botulism is found primarily in the Qinghai-Tibet plateau of northwest China far from the ocean, at an altitude of approximately 4-5 km. The foods most commonly associated with the disease are fermented grain and beans as well as raw meat. A suspected outbreak of type E botulism poisoning in the central costal region of China in the 1990s prompted the collection and analysis of samples of mud, sand, and fish from the region. The toxin produced by type E botulinum was found in these samples. Surprisingly, though, upon further analysis, the strain isolated from the samples was identified not as type E C. botulinum, but as the neurotoxigenic bacterium Clostridium butyricum.

Clostridium butyricum sepsis in an injection drug user with an indwelling central venous catheter

Clostridium novyi has been associated with a large outbreak of severe infections in injection drug users. A case of bacteraemia with Clostridium butyricum in an injection drug user is reported. During treatment for Staphylococcus aureus osteomyelitis, the patient used an indwelling central venous catheter to inject cocaine. He was admitted with C. butyricum sepsis that responded to broad spectrum antibiotics, including vancomycin. Local investigation for other cases was unrevealing; however, growth of an unusual pathogen in clinical specimens should be investigated as it may represent a sentinel event with public health implications.

Intestinal toxemia botulism in Italy, 1984–2005

Botulism in humans is caused by botulinum neurotoxins, produced in most cases by Clostridium botulinum, although other Clostridia species are implicated as well. Of the five forms of botulism in humans, three are referred to as "infective": wound botulism, infant botulism, and adult intestinal botulism; the latter two forms are also referred to as "intestinal toxemia botulism" because the organism colonizes the lumen of the intestinal tract and produces botulinum neurotoxin in vivo. Twenty-three cases of infant botulism and three cases of adult intestinal botulism occurred in Italy between 1984 and 2005. Microbiological analyses of clinical, environmental, and food samples and analysis of clinical and epidemiological data revealed two main characteristics of intestinal toxemia botulism in Italy that are not common in cases in other countries: the isolation of a strain of C. butyricum that produced botulinum neurotoxin type E in 6 of 26 cases, including two cases of adult intestinal toxemia botulism, and the onset of botulism in these cases with concomitant severe gastrointestinal symptomatology. This report summarizes the microbiological, clinical, and epidemiological data of all cases of intestinal toxemia botulism that have occurred in Italy in the period 1984-2005.

SYBR green real-time PCR method to detect Clostridium botulinum type A

Botulinum toxins (BoNTs) are classically produced by Clostridium botulinum but rarely also from neurotoxigenic strains of Clostridium baratii and Clostridium butyricum. BoNT type A (BoNT/A), BoNT/B, BoNT/E, and very rarely BoNT/F are mainly responsible for human botulism. Standard microbiological methods take into consideration only the detection of C. botulinum. The presumptive identification of the toxigenic strains together with the typing of BoNT has to be performed by mouse bioassay. The development of PCR-based methods for the detection and typing of BoNT-producing clostridia would be an ideal alternative to the mouse bioassay. The objective of this study was to develop a rapid and robust real-time PCR method for detecting C. botulinum type A. Four different techniques for the extraction and purification of DNA from cultured samples were initially compared. Of the techniques used, Chelex 100, DNeasy tissue kit, InstaGene matrix DNA, and boiling, the boiling technique was significantly less efficient than the other three. These did not give statistically different results, and Chelex 100 was chosen because it was less expensive than the others. In order to eliminate any false-negative results, an internal amplification control was synthesized and included in the amplification mixture according to ISO 22174. The specificity of the method was tested against 75 strains of C. botulinum type A, 4 strains of C. botulinum type Ab, and 101 nontarget strains. The detection limit of the reaction was less than 6 x 10(1) copies of C. botulinum type A DNA. The robustness of the method was confirmed using naturally contaminated stool specimens to evaluate the tolerance of inhibitor substances. SYBR green real-time PCR showed very high specificity for the detection of C. botulinum types A and Ab (inclusivity and exclusivity, 100%).

Sensitive detection of botulinum neurotoxin types C and D with an immunoaffinity chromatographic column test

A sensitive and specific immunoassay for the simultaneous detection of Clostridium botulinum type C (BoNT/C) and type D neurotoxin was developed. Goat anti-mouse immunoglobulin G was bound to polyethylene disks in a small disposable column used for this assay. The sample was preincubated together with monoclonal antibodies specific for the heavy chain of BoNT/C and D and affinity-purified, biotinylated polyclonal antibodies against these neurotoxins. This complex was captured on the assay disk. Streptavidin-poly-horseradish peroxidase was used as a conjugate, and a precipitating substrate allowed the direct semiquantitative readout of the assay, if necessary. For a more accurate quantitative detection, the substrate can be eluted and measured in a photometer. Depending on the preincubation time, a sensitivity of 1 mouse lethal dose ml(-1) was achieved in culture supernatants.

Identification of type A, B, E, and F botulinum neurotoxin genes and of botulinum neurotoxigenic clostridia by denaturing high-performance liquid chromatography

Denaturing high-performance liquid chromatography (DHPLC) is a recently developed technique for rapid screening of nucleotide polymorphisms in PCR products. We used this technique for the identification of type A, B, E, and F botulinum neurotoxin genes. PCR products amplified from a conserved region of the type A, B, E, and F botulinum toxin genes from Clostridium botulinum, neurotoxigenic C. butyricum type E, and C. baratii type F strains were subjected to both DHPLC analysis and sequencing. Unique DHPLC peak profiles were obtained with each different type of botulinum toxin gene fragment, consistent with nucleotide differences observed in the related sequences. We then evaluated the ability of this technique to identify botulinal neurotoxigenic organisms at the genus and species level. A specific short region of the 16S rRNA gene which contains genus-specific and in some cases species-specific heterogeneity was amplified from botulinum neurotoxigenic clostridia and from different food-borne pathogens and subjected to DHPLC analysis. Different peak profiles were obtained for each genus and species, demonstrating that the technique could be a reliable alternative to sequencing for the rapid identification of food-borne pathogens, specifically of botulinal neurotoxigenic clostridia most frequently implicated in human botulism.

Clostridium botulinum and the Clinical Laboratorian: A Detailed Review of Botulism, Including Biological Warfare Ramifications of Botulinum Toxin

Objective.—This review article is designed to thoroughly familiarize all health care professionals with the history, classification, epidemiology, clinical characteristics, differential diagnosis, diagnostic evaluation (including laboratory-based testing), treatment, and prognosis of botulism. It is especially targeted toward clinical laboratorians and includes a detailed enumeration of the important clinical laboratory contributions to the diagnosis, treatment, and monitoring of patients with botulism. Finally, the bioterrorism potential for botulism is discussed, with an emphasis on the clinical laboratory ramifications of this possibility.

Data Sources.—Included medical periodicals and textbooks accessioned from computerized and manual medical literature searches. More than 1000 medical works published from the 1800s through 2003 were retrieved and reviewed in this process.

Data Synthesis.—Pertinent data are presented in textual and tabular formats, the latter including 6 tables presenting detailed information regarding the clinical parameters, differential diagnosis, diagnostic studies, laboratory testing, and therapeutic approaches to botulism.

Conclusions.—Because botulism is such a rare disease, a keen awareness of its manifestations and prompt diagnosis are absolutely crucial for its successful treatment. The bioterrorism potential of botulism adds further urgency to the need for all health care professionals to be familiar with this disease, its proper evaluation, and timely treatment; the need for such urgency clearly includes the clinical laboratory.

Shelf Life and Safety Concerns of Bakery Products—A Review

Bakery products are an important part of a balanced diet and, today, a wide variety of such products can be found on supermarket shelves. This includes unsweetened goods (bread, rolls, buns, crumpets, muffins and bagels), sweet goods (pancakes, doughnuts, waffles and cookies) and filled goods (fruit and meat pies, sausage rolls, pastries, sandwiches, cream cakes, pizza and quiche). However, bakery products, like many processed foods, are subject to physical, chemical and microbiological spoilage. While physical and chemical spoilage limits the shelf life of low and intermediate moisture bakery products, microbiological spoilage by bacteria, yeast and molds is the concern in high moisture products i.e., products with a water activity (a(w)) > 0.85. Furthermore, several bakery products also have been implicated infoodborne illnesses involving Salmonella spp., Listeria monoctyogenes and Bacillus cereus, while Clostridium botulinum is a concern in high moisture bakery products packaged under modified atmospheres. This extensive review is divided into two parts. Part I focuses on the spoilage concerns of low, intermediate and high moisture bakery products while Part II focuses on the safety concerns of high moisture bakery products only. In both parts, traditional and novel methods of food preservation that can be used by the bakery industry to extend the shelf life and enhance the safety of products are discussed in detail.

Characterisation of botulinum toxins type A and B, by matrix-assisted laser desorption ionisation and electrospray mass spectrometry

A method earlier developed for the mass spectrometric (MS) identification of tetanus toxin (TTx) was applied to botulinum toxins type A and B (BTxA and BTxB). Botulinum toxins are extremely neurotoxic bacterial toxins, likely to be used as biological warfare agent. Biologically active BTxA and BTxB are comprised of a protein complex of the respective neurotoxins with specific haemagglutinins (HAs) and non-toxic non-haemagglutinins (NTNHs). These protein complexes are also observed in mass spectrometric identification. The particular BTxA complex, from Clostridium botulinum strain 62A, almost completely matched database data derived from genetic sequences known for this strain. Although no such database information was available for BTxB, from C. botulinum strain okra, all protein sequences from the complex except that of HA-70 were found to match proteins known from other type B strains. It was found that matrix-assisted laser desorption ionisation MS provides provisional identification from trypsin digest peptide maps and that liquid chromatography electrospray (tandem) mass spectrometry affords unequivocal identification from amino acid sequence information of digest peptides obtained in trypsin or pepsin digestion.

Taxonomic identity of type E botulinum toxin-producing Clostridium butyricum strains by sequencing of a short 16S rDNA region

Several micro-organisms capable of producing botulinum neurotoxin type E, though phenotypically similar to Clostridium butyricum (a normally non-neurotoxigenic organism), have recently been isolated in Italy and China. Some of these micro-organisms had been implicated in food-borne botulism, a serious neuroparalytic disease. The taxonomic identity of the type E botulinum toxin-producing strains is confirmed here, through sequencing of a genus- and species-specific segment of the 16S rRNA gene. Confirmation leads to the conclusion that neurotoxigenic C. butyricum must be regarded as an emergent food-borne pathogen.

Influence of pH and temperature on the growth of and toxin production by neurotoxigenic strains of Clostridium butyricum type E

Strains of Clostridium butyricum that produce botulinal toxin type E have been implicated in outbreaks of foodborne botulism in China, India, and Italy, yet the conditions that are favorable for the growth and toxinogenesis of these strains remain to be established. We attempted to determine the temperatures and pH levels that are most conducive to the growth of and toxin production by the six strains of neurotoxigenic C. butyricum that have been implicated in outbreaks of infective and foodborne botulism in Italy. The strains were cultured for 180 days on Trypticase-peptone-glucose-yeast extract broth at various pHs (4.6, 4.8, 5.0, 5.2, 5.4, 5.6, and 5.8) at 30 degrees C and at various temperatures (10, 12, and 15 degrees C) at pH 7.0. Growth was determined by checking for turbidity; toxin production was determined by the mouse bioassay. We also inoculated two foods: mascarpone cheese incubated at 25 and 15 degrees C and pesto sauce incubated at 25 degrees C. The lowest pH at which growth and toxin production occurred was 4.8 at 43 and 44 days of incubation, respectively. The lowest temperature at which growth and toxin production occurred was 12 degrees C, with growth and toxin production first being observed after 15 days. For both foods, toxin production was observed after 5 days at 25 degrees C. Since the strains did not show particularly psychrotrophic behavior, 4 degrees C can be considered a sufficiently low temperature for the inhibition of growth. However, the observation of toxin production in foods at room temperature and at abused refrigeration temperatures demands that these strains be considered a new risk for the food industry.

Impact of small scale fermentation technology on food safety in developing countries

Fermentation is one of the oldest technologies used for food preservation. Over the centuries, it has evolved and been refined and diversified. Today, a variety of food products is derived from this technology in households, small-scale food industries as well as in large enterprises. Furthermore, fermentation is an affordable food preservation technology and of economic importance to developing countries. In the report of an FAO/WHO Workshop (FAO/WHO, 1996), fermentation was reviewed and the nutritional and safety aspects of fermentation technologies and their products were assessed. Fermentation enhances the nutritional quality of foods and contributes to food safety particularly under conditions where refrigeration or other foods processing facilities are not available. Hazard Analysis and Critical Control Point (HACCP) studies of some fermented products have demonstrated that depending on the process and the hygienic conditions observed during preparation, some fermented foods, e.g. togwa prepared in Tanzania, may pose a safety risk. Fermented foods must therefore be studied following HACCP principles and small-scale food industries and households must be advised on the critical control points of fermentation processes and the control measures to be applied at these points. This paper reviews the risks and benefits of fermentation and demonstrates the application of the HACCP system to some fermented foods in developing countries.

Clostridium botulinum and its neurotoxins: a metabolic and cellular perspective

Clostridium botulinum comprises a diverse assemblage of clostridia that have the common property of producing a distinctive protein neurotoxin (BoNT) of similar pharmacological activity and extraordinary potency. BoNTs are produced in culture as molecular complexes consisting of BoNT, hemagglutinin (HA) and associated subcomponent proteins, nontoxic nonhemagglutinin (NTNH), and RNA. The genes encoding the protein components reside as a cluster on the chromosome, on bacteriophages, or on plasmids depending on the C. botulinum serotype. A gene BotR coding for a regulatory protein has been detected in toxin gene clusters from certain strains, as well as ORFs coding for uncharacterized components. The gene encoding TeNT is located on a large plasmid, and expression of the structural gene is controlled by the regulatory gene, TetR, located immediately upstream of the TeNT structural gene. TeNT is not known to be assembled into a protein/nucleic acid complex in culture. Cellular synthesis of BoNT and TeNT have been demonstrated to be positively regulated by the homologous proteins, BotR/A and TetR. Evidence suggests that negative regulatory factors and general control cascades such as those involved in nitrogen regulation and carbon catabolite repression also regulate synthesis of BoNTs. Neurotoxigenic clostridia have attracted considerable attention from scientists and clinicians during the past decade, and many excellent reviews are available on various aspects of these organisms and their neurotoxins. However, certain areas have not been well-studied, including metabolic regulation of toxin formation and genetic tools to study neurotoxigenic clostridia. These topics are the focus of this review.

An outbreak in Italy of botulism associated with a dessert made with mascarpone cream cheese

In the late 1996, an outbreak of botulism affected eight young people (age of patients ranged from 6 to 23 years) in Italy. The onset of the illness was the same for all of these patients: gastrointestinal symptoms (nausea and vomiting) followed by neurologic symptoms. The most common neurologic symptoms were dysphagia, respiratory failure (100%), diplopia (87%), dysarthria, ptosis (75%) and mydriasis (50%). All patients required mechanical ventilation. Botulinum toxin was detected from two of respectively five sera and six stool samples analysed, while spores of Clostridium botulinum type A were recovered from all patient' faeces. The epidemiological investigation led to suspect a commercial cream cheese ('mascarpone') as a source of botulinum toxin: indeed, it had been eaten by all the patients before onset of the symptoms, either alone or as the (uncooked) ingredient of a dessert, 'tiramisù'. Botulinum toxin type A was found in the 'tiramisù' leftover consumed by two patients and in some mascarpone cheese samples collected from the same retail stores where the other patients had previously bought their cheeses. A break in the cold-chain at the retail has likely caused germination of C. botulinum spores contaminating the products, with subsequent production of the toxin. One of the patients died, while the others recovered very slowly. Prompt international alerting and recall of the mascarpone cheese prevented the spread of the outbreak due to the wide range of distribution, demonstrating the importance of a rapid surveillance system. None of the people complaining of symptoms after the public alert resulted positive for botulinum spores and toxin.

Clostridium botulinum and the ophthalmologist: a review of botulism, including biological warfare ramifications of botulinum toxin

The anaerobic bacterium Clostridium botulinum causes disease by elaborating an extremely potent neurotoxin that inhibits release of acetylcholine at presynaptic nerve endings, thereby resulting in a descending flaccid paralysis and autonomic nervous system dysfunction. Possible ophthalmological effects of this neurotoxin are many and typically constitute the earliest manifestations of botulism. This review summarizes the medical literature on botulism with regard to historical perspective, epidemiology, clinical manifestations, and treatment. Ophthalmological findings of botulism are tabulated and their frequencies are provided. Finally, the bioterrorism/biologic warfare ramifications of botulinum toxin are briefly discussed.

Genetic analysis of type E botulinum toxin-producing Clostridium butyricum strains

Type E botulinum toxin (BoNT/E)-producing Clostridium butyricum strains isolated from botulism cases or soil specimens in Italy and China were analyzed by using nucleotide sequencing of the bont/E gene, random amplified polymorphic DNA (RAPD) assay, pulsed-field gel electrophoresis (PFGE), and Southern blot hybridization for the bont/E gene. Nucleotide sequences of the bont/E genes of 11 Chinese isolates and of the Italian strain BL 6340 were determined. The nucleotide sequences of the bont/E genes of 11 C. butyricum isolates from China were identical. The deduced amino acid sequence of BoNT/E from the Chinese isolates showed 95.0 and 96.9% identity with those of BoNT/E from C. butyricum BL 6340 and Clostridium botulinum type E, respectively. The BoNT/E-producing C. butyricum strains were divided into the following three clusters based on the results of RAPD assay, PFGE profiles of genomic DNA digested with SmaI or XhoI, and Southern blot hybridization: strains associated with infant botulism in Italy, strains associated with food-borne botulism in China, and isolates from soil specimens of the Weishan lake area in China. A DNA probe for the bont/E gene hybridized with the nondigested chromosomal DNA of all toxigenic strains tested, indicating chromosomal localization of the bont/E gene in C. butyricum. The present results suggest that BoNT/E-producing C. butyricum is clonally distributed over a vast area.

Intestinal toxemia botulism in two young people, caused by Clostridium butyricum type E

Two unconnected cases of type E botulism involving a 19-year-old woman and a 9-year-old child are described. The hospital courses of their illness were similar and included initial acute abdominal pain accompanied by progressive neurological impairment. Both patients were suspected of having appendicitis and underwent laparotomy, during which voluminous Meckel's diverticula were resected. Unusual neurotoxigenic Clostridium butyricum strains that produced botulinum-like toxin type E were isolated from the feces of the patients. These isolates were genotypically and phenotypically identical to other neurotoxigenic C. butyricum strains discovered in Italy in 1985-1986. No cytotoxic activity of the strains that might explain the associated gastrointestinal symptoms was demonstrated. The clinical picture of the illness and the persistence of neurotoxigenic clostridia in the feces of these patients suggested a colonization of the large intestine, with in vivo toxin production. The possibility that Meckel's diverticulum may predispose to intestinal toxemia botulism may warrant further investigation.

Identification, assessment and management of food-related microbiological hazards: historical, fundamental and psycho-social essentials

Microbiological risk assessment aimed at devising measures of hazard management, should take into account all perceived hazards, including those not empirically identified. It should also recognise that safety cannot be "inspected into" a food. Rather hazard management should be the product of intervention strategies in accordance with the approach made mandatory in the EU Directive 93/43 and the USDA FSIS Pathogen Reduction HACCP system; Final Rule. It is essential too that the inherent variability of the biological attributes affecting food safety is recognised in any risk assessment. The above strategic principles may be conceptualised as a four-step sequence, involving (i) identification and quantification of hazards; (ii) design and codification of longitudinally integrated ("holistic") technological processes and procedures to eliminate, or control growth and metabolism of, pathogenic and toxinogenic organisms; (iii) elaboration of microbiological analytical standard operating procedures, permitting validation of "due diligence" or responsible care, i.e. adherence to adopted intervention strategies. This should be supported by empirically assessed reference ranges, particularly for marker organisms, while the term "zero tolerance" is refined throughout to tolerable safety limit; (iv) when called for, the need to address concerns arising from lay perceptions of risk which may lack scientific foundation. In relation to infectious and toxic hazards in the practical context the following general models for quantitative holistic risk assessment are presented: (i) the first order, basic lethality model; (ii) a second approximation taking into account the amount of food ingested in a given period of time; (iii) a further adjustment accounting for changes in colonization levels during storage and distribution of food commodities and the effects of these on proliferation of pathogens and toxin production by bacteria and moulds. Guidelines are provided to address: (i) unsubstantiated consumer concern over the wholesomeness of foods processed by an innovative procedure; and (ii) reluctance of small food businesses to adopt novel strategies in food safety. Progress here calls for close cooperation with behavioural scientists to ensure that investment in developing measures to contain risk deliver real benefit.