Botulism and hot-smoked whitefish: a family cluster of type E botulism in France, September 2009

Tracing Foodborne Botulism Events Caused by Clostridium botulinum in Xinjiang Province, China, Using a Core Genome Sequence Typing Scheme

Foodborne botulism is a rare but life-threatening illness resulting from the action of a potent toxin mainly produced by Clostridium botulinum. It grows in an oxygen-deficient environment and is extremely viable in meat and soy products, making it one of the most virulent bacteria. How to track foodborne botulism events quickly and accurately has become a key issue. Here, we investigated two foodborne botulism events that occurred in Xinjiang in 2019 based on whole-genome sequencing and also successfully traced the relationship between clinical and food C. botulinum isolates using whole-genome core gene markers. All 59 isolates were classified as group I strains. Of the strains isolated in this study, 44 were found to be botulinum toxin A(B), and 15 isolates contained only the toxin B locus. Both the toxin A and B gene segments were located on the chromosome and organized in an ha cluster. Antibiotic resistance and virulence factors were also investigated. A set of 329 universal core gene markers were established using C. botulinum strains from a public database. These core gene markers were applied to the published C. botulinum genomes, and three outbreaks were identified. This work demonstrates that universal core gene markers can be used to trace foodborne botulism events, and we hope that our work will facilitate this effort in future. IMPORTANCE In this study, we analyzed 59 foodborne botulism (FB)-related strains isolated in Xinjiang Province, China. Our findings not only reveal the group classification, neurotoxin locus organization, antibiotic resistance and virulence factors of these strains but also establish a set of core gene markers for tracing foodborne botulism events, which was verified using published genomes. These findings indicate that these gene markers might be used as a potential tracing tool for FB events caused by C. botulinum group I strains, which have relatively stable genomic components.

Epidemiology and risk factors for notifiable Clostridium botulinum infections in Taiwan from 2003 to 2020

Botulinum toxin is produced by Clostridium botulinum, a gram-positive anaerobic bacterium. This study aimed to examine the epidemiological characteristics, including sex, age, season in which infection occurred, place of residence, and epidemiological trends, of confirmed botulism cases in Taiwan from 2003 to 2020. This study examined the annual summary data on reported botulism in Taiwan' s Center for Disease Control from 2003 to 2020 available to the public on the internet. We found that there were 50 confirmed domestic cases of botulism. The incidence of botulism ranged from 0 to 0.48 per 1000,000 from 2003 to 2020 and peaked in 2008 and 2010. During the 18-year investigation period in which 6-year intervals were used, the study results showed a decreasing trend (2003-2008, 2009-14, and 2015-2020, had 22, 19, 9 cases each). In terms of patients' gender, age, and place of residence, most of the patients were females (56%), were aged ≥ 50 years (48%), and resided in Taipei and northern Taiwan (44%). The number of botulism cases in Taiwan from 2012 to 2020 compared with other years (from 2003 to 2011) found that there were significant differences among patients within an age group of <20 years (P = .003, odds ratio = 18.500, and 95% confidence interval = 3.287-104.111), and there were significant differences among patients whose place of residence was Taipei metropolitan area (P = .025, odds ratio = 5.667, and 95% confidence interval = 1.248-25.734). During 2003 to 2009, there was no case of botulism among those aged <20 years. Over the last 10 years, botulism in children showed an increasing trend. A total of 9 children were found to have botulism during 2010 to 2020; most of these children were male (66.7%) and were infected during spring and summer (66.7%). This study is the first to report the number of confirmed domestic cases with botulism from surveillance data from Taiwan's Center for Disease Control during 2003 to 2020. This study also found that the place of residence and age were associated with an increased risk of botulism in Taiwan. This information may be useful for policymakers and clinical experts to direct prevention- and control-based activities regarding botulism that result in the most severe illness and the greatest burden on Taiwanese.

Human Botulism in France, 1875-2016

Botulism is a rare but severe disease which is characterized by paralysis and inhibition of secretions. Only a few cases had been reported at the end of the 19th century in France. The disease was frequent during the second world war, and then the incidence decreased progressively. However, human botulism is still present in France with 10-25 cases every year. Food-borne botulism was the main form of botulism in France, whereas infant botulism (17 cases between 2004 and 2016) was rare, and wound and inhalational botulism were exceptional. Type B was the prevalent botulism type and was mainly due to consumption of home-made or small-scale preparations of cured ham and to a lesser extent other pork meat products. In the recent period (2000-2016), a wider diversity of botulism types from various food origin including industrial foods was reported. Severe cases of type A and F botulism as well as type E botulism were more frequent. Albeit rare, the severity of botulism justifies its continued surveillance and recommendations to food industry and consumers regarding food hygiene and preservation practices.

Assessment of the risk of botulism from chilled, vacuum/modified atmosphere packed fresh beef, lamb and pork held at 3 °C-8 °C

The safety of current UK industry practice (including shelf-life) for chilled, vacuum/modified atmosphere-packed fresh red meat (beef, lamb and pork) held at 3°C-8°C has been evaluated with respect to non-proteolytic Clostridium botulinum. UK industry typically applies a retail pack shelf-life at 3°C-8°C to 13 days for fresh red meat, with a maximum of 23 days for beef, 27 days for lamb, and 18 days for pork. An exposure assessment established that current commercial practice for fresh red meat provided strong protection with more than 10¹⁰ person servings marketed in the UK without association with foodborne botulism. A challenge test demonstrated that spores of non-proteolytic C. botulinum inoculated on chilled vacuum-packed fresh red meat did not lead to detectable neurotoxin at day 50 for beef, day 35 for lamb, or day 25 for pork (i.e. <40 pg type B toxin and type E toxin g^-1 of meat). The products were visually spoiled many days before these end points. The exposure assessment and challenge test demonstrated the safety of current UK industry practices for the shelf-life of fresh, vacuum-packed beef, lamb and pork held at 3°C-8°C with respect to C. botulinum, and that botulinum neurotoxin was not detected within their organoleptic shelf-life.

High prevalence of Clostridium botulinum in vegetarian sausages

Clostridium botulinum is a significant food safety concern due to its ability to produce highly potent neurotoxin and resistant endospores. Vegetarian sausages have become a popular source of plant protein and alternative for meat products. While vegetarian sausages have not been linked to botulism, numerous outbreaks due to preserved vegetables suggest a frequent occurrence of C. botulinum spores in the raw material. The product formulation of vegetarian sausages involves limited NaCl and preservatives, and shelf-lives may be several months. The safety of vegetarian sausages thus relies mainly on heat treatment and chilled storage. The main food safety concern is C. botulinum Group II that can grow and produce toxin at refrigeration temperatures. Here we show a high overall prevalence (32%) of C. botulinum in 74 samples of vegetarian sausages from seven producers. Both Groups I and II strains and genes for neurotoxin types A, B, E and F were detected in the products. The highest cell counts (1200 spores/kg) were observed for C. botulinum Group II in products with remaining shelf-lives of 6 months at the time of purchase. We conclude that vacuum-packaged vegetarian sausage products frequently contain C. botulinum spores and may possess a high risk of C. botulinum growth and toxin production. Chilled storage below 3°C and thorough reheating before consumption are warranted.

Systematic Assessment of Nonproteolytic Clostridium botulinum Spores for Heat Resistance

Heat treatment is an important controlling factor that, in combination with other hurdles (e.g., pH, aw), is used to reduce numbers and prevent the growth of and associated neurotoxin formation by nonproteolytic C. botulinum in chilled foods. It is generally agreed that a heating process that reduces the spore concentration by a factor of 10(6) is an acceptable barrier in relation to this hazard. The purposes of the present study were to review the available data relating to heat resistance properties of nonproteolytic C. botulinum spores and to obtain an appropriate representation of parameter values suitable for use in quantitative microbial risk assessment. In total, 753 D values and 436 z values were extracted from the literature and reveal significant differences in spore heat resistance properties, particularly those corresponding to recovery in the presence or absence of lysozyme. A total of 503 D and 338 z values collected for heating temperatures at or below 83°C were used to obtain a probability distribution representing variability in spore heat resistance for strains recovered in media that did not contain lysozyme.

IMPORTANCE

In total, 753 D values and 436 z values extracted from literature sources reveal significant differences in spore heat resistance properties. On the basis of collected data, two z values have been identified, z = 7°C and z = 9°C, for spores recovered without and with lysozyme, respectively. The findings support the use of heat treatment at 90°C for 10 min to reduce the spore concentration by a factor of 10(6), providing that lysozyme is not present during recovery. This study indicates that greater heat treatment is required for food products containing lysozyme, and this might require consideration of alternative recommendation/guidance. In addition, the data set has been used to test hypotheses regarding the dependence of spore heat resistance on the toxin type and strain, on the heating technique used, and on the method of D value determination used.

Neutralization of Botulinum Neurotoxin Type E by a Humanized Antibody

Botulinum neurotoxins (BoNTs) cause botulism and are the deadliest naturally-occurring substances known to humans. BoNTs have been classified as one of the category A agents by the Centers for Disease Control and Prevention, indicating their potential use as bioweapons. To counter bio-threat and naturally-occurring botulism cases, well-tolerated antibodies by humans that neutralize BoNTs are relevant. In our previous work, we showed the neutralizing potential of macaque (Macaca fascicularis)-derived scFv-Fc (scFv-Fc ELC18) by in vitro endopeptidase immunoassay and ex vivo mouse phrenic nerve-hemidiaphragm assay by targeting the light chain of the botulinum neurotoxin type E (BoNT/E). In the present study, we germline-humanized scFv-Fc ELC18 into a full IgG hu8ELC18 to increase its immunotolerance by humans. We demonstrated the protection and prophylaxis capacity of hu8ELC18 against BoNT/E in a mouse model. A concentration of 2.5 ng/mouse of hu8ELC18 protected against 5 mouse lethal dose (MLD) in a mouse protection assay and complete neutralization of 1 LD50 of pure BoNT/E toxin was achieved with 8 ng of hu8ELC18 in mouse paralysis assay. Furthermore, hu8ELC18 protected mice from 5 MLD if injected up to 14 days prior to intraperitoneal BoNT/E administration. This newly-developed humanized IgG is expected to have high tolerance in humans.

Diversity of Group I and II Clostridium botulinum Strains from France Including Recently Identified Subtypes

In France, human botulism is mainly food-borne intoxication, whereas infant botulism is rare. A total of 99 group I and II Clostridium botulinum strains including 59 type A (12 historical isolates [1947-1961], 43 from France [1986-2013], 3 from other countries, and 1 collection strain), 31 type B (3 historical, 23 recent isolates, 4 from other countries, and 1 collection strain), and 9 type E (5 historical, 3 isolates, and 1 collection strain) were investigated by botulinum locus gene sequencing and multilocus sequence typing analysis. Historical C. botulinum A strains mainly belonged to subtype A1 and sequence type (ST) 1, whereas recent strains exhibited a wide genetic diversity: subtype A1 in orfX or ha locus, A1(B), A1(F), A2, A2b2, A5(B2') A5(B3'), as well as the recently identified A7 and A8 subtypes, and were distributed into 25 STs. Clostridium botulinum A1(B) was the most frequent subtype from food-borne botulism and food. Group I C. botulinum type B in France were mainly subtype B2 (14 out of 20 historical and recent strains) and were divided into 19 STs. Food-borne botulism resulting from ham consumption during the recent period was due to group II C. botulinum B4. Type E botulism is rare in France, 5 historical and 1 recent strains were subtype E3. A subtype E12 was recently identified from an unusual ham contamination. Clostridium botulinum strains from human botulism in France showed a wide genetic diversity and seems to result not from a single evolutionary lineage but from multiple and independent genetic rearrangements.

A penicillin- and metronidazole-resistant Clostridium botulinum strain responsible for an infant botulism case

The clinical course of a case of infant botulism was characterized by several relapses despite therapy with amoxicillin and metronidazole. Botulism was confirmed by identification of botulinum toxin and Clostridium botulinum in stools. A C. botulinum A2 strain resistant to penicillins and with heterogeneous resistance to metronidazole was isolated from stool samples up to 110 days after onset. Antibiotic susceptibility was tested by disc agar diffusion and MICs were determined by Etest. Whole genome sequencing allowed detection of a gene cluster composed of blaCBP for a novel penicillinase, blaI for a regulator, and blaR1 for a membrane-bound penicillin receptor in the chromosome of the C. botulinum isolate. The purified recombinant penicillinase was assayed. Resistance to β-lactams was in agreement with the kinetic parameters of the enzyme. In addition, the β-lactamase gene cluster was found in three C. botulinum genomes in databanks and in two of 62 genomes of our collection, all the strains belonging to group I C. botulinum. This is the first report of a C. botulinum isolate resistant to penicillins. This stresses the importance of antibiotic susceptibility testing for adequate therapy of botulism.

Quantification of Nonproteolytic Clostridium botulinum Spore Loads in Food Materials

We have produced data and developed analysis to build representations for the concentration of spores of nonproteolytic Clostridium botulinum in materials that are used during the manufacture of minimally processed chilled foods in the United Kingdom. Food materials are categorized into homogenous groups which include meat, fish, shellfish, cereals, fresh plant material, dairy liquid, dairy nonliquid, mushroom and fungi, and dried herbs and spices. Models are constructed in a Bayesian framework and represent a combination of information from a literature survey of spore loads from positive-control experiments that establish a detection limit and from dedicated microbiological tests for real food materials. The detection of nonproteolytic C. botulinum employed an optimized protocol that combines selective enrichment culture with multiplex PCR, and the majority of tests on food materials were negative. Posterior beliefs about spore loads center on a concentration range of 1 to 10 spores kg(-1). Posterior beliefs for larger spore loads were most significant for dried herbs and spices and were most sensitive to the detailed results from control experiments. Probability distributions for spore loads are represented in a convenient form that can be used for numerical analysis and risk assessments.

Genomes, neurotoxins and biology of Clostridium botulinum Group I and Group II

Recent developments in whole genome sequencing have made a substantial contribution to understanding the genomes, neurotoxins and biology of Clostridium botulinum Group I (proteolytic C. botulinum) and C. botulinum Group II (non-proteolytic C. botulinum). Two different approaches are used to study genomics in these bacteria; comparative whole genome microarrays and direct comparison of complete genome DNA sequences. The properties of the different types of neurotoxin formed, and different neurotoxin gene clusters found in C. botulinum Groups I and II are explored. Specific examples of botulinum neurotoxin genes are chosen for an in-depth discussion of neurotoxin gene evolution. The most recent cases of foodborne botulism are summarised.