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Viable Clostridium botulinum spores not detected in the household dust of major Canadian cities.

ABSTRACT: Clostridium botulinum causes infant botulism by colonising the intestines and producing botulinum neurotoxin in situ. Previous reports have linked infant botulism cases to C. botulinum spores in household dust, yet the baseline incidence of C. botulinum spores in residential households is currently unknown. Vacuum cleaner dust from 963 households in 13 major Canadian cities was tested for C. botulinum using a novel real-time PCR assay directed against all known subtypes of the botulinum neurotoxin gene. None of the samples tested positive for C. botulinum. Analysis of a random subset of samples by MALDI Biotyper revealed that the most common anaerobic bacterial isolates were of the genus Clostridium and the most common species recovered overall was Clostridium perfringens. Dust that was spiked with C. botulinum spores of each toxin type successfully produced positive real-time PCR reactions. These control experiments indicate that this is a viable method for the detection of C. botulinum spores in household dust. We make several recommendations for future work that may help discover a common environmental source of C. botulinum spores that could lead to effective preventative measures for this rare but deadly childhood disease.

SUBMITTER: Harris RA

PROVIDER: S-EPMC10548537 | biostudies-literature | 2023 Sep

REPOSITORIES: biostudies-literature

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Viable Clostridium botulinum spores not detected in the household dust of major Canadian cities.

Harris Richard A RA Blondin-Brosseau Madeleine M Levesque Christine C Rasmussen Pat E PE Beauchemin Suzanne S Austin John W JW

Epidemiology and infection 20230907

Clostridium botulinum causes infant botulism by colonising the intestines and producing botulinum neurotoxin in situ. Previous reports have linked infant botulism cases to C. botulinum spores in household dust, yet the baseline incidence of C. botulinum spores in residential households is currently unknown. Vacuum cleaner dust from 963 households in 13 major Canadian cities was tested for C. botulinum using a novel real-time PCR assay directed against all known ...[more]

PMID: 37675600

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Project description:UnlabelledHeat 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.ImportanceIn 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.

Project description:The PFGRC has developed a cost effective alternative to complete genome sequencing in order to study the genetic differences between closely related species and/or strains. The comparative genomics approach combines Gene Discovery (GD) and Comparative Genomic Hybridization (CGH) techniques, resulting in the design and production of species microarrays that represent the diversity of a species beyond just the sequenced reference strain(s) used in the initial microarray design. These species arrays may then be used to interrogate hundreds of closely related strains in order to further unravel their evolutionary relationships. Clostridium botulinum produces botulinum neurotoxin (BoNT)and is classified as a “Category A” select agent. BoNT can be classified into seven serotypes designated A-G. There is considerable genetic variation within these serotypes, as demonstrated by the recognition of at least 47 subtypes. The most studied serotype, BoNT/A, has been found in a large and diverse group of clostridia, most of which express the subtype BoNT/A1. The BoNT/A1 producing C. botulinum strain ATCC 3502, used to obtain an initial annotated genome sequence, is not representative of the diverse clostridia group producing BoNT. Nearly 50% of C. botulinum strains producing BoNT/A1 have been shown to also encode unexpressed variants of BoNT/B with a distinct cluster arrangement. This nucleotide cluster is completely absent from the published genome sequence. In addition, a recently identified novel BoNT/A1 strain lacks the gene cluster seen in the genome sequence of ATCC 3502. Furthermore, a strain designated Hall A Hyper differs greatly from the sequenced strain as indicated by its ability to produce higher quantities of BoNT/A1. The genetic and phenotypic basis for this difference in BoNT expression is currently unknown, and the sequences of the BoNT gene and the cluster are identical in both strains. This observation supports the hypothesis that genes outside the toxin cluster are involved in the regulation and maturation of BoNT. The flow of genetic information within this group motivated us to identify novel genes for the purpose of creating a “species” DNA microarray to better understand the ancestral relationships among its members. Based on preliminary genotyping (MLST, and CGH using a single-genome-based array), 20 diverse C. botulinum strains were selected for sequencing. Sequence information obtained from this project, and from other publicly available sources, led to the development of a comprehensive species microarray for C. botulinum group members. The availability of the C. botulinum species DNA microarray has allowed us to carry out a collaborative CGH genotyping project to validate this microarray as well as understand the phylogenomic relationships among members of C. botulinum group.

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Viable Clostridium botulinum spores not detected in the household dust of major Canadian cities.

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Viable <i>Clostridium botulinum</i> spores not detected in the household dust of major Canadian cities.

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