Isolation and characterization of Bacillus cereus-like bacteria from faecal samples from greenhouse workers who are using Bacillus thuringiensis-based insecticides

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In a study of occupational exposure to Bacillus thuringiensis, 20 exposed greenhouse workers were examined for Bacillus cereus-like bacteria in fecal samples and on biomonitoring filters. Bacteria with the following characteristics were isolated from eight individuals: intracellular crystalline inclusions characteristic of B. thuringiensis, genes for and production of B. cereus enterotoxins, and positivity for cry11 as determined by PCR. DNA fingerprints of the fecal isolates were identical to those of strains isolated from the commercial products used. Work processes (i.e., spraying) correlated with the presence of B. thuringiensis in the fecal samples (10 2 to 10 3 CFU/g of feces). However, no gastrointestinal symptoms correlated with the presence of B. thuringiensis in the fecal samples.

Section: Discussionmentioning

confidence: 61%

Section: Designmentioning

confidence: 99%

Bacillus thuringiensis in Fecal Samples from Greenhouse Workers after Exposure to B. thuringiensis -Based Pesticides

Jensen

Larsen

Jacobsen

et al. 2002

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“…Previous studies have shown growers to be exposed to Bacillus thuringiensis applied by spraying (19,26,27). The three biocontrol organisms included in this study (T. harzianum, Beauveria sp., and S. griseoviridis) were not observed to be a natural part of the airborne microbiota in the greenhouse.…”

Section: Discussionmentioning

confidence: 99%

“…Application of biocontrol products that contain MPCAs may increase growers' exposure to the microbial agent (9,19,26,27). The biocontrol product Supresivit contains the ascomycete Trichoderma harzianum (Rifai 1969) which belongs to the family Hypocreaceae.…”

mentioning

confidence: 99%

Exposure to Bioaerosols during the Growth Season of Tomatoes in an Organic Greenhouse Using Supresivit ( Trichoderma harzianum ) and Mycostop ( Streptomyces griseoviridis )

Hansen

Winding

Madsen

2010

In working environments, especially in confined spaces like greenhouses, elevated concentrations of airborne microorganisms may become a problem for workers' health. Additionally, the use of microbial pest control agents (MPCAs) may increase exposure to microorganisms. The aim of this study was to investigate tomato growers' exposure to naturally occurring bioaerosol components [dust, bacteria, fungi, actinomycetes, (133)-␤-D-glucans, and endotoxin] and MPCAs applied by drip irrigation. Airborne dust was collected with filter samplers and analyzed for microorganisms by plate counts and total counts using a microscope. Analysis of (133)-␤-D-glucan and endotoxin content was performed by kinetic, chromatic Limulus amoebocyte lysate tests. The fungal strain (Trichoderma harzianum) from the biocontrol product Supresivit was identified by PCR analysis. Measurements were performed on the day of drip irrigation and 1 week, 1 month, and 3 months after the irrigation. T. harzianum from Supresivit could be detected only on the day of treatment. Streptomyces griseoviridis, an applied MPCA, was not detected in the air during this investigation. We found that bioaerosol exposure increases during the growth season and that exposure to fungi, bacteria, and endotoxin can reach levels during the harvest period that may cause respiratory symptoms in growers. The collected data indicate that MPCAs applied by drip irrigation do not become airborne later in the season.

“…However, the role of CytK is not yet fully understood, since recent studies have indicated the existence of two variants of CytK (4, 10), the one (CytK2) having a lower toxicity than CytK1, which caused the severe food poisoning case. Also, commercially used B. thuringiensis strains have been shown to harbor genes for HBL, NHE, and CytK, and the expression of components of the three-component enterotoxins HBL and NHE has also been established (8,16,22).Since methods for identification of B. cereus-like bacteria in food and clinical settings do not distinguish between B. cereus and B. thuringiensis, the presence of B. thuringiensis in food and the role of this organism in food poisoning are not well described. The bacterium B. thuringiensis has only in one case been associated with food poisoning (15), although the bacterium has the same genetic potential for producing enterotoxins as B. cereus.…”

mentioning

confidence: 99%

Occurrence of Natural Bacillus thuringiensis Contaminants and Residues of Bacillus thuringiensis -Based Insecticides on Fresh Fruits and Vegetables

Frederiksen¹,

Rosenquist²,

Jørgensen

et al. 2006

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A total of 128 Bacillus cereus-like strains isolated from fresh fruits and vegetables for sale in retail shops in Denmark were characterized. Of these strains, 39% (50/128) were classified as Bacillus thuringiensis on the basis of their content of cry genes determined by PCR or crystal proteins visualized by microscopy. Random amplified polymorphic DNA analysis and plasmid profiling indicated that 23 of the 50 B. thuringiensis strains were of the same subtype as B. thuringiensis strains used as commercial bioinsecticides. Fourteen isolates were indistinguishable from B. thuringiensis subsp. kurstaki HD1 present in the products Dipel, Biobit, and Foray, and nine isolates grouped with B. thuringiensis subsp. aizawai present in Turex. The commercial strains were primarily isolated from samples of tomatoes, cucumbers, and peppers. A multiplex PCR method was developed to simultaneously detect all three genes in the enterotoxin hemolysin BL (HBL) and the nonhemolytic enterotoxin (NHE), respectively. This revealed that the frequency of these enterotoxin genes was higher among the strains indistinguishable from the commercial strains than among the other B. thuringiensis and B. cereus-like strains isolated from fruits and vegetables. The same was seen for a third enterotoxin, CytK. In conclusion, the present study strongly indicates that residues of B. thuringiensis-based insecticides can be found on fresh fruits and vegetables and that these are potentially enterotoxigenic.The gram-positive spore-forming bacterium Bacillus thuringiensis is ubiquitous in the environment and is closely related to the food-borne pathogen Bacillus cereus. The only difference between the two species is the ability of B. thuringiensis to produce parasporal crystalline inclusions, the so-called crystal proteins (Cry proteins) or ␦-endotoxins, which are plasmid encoded. These toxins have highly specific activity against certain insects (6, 23), especially within the orders Lepidoptera, Diptera, and Coleoptera (11), and B. thuringiensis is therefore of commercial interest. Plant protection products based on selected strains of B. thuringiensis are used worldwide in, e.g., the production of fruits and vegetables in greenhouses and in the field.The high specificity of the Cry proteins against insects is mainly due to specific receptors in the insect gut, which are not present in the mammalian gut. These toxins are therefore considered harmless to humans. However, B. thuringiensis strains are capable of producing a variety of other toxins and virulence factors that can affect humans, including the same diarrhea-causing enterotoxins as produced by B. cereus (12,13,20). The two best-characterized enterotoxins are hemolysin BL (HBL) and nonhemolytic enterotoxin (NHE), which are both three-component toxins requiring expression of all three genes for full virulence (17,19). A third enterotoxin, cytotoxin K (CytK), is a single-component toxin once reported to be involved in a severe food poisoning case that caused the deaths of three individuals (18). H...