In defence of Bacillus thuringiensis, the safest and most successful microbial insecticide available to humanity—a response to EFSA

Abstract

The Bacillus cereus group contains vertebrate pathogens such as B. anthracis and B. cereus and the invertebrate pathogen B. thuringiensis (Bt). Microbial biopesticides based on Bt are widely recognised as being among the safest and least environmentally damaging insecticidal products available. Nevertheless, a recent food-poisoning incident prompted a European Food Safety Authority review which argued that Bt poses a health risk equivalent to B. cereus, a causative agent of diarrhoea. However, a critical examination of available data, and this latest incident, provides no solid evidence that Bt causes diarrhoea. Although relatively high levels of B. cereus-like spores can occur in foods, genotyping demonstrates that these are predominantly naturally occurring strains rather than biopesticides. Moreover, MLST genotyping of >2000 isolates show that biopesticide genotypes have never been isolated from any clinical infection. MLST data demonstrate that B. cereus group is heterogeneous and formed of distinct clades with substantial differences in biology, ecology and host association. The group posing the greatest risk (the anthracis clade) is distantly related to the clade containing all biopesticides. These recent data support the long-held view that Bt and especially the strains used in Bt biopesticides are very safe for humans.

Lineage‐specific plasmid acquisition and the evolution of specialized pathogens in Bacillus thuringiensis and the Bacillus cereus group

“…The high cost of Cry toxin production and specialization to invertebrate hosts could explain the excellent safety record of Bt ‐based biopesticides. Despite their close phylogenetic relationship to Bc isolates capable of causing diarrhoea (Raymond & Federici, ; Raymond, Johnston, et al., ; Raymond, Wyres, et al., ), growth in the vertebrate gut and vegetative production of enterotoxins are required for diarrhoeal food poisoning (Ceuppens et al., ), and production of Cry toxins is likely to hamper vegetative outgrowth considerably.…”

“…Unsurprisingly, Bt is not a monophyletic group, and several divergent clades defined by multilocus sequence typing (MLST) or genomic data contain Bt isolates with Cry inclusions (Raymond, Wyres, et al., ). The taxonomy of the B. cereus group , and of Bt within it, is controversial, while accurate and informative species delineation has important economic implications (EFSA , Raymond & Federici, ). The licensing and “safe” status of Bt as a biological control agent that can be applied to vegetable crops are partly dependent on its biological distinctiveness from human pathogenic Bc and Ba .…”

“…The licensing and “safe” status of Bt as a biological control agent that can be applied to vegetable crops are partly dependent on its biological distinctiveness from human pathogenic Bc and Ba . Although Bt ‐based products are considered to be among the safest insecticides on the market (Federici & Siegel, ; Siegel, ), this reputation can be damaged by uncertain taxonomy and lack of rigour in interpreting epidemiological evidence (Raymond & Federici, ). Moreover, the possible horizontal mobility of virulence factors from vertebrate pathogens within the B. cereus group to invertebrate pest control agents also has potential safety implications for the use of Bt in biocontrol (EFSA ).…”

Plant Growth Promoting Rhizobacteria (PGPR) and Plutella xylostella (L.) (Lepidoptera: Plutellidae) interaction as a resistance inductor factor in Brassica oleracea var. capitata

“…For example, Bt plants are capable of producing proteins from the insecticidal bacteria, Bacillus thuringiensis (Bt), that creates resistance to attacks from specific pests. Studies with Bt plants have been conducted for half a century, and demonstrated that they are efficient biopesticides and are harmless to humans and the environment (6). However, the products based on Bt are not prominent in the insecticide market, principally due to problems with the loss of stability, the absence of translocation in the plants, the limited action spectrum and their rapid degradation due to ultra-violet light.…”

Biofilm Formation in Bacillus cereus, B. licheniformis and B. pumilus: An Alternative for Survival in Impacted Environments

“…Aerobic or facultative anaerobic, catalase-positive and sporeproducing Gram-positive bacteria represent this genus, which may be present in both aquatic and terrestrial environments. It includes species of ecological importance, such as B. thuringiensis (Raymond and Federici, 2017) and medical relevance, for example, B. antracis (Banada et al, 2017) and B. cereus (Owusu-Kwarteng et al, 2017). This genus also includes B. pumilus and B. licheniformis, being the last increasingly recognized as a human pathogen, causing serious infections in immunocompromised patients, food poisoning and ocular infections (Mohapatra and La Dut, 2012).…”