InhA1, NprA, and HlyII as Candidates for Markers To Differentiate Pathogenic from NonpathogenicBacillus cereusStrains

Cadot, Céline; Tran, Seav-Ly; Vignaud, Marie-Léone; Buyser, Marie-Laure De; Kolstø, Anne‐Brit; Brisabois, Anne; Nguyen-Thé, Christophe; Lereclus, Didier; Guinebretière, Marie-Hélène; Ramarao, Nalini

doi:10.1128/jcm.02123-09

Cited by 80 publications

(81 citation statements)

References 63 publications

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“…Regardless of the bacterial species, results obtained with Galleria larvae infected by direct injection through the cuticle consistently correlate with those of similar mammalian studies: bacterial strains that are attenuated in mammalian models demonstrate lower virulence in Galleria, and strains causing severe human infections are also highly virulent in the Galleria model [8][9][10][11] . Oral infection of Galleria is much less used and additional compounds, like specific toxins, are needed to reach mortality.…”

Section: Introductionsupporting

confidence: 69%

The Insect Galleria mellonella as a Powerful Infection Model to Investigate Bacterial Pathogenesis

Ramarao¹,

Nielsen-LeRoux²,

Lereclus³

2012

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The study of bacterial virulence often requires a suitable animal model. Mammalian models of infection are costly and may raise ethical issues. The use of insects as infection models provides a valuable alternative. Compared to other non-vertebrate model hosts such as nematodes, insects have a relatively advanced system of antimicrobial defenses and are thus more likely to produce information relevant to the mammalian infection process. Like mammals, insects possess a complex innate immune system 1 . Cells in the hemolymph are capable of phagocytosing or encapsulating microbial invaders, and humoral responses include the inducible production of lysozyme and small antibacterial peptides 2,3 . In addition, analogies are found between the epithelial cells of insect larval midguts and intestinal cells of mammalian digestive systems. Finally, several basic components essential for the bacterial infection process such as cell adhesion, resistance to antimicrobial peptides, tissue degradation and adaptation to oxidative stress are likely to be important in both insects and mammals 1 . Thus, insects are polyvalent tools for the identification and characterization of microbial virulence factors involved in mammalian infections.Larvae of the greater wax moth Galleria mellonella have been shown to provide a useful insight into the pathogenesis of a wide range of microbial infections including mammalian fungal (Fusarium oxysporum, Aspergillus fumigatus, Candida albicans) and bacterial pathogens, such as Staphylococcus aureus, Proteus vulgaris, Serratia marcescens Pseudomonas aeruginosa, Listeria monocytogenes or Enterococcus faecalis [4][5][6][7] . Regardless of the bacterial species, results obtained with Galleria larvae infected by direct injection through the cuticle consistently correlate with those of similar mammalian studies: bacterial strains that are attenuated in mammalian models demonstrate lower virulence in Galleria, and strains causing severe human infections are also highly virulent in the Galleria model [8][9][10][11] . Oral infection of Galleria is much less used and additional compounds, like specific toxins, are needed to reach mortality.G. mellonella larvae present several technical advantages: they are relatively large (last instar larvae before pupation are about 2 cm long and weight 250 mg), thus enabling the injection of defined doses of bacteria; they can be reared at various temperatures (20 °C to 30 °C) and infection studies can be conducted between 15 °C to above 37 °C 12,13 , allowing experiments that mimic a mammalian environment. In addition, insect rearing is easy and relatively cheap. Infection of the larvae allows monitoring bacterial virulence by several means, including calculation of LD 50 14 , measurement of bacterial survival 15,16 and examination of the infection process 17 . Here, we describe the rearing of the insects, covering all life stages of G. mellonella. We provide a detailed protocol of infection by two routes of inoculation: oral and intra haemocoelic. The bacterial...

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Section: Introductionsupporting

confidence: 69%

The Insect Galleria mellonella as a Powerful Infection Model to Investigate Bacterial Pathogenesis

Ramarao¹,

Nielsen-LeRoux²,

Lereclus³

2012

JoVE

Self Cite

247

233

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“…To date, the ces gene is the most relevant marker for the emetic syndrome. The toxins Nhe and HlyII have been directly or indirectly linked to the diarrheal syndrome (3,19), but they do not yet explain the pathogenicity of all strains. Some new associated virulence factors (5) have not been evaluated yet as pathogenic makers, and others are doubtlessly still unknown.…”

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Ability of Bacillus cereus Group Strains To Cause Food Poisoning Varies According to Phylogenetic Affiliation (Groups I to VII) Rather than Species Affiliation

et al. 2010

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Cytotoxic activity levels of culture filtrates and toxin distributions varied according to the phylogenetic group (I to VII) within the Bacillus cereus group, suggesting that these groups are of different clinical significance and are more suitable than species affiliations for determining food poisoning risk. A first-line, simple online tool (https://www.tools.symprevius.org/Bcereus/english.php) to assign strains to the different phylogenetic groups is presented.

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“…Hemolysin II (HlyII) of Bacillus cereus was discovered to be one of the secreted factors responsible for causing hemolysis (35). It has widespread expression among B. cereus group members (10,34) and is found with increased probability in pathogenic strains (11).…”

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confidence: 99%

Iron Regulates Expression of Bacillus cereus Hemolysin II via Global Regulator Fur

et al. 2012

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The capacity of pathogens to respond to environmental signals, such as iron concentration, is key to bacterial survival and establishment of a successful infection. Bacillus cereus is a widely distributed bacterium with distinct pathogenic properties. Hemolysin II (HlyII) is one of its pore-forming cytotoxins and has been shown to be involved in bacterial pathogenicity in a number of cell and animal models. Unlike many other B. cereus pathogenicity factors, HlyII is not regulated by pleiotropic transcriptional regulator PlcR but is controlled by its own regulator, HlyIIR. Using a combination of in vivo and in vitro techniques, we show that hlyII expression is also negatively regulated by iron by the global regulator Fur via direct interaction with the hlyII promoter. DNase I footprinting and in vitro transcription experiments indicate that Fur prevents RNA polymerase binding to the hlyII promoter. HlyII expression profiles demonstrate that both HlyIIR and Fur regulate HlyII expression in a concerted fashion, with the effect of Fur being maximal in the early stages of bacterial growth. In sum, these results show that Fur serves as a transcriptional repressor for hlyII expression.

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InhA1, NprA, and HlyII as Candidates for Markers To Differentiate Pathogenic from NonpathogenicBacillus cereusStrains

Cited by 80 publications

References 63 publications

The Insect <em>Galleria mellonella</em> as a Powerful Infection Model to Investigate Bacterial Pathogenesis

The Insect <em>Galleria mellonella</em> as a Powerful Infection Model to Investigate Bacterial Pathogenesis

Ability of Bacillus cereus Group Strains To Cause Food Poisoning Varies According to Phylogenetic Affiliation (Groups I to VII) Rather than Species Affiliation

Iron Regulates Expression of Bacillus cereus Hemolysin II via Global Regulator Fur

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