title: Persistence of Bacillus thuringiensis israelensis (Bti) in the environment induces resistance to multiple Bti toxins in mosquitoes.
abstract: BACKGROUND
  The simultaneous production of six different toxins by Bacillus thuringiensis israelensis (Bti) is thought to delay the evolution of resistance in treated mosquito populations. Recent studies have shown that Bti can persist and proliferate in the environment, thereby imposing continuous selective pressure on mosquito populations, raising concerns about the long-term effectiveness of this bioinsecticide. In order to evaluate the effect of Bti persistence on the evolution of resistance, the authors selected a laboratory Aedes aegypti L. strain with field-collected leaf litter containing Bti toxins.
  
  
  RESULTS
  It is shown that resistance to each individual Bti toxin (up to 30-fold) can be obtained after only a few generations of selection. However, the resistance to commercial Bti and to environmental Bti remains low (twofold and 3.4-fold respectively) in the selected strain. Furthermore, some selected individuals exhibited resistance to Cry4B but not to Cry4A, suggesting that two distinct resistance mechanisms are involved in the resistance to these two toxins.
  
  
  CONCLUSIONS
  Considering that resistance to Cry toxins might act as a first step to resistance to a complete Bti toxin mixture, the present results highlight the importance of testing each toxin individually in order accurately to monitor Bti toxin resistance evolution in field populations.
authors.affiliation: Laboratoire d'Ecologie Alpine, UMR 5553 CNRS-Université de Grenoble, Grenoble, France.
authors.forename: Margot
authors.initials: M
authors.lastname: Paris
authors.forename: Guillaume
authors.initials: G
authors.lastname: Tetreau
authors.forename: Fabien
authors.initials: F
authors.lastname: Laurent
authors.forename: Maud
authors.initials: M
authors.lastname: Lelu
authors.forename: Laurence
authors.initials: L
authors.lastname: Despres
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: David
mesh_terms: D000818:Animals; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000494:pharmacology*; D005075:Biological Evolution; D009033:Culicidae / Q000187:drug effects* / Q000254:growth & development; D004731:Endotoxins / Q000494:pharmacology*; D004781:Environmental Exposure; D006460:Hemolysin Proteins / Q000494:pharmacology*; D007305:Insecticide Resistance / Q000187:drug effects*; D007814:Larva / Q000187:drug effects / Q000254:growth & development; D010572:Pest Control, Biological / Q000379:methods; D012641:Selection, Genetic; D013997:Time Factors
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis