Bacillus thuringiensis pulmonary infection: critical role for bacterial membrane-damaging toxins and host neutrophils

Emilia Ghelardi, Francesco Celandroni, Sara Salvetti, Ersilia Fiscarelli, Sonia Senesi

Research output: Contribution to journalArticlepeer-review


The occurrence of Bacillus thuringiensis bacteremia in a neutropenic patient suffering from severe pulmonary disease addressed the question of whether the aggressive behavior of B. thuringiensis depended on the host status and/or on the membrane-damaging toxins the isolate produced. After intratracheal injection, BALB/c mice developed pneumonia followed by fatal dissemination into deep organs, with mice rendered neutropenic by cyclophosphamide injection being extremely more susceptible to infection than normal animals. In animals infected with isogenic strains of B. thuringiensis progressively more defective in membrane-damaging toxins (407 Cry- > IP2 > MP02), an increase in the 50% lethal dose was registered (3.9 × 105, 1.1 × 106, 1.2 × 107 CFU). Consistently, after non-lethal dose application, only 407 Cry- replicated intrapulmonary, reaching a bacterial burden 4.7-fold and 40.9-fold higher than IP2 (P = 0.018) and MP02 (P = 0.008) at 48 h post-inoculation. Notably, the time-course of infection was similar in animals infected with viable bacilli or spores, with neutropenic mice always being more susceptible to infection. The overall results indicate that B. thuringiensis may be responsible for opportunistic infections and strongly suggest that membrane-damaging toxins contribute to intrapulmonary bacterial persistence favoring dissemination.

Original languageEnglish
Pages (from-to)591-598
Number of pages8
JournalMicrobes and Infection
Issue number5
Publication statusPublished - Apr 2007


  • Bacillus thuringiensis
  • Bacterial membrane-damaging toxins
  • Hemolysin BL
  • Isogenic B. thuringiensis mutants
  • Murine pulmonary infection
  • Neutropenic mice
  • Phospholipase

ASJC Scopus subject areas

  • Microbiology
  • Infectious Diseases


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