Super-infection byBacillus thuringiensisH34 or 3a3b can lead to death in mice infected with the influenza A virus

Abstract

Bacterial super-infections are the main cause of complication and mortality after influenza virus (IAV) infection. Since Bacillus thuringiensis (Bt) is considered non-pathogenic for humans and is widely sprayed in urban areas, the aim of this work was to evaluate the potential pathogenicity of a combined infection Bt-IAV in a mouse model of pneumonia. Bacteria used for super-infections were Bt serotype H34 isolated from human infection and the insecticidal strain 3a3b obtained from a commercial source. Virus strain was A/Scotland/20/74 (H3N2) adapted to BALB/c mice by serial lung passage. Combined infection with 4% of the viral lethal dose 50% (LD(50)) and 10(2) spores of Bt H34 killed 40% of the mice. Mortality rates increased up to 55% and 100% when combined infections were done with respectively 10(4) and 10(7) spores. The insecticidal strain Bt 3a3b was less pathogenic than Bt H34. A dose of 10(4) spores associated with 4% of IAV LD(50) killed 50% of the mice. This inoculum must be compared with the doses usually sprayed in agriculture: 10(11) spores m(-2). Total protection against super-infection was obtained when mice were treated with amantadine. Even if only a few cases of Bt human infection have been reported, these results suggest a possible risk for workers spraying Bt-based biopesticides during flu outbreaks.

Bacillus thuringiensis beyond insect biocontrol: plant growth promotion and biosafety of polyvalent strains

“…In addition, two other pathogenic isolates, B. cereus Zebra Killer (ZK) and B. thuringiensis 97-27 (subsp. konkukian (serotype H34)) (Hernandez et al, 1998(Hernandez et al, , 1999(Hernandez et al, , 2000 were shown, together with B. cereus G9241, to be closely related to B. anthracis based on phylogenetic analysis using AFLP and MLST (Hill et al, 2004). The proteome of all three isolates show a higher similarity to that of B. anthracis than to that of the non-pathogenic B. cereus ATCC 14579 (Rasko et al, 2005 and references therein).…”

Contaminated feed-borne Bacillus cereus aggravates respiratory distress post avian influenza virus H9N2 infection by inducing pneumonia

“…Main cause of complications and mortality following an avian influenza virus attack, are the secondary bacterial infections. Combined infection with influenza A virus from human infection (4% of the viral lethal dose 50%) and Bacillus thuringiensis (10 7 spores) from a commercial source leading to 100% mortality in mice indicates that non-pathogenic Bacillus species will pose a high risk during bird flu outbreak 15 .…”

The Bacillus cereus Group: Bacillus Species with Pathogenic Potential

“…The opportunistic properties of B. thuringiensis and B. cereus have been investigated using nasal instillation in mice (243, 244) and intraocular infection in mice and rabbits (245). In all the cases, the results highlight the importance of the PlcR regulon in the pathogenic properties of these bacteria.…”