Super-infection by Bacillus thuringiensis H34 or 3a3b can lead to death in mice infected with the influenza A virus.
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.
Hernandez
E
E
Service de Biologie Médicale, Hôpital d'Instruction des Armées Begin, 69 Avenue de Paris, 94160 Saint-Mandé, France. hnz.eric@freesurf.fr
Ramisse
F
F
Gros
P
P
Cavallo
J
J
D000284:Administration, Oral; D000547:Amantadine / Q000008:administration & dosage / Q000627:therapeutic use; D000818:Animals; D000911:Antibodies, Monoclonal / Q000627:therapeutic use; D000998:Antiviral Agents / Q000008:administration & dosage / Q000627:therapeutic use; D016863:Bacillaceae Infections / Q000150:complications* / Q000188:drug therapy / Q000401:mortality; D001413:Bacillus thuringiensis / Q000472:pathogenicity; D005260:Female; D006801:Humans; D009980:Influenza A virus / Q000472:pathogenicity; D007251:Influenza, Human / Q000150:complications* / Q000188:drug therapy / Q000401:mortality; D008168:Lung / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D013171:Spores, Bacterial / Q000472:pathogenicity; D015163:Superinfection / Q000150:complications* / Q000188:drug therapy / Q000401:mortality
D000911:Antibodies, Monoclonal; D000998:Antiviral Agents; D000547:Amantadine