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Isolation of mammalian pathogenic bacteria using silkworms
1Laboratory of Microbiology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan.
Abstract:
We developed a method to predict bacterial pathogenicity against mammals by measuring bacterial virulence in silkworms at 37°C, human body temperature. One hundred and twenty-two strains of bacteria were isolated from the intestines of fish and shellfish and tested for their virulence against silkworms. Overnight cultures of 50 strains killed at least 50% of the silkworms when injected into the hemolymph. Of 10 strains that showed the most potent pathogenicity against silkworms, 8 also killed mice within 4 days after injection, including Staphylococcus simiae and Staphylococcus pasteuri, neither of which was previously reported to be pathogenic against mammals. These findings suggest that bacterial pathogenicity against mammals can be predicted based on measurements of silkworm-killing activity.
Insights
Researchers developed a novel method to predict bacterial pathogenicity in mammals using silkworm virulence assays at 37°C. This approach accurately identified potential mammalian pathogens, including previously unrecognized ones like Staphylococcus simiae.
Area of Science:
- Microbiology
- Infectious Diseases
- Animal Models
Background:
- Predicting bacterial pathogenicity against mammals is crucial for public health.
- Existing methods for assessing bacterial virulence can be time-consuming and resource-intensive.
- A rapid and reliable in vivo model is needed to screen bacterial strains for potential mammalian pathogenicity.
Purpose of the Study:
- To develop and validate a method for predicting bacterial pathogenicity in mammals.
- To utilize silkworm (Bombyx mori) virulence as a proxy for mammalian pathogenicity.
- To identify novel bacterial pathogens of mammals.
Main Methods:
- Isolated 122 bacterial strains from fish and shellfish intestines.
- Assessed bacterial virulence by injecting cultures into silkworm hemolymph at 37°C.
- Correlated silkworm lethality with mouse lethality for highly virulent strains.
Main Results:
- Fifty bacterial strains demonstrated significant lethality (>50%) in silkworms.
- Ten strains with the highest silkworm pathogenicity were further tested in mice.
- Eight of these ten strains killed mice within 4 days, including Staphylococcus simiae and Staphylococcus pasteuri, previously unreported mammalian pathogens.
Conclusions:
- Silkworm virulence assays at 37°C can effectively predict bacterial pathogenicity against mammals.
- This method offers a rapid and cost-effective approach for screening bacterial strains.
- The study identified new potential mammalian pathogens, highlighting the utility of the silkworm model.
