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The Pathogenicity of Serratia Strains to Lucilia sericata (Diptera: Calliphoridae)
1AgResearch, Lincoln, Canterbury, New Zealand
Abstract:
Adult blowflies, Lucilia sericata, were tested for susceptibility to 11 strains of Serratia marcescens, 2 strains of Serratia liquefaciens, and 1 strain of Serratia entomophila in a series of 14 laboratory bioassays. Most bacterial strains were initially isolated from insects. S. marcescens strains were characterized to biotype level. Most strains conformed to biotype A2a, the group most commonly associated with insects. Flies were held individually in small tubes and fed bacterial suspensions containing approximately 1 x 10(9) bacteria ml-1 in a single 24-hr feeding period. For the remainder of the experiment, flies were fed sucrose solution. Eight of the S. marcescens strains caused significant mortality (P < 0.05-0.001), measured as death rate compared to untreated flies. Four strains had no effect on the flies (P > 0.05). The time taken to reach 50% mortality (LT50) ranged from 6.38 to 7.49 days for the pathogenic S. marcescens strains compared to LT50s of 8.81-11.73 days for the nonpathogenic strains, which did not differ significantly from the untreated control flies (LT50 of 10.38 days). After 7 days, mortality caused by the pathogenic strains ranged from 21 to 45% of treated insects. One strain of S. liquefaciens also caused significant mortality while the other was nonpathogenic. No mortality resulted from treatment of flies with S. entomophila.
Insights
Certain Serratia marcescens strains are pathogenic to blowflies (Lucilia sericata), causing significant mortality in laboratory bioassays. Other Serratia species tested showed varying levels of pathogenicity.
Area of Science:
- Medical Entomology
- Microbiology
- Insect Pathology
Background:
- Blowflies (Lucilia sericata) are important in forensic entomology and disease transmission.
- Serratia species are common insect symbionts and opportunistic pathogens.
Purpose of the Study:
- To assess the pathogenicity of various Serratia species and strains against adult blowflies.
- To identify specific Serratia strains that cause mortality in Lucilia sericata.
Main Methods:
- Laboratory bioassays were conducted using 14 different Serratia strains (S. marcescens, S. liquefaciens, S. entomophila).
- Adult blowflies were fed bacterial suspensions (approx. 1 x 10(9) bacteria/ml) for 24 hours.
- Mortality rates and time to 50% mortality (LT50) were recorded and compared to controls.
Main Results:
- Eight of eleven Serratia marcescens strains caused significant blowfly mortality (21-45% after 7 days).
- Pathogenic S. marcescens strains reduced LT50 values compared to nonpathogenic strains and controls.
- One Serratia liquefaciens strain was pathogenic, while another and Serratia entomophila were not.
Conclusions:
- Specific strains of Serratia marcescens exhibit pathogenicity towards adult blowflies.
- These findings contribute to understanding insect-microbe interactions and potential biocontrol agents.