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Effect of growth temperature on complement-mediated killing of mesophilic Aeromonas spp. serotype O:34
S Merino1, D Alvarez, S Hernández-Allés
1Departamento de Microbiología, Facultad de Biología, Universidad de Barcelona, Spain.
Abstract:
Mesophilic Aeromonas spp. strains (serotype O:34) showed sensitivity to complement-mediated killing when they were cultivated at 37 degrees C (serum-sensitive) but not when they were cultivated at 20 degrees C (serum-resistant). These strains produced smooth lipopolysaccharide when they were grown at 20 degrees C and rough lipolysaccharide when cultivated at 37 degrees C. The reason for the resistance to complement-mediated killing could be that C3b is rapidly degraded (possibly because it is bound far from the cell membrane), consequently the lytic complex (C5b-9) is not formed.
Insights
Aeromonas O:34 strains are serum-resistant at 20°C and serum-sensitive at 37°C due to changes in lipopolysaccharide structure affecting complement-mediated killing. This impacts bacterial survival and immune evasion strategies.
Area of Science:
- Microbiology
- Immunology
- Bacterial Pathogenesis
Background:
- Mesophilic Aeromonas spp. are opportunistic pathogens.
- Complement-mediated killing is a key host defense mechanism against bacterial infections.
- Bacterial surface structures, such as lipopolysaccharides (LPS), can influence complement resistance.
Purpose of the Study:
- To investigate the differential susceptibility of Aeromonas spp. (serotype O:34) to complement-mediated killing based on cultivation temperature.
- To determine the role of lipopolysaccharide structure in temperature-dependent serum resistance.
Main Methods:
- Cultivation of Aeromonas spp. (serotype O:34) at 20°C (serum-resistant) and 37°C (serum-sensitive).
- Assessment of bacterial sensitivity to complement-mediated killing using serum.
- Analysis of lipopolysaccharide structure (smooth vs. rough) under different cultivation conditions.
Main Results:
- Aeromonas O:34 strains exhibited serum resistance when grown at 20°C and serum sensitivity when grown at 37°C.
- Smooth lipopolysaccharide was produced at 20°C, while rough lipopolysaccharide was observed at 37°C.
- Resistance to complement may be due to rapid degradation of complement component C3b, preventing the formation of the terminal complement complex (C5b-9).
Conclusions:
- Cultivation temperature significantly impacts the serum resistance of Aeromonas O:34 strains.
- Lipopolysaccharide structure variation (smooth vs. rough) is associated with temperature-dependent serum resistance.
- Impaired complement activation, potentially via C3b degradation, contributes to serum resistance in Aeromonas O:34.