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Virulence of Escherichia coli in experimental hematogenous pyelonephritis in mice
Abstract:
Differences in nephropathogenicity between Escherichia coli strains were studied by following the kinetics of the viable count in the mouse kidney during 8 h after intravenous injection. Assuming as a reference point that at zero time 0.1% of the inoculum was lodged in the kidney, we found that strains fell into three main groups with different behavior patterns: in group I, the viable count fell and remained low; in group II, the viable count first fell and then rose after 4 h, reaching the level of the reference point within 8 h; in group III, the viable count rose rapidly and remained high. The kinetics of the viable counts were also studied in blood, spleen, and liver: group I and II strains behaved similarly; only in the kidney did group II strains show higher counts than group I strains. These data suggest that group II strains are specifically virulent for the mouse kidney. Group III strains also gave higher viable counts in blood and spleen but comparable counts in the liver, suggesting that group III strains are more generally virulent. Fifty percent lethal dose measurements confirmed the conclusion that group I strains are avirulent and group III strains are the most virulent. Possible relationships between behavior pattern and serotype are discussed.
Insights
This study categorizes Escherichia coli strains into three groups based on their kidney colonization patterns in mice. Group II strains show specific virulence for the mouse kidney, while Group III strains exhibit broader systemic virulence.
Area of Science:
- Microbiology
- Pathogenesis
- Immunology
Background:
- Escherichia coli (E. coli) can cause various infections, including kidney infections (nephropathogenicity).
- Understanding the virulence factors and pathogenic mechanisms of different E. coli strains is crucial for developing effective treatments and prevention strategies.
- Assessing bacterial kinetics within host organs provides insights into infection progression and organ-specific tropism.
Purpose of the Study:
- To investigate and differentiate the nephropathogenicity of various Escherichia coli strains in a murine model.
- To characterize the dynamic behavior of E. coli populations within the mouse kidney post-infection.
- To correlate bacterial kinetics with overall virulence and identify strain-specific pathogenic profiles.
Main Methods:
- Intravenous injection of Escherichia coli strains into mice.
- Monitoring the kinetics of viable bacterial counts in the kidney, blood, spleen, and liver over an 8-hour period.
- Determining the 50% lethal dose (LD50) for different bacterial groups.
Main Results:
- Escherichia coli strains were classified into three groups based on kidney viable counts: Group I (declining counts), Group II (initial decline followed by increase), and Group III (rapid increase and sustained high counts).
- Group II strains exhibited higher kidney counts compared to Group I, suggesting specific kidney tropism.
- Group III strains showed increased counts in blood and spleen, indicating general systemic virulence, while Group I strains were avirulent and Group III strains were highly virulent based on LD50.
Conclusions:
- Escherichia coli strains display distinct nephropathogenic behaviors, with Group II strains showing specific virulence for the mouse kidney.
- Group III strains demonstrate a more generalized virulence affecting multiple organs.
- The study provides a framework for classifying E. coli virulence based on kinetic patterns in host tissues.