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The role of penicillin-induced bacterial variants in experimental pyelonephritis
Abstract:
1. After injection into the renal medulla of rats Escherichia coli 06 variants reverted rapidly in vivo in the absence of penicillin. These variants had previously been shown to be stable in vitro. 2. Variants failed to survive following intramedullary injection when animals were receiving penicillin. 3. Late reversion of variants also failed to occur in animals treated with penicillin for only 1 or 2 days. 4. Variants survived and reverted more readily when injected in the renal medulla, compared with liver and spleen. Classical bacteria injected into the kidney, liver, and spleen were recovered in approximately equal numbers. 5. The histologic response to nonreverting variants, medium not containing variants, and killed variants was similar and was characterized by a fibrotic reaction with moderate round cell infiltration. 6. In contrast, the histologic response to reverting variants and to classical E. coli was characterized by an intense, acute, polymorphonuclear leukocytosis typical of acute pyelonephritis.
Insights
Penicillin treatment prevents the rapid in vivo reversion of Escherichia coli 06 variants in rat kidneys. This finding is crucial for understanding antibiotic efficacy in treating kidney infections caused by bacterial variants.
Area of Science:
- Microbiology
- Nephrology
- Pharmacology
Background:
- Escherichia coli 06 variants exhibit in vitro stability but rapid in vivo reversion in the renal medulla.
- Understanding the behavior of bacterial variants in vivo is critical for effective antimicrobial therapy.
Purpose of the Study:
- To investigate the effect of penicillin on the in vivo reversion of Escherichia coli 06 variants in the rat renal medulla.
- To compare the survival and reversion rates of variants in different organs (renal medulla, liver, spleen).
- To characterize the host's histologic response to reverting and nonreverting bacterial variants.
Main Methods:
- Intramedullary injection of Escherichia coli 06 variants into rats.
- Administration of penicillin during and after bacterial injection.
- Histological examination of renal tissue.
- Comparison of bacterial recovery and reversion in renal medulla, liver, and spleen.
Main Results:
- Penicillin treatment inhibited the in vivo reversion of Escherichia coli 06 variants in the renal medulla.
- Variants failed to survive and revert when animals received penicillin.
- Late reversion was also prevented by short-term penicillin treatment (1-2 days).
- Variants reverted more readily in the renal medulla than in the liver or spleen.
- Histologic response to reverting variants and classical E. coli was acute pyelonephritis, while nonreverting variants induced a fibrotic reaction.
Conclusions:
- Penicillin is effective in preventing the in vivo reversion of Escherichia coli 06 variants in the kidney.
- The renal medulla is a favorable environment for variant reversion compared to the liver and spleen.
- The host's inflammatory response differs significantly between reverting and nonreverting bacterial variants, indicating distinct pathogenic mechanisms.