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Chronic pyelonephritis. Electron microscopic study. II. Persistence of variant bacterial forms
Abstract:
Ascending nonobstructive pyelonephritis was produced in nonhuman primates by ureteral catheterization which delivered Escherichia coli (04:H1) to the renal pelvis while creating intrarenal reflux. Female rhesus monkeys (Macaca mulatta) were immunosuppressed by cyclophosphamide before infection and weekly thereafter and compared to those with infection only. Kidney tissue was examined by electron microscopy in an effort to compare the development of the infection in the two groups of monkeys, i.e., immunocompetent and immunosuppressed. Reorganization of bacterial cytoplasm into small dense bodies (averaging 250 A in diameter) was seen in two of the suppressed animals. These particles were within bacteria that were either free in the medullary interstitium or in macrophages. Clusters of electron-dense bodies of the same size and morphology were also seen within subendothelial spaces of glomerular capillaries. Protoplast-like forms were observed within the medullary interstitium. One cell wall-less form contained particles (as previously described) within a large peripheral vesical. Gross pyelonephritic scarring occurred in all immunosuppressed animals. This study has shown morphologically that classical bacterial organisms placed into the intact kidneys of partially immunoincompetent nonhuman primates will cause pyelonephritis and continue to exist for 18 days. These observations of the futile efforts by suppressed populations of leukocytes to clear intrarenal bacteria raise interesting questions about the host-paradise relationship in chronic renal infection.
Insights
In immunosuppressed primates, Escherichia coli caused pyelonephritis, with bacteria persisting for 18 days. Electron microscopy revealed bacterial reorganization and cell-wall-less forms, highlighting immune system challenges in clearing kidney infections.
Area of Science:
- Nephrology
- Microbiology
- Immunology
Background:
- Ascending pyelonephritis is a significant kidney infection.
- Understanding bacterial persistence in the kidney is crucial for treatment.
- The role of the immune system in clearing renal infections requires further elucidation.
Purpose of the Study:
- To investigate the morphological changes of Escherichia coli during pyelonephritis in immunosuppressed nonhuman primates.
- To compare the development of pyelonephritis in immunocompetent versus immunosuppressed rhesus monkeys.
- To examine bacterial survival and host-pathogen interactions in the renal environment.
Main Methods:
- Induction of ascending nonobstructive pyelonephritis in female rhesus monkeys (Macaca mulatta) via ureteral catheterization with Escherichia coli (O4:H1).
- Immunosuppression of animals using cyclophosphamide.
- Examination of kidney tissue using electron microscopy to compare infected immunocompetent and immunosuppressed groups.
Main Results:
- Gross pyelonephritic scarring was observed in all immunosuppressed animals.
- Electron microscopy revealed bacterial reorganization into small dense bodies within bacteria and macrophages in immunosuppressed monkeys.
- Protoplast-like, cell wall-less bacterial forms were observed in the renal interstitium, with some containing internal particles.
- Electron-dense bodies were also found within subendothelial spaces of glomerular capillaries.
- Classical bacterial organisms persisted in the kidneys of partially immunoincompetent nonhuman primates for up to 18 days.
Conclusions:
- Morphological evidence confirms that Escherichia coli can cause pyelonephritis and persist for extended periods in immunosuppressed nonhuman primates.
- The study demonstrates the presence of unusual bacterial forms, including cell-wall-less variants, during infection.
- Observations suggest challenges faced by the host immune system, specifically leukocytes, in clearing intrarenal bacteria, raising questions about host-pathogen dynamics in chronic renal infections.