This study established a rat model of foreign body-associated urinary tract infection. A spiral polyethylene tube (PT) was placed transurethrally into the bladder without surgical manipulation, followed by transurethral inoculation with Pseudomonas aeruginosa. The persistence of P. aeruginosa in the kidneys and bladder was significantly enhanced by placement of the PT, whereas the bacteria were eliminated rapidly from the urinary tract in the animals without the PT. Scanning electron microscopy revealed a thick biofilm on the surface of the PT from the early stage of infection. Histopathologically, acute pyelonephritis was followed by chronic renal inflammation as well as continuous and sporadic polymorphonuclear leukocyte accumulation and hemorrhage in the pelvis and adjacent tissues, suggesting continuous ascending introduction of the bacteria from the biofilm adhering to the PT. We believe our model simulates the pathophysiology of foreign body-associated urinary tract infection characterized by biofilm formation on the surface of a foreign body.Key words: Rat model, Pseudomonas aeruginosa, Urinary tract infection, Foreign body-associated UTI Urinary tract infections (UTI) associated with foreign bodies including urinary catheters and/or stents are some of the most common and problematic of hospitalacquired infections (3, 16). Typically, the biofilm mode of bacterial growth on the surface of the urinary catheter and adjacent mucosa accounts for the pathophysiology of foreign body-associated UTI (6-8). The role of bacterial biofilms on the surface of urinary catheters in UTI has been studied in rabbit models (5, 13). To determine the pathogenesis of foreign body-associated UTI in terms of its immunological and bacteriological aspects, numerous efforts have been made to establish rodent models of foreign body-associated UTI. These include models in which UTI was induced by placement of foreign bodies, such as glass beads (I), zinc rings (10, 12, 15), catheter segments (4), sutures (11), and polyurethane sponges, into the bladder (9). These models, however, have had few clinical parallels mainly because surgical manipulation to implant the foreign body into the bladder could not be avoided. Surgical incision of the bladder
A strain of Streptococcus pneumoniae, when inoculated intranasally in 2 μl of suspension into BALB/c mice preinfected with influenza virus, colonized first in the nose, and several days thereafter also colonized significantly in the trachea and lungs with purulent inflammation. Pneumoccocal colonization was also observed in the noses of normal mice after the same bacterial inoculation, but not apparently in the lower respiratory tract. These results suggest that pneumococcal infection may develop from the upper to the lower respiratory tract as a possible sequence preferentially in influenza virus‐infected subjects.
The pathogenesis of infection in mice with herpes simplex virus type 1 (HSV-1) strain 7401H was studied. Mice immunosuppressed by intraperitoneal injection of cyclophosphamide were inoculated cutaneously into the flank with the virus and developed severe zosteriform skin lesions. All of them died within 2 weeks after the infection, while most of the normal mice survived the viral infection with healing of the lesions. In the gastrointestinal tract of the immunosuppressed mice, macroscopic abnormalities were frequently observed, and infectious viruses were detected on days 7 to 9. The viruses were also detectable in the dorsal root ganglia and the spinal cord of thoracolumbar area on days 5 to 7, and in the celiac plexus on day 7. However, no viruses were detected in the blood. Immunohistological examination of the gastrointestinal tract revealed that the viral antigens were localized in Auerbach's myenteric plexus. These results suggest that HSV-1 inoculated into the flank skin invaded the gastrointestinal tract via the nervous system, which gastrointestinal involvement might possibly have caused the death of the mice.
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