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Category: Clinical Microbiology; Bacterial Pathogenesis
Polymicrobial Bacteriuria: Biofilm Formation on Foreign Bodies and Colonization of the Urinary Tract, Page 1 of 2
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Indwelling catheters are used to control the release of urine from the bladder. Various types of stents maintain the flow of urine through the ureters and the urethra. They are not inert, however, and their surfaces are capable of physical, chemical, and biological interactions. In addition, they have none of the defense mechanisms which protect mucosal tissue surfaces from bacterial colonization. The surface irregularities common on these devices also induce the passive entrapment of bacterial cells. These foreign bodies are thus extremely vulnerable to colonization by any contaminating microbes that might be in their vicinity. If infection occurs in the first week of catheterization, it is usually caused by a single species such as Staphylococcus epidermidis, Enterococcus faecalis, or Escherichia coli. The longer the catheter remains in place, the greater the variety of organisms that accumulate in the bladder. Polymicrobial bacteriuria is thus characteristic of patients enduring longterm bladder management by indwelling catheter. Results of a study found that biofilms were visible on 46% of 72 stents, most of which had been in place for 12 weeks. Enterococci and coagulase-negative staphylococci were again reported as the organisms commonly colonizing the stents. The crystalline biofilms that form on catheters usually contain Proteus mirabilis and several other species. Vaccines have been developed against uropathogenic E. coli and shown to induce effective prophylaxis against infections in patients with “normal” urinary tracts, but whether they are capable of preventing the colonization of the catheter and the urine in the catheterized urinary tract is unknown.
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Foreign bodies that are placed in the urinary tract. (a) An unused all-silicone catheter. The retention balloon near to the tip of the catheter has been inflated, and the eyehole through which urine flows is visible. (b) A ureteral stent that had been lying in situ between a patient's kidney and bladder for 12 weeks. Encrustation is visible on the end of the stent that was lying in the bladder. Modified from reference 89 and published with permission from Elsevier BV and the International Society of Chemotherapy.
Foreign bodies that are placed in the urinary tract. (a) An unused all-silicone catheter. The retention balloon near to the tip of the catheter has been inflated, and the eyehole through which urine flows is visible. (b) A ureteral stent that had been lying in situ between a patient's kidney and bladder for 12 weeks. Encrustation is visible on the end of the stent that was lying in the bladder. Modified from reference 89 and published with permission from Elsevier BV and the International Society of Chemotherapy.
Transmission electron micrographs showing sections through a crystalline biofilm (120 μm thick) that had developed on an all-silicone catheter over 24 h in a model of the catheterized bladder. The model had been inoculated with a mixed urine culture of P. mirabilis and E. coli. (a) Boundary of the biofilm over which urine (U) has been flowing. (b) Edge of the biofilm adjacent to the silicone surface (S) of the catheter. Bacterial cells can be seen distributed throughout the ruthenium red-stained polysaccharide matrix. The unstained areas are struvite and apatite crystals. Bacteria are visible within the apatite formations. From reference 88a with permission from the European Board of Urology.
Transmission electron micrographs showing sections through a crystalline biofilm (120 μm thick) that had developed on an all-silicone catheter over 24 h in a model of the catheterized bladder. The model had been inoculated with a mixed urine culture of P. mirabilis and E. coli. (a) Boundary of the biofilm over which urine (U) has been flowing. (b) Edge of the biofilm adjacent to the silicone surface (S) of the catheter. Bacterial cells can be seen distributed throughout the ruthenium red-stained polysaccharide matrix. The unstained areas are struvite and apatite crystals. Bacteria are visible within the apatite formations. From reference 88a with permission from the European Board of Urology.
Scanning electron micrographs of a ureteral stent that had been removed from a patient after 12 weeks. (a to c) Crystalline material can be seen on the outer surface (a) and completely occluding an eyehole (b) and the central channel (c). (d) Bacteria in this crystalline material. Modified from reference 89 and published with permission from Elsevier BV and the International Society of Chemotherapy.
Scanning electron micrographs of a ureteral stent that had been removed from a patient after 12 weeks. (a to c) Crystalline material can be seen on the outer surface (a) and completely occluding an eyehole (b) and the central channel (c). (d) Bacteria in this crystalline material. Modified from reference 89 and published with permission from Elsevier BV and the International Society of Chemotherapy.
Scanning electron micrographs of a P. aeruginosa biofilm on a catheter that had been removed from a patient after 6 weeks. (a) Freeze-dried preparation of a freeze-fractured cross section of the catheter lumen. (b) Spongiform structure of the biofilm. Modified from reference 88a with permission from the European Board of Urology.
Scanning electron micrographs of a P. aeruginosa biofilm on a catheter that had been removed from a patient after 6 weeks. (a) Freeze-dried preparation of a freeze-fractured cross section of the catheter lumen. (b) Spongiform structure of the biofilm. Modified from reference 88a with permission from the European Board of Urology.
Images of a worm-like structure that blocked a patient's catheter regularly at 4-day intervals. (a) Photograph of a cut section of the catheter, revealing the “worm” that blocked the lumen. (b) Scanning electron micrograph of a freeze-dried preparation of the “worm,” showing the crystal formations of the outer surface. (c) Scanning electron micrograph of a fixed, critical-point-dried specimen, showing that beneath the crystalline coat the “worm” is composed of masses of cocci, short rods, and a tangle of very long bacilli. Modified from reference 93 with permission.
Images of a worm-like structure that blocked a patient's catheter regularly at 4-day intervals. (a) Photograph of a cut section of the catheter, revealing the “worm” that blocked the lumen. (b) Scanning electron micrograph of a freeze-dried preparation of the “worm,” showing the crystal formations of the outer surface. (c) Scanning electron micrograph of a fixed, critical-point-dried specimen, showing that beneath the crystalline coat the “worm” is composed of masses of cocci, short rods, and a tangle of very long bacilli. Modified from reference 93 with permission.
Micrograph of a P. mirabilis biofilm that had developed on a hydrogel-coated latex catheter after 20 h in a model of the catheterized bladder. Pores are visible penetrating the calcified “plaster cast” of the biofilm. Kindly provided by Rob Young, Cardiff University.
Micrograph of a P. mirabilis biofilm that had developed on a hydrogel-coated latex catheter after 20 h in a model of the catheterized bladder. Pores are visible penetrating the calcified “plaster cast” of the biofilm. Kindly provided by Rob Young, Cardiff University.
Micrographs illustrating the formation of a crystalline P. mirabilis biofilm around the eyehole of a hydrogel-coated latex catheter over a period of 20 h in a laboratory model. (a and b) Rough, irregular surface of the catheter. (c) After 2 h in the model, bacteria have adhered to the crevices in the surface. (d) After 4 h, microcolonies have developed in depressions in the surface. (e) After 6 h, amorphous crystalline material typical of apatite is associated with the cells. (f) After 20 h, extensive crystalline biofilm has formed around the eyehole. Modified from reference 97 with permission.
Micrographs illustrating the formation of a crystalline P. mirabilis biofilm around the eyehole of a hydrogel-coated latex catheter over a period of 20 h in a laboratory model. (a and b) Rough, irregular surface of the catheter. (c) After 2 h in the model, bacteria have adhered to the crevices in the surface. (d) After 4 h, microcolonies have developed in depressions in the surface. (e) After 6 h, amorphous crystalline material typical of apatite is associated with the cells. (f) After 20 h, extensive crystalline biofilm has formed around the eyehole. Modified from reference 97 with permission.
Photographs of unused catheters illustrating the narrow central channels through which the urine has to flow. (A) Silicone-coated latex catheter. (B) Hydrogel-coated latex catheter. (C) All-silicone catheter. From reference 97 with permission.
Photographs of unused catheters illustrating the narrow central channels through which the urine has to flow. (A) Silicone-coated latex catheter. (B) Hydrogel-coated latex catheter. (C) All-silicone catheter. From reference 97 with permission.
Scanning electron micrographs showing a section of hydrogel-coated latex catheter over which P. mirabilis swarmers are migrating. The section has been removed from a laboratory model. Multicellular rafts of elongated swarmer cells can be seen on the rough, irregular luminal surface of the catheter. The swarmers are migrating from left to right over the catheter. Kindly provided by Rob Broomfield, Cardiff University.
Scanning electron micrographs showing a section of hydrogel-coated latex catheter over which P. mirabilis swarmers are migrating. The section has been removed from a laboratory model. Multicellular rafts of elongated swarmer cells can be seen on the rough, irregular luminal surface of the catheter. The swarmers are migrating from left to right over the catheter. Kindly provided by Rob Broomfield, Cardiff University.