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1.
J Med Microbiol ; 58(Pt 10): 1367-1375, 2009 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-19556373

RESUMO

The problem of catheter encrustation stems from infection by urease-producing bacteria. These organisms generate ammonia from urea, elevate the pH of urine and cause crystals of calcium and magnesium phosphates to form in the urine and the biofilm that develops on the catheter. In this study, a laboratory model was used to compare the ability of 12 urease-positive species of urinary tract pathogens to encrust and block catheters. Proteus mirabilis, Proteus vulgaris and Providencia rettgeri were able to raise the urinary pH above 8.3 and produce catheter-blocking crystalline biofilms within 40 h. Morganella morganii and Staphylococcus aureus elevated the pH of urine to 7.4 and 6.9, respectively, and caused some crystal deposition in the biofilms but did not block catheters in the 96 h experimental period. Isolates of Klebsiella pneumoniae, Klebsiella oxytoca, Enterobacter cloacae, Serratia marcescens, Pseudomonas aeruginosa and Providencia stuartii were only capable of raising the pH of urine to a maximum of 6.4 and failed to cause crystal deposition in the biofilm. The most effective way to prevent catheter encrustation was shown to be diluting urine and increasing its citrate concentration. This strategy raises the nucleation pH (pH(n)) at which calcium and magnesium phosphates crystallize from urine. Increasing the fluid intake of a healthy volunteer with citrated drinks resulted in urine with a pH(n) of >8.0 in which catheter encrustation was inhibited. It is suggested that this dietary strategy will be an effective means of controlling catheter encrustation, whichever bacterial species is causing the problem.


Assuntos
Biofilmes/crescimento & desenvolvimento , Infecções Relacionadas a Cateter/microbiologia , Infecções Relacionadas a Cateter/prevenção & controle , Cateterismo Urinário/efeitos adversos , Fenômenos Fisiológicos Bacterianos , Ácido Cítrico/administração & dosagem , Ácido Cítrico/urina , Cristalização , Infecções por Enterobacteriaceae/etiologia , Infecções por Enterobacteriaceae/microbiologia , Infecções por Enterobacteriaceae/prevenção & controle , Humanos , Concentração de Íons de Hidrogênio , Técnicas In Vitro , Microscopia Eletrônica de Varredura , Modelos Biológicos , Infecções por Proteus/etiologia , Infecções por Proteus/microbiologia , Infecções por Proteus/prevenção & controle , Proteus mirabilis/patogenicidade , Proteus mirabilis/fisiologia , Proteus vulgaris/patogenicidade , Proteus vulgaris/fisiologia , Providencia/patogenicidade , Providencia/fisiologia , Urease/biossíntese , Infecções Urinárias/etiologia , Infecções Urinárias/microbiologia , Infecções Urinárias/prevenção & controle , Urina/química , Urina/microbiologia
2.
Urol Res ; 37(2): 89-93, 2009 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-19189089

RESUMO

The aim of this study was to examine the structure of the crystalline bacterial biofilms that encrust and block silver/hydrogel-coated latex catheters. Scanning electron microscopy was used to examine the crystalline deposits that were found encrusting catheters obtained from six patients undergoing long-term catheterization in a community setting. Large populations of bacilli and cocci were seen on all catheters developing on a basal foundation layer of crystalline material. These observations show that in patients prone to catheter encrustation, crystalline material formed in the urine can cover the surfaces of silver catheters. Extensive bacterial biofilms then develop on the crystals, shielded from the underlying silver. It is suggested that if antimicrobials are to be incorporated into catheters to prevent encrustation, they must diffuse out from the catheter surface and reduce the viable cell populations of the urease producing bacteria that elevate the urinary pH and trigger crystal formation.


Assuntos
Fenômenos Fisiológicos Bacterianos , Biofilmes/crescimento & desenvolvimento , Cateterismo Urinário/efeitos adversos , Cateterismo Urinário/instrumentação , Bactérias/ultraestrutura , Materiais Revestidos Biocompatíveis , Cristalização , Humanos , Hidrogéis , Microscopia Eletrônica de Varredura , Proteus mirabilis/fisiologia , Proteus mirabilis/ultraestrutura , Prata
3.
J Med Microbiol ; 55(Pt 5): 489-494, 2006 May.
Artigo em Inglês | MEDLINE | ID: mdl-16585633

RESUMO

The crystalline biofilms formed by Proteus mirabilis can seriously complicate the care of patients undergoing long-term bladder catheterization. The generation of alkaline urine by the bacterial urease causes calcium and magnesium phosphates to precipitate from urine and accumulate in the catheter biofilm, blocking the flow of urine from the bladder. The pH at which these salts crystallize from a urine sample, the nucleation pH (pH(n)), can be elevated by diluting the urine and by increasing its citrate content. The aim of this study was to examine whether manipulation of pH(n) in these ways modulated the rate at which crystalline biofilm developed. Experiments in laboratory models of the catheterized bladder infected with P. mirabilis showed that when the bladder was supplied with a concentrated urine (pH(n) 6.7) at a low fluid output (720 ml per 24 h), catheters blocked at 19-31 h. Diluting this urine 1:4 increased the pH(n) to 7.5 and models supplied with this urine at 2880 ml per 24 h took 110-137 h to block. When models were supplied with urine containing citrate at 1.5 mg ml(-1) or above (pH(n) 8.3-9.1), the catheters drained freely for the full 7 day experimental period. Scanning electron microscopy revealed that the catheter biofilms that developed in urine with high pH(n) values were devoid of crystalline formations. These observations should encourage a clinical trial to examine the effect of increasing a patient's fluid intake with citrate-containing drinks on the encrustation and blockage of catheters.


Assuntos
Biofilmes/crescimento & desenvolvimento , Cateterismo , Citratos/urina , Proteus mirabilis/fisiologia , Cateterismo Urinário , Compostos de Cálcio/metabolismo , Cristalização , Humanos , Concentração de Íons de Hidrogênio , Compostos de Magnésio/metabolismo , Microscopia Eletrônica de Varredura , Modelos Biológicos , Proteus mirabilis/metabolismo , Fatores de Tempo , Urina/química , Urina/microbiologia
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