Role of Escherichia coli adhesins in urethral colonization of catheterized patients

Effects of subinhibitory concentrations of nitroxoline on the surface properties of Escherichia coli

Nitroxoline (5-nitro-8-quinolinol; NIQ) at subinhibitory concentrations (sub-MIC) decreased the adherence of uropathogenic Escherichia coli to catheter surface and significantly enhanced cell surface hydrophobicity. The surface hydrophobicity increased in the presence of sub-MIC of NIQ and also in an excess of Mg2+. The effect of NIQ on the cell surface was not related to the bacteriostatic effect of this agent. The increase in nitrogen and decrease in phosphate content in the cell surface was found in the presence of NIQ. NIQ did not inhibit the expression of fimbriae.

Catheter-associated urinary tract infections

Millions of urethral catheters are used each year. This device subverts several host defenses to allow bacterial entry at the rate of 3% to 10% incidence per day, and its presence encourages the organism's persistent residence in the urinary tract. Most catheter-associated bacteriurias are asymptomatic. The complications in short-term catheterized patients include fever, acute pyelonephritis, bacteremia, and death; patients with long-term catheters in place are at risk for these complications and catheter obstruction, urinary tract stones, local periurinary infections, chronic renal inflammation, chronic pyelonephritis, and, over years, bladder cancer. The closed catheter system has been a magnificant step forward in the prevention of catheter-associated bacteriuria. Indeed, only two catheter principles are universally recommended: keep the closed catheter system closed and remove the catheter as soon as possible. Most modifications of the closed catheter system have not improved markedly on its ability to postpone bacteriuria. On first inspection, systemic antibiotics seem to be an exception to this rule, but their use results in infection of the bladder with resistant organisms, including candida. This and the effect of side effects on the patient and emergence of resistant bacteria in the medical unit have led most authorities to conclude that antibiotics are not useful for prevention of bacteriuria, nor for treatment of bacteriuria in the asymptomatic catheterized patient. For symptomatic patients, usually with fever or signs of sepsis, treatment of bacteriuria with appropriate systemic antibiotics and removal or replacement of the urethral catheter are indicated. Gloves, hand washing, and segregation of catheterized patients can minimize nosocomial clusters. Because clinicians can only postpone bacteriuria, and once it occurs, clinicians seem unable to prevent its complications, methodologies other than urethral catheters should be used for urine drainage assistance whenever possible. These options include condom, intermittent, suprapubic, and intraurethral catheterization for appropriate patients. The few data available suggest that each one of these catheterization options yields a lower incidence of bacteriuria-and its consequent complications-than urethral catheterization.