Urinary calculi and urinary tract infection. A clinical and microbiological study

Abstract

The problem of urinary calculi in association with urinary tract infection (UTI) was investigated. Fifty-two (7%) of 796 patients attending our outpatient stone clinic had UTI which was considered of pathogenic importance for their stone formation. Proteus was the most common microorganism. Metabolic disorders were found in one third and anatomical and functional abnormalities in two thirds of the patients. The infected patients had lower urinary calcium excretion and higher serum creatinine than idiopathic stone formers and had a higher frequency of stone operations. The prevalence of staghorn calculi as a cause of urimia was low (1.5% of 481 dialysis patients). Eight such patients were studied and six of them had metabolic and anatomical disorders. The time taken for the uremia to develop was 7.4 +/- 2.0 (SD) years. In 535 patients treated surgically for renal calculi, about one third had positive urine culture at the time of operation and E. coli was the most common bacterial strain (35%). Proteus was found in 28% and these patients had the highest frequency of UTI episodes, most of which occurred before hospitalization. Patients infected with E. coli had a higher frequency of phosphate-containing calculi than non-infected patients, in whom the highest frequency of calcium oxalate calculi was found. A new broad-spectrum cephalosporin, ceftazidime, was used as perioperative prophylaxis in 15 patients operated upon for renal calculi and UTI. Ten had bacterial growth in the renal pelvis and all strains were eradicated. Bacterial growth was found in two out of six cultured stones from patients with bacterial growth in the pelvis. The pharmacokinetics of the drug was studied and the decreases in the ceftazidime levels in serum and renal tissue seemed to be parallel. Bacterial binding of urinary isolates to hydroxyapatite (HAP) particles was studied. Two E. coli strains (A5089 and E7704) and one Proteus mirabilis strain (A5076), all obtained from stone patients, were compared with two E. coli strains (2683 and M7810) with well defined cell-surface properties. Hemagglutination tests were performed and the cell-surface hydrophobicity was determined by a salt-aggregating test. When the strains were cultured at 37 degrees C to promote fimbriae formation they hemagglutinated erythrocytes and displayed hydrophobic cell-surface properties, and showed higher capacity for binding to HAP than when cultured at 18 degrees C to suppress fimbriae formation, when they showed almost complete absence of hemagglutination and low cell-surface hydrophobicity. Bacterial cell-surface properties seem to influence the binding of uropathogens to HAP particles.