Host parasite interaction in urinary tract infection

The last decade has provided new insight into the mechanisms of host-parasite interactions in the urinary tract. Reduction of host resistance appears to reduce the requirement for bacterial virulence, whereas the resistant host becomes infected with bacteria of high virulence. In the resistant host, bacterial virulence can be defined as the sum of properties required to colonize the urinary tract and induce tissue reactions. The ability to attach to uroepithelial cells is the single property most frequently associated with pyelonephritogenic clones. Attachment to the Gal1–4Gal-containing receptors promotes localization of bacteria to the kidney and the induction of lipopolysaccharide-mediated inflammation. Other virulence factors, defined by increased frequency in acute pyelonephritis compared with asymptomatic bacteriuria, include haemolysin and aerobactin production. Among the factors which influence the natural resistance to urinary tract infection are urinary flow and reactivity to endotoxin. The resistance induced by natural exposure to infection or immunization may be protective in experimental models, but the importance of this is not yet defined. The localization, severity and sequelae of urinary tract infection are determined by the balance between bacterial virulence and host resistance. Although disease is a result of the interaction between bacterial virulence and host resistance, these components are discussed separately for clarity.     

Urinary proteins in children with urinary tract infection

The aim of this study was to test our hypothesis that the urinary excretion of C-reactive protein (CRP), alpha 1-microglobulin (A1M), retinol-binding protein (RBP) and Clara cell protein (CC16) is increased in children with urinary tract infection (UTI) and relates to renal damage as measured by acute dimercaptosuccinic acid (DMSA) scintigraphy. Fifty-two children <2 years of age with UTI were enrolled in the study, 44 of whom were febrile. The control group consisted of 23 patients with non-UTI infection and elevated serum CRP (s-CRP) levels. Thirty-six patients had abnormal DMSA uptake, classified as mild, moderate or severe damage (DMSA class 1, 2, 3, respectively). There was a significant association between DMSA class and the excretion of urinary RBP (u-RBP) and u-CC16. There was also a significant difference in u-CRP levels between children with UTI and control children with non-UTI infections, although u-CRP excretion was not significantly correlated to DMSA class. In conclusion, the urinary excretion of the low-molecular-weight proteins RBP and CC16 showed a strong association with uptake defects on renal DMSA scans. The urinary level of CRP seems to distinguish between children with UTI and other febrile conditions. A combination of these biomarkers may be useful in the clinical assessment of children with UTI.     

Urinary tract infection associated with urinary calculi. 1. The significance of urinary tract infection in urinary calculi

We investigated 158 cases of urinary stones (infection stones 56, metabolic stones 102) with special reference to pyuria, bacteriuria, stone culture and urease activities of isolated bacteria. Abacterial pyuria was noted in 9 out of 49 (18%) infection stones and in 53 of 77 (69%) metabolic stones. Bacteriuria was noted in 79% of the infection stones and 26% of the metabolic stones. Sixty-seven percent of the infection stones were infected with mainly urea splitting bacteria such as Proteus mirabilis and Staphylococcus. Twenty-three percent of metabolic stones were also infected. Though E. coli, a non-urea splitting bacteria, was isolated most frequently from metabolic stones, urease positive Staphylococcus and Pseudomonas were also isolated. Bacteria within stones could be predicted on the basis of urine culture results of only 20 of 41 infection stones and 8 of 24 metabolic stones. These facts are useful for selection of some antibiotics in the treatment of urinary tract infections associated with urinary calculi. Urinary infections of urea splitting bacteria in infection stones are thought to be initial factors of stone formation and those of non-urea splitting bacteria are to be superimposed. However, urea splitting bacteria in metabolic stones may convert them into infection stones in future.     

Mechanisms of urinary tract infection.

Most urinary tract infections begin as a cystitis secondary to decreased host resistance brought on by disruption of tissue integrity or a decrease in blood supply to the bladder. In the female, infrequent voiding and the uninhibited bladder are the most common causes of urinary tract infection and are best treated by healthy voiding regimens; while in the male, structural and functional obstructive uropathy are most often associated with urinary tract infection and are alleviated by lowering the high intravesical pressures via surgical or medical measures. The concept that host resistance is the determinant of infection rather than the organism has permitted the use of clean, intermittent self-catheterization; clean intermittent self-dilatation; and transurethral diverticulectomy in the therapy of a host of urologic disease syndromes.     

Localization of urinary tract infection.

Both the antibody-coating and LDH isoenzyme techniques theoretically fulfill the criteria for an ideal localization test. Both are noninvasive. They are relatively easy to perform and well within the capability of most clinical laboratories. Both can be done rapidly and the results can be in the clinician's hands in a matter of a few hours. The results of the antibody-coating technique do not appear to be valid for children. Since only one controlled study with comparison with other localization techniques has been done in adults, further evaluation needs to be done. The LDH isoenzyme pattern has not been studied in adults but appears to be accurate in children. A prospective comparison of both procedures in adults using either the Fairly bladder washout technique or the Stamey ureteral catheterization method to localize definitively the site of infection would be most helpful. Definitive noninvasive localization techniques could lead to therapy being initiated with the site of infection defined. This would facilitate earlier and more intensive antibiotic therapy in those patients at risk for renal parenchymal damage from upper tract infections.     

Non-invasive localization of urinary tract infection.

New methods to localize the source of bacteriuria were evaluated in monkeys with experimental urinary tract infection. A high level of diagnostic accuracy was obtained with the combined study of antibody-coated urinary bacteria by immunofluorescence, 131I hippuran scintiphotos in the hydropenic state and 67gallium citrate scintiphotos. Unique patterns were found, which differentiate cystitis, ureteritis, pyelonephritis and renal or perinephric abscesses.     

Febrile urinary tract infection: Escherichia coli susceptibility to oral antimicrobials

Empirical treatment is indicated for young children with febrile urinary tract infection (UTI). In this clinical setting, oral antibiotics are as safe and effective as intravenous therapy. The aim of this study was to investigate in children with febrile UTI whether there were longitudinal changes in the prevalence of bacteria and in the pattern of Escherichia coli susceptibility to oral antimicrobial agents. Two hundred and eighty-seven positive urine cultures from children (1 month to 12 years) with febrile UTI collected over three periods (1986–1989, 1990–1991, and 1997) were studied. E. coli was the most-prevalent microorganism in all three study-periods (n=228). The susceptibility pattern of E. coli to nitrofurantoin (92%, 95%, 94%) and nalidixic acid (85%, 92%, 95%) did not present any statistically significant differences (P>0.05) over time. There was a significant increase (P<0.05) in E. coli susceptibility to cephalexin (65%, 54%, 81%). The E. coli susceptibility to trimethoprim-sulfamethoxazole (40%, 85%, 40%) behaved differently. Initially there was a significant rise (P<0.05), followed by a significant decrease (P<0.05). Empirical oral treatment with nitrofurantoin or nalidixic acid can safely be started in children with febrile UTI seen in the Emergency Department, Hospital de Clínicas de Porto Alegre, Brazil. Received: 20 December 2000 / Revised: 26 November 2001 / Accepted: 27 November 2001     

Quantitation of urinary Tamm-Horsfall protein in children with urinary tract infection.

It has been suggested that urinary Tamm-Horsfall protein (THP) prevents colonization of the urinary tract by binding uropathogens. We tested the hypothesis that low urinary THP levels may predispose to urinary tract infection (UTI) by measuring THP levels in children. We studied a cohort of 35 girls with uncomplicated recurrent UTI (group 1) that was compared with 27 patients with myelomeningoceles undergoing clean intermittent catheterization (group 2) and 16 female controls (group 3). We measured urinary THP in both aggregated (aTHP) and disaggregated form (dTHP), leukocyte esterase activity, urine chemistries and culture. No significant differences in dTHP or aTHP levels were seen between groups 1 and 3, but group-1 patients had higher dTHP levels than group-2 patients (p < 0.008). History of reflux or the presence of bacteriuria or pyuria at the time of urine collection did not affect dTHP levels; in contrast, pyuria or bacteriuria at the time of sampling was associated with markedly lower aTHP levels when compared with sterile samples (p < 0.0001). For all groups, measured quantities of dTHP did not correlate with aTHP levels. We conclude that excretion of dTHP in children with history of recurrent UTI is not reduced. In contrast, concentrations of aTHP are profoundly depressed in children during times of UTI, suggesting a role for THP in the pathogenesis of UTI. Assaying THP in its aggregated form may prove valuable when studying its physiologic function and merits further investigation.     

尿路感染研究进展

尿路感染是威胁人类健康的常见疾病之一,大肠埃希菌是尿路感染最常见的病原。近年来,尿路感染发病机制的研究已深入到免疫学和分子生物学水平。本文就大肠埃希菌致病机制、细菌-宿主之间的相互作用、尿路感染再发机理及临床治疗方面的进展作一综述。     

Psychological factors in recurrent uncomplicated urinary tract infection.

Recurrent urinary tract infection (UTI) is a very common medical complaint among women. A large proportion of such recurrence is attributable to a small sub-group of sufferers. Medical factors have proven insufficient to explain all such cases, and a number of psychological factors have been suggested as having a causal role. This study examines the evidence for the effects of behavioural and personality factors. Neuroticism and specific "risky" behaviours are identified as particularly important, being related to both the diagnosis of recurrent UTI and the frequency of infection. These findings suggest that treatment of recurrent, intractable UTI might include a psychological component.     

尿路结构异常儿童合并泌尿系感染的病原菌分析

目的探讨尿路结构异常儿童合并泌尿系感染（UTI）致病菌的分布及药物敏感及耐药情况。 方法收集2012年1月至2016年12月中山大学附属第三医院及汕头市中心医院符合UTI住院患儿476例,分为尿路正常组及尿路异常组,比较两组间病原菌构成比及对抗菌药物的敏感和耐药情况。 结果尿路异常者162例（肾积水最为常见,占43.83%）,尿路正常儿童314例。尿路异常儿童合并感染常见于男性（P<0.05）,共检出致病菌166株,革兰氏阴性菌（G^-）为主（71.08%）,大肠埃希菌占首位（40.36%）,肠球菌属居第2位（22.89%）,粪肠球菌在尿路异常组常见（χ²=4.59,P=0.032）。两组间常见病原菌耐药性差异无统计学意义。 结论尿路结构异常男性儿童易发生泌尿系感染,且肠球菌感染的发生率高于尿路结构正常儿童。