Dr Operon-Associated Invasiveness of Escherichia coli from Pregnant Patients with Pyelonephritis

Abstract

We used a gentamicin protection assay to assess the ability of gestational pyelonephritis isolates of Escherichia coli to invade HeLa cells. The ability to enter HeLa cells was strongly associated with the presence of Dr operons coding for Dr adhesins. In contrast, the nonivasive isolates predominantly expressed papG, coding for P fimbriae.Pyelonephritis in pregnant patients is a serious complication that may lead to severe sequelae such as bacteremia, urosepsis, adult respiratory distress syndrome, and death (16). The course of the pregnancy may be affected, resulting in preterm labor or intrauterine growth retardation (2). Escherichia coli remains the primary cause of renal infections in pregnant patients, accounting for 65 to 80% of cases (11). E. coli strains isolated from pregnant women with pyelonephritis are genetically closely related and express gestational age-dependent profiles of virulence factors such as Dr and P fimbriae (7, 13). Interaction of recombinant E. coli bearing Dr adhesin with receptor decay-accelerating factor (DAF; CD55) on HeLa cells mediates bacterial invasion into epithelial cells (6). Moreover, Dr-positive E. coli is able to kill pregnant rats while not affecting nonpregnant animals (12). Mutation of the E. coli Dr operon results in abolishment of bacterial invasion and abrogates the development of experimental chronic interstitial nephritis in mice (5). Our general hypothesis is that an experimental lethality of Dr-positive E. coli for pregnant animals may account for their epidemiological association with pyelonephritis in pregnant patients and suggest unique gestational virulence. In this report, we evaluated the hypothesis that expression of the Dr family of adhesins in clinical gestational isolates of E. coli is associated with invasive properties. We also assessed whether other common virulence traits encountered in uropathogenic E. coli, such as P fimbriae and ␣-hemolysin, may be associated with bacterial entry into HeLa epithelial cells.In the first set of experiments, we tested the invasive properties of 73 gestational isolates of E. coli derived from pregnant patients hospitalized due to pyelonephritis at the University of Texas Medical Branch at Galveston between 1996 and 1999. Strains were selected on the basis of a positive urine culture and clinical symptoms. The standard gentamicin protection assay was performed on human cervical cell line HeLa (ATCC CCL2) as described previously to evaluate the ability of E. coli isolates to enter epithelial cells (6). The invasion rate was expressed as the percentage of the initial bacterial inoculum (1.36 ϫ 10 8 ) that was recovered after treatment of the HeLa cell monolayer with antibiotic and subsequent lysis with detergent. Isolates which yielded fewer than 0.001% survivors were characterized as noninvasive. This criterion is based on our previous studies, which revealed that a survival rate of Ͻ0.001% characterized Dr-negative mutants of clinical or laboratory recombinant strains that are not able to invade HeLa cells as furth...

Dra/AfaE Adhesin of Uropathogenic Dr/Afa + Escherichia coli Mediates Mortality in Pregnant Rats

“…In the present study, we have shown, using a gentamicin protection assay, that E. coli expressing AfaE-III but lacking AfaD can still invade HeLa cells. This is consistent with our previous experiments showing the invasiveness of Dr/Afa ϩ E. coli (9,11) and suggesting that mutation of the hydrophilic domain II of Dra/AfaE eliminates the capacity of E. coli to invade HeLa cells although it does not influence its attachment (1a). We speculate that since the afaE mutants were unable to invade HeLa cells, the expression of AfaE is an essential requirement for the internalization process.…”

Complicated Catheter-Associated Urinary Tract Infections Due toEscherichia coliandProteus mirabilis

“…Type 1 fimbria-mediated invasion is dependent upon FimH expression (241). E. coli strains that express Dr adhesins have been observed to invade epithelial cells including Caco-2 intestinal cells (115,286). Dr adhesin-mediated invasion of uroepithelial cells is dependent upon the presence of the decayaccelerating factor receptor on host cells (117) and may contribute to persistence within the upper urinary tract (271).…”

Pregnancy and chronic pyelonephritis: Clinical and immunological aspects (a review)

“…Известно, что при рецидивирующих инфек-циях МВП влагалище женщин чаще колонизировано уропатогенными микроорганизмами [7,26]. По данным P. Goluszko [27], в 52% посевов содержимого влагалища у женщин с рецидивирующей мочевой инфекцией выделя-ются грамотрицательные бактерии, тогда как у пациенток без данной патологии они определяются лишь в 24% на-блюдений. Кроме того, отмечается высокая колонизация влагалища Е. coli, E. faecalis, Klebsiella [4,7,25,26].…”

“…В инфицированной почке обнаруживали значи-тельное увеличе ние бактерий, регистрировали локальную продукцию ИЛ-6 и ИЛ-8, идентифицированную иммуно-химически, а также деструкцию почечной паренхимы, со-провождаемую выраженной инфильтрацией лейкоцита-ми. Данные результаты указывают на участие провоспа-лительных цитокинов в иммунопатогенезе ПН на самых ранних стадиях его развития [27,48].…”