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A Stapleton

Publications and source records attributed to A Stapleton.

At least 19 recordsLinked to original sources
PubMed2000

Expression of virulence factors among Escherichia coli isolated from the periurethra and urine of children with neurogenic bladder on intermittent catheterization.

BACKGROUND: Patients with neurogenic bladder caused by spinal cord injury or myelomeningocele empty their bladder several times a day by intermittent catheterization. Bacteriuria without symptoms of infection is frequently present in these patients. Occasionally a clone of Escherichia coli that has been carried for weeks without symptoms causes a symptomatic urinary tract infection. Virulence factors are commonly expressed among E. coli causing infection in patients with normal urinary tracts. However, it is unknown whether expression of virulence factors by an E. coli clone colonizing the neurogenic bladder increases the risk of subsequent infection. In this study we examined the prevalence of virulence factor expression among E. coli isolated from the periurethra and urine of patients with neurogenic bladder. METHODS: The prevalence of virulence factors was examined among E. coli isolated from the periurethra and urine in patients with neurogenic bladder who received intermittent catheterization and were followed for 6 months. Representative isolates from the 37 clonal types of E. coli detected in the periurethra and urine of children with neurogenic bladder were assessed for O antigen, hemolysin, aerobactin, serum resistance and type I and P-adhesin. RESULTS: All clones were serum-resistant and expressed type I adhesin, none expressed aerobactin and two expressed hemolysin. The presence of P-adhesin was not unique to clones associated with symptomatic infection. The presence of P-adhesin carried for weeks in a clone did not predict subsequent infection in the neurogenic bladder. CONCLUSION: Bacterial virulence factors did not predict infection of the neurogenic bladder.

Adolescent↗
PubMed1999

Host factors in susceptibility to urinary tract infections.

In summary, a variety of intrinsic and acquired factors influence the risk of RUTI in otherwise normal women, including history of prior UTIs, the woman's genetic background, and exposures to spermicides, sexual activity and antibiotics. Further studies are directed towards understanding the interplay between these factors and their relative importance among various subpopulations of women with RUTI, such as otherwise healthy pre- and post-menopausal women.

Animals↗
PubMed1998

Biochemical separations by continuous-bed chromatography.

Innovations in column-packing media for biomolecule purification have progressed from large spherical, porous polysaccharide beads to advanced polymeric supports. Continuous-bed technology is a radical new technology for chromatography based on the polymerization of advanced monomers and ionomers directly in the chromatographic column. The polymer chains form aggregates which coalesce into a dense, homogeneous network of interconnected nodules consisting of microparticles with an average diameter of 3000 A. The voids or channels between the nodules are large enough to permit a high hydrodynamic flow. Due to the high cross-linking of the polymer matrix, the surface of each nodule is nonporous yet the polymeric microparticles provide a very large surface area for high binding capacity. This paper will demonstrate the properties and advantages of using a continuous bed support for high resolution biomolecule separations at high flow-rates without sacrificing capacity.

Animals↗
PubMed1998

papG alleles of Escherichia coli strains causing first-episode or recurrent acute cystitis in adult women.

The distribution of the three alleles of the P adhesin gene papG (classes I-III) was assessed among 74 Escherichia coli urine isolates from women with first-episode or recurrent cystitis, and papG genotype was compared with clinical origin, O serogroup, agglutination of Gal(alpha1-4)Gal-coated latex beads and human or sheep erythrocytes, and hemolysin production. The class-III-only papG genotype (27% of strains) predominated over the I + III (3%) and II-only (7%) genotypes, irrespective of clinical category. In contrast to the class II papG allele, the class III allele was significantly concentrated in serogroups O6 and O18. Agglutination phenotypes corresponded significantly but incompletely with papG genotype, whereas hemolysin production and papG positivity were tightly correlated. These findings suggest that in acute cystitis in adult women, the class III papG allele predominates, confers distinctive agglutination phenotypes, and is restricted to specific E. coli lineages.

Adhesins, Escherichia coli↗
PubMed1998

Comparison of Escherichia coli strains recovered from human cystitis and pyelonephritis infections in transurethrally challenged mice.

Urinary tract infection, most frequently caused by Escherichia coli, is one of the most common bacterial infections in humans. A vast amount of literature regarding the mechanisms through which E. coli induces pyelonephritis has accumulated. Although cystitis accounts for 95% of visits to physicians for symptoms of urinary tract infections, few in vivo studies have investigated possible differences between E. coli recovered from patients with clinical symptoms of cystitis and that from patients with symptoms of pyelonephritis. Epidemiological studies indicate that cystitis-associated strains appear to differ from pyelonephritis-associated strains in elaboration of some putative virulence factors. With transurethrally challenged mice we studied possible differences using three each of the most virulent pyelonephritis and cystitis E. coli strains in our collection. The results indicate that cystitis strains colonize the bladder more rapidly than do pyelonephritis strains, while the rates of kidney colonization are similar. Cystitis strains colonize the bladder in higher numbers, induce more pronounced histologic changes in the bladder, and are more rapidly eliminated from the mouse urinary tract than pyelonephritis strains. These results provide evidence that cystitis strains differ from pyelonephritis strains in this model, that this model is useful for the study of the uropathogenicity of cystitis strains, and that it would be unwise to use pyelonephritis strains to study putative virulence factors important in the development of cystitis.

Animals↗
PubMed1997

Prevention of urinary tract infection.

Recurrent UTI remains an exceedingly common clinical problem among women of all ages. Among otherwise healthy premenopausal and postmenopausal women, increased susceptibility to recurrences seems to be conferred by intrinsic host factors, such as nonsecretor genotype or estrogen status, and by exogenous exposures or behaviors, such as use of a diaphragm with spermicide, antimicrobial use, and sexual behavior. The natural history of recurrent UTIs is notable for a temporal clustering phenomenon, the tendency of women to revert to a baseline infection pattern after the cessation of preventive interventions, and repeated serial reinfections of the urinary tract from the fecal reservoir, often by genetically identical organisms. Low-dose antimicrobial regimens given daily, three times weekly, or postcoitally are effective in preventing recurrences in most women with a predisposition to frequent infection. Intermittent patient-initiated self-treatment is an appropriate and effective option in some patients with lower recurrence rates. In postmenopausal women, estrogen replacement therapy, particularly vaginally applied estriol creams, may also significantly reduce the rate of recurrent UTI. Ongoing investigations in the areas of microbial ecology of the vaginal flora, the molecular basis for host-parasite interactions within the urinary tract, and vaccine development may eventually lead to improved means to prevent recurrent urinary tract infections more effectively.

Adult↗
PubMed1997

Antecedent antimicrobial use increases the risk of uncomplicated cystitis in young women.

To examine whether antecedent antimicrobial use influenced subsequent relative risk of urinary tract infection (UTI) in premenopausal women, data were analyzed from two cohorts of women observed prospectively for 6 months to determine risk factors for UTI. Using a Cox proportional hazards model to adjust for covariates, we found that 326 women in a University cohort and 425 women in a health-maintenance organization cohort were at increased risks for UTI (2.57 [95% confidence interval (CI), 1.24-5.32] and 5.83 [95% CI, 3.17-10.70], respectively) if antimicrobials had been taken during the previous 15-28 days but not during the previous 3, 7, or 14 days. The increased risks were noted both for women whose antimicrobial use was for treatment of a previous UTI and for women who received antimicrobials for other illnesses. These results suggest that recent antimicrobial use increases a woman's risk of UTI, perhaps by altering the indigenous urogenital flora and predisposing to vaginal colonization with uropathogens.

Adolescent↗
PubMed1997

Noninvasive evaluation of coronary artery disease and myocardial viability through stress echocardiography and myocardial perfusion imaging.

Today, primary care providers are managing clinical problems that were frequently addressed by a "specialist". Consequently, they must keep current with myriad state-of-the-art diagnostic modalities. In the case of coronary artery disease, knowledge about the reversibility of left ventricular dysfunction conceptualized as "hibernating" and "stunned" myocardium has resulted in an increased utilization of noninvasive cardiac imaging techniques to facilitate clinical decision making. These procedures provide diagnostic and prognostic information about coronary artery disease and left ventricular function beyond that provided by the conventional exercise stress test. The most commonly employed of these are the stress echocardiogram and stress myocardial nuclear perfusion procedures. Both modalities can be performed in conjunction with physical or pharmacologically induced stress, and may be performed on an outpatient basis. Knowledge of how these procedures are performed and the clinical data they provide will facilitate primary care providers as they care for this growing population.

Cardiotonic Agents↗
PubMed1995

Effect of secretor status on vaginal and rectal colonization with fimbriated Escherichia coli in women with and without recurrent urinary tract infection.

The prevalence and duration of rectal and vaginal colonization with P- and F-fimbriated Escherichia coli and the relationship of colonization with these strains to blood group secretor status was investigated. Rectal and vaginal E. coli isolates were prospectively collected twice monthly for 6 months from 20 young women with and 20 without a history of recurrent urinary tract infection (UTI). Rectal and vaginal colonization with P- and/or F-fimbriated E. coli was highly prevalent. Nonsecretors who developed UTI during the study period were significantly more likely to be colonized rectally with F-fimbriated E. coli than were the infected secretors (56% vs. 27%; P = .042) or uninfected nonsecretors (56% vs. 31%; P = .046). Persistent vaginal and rectal E. coli colonization with fimbriated organisms occurred commonly in the study patients but was not often temporally associated with the development of UTI. Results suggest that nonsecretors are more susceptible than secretors to colonization with F adhesin-bearing E. coli isolates.

Adhesins, Escherichia coli↗
PubMed1995

Chromosomal restriction fragment length polymorphism analysis of Escherichia coli strains causing recurrent urinary tract infections in young women.

To determine whether recurrent, symptomatic urinary tract infections (UTIs) in a given individual are due to the same or different strains, 71 Escherichia coli strains that caused recurrent UTIs were prospectively collected from 23 infection-prone young women and studied by chromosomal restriction fragment length polymorphism (RFLP) analysis using pulsed-field gel electrophoresis. Thirty-five strains from women with first-episode UTIs were also studied. Overall, 30 (68%) of 44 recurrent UTIs were caused by a strain previously identified in that person. In contrast, 32 of 35 strains from first-episode UTIs had unique RFLP profiles. Analysis of a subset of subjects established that the majority of recurrent UTIs were due to reinfection, not persistence of the pathogen within the urinary tract, and suggested that the colonic flora was the reservoir for these reinfecting strains.

Adolescent↗
PubMed1995

Comparison of expression of virulence factors by Escherichia coli causing cystitis and E. coli colonizing the periurethra of healthy girls.

The prevalence of virulence factors possessed by Escherichia coli colonizing the periurethra was examined and compared with that of E. coli causing urinary tract infection. One hundred two E. coli isolates obtained from the periurethra and urine of 7 non-sexually active girls at risk for cystitis were characterized for genetic relatedness and examined for expression of six virulence factors. Expression of virulence factors in colonizing clones of E. coli were compared with expression in clones from symptomatic infection. All virulence factors except P adhesin were commonly expressed by colonizing clones of E. coli that did not go on to infect the urinary tract. Although P adhesin-expressing E. coli were commonly isolated from episodes of cystitis, the presence of P adhesin on periurethral E. coli did not usually predict subsequent infection. By itself, expression of virulence factors on periurethral E. coli is not enough to predict subsequent infection.

Agglutination Tests↗
PubMed1994

Cloning and expression of soluble epoxide hydrolase from potato.

Five cDNAs encoding a putative soluble epoxide hydrolase (sEH) from potato were isolated and characterized. The cDNAs contained open reading frames encoding 36 kDa polypeptides which were highly homologous to the carboxy terminal region of mammalian sEH. When one of the cDNAs was expressed in a baculovirus system a soluble 38 kDa protein with epoxide hydrolase activity was produced. The recombinant enzyme hydrolyzed a commonly used diagnostic substrate for the soluble form of mammalian EH. Inhibitor profiles of the recombinant potato and mammalian sEH were also similar. The expression of sEH in potato was found to be regulated by both developmental and environmental signals. Levels of mRNA for sEH were higher in meristematic tissue than in mature leaves. This mRNA was also observed to accumulate on wounding and application of exogenous methyl jasmonate.

Amino Acid Sequence↗
PubMed1992

Partial amino acid sequence of potato solanidine UDP-glucose glucosyltransferase purified by new anion-exchange and size exclusion media.

Solanidine UDP-glucose glucosyltransferase (SGT) is involved in the biosynthesis of steroidal glycoalkaloids in potatoes. This enzyme is present at an extremely low level, is inherently unstable, and copurifies with the major storage protein patatin during isolation. We describe an improved method for isolating SGT from greening potato peel using two new chromatographic supports, Macro-Prep 50 Q anion-exchange and Superdex 75HR size exclusion media, under medium-pressure conditions at room temperature. The enzyme preparation was further resolved by SDS-PAGE and the proteins transferred to PVDF membrane (Immobilon-P). Two protein bands corresponding to active forms of SGT (36 and 37 kDa) were excised and cleaved with cyanogen bromide in trifluoroacetic acid. The resultant peptide mixtures were then separated by Tricine-SDS-PAGE and transferred to a PVDF membrane (Pro-Blott). The two major peptide bands observed in both digests (17 and 19 kDa) were sequenced. Identical N-terminal sequences were obtained from the 19-kDa peptides from both digests.

Amino Acid Sequence↗
PubMed1992

Binding of uropathogenic Escherichia coli R45 to glycolipids extracted from vaginal epithelial cells is dependent on histo-blood group secretor status.

Women with a history of recurrent Escherichia coli urinary tract infections (UTIs) are two to three times more likely to be nonsecretors of histo-blood group antigens than are women without such a history. Further, uroepithelial cells from women who are nonsecretors show enhanced adherence of uropathogenic E. coli compared with cells from secretors. To investigate the hypothesis that nonsecretors express unique receptors for uropathogenic E. coli related to their genetic background, we extracted glycosphingolipids (GSLs) from vaginal epithelial cells collected from nonsecretors and secretors and used an assay in which radiolabeled uropathogenic E. coli were bound to these GSLs separated on TLC plates. An E. coli strain (R45) expressing both P and F adhesins, which was isolated from one of these patients' UTIs, was metabolically labeled with 35S for the TLC binding assay. The radiolabeled E. coli R45 bound to two extended globo-series GSLs, sialosyl gal-globoside (SGG) and disialosyl gal-globoside (DSGG), found in the GSL extracts from nonsecretors but not from secretors. The identity of SGG in the nonsecretor GSL extracts was confirmed in radioimmunoassays using an mAb to SGG and in immunofluorescence assays with this mAb and native vaginal epithelial cells. We show that SGG and DSGG are selectively expressed by epithelial cells of nonsecretors, presumably as a result of sialylation of the gal-globoside precursor glycolipid, which in secretors is fucosylated and processed to ABH antigens. The presence of SGG and DSGG may account for the increased binding of E. coli to uroepithelial cells from nonsecretors and for their increased susceptibility to recurrent UTI.

Adult↗
PubMed1991

The Tn3 beta-lactamase gene acts as a hotspot for meiotic recombination in yeast.

Although genetic distances are often assumed to be proportional to physical distances, chromosomal regions with unusually high (hotspots) or low (coldspots) levels of meiotic recombination have been described in a number of genetic systems. In general, the DNA sequences responsible for these effects have not been determined. We report that the 5' region of the beta-lactamase (ampR) gene of the bacterial transposon Tn3 is a hotspot for meiotic recombination when inserted into the chromosomes of the yeast Saccharomyces cerevisiae. When these sequences are homozygous, both crossing over and gene conversion are locally stimulated. The 5' end of the beta-lactamase gene is about 100-fold "hotter" for crossovers than an average yeast DNA sequence.

Chi-Square Distribution↗
PubMed1991

Urovirulence determinants in Escherichia coli isolates causing first-episode and recurrent cystitis in women.

To assess the prevalence of urovirulence determinants among Escherichia coli isolates from women with acute uncomplicated cystitis, 121 isolates from 87 women with first-episode or recurrent cystitis and 156 fecal isolates from 52 women without recent urinary tract infection were tested using DNA probes for P fimbriae, hemolysin, aerobactin, and diffuse adhesin and for expression of hemolysin and P and F adhesins. P fimbrial genotype (P = .002), hemolysin phenotype (P = .007), and the diffuse adhesin determinant (P = .03), but not aerobactin, were found more frequently in E. coli from women with acute cystitis, and expression of the F adhesin (41%) was more common than the P adhesin (24%; P = .001). E. coli isolates that caused cystitis in women using diaphragms had fewer virulence determinants than those from nonusers (P = .04), suggesting that diaphragm use may allow infection with less virulent E. coli.

Acute Disease↗
PubMed1990

Postcoital antimicrobial prophylaxis for recurrent urinary tract infection. A randomized, double-blind, placebo-controlled trial.

We conducted a randomized, double-blind, placebo-controlled study to determine the efficacy of postcoital antibiotic prophylaxis in healthy young women prone to recurrent urinary tract infections. Sixteen patients were randomized to receive postcoital administration of a combination product of trimethoprim and sulfamethoxazole, while 11 received postcoital placebo. The treatment groups were similar with respect to age, parity, diaphragm use, history of lifetime urinary tract infections, frequency of intercourse, and number of lifetime sexual partners. In over 6 months of observation, postcoital administration of trimethoprim-sulfamethoxazole was highly effective in preventing recurrent urinary tract infections. Nine of 11 patients who took the placebo developed urinary tract infections (infection rate, 3.6 per patient-year), compared with only two of 16 patients who received postcoital trimethoprim-sulfamethoxazole (infection rate, 0.3 per patient-year). Postcoital administration of trimethoprim-sulfamethoxazole was effective in patients with both low (two or fewer times per week) and high (three or more times per week) intercourse frequencies. Side effects were few and compliance was excellent. We conclude that postcoital trimethoprim-sulfamethoxazole is a safe, effective, and inexpensive approach to management of recurrent urinary tract infections in young women.

Adult↗