Publications by authors named "Kristin M Tiemann"

11 Publications

  • Page 1 of 1

Renal scar formation and kidney function following antibiotic-treated murine pyelonephritis.

Dis Model Mech 2017 11 7;10(11):1371-1379. Epub 2017 Sep 7.

Department of Pediatrics, Washington University School of Medicine, St Louis, MO 63110, USA

We present a new preclinical model to study treatment, resolution and sequelae of severe ascending pyelonephritis. Urinary tract infection (UTI), primarily caused by uropathogenic (UPEC), is a common disease in children. Severe pyelonephritis is the primary cause of acquired renal scarring in childhood, which may eventually lead to hypertension and chronic kidney disease in a small but important fraction of patients. Preclinical modeling of UTI utilizes almost exclusively females, which (in most mouse strains) exhibit inherent resistance to severe ascending kidney infection; consequently, no existing preclinical model has assessed the consequences of recovery from pyelonephritis following antibiotic treatment. We recently published a novel mini-surgical bladder inoculation technique, with which male C3H/HeN mice develop robust ascending pyelonephritis, highly prevalent renal abscesses and evidence of fibrosis. Here, we devised and optimized an antibiotic treatment strategy within this male model to more closely reflect the clinical course of pyelonephritis. A 5-day ceftriaxone regimen initiated at the onset of abscess development achieved resolution of bladder and kidney infection. A minority of treated mice displayed persistent histological abscess at the end of treatment, despite microbiological cure of pyelonephritis; a matching fraction of mice 1 month later exhibited renal scars featuring fibrosis and ongoing inflammatory infiltrates. Successful antibiotic treatment preserved renal function in almost all infected mice, as assessed by biochemical markers 1 and 5 months post-treatment; hydronephrosis was observed as a late effect of treated pyelonephritis. An occasional mouse developed chronic kidney disease, generally reflecting the incidence of this late sequela in humans. In total, this model offers a platform to study the molecular pathogenesis of pyelonephritis, response to antibiotic therapy and emergence of sequelae, including fibrosis and renal scarring. Future studies in this system may inform adjunctive therapies that may reduce the long-term complications of this very common bacterial infection.
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http://dx.doi.org/10.1242/dmm.030130DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5719254PMC
November 2017

Synthesis, characterization, in vitro SAR and in vivo evaluation of N,N'bisnaphthylmethyl 2-alkyl substituted imidazolium salts against NSCLC.

Bioorg Med Chem Lett 2017 02 16;27(4):764-775. Epub 2017 Jan 16.

Department of Chemistry, University of Akron, Akron, OH 44325, United States. Electronic address:

Alkyl- and N,N'-bisnaphthyl-substituted imidazolium salts were tested in vitro for their anti-cancer activity against four non-small cell lung cancer cell lines (NCI-H460, NCI-H1975, HCC827, A549). All compounds had potent anticancer activity with 2 having IC values in the nanomolar range for three of the four cell lines, a 17-fold increase in activity against NCI-H1975 cells when compared to cisplatin. Compounds 1-4 also showed high anti-cancer activity against nine NSCLC cell lines in the NCI-60 human tumor cell line screen. In vitro studies performed using the Annexin V and JC-1 assays suggested that NCI-H460 cells treated with 2 undergo an apoptotic cell death pathway and that mitochondria could be the cellular target of 2 with the mechanism of action possibly related to a disruption of the mitochondrial membrane potential. The water solubilities of 1-4 was over 4.4mg/mL using 2-hydroxypropyl-β-cyclodextrin as a chemical excipient, thereby providing sufficient solubility for systemic administration.
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http://dx.doi.org/10.1016/j.bmcl.2017.01.035DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5575737PMC
February 2017

Polymeric nanoparticles in development for treatment of pulmonary infectious diseases.

Wiley Interdiscip Rev Nanomed Nanobiotechnol 2016 11 25;8(6):842-871. Epub 2016 Mar 25.

Department of Chemistry, Department of Chemical Engineering, Department of Materials Science & Engineering, Laboratory for Synthetic-Biologic Interactions, Texas A&M University, College Station, TX, USA.

Serious lung infections, such as pneumonia, tuberculosis, and chronic obstructive cystic fibrosis-related bacterial diseases, are increasingly difficult to treat and can be life-threatening. Over the last decades, an array of therapeutics and/or diagnostics have been exploited for management of pulmonary infections, but the advent of drug-resistant bacteria and the adverse conditions experienced upon reaching the lung environment urge the development of more effective delivery vehicles. Nanotechnology is revolutionizing the approach to circumventing these barriers, enabling better management of pulmonary infectious diseases. In particular, polymeric nanoparticle-based therapeutics have emerged as promising candidates, allowing for programmed design of multi-functional nanodevices and, subsequently, improved pharmacokinetics and therapeutic efficiency, as compared to conventional routes of delivery. Direct delivery to the lungs of such nanoparticles, loaded with appropriate antimicrobials and equipped with 'smart' features to overcome various mucosal and cellular barriers, is a promising approach to localize and concentrate therapeutics at the site of infection while minimizing systemic exposure to the therapeutic agents. The present review focuses on recent progress (2005-2015) important for the rational design of nanostructures, particularly polymeric nanoparticles, for the treatment of pulmonary infections with highlights on the influences of size, shape, composition, and surface characteristics of antimicrobial-bearing polymeric nanoparticles on their biodistribution, therapeutic efficacy, and toxicity. WIREs Nanomed Nanobiotechnol 2016, 8:842-871. doi: 10.1002/wnan.1401 For further resources related to this article, please visit the WIREs website.
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http://dx.doi.org/10.1002/wnan.1401DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5035710PMC
November 2016

Local Generation of Kynurenines Mediates Inhibition of Neutrophil Chemotaxis by Uropathogenic Escherichia coli.

Infect Immun 2016 Apr 24;84(4):1176-1183. Epub 2016 Mar 24.

Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri, USA

During epithelial infections, pathogenic bacteria employ an array of strategies to attenuate and evade host immune responses, including the influx of polymorphonuclear leukocytes (PMN; neutrophils). Among the most common bacterial infections in humans are those of the urinary tract, caused chiefly by uropathogenic Escherichia coli (UPEC). During the establishment of bacterial cystitis, UPEC suppresses innate responses via multiple independent strategies. We recently described UPEC attenuation of PMN trafficking to the urinary bladder through pathogen-specific local induction of indoleamine 2,3-dioxygenase (IDO), a tryptophan catabolic enzyme previously shown to have regulatory activity only in adaptive immunity. Here, we investigated the mechanism by which IDO induction attenuates PMN migration. Local tryptophan limitation, by which IDO is known to influence T cell longevity and proliferation, was not involved in its effect on PMN trafficking. Instead, metabolites in the IDO pathway, particularly L-kynurenine, directly suppressed PMN transepithelial migration and induced an attached, spread morphology in PMN both at rest and in the presence of chemotactic stimuli. Finally, kynurenines represent known ligands of the mammalian aryl hydrocarbon receptor (AHR), and UPEC infection of Ahr(-/-)mice recapitulated the derepressed PMN recruitment observed previously in Ido1(-/-)mice. UPEC therefore suppresses neutrophil migration early in bacterial cystitis by eliciting an IDO-mediated increase in local production of kynurenines, which act through the AHR to impair neutrophil chemotaxis.
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http://dx.doi.org/10.1128/IAI.01202-15DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4807489PMC
April 2016

Klebsiella pneumoniae FimK Promotes Virulence in Murine Pneumonia.

J Infect Dis 2016 Feb 7;213(4):649-58. Epub 2015 Sep 7.

Division of Pediatric Infectious Diseases, Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri.

Klebsiella pneumoniae, a chief cause of nosocomial pneumonia, is a versatile and commonly multidrug-resistant human pathogen for which further insight into pathogenesis is needed. We show that the pilus regulatory gene fimK promotes the virulence of K. pneumoniae strain TOP52 in murine pneumonia. This contrasts with the attenuating effect of fimK on urinary tract virulence, illustrating that a single factor may exert opposing effects on pathogenesis in distinct host niches. Loss of fimK in TOP52 pneumonia was associated with diminished lung bacterial burden, limited innate responses within the lung, and improved host survival. FimK expression was shown to promote serum resistance, capsule production, and protection from phagocytosis by host immune cells. Finally, while the widely used K. pneumoniae model strain 43816 produces rapid dissemination and death in mice, TOP52 caused largely localized pneumonia with limited lethality, thereby providing an alternative tool for studying K. pneumoniae pathogenesis and control within the lung.
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http://dx.doi.org/10.1093/infdis/jiv440DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4721909PMC
February 2016

Imidazolium salts as small-molecule urinary bladder exfoliants in a murine model.

Antimicrob Agents Chemother 2015 Sep 29;59(9):5494-502. Epub 2015 Jun 29.

Department of Pediatrics, Washington University, St. Louis, Missouri, USA Department of Molecular Microbiology, Washington University, St. Louis, Missouri, USA

We present a novel family of small-molecule urinary bladder exfoliants that are expected to be of great value in preclinical studies of urologic conditions and have improved potential for translation compared with prior agents. There is broad urologic interest in the therapeutic potential of such exfoliating agents. The primary agent used in preclinical models, the cationic peptide protamine sulfate (PS), has limited translational potential due to concerns including systemic adverse reactions and bladder tissue injury. Intravesical application of a safe, systemically nontoxic exfoliant would have potential utility in the eradication of Escherichia coli and other uropathogens that reside in the bladder epithelium following cystitis, as well as in chronic bladder pain and bladder cancer. Here, we introduce a family of imidazolium salts with potent and focused exfoliating activity on the bladder epithelium. Synthesis and purification were straightforward and scalable, and the compounds exhibited prolonged stability in lyophilized form. Most members of the compound family were cytotoxic to cultured uroepithelial cells, with >10-fold differences in potency across the series. Upon topical (intravesical) administration of selected compounds to the murine bladder, complete epithelial exfoliation was achieved with physiologically relevant imidazolium concentrations and brief contact times. The exfoliative activity of these compounds was markedly improved in comparison to PS, as assessed by microscopy, immunofluorescence, and immunoblotting for uroplakins. Bladder uroepithelium regenerated within days to yield a histologically normal appearance, and no toxicity was observed. Finally, the chemical scaffold offers an opportunity for inclusion of antimicrobials or conjugation with chemotherapeutic or other moieties.
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http://dx.doi.org/10.1128/AAC.00881-15DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4538537PMC
September 2015

Preparation and in vitro antimicrobial activity of silver-bearing degradable polymeric nanoparticles of polyphosphoester-block-poly(L-lactide).

ACS Nano 2015 Feb 26;9(2):1995-2008. Epub 2015 Jan 26.

Departments of Chemistry, Chemical Engineering, and Materials Science and Engineering, and Laboratory for Synthetic-Biologic Interactions, Texas A&M University , P.O. Box 30012, 3255 TAMU, College Station, Texas 77842, United States.

The development of well-defined polymeric nanoparticles (NPs) as delivery carriers for antimicrobials targeting human infectious diseases requires rational design of the polymer template, an efficient synthetic approach, and fundamental understanding of the developed NPs, e.g., drug loading/release, particle stability, and other characteristics. Herein, we developed and evaluated the in vitro antimicrobial activity of silver-bearing, fully biodegradable and functional polymeric NPs. A series of degradable polymeric nanoparticles (dNPs), composed of phosphoester and L-lactide and designed specifically for silver loading into the hydrophilic shell and/or the hydrophobic core, were prepared as potential delivery carriers for three different types of silver-based antimicrobials-silver acetate or one of two silver carbene complexes (SCCs). Silver-loading capacities of the dNPs were not influenced by the hydrophilic block chain length, loading site (i.e., core or shell), or type of silver compound, but optimization of the silver feed ratio was crucial to maximize the silver loading capacity of dNPs, up to ca. 12% (w/w). The release kinetics of silver-bearing dNPs revealed 50% release at ca. 2.5-5.5 h depending on the type of silver compound. In addition, we undertook a comprehensive evaluation of the rates of hydrolytic or enzymatic degradability and performed structural characterization of the degradation products. Interestingly, packaging of the SCCs in the dNP-based delivery system improved minimum inhibitory concentrations up to 70%, compared with the SCCs alone, as measured in vitro against 10 contemporary epidemic strains of Staphylococcus aureus and eight uropathogenic strains of Escherichia coli. We conclude that these dNP-based delivery systems may be beneficial for direct epithelial treatment and/or prevention of ubiquitous bacterial infections, including those of the skin and urinary tract.
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http://dx.doi.org/10.1021/nn507046hDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4455953PMC
February 2015

Bacterial lysis liberates the neutrophil migration suppressor YbcL from the periplasm of uropathogenic Escherichia coli.

Infect Immun 2014 Dec 2;82(12):4921-30. Epub 2014 Sep 2.

Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri, USA Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA

Uropathogenic Escherichia coli (UPEC) modulates aspects of the innate immune response during urinary tract infection to facilitate bacterial invasion of the bladder epithelium, a requirement for the propagation of infection. For example, UPEC-encoded YbcL suppresses the traversal of bladder epithelia by neutrophils in both an in vitro model and an in vivo murine cystitis model. The suppressive activity of YbcL requires liberation from the bacterial periplasm, though the mechanism of release is undefined. Here we present findings on the site of action of YbcL and demonstrate a novel mode of secretion for a UPEC exoprotein. Suppression of neutrophil migration by purified YbcL(UTI), encoded by cystitis isolate UTI89, required the presence of a uroepithelial layer; YbcL(UTI) did not inhibit neutrophil chemotaxis directly. YbcL(UTI) was released to a greater extent during UPEC infection of uroepithelial cells than during that of neutrophils. Release of YbcL(UTI) was maximal when UPEC and bladder epithelial cells were in close proximity. Established modes of secretion, including outer membrane vesicles, the type II secretion system, and the type IV pilus, were dispensable for YbcL(UTI) release from UPEC. Instead, YbcL(UTI) was liberated during bacterial death, which was augmented upon exposure to bladder epithelial cells, as confirmed by detection of bacterial cytoplasmic proteins and DNA in the supernatant and enumeration of bacteria with compromised membranes. As YbcL(UTI) acts on the uroepithelium to attenuate neutrophil migration, this mode of release may represent a type of altruistic cooperation within a UPEC population during colonization of the urinary tract.
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http://dx.doi.org/10.1128/IAI.01838-14DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4249291PMC
December 2014

A serologic correlate of protective immunity against community-onset Staphylococcus aureus infection.

Clin Infect Dis 2013 Jun 27;56(11):1554-61. Epub 2013 Feb 27.

Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri, USA.

Background: Staphylococcus aureus is among the leading causes of human infection. Widespread drug resistance, emergence of highly virulent strains, and the ability of S. aureus to colonize >30% of the human population contribute to this organism's pathogenic success. Human serologic responses to S. aureus and their relationship to protective immunity remain incompletely defined, challenging the strategic development of efficacious vaccines.

Methods: We measured humoral responses to 2 staphylococcal exotoxins, α-hemolysin (Hla) and Panton-Valentine leukocidin (PVL; LukF-PV/LukS-PV subunits), both premier targets of current vaccine and immunotherapy development. We correlated acute and convalescent serum antibody levels with incidence of recurrent infection over 12 months follow-up in 235 children with S. aureus colonization, primary or recurrent skin and soft tissue infection, or invasive disease.

Results: Cutaneous infection elicited transient increases in anti-Hla and anti-PVL antibodies; however, subsequent infection risk was similar between primary and recurrent cutaneous infection cohorts. Patients with invasive infections had the lowest preexisting titers against Hla and LukF but displayed the highest convalescent titers. Across cohorts, convalescent anti-Hla titers correlated with protection against subsequent S. aureus infection.

Conclusions: Cutaneous S. aureus infection does not reliably provoke durable, protective immune responses. This study provides the first link between protection from disease recurrence and the humoral response to Hla, a virulence factor already implicated in disease pathogenesis. These observations can be utilized to refine ongoing vaccine and immunotherapy efforts and inform the design of clinical trials.
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http://dx.doi.org/10.1093/cid/cit123DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3641868PMC
June 2013

Synthetic polymer nanoparticles conjugated with FimH(A) from E. coli pili to emulate the bacterial mode of epithelial internalization.

J Am Chem Soc 2012 Mar 23;134(9):3938-41. Epub 2012 Feb 23.

Department of Chemistry and Chemical Engineering, Texas A&M University, P.O. Box 30012, College Station, Texas 77842, USA.

Amphiphilic block copolymer nanoparticles are conjugated with uropathogenic Escherichia coli type 1 pilus adhesin FimH(A) through amidation chemistry to enable bladder epithelial cell binding and internalization of the nanoparticles in vitro.
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http://dx.doi.org/10.1021/ja2091917DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3325780PMC
March 2012