1
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Doranga S, Conway T. OmpC-Dependent Bile Tolerance Contributes to E. coli Colonization of the Mammalian Intestine. Microbiol Spectr 2023; 11:e0524122. [PMID: 37014216 PMCID: PMC10269588 DOI: 10.1128/spectrum.05241-22] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2022] [Accepted: 03/09/2023] [Indexed: 04/05/2023] Open
Abstract
Escherichia coli persistently colonizes the mammalian intestine by mechanisms that are not fully understood. Previously, we found when streptomycin-treated mice were fed E. coli MG1655, the intestine selected for envZ missense mutants that outcompeted the wild type. The better-colonizing envZ mutants had a higher level of OmpC and reduced OmpF. This suggested the EnvZ/OmpR two-component system and outer membrane proteins play a role in colonization. In this study, we show that wild-type E. coli MG1655 outcompetes an envZ-ompR knockout mutant. Moreover, ompA and ompC knockout mutants are outcompeted by the wild type, while an ompF knockout mutant colonizes better than the wild type. Outer membrane protein gels show the ompF mutant overproduces OmpC. An ompC mutant is more sensitive to bile salts than the wild type and ompF mutant. The ompC mutant initiates colonization slowly because it is sensitive to physiological concentrations of bile salts in the intestine. Overexpression of ompC under the control of a constitutive promoter confers a colonization advantage only when ompF is deleted. These results indicate that fine-tuning of OmpC and OmpF levels is needed to maximize competitive fitness in the intestine. RNA sequencing reveals the EnvZ/OmpR two-component system is active in the intestine: ompC is upregulated and ompF is downregulated. While other factors could also contribute to the advantage provided by OmpC, we provide evidence that OmpC is important for E. coli to colonize the intestine because its smaller pore size excludes bile salts or other unknown toxic substances, while OmpF is deleterious because its larger pore size allows bile salts or other unknown toxic substances to enter the periplasm. IMPORTANCE Every mammalian intestine is colonized with Escherichia coli. Although E. coli is one of the most studied model organisms, how it colonizes the intestine is not fully understood. Here, we investigated the role of the EnvZ/OmpR two-component system and outer membrane proteins in colonization of the mouse intestine by E. coli. We report that an ompC mutant is a poor colonizer, while an ompF mutant, which overproduces OmpC, outcompetes the wild type. OmpF has a larger pore size that allows toxic bile salts or other toxic compounds into the cell and is deleterious for colonization of the intestine. OmpC has a smaller pore size and excludes bile salts. Our findings provide insights into why E. coli fine-tunes the levels of OmpC and OmpF during colonization via the EnvZ/OmpR two-component system.
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Affiliation(s)
- Sudhir Doranga
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, Oklahoma, USA
| | - Tyrrell Conway
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, Oklahoma, USA
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2
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Huang L, Zhang Y, Du X, An R, Liang X. Escherichia coli Can Eat DNA as an Excellent Nitrogen Source to Grow Quickly. Front Microbiol 2022; 13:894849. [PMID: 35836416 PMCID: PMC9273947 DOI: 10.3389/fmicb.2022.894849] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2022] [Accepted: 05/31/2022] [Indexed: 11/13/2022] Open
Abstract
Is DNA or RNA a good nutrient? Although scientists have raised this question for dozens of years, few textbooks mention the nutritional role of nucleic acids. Paradoxically, mononucleotides are widely added to infant formula milk and animal feed. Interestingly, competent bacteria can bind and ingest extracellular DNA and even integrate it into their genome. These results prompt us to clarify whether bacteria can “eat” DNA as food. We found that Escherichia coli can grow well in the medium with DNA as carbon and nitrogen sources. More interestingly, in the presence of glucose and DNA, bacteria grew more rapidly, showing that bacteria can use DNA as an excellent nitrogen source. Surprisingly, the amount of DNA in the culture media decreased but its length remained unchanged, demonstrating that E. coli ingested long DNA directly. The gene expression study shows that E. coli mainly ingests DNA before digestion and digests it in the periplasm. Bifidobacterium bifidum can also use DNA as the nitrogen source for growth, but not efficiently as E. coli. This study is of great significance to study DNA metabolism and utilization in organisms. It also lays a foundation to understand the nutritional function of DNA in intestinal flora and human health.
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Affiliation(s)
- Lili Huang
- College of Food Science and Engineering, Ocean University of China, Qingdao, China
| | - Yehui Zhang
- College of Food Science and Engineering, Ocean University of China, Qingdao, China
| | - Xinmei Du
- College of Food Science and Engineering, Ocean University of China, Qingdao, China
| | - Ran An
- College of Food Science and Engineering, Ocean University of China, Qingdao, China
- *Correspondence: Ran An
| | - Xingguo Liang
- College of Food Science and Engineering, Ocean University of China, Qingdao, China
- Laboratory for Marine Drugs and Bioproducts, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China
- Xingguo Liang
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3
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García MA, Varum F, Al-Gousous J, Hofmann M, Page S, Langguth P. In Vitro Methodologies for Evaluating Colon-Targeted Pharmaceutical Products and Industry Perspectives for Their Applications. Pharmaceutics 2022; 14:pharmaceutics14020291. [PMID: 35214024 PMCID: PMC8876830 DOI: 10.3390/pharmaceutics14020291] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Revised: 01/22/2022] [Accepted: 01/24/2022] [Indexed: 02/04/2023] Open
Abstract
Several locally acting colon-targeted products to treat colonic diseases have been recently developed and marketed, taking advantage of gastrointestinal physiology to target delivery. Main mechanisms involve pH-dependent, time-controlled and/or enzymatic-triggered release. With site of action located before systemic circulation and troublesome colonic sampling, there is room for the introduction of meaningful in vitro methods for development, quality control (QC) and regulatory applications of these formulations. A one-size-fits-all method seems unrealistic, as the selection of experimental conditions should resemble the physiological features exploited to trigger the release. This article reviews the state of the art for bio-predictive dissolution testing of colon-targeted products. Compendial methods overlook physiological aspects, such as buffer molarity and fluid composition. These are critical for pH-dependent products and time-controlled systems containing ionizable drugs. Moreover, meaningful methods for enzymatic-triggered products including either bacteria or enzymes are completely ignored by pharmacopeias. Bio-predictive testing may accelerate the development of successful products, although this may require complex methodologies. However, for high-throughput routine testing (e.g., QC), simplified methods can be used where balance is struck between simplicity, robustness and transferability on one side and bio-predictivity on the other. Ultimately, bio-predictive methods can occupy a special niche in terms of supplementing plasma concentration data for regulatory approval.
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Affiliation(s)
- Mauricio A. García
- Department of Biopharmaceutics and Pharmaceutical Technology, Johannes Gutenberg University Mainz, 55099 Mainz, Germany; (M.A.G.); (J.A.-G.)
| | - Felipe Varum
- Pharmaceutical Research and Development, F. Hoffmann-La Roche Ltd., 4070 Basel, Switzerland; (F.V.); (M.H.); (S.P.)
| | - Jozef Al-Gousous
- Department of Biopharmaceutics and Pharmaceutical Technology, Johannes Gutenberg University Mainz, 55099 Mainz, Germany; (M.A.G.); (J.A.-G.)
- Department of Pharmaceutical Sciences, University of Michigan, 428 Church Street, Ann Arbor, MI 48109, USA
| | - Michael Hofmann
- Pharmaceutical Research and Development, F. Hoffmann-La Roche Ltd., 4070 Basel, Switzerland; (F.V.); (M.H.); (S.P.)
| | - Susanne Page
- Pharmaceutical Research and Development, F. Hoffmann-La Roche Ltd., 4070 Basel, Switzerland; (F.V.); (M.H.); (S.P.)
| | - Peter Langguth
- Department of Biopharmaceutics and Pharmaceutical Technology, Johannes Gutenberg University Mainz, 55099 Mainz, Germany; (M.A.G.); (J.A.-G.)
- Correspondence:
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4
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Krollik K, Lehmann A, Wagner C, Kaidas J, Kubas H, Weitschies W. The effect of buffer species on biorelevant dissolution and precipitation assays - Comparison of phosphate and bicarbonate buffer. Eur J Pharm Biopharm 2021; 171:90-101. [PMID: 34592364 DOI: 10.1016/j.ejpb.2021.09.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Revised: 09/07/2021] [Accepted: 09/22/2021] [Indexed: 12/31/2022]
Abstract
Biorelevant solubility and dissolution testing is an important tool during pharmaceutical development, however, solubility experiments performed using biorelevant media often do not properly match the solubility data observed in human intestinal fluids. Even though the bicarbonate buffer is the predominant buffer system in the small intestine, in vitro assays are commonly performed using non-volatile buffer systems like phosphate and maleate. In the current study, bicarbonate- and phosphate-buffered biorelevant media were applied to solubility, dissolution, and precipitation testing for a broad range of model compounds. It was found that the medium affects primarily the dissolution kinetics. However, with the knowledge of the unique buffering properties of bicarbonate buffer in the diffusion layer, it was not always possible to predict the effect of buffer species on solubility and dissolution when changing from phosphate to bicarbonate buffer. This once again highlights the special role of bicarbonate buffer for simulating the conditions in the human intestinal fluids. Moreover, it is necessary to further investigate the factors which may cause the differences in solubility and dissolution behavior when using phosphate- vs. bicarbonate-buffered biorelevant media.
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Affiliation(s)
- Katharina Krollik
- Institute of Pharmacy, Department of Biopharmaceutics and Pharmaceutical Technology, University of Greifswald, Felix-Hausdorff-Straße 3, Greifswald, Germany; Chemical and Pharmaceutical Development, Merck KGaA, Frankfurter Straße 250, Darmstadt, Germany.
| | - Andreas Lehmann
- Chemical and Pharmaceutical Development, Merck KGaA, Frankfurter Straße 250, Darmstadt, Germany.
| | - Christian Wagner
- Chemical and Pharmaceutical Development, Merck KGaA, Frankfurter Straße 250, Darmstadt, Germany.
| | - Jonathan Kaidas
- Chemical and Pharmaceutical Development, Merck KGaA, Frankfurter Straße 250, Darmstadt, Germany.
| | - Holger Kubas
- Chemical and Pharmaceutical Development, Merck KGaA, Frankfurter Straße 250, Darmstadt, Germany.
| | - Werner Weitschies
- Institute of Pharmacy, Department of Biopharmaceutics and Pharmaceutical Technology, University of Greifswald, Felix-Hausdorff-Straße 3, Greifswald, Germany.
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5
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Midgett CR, Talbot KM, Day JL, Munson GP, Kull FJ. Structure of the master regulator Rns reveals an inhibitor of enterotoxigenic Escherichia coli virulence regulons. Sci Rep 2021; 11:15663. [PMID: 34341412 PMCID: PMC8329261 DOI: 10.1038/s41598-021-95123-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Accepted: 07/14/2021] [Indexed: 02/07/2023] Open
Abstract
Enteric infections caused by the gram-negative bacteria enterotoxigenic Escherichia coli (ETEC), Vibrio cholerae, Shigella flexneri, and Salmonella enterica are among the most common and affect billions of people each year. These bacteria control expression of virulence factors using a network of transcriptional regulators, some of which are modulated by small molecules as has been shown for ToxT, an AraC family member from V. cholerae. In ETEC the expression of many types of adhesive pili is dependent upon the AraC family member Rns. We present here the 3 Å crystal structure of Rns and show it closely resembles ToxT. Rns crystallized as a dimer via an interface similar to that observed in other dimeric AraC's. Furthermore, the structure of Rns revealed the presence of a ligand, decanoic acid, that inhibits its activity in a manner similar to the fatty acid mediated inhibition observed for ToxT and the S. enterica homologue HilD. Together, these results support our hypothesis that fatty acids regulate virulence controlling AraC family members in a common manner across a number of enteric pathogens. Furthermore, for the first time this work identifies a small molecule capable of inhibiting the ETEC Rns regulon, providing a basis for development of therapeutics against this deadly human pathogen.
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Affiliation(s)
| | - Kacey Marie Talbot
- Department of Microbiology and Immunology, Miller School of Medicine, University of Miami, Miami, FL, USA
| | - Jessica L Day
- Department of Chemistry, Dartmouth College, Hanover, NH, USA
- Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, NH, USA
| | - George P Munson
- Department of Microbiology and Immunology, Miller School of Medicine, University of Miami, Miami, FL, USA
| | - F Jon Kull
- Department of Chemistry, Dartmouth College, Hanover, NH, USA.
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6
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Salehi N, Al-Gousous J, Mudie DM, Amidon GL, Ziff RM, Amidon GE. Hierarchical Mass Transfer Analysis of Drug Particle Dissolution, Highlighting the Hydrodynamics, pH, Particle Size, and Buffer Effects for the Dissolution of Ionizable and Nonionizable Drugs in a Compendial Dissolution Vessel. Mol Pharm 2020; 17:3870-3884. [PMID: 32886520 DOI: 10.1021/acs.molpharmaceut.0c00614] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Dissolution is a crucial process for the oral delivery of drug products. Before being absorbed through epithelial cell membranes to reach the systemic circulation, drugs must first dissolve in the human gastrointestinal (GI) tract. In vivo and in vitro dissolutions are complex because of their dependency upon the drug physicochemical properties, drug product, and GI physiological properties. However, an understanding of this process is critical for the development of robust drug products. To enhance our understanding of in vivo and in vitro dissolutions, a hierarchical mass transfer (HMT) model was developed that considers the drug properties, GI fluid properties, and fluid hydrodynamics. The key drug properties include intrinsic solubility, acid/base character, pKa, particle size, and particle polydispersity. The GI fluid properties include bulk pH, buffer species concentration, fluid shear rate, and fluid convection. To corroborate the model, in vitro dissolution experiments were conducted in the United States Pharmacopeia (USP) 2 dissolution apparatus. A weakly acidic (ibuprofen), a weakly basic (haloperidol), and a nonionizable (felodipine) drug were used to study the effects of the acid/base character, pKa, and intrinsic solubility on dissolution. 900 mL of 5 mM bicarbonate and phosphate buffers at pH 6.5 and 37 °C was used to study the impact of the buffer species on drug dissolution. To investigate the impacts of fluid shear rate and convection, the apparatus was operated at different impeller rotational speeds. Moreover, presieved ibuprofen particles with different average diameters were used to investigate the effect of particle size on drug dissolution. In vitro experiments demonstrate that the dissolution rates of both the ionizable compounds used in this study were slower in bicarbonate buffer than in phosphate buffer, with the same buffer concentration, because of the lower interfacial buffer capacity, a unique behavior of bicarbonate buffer. Therefore, using surrogates (i.e., 50 mM phosphate) for bicarbonate buffer for biorelevant in vitro dissolution testing may overestimate the in vivo dissolution rate for ionizable drugs. Model simulations demonstrated that, assuming a monodisperse particle size when modeling, dissolution may overestimate the dissolution rate for polydisperse particle size distributions. The hydrodynamic parameters (maximum shear rate and fluid velocity) under in vitro conditions in the USP 2 apparatus under different rotational speeds are orders of magnitude higher compared to the in vivo situation. The inconsistencies between the in vivo and in vitro drug dissolution hydrodynamic conditions may cause an overestimation of the dissolution rate under in vitro conditions. The in vitro dissolution data supported the accuracy of the HMT for drug dissolution. This is the first drug dissolution model that incorporates the effect of the bulk pH and buffer concentration on the interfacial drug particle solubility of ionizable compounds, combined with the medium hydrodynamics effect (diffusion, convection, shear, and confinement components), and drug particle size distribution.
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Affiliation(s)
- Niloufar Salehi
- Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan 48109, United States.,Department of Pharmaceutical Sciences, University of Michigan, Ann Arbor, Michigan,48109, United States
| | - Jozef Al-Gousous
- Institute of Pharmaceutical and Biomedical Sciences, Johannes Gutenberg University Mainz, Staudingerweg 5, Mainz 55128, Germany
| | - Deanna M Mudie
- Global Research and Development, Lonza, Bend, Oregon 97703, United States
| | - Gordon L Amidon
- Department of Pharmaceutical Sciences, University of Michigan, Ann Arbor, Michigan,48109, United States
| | - Robert M Ziff
- Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Gregory E Amidon
- Department of Pharmaceutical Sciences, University of Michigan, Ann Arbor, Michigan,48109, United States
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7
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Fink C, Lecomte M, Badolo L, Wagner K, Mäder K, Peters SA. Identification of solubility-limited absorption of oral anticancer drugs using PBPK modeling based on rat PK and its relevance to human. Eur J Pharm Sci 2020; 152:105431. [PMID: 32562690 DOI: 10.1016/j.ejps.2020.105431] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2020] [Revised: 05/19/2020] [Accepted: 06/16/2020] [Indexed: 10/24/2022]
Abstract
Solubility is one of the key parameters that is optimized during drug discovery to ensure sufficient drug concentration in systemic circulation and to achieve the desired pharmacological response. We recently reported the application of PBPK analysis of early clinical pharmacokinetic data to identify drugs whose absorption are truly limited by solubility. In this work, we selected ten anticancer drugs that exhibit poor in vitro solubility to explore the utility of this approach to identify solubility-limited absorption based on rat pharmacokinetic data and compare the findings to human data. Oral rat pharmacokinetic studies were performed at the body weight-scaled doses of the model drugs' human food effect studies, and analyzed using a top-down PBPK modeling approach. A good correlation of solubility-limited absorption in rat and human was observed. These results allow an early identification of drugs with truly solubility-limited absorption, with the potential to guide decisions and save valuable resources in drug development.
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Affiliation(s)
- Christina Fink
- Chemical Pharmaceutical Development, Merck KGaA, Darmstadt, Germany; Institute of Pharmacy, Faculty of Biosciences, Martin-Luther University Halle-Wittenberg, Germany
| | - Marc Lecomte
- NCE DMPK, Discovery Technology, Merck KGaA, Darmstadt, Germany
| | - Lassina Badolo
- NCE DMPK, Discovery Technology, Merck KGaA, Darmstadt, Germany
| | - Knut Wagner
- Chemical Pharmaceutical Development, Merck KGaA, Darmstadt, Germany
| | - Karsten Mäder
- Institute of Pharmacy, Faculty of Biosciences, Martin-Luther University Halle-Wittenberg, Germany
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8
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Amaral Silva D, Davies NM, Doschak MR, Al-Gousous J, Bou-Chacra N, Löbenberg R. Mechanistic understanding of underperforming enteric coated products: Opportunities to add clinical relevance to the dissolution test. J Control Release 2020; 325:323-334. [DOI: 10.1016/j.jconrel.2020.06.031] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Accepted: 06/26/2020] [Indexed: 02/04/2023]
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9
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Hofmann M, García MA, Al-Gousous J, Ruiz-Picazo A, Thieringer F, Nguyen MA, Månsson W, Galle PR, Langguth P. In vitro prediction of in vivo absorption of ibuprofen from suspensions through rational choice of dissolution conditions. Eur J Pharm Biopharm 2020; 149:229-237. [DOI: 10.1016/j.ejpb.2020.02.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2019] [Revised: 02/07/2020] [Accepted: 02/21/2020] [Indexed: 01/19/2023]
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10
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Al-Gousous J, Salehi N, Amidon GE, Ziff RM, Langguth P, Amidon GL. Mass Transport Analysis of Bicarbonate Buffer: Effect of the CO 2-H 2CO 3 Hydration-Dehydration Kinetics in the Fluid Boundary Layer and the Apparent Effective p K a Controlling Dissolution of Acids and Bases. Mol Pharm 2019; 16:2626-2635. [PMID: 31013101 DOI: 10.1021/acs.molpharmaceut.9b00187] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The main buffering system influencing ionizable drug dissolution in the human intestinal fluid is bicarbonate-based; however, it is rarely used in routine pharmaceutical practice due to the volatility of dissolved CO2. The typical pharmaceutical buffers used fail to capture the unique aspects of the hydration-dehydration kinetics of the bicarbonate-CO2 system. In particular, CO2 is involved in a reversible interconversion with carbonic acid (H2CO3), which is the actual conjugate acid of the system, as follows CO2 + H2O ⇌ H2CO3. In contrast to ionization reactions, this interconversion does not equilibrate very rapidly compared to the diffusional processes through a typical fluid diffusion boundary layer at a solid-liquid interface. In this report, a mathematical mass transport analysis was developed for ionizable drug dissolution in bicarbonate using the rules of conservation of mass and electric charge in addition to accounting for the diffusional times and reaction rate constants of the CO2-H2CO3 interconversion. This model, which includes both the hydration reaction rate and dehydration reaction rate, we called the "reversible non-equilibrium" (RNE) model. The predictions made by this RNE approach for ionizable drug dissolution rates were compared to the experimental data generated by an intrinsic dissolution method for three ionizable drugs, indomethacin, ibuprofen, and haloperidol. The results demonstrate the superiority of predictions for the RNE approach compared to the predictions of a model assuming equilibrium between CO2 and H2CO3, as well as models ignoring reactions. The analysis also shows that bicarbonate buffer can be viewed as having an effective p Ka in the boundary layer that is different from that in bulk and is hydrodynamics-dependent.
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Affiliation(s)
- Jozef Al-Gousous
- Department of Pharmaceutical Sciences , University of Michigan , 428 Church Street , Ann Arbor , Michigan 48109 , United States
| | - Niloufar Salehi
- Department of Chemical Engineering , University of Michigan , 2300 Hayward Street , Ann Arbor , Michigan 48109 , United States
| | - Gregory E Amidon
- Department of Pharmaceutical Sciences , University of Michigan , 428 Church Street , Ann Arbor , Michigan 48109 , United States
| | - Robert M Ziff
- Department of Chemical Engineering , University of Michigan , 2300 Hayward Street , Ann Arbor , Michigan 48109 , United States
| | - Peter Langguth
- Institute of Pharmacy and Biochemistry , Johannes Gutenberg University Mainz , Staudingerweg 5 , 55128 Mainz , Germany
| | - Gordon L Amidon
- Department of Pharmaceutical Sciences , University of Michigan , 428 Church Street , Ann Arbor , Michigan 48109 , United States
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11
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Levine MM, Barry EM, Chen WH. A roadmap for enterotoxigenic Escherichia coli vaccine development based on volunteer challenge studies. Hum Vaccin Immunother 2019; 15:1357-1378. [PMID: 30724648 PMCID: PMC6663128 DOI: 10.1080/21645515.2019.1578922] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Enterotoxigenic Escherichia coli (ETEC) is a major cause of travelers’ diarrhea and of diarrhea among young children in developing countries. Experimental challenge studies in adult volunteers have played a pivotal role in establishing ETEC as an enteric pathogen, elucidating its pathogenesis by identifying specific virulence attributes, characterizing the human immune response to clinical and sub-clinical ETEC infection and assessing preliminarily the clinical acceptability, immunogenicity and efficacy of prototype ETEC vaccines. This review provides a historical perspective of experimental challenge studies with ETEC. It summarizes pioneering early studies carried out by investigators at the University of Maryland School of Medicine to show how those studies provided key information that influenced the directions taken by many research groups to develop vaccines to prevent ETEC. In addition, key experimental challenge studies undertaken at other institutions will also be cited.
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Affiliation(s)
- Myron M Levine
- a Center for Vaccine Development and Global Health , University of Maryland School of Medicine , Baltimore , MD , USA
| | - Eileen M Barry
- a Center for Vaccine Development and Global Health , University of Maryland School of Medicine , Baltimore , MD , USA
| | - Wilbur H Chen
- a Center for Vaccine Development and Global Health , University of Maryland School of Medicine , Baltimore , MD , USA
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12
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Karkossa F, Klein S. Assessing the influence of media composition and ionic strength on drug release from commercial immediate-release and enteric-coated aspirin tablets. J Pharm Pharmacol 2017; 69:1327-1340. [DOI: 10.1111/jphp.12777] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Accepted: 05/28/2017] [Indexed: 12/01/2022]
Abstract
Abstract
Objectives
The objective of this test series was to elucidate the importance of selecting the right media composition for a biopredictive in-vitro dissolution screening of enteric-coated dosage forms.
Methods
Drug release from immediate-release (IR) and enteric-coated (EC) aspirin formulations was assessed in phosphate-based and bicarbonate-based media with different pH, electrolyte composition and ionic strength.
Key findings
Drug release from aspirin IR tablets was unaffected by media composition. In contrast, drug release from EC aspirin formulations was affected by buffer species and ionic strength. In all media, drug release increased with increasing ionic strength, but in bicarbonate-based buffers was delayed when compared with that in phosphate-based buffers. Interestingly, the cation species in the dissolution medium had also a clear impact on drug release. Drug release profiles obtained in Blank CarbSIF, a new medium simulating pH and average ionic composition of small intestinal fluid, were different from those obtained in all other buffer compositions studied.
Conclusions
Results from this study in which the impact of various media parameters on drug release of EC aspirin formulations was systematically screened clearly show that when developing predictive dissolution tests, it is important to simulate the ionic composition of intraluminal fluids as closely as possible.
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Affiliation(s)
- Frank Karkossa
- Department of Pharmacy, Institute of Biopharmaceutics and Pharmaceutical Technology, Center of Drug Absorption and Transport (C_DAT), University of Greifswald, Greifswald, Germany
| | - Sandra Klein
- Department of Pharmacy, Institute of Biopharmaceutics and Pharmaceutical Technology, Center of Drug Absorption and Transport (C_DAT), University of Greifswald, Greifswald, Germany
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13
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Escherichia coli EDL933 requires gluconeogenic nutrients to successfully colonize the intestines of streptomycin-treated mice precolonized with E. coli Nissle 1917. Infect Immun 2015; 83:1983-91. [PMID: 25733524 DOI: 10.1128/iai.02943-14] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Accepted: 02/20/2015] [Indexed: 11/20/2022] Open
Abstract
Escherichia coli MG1655, a K-12 strain, uses glycolytic nutrients exclusively to colonize the intestines of streptomycin-treated mice when it is the only E. coli strain present or when it is confronted with E. coli EDL933, an O157:H7 strain. In contrast, E. coli EDL933 uses glycolytic nutrients exclusively when it is the only E. coli strain in the intestine but switches in part to gluconeogenic nutrients when it colonizes mice precolonized with E. coli MG1655 (R. L. Miranda et al., Infect Immun 72:1666-1676, 2004, http://dx.doi.org/10.1128/IAI.72.3.1666-1676.2004). Recently, J. W. Njoroge et al. (mBio 3:e00280-12, 2012, http://dx.doi.org/10.1128/mBio.00280-12) reported that E. coli 86-24, an O157:H7 strain, activates the expression of virulence genes under gluconeogenic conditions, suggesting that colonization of the intestine with a probiotic E. coli strain that outcompetes O157:H7 strains for gluconeogenic nutrients could render them nonpathogenic. Here we report that E. coli Nissle 1917, a probiotic strain, uses both glycolytic and gluconeogenic nutrients to colonize the mouse intestine between 1 and 5 days postfeeding, appears to stop using gluconeogenic nutrients thereafter in a large, long-term colonization niche, but continues to use them in a smaller niche to compete with invading E. coli EDL933. Evidence is also presented suggesting that invading E. coli EDL933 uses both glycolytic and gluconeogenic nutrients and needs the ability to perform gluconeogenesis in order to colonize mice precolonized with E. coli Nissle 1917. The data presented here therefore rule out the possibility that E. coli Nissle 1917 can starve the O157:H7 E. coli strain EDL933 of gluconeogenic nutrients, even though E. coli Nissle 1917 uses such nutrients to compete with E. coli EDL933 in the mouse intestine.
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Nausea, Vomiting, and Noninflammatory Diarrhea. MANDELL, DOUGLAS, AND BENNETT'S PRINCIPLES AND PRACTICE OF INFECTIOUS DISEASES 2015. [PMCID: PMC7173487 DOI: 10.1016/b978-1-4557-4801-3.00100-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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Merchant HA, Goyanes A, Parashar N, Basit AW. Predicting the gastrointestinal behaviour of modified-release products: utility of a novel dynamic dissolution test apparatus involving the use of bicarbonate buffers. Int J Pharm 2014; 475:585-91. [PMID: 25195730 DOI: 10.1016/j.ijpharm.2014.09.003] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Revised: 09/02/2014] [Accepted: 09/03/2014] [Indexed: 11/25/2022]
Abstract
The establishment of physiologically relevant in vitro-in vivo correlations (IV-IVCs) is key for any biorelevant dissolution test. Historically, bicarbonate buffers have produced better correlations than compendial phosphate buffered media, though such tests are usually performed at a constant pH experiment, overlooking the notion that the pH of the luminal fluids is variable and fluctuating. In this work, we have devised a dynamic dissolution test method employing a physiological bicarbonate buffer under pH conditions of the proximal gut in order to assess the dissolution behaviour of various enteric polymer-coated (gastro-resistant) prednisolone tablets. The pH of the media is modulated and controlled by an Auto pH System™ which exploits the physiological equilibria between [H2CO3] and [HCO3(-)], to match it to the aboral change in pH with transit of the dosage form through the proximal small intestine (from pH 5.6 up to 6.8). The lag time values for an accelerated release and standard EUDRAGIT(®) L30D-55 coated formulation (25 min and 60 min, respectively) were close to the previously reported initial tablet disintegration time data obtained in-vivo by γ-scintigraphy (28 min and 66 min, respectively). Dissolution of alternative delayed release coated products was also better discriminated in the dynamic buffer system. These data confirm the dynamic dissolution system provides a robust and reliable platform to predict the in vivo fate of oral products in a laboratory setting.
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Affiliation(s)
- Hamid A Merchant
- Department of Pharmaceutics, UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London WC1N 1AX, UK.
| | - Alvaro Goyanes
- Department of Pharmaceutics, UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London WC1N 1AX, UK
| | - Narendra Parashar
- Department of Pharmaceutics, UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London WC1N 1AX, UK
| | - Abdul W Basit
- Department of Pharmaceutics, UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London WC1N 1AX, UK.
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Adediran J, Leatham-Jensen MP, Mokszycki ME, Frimodt-Møller J, Krogfelt KA, Kazmierczak K, Kenney LJ, Conway T, Cohen PS. An Escherichia coli Nissle 1917 missense mutant colonizes the streptomycin-treated mouse intestine better than the wild type but is not a better probiotic. Infect Immun 2014; 82:670-82. [PMID: 24478082 PMCID: PMC3911375 DOI: 10.1128/iai.01149-13] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2013] [Accepted: 11/18/2013] [Indexed: 01/08/2023] Open
Abstract
Previously we reported that the streptomycin-treated mouse intestine selected for two different Escherichia coli MG1655 mutants with improved colonizing ability: nonmotile E. coli MG1655 flhDC deletion mutants that grew 15% faster in vitro in mouse cecal mucus and motile E. coli MG1655 envZ missense mutants that grew slower in vitro in mouse cecal mucus yet were able to cocolonize with the faster-growing flhDC mutants. The E. coli MG1655 envZ gene encodes a histidine kinase that is a member of the envZ-ompR two-component signal transduction system, which regulates outer membrane protein profiles. In the present investigation, the envZP41L gene was transferred from the intestinally selected E. coli MG1655 mutant to E. coli Nissle 1917, a human probiotic strain used to treat gastrointestinal infections. Both the E. coli MG1655 and E. coli Nissle 1917 strains containing envZP41L produced more phosphorylated OmpR than their parents. The E. coli Nissle 1917 strain containing envZP41L also became more resistant to bile salts and colicin V and grew 50% slower in vitro in mucus and 15% to 30% slower on several sugars present in mucus, yet it was a 10-fold better colonizer than E. coli Nissle 1917. However, E. coli Nissle 1917 envZP41L was not better at preventing colonization by enterohemorrhagic E. coli EDL933. The data can be explained according to our "restaurant" hypothesis for commensal E. coli strains, i.e., that they colonize the intestine as sessile members of mixed biofilms, obtaining the sugars they need for growth locally, but compete for sugars with invading E. coli pathogens planktonically.
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Affiliation(s)
- Jimmy Adediran
- Department of Cell and Molecular Biology, University of Rhode Island, Kingston, Rhode Island, USA
| | - Mary P. Leatham-Jensen
- Department of Cell and Molecular Biology, University of Rhode Island, Kingston, Rhode Island, USA
| | - Matthew E. Mokszycki
- Department of Cell and Molecular Biology, University of Rhode Island, Kingston, Rhode Island, USA
| | - Jakob Frimodt-Møller
- Department of Microbiological Surveillance and Research, Statens Serum Institut, Copenhagen, Denmark
| | - Karen A. Krogfelt
- Department of Microbiological Surveillance and Research, Statens Serum Institut, Copenhagen, Denmark
| | - Krystyna Kazmierczak
- Jesse Brown Veterans Administration Medical Center, Chicago, Illinois, USA
- Department of Microbiology, University of Illinois—Chicago, Chicago, Illinois, USA
- Mechanobiology Institute, National University of Singapore, Singapore, Singapore
| | - Linda J. Kenney
- Jesse Brown Veterans Administration Medical Center, Chicago, Illinois, USA
- Department of Microbiology, University of Illinois—Chicago, Chicago, Illinois, USA
- Mechanobiology Institute, National University of Singapore, Singapore, Singapore
| | - Tyrrell Conway
- Department of Microbiology and Plant Biology, University of Oklahoma, Norman, Oklahoma, USA
| | - Paul S. Cohen
- Department of Cell and Molecular Biology, University of Rhode Island, Kingston, Rhode Island, USA
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Leatham-Jensen MP, Frimodt-Møller J, Adediran J, Mokszycki ME, Banner ME, Caughron JE, Krogfelt KA, Conway T, Cohen PS. The streptomycin-treated mouse intestine selects Escherichia coli envZ missense mutants that interact with dense and diverse intestinal microbiota. Infect Immun 2012; 80:1716-27. [PMID: 22392928 PMCID: PMC3347456 DOI: 10.1128/iai.06193-11] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2011] [Accepted: 02/16/2012] [Indexed: 01/07/2023] Open
Abstract
Previously, we reported that the streptomycin-treated mouse intestine selected nonmotile Escherichia coli MG1655 flhDC deletion mutants of E. coli MG1655 with improved colonizing ability that grow 15% faster in vitro in mouse cecal mucus and 15 to 30% faster on sugars present in mucus (M. P. Leatham et al., Infect. Immun. 73:8039-8049, 2005). Here, we report that the 10 to 20% remaining motile E. coli MG1655 are envZ missense mutants that are also better colonizers of the mouse intestine than E. coli MG1655. One of the flhDC mutants, E. coli MG1655 ΔflhD, and one of the envZ missense mutants, E. coli MG1655 mot-1, were studied further. E. coli MG1655 mot-1 is more resistant to bile salts and colicin V than E. coli MG1655 ΔflhD and grows ca. 15% slower in vitro in mouse cecal mucus and on several sugars present in mucus compared to E. coli MG1655 ΔflhD but grows 30% faster on galactose. Moreover, E. coli MG1655 mot-1 and E. coli MG1655 ΔflhD appear to colonize equally well in one intestinal niche, but E. coli MG1655 mot-1 appears to use galactose to colonize a second, smaller intestinal niche either not colonized or colonized poorly by E. coli MG1655 ΔflhD. Evidence is also presented that E. coli MG1655 is a minority member of mixed bacterial biofilms in the mucus layer of the streptomycin-treated mouse intestine. We offer a hypothesis, which we call the "Restaurant" hypothesis, that explains how nutrient acquisition in different biofilms comprised of different anaerobes can account for our results.
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Affiliation(s)
- Mary P. Leatham-Jensen
- Department of Cell and Molecular Biology, University of Rhode Island, Kingston, Rhode Island, USA
| | - Jakob Frimodt-Møller
- Department of Microbiological Surveillance and Research, Statens Serum Institut, Copenhagen S, Denmark
| | - Jimmy Adediran
- Department of Cell and Molecular Biology, University of Rhode Island, Kingston, Rhode Island, USA
| | - Matthew E. Mokszycki
- Department of Cell and Molecular Biology, University of Rhode Island, Kingston, Rhode Island, USA
| | - Megan E. Banner
- Department of Cell and Molecular Biology, University of Rhode Island, Kingston, Rhode Island, USA
| | - Joyce E. Caughron
- Department of Botany and Microbiology, University of Oklahoma, Norman, Okloahoma, USA
| | - Karen A. Krogfelt
- Department of Microbiological Surveillance and Research, Statens Serum Institut, Copenhagen S, Denmark
| | - Tyrrell Conway
- Department of Botany and Microbiology, University of Oklahoma, Norman, Okloahoma, USA
| | - Paul S. Cohen
- Department of Cell and Molecular Biology, University of Rhode Island, Kingston, Rhode Island, USA
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Liu F, Merchant HA, Kulkarni RP, Alkademi M, Basit AW. Evolution of a physiological pH6.8 bicarbonate buffer system: Application to the dissolution testing of enteric coated products. Eur J Pharm Biopharm 2011; 78:151-7. [DOI: 10.1016/j.ejpb.2011.01.001] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2010] [Revised: 01/04/2011] [Accepted: 01/11/2011] [Indexed: 11/24/2022]
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Sack RB. The discovery of cholera - like enterotoxins produced by Escherichia coli causing secretory diarrhoea in humans. Indian J Med Res 2011; 133:171-80. [PMID: 21415491 PMCID: PMC3089048] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Non-vibrio cholera has been recognized as a clinical entity for as long as cholera was known to be caused by Vibrio cholerae. Until 1968, the aetiologic agent of this syndrome was not known. Following a series of studies in patients with non-vibrio cholera it was found that these patients had large concentrations of Escherichia coli in the small bowel and stools which produced cholera toxin-like enterotoxins, and had fluid and electrolyte transport abnormalities in the small bowel similar to patients with documented cholera. Furthermore, these patients developed antibodies to the cholera-like enterotoxin. Later studies showed that these strains, when fed to volunteers produced a cholera-like disease and that two enterotoxins were found to be produced by these organisms: a heat-labile enterotoxin (LT) which is nearly identical to cholera toxin, and a heat-stable enterotoxin (ST), a small molecular weight polypeptide. E. coli that produced one or both of these enterotoxins were designated enterotoxigenic E. coli (ETEC). ETEC are now known not only to cause a severe cholera-like illness, but to be the most common bacterial cause of acute diarrhoea in children in the developing world, and to be the most common cause of travellers' diarrhoea in persons who visit the developing world.
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Affiliation(s)
- R. Bradley Sack
- Johns Hopkins University, Bloomberg School of Public Health, Baltimore, Maryland, USA,Reprint requests: Dr R. Bradley Sack, Department of International Health, Johns Hopkins University, Bloomberg School of Public Health 615 North Wolfe Street, Room W5953, Baltimore, Maryland, 21205, USA e-mail:
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20
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Mudie DM, Amidon GL, Amidon GE. Physiological parameters for oral delivery and in vitro testing. Mol Pharm 2010; 7:1388-405. [PMID: 20822152 DOI: 10.1021/mp100149j] [Citation(s) in RCA: 305] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Pharmaceutical solid oral dosage forms must undergo dissolution in the intestinal fluids of the gastrointestinal tract before they can be absorbed and reach the systemic circulation. Therefore, dissolution is a critical part of the drug-delivery process. The rate and extent of drug dissolution and absorption depend on the characteristics of the active ingredient as well as properties of the dosage form. Just as importantly, characteristics of the physiological environment such as buffer species, pH, bile salts, gastric emptying rate, intestinal motility, and hydrodynamics can significantly impact dissolution and absorption. While significant progress has been made since 1970 when the first compendial dissolution test was introduced (USP apparatus 1), current dissolution testing does not take full advantage of the extensive physiologic information that is available. For quality control purposes, where the question is one of lot-to-lot consistency in performance, using nonphysiologic test conditions that match drug and dosage form properties with practical dissolution media and apparatus may be appropriate. However, where in vitro-in vivo correlations are desired, it is logical to consider and utilize knowledge of the in vivo condition. This publication critically reviews the literature that is relevant to oral human drug delivery. Physiologically relevant information must serve as a basis for the design of dissolution test methods and systems that are more representative of the human condition. As in vitro methods advance in their physiological relevance, better in vitro-in vivo correlations will be possible. This will, in turn, lead to in vitro systems that can be utilized to more effectively design dosage forms that have improved and more consistent oral bioperformance.
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Affiliation(s)
- Deanna M Mudie
- College of Pharmacy, University of Michigan, Ann Arbor, MI 48109-1065, USA
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21
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Fadda HM, Merchant HA, Arafat BT, Basit AW. Physiological bicarbonate buffers: stabilisation and use as dissolution media for modified release systems. Int J Pharm 2009; 382:56-60. [DOI: 10.1016/j.ijpharm.2009.08.003] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2009] [Revised: 07/29/2009] [Accepted: 08/03/2009] [Indexed: 11/27/2022]
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22
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Sheng JJ, McNamara DP, Amidon GL. Toward an in vivo dissolution methodology: a comparison of phosphate and bicarbonate buffers. Mol Pharm 2009; 6:29-39. [PMID: 19183104 DOI: 10.1021/mp800148u] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The purpose of this research was to evaluate the difference between the pharmaceutical phosphate buffers and the gastrointestinal bicarbonates in dissolution of ketoprofen and indomethacin, to illustrate the dependence of buffer differential on biopharmaceutical properties of BCS II weak acids, and to recommend phosphate buffers equivalent to bicarbonates. The intrinsic dissolution rates of ketoprofen and indomethacin were experimentally measured using a rotating disk method at 37 degrees C in USP SIF/FaSSIF and various concentrations of bicarbonates. Theoretical models including an improved reaction plane model and a film model were applied to estimate the surrogate phosphate buffers equivalent to the bicarbonates. Experimental results show that the intrinsic dissolution rates of ketoprofen and indomethacin in USP and FaSSIF phosphate buffers are 1.5-3.0 times that in the 15 mM bicarbonates. Theoretical analysis demonstrates that the buffer differential is largely dependent on the drug pK(a) and second on solubility, and weakly dependent on the drug diffusivity. Further, in accordance with the drug pK(a), solubility and diffusivity, a simple phosphate surrogate was proposed to match an average bicarbonate value (15 mM) of the upper gastrointestinal region. Specifically, phosphate buffers of 13-15 mM and 3-4 mM were recommended for ketoprofen and indomethacin, respectively. For both ketoprofen and indomethacin, the intrinsic dissolution using the phosphate surrogate buffers closely approximated the 15 mM bicarbonate buffer. This work demonstrates the substantial difference between pharmaceutical phosphates and physiological bicarbonates in determining the drug intrinsic dissolution rates of BCS II weak acids, such as ketoprofen and indomethacin. Surrogate phosphates were recommended in order to closely reflect the in vivo dissolution of ketoprofen and indomethacin in gastrointestinal bicarbonates, which has significant implications for defining buffer systems for BCS II weak acids in developing in vitro bioequivalence dissolution methodology.
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Affiliation(s)
- Jennifer J Sheng
- College of Pharmacy, University of Michigan, Ann Arbor, Michigan 48109-1065, USA
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23
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Liu F, Lizio R, Meier C, Petereit HU, Blakey P, Basit AW. A novel concept in enteric coating: A double-coating system providing rapid drug release in the proximal small intestine. J Control Release 2009; 133:119-24. [DOI: 10.1016/j.jconrel.2008.09.083] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2008] [Revised: 09/10/2008] [Accepted: 09/19/2008] [Indexed: 10/21/2022]
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24
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Gut instincts: Explorations in intestinal physiology and drug delivery. Int J Pharm 2008; 364:213-26. [DOI: 10.1016/j.ijpharm.2008.05.012] [Citation(s) in RCA: 280] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2008] [Revised: 05/03/2008] [Accepted: 05/06/2008] [Indexed: 12/12/2022]
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25
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Dubost DC, Kaufman MJ, Jahansouz H, Brenner GS. Physicochemical Characterization of L-691, 121, a Potent and Selective Class III Antiarrhythmic Agent. Drug Dev Ind Pharm 2008. [DOI: 10.3109/03639049609065917] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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26
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Gauger EJ, Leatham MP, Mercado-Lubo R, Laux DC, Conway T, Cohen PS. Role of motility and the flhDC Operon in Escherichia coli MG1655 colonization of the mouse intestine. Infect Immun 2007; 75:3315-24. [PMID: 17438023 PMCID: PMC1932950 DOI: 10.1128/iai.00052-07] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Previously, we reported that the mouse intestine selected mutants of Escherichia coli MG1655 that have improved colonizing ability (M. P. Leatham et al., Infect. Immun. 73:8039-8049, 2005). These mutants grew 10 to 20% faster than their parent in mouse cecal mucus in vitro and 15 to 30% faster on several sugars found in the mouse intestine. The mutants were nonmotile and had deletions of various lengths beginning immediately downstream of an IS1 element located within the regulatory region of the flhDC operon, which encodes the master regulator of flagellum biosynthesis, FlhD(4)C(2). Here we show that during intestinal colonization by wild-type E. coli strain MG1655, 45 to 50% of the cells became nonmotile by day 3 after feeding of the strain to mice and between 80 and 90% of the cells were nonmotile by day 15 after feeding. Ten nonmotile mutants isolated from mice were sequenced, and all were found to have flhDC deletions of various lengths. Despite this strong selection, 10 to 20% of the E. coli MG1655 cells remained motile over a 15-day period, suggesting that there is an as-yet-undefined intestinal niche in which motility is an advantage. The deletions appear to be selected in the intestine for two reasons. First, genes unrelated to motility that are normally either directly or indirectly repressed by FlhD(4)C(2) but can contribute to maximum colonizing ability are released from repression. Second, energy normally used to synthesize flagella and turn the flagellar motor is redirected to growth.
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Affiliation(s)
- Eric J Gauger
- Department of Cell and Molecular Biology, University of Rhode Island, Kingston, RI 02881, USA
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Ibekwe VC, Fadda HM, Parsons GE, Basit AW. A comparative in vitro assessment of the drug release performance of pH-responsive polymers for ileo-colonic delivery. Int J Pharm 2006; 308:52-60. [PMID: 16356670 DOI: 10.1016/j.ijpharm.2005.10.038] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2005] [Revised: 10/17/2005] [Accepted: 10/18/2005] [Indexed: 11/19/2022]
Abstract
The aim of this study was to investigate the in vitro dissolution characteristics of pH-responsive polymers in a variety of simulated fluids. Prednisolone tablets were fabricated and coated with the following polymer systems: Eudragit S (organic solution), Eudragit S (aqueous dispersion), Eudragit FS (aqueous dispersion) and Eudragit P4135 (organic solution). Dissolution tests were conducted using a pH change method whereby tablets were transferred from acid to buffer. Three different buffer media were investigated: two compendial phosphate buffers (pH range 6.8-7.4) and a physiological buffer solution (Hanks buffer) with very similar ionic composition to intestinal fluid (pH 7.4). There was considerable drug release from tablets coated with Eudragit P4135 in acid, prompting discontinuation of further investigations of this polymer. Eudragit S (organic solution), Eudragit S (aqueous dispersion) and Eudragit FS on the other hand prevented drug release in acid, though subsequent drug release in the buffer media was found to be influenced by the duration of tablet exposure to acid. At pH 7.4 drug release rate from the polymer coated tablets was similar in the two compendial media, however in the physiological buffer, they were found to differ in the following order: Eudragit S (aqueous dispersion)>Eudragit FS>Eudragit S (organic solution). The results indicate that the tablets coated with the newer Eudragit FS polymer would be more appropriate for drug delivery to the ileo-colonic region in comparison to the more established Eudragit S. More importantly, however, dissolution in the physiological buffer was found to be markedly slower for all the coated tablets than in the two compendial buffers, a result akin to reported slower dissolution of enteric coated tablets in vivo. There is therefore the need to adequately simulate the ionic composition of the intestinal fluid in the dissolution media.
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Affiliation(s)
- Valentine C Ibekwe
- Department of Pharmaceutics, The School of Pharmacy, University of London, 29/39 Brunswick Square, London WC1N 1AX, UK
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29
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Fadda H, Basit A. Dissolution of pH responsive formulations in media resembling intestinal fluids: bicarbonate versus phosphate buffers. J Drug Deliv Sci Technol 2005. [DOI: 10.1016/s1773-2247(05)50049-2] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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30
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Vertzoni M, Fotaki N, Kostewicz E, Stippler E, Leuner C, Nicolaides E, Dressman J, Reppas C. Dissolution media simulating the intralumenal composition of the small intestine: physiological issues and practical aspects. J Pharm Pharmacol 2004; 56:453-62. [PMID: 15099440 DOI: 10.1211/0022357022935] [Citation(s) in RCA: 180] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
The objective of this study was to test various aspects of dissolution media simulating the intralumenal composition of the small intestine, including the suitability of the osmolality-adjusting agents and of the buffers, the substitution of crude sodium taurocholate (from ox bile) for pure sodium taurocholate and the substitution of partially hydrolysed soybean phosphatidylcholine for egg phosphatidylcholine. It was concluded that biorelevant media should contain sodium as the major cation species to better reflect the physiology. However, the use of non-physiologically relevant buffers is inevitable, especially for simulation of the fed state in the small intestine. The buffers used may affect the solubility product of weakly basic compounds with pK(a)(s) higher than about 5, the solubility of extremely highly lipophilic compounds due to salting in/out properties of the anion of the buffer and the stability of the dissolving compound. It is prudent in relevant situations to run an additional dissolution test in a modified fed state simulated intestinal fluid (FeSSIF) (or fasted state simulated intestinal fluid (FaSSIF), where applicable) containing alternative buffer species. Although a mixture of bile salts is physiologically more relevant than pure sodium taurocholate, this issue seems to be of practical importance in only a few cases. Adequate simulations in these cases will probably require the use of a number of pure substances and could substantially increase the cost of the test. Finally, unless the drug is extremely lipophilic (ca. logP> 5), egg phosphatidylcholine can be substituted by partially hydrolysed soybean phosphatidylcholine.
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Affiliation(s)
- Maria Vertzoni
- Laboratory of Biopharmaceutics and Pharmacokinetics, University of Athens, Athens, Greece
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31
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Møller AK, Leatham MP, Conway T, Nuijten PJM, de Haan LAM, Krogfelt KA, Cohen PS. An Escherichia coli MG1655 lipopolysaccharide deep-rough core mutant grows and survives in mouse cecal mucus but fails to colonize the mouse large intestine. Infect Immun 2003; 71:2142-52. [PMID: 12654836 PMCID: PMC152069 DOI: 10.1128/iai.71.4.2142-2152.2003] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The ability of E. coli strains to colonize the mouse large intestine has been correlated with their ability to grow in cecal and colonic mucus. In the present study, an E. coli MG1655 strain was mutagenized with a mini-Tn5 Km (kanamycin) transposon, and mutants were tested for the ability to grow on agar plates with mouse cecal mucus as the sole source of carbon and nitrogen. One mutant, designated MD42 (for mucus defective), grew poorly on cecal-mucus agar plates but grew well on Luria agar plates and on glucose minimal-agar plates. Sequencing revealed that the insertion in MD42 was in the waaQ gene, which is involved in lipopolysaccharide (LPS) core biosynthesis. Like "deep-rough" E. coli mutants, MD42 was hypersensitive to sodium dodecyl sulfate (SDS), bile salts, and the hydrophobic antibiotic novobiocin. Furthermore, its LPS core oligosaccharide was truncated, like that of a deep-rough mutant. MD42 initially grew in the large intestines of streptomycin-treated mice but then failed to colonize (<10(2) CFU per g of feces), whereas its parent colonized at levels between 10(7) and 10(8) CFU per g of feces. When mouse cecal mucosal sections were hybridized with an E. coli-specific rRNA probe, MD42 was observed in cecal mucus as clumps 24 h postfeeding, whereas its parent was present almost exclusively as single cells, suggesting that clumping may play a role in preventing MD42 colonization. Surprisingly, MD42 grew nearly as well as its parent during growth in undiluted, highly viscous cecal mucus isolated directly from the mouse cecum and, like its parent, survived well after reaching stationary phase, suggesting that there are no antimicrobials in mucus that prevent MD42 colonization. After mini-mariner transposon mutagenesis, an SDS-resistant suppressor mutant of MD42 was isolated. The mini-mariner insertion was shown to be in the bipA gene, a known regulator of E. coli surface components. When grown in Luria broth, the LPS core of the suppressor mutant remained truncated; however, the LPS core was not truncated when the suppressor mutant was grown in the presence of SDS. Moreover, when the suppressor mutant was grown in the presence of SDS and fed to mice, it colonized the mouse large intestine. Collectively, the data presented here suggest that BipA may play a role in E. coli MG1655 LPS core biosynthesis and that because MD42 forms clumps in intestinal mucus, it is unable to colonize the mouse large intestine.
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Affiliation(s)
- Annette K Møller
- Department of Cell and Molecular Biology, University of Rhode Island, Kingston, RI 02881, USA
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Fleckenstein JM, Lindler LE, Elsinghorst EA, Dale JB. Identification of a gene within a pathogenicity island of enterotoxigenic Escherichia coli H10407 required for maximal secretion of the heat-labile enterotoxin. Infect Immun 2000; 68:2766-74. [PMID: 10768971 PMCID: PMC97486 DOI: 10.1128/iai.68.5.2766-2774.2000] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Studies of the pathogenesis of enterotoxigenic Escherichia coli (ETEC) have largely centered on extrachromosomal determinants of virulence, in particular the plasmid-encoded heat-labile (LT) and heat-stable enterotoxins and the colonization factor antigens. ETEC causes illnesses that range from mild diarrhea to severe cholera-like disease. These differences in disease severity are not readily accounted for by our current understanding of ETEC pathogenesis. Here we demonstrate that Tia, a putative adhesin of ETEC H10407, is encoded on a large chromosomal element of approximately 46 kb that shares multiple features with previously described E. coli pathogenicity islands. Further analysis of the region downstream from tia revealed the presence of several candidate open reading frames (ORFs) in the same transcriptional orientation as tia. The putative proteins encoded by these ORFs bear multiple motifs associated with bacterial secretion apparatuses. An in-frame deletion in one candidate gene identified here as leoA (labile enterotoxin output) resulted in marked diminution of secretion of the LT enterotoxin and lack of fluid accumulation in a rabbit ileal loop model of infection. Although previous studies have suggested that E. coli lacks the capacity to secrete LT, our studies show that maximal release of LT from the periplasm of H10407 is dependent on one or more elements encoded on a pathogenicity island.
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Affiliation(s)
- J M Fleckenstein
- Medicine Service, Veterans Affairs Medical Center, Memphis, Tennessee 38104, USA.
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Fleckenstein JM, Kopecko DJ, Warren RL, Elsinghorst EA. Molecular characterization of the tia invasion locus from enterotoxigenic Escherichia coli. Infect Immun 1996; 64:2256-65. [PMID: 8675335 PMCID: PMC174064 DOI: 10.1128/iai.64.6.2256-2265.1996] [Citation(s) in RCA: 104] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Enterotoxigenic Escherichia coli (ETEC) shares with other diarrheal pathogens the capacity to invade epithelial cell lines originating from the human ileum or colon, although the role of invasion in ETEC pathogenesis remains undefined. Two distinct loci (tia and tib) that direct noninvasive E. coli to adhere to and invade intestinal epithelial cell lines have previously been isolated from cosmid libraries of the classical ETEC strain H10407. Here, we report the molecular characterization of the tia locus. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of cellular fractions of E. coli DH5alpha carrying the tia-positive cosmids and recombinant plasmid subclones revealed that this locus directs the production of a 25-kDa protein (the Tia protein) that is localized to the outer membrane. The tia locus was subcloned to a maximum of 2 kb and mutagenized with bacteriophage Mud. Synthesis of this protein was directly correlated with the ability of subclones and Mud transposon mutants to adhere to and invade epithelial cells. Sequencing of the tia locus identified a 756-bp open reading frame. All transposon insertions resulting in an invasion-negative phenotype mapped to this open reading frame. The open reading frame was amplified and directionally cloned behind the lac promoter of pHG165. This construct directed DHalpha to express a 25-kDa protein and to adhere to and invade epithelial cells. The role of the tia gene in directing epithelial adherence and invasion was further assessed by the construction of chromosomal tia deletion derivatives of the parent ETEC strain, H10407. These tia deletion strains were noninvasive and lacked the ability to adhere to human ileocecal cells. The tia gene shares limited homology with the Yersinia ail locus and significant homology with the hra1 agglutinin gene cloned from a porcine ETEC strain. Additionally, tia probes hybridized to geographically diverse ETEC strains, as well as some enteropathogenic E. coli, enteroaggregative E. coli, and Shigella sonnei strains.
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Affiliation(s)
- J M Fleckenstein
- Department of Medicine, Walter Reed Army Medical Center, Washington, D.C. 20307-5001, USA
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Ashford M, Fell JT, Attwood D, Woodhead PJ. An in vitro investigation into the suitability of pH-dependent polymers for colonic targeting. Int J Pharm 1993. [DOI: 10.1016/0378-5173(93)90344-f] [Citation(s) in RCA: 111] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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Elsinghorst EA, Kopecko DJ. Molecular cloning of epithelial cell invasion determinants from enterotoxigenic Escherichia coli. Infect Immun 1992; 60:2409-17. [PMID: 1587608 PMCID: PMC257174 DOI: 10.1128/iai.60.6.2409-2417.1992] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Although penetration of the epithelial mucosa has not been identified as a virulence mechanism in enterotoxigenic Escherichia coli (ETEC), we have found that this pathogen is capable of invading human intestinal cell lines. Classical ETEC strain H10407 was most invasive for epithelial cell lines derived from ileocecal and colonic tissues. An ETEC cosmid library was screened for clones that could direct E. coli HB101 to invade cultured human ileocecal epithelial cells (HCT 8 cells). Three invasive recombinant cosmid clones were isolated. These cosmids could direct HB101 invasion at an efficiency that was equal to or greater than that of the parent ETEC strain. The invasion cosmids also allowed for enhanced HCT 8 cell adherence by HB101. Electron micrographs of ETEC and recombinant HB101 strains revealed intracellular bacteria contained within endocytic vacuoles. Restriction endonuclease mapping and hybridization analyses showed that the three ETEC clones represent two separate invasion systems present in the parent ETEC strain and that both systems are chromosomally encoded. The parent ETEC strain and one cloned invasion system did not invade HeLa cells. Interestingly, one cloned invasion system was capable of directing HB101 to invade HeLa cells. Invasion of HCT 8 cells by recombinant HB101 strains and the parent ETEC strain was inhibited by cytochalasin D, indicating that the wild-type and both cloned invasion systems trigger an actin polymerization-dependent uptake process. It is not known whether the invasive phenotype of ETEC is relevant for enterotoxigenic disease. However, the parent ETEC strain, as well as recombinant HB101 strains, was capable of transcytosis through polarized HCT 8 monolayers. This transcytosis suggests that ETEC may cross the gut epithelium in vivo and that this invasion may have a previously unrecognized role in the disease process.
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Affiliation(s)
- E A Elsinghorst
- Department of Bacterial Immunology, Walter Reed Army Institute of Research, Washington, D.C. 20307-5100
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Mezoff AG, Giannella RA, Eade MN, Cohen MB. Escherichia coli enterotoxin (STa) binds to receptors, stimulates guanyl cyclase, and impairs absorption in rat colon. Gastroenterology 1992; 102:816-22. [PMID: 1347028 DOI: 10.1016/0016-5085(92)90163-s] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
To determine the contribution of the colon in Escherichia coli heat-stable enterotoxin-mediated diarrheal disease, toxin binding, guanyl cyclase activation, and toxin-induced water flux in the rat colon and ileum were compared. Scatchard analysis suggested a single class of heat-stable enterotoxin receptors with an affinity constant of binding of 10(9) L/mol in both colonocytes and ileocytes; however, the number of toxin receptors per cell was 3.5-fold greater in coloncytes than ileocytes (8.32 +/- 1.33 x 10(5) vs. 2.33 +/- 0.28 x 10(5) receptors per cell; P = 0.02). Heat-stable enterotoxin stimulated guanyl cyclase activation in an identical dose-dependent manner in proximal colonic and ileal membranes, with similar sensitivity and maximum response. Heat-stable enterotoxin also inhibited net water flux to a similar degree in both colon and ileum (-47.8 vs. -48.4 microL.cm-1.h-1, respectively) at a dose of 8 nmol/L. At this dose in the colon, because of a higher baseline of absorption, absorption continued, but at a diminished level. At this dose in the ileum, heat-stable enterotoxin induced net secretion. These data are consistent with the concept that heat-stable enterotoxin-induced diarrheal disease results from a decreased absorptive capacity in the colon in the face of increased small intestinal fluid secretion.
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Affiliation(s)
- A G Mezoff
- Division of Pediatric Gastroenterology, Children's Hospital Research Foundation, Cincinnati, Ohio
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Tantisira MH, Jodal M, Lundgren O. Effects of heat-stable Escherichia coli enterotoxin on intestinal alkaline secretion and transepithelial potential difference in the rat intestines in vivo. Scand J Gastroenterol 1990; 25:19-28. [PMID: 2406887 DOI: 10.3109/00365529008999205] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The effects of the heat-stable enterotoxin of Escherichia coli (STa) on intestinal alkaline secretion and transepithelial electric potential difference (PD) were investigated in vivo in denervated segments of rat jejunum, ileum, and proximal colon. STa caused a significant increase in alkaline secretion in the jejunum but not in the ileum or colon. The jejunal effect of STa may be ascribed to a stimulation of bicarbonate secretion and/or an inhibition of Na+/H+ exchange. With regard to PD, STa caused a marked rise in colonic PD, whereas only a small response was found in the jejunum. No effect on PD was seen in the ileum. Hexamethonium (10 mg/kg intravenously) significantly diminished the effects of STa on PD, whereas only a small inhibition of the STa-induced alkaline secretion was observed. The effect of lidocaine on PD and alkaline secretion was found to be similar to that of hexamethonium. Atropine had no effect on any of the studied variables. These findings suggest that STa exerts, via nerves, a profound influence on the jejunal transport mechanisms responsible for the changes in PD, whereas the influence on alkaline secretion is to a large extent not mediated via enteric nerves. Thus, the extent of enteric nervous control of epithelial function differs for different transport functions. The findings also indicate that the bicarbonate ion is not the anion mainly responsible for the fluid secretion elicited by STa.
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Abstract
Three hundred million people, mostly tourists, participate in international travel each year. Development of an acute diarrheal syndrome abroad, while returning home, or shortly after arriving home is referred to as traveler's diarrhea (TD). TD is not a specific diagnosis but, rather, a clinical syndrome with multiple etiologies. In this article, clinical and epidemiological features of TD, specific etiologies and their pathogenesis, as well as current means of diagnosis, treatment, and prevention will be reviewed.
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Pessina A, Neri MG, Muschiato A. Effect of heat-labile enterotoxin(LT) produced by Escherichia coli on in vitro cell proliferation. EXPERIENTIA 1982; 38:1056-7. [PMID: 6751857 DOI: 10.1007/bf01955364] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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Read NW, Read MG, Krejs GJ, Hendler RS, Davis G, Fordtran JS. A report of five patients with large-volume secretory diarrhea but no evidence of endocrine tumor or laxative abuse. Dig Dis Sci 1982; 27:193-201. [PMID: 7075417 DOI: 10.1007/bf01296914] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The purpose of this paper is to report five patients with chronic secretory diarrhea (maximum stool volume greater than 1 liter per day, duration 6 weeks to 8 years) in whom we could find no evidence of an endocrine tumor or of surreptitious laxative ingestion. All except one had severe hypokalemia. There was apparent improvement after treatment with prednisone in two patients and loperamide in one. The diarrhea resolved spontaneously in three patients and has undergone several temporary remissions in one patient. The last patient died after a severe unremitting illness. Extensive investigations failed to establish the etiology, but intestinal perfusion (carried out in four of the five patients) revealed secretion or abnormally low absorption of water and electrolytes in the jejunum and abnormally low absorption in the colon. The management of patients with chronic watery diarrhea is discussed.
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Burns TW, Mathias JR, Carlson GM, Martin JL, Shields RP. Effect of toxigenic Escherichia coli on myoelectric activity of small intestine. THE AMERICAN JOURNAL OF PHYSIOLOGY 1978; 235:E311-5. [PMID: 358839 DOI: 10.1152/ajpendo.1978.235.3.e311] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
When exposed to cholera toxin (CT), distal ileal loops of the rabbit small intestine showed an alteration in myoelectric activity. This alteration was defined as the migrating action potential complex (MAPC). The purpose of this study was to determine, using myoelectric recording techniques, the effects of live toxigenic Escherichia coli (TEC) on motility. Live TEC, live nontoxigenic E. coli (NTEC), and culture filtrates of these organisms were studied. Live TEC and its filtrate induced MAPC activity similar to that of CT. Live TEC induced a mean of 3.8 MAPCs/h, significantly greater than induced by live NTEC. TEC filtrate induced a mean of 14.2 MAPCs/h, significantly greater than NTEC filtrate. Heating the TEC filtrate to 100 degrees C before use resulted in a significant decrease of MAPC activity. This experiment demonstrated that live TEC and its culture filtrate altered ileal myoelectric activity. The effect may have been mediated by a heat-labile enterotoxin. This study suggests that alterations in small intestinal motility may be important in the pathogenesis of TEC diarrhea.
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Richards KL, Douglas SD. Pathophysiological effects of Vibrio cholerae and enterotoxigenic Escherichia coli and their exotoxins on eucaryotic cells. Microbiol Rev 1978; 42:592-613. [PMID: 82199 PMCID: PMC281445 DOI: 10.1128/mr.42.3.592-613.1978] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Hamilton DL, Roe WE, Nielsen NO. Effect of heat stable and heat labile Escherichia coli enterotoxins, cholera toxin and theophylline on unidirectional sodium and chloride fluxes in the proximal and distal jejunum of weanling swine. CANADIAN JOURNAL OF COMPARATIVE MEDICINE : REVUE CANADIENNE DE MEDECINE COMPAREE 1977; 41:306-17. [PMID: 332292 PMCID: PMC1277595] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Acute, isolated loops of proximal and distal jejunum of weanling swine were exposed to either heat stable porcine Escherichia coli enterotoxin, heat labile porcine Escherichia coli enterotoxin, cholera toxin or theophylline. Unidirectional sodium fluxes in response to heat stable in the proximal jejunum were dependent on the length of time that the intestinal mucosae was exposed to the enterotoxin. Net water, sodium and chloride and unidirectional sodium and chloride flux measurements in the proximal jejunum in response to each agent uniformly indicated that net secretion of fluid and electrolytes was the result of increased unidirectional sodium secretion or blood-to-lumen flux and decreased unidirectional chloride absorption or lumen-to-blood flux. In addition heat stable cholera toxin and theophylline but not heat labile decreased unidirectional chloride secretion a small but significant amount in the proximal jejunum. Sodium and chloride flux measurements in the distal jejunum demonstrated that all four secretory agents could stimulate net secretion of water, sodium and chloride in that region. The response to these secretory agents as measured by sodium and chloride unidirectional flux rates was not similar to changes observed in the proximal jejunum. In the distal small intestine, whereas heat labile cholera toxin and theophylline induced similar qualitative changes in unidirectional sodium and chloride fluxes, that induced by heat stable differed.
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Neto UF, Toccalino H, Dujovney F. Stool bacterial aerobic overgrowth in the small intestine of children with acute diarrhoea. ACTA PAEDIATRICA SCANDINAVICA 1976; 65:609-15. [PMID: 961412 DOI: 10.1111/j.1651-2227.1976.tb04940.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The aerobic flora of 2 groups of children (normal and with malnutrition) with acute diarrhoea was studied, by intubation of the upper and middle small intestine and by stool culture. All the 27 children studied presented bacterial concentrations of 10(5) germs/ml at one or both levels studied. In 9 cases enteropathogen bacteria e were isolated from stools, and in 6 of these they were also found in the small intestine. The results show the elevated incidence of overgrowth of the small intestinal aerobic flora in children with acute diarrhoea. This fact is mentioned as another etiological factor to be taken into consideration in this pathology.
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Klipstein FA, Horowitz IR, Engert RF, Schnenk EA. Effect of Klebsiella pneumoniae enterotoxin on intestinal transport in the rat. J Clin Invest 1975; 56:799-807. [PMID: 169297 PMCID: PMC301934 DOI: 10.1172/jci108158] [Citation(s) in RCA: 34] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The effects on intestinal transport of either a semipurified preparation of enterotoxin elaborated by Klebsiella pneumoniae or similaryly prepared control material were tested by marker perfusion studies in the small intestine of rats. At a concentration of 2 mg/ml, the enterotoxin produced net secretion of water, Na, and Cl in both jejunal and ileal segments; HCO3 transport was not affected. Net secretion was evident within 30 min after intorduction of the toxin and was maximal after 90 min. The addition of 56 mM glucose to the enterotoxin-containing perfusion fluid resulted in reversal of water and Na transport to net absorption in both intestinal segments. The enterotoxin also produced a significant depression of xylose absorption in both the jejunum and ileum but did not affect the absorption of either glucose or L-leucine. Intestinal structure was not altered after perfusion of the toxin but insillation of approximately one-quarter of the total perfusion dose into a ligated jejunal loop for 18 h produced fluid secretion and structural abnormalities. These observations confirm the fact that other species of coliform bacteria in addition to tescherichia coli are capable of elaborating an enterotoxin. Such species commonly contaminate the small intestine of persons with tropical sprue and it is suggested that chronic exposure of the intestinal mucosa to the enterotoxin elaborated by these bacteria may be a factor in the pathogenesis of intestinal abnormalities in thid disorder.
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Guggenbichler JP, Stickler GB. [Old and new data on diarrhetic diseases in childhood I. Etiology and pathophysiology]. Infection 1975; 3:127-42. [PMID: 770335 DOI: 10.1007/bf01641335] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Etiology and Pathophysiology. The present article is a comprehensive review of recent research results in the field of acute diarrhea. The most important new idea in contrast to older views is that almost all acute diarrheas are associated with a disturbance of intestinal bacterial homeostasis: overgrowth of the small intestine with apathogenic or pathogenic organisms is followed by changes in intestinal metabolism with increase in intestinal water and electrolyte secretion. Anaerobic organisms cause by enzymatic deconugation and dydroxylation of bile acids secretion of fluid into the small intestine and inhibition of fluid absorption from the large intestine. 10-OH-fatty acids, which are formed intraluminally by enzymatic hydroxylation of long-chain unsaturated fatty acids from the diet by similar anaerobic organisms, produce profuse secretion of fluid into the small intestine. The ability of numerous strains of E. coli to produce enterotoxin, which has a qualitatively similar action to cholera toxin, is now considered to be a major cause of infantile diarrhea. The separation of two completely different pathophysiologic mechanisms of E. Coli, the enterotoxic and the enteroinvasive action which are determined by extranuclear chromosomal material, is an important result of recent research. Overgrowth of the small intestine with different bacteria is followed by loss of actiivity of lactase, and later of all disaccharidases in the intestinal mucosa.
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Abstract
In a group of 133 United States students studied for 18 days after arriving in Mexico, diarrhea developed in 38 (29 per cent). Diarrhea rarely began before the fourth day, and the mean onset was 13 days after arrival. Symptoms lasted an average of 3.4 days but persisted in 21 per cent of sick students. Heat-labile enterotoxin-producing Escheria coli was found in the stools of 72 per cent of sick and 15 per cent of healthy students. None had heat-labile Esch. coli when they entered Mexico. The incubation period was short, generally 24 to 48 hours, and the carrier state was five days or less in 82 per cent of students surveyed. Entamoeba histolytica was found in 6 per cent of cases of diarrhea, but not salmonella, shigella or penetrating Esch. coli. These studies suggest that approximately 70 per cent of travelers' diarrhea in Mexico is associated with heat-labile toxigenic strains of Esch. coli.
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