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Okuno M, Tsuru N, Yoshino S, Gotoh Y, Yamamoto T, Hayashi T, Ogura Y. Isolation and Genomic Characterization of a Heat-Labile Enterotoxin 1-Producing Escherichia fergusonii Strain from a Human. Microbiol Spectr 2023; 11:e0049123. [PMID: 37432125 PMCID: PMC10434266 DOI: 10.1128/spectrum.00491-23] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Accepted: 06/23/2023] [Indexed: 07/12/2023] Open
Abstract
Escherichia fergusonii strains have been isolated from patients with diarrhea, but their virulence determinant has not been well elucidated. Here, we report the first isolation of a heat-labile enterotoxin 1 (LT1)-producing E. fergusonii strain (strain 30038) from a patient in Japan. The complete genome sequence of strain 30038 was determined and subjected to comparative genomics and phylogenetic analyses with 195 publicly available genomes of E. fergusonii. In addition to strain 30038, the elt1 gene was also identified in an E. fergusonii strain that is phylogenetically distinct and which was isolated from poultry in the United Kingdom. Fine genomic comparison revealed that these two strains share comparable elt1-bearing plasmids. However, an intriguing distinction arises in strain 30038, wherein the plasmid has integrated into the chromosome via a recombination process mediated by an insertion sequence. The production of active LT1 toxin by strain 30038 was verified through an in vitro assay using cultured cells. A large plasmid carrying 11 antimicrobial resistance genes was also identified in strain 30038. Our results indicate that extensive surveillance of elt1-positive E. fergusonii strains as diarrheagenic pathogens is needed. IMPORTANCE Escherichia fergusonii, a species closely related to Escherichia coli, is known to cause sporadic conditions in humans, including diarrhea. However, the critical virulence factors in E. fergusonii clinical isolates remain to be identified. This study shows the first isolation of an E. fergusonii strain carrying the elt1 gene, which encodes heat-labile enterotoxin 1, from a patient with diarrhea. Our analysis of public databases also revealed the presence of elt1-positive E. fergusonii strains isolated from poultry in the United Kingdom. Interestingly, while the elt1 gene in the poultry isolate was present on a large plasmid, in the human isolate it was integrated into the chromosome, which may confer stability on the elt1-carrying genetic element. Our findings highlight the need for extensive surveillance of elt1-positive E. fergusonii strains in livestock animals.
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Affiliation(s)
- Miki Okuno
- Division of Microbiology, Department of Infectious Medicine, Kurume University School of Medicine, Kurume, Japan
| | - Nami Tsuru
- Miyazaki Prefectural Institute for Public Health and Environment, Miyazaki, Japan
| | - Shuji Yoshino
- Miyazaki Prefectural Institute for Public Health and Environment, Miyazaki, Japan
| | - Yasuhiro Gotoh
- Department of Bacteriology, Faculty of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Takeshi Yamamoto
- Division of Microbiology, Department of Infectious Medicine, Kurume University School of Medicine, Kurume, Japan
| | - Tetsuya Hayashi
- Department of Bacteriology, Faculty of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Yoshitoshi Ogura
- Division of Microbiology, Department of Infectious Medicine, Kurume University School of Medicine, Kurume, Japan
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Kaushik H, Deshmukh SK, Solanki AK, Bhatia B, Tiwari A, Garg LC. Immunization with recombinant fusion of LTB and linear epitope (40-62) of epsilon toxin elicits protective immune response against the epsilon toxin of Clostridium perfringens type D. AMB Express 2019; 9:105. [PMID: 31300915 PMCID: PMC6626085 DOI: 10.1186/s13568-019-0824-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Accepted: 06/26/2019] [Indexed: 11/10/2022] Open
Abstract
Epsilon toxin (Etx) produced by Clostridium perfringens types B and D, a major causative agent of enterotoxaemia causes significant economic losses to animal industry. Conventional vaccines against these pathogens generally employ formalin-inactivated culture supernatants. However, immunization with the culture supernatant and full length toxin subjects the animal to antigenic load and often have adverse effect due to incomplete inactivation of the toxins. In the present study, an epitope-based vaccine against Clostridium perfringens Etx, comprising 40-62 amino acid residues of the toxin in translational fusion with heat labile enterotoxin B subunit (LTB) of E. coli, was evaluated for its protective potential. The ability of the fusion protein rLTB.Etx40-62 to form pentamers and biologically active holotoxin with LTA of E. coli indicated that the LTB present in the fusion protein retained its biological activity. Antigenicity of both the components in the fusion protein was retained as anti-fusion protein antisera detected both the wild type Etx and LTB in Western blot analysis. Immunization of BALB/c mice with the fusion protein resulted in a significant increase in all isotypes, predominantly IgG1, IgG2a and IgG2b. Anti-fusion protein antisera neutralized the cytotoxicity of epsilon toxin both in vitro and in vivo. Thus, the results demonstrate the potential of rLTB.Etx40-62 as a candidate vaccine against C. perfringens.
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Madec S, Pichereau V, Jacq A, Paillard M, Boisset C, Guérard F, Paillard C, Nicolas JL. Characterization of the secretomes of two vibrios pathogenic to mollusks. PLoS One 2014; 9:e113097. [PMID: 25401495 PMCID: PMC4234667 DOI: 10.1371/journal.pone.0113097] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Accepted: 10/19/2014] [Indexed: 02/05/2023] Open
Abstract
Vibrio tapetis causes the brown ring disease in the Japanese clam Ruditapes philippinarum while Vibrio aestuarianus is associated with massive oyster mortalities. As extracellular proteins are often associated with the virulence of pathogenic bacteria, we undertook a proteomic approach to characterize the secretomes of both vibrios. The extracellular proteins (ECPs) of both species were fractionated by SEC-FPLC and in vitro assays were performed to measure the effects of each fraction on hemocyte cellular parameters (phagocytosis and adhesion). Fractions showing a significant effect were subjected to SDS-PAGE, and proteins were identified by nano LC-MS/MS. 45 proteins were identified for V. aestuarianus and 87 for V. tapetis. Most of them belonged to outer membrane or were periplasmic, including porins or adhesins that were already described as virulence factors in other bacterial species. Others were transporter components, flagella proteins, or proteins of unknown function (14 and 15 respectively). Interestingly, for V. aestuarianus, we noted the secretion of 3 extracellular enzymes including the Vam metalloprotease and two other enzymes (one putative lipase and one protease). For V. tapetis, we identified five extracellular enymes, i.e. two different endochitinases, one protease, one lipase and an adhesin. A comparison of both secretomes also showed that only the putative extracellular lipase was common to both secretomes, underscoring the difference in pathogenicity mechanisms between these two species. Overall, these results characterize for the first time the secretomes of these two marine pathogenic vibrios and constitute a useful working basis to further analyze the contribution of specific proteins in the virulence mechanisms of these species.
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Affiliation(s)
- Stéphanie Madec
- Laboratoire Universitaire de Biodiversité et Ecologie Microbienne (EA3882), SFR48 ScInBios, Université de Bretagne Occidentale (UBO), UEB, ESIAB, Technopôle Brest Iroise, 29280, Plouzané, France
| | - Vianney Pichereau
- Laboratoire des Sciences de l’Environnement Marin, UMR 6539 UBO/CNRS/IRD/Ifremer, Université de Bretagne Occidentale (UBO), Institut Universitaire Européen de la Mer, Technopôle Brest Iroise, 29280, Plouzané, France
| | - Annick Jacq
- Institut de Génétique et de Microbiologie, UMR8621, CNRS-Université Paris-Sud, 91405, Orsay, France
| | - Mathieu Paillard
- Laboratoire des Sciences de l’Environnement Marin, UMR 6539 UBO/CNRS/IRD/Ifremer, Université de Bretagne Occidentale (UBO), Institut Universitaire Européen de la Mer, Technopôle Brest Iroise, 29280, Plouzané, France
| | - Claire Boisset
- Centre de Recherche sur les macromolécules végétales, CERMAV-CNRS, BP53, 38041 Grenoble, France
| | - Fabienne Guérard
- Laboratoire des Sciences de l’Environnement Marin, UMR 6539 UBO/CNRS/IRD/Ifremer, Université de Bretagne Occidentale (UBO), Institut Universitaire Européen de la Mer, Technopôle Brest Iroise, 29280, Plouzané, France
| | - Christine Paillard
- Laboratoire des Sciences de l’Environnement Marin, UMR 6539 UBO/CNRS/IRD/Ifremer, Université de Bretagne Occidentale (UBO), Institut Universitaire Européen de la Mer, Technopôle Brest Iroise, 29280, Plouzané, France
| | - Jean-Louis Nicolas
- Laboratoire des Sciences de l’Environnement Marin, UMR 6539 UBO/CNRS/IRD/Ifremer, Université de Bretagne Occidentale (UBO), Institut Universitaire Européen de la Mer, Technopôle Brest Iroise, 29280, Plouzané, France
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Hamorsky KT, Kouokam JC, Bennett LJ, Baldauf KJ, Kajiura H, Fujiyama K, Matoba N. Rapid and scalable plant-based production of a cholera toxin B subunit variant to aid in mass vaccination against cholera outbreaks. PLoS Negl Trop Dis 2013; 7:e2046. [PMID: 23505583 PMCID: PMC3591335 DOI: 10.1371/journal.pntd.0002046] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2012] [Accepted: 12/18/2012] [Indexed: 12/20/2022] Open
Abstract
INTRODUCTION Cholera toxin B subunit (CTB) is a component of an internationally licensed oral cholera vaccine. The protein induces neutralizing antibodies against the holotoxin, the virulence factor responsible for severe diarrhea. A field clinical trial has suggested that the addition of CTB to killed whole-cell bacteria provides superior short-term protection to whole-cell-only vaccines; however, challenges in CTB biomanufacturing (i.e., cost and scale) hamper its implementation to mass vaccination in developing countries. To provide a potential solution to this issue, we developed a rapid, robust, and scalable CTB production system in plants. METHODOLOGY/PRINCIPAL FINDINGS In a preliminary study of expressing original CTB in transgenic Nicotiana benthamiana, the protein was N-glycosylated with plant-specific glycans. Thus, an aglycosylated CTB variant (pCTB) was created and overexpressed via a plant virus vector. Upon additional transgene engineering for retention in the endoplasmic reticulum and optimization of a secretory signal, the yield of pCTB was dramatically improved, reaching >1 g per kg of fresh leaf material. The protein was efficiently purified by simple two-step chromatography. The GM1-ganglioside binding capacity and conformational stability of pCTB were virtually identical to the bacteria-derived original B subunit, as demonstrated in competitive enzyme-linked immunosorbent assay, surface plasmon resonance, and fluorescence-based thermal shift assay. Mammalian cell surface-binding was corroborated by immunofluorescence and flow cytometry. pCTB exhibited strong oral immunogenicity in mice, inducing significant levels of CTB-specific intestinal antibodies that persisted over 6 months. Moreover, these antibodies effectively neutralized the cholera holotoxin in vitro. CONCLUSIONS/SIGNIFICANCE Taken together, these results demonstrated that pCTB has robust producibility in Nicotiana plants and retains most, if not all, of major biological activities of the original protein. This rapid and easily scalable system may enable the implementation of pCTB to mass vaccination against outbreaks, thereby providing better protection of high-risk populations in developing countries.
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Affiliation(s)
- Krystal Teasley Hamorsky
- Owensboro Cancer Research Program, Owensboro, Kentucky, United States of America
- Department of Pharmacology and Toxicology and James Graham Brown Cancer Center, University of Louisville School of Medicine, Louisville, Kentucky, United States of America
| | - J. Calvin Kouokam
- Owensboro Cancer Research Program, Owensboro, Kentucky, United States of America
- Department of Pharmacology and Toxicology and James Graham Brown Cancer Center, University of Louisville School of Medicine, Louisville, Kentucky, United States of America
| | - Lauren J. Bennett
- Owensboro Cancer Research Program, Owensboro, Kentucky, United States of America
| | - Keegan J. Baldauf
- Department of Pharmacology and Toxicology and James Graham Brown Cancer Center, University of Louisville School of Medicine, Louisville, Kentucky, United States of America
| | - Hiroyuki Kajiura
- International Center for Biotechnology, Osaka University, Osaka, Japan
| | - Kazuhito Fujiyama
- International Center for Biotechnology, Osaka University, Osaka, Japan
| | - Nobuyuki Matoba
- Owensboro Cancer Research Program, Owensboro, Kentucky, United States of America
- Department of Pharmacology and Toxicology and James Graham Brown Cancer Center, University of Louisville School of Medicine, Louisville, Kentucky, United States of America
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Wang YK, Huang SC, Wu YF, Chen YC, Lin YL, Nayak M, Lin YR, Chen WH, Chiu YR, Li TTH, Yeh BS, Wu TK. Site-directed mutations of thermostable direct hemolysin from Grimontia hollisae alter its arrhenius effect and biophysical properties. Int J Biol Sci 2011; 7:333-46. [PMID: 21494434 PMCID: PMC3076507 DOI: 10.7150/ijbs.7.333] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2011] [Accepted: 03/23/2011] [Indexed: 11/23/2022] Open
Abstract
Recombinant thermostable direct hemolysin from Grimontia hollisae (Gh-rTDH) exhibits paradoxical Arrhenius effect, where the hemolytic activity is inactivated by heating at 60 °C but is reactivated by additional heating above 80 °C. This study investigated individual or collective mutational effect of Tyr53, Thr59, and Ser63 positions of Gh-rTDH on hemolytic activity, Arrhenius effect, and biophysical properties. In contrast to the Gh-rTDH wild-type (Gh-rTDH(WT)) protein, a 2-fold decrease of hemolytic activity and alteration of Arrhenius effect could be detected from the Gh-rTDH(Y53H/T59I) and Gh-rTDH(T59I/S63T) double-mutants and the Gh-rTDH(Y53H/T59I/S63T) triple-mutant. Differential scanning calorimetry results showed that the Arrhenius effect-loss and -retaining mutants consistently exhibited higher and lower endothermic transition temperatures, respectively, than that of the Gh-rTDH(WT). Circular dichroism measurements of Gh-rTDH(WT) and Gh-rTDH(mut) showed a conspicuous change from a β-sheet to α-helix structure around the endothermic transition temperature. Consistent with the observation is the conformational change of the proteins from native globular form into fibrillar form, as determined by Congo red experiments and transmission electron microscopy.
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Affiliation(s)
- Yu-Kuo Wang
- 1. Department of Biological Science and Technology, National Chiao Tung University, 30068, Hsin-Chu, Taiwan, Republic of China
| | - Sheng-Cih Huang
- 1. Department of Biological Science and Technology, National Chiao Tung University, 30068, Hsin-Chu, Taiwan, Republic of China
| | - Yi-Fang Wu
- 1. Department of Biological Science and Technology, National Chiao Tung University, 30068, Hsin-Chu, Taiwan, Republic of China
| | - Yu-Ching Chen
- 1. Department of Biological Science and Technology, National Chiao Tung University, 30068, Hsin-Chu, Taiwan, Republic of China
| | - Yen-Ling Lin
- 1. Department of Biological Science and Technology, National Chiao Tung University, 30068, Hsin-Chu, Taiwan, Republic of China
| | - Manoswini Nayak
- 1. Department of Biological Science and Technology, National Chiao Tung University, 30068, Hsin-Chu, Taiwan, Republic of China
| | - Yan Ren Lin
- 1. Department of Biological Science and Technology, National Chiao Tung University, 30068, Hsin-Chu, Taiwan, Republic of China
| | - Wen-Hung Chen
- 1. Department of Biological Science and Technology, National Chiao Tung University, 30068, Hsin-Chu, Taiwan, Republic of China
| | - Yi-Rong Chiu
- 1. Department of Biological Science and Technology, National Chiao Tung University, 30068, Hsin-Chu, Taiwan, Republic of China
| | - Thomas Tien-Hsiung Li
- 2. Institute of Biochemistry, National Chung Hsing University, 40227, Taichung, Taiwan, Republic of China
| | - Bo-Sou Yeh
- 3. Hsin Chu General Hospital, Department of Health, Executive Yuan, Taiwan, Republic of China
| | - Tung-Kung Wu
- 1. Department of Biological Science and Technology, National Chiao Tung University, 30068, Hsin-Chu, Taiwan, Republic of China
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Yuki Y, Tokuhara D, Nochi T, Yasuda H, Mejima M, Kurokawa S, Takahashi Y, Kataoka N, Nakanishi U, Hagiwara Y, Fujihashi K, Takaiwa F, Kiyono H. Oral MucoRice expressing double-mutant cholera toxin A and B subunits induces toxin-specific neutralising immunity. Vaccine 2009; 27:5982-8. [DOI: 10.1016/j.vaccine.2009.07.071] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2009] [Revised: 07/10/2009] [Accepted: 07/22/2009] [Indexed: 10/20/2022]
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Nochi T, Takagi H, Yuki Y, Yang L, Masumura T, Mejima M, Nakanishi U, Matsumura A, Uozumi A, Hiroi T, Morita S, Tanaka K, Takaiwa F, Kiyono H. Rice-based mucosal vaccine as a global strategy for cold-chain- and needle-free vaccination. Proc Natl Acad Sci U S A 2007; 104:10986-91. [PMID: 17573530 PMCID: PMC1904174 DOI: 10.1073/pnas.0703766104] [Citation(s) in RCA: 220] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2007] [Indexed: 11/18/2022] Open
Abstract
Capable of inducing antigen-specific immune responses in both systemic and mucosal compartments without the use of syringe and needle, mucosal vaccination is considered ideal for the global control of infectious diseases. In this study, we developed a rice-based oral vaccine expressing cholera toxin B subunit (CTB) under the control of the endosperm-specific expression promoter 2.3-kb glutelin GluB-1 with codon usage optimization for expression in rice seed. An average of 30 mug of CTB per seed was stored in the protein bodies, which are storage organelles in rice. When mucosally fed, rice seeds expressing CTB were taken up by the M cells covering the Peyer's patches and induced CTB-specific serum IgG and mucosal IgA antibodies with neutralizing activity. When expressed in rice, CTB was protected from pepsin digestion in vitro. Rice-expressed CTB also remained stable and thus maintained immunogenicity at room temperature for >1.5 years, meaning that antigen-specific mucosal immune responses were induced at much lower doses than were necessary with purified recombinant CTB. Because they require neither refrigeration (cold-chain management) nor a needle, these rice-based mucosal vaccines offer a highly practical and cost-effective strategy for orally vaccinating large populations against mucosal infections, including those that may result from an act of bioterrorism.
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Affiliation(s)
- Tomonori Nochi
- *Division of Mucosal Immunology, Department of Microbiology and Immunology, The Institute of Medical Science, University of Tokyo, Tokyo 108-8639, Japan
- Core Research for Evolutional Science and Technology, Japan Science and Technology Corporation, Saitama 332-0012, Japan
| | - Hidenori Takagi
- Transgenic Crop Research and Development Center, National Institute of Agrobiological Sciences, Ibaraki 305-8602, Japan
| | - Yoshikazu Yuki
- *Division of Mucosal Immunology, Department of Microbiology and Immunology, The Institute of Medical Science, University of Tokyo, Tokyo 108-8639, Japan
- Core Research for Evolutional Science and Technology, Japan Science and Technology Corporation, Saitama 332-0012, Japan
| | - Lijun Yang
- Transgenic Crop Research and Development Center, National Institute of Agrobiological Sciences, Ibaraki 305-8602, Japan
| | - Takehiro Masumura
- Laboratory of Genetic Engineering, Graduate School of Agriculture, Kyoto Prefectural University, Shimogamo, Kyoto 606-8522, Japan
- Kyoto Prefectural Institute of Agricultural Biotechnology, Seika-cho, Kyoto 619-0244, Japan; and
| | - Mio Mejima
- *Division of Mucosal Immunology, Department of Microbiology and Immunology, The Institute of Medical Science, University of Tokyo, Tokyo 108-8639, Japan
- Core Research for Evolutional Science and Technology, Japan Science and Technology Corporation, Saitama 332-0012, Japan
| | - Ushio Nakanishi
- *Division of Mucosal Immunology, Department of Microbiology and Immunology, The Institute of Medical Science, University of Tokyo, Tokyo 108-8639, Japan
| | - Akiko Matsumura
- *Division of Mucosal Immunology, Department of Microbiology and Immunology, The Institute of Medical Science, University of Tokyo, Tokyo 108-8639, Japan
- Core Research for Evolutional Science and Technology, Japan Science and Technology Corporation, Saitama 332-0012, Japan
| | - Akihiro Uozumi
- *Division of Mucosal Immunology, Department of Microbiology and Immunology, The Institute of Medical Science, University of Tokyo, Tokyo 108-8639, Japan
| | - Takachika Hiroi
- Department of Allergy and Immunology, Tokyo Metropolitan Institute of Medical Science, Tokyo 113-8613, Japan
| | - Shigeto Morita
- Laboratory of Genetic Engineering, Graduate School of Agriculture, Kyoto Prefectural University, Shimogamo, Kyoto 606-8522, Japan
- Kyoto Prefectural Institute of Agricultural Biotechnology, Seika-cho, Kyoto 619-0244, Japan; and
| | - Kunisuke Tanaka
- Laboratory of Genetic Engineering, Graduate School of Agriculture, Kyoto Prefectural University, Shimogamo, Kyoto 606-8522, Japan
- Kyoto Prefectural Institute of Agricultural Biotechnology, Seika-cho, Kyoto 619-0244, Japan; and
| | - Fumio Takaiwa
- Transgenic Crop Research and Development Center, National Institute of Agrobiological Sciences, Ibaraki 305-8602, Japan
| | - Hiroshi Kiyono
- *Division of Mucosal Immunology, Department of Microbiology and Immunology, The Institute of Medical Science, University of Tokyo, Tokyo 108-8639, Japan
- Core Research for Evolutional Science and Technology, Japan Science and Technology Corporation, Saitama 332-0012, Japan
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Kothary MH, McCardell BA, Frazar CD, Deer D, Tall BD. Characterization of the zinc-containing metalloprotease encoded by zpx and development of a species-specific detection method for Enterobacter sakazakii. Appl Environ Microbiol 2007; 73:4142-51. [PMID: 17483271 PMCID: PMC1932767 DOI: 10.1128/aem.02729-06] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Enterobacter sakazakii causes a severe form of neonatal meningitis that occurs as sporadic cases as well as outbreaks. The disease has been epidemiologically associated with consumption of reconstituted, dried infant formulas. Very little information is available regarding pathogenicity of the organism and production of virulence factors. Clinical and environmental strains were screened for production of factors which have activity against Chinese hamster ovary (CHO) cells in tissue culture. Polymyxin B lysate and sonicate preparations but not culture supernatants from the strains caused "rounding" of CHO cells. Subsequent studies showed that the CHO cell-rounding factor is a proteolytic enzyme that has activity against azocasein. The cell-bound protease was isolated by using a combination of polymyxin B lysis, followed by sonication of cells harvested from tryptone broth. The protease was purified to homogeneity by sequential ammonium sulfate precipitation, gel filtration chromatography with Sephadex G-100, hydrophobic interaction chromatography with phenyl-Sepharose CL-4B, and a second gel filtration with Sephadex G-100. In addition to activity against azocasein, the purified protease also exhibits activity against azocoll and insoluble casein but not elastin. The protease has a molecular weight of 38,000 and an isoelectric point of 4.4. It is heat labile and for maximal activity against azocasein has an optimum temperature of 37 degrees C and a pH range of 5 to 7. Proteolytic activity is inhibited by ortho-phenanthroline and Zincov but is not affected by phenylmethylsulfonyl fluoride, N-ethylmaleimide, and trypsin inhibitors, which demonstrates that the protease is a zinc-containing metalloprotease. The metalloprotease does not hemagglutinate chicken or sheep erythrocytes. Twenty-three to 27 of the first 42 N-terminal amino acid residues of the metalloprotease are identical to proteases produced by Serratia proteamaculans, Pectobacterium carotovorum, and Anabaena sp. PCR analysis using primers designed from a consensus nucleotide sequence showed that 135 E. sakazakii strains possessed the metalloprotease gene, zpx, and 25 non-E. sakazakii strains did not. The cloned zpx gene of strain 29544 consists of 1,026 nucleotides, and the deduced amino acid sequence of the metalloprotease has 341 amino acid residues, which corresponds to a theoretical protein size of 37,782 with a theoretical pI of 5.23. The sequence possesses three well-characterized zinc-binding and active-site motifs present in other bacterial zinc metalloproteases.
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Affiliation(s)
- M H Kothary
- MOD 1 Facility, Virulence Mechanisms Branch, Division of Virulence Assessment, OARSA, Center for Food Safety and Applied Nutrition, US Food and Drug Administration, Laurel, MD 20708, USA.
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Yeung PSM, Wiedmann M, Boor KJ. Evaluation of a tissue culture-based approach for differentiating between virulent and avirulent Vibrio parahaemolyticus strains based on cytotoxicity. J Food Prot 2007; 70:348-54. [PMID: 17340868 DOI: 10.4315/0362-028x-70.2.348] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The ability of only a subset of Vibrio parahaemolyticus strains to cause human infection underscores the need for an analytical method that can effectively differentiate between pathogenic strains and those that do not cause disease. We tested the feasibility of a tissue culture-based assay to determine whether clinical isolates could be differentiated from nonclinical isolates based on relative isolate cytopathogenicity. To screen for cytotoxic capability, we measured relative extracellular lactate dehydrogenase as an indicator of host cell damage in five different mammalian cell lines in the presence of V. parahaemolyticus. Isolates originating from clinical sources exhibited 15.5 to 59.3% relative cytotoxicity, whereas those originating from food sources exhibited 4.4 to 54.9% relative cytotoxicity. In the presence of -1.2 x 10(6) cells, cytotoxicity was 1.6- to 3.5-fold higher (P < 0.05) for clinical isolates than for nonclinical isolates in L2, Henle 407, and Caco-2 cell lines. V. parahaemolyticus serotype O3:K6 clinical isolates had 1.6- to 2.1-fold higher cytotoxicity than did the non-O3:K6 clinical isolates, with significantly higher cytotoxicity in HeLa, J774A.1, and Henle 407 cells than in L2 and Caco-2 cells. Because V. parahaemolyticus often is found in oysters, the effect of the presence of an oyster matrix on assay efficacy was also tested with L2 cells. The cytotoxicity elicited by a highly cytotoxic V. parahaemolyticus isolate was not affected by the presence of oyster tissue, suggesting that an oyster matrix will not interfere with assay sensitivity. In the present format, this assay can detect the presence of > 10(5) cells of a virulent V. parahaemolyticus strain in an oyster matrix.
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Affiliation(s)
- P S Marie Yeung
- Biological Sciences Department, California Polytechnic State University, San Luis Obispo, California 93407, USA.
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Curtis SK, Kothary MH, Blodgett RJ, Raybourne RB, Ziobro GC, Tall BD. Rugosity in Grimontia hollisae. Appl Environ Microbiol 2006; 73:1215-24. [PMID: 17189437 PMCID: PMC1828682 DOI: 10.1128/aem.02553-06] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Grimontia hollisae, formerly Vibrio hollisae, produces both smooth and rugose colonial variants. The rugose colony phenotype is characterized by wrinkled colonies producing copious amounts of exopolysaccharide. Cells from a rugose colony grown at 30 degrees C form rugose colonies, while the same cells grown at 37 degrees C form smooth colonies, which are characterized by a nonwrinkled, uncrannied appearance. Stress response studies revealed that after exposure to bleach for 30 min, rugose survivors outnumbered smooth survivors. Light scatter information obtained by flow cytometry indicated that rugose cells clumped into clusters of three or more cells (average, five cells) and formed two major clusters, while smooth cells formed only one cluster of single cells or doublets. Fluorescent lectin-binding flow cytometry studies revealed that the percentages of rugose cells that bound either wheat germ agglutinin (WGA) or Galanthus nivalis lectin (GNL) were greater than the percentages of smooth cells that bound the same lectins (WGA, 35% versus 3.5%; GNL, 67% versus 0.21%). These results indicate that the rugose exopolysaccharide consists partially of N-acetylglucosamine and mannose. Rugose colonies produced significantly more biofilm material than did smooth colonies, and rugose colonies grown at 30 degrees C produced more biofilm material than rugose colonies grown at 37 degrees C. Ultrastructurally, rugose colonies show regional cellular differentiation, with apical and lateral colonial regions containing cells embedded in a matrix stained by Alcian Blue. The cells touching the agar surface are packed tightly together in a palisade-like manner. The central region of the colony contains irregularly arranged, fluid-filled spaces and loosely packed chains or arrays of coccoid and vibrioid cells. Smooth colonies, in contrast, are flattened, composed of vibrioid cells, and lack distinct regional cellular differences. Results from suckling mouse studies showed that both orally fed rugose and smooth variants elicited significant, but similar, amounts of fluid accumulated in the stomach and intestines. These observations comprise the first report of expression and characterization of rugosity by G. hollisae and raise the possibility that expression of rugose exopolysaccharide in this organism is regulated at least in part by growth temperature.
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Affiliation(s)
- S K Curtis
- U.S. Food and Drug Administration, College Park, MD 20740, USA
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Sears CL, Kaper JB. Enteric bacterial toxins: mechanisms of action and linkage to intestinal secretion. Microbiol Rev 1996; 60:167-215. [PMID: 8852900 PMCID: PMC239424 DOI: 10.1128/mr.60.1.167-215.1996] [Citation(s) in RCA: 189] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- C L Sears
- Division of Infectious Diseases, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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