Karen A Krogfelt
SSI, Microbiology, Faculty Member
- Professor , reasearch in Medical microbiology, infectious diseases , mentor for students at MSc PhD levelsedit
This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for... more
This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes. Summary Background We hypothesize that perinatal exposures, in particular the human micro-biome and maternal nutrition during pregnancy, interact with the genetic predisposition to cause an abnormal immune modulation in early life towards a trajectory to chronic inflammatory diseases such as asthma and others. Objective The aim of this study is to explore these interactions by conducting a longitudinal
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Background and objectivesThe development of childhood asthma is associated with neonatal colonization with pathogenic bacteria in hypopharynx. Furthermore, established asthma is associated with systemic low‐grade inflammation. We here... more
Background and objectivesThe development of childhood asthma is associated with neonatal colonization with pathogenic bacteria in hypopharynx. Furthermore, established asthma is associated with systemic low‐grade inflammation. We here report on the association between neonatal colonization with pathogenic bacteria in hypopharynx and the development of systemic low‐grade inflammation.MethodsBacterial colonization of the hypopharynx with Moraxella catharralis, Haemophilus influenzae, and/or Streptococcus pneumoniae was assessed in asymptomatic children from the Copenhagen Prospective Studies on Asthma in Childhood2000 (COPSAC2000) cohort at age 1 month by culturing technique (N = 238) and by quantitative polymerase chain reaction (qPCR) technique (N = 249) and in the COPSAC2010 cohort by culturing at age 1 month (N = 622) and again at age 3 months (N = 613). Systemic low‐grade inflammation was determined in both cohorts at age 6 months by measuring plasma levels of high‐sensitivity C‐...
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Publisher Summary Understanding the physiology of bacteria grown in vivo in various hosts has been a difficult task. By using the adhesive properties of the microorganism, it is possible to isolate certain bacteria from their natural... more
Publisher Summary Understanding the physiology of bacteria grown in vivo in various hosts has been a difficult task. By using the adhesive properties of the microorganism, it is possible to isolate certain bacteria from their natural environment for further investigations. Pure cultures so obtained do not require growth on an artificial laboratory medium. The chapter describes the method for adhesin-dependent isolation and characterization of bacteria from their natural environment. It is performed by using a streptomycin-treated mouse as a host for a human Escherichia coli strain, producing type 1 fimbriae in vivo . Type 1 fimbriae bind specifically to D-mannose moieties. In this context, experiments were performed in which sepharose beads coupled with D-mannose were used for isolating bacterial cells from a fecal suspension, and/or from cecal mucus and cecal contents. Then, the isolated intact bacterial cells can be characterized by techniques such as electron microscopy, flow cytometry, and in situ hybridization. By electron microscopy, cell shape and surface components can be observed. A flow cytometer can be used for determining rapidly and with high precision the cell size of individual bacterial cells and the cell-size distribution in the isolated population. DNA content can be measured and the number of genomes per cell calculated. By in situ hybridization with labeled ribosomal RNA probes, the rRNA can be measured, which will reflect the metabolic activity of the bacterial cell in the host.
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persistence of Escherichia coli in urinary bladders
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Intestinal dysbiosis in inflammatory bowel disease (IBD) patients depend on disease activity. We aimed to characterize the microbiota after 7 years of follow-up in an unselected cohort of IBD patients according to disease activity and... more
Intestinal dysbiosis in inflammatory bowel disease (IBD) patients depend on disease activity. We aimed to characterize the microbiota after 7 years of follow-up in an unselected cohort of IBD patients according to disease activity and disease severity. Fifty eight Crohn’s disease (CD) and 82 ulcerative colitis (UC) patients were included. Disease activity was assessed by the Harvey-Bradshaw Index for CD and Simple Clinical Colitis Activity Index for UC. Microbiota diversity was assessed by 16S rDNA MiSeq sequencing. In UC patients with active disease and in CD patients with aggressive disease the richness (number of OTUs, p = 0.018 and p = 0.013, respectively) and diversity (Shannons index, p = 0.017 and p = 0.023, respectively) were significantly decreased. In the active UC group there was a significant decrease in abundance of the phylum Firmicutes (p = 0.018). The same was found in CD patients with aggressive disease (p = 0.05) while the abundance of Proteobacteria phylum showed ...
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Escherichia coli F-18, a normal human fecal isolate, is an excellent colonizer of the streptomycin-treated mouse large intestine. E. coli F-18 Col-, a derivative of E. coli F-18 which no longer makes the E. coli F-18 colicin, colonizes... more
Escherichia coli F-18, a normal human fecal isolate, is an excellent colonizer of the streptomycin-treated mouse large intestine. E. coli F-18 Col-, a derivative of E. coli F-18 which no longer makes the E. coli F-18 colicin, colonizes the large intestine as well as E. coli F-18 when fed to mice alone but is eliminated when fed together with E. coli F-18. Random sequences of E. coli F-18 DNA were cloned into pRLB2, a par-B-stabilized derivative of pHC79. The entire gene library was transformed into E. coli F-18 Col- and fed to streptomycin-treated mice. The mouse large intestine selected a predominant clone which contained a recombinant plasmid (pRLB7) that enhanced E. coli F-18 Col- colonizing ability 100-fold but did not stimulate colicin synthesis. Moreover, pRLB7 simultaneously improved the survival of E. coli F-18 Col- in stationary phase in vitro, utilizing nutrients derived from mouse cecal mucus, and stimulated synthesis of both type 1 fimbriae and three E. coli F-18 Col- ou...
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Pseudomonas aeruginosa AC869, a 3,5-dichlorobenzoate degrader, is a mouse pathogen and has a reported 50% lethal dose (LD50) of 1.05 x 10(7) CFU when given intranasally to C3H/HeJ mice (S.E. George, M.J. Kohan, M.I. Gilmour, M.S. Taylor,... more
Pseudomonas aeruginosa AC869, a 3,5-dichlorobenzoate degrader, is a mouse pathogen and has a reported 50% lethal dose (LD50) of 1.05 x 10(7) CFU when given intranasally to C3H/HeJ mice (S.E. George, M.J. Kohan, M.I. Gilmour, M.S. Taylor, H.G. Brooks, J.P. Creason, and L.D. Claxton, Appl. Environ, Microbiol. 59:3585-3591, 1993). AC869 was serotyped as O6 when grown in CD-1 mouse cecal and lung mucus but could not be assigned an O serotype when grown in Luria broth (LB). After growth in mouse cecal mucus, a less virulent mutant, AC869-11, was isolated from AC869 by using bacteriophage E79, which adsorbs to the O side chain of lipopolysaccharide (LPS). AC869-11 produced significantly less O antigen on its LPS than AC869 when grown in mouse lung and cecal mucus. The mutant also produced half the amount of exoenzyme S and 16-fold less extracellular protease than AC869 and was more sensitive than its parent to a number of antibiotics when grown either in LB or in mouse lung mucus. AC869-1...
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Growth rates of Escherichia coli BJ4 colonizing the large intestine of streptomycin-treated mice were estimated by quantitative hybridization with rRNA target probes and by epifluorescence microscopy. The ribosomal contents in bacteria... more
Growth rates of Escherichia coli BJ4 colonizing the large intestine of streptomycin-treated mice were estimated by quantitative hybridization with rRNA target probes and by epifluorescence microscopy. The ribosomal contents in bacteria isolated from the cecal mucus, cecal contents, and feces were measured and correlated with the ribosomal contents of bacteria growing in vitro at defined rates. The data suggest that E. coli BJ4 grows at an overall high rate in the intestine. However, when taking into account the total intestinal volume and numbers of bacteria present in cecal mucus, cecal contents, and feces, we suggest that E. coli BJ4 in the intestine consists of two populations, one in the mucus which has an apparent generation time of 40 to 80 min and one in the luminal contents which is static.
Research Interests: Microbiology, Bacteriology, Biology, Medicine, Cell Division, and 15 moreBiological Sciences, Escherichia coli, Mice, Female, Animals, Nucleic acid hybridization, Bacteria, ribosomal RNA, Feces, Mucus, Streptomycin, Base Sequence, Escherichia Coli Infections, Molecular Sequence Data, and Medical and Health Sciences
SUMMARYFollowing an unusually heavy rainfall in June 2009, a community-wide outbreak ofCampylobactergastroenteritis occurred in a small Danish town. The outbreak investigation consisted of (1) a cohort study using an e-questionnaire of... more
SUMMARYFollowing an unusually heavy rainfall in June 2009, a community-wide outbreak ofCampylobactergastroenteritis occurred in a small Danish town. The outbreak investigation consisted of (1) a cohort study using an e-questionnaire of disease determinants, (2) microbiological study of stool samples, (3) serological study of blood samples from cases and asymptomatic members of case households, and (4) environmental analyses of the water distribution system. The questionnaire study identified 163 cases (respondent attack rate 16%). Results showed a significant dose-response relationship between consumption of tap water and risk of gastroenteritis.Campylobacter jejunibelonging to two relatedflaAtypes were isolated from stool samples. Serum antibody levels againstCampylobacterwere significantly higher in cases than in asymptomatic persons. Water samples were positive for coliform bacteria, and the likely mode of contamination was found to be surface water leaking into the drinking-wate...
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The majority of microbes most probably exist in nature in close association with particular surfaces. The adhesive properties of microorganisms were first recognized at the beginning of this century. Since then it has been shown that... more
The majority of microbes most probably exist in nature in close association with particular surfaces. The adhesive properties of microorganisms were first recognized at the beginning of this century. Since then it has been shown that bacterial adhesion is important in plant and animal hosts, pathogenesis, medical devices, aquatic and soil ecosystems, biodegradation, and industrial processes.
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Owing to under-ascertainment it is difficult if not impossible to determine the incidence of a given disease based on cases notified to routine public health surveillance. This is especially true for diseases that are often present in... more
Owing to under-ascertainment it is difficult if not impossible to determine the incidence of a given disease based on cases notified to routine public health surveillance. This is especially true for diseases that are often present in mild forms as for example diarrhoea caused by foodborne bacterial infections. This study presents a Bayesian approach for obtaining incidence estimates by use of measurements of serum antibodies against Salmonella from a cross-sectional study. By comparing these measurements with antibody measurements from a follow-up study of infected individuals it was possible to estimate the time since last infection for each individual in the cross-sectional study. These time estimates were then converted into incidence estimates. Information about the incidence of Salmonella infections in Denmark was obtained by using blood samples from 1780 persons. The estimated incidence was about 0.094 infections per person year. This number corresponds to 325 infections per culture-confirmed case captured in the Danish national surveillance system. We present a novel approach, termed as seroincidence, that has potentials to compare the sensitivity of public health surveillance between different populations, countries and over time.
Research Interests: Algorithms, Incidence Geometry, Communicable Diseases, Adolescent, Antibodies, and 15 moreDenmark, Humans, Computer Simulation, Infectious Disease, Female, Confidence intervals, Estimation, Incidence, Danish, Aged, Longitudinal Studies, Lipopolysaccharides, Adult, Bayes Theorem, and Cross Sectional Studies
Research Interests: Microbiology, Immunology, Medical Microbiology, Biology, Medicine, and 15 moreWestern blotting, Escherichia coli, Immunization, Peptides, Microbial Pathogenesis, Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis, Peptide, Antiserum, Amino Acid Sequence, Epitopes, Enzyme Linked Immunosorbent Assay, Antigen, Fimbria, Molecular Sequence Data, and epitope
Three minor components of type 1 fimbriae, FimF, FimG and FimH have been characterized. These proteins are integrated in the fimbrial structure; are responsible for the adhesive properties of the fimbriae but are not necessary for the... more
Three minor components of type 1 fimbriae, FimF, FimG and FimH have been characterized. These proteins are integrated in the fimbrial structure; are responsible for the adhesive properties of the fimbriae but are not necessary for the production of fimbriae. Fimbriae were purified from different clones harbouring various combinations of the fimF, fimG and fimH genes in addition to the fimA gene. The FimF, FimG and FimH proteins were identified by two dimentional gel electrophoresis. They were found to have molecular weights of 18.0 kDa, 17.0 kDa and 30 kDa, respectively. The ratio of FimF, FimG and FimH components to the major subunit was less than 1:100. The fimH protein especially was present in very small quantities. Sera raised against fimbriae from two of the clones (HB101/pPKL5 and HB101/pPKL4) were found by immunoblotting to be specific respectively for the major structural protein only (FimA), and for all components.
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SUMMARYThe incidence of reported infections of non-typhoidSalmonellais affected by biases inherent to passive laboratory surveillance, whereas analysis of blood sera may provide a less biased alternative to estimate the force... more
SUMMARYThe incidence of reported infections of non-typhoidSalmonellais affected by biases inherent to passive laboratory surveillance, whereas analysis of blood sera may provide a less biased alternative to estimate the force ofSalmonellatransmission in humans. We developed a mathematical model that enabled a back-calculation of the annual seroincidence ofSalmonellabased on measurements of specific antibodies. The aim of the present study was to determine the seroincidence in two convenience samples from 2012 (Danish blood donors,n= 500, and pregnant women,n= 637) and a community-based sample of healthy individuals from 2006 to 2007 (n= 1780). The lowest antibody levels were measured in the samples from the community cohort and the highest in pregnant women. The annualSalmonellaseroincidences were 319 infections/1000 pregnant women [90% credibility interval (CrI) 210–441], 182/1000 in blood donors (90% CrI 85–298) and 77/1000 in the community cohort (90% CrI 45–114). Although the di...
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Escherichia coli F-18, isolated from the feces of a healthy human, makes type 1 fimbriae and is an excellent colonizer of the streptomycin-treated mouse large intestine. Recently, it was shown that the inability to produce type 1 fimbriae... more
Escherichia coli F-18, isolated from the feces of a healthy human, makes type 1 fimbriae and is an excellent colonizer of the streptomycin-treated mouse large intestine. Recently, it was shown that the inability to produce type 1 fimbriae had no effect on the ability of E. coli F-18 to colonize the streptomycin-treated mouse large intestine, suggesting the possibility that E. coli F-18 does not express type 1 fimbriae in vivo. However, we show here that E. coli F-18 does express type 1 fimbriae in mouse cecal mucus in vivo and, in fact, appears to express substantially more type 1 fimbriae in cecal mucus in vivo than in L broth in vitro.
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Escherichia coli BJ4, a rat isolate, was used to examine the growth and differentiation of the microorganism in its natural habitat, the intestine. Growth of E. coli BJ4 in the large intestine of streptomycin-treated mice was compared... more
Escherichia coli BJ4, a rat isolate, was used to examine the growth and differentiation of the microorganism in its natural habitat, the intestine. Growth of E. coli BJ4 in the large intestine of streptomycin-treated mice was compared with its growth in laboratory media. By a number of methods, it was shown that E. coli BJ4 differentiates, during growth in the intestine, into two distinct populations, one that has the characteristics of the laboratory-grown strain and one that appears as a coccoid cell. Furthermore, it was shown that there is a natural selection for the coccoid-type cell in the intestine, while in laboratory media growth of rod-shaped E. coli BJ4 is enhanced.
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Type 1 fimbriae of Escherichia coli are surface organelles which mediate binding to D-mannose-containing structures. By direct binding of FimH to D-mannose attached to a carrier protein, we demonstrated that this protein was uniquely... more
Type 1 fimbriae of Escherichia coli are surface organelles which mediate binding to D-mannose-containing structures. By direct binding of FimH to D-mannose attached to a carrier protein, we demonstrated that this protein was uniquely responsible for the receptor specificity. Furthermore, we show by receptor immunoelectron microscopy that the FimH protein is located laterally in the structure of the type 1 fimbriae.
Research Interests: Microbiology, Electron Microscopy, Biology, Localization, Scanning Electron Microscopy, and 15 moreMedicine, Biological Sciences, Infection and immunity, Escherichia coli, Bacteria, Proteins, Plasmids, Molecular cloning, Molecular weight, Recombinant Proteins, Mannose, Bacterial Adhesion, Fimbria, Adhesin, and Medical and Health Sciences
The growth physiology of Escherichia coli during colonization of the intestinal tract was studied with four animal models: the streptomycin-treated mouse carrying a reduced microflora, the monoassociated mouse with no other microflora... more
The growth physiology of Escherichia coli during colonization of the intestinal tract was studied with four animal models: the streptomycin-treated mouse carrying a reduced microflora, the monoassociated mouse with no other microflora than the introduced strain, the conventionalized streptomycin-treated mouse, and the conventionalized monoassociated mouse harboring a full microflora. A 23S rRNA fluorescent oligonucleotide probe was used for hybridization to whole E. coli cells fixed directly after being taken from the animals, and the respective growth rates of E. coli BJ4 in the four animal models were estimated by correlating the cellular concentrations of ribosomes with the growth rate of the strain. The growth rates thus estimated from the ribosomal content of E. coli BJ4 in vivo did not differ in the streptomycin-treated and the monoassociated mice. After conventionalization there was a slight decrease of the bacterial growth rates in both animal models.
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Fluorescent oligonucleotide probes targeting rRNA were used to develop an in situ hybridization technique by which the spatial distribution of Escherichia coli in the large intestines of streptomycin-treated mice was determined. Single E.... more
Fluorescent oligonucleotide probes targeting rRNA were used to develop an in situ hybridization technique by which the spatial distribution of Escherichia coli in the large intestines of streptomycin-treated mice was determined. Single E. coli cells were identified in thin frozen sections from the large intestines by the use of a probe specific for E. coli 23S rRNA. Furthermore, the total bacterial population was visualized with an rRNA probe targeting the domain Bacteria. By this technique, all E. coli cells were seen embedded in the mucosal material overlying the epithelial cells of the large intestine, and no direct attachment to the epithelium was observed.
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The role of the Klebsiella pneumoniae capsular polysaccharide (K antigen) during colonization of the mouse large intestine was assessed with wild-type K. pneumoniae LM21 and its isogenic capsule-defective mutant. When bacterial strains... more
The role of the Klebsiella pneumoniae capsular polysaccharide (K antigen) during colonization of the mouse large intestine was assessed with wild-type K. pneumoniae LM21 and its isogenic capsule-defective mutant. When bacterial strains were fed alone to mice, the capsulated bacteria persisted in the intestinal tract at levels of 10 8 CFU/g of feces while the capsule-defective strain colonized at low levels, 10 4 CFU/g of feces. In mixed-infection experiments, the mutant was rapidly outcompeted by the wild type. In situ hybridization on colonic sections revealed that bacterial cells of both strains were evenly distributed in the mucus layer at day 1 after infection, while at day 20 the wild type remained dispersed and the capsule-defective strain was seen in clusters in the mucus layer. These results suggest that capsular polysaccharide plays an important role in the gut colonization ability of K. pneumoniae .
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Objective: Wound healing can be delayed by the presence of colonising bacteria, and in polymicrobial wounds they may act synergistically to the further detriment of wound healing. In this pilot investigation, biopsy and swab samples were... more
Objective: Wound healing can be delayed by the presence of colonising bacteria, and in polymicrobial wounds they may act synergistically to the further detriment of wound healing. In this pilot investigation, biopsy and swab samples were obtained as part of skin-graft operations performed on a chronic venous leg ulcer in order to study the spatial microbial diversity and to compare standard bacteriological and molecular biological techniques. Method: The wound was sampled before excision, and sampling was undertaken at multiple locations across the wound. Swab samples and biopsies were subjected to culture analysis and 16S rRNA polymerase chain reaction (PCR), and to denaturing gradient gel electrophoresis (DGGE). Results: Within the wound samples, DGGE identified the major wound microflora components and established the extent of local differences in bacterial diversity. Conclusion: This ongoing investigation has verified DGGE as a powerful tool for elucidating the clinical microbi...
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Query (Q) fever was virtually unknown in Denmark in 2005, when, after the introduction of new sensitive diagnostic methods for Coxiella burnetii, an increasing number of positive cattle created concern among people with frequent exposure.... more
Query (Q) fever was virtually unknown in Denmark in 2005, when, after the introduction of new sensitive diagnostic methods for Coxiella burnetii, an increasing number of positive cattle created concern among people with frequent exposure. This led to a dramatic rise in examinations for Q fever among humans in the following 2 years. The aim of our study was to assess indication for testing and symptoms in individuals with serological signs of infection with C. burnetii. We performed a case-review study of seropositives among all humans tested for Q fever in 2006-07 in Denmark. Seropositive cases were categorized with acute infection: 4-fold increase in immunoglobulin G (IgG) phase II or concomitant IgM phase II ≥ 1 : 256 and IgG phase II ≥ 1 : 1024; and previous infection: IgG phase II ≥ 1 : 1024. A borderline result was defined as: IgG phase II = 1 : 512. Physicians completed a questionnaire retrospectively. Of the 1613 people tested, 177 (11%) were seropositive [37 (2%) acute infection, 140 (9%) previous infection], 180 had a borderline result. Among 127 seropositives responders, 31% were tested due to symptoms compatible with Q fever after a possible exposure to C. burnetii, 64% were asymptomatic and were tested following relevant exposure only; 64% were males, 43% farmers, 39% veterinarians, 84% had been exposed to cattle. The most frequently reported symptoms were asthenia (25%), myalgia (21%), fever (17%) and headache (13%). About two-thirds of seropositives reported asymptomatic infections, and were tested for Q fever because of concern for occupational exposure to cattle. One-third of the seropositives reported symptoms consistent with Q fever, the majority being mild. Our study provided important evidence that increased requests for Q fever testing in 2006-07 arose from heightened public awareness of the disease, and not from an outbreak of clinical disease. Nonetheless, Q fever should be considered endemic in Denmark.
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... Permissions & Reprints. [2] Monitoring bacterial growth activity in biofilms from laboratory flow chambers, plant rhizosphere, and animal intestine. Cayo Ramos, Tine R. Licht, Claus Sternberg, Karen A. Krogfelt and... more
... Permissions & Reprints. [2] Monitoring bacterial growth activity in biofilms from laboratory flow chambers, plant rhizosphere, and animal intestine. Cayo Ramos, Tine R. Licht, Claus Sternberg, Karen A. Krogfelt and Søren Molin. Available online 29 July 2004. Excerpt. ...
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Bismuth-containing drugs are widely used in the treatment of Helicobacter pylori associated peptic ulcer. The mechanism of action of bismuth salts is, however, not fully understood, and at present no histochemical techniques for the... more
Bismuth-containing drugs are widely used in the treatment of Helicobacter pylori associated peptic ulcer. The mechanism of action of bismuth salts is, however, not fully understood, and at present no histochemical techniques for the demonstration of bismuth in H. pylori are available. The aims were to present a histochemical method for the detection of bismuth in H. pylori and to demonstrate bismuth uptake in H. pylori after in vitro exposure to bismuth citrate. H. pylori cultures (the strain used in this study was CCUG 17874), were exposed to bismuth citrate at different concentrations (0, 4.6, 80, 200 microM) and for different lengths of time (0 min, 15 min, 1 h, 24 h, 48 h). The samples were fixed in glutaraldehyde, centrifuged, and exposed to autometallographic (AMG) development in order to detect bismuth histochemically. A detailed protocol on the AMG bismuth technique on H. pylori exposed to bismuth in vitro is given. This method results in easily detectable AMG grains of silver enhanced bismuth particles at the electron microscopical level, and shows that bismuth accumulates in H. pylori, predominantly near the wall of the bacteria. Bismuth uptake is followed by bacterial degeneration. The present technique with its ability to trace bismuth constitutes a valuable tool in the efforts of clarifying the mechanism of action of bismuth on H. pylori, and supports the notion that bismuth has an antimicrobial activity in itself.
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Research Interests: Medical Microbiology, Medicine, Biological Sciences, Serology, Humans, and 14 moreSalmonella enteritidis, Animals, Salmonella Typhimurium, Typhoid Fever, Salmonella, Immunoassay, Sensitivity and Specificity, Enzyme Linked Immunosorbent Assay, Biochemistry and cell biology, Medical, Serotype, Salmonella enterica, Medical and Health Sciences, and Salmonella Typhi
Campylobacter jejuniis the most frequent cause of severe gastroenteritis in the developed world. The major symptom of campylobacteriosis is inflammatory diarrhoea. The molecular mechanisms of this infection are poorly understood compared... more
Campylobacter jejuniis the most frequent cause of severe gastroenteritis in the developed world. The major symptom of campylobacteriosis is inflammatory diarrhoea. The molecular mechanisms of this infection are poorly understood compared to those of less frequent disease-causing pathogens. In a previous study, we identifiedC. jejuniproteins that antibodies in human campylobacteriosis patients reacted with. One of the immunogenic proteins identified (Cj0917) displays homology to carbon starvation protein A (CstA) fromEscherichia coli, where this protein is involved in the starvation response and peptide uptake. In contrast to many bacteria,C. jejunirelies on amino acids and organic acids for energy, butin vivoit is highly likely that peptides are also utilized, although their mechanisms of uptake are unknown. In this study, Biolog phenotype microarrays have been used to show that aΔcstAmutant has a reduced ability to utilize a number of di- and tri-peptides as nitrogen sources. This ...
Research Interests: Microbiology, Carbon, Medical Microbiology, Biology, Medicine, and 15 moreDendritic Cells, Biological Sciences, Humans, Mice, Female, Animals, Bacteria, Complementation, Host Pathogen Interactions, Amino Acid Sequence, Campylobacter jejuni, Interleukin, Agglutination, Molecular Sequence Data, and Medical and Health Sciences
The analysis of Serratia liquefaciens MG1 ′ luxAB insertion mutants that are responsive to N -butanoyl- l -homoserine lactone revealed that expression of lipB is controlled by the swr quorum-sensing system. LipB is part of the Lip... more
The analysis of Serratia liquefaciens MG1 ′ luxAB insertion mutants that are responsive to N -butanoyl- l -homoserine lactone revealed that expression of lipB is controlled by the swr quorum-sensing system. LipB is part of the Lip exporter, a type I secretion system, which is responsible for the secretion of extracellular lipase, metalloprotease, and S-layer protein.
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Research Interests: Microbiology, Electron Microscopy, Medical Microbiology, Biology, Transmission Electron Microscopy, and 13 moreMedicine, Humans, Escherichia coli, Mice, Animals, Bacteria, Antimicrobial chemotherapy, Antibiotics, Mouse Model, Urinary Bladder, Intracellular, Antibiotic treatment, and Pharmacology and pharmaceutical sciences
Analysis of the hydrophilic fraction of cranberry juice by reversed-phase HPLC using an Aqua LUNA column with diode array or MS detection revealed the presence of quinic acid, malic acid, shikimic acid, and citric acid. For the first... more
Analysis of the hydrophilic fraction of cranberry juice by reversed-phase HPLC using an Aqua LUNA column with diode array or MS detection revealed the presence of quinic acid, malic acid, shikimic acid, and citric acid. For the first time, two iridoid glucosides were found in the juice. The two iridoid glucosides were shown to be monotropein and 6,7-dihydromonotropein by MS and NMR spectroscopy. A fast reversed-phase HPLC method for quantification of the hydrophilic carboxylic acids was developed and used for analyses of cranberry, lingonberry, and blueberry juices. The level of hydrophilic carboxylic acids in cranberries was 2.67-3.57% (w/v), in lingonberries 2.27-3.05%, and in blueberries 0.35-0.75%. In lingonberries both iridoid glucosides were present, whereas only monotropein was present in blueberries.
Research Interests: Engineering, Chemistry, Mass Spectrometry, Magnetic Resonance Spectroscopy, Medicine, and 13 moreAgricultural, High Pressure Liquid Chromatography, CHEMICAL SCIENCES, Beverages, Iridoids, Vaccinium myrtillus, Carboxylic Acids, Agricultural and Food Chemistry, Vaccinium Macrocarpon, Citric Acid, Quinic Acid, Shikimic acid, and Cranberry juice
The ability of Escherichia coli to survive stress during growth in different environments is, in large part, dependent on rpoS and the genes that comprise the rpoS regulon. E. coli BJ4 and an isogenic BJ4 rpoS mutant were used to examine... more
The ability of Escherichia coli to survive stress during growth in different environments is, in large part, dependent on rpoS and the genes that comprise the rpoS regulon. E. coli BJ4 and an isogenic BJ4 rpoS mutant were used to examine the influence of the rpoS gene on E. coli colonization of the streptomycin-treated mouse large intestine. Colonization experiments in which the wild-type E. coli BJ4 and its rpoS mutant were fed individually as well as simultaneously to mice suggested that E. coli BJ4 does not face prolonged periods of nutrient starvation in the mouse large intestine and that the rpoS regulon is not expressed during long-term colonization after adaptation of the bacteria to the gut environment.
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A minitransposon mutant of Salmonella enterica serovar Typhimurium SR-11, SR-11 Fad − , is unable to utilize gluconeogenic substrates as carbon sources and is avirulent and immunogenic when administered perorally to BALB/c mice (M. J.... more
A minitransposon mutant of Salmonella enterica serovar Typhimurium SR-11, SR-11 Fad − , is unable to utilize gluconeogenic substrates as carbon sources and is avirulent and immunogenic when administered perorally to BALB/c mice (M. J. Utley et al., FEMS Microbiol. Lett., 163:129–134, 1998). Here, evidence is presented that the mutation in SR-11 Fad − that renders the strain avirulent is in the cra gene, which encodes the Cra protein, a regulator of central carbon metabolism.
Research Interests: Microbiology, Biology, Medicine, Biological Sciences, Infection and immunity, and 15 moreVirulence, Mice, Animals, Salmonella Typhimurium, Infection, Enterobacteriaceae, Gene, Salmonella, Intestines, Carbohydrate metabolism, Mucus, Serotyping, Serotype, Salmonella enterica, and Medical and Health Sciences
SUMMARYAn increase in pertussis has been observed in several countries over the last decades, especially in adult populations. The seroprevalence of pertussis was determined in a cross-sectional study of the adult population in the... more
SUMMARYAn increase in pertussis has been observed in several countries over the last decades, especially in adult populations. The seroprevalence of pertussis was determined in a cross-sectional study of the adult population in the Copenhagen area, Denmark, conducted between 2006 and 2008. Specific IgG antibodies against pertussis toxin (PT) were measured in 3440 persons resulting in an age-standardized seroprevalence of 3·0% (95% confidence interval 1·9–4·7) using an IgG anti-PT cut-off of 75 IU/ml. By using antibody decay profiles from longitudinal data the estimated seroincidence was 143/1000 person-years. In contrast, an incidence of 0·03/1000 person-years was estimated from the official data of notified cases during the same period. Of the investigated risk factors, only age and education were significantly associated with pertussis infection. This study indicates that pertussis is highly underestimated in the adult population in Denmark, which has implications for future preve...
Research Interests: Epidemiology, Incidence Geometry, Adolescent, Medicine, Denmark, and 15 morePopulation, Humans, Female, Male, Incidence, Aged, Middle Aged, Adult, Public health systems and services research, Risk Factors, Cross sectional Study, Cross Sectional Studies, Confidence Interval, Bordetella Pertussis, and immunoglobulin G
SUMMARYAlthough most foodborne infections are undiagnosed, the incidence of these infections is usually calculated from reported cases. We present a novel population-based method to estimate the incidence of non-typhoid Salmonella... more
SUMMARYAlthough most foodborne infections are undiagnosed, the incidence of these infections is usually calculated from reported cases. We present a novel population-based method to estimate the incidence of non-typhoid Salmonella infections. From 154 patients with confirmed Salmonella serotype Enteritidis infection, we determined the kinetics of the antibody response. The estimated mean responses for the three classes of serum antibodies were combined such that the time from infection could be estimated from antibody measurements. Next, serum samples collected in 1983, 1986, 1992, and 1999 from the general population were analysed for antibodies. We demonstrated how these measurements can be translated into an estimate of the general incidence. Based on serology markers there were 13 exposures leading to seroresponse of Salmonella Enteritidis/1000 person-years in 1983; the similar number in 1999 was 217. This trend confirms the increase in the number of culture-confirmed cases repo...