ABSTRACT
Neonatal myocardial infarction due to coronary thrombus is a rare cause of acute heart failure and is associated with high morbidity and mortality. We present a rare case of a full-term newborn who developed coronary artery thrombus treated with intracoronary recombinant tissue plasminogen activator infusion while undergoing therapeutic hypothermia. Also, we describe a unique treatment strategy to support systemic circulation sparing the patient from neonatal extracorporeal membrane oxygenation and its complications. Neonatal myocardial infarction should be suspected and ruled out in sick newborns.
Subject(s)
Extracorporeal Membrane Oxygenation , Myocardial Infarction , Thrombosis , Extracorporeal Membrane Oxygenation/adverse effects , Female , Heart Ventricles/diagnostic imaging , Humans , Infant, Newborn , Myocardial Infarction/drug therapy , Pregnancy , Thrombosis/complications , Thrombosis/etiology , Tissue Plasminogen Activator/therapeutic useABSTRACT
In Flanders, Belgium, rigid and soft plastics represent an interesting fraction of residual household waste as a potential 80 000â¯Ggâ¯a-1 can be recycled instead of incinerated. Removing a large amount of rigid packaging and non-packaging plastics from the residual household waste fraction could contribute to the goal to reduce the amount of residual household waste to less than 150â¯kg capita-1â¯a-1 for the Flemish region, where currently only 20% of plastics are collected selectively in drop-off facilities. Given the wide range of plastic separation schemes across the region, it is the aim of this paper to identify whether the applied separation options have an impact on the quantity of separated plastics, and, moreover, which scheme is able to separate most plastics. Cross-sectional data for the period 2008-2012 were collected for all 308 Flemish municipalities to conduct a regression analysis. The results of the analysis show that the quantity of separated plastics differs significantly between the different separation schemes used. If municipalities change their separation schemes, Flanders as a whole would be able to collect more plastic waste to better comply with its own objectives and EU regulation on recycling. Improved separation-at-source recycling initiatives, by applying the appropriate separation scheme for plastics, may increase recycling growth.
Subject(s)
Agriculture/economics , Fertilizers/analysis , Fertilizers/economics , Adult , Animals , Belgium , Crops, Agricultural , Data Collection , Humans , Livestock , Middle Aged , Surveys and Questionnaires , Young AdultABSTRACT
Recently, biogas plant managers in Flanders face increased financial uncertainty. Between 2011 and 2012, 20% of the Flemish biogas plants went bankrupt. Difficulties in obtaining feedstock at stable and affordable prices is one reason why the biogas sector struggles. In literature, contracting is often proposed as a way to decrease the volatility of the feedstock costs. However, these studies generally do not consider the context in which the biogas plant manager needs to buy the feedstock. Yet, this context could be of specific importance when biogas plant managers are in competition with other users of the same biomass type. Silage maize is an example of such a feedstock, as it is both used by dairy farmers and biogas plant managers. Using a combination of qualitative research and agent-based modelling, we investigated the effect of specific characteristics of the silage maize market on the acquisition of local silage maize by biogas plant managers. This paper details the institutional arrangements of the silage maize market in Flanders and the results of a scenario analysis, simulating three different scenarios. As shown by the results, the time of entry into the market, as well as the different institutional arrangements used by the biogas plant managers as opposed to dairy farmers could explain the difficulties in obtaining a stable supply of local silage maize by biogas plants. Our findings can help to develop mitigation strategies addressing these difficulties.
Subject(s)
Biofuels/economics , Bioreactors , Models, Theoretical , Silage/economics , Zea mays , BelgiumABSTRACT
The rising pressure in terms of cost efficiency on public services pushes governments to transfer part of those services to the private sector. A trend towards more privatizing can be noticed in the collection of municipal household waste. This paper reports the findings of a research project aiming to compare the cost between the service of private and public collection of residual household waste. Multiple case studies of municipalities about the Flemish region of Belgium were conducted. Data concerning the year 2009 were gathered through in-depth interviews in 2010. In total 12 municipalities were investigated, divided into three mutual comparable pairs with a weekly and three mutual comparable pairs with a fortnightly residual waste collection. The results give a rough indication that in all cases the cost of private service is lower than public service in the collection of household waste. Albeit that there is an interest in establishing whether there are differences in the costs and service levels between public and private waste collection services, there are clear difficulties in establishing comparisons that can be made without having to rely on a large number of assumptions and corrections. However, given the cost difference, it remains the responsibility of the municipalities to decide upon the service they offer their citizens, regardless the cost efficiency: public or private.
Subject(s)
Private Sector , Public Sector , Waste Management/economics , Belgium , Cluster Analysis , GarbageABSTRACT
AIM: The aim of this study is to investigate the effects of food insecurity derived from non-cereal food consumption on nutritional status of children and mothers in a poverty-prone region in Bangladesh. METHODS: Data from the Bangladesh Nutritional Surveillance Project, 2005 of Helen Keller International were used to relate non-cereal food consumption and household food insecurity to nutritional status of children and their mothers. Multiple regressions were used to determine the association between the nutritional outcomes and the explanatory variables. In the case of binary and multi-level outcomes, logistic regressions were used as well. RESULTS: Non-cereal dietary diversity was found to have little predictive power on BMI and MUAC of mothers and on the nutritional status of the children. Maternal education is strongly associated with mothers' and children's nutritional status. CONCLUSION: Dietary diversity based on non-cereal food consumption can be a useful tool to investigate the nutritional status of poor households, but more studies are needed to verify these findings.
Subject(s)
Diet/psychology , Eating/psychology , Food Supply , Mothers , Nutritional Status , Bangladesh , Body Mass Index , Child, Preschool , Female , Food , Humans , Infant , Infant, Newborn , Male , Poverty , Surveys and QuestionnairesABSTRACT
Aim: The aim of this study is to investigate the effects of food insecurity derived from non-cereal food consumption on nutritional status of children and mothers in a poverty-prone region in Bangladesh. Methods: Data from the Bangladesh Nutritional Surveillance Project, 2005 of Helen Keller International were used to relate non-cereal food consumption and household food insecurity to nutritional status of children and their mothers. Multiple regressions were used to determine the association between the nutritional outcomes and the explanatory variables. In the case of binary and multi-level outcomes, logistic regressions were used as well. Results: Non-cereal dietary diversity was found to have little predictive power on BMI and MUAC of mothers and on the nutritional status of the children. Maternal education is strongly associated with mothers’ and children’s nutritional status. Conclusion: Dietary diversity based on non-cereal food consumption can be a useful tool to investigate the nutritional status of poor households, but more studies are needed to verify these findings.
ABSTRACT
BACKGROUND AND PURPOSE: Previous results have shown that mice lacking in the group 1B phospholipase A(2) (Pla2g1b) are resistant to obesity and diabetes induced by feeding a diabetogenic high-fat/high-carbohydrate diet. This study examined the potential of using the Pla2g1b inhibitor methyl indoxam as therapy to suppress diet-induced obesity and diabetes. EXPERIMENTAL APPROACH: Male C57BL/6 mice were fed the diabetogenic diet with or without methyl indoxam supplementation. Body weight gain, fasting plasma glucose levels, glucose tolerance and postprandial lysophospholipid absorption were compared. KEY RESULTS: Wild-type C57BL/6 mice fed the diabetogenic diet without Pla2g1b inhibitor showed 31 and 69% body weight gain after 4 and 10 weeks respectively. These animals also showed elevated plasma glucose levels and were glucose intolerant. In contrast, C57BL/6 mice fed the diabetogenic diet with 90 mg.kg(-1) of methyl indoxam gained only 5% body weight after 10 weeks. These animals were also euglycaemic and displayed normal glucose excursion rates in glucose tolerance test. Methyl indoxam suppression of diet-induced body weight gain and glucose intolerance was correlated with the inhibition of Pla2g1b-mediated postprandial lysophospholipid absorption. CONCLUSIONS AND IMPLICATIONS: These results show that oral supplementation of a diabetogenic diet with the Pla2g1b inhibitor methyl indoxam effectively suppresses diet-induced obesity and diabetes in mice. This suggests that Pla2g1b inhibition may be a potentially effective oral therapeutic option for treatment of obesity and diabetes.
Subject(s)
Anti-Obesity Agents/therapeutic use , Biphenyl Compounds/pharmacology , Glucose Intolerance/drug therapy , Group IB Phospholipases A2/antagonists & inhibitors , Hypoglycemic Agents/therapeutic use , Indoles/pharmacology , Obesity/drug therapy , Animals , Anti-Obesity Agents/pharmacokinetics , Bile/drug effects , Bile/enzymology , Caco-2 Cells , Dietary Carbohydrates/administration & dosage , Dietary Fats/administration & dosage , Eating/drug effects , Glucose Intolerance/blood , Glucose Intolerance/etiology , Group IB Phospholipases A2/genetics , Group IB Phospholipases A2/metabolism , Humans , Hydrolysis , Hypoglycemic Agents/pharmacokinetics , Lysophospholipids/blood , Male , Mice , Mice, Inbred C57BL , Mice, Knockout , Obesity/blood , Obesity/etiology , Postprandial Period , Recombinant Proteins/antagonists & inhibitors , Recombinant Proteins/metabolism , Weight Gain/drug effectsABSTRACT
The radon absorption ability and the track etch properties of the polycarbonate material of commercial compact disks make them very useful as sensitive retrospective 222Rn detectors. The basic idea is to remove, after exposure, a surface layer that is thicker than the range of the alpha particles of the 222Rn and 220Rn progenies and to count the electrochemically etched tracks at the corresponding depths (>80 microm). The effects on the response due to differences in pressure, temperature, and humidity have been studied experimentally. The effect of the growing of 210Po after long-term exposures was also estimated. The effect of all listed factors except the temperature is either absent or restricted to maximum--about 10% for the very extreme cases. The variation of the response at 83 microm depth over the temperature interval 15-25 degrees C is +/-12% around the 20 degrees C value. The dependence of the calibration factor on the etched depth beneath the surface was studied at 4 different temperatures within the range expected indoors. The results show that the depth dependence is exponential with the parameters of the exponent also being dependent on the temperature. In practice, using the track density obtained in two or more depths beneath the compact disk's front surface, an a posteriori temperature correction could be made. By this correction it is possible to substantially reduce the bias in the results due to the unknown temperature during exposure. The results imply that by using home stored compact disks long-term retrospective 222Rn measurements could be made with an uncertainty that could be potentially better than 10%. The useful range of the method starts at about 3 Bq m(-3) (for 10 y exposure time) and appears to cover practically the whole range of indoors 222Rn concentrations.
Subject(s)
Compact Disks , Materials Testing/methods , Radiometry/instrumentation , Radon/analysis , Alpha Particles , Background Radiation , Calibration , Environmental Monitoring/instrumentation , Environmental Monitoring/methods , Equipment Design , Humidity , Polycarboxylate Cement/chemistry , Polycarboxylate Cement/radiation effects , Pressure , Radiometry/methods , Radon/chemistry , Radon Daughters/analysis , Radon Daughters/chemistry , Sensitivity and Specificity , Statistics as Topic , TemperatureABSTRACT
The yycF1(Ts) mutation in Staphylococcus aureus conferred hypersensitivity to macrolide-lincosamide-streptogramin B (MLS(B)) antibiotics on strains either containing or lacking ermB. The overexpression of the S. aureus Ssa protein restored the yycF1 mutant to wild-type levels of susceptibility. Inactivation of ssa in an unmutagenized strain dramatically reduced ermB-based resistance. Conditional loss of function or expression of ssa in the yycF1 mutant is proposed to result in the observed hypersensitivity to MLS(B) antibiotics.
Subject(s)
Anti-Bacterial Agents/pharmacology , Bacterial Proteins/genetics , Drug Resistance, Multiple, Bacterial , Macrolides , Staphylococcus aureus/drug effects , Streptogramins/pharmacology , Amino Acid Sequence , Bacterial Proteins/metabolism , Lincosamides , Methyltransferases/genetics , Methyltransferases/metabolism , Microbial Sensitivity Tests , Molecular Sequence Data , Mutation , Staphylococcus aureus/genetics , TemperatureABSTRACT
Complete DNA sequence information has now been obtained for several prokaryotic genomes, defining the entire genetic complement of these organisms. The collection of genomic data has provided new insights into the molecular architecture of bacterial cells, revealing the basic genetic and metabolic structures that support viability of the organisms. Genomic information has also revealed new avenues for inhibition of bacterial growth and viability, expanding the number of possible drug targets for antibiotic discovery. This review examines how genomic sciences and experimental tools are applied to antibacterial target discovery, the necessary first step in the development of new antibiotic classes. Significant advances have been realized in the development of functional genomic, comparative genomic, and proteomic methods for the analysis of completed genomes. The combination of these methods can be used to systematically parse the genome and identify targets worthy of inhibitor screens. Two basic categories of targets emerge from this exercise, comprising in vitro essential targets required for bacterial viability on synthetic media and in vivo essential targets required to establish and maintain infection within a host organism. Current use of genomic information is focused primarily on a definition of all in vitro essential targets that satisfy criteria of selectivity, spectrum, and novelty. As the genomes of additional bacterial pathogens are solved, it will be possible to select in vivo essential targets common to groups of select pathogens (e.g., bacterial agents of community acquired pneumonia) or even pathogen-specific targets. Consideration of host-pathogen interactions, defined at the level of gene expression for each organism, might provide novel therapeutic options in the future.
Subject(s)
Anti-Infective Agents/pharmacology , Drug Design , Drug Industry/methods , Genomics/methods , Animals , Anti-Infective Agents/chemistry , Genes, Bacterial , Genome, Bacterial , Genomics/trendsABSTRACT
An approach for preparation of short-lived alpha sources of energy 6.0 MeV and 7.69 MeV is proposed. The sources are prepared by taking a sample of 222Rn progeny on an alpha spectrometric filter. The activities (or related parameters) of 218Po, 214Pb and 214Bi at the end of sampling are precisely determined by a reference measurement with an alpha spectrometer. Further they are used as input values to calculate with a sufficient precision the number of emitted alpha particles of any energy and at any time interval of interest. Theoretical modelling and experimental results demonstrated that such sources could be prepared with a sufficient purity. There is a potential for the number of alpha particles emitted in a given time interval to be certified with an accuracy of 1-2%.
Subject(s)
Nuclear Energy , Radiation Monitoring/methods , Radon/analysis , Calibration , Elements, Radioactive/analysis , Models, Theoretical , Radon/adverse effects , Sensitivity and Specificity , Spectrometry, GammaABSTRACT
The residual radiocesium concentration, nearly 10 y after the Chernobyl accident, is measured at different sites on the Belgian territory by means of in-situ gamma-spectrometry. A possible link between the rainfall at the beginning of May 1986 and the actual cesium concentration is investigated. The radiological impact of this contamination, even in the most affected regions in the Ardennes, is very small (<6 microSv y(-1)).
Subject(s)
Cesium Radioisotopes/analysis , Radioactive Fallout , Radioactive Hazard Release , Soil Pollutants, Radioactive/analysis , Belgium , Geography , Rain , Seasons , Spectrometry, Gamma/methods , Time Factors , UkraineABSTRACT
The oxazolidinones are a new class of synthetic antibiotics with good activity against gram-positive pathogenic bacteria. Experiments with a susceptible Escherichia coli strain, UC6782, demonstrated that in vivo protein synthesis was inhibited by both eperezolid (formerly U-100592) and linezolid (formerly U-100766). Both linezolid and eperezolid were potent inhibitors of cell-free transcription-translation in E. coli, exhibiting 50% inhibitory concentrations (IC50s) of 1.8 and 2.5 microM, respectively. The ability to demonstrate inhibition of in vitro translation directed by phage MS2 RNA was greatly dependent upon the amount of RNA added to the assay. For eperezolid, 128 microg of RNA per ml produced an IC50 of 50 microM whereas a concentration of 32 microg/ml yielded an IC50 of 20 microM. Investigating lower RNA template concentrations in linezolid inhibition experiments revealed that 32 and 8 microg of MS2 phage RNA per ml produced IC50s of 24 and 15 microM, respectively. This phenomenon was shared by the translation initiation inhibitor kasugamycin but not by streptomycin. Neither oxazolidinone inhibited the formation of N-formylmethionyl-tRNA, elongation, or termination reactions of bacterial translation. The oxazolidinones appear to inhibit bacterial translation at the initiation phase of protein synthesis.
Subject(s)
Acetamides/pharmacology , Anti-Infective Agents/pharmacology , Oxazoles/pharmacology , Oxazolidinones , Protein Biosynthesis/drug effects , Anti-Bacterial Agents , Bacterial Proteins/biosynthesis , Coliphages , Culture Media , Escherichia coli/drug effects , Escherichia coli/genetics , Linezolid , Microbial Sensitivity Tests , N-Formylmethionine/metabolism , Poly U/metabolism , Polyribosomes/drug effects , Polyribosomes/metabolism , Ribosomes/drug effects , Ribosomes/metabolism , Transcription, Genetic/drug effectsABSTRACT
Shigella species and enteroinvasive Escherichia coli contain a core set of virulence genes whose coordinated expression results in the invasion of host colonic epithelial cells and the dysenteric syndrome. A number of virulence determinants are carried by the 230 kb invasion plasmid found in all virulent strains of Shigellae. Many of these invasion plasmid genes encode immunogens that are recognized by convalescent serum, including proteins that mediate the invasion (IpaB, IpaC, IpaD) and cell spreading (VirG or IcsA and IcsB) phenotypes. In this report, we describe the molecular characterization of a novel invasion plasmid antigen from Shigella flexneri, designated IpaJ. The ipaJ gene encodes a 780 bp open reading frame (ORF), separated from the ipaR (virB) stop codon by 944 bp. The predicted amino acid sequence for IpaJ revealed a consensus signal peptide for protein export. TnphoA mutagenesis of the ipaJ ORF confirmed the presence of export signal sequences in IpaJ. Unlike ipaBCDA genes, transcription analysis of ipaJ indicated that the gene is not expressed in a temperature-dependent fashion. The IpaJ protein was expressed and purified as a His6-tagged fusion protein that reacted with convalescent sera in Western blot analyses, confirming its identification as a Shigella immunogen. Construction and phenotypic characterization of ipaJ mutants in two serotypes of S. flexneri showed that the mutants were not compromised in their ability to invade cultured epithelial cells or to form plaques on BHK cell monolayers. In addition, the ipaJ mutants were Sereny positive indicating a capacity for intercellular dissemination; however, in the limited number of guinea-pigs tested, the keratoconjunctivitis reaction appeared attenuated.
Subject(s)
Antigens, Bacterial/genetics , Shigella flexneri/genetics , Amino Acid Sequence , Animals , Antigens, Bacterial/metabolism , Base Sequence , Blotting, Western , Cells, Cultured , Gene Expression Regulation , Guinea Pigs , HeLa Cells , Humans , Molecular Sequence Data , Mutagenesis , Plasmids , RNA, Bacterial/analysis , RNA, Messenger/analysis , Recombinant Fusion Proteins/analysis , Restriction Mapping , Sequence Analysis , Shigella flexneri/pathogenicity , VirulenceABSTRACT
We describe methods for the mutagenesis of cloned Actinobacillus pleuropneumoniae (Ap) genes and for the construction of Ap mutants by allelic exchange. We used these methods to construct isogenic mutants of Ap which no longer synthesized a 48-kDa outer membrane protein (AopA). The native aopA locus was replaced with a mutated locus that had been inactivated by insertion of a gene (KmR) encoding kanamycin resistance from Tn903. The inactivated aopA locus was cloned into a conjugative, R6K-derived, lambda pir-dependent suicide vector and introduced into Ap using a filtermating technique. Southern and Western blot analyses indicated that the wild-type locus was replaced by the mutated locus through either single- or double-crossover events, and that AopA was no longer produced by either type of mutant. These methods were used successfully to construct AopA- mutants in Ap serotypes 1 and 5. These methods should be generally useful in constructing mutant loci which can be used to analyze the roles of various Ap genes in the pathogenesis of contagious pleuropneumonia in swine.
Subject(s)
Actinobacillus pleuropneumoniae/genetics , Bacterial Outer Membrane Proteins/genetics , Mutagenesis , Actinobacillus pleuropneumoniae/metabolism , AllelesABSTRACT
The ipaH loci comprise a multicopy antigen gene family unique to Shigella species and enteroinvasive Escherichia coli (EIEC). DNA probes derived from the Shigella flexneri serotype 5 ipaH7.8 gene were used to compare the molecular arrangement of ipaH alleles in a variety of Shigella and EIEC strains. Multiple copies of ipaH-homologous sequences were detected in all invasion plasmids examined. Oligonucleotide probes covering discrete 24 bp segments of the ipaH7.8 gene and sequences flanking the ipaH4.5 (probe H25) and ipaH2.5 (probe H24) loci were used to define the extent of homology among invasion plasmid copies of ipaH in S. flexneri serotypes 1, 2 and 5 and in S. sonnei. IpaH alleles carried by these invasion plasmids were not structurally equivalent and showed sequence divergence at their amino- and carboxy-terminal ends. The H25 probe was shown to correspond to an IS629 sequence genetically linked to the ipaH alleles, while the H24 probe defined a DNA sequence found only in Shigella invasion plasmids. Chromosomal DNA from invasion plasmid-cured S. flexneri and S. sonnei strains hybridized a core ipaH7.8 gene segment, indicating that portions of the ipaH7.8 structural gene were reiterated and contained within the shigellae chromosomes. Based on the specificity of the ipaH7.8 core probe and the detection of ipaH sequences on the invasion plasmids and chromosomes of Shigella strains, three polymorphic groups within a collection of forty S. dysenteriae 1 isolates received by the United States Centers for Disease Control in 1988 were identified using this probe. These results suggest that ipaH restriction fragment length polymorphisms may be useful in genetic lineage and epidemiologic studies of virulent shigellae.
Subject(s)
Antigens, Bacterial , Bacterial Proteins/genetics , Escherichia coli/genetics , Genes, Bacterial , Shigella/genetics , Base Sequence , Chromosome Mapping , DNA Probes , Genotype , Hybridization, Genetic , Molecular Sequence Data , Plasmids/chemistry , Plasmids/genetics , Polymorphism, Genetic , Polymorphism, Restriction Fragment Length , Restriction Mapping , Shigella flexneri/genetics , Shigella flexneri/immunologyABSTRACT
An avirulent, invasion plasmid insertion mutant of Shigella flexneri 5 (pHS1059) was restored to the virulence phenotype by transformation with a partial HindIII library of the wild-type invasion plasmid constructed in pBR322. Western immunoblot analysis of pHS1059 whole-cell lysates revealed that the synthesis of the invasion plasmid antigens VirG, IpaA, IpaB, IpaC, and IpaD was similar to that seen in the corresponding isogenic S. flexneri 5 virulent strain, M90T. IpaB and IpaC, however, were not present on the surface of pHS1059 as was found in M90T, suggesting that the transport or presentation of the IpaB and IpaC proteins onto the bacterial surface was defective in the mutant. pHS1059 was complemented by pWR266, which carried contiguous 1.2- and 4.1-kb HindIII fragments of the invasion plasmid. pHS1059(pWR266) cells were positive in the HeLa cell invasion assay as well as colony immunoblot and enzyme-linked immunosorbent assays, using monoclonal antibodies to IpaB and IpaC. These studies established that the antigens were expressed on the surface of the transformed bacteria. In addition, water extraction of pHS1059 and pHS1059(pWR266) whole cells, which can be used to remove IpaB and IpaC antigens from the surface of wild-type M90T bacteria, yielded significant amounts of these antigens from pHS1059(pWR266) but not from pHS1059. Minicell and DNA sequence analysis indicated that several proteins were encoded by pWR266, comprising the spa loci, which were mapped to a region approximately 18 kb upstream of the ipaBCDAR gene cluster. Subcloning and deletion analysis revealed that more than one protein was involved in complementing the Spa- phenotype in pHS1059. One of these proteins, Spa47, showed striking homology to ORF4 of the Bacillus subtilis flaA locus and the fliI gene sequence of Salmonella typhimurium, both of which bear strong resemblance to the alpha and beta subunits of bacterial, mitochondrial, and chloroplast proton-translocating F0F1 ATPases.
Subject(s)
Antigens, Bacterial/genetics , Shigella flexneri/pathogenicity , Adenosine Triphosphate/metabolism , Amino Acid Sequence , Antigens, Surface/genetics , Base Sequence , Cell Membrane/immunology , Cell Membrane/metabolism , Chromosome Mapping , Cloning, Molecular , DNA Transposable Elements , DNA, Bacterial/genetics , Genes, Bacterial , Genetic Complementation Test , Molecular Sequence Data , Plasmids , Restriction Mapping , Sequence Alignment , Shigella flexneri/genetics , Shigella flexneri/immunologyABSTRACT
Colonial variation of Shigella flexneri serotype 2a from the translucent (2457T) to the opaque form (2457O) occurs spontaneously once in 10(4) cell divisions, with concomitant loss of ipa gene expression and virulence. The appearance of 2457O was associated with the insertional inactivation of virF, an invasion plasmid-encoded positive regulator of ipa gene expression. Plasmid pWR110, a Tn5-tagged invasion plasmid that restores the invasive phenotype to plasmid-cured Shigella derivatives, was conjugally transferred into 2457O. Synthesis of the invasion-associated IpaB and IpaC polypeptides, normally present on the surface of virulent shigellae, and the invasive phenotype were restored in 2457O(pWR110) transconjugants. Plasmid DNA restriction endonuclease patterns of 2457T and 2457O, along with hybridization analysis, showed that a SalI fragment carrying the virF gene in 2457O had increased in size relative to its counterpart in 2457T. Analysis of virF DNA sequences amplified by the polymerase chain reaction revealed that the virF sequence from 2457O was 780 bp larger than that amplified from 2457T. Moreover, the virF sequence amplified from 2457O hybridized to an IS1 DNA probe whereas the amplified 2457T virF sequence did not. DNA sequence analysis mapped the insertion element, designated IS1SFO, within an A.T-rich region of the virF open reading frame and identified a 9-bp virF target sequence that was duplicated at the insertion site of IS1SFO. The DNA sequence of IS1SFO was greater than 99% homologous to IS1F. Plasmid pWR600, carrying a 1,260-bp HpaII fragment encoding a wild-type virF gene, was able to restore the virulent phenotype and translucent colonial morphology to nine independently isolated 2457O hosts.