Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.30.2 (endonuclease)
 18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We studied the restriction endonuclease cleavage patterns of rRNA genes (ribotypes) of 72 clinical isolates of Shigella flexneri representing eight serotypes to determine whether ribotyping could be used to distinguish S. flexneri strains and to compare the discriminating ability of the method with that of serotyping. By using a cloned Escherichia coli rRNA operon as the probe, Southern blot hybridization of restriction endonuclease-digested total DNA was carried out. Ribotyping of the isolates with each of the five restriction endonucleases BamHI, EcoRI, HindIII, PstI, and SalI generated reproducible restriction patterns. However, HindIII produced the optimum digestion pattern of the rRNA genes and was more useful than the other enzymes used in differentiating strains. Analysis of the 72 isolates showed 11 different HindIII cleavage patterns of their rRNA genes. Four of these HindIII-generated ribotypes could be further differentiated into two to four subribotypes by using PstI. The results indicate that ribotyping has an application for differentiation of S. flexneri strains and can complement serotyping. Definition of strains in terms of both serotype and ribotype may be of greater use in epidemiological studies.
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PMID:Differentiation of Shigella flexneri strains by rRNA gene restriction patterns. 128 Jun 47

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.
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PMID:Spontaneous insertion of an IS1-like element into the virF gene is responsible for avirulence in opaque colonial variants of Shigella flexneri 2a. 130 11

A correlation between the multiple drug resistance patterns and the plasmid profiles given by 70 clinical isolates of Shigella sonnei and Shigella flexneri was investigated in this study. The most common plasmids were purified from different isolates by electroelution and characterized via restriction endonuclease digestions.
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PMID:[Plasmid analysis of antibiotic resistant Shigella isolates]. 179 58

Plasmid isolation was used to refine the epidemiologic analysis for 168 shigellosis cases in Pima County, Ariz. Plasmids of less than 20 kb were used for comparison of plasmid profiles. Plasmid patterns for each species were distinct. A total of 57 of 74 (77%) Shigella flexneri strains could be placed into seven plasmid patterns, 70 of 79 (89%) Shigella sonnei strains could be placed into seven patterns, 12 Shigella boydii strains could be placed into six patterns, and each of 3 Shigella dysenteriae strains differed. There was a correlation between plasmid patterns and serotypes for S. flexneri, and multiple plasmid patterns were found in serotypes 1, 2, and 6, offering a refinement beyond serotyping. In previous studies we found an association between Mexican travel and an S. sonnei 5.1-kb plasmid. When this plasmid was used as a probe, strong homology was seen with numerous small plasmids in all Shigella species: restriction endonuclease analysis revealed a 1.1-kb AvaI-AvaII fragment common to various plasmids of S. sonnei. S. flexneri, and S. boydii independent of species. Of 34 Pima County Shigella isolates from the mid-1970s. 8 showed plasmid patterns similar to those of the recent isolates. Some plasmids from S. sonnei, S. flexneri, and S. boydii strains isolated in the 1970s also contained the AvaI-AvaII fragment. The conservation of this specific fragment in our population for more than 12 years suggests that it may contain genes important in virulence or survival.
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PMID:Molecular epidemiology of Shigella infections: plasmid profiles, serotype correlation, and restriction endonuclease analysis. 184 48

The Sfl2aI system of restriction-modification (RM) was revealed in the cells of Shigella flexneri encoded by pKMR114 plasmid belonging to the IncN incompatibility group. The genes for Sfl2aI RM system were cloned. The system was ascribed to the enzymes of the EcoRII specificity, as shown by in vivo and in vitro experiments. Restriction analysis of these genes' region and antigenic properties of the Sfl2aI endonuclease pointed to significant differences between this and EcoRII RM systems.
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PMID:[Cloning of Shigella flexneri 2a genes coding for restriction- modification system Sfl2aI]. 222 95

In 1983, a small outbreak of infections caused by a previously unrecognized multiply-drug-resistant Shigella flexneri 3a strain occurred on the Hopi Indian reservation. The index patient, a diabetic woman with recurrent Escherichia coli bacteriuria on prophylactic trimethoprim/sulfamethoxazole (TMP/SMZ) therapy, was hospitalized with concurrent E. coli urinary tract infection and shigellosis. Both E. coli isolated from her urine and S. flexneri isolated from her stool were resistant to ampicillin, carbenicillin, streptomycin, sulfisoxazole, tetracycline, and TMP/SMZ. Both isolates contained a 35-MDa plasmid transferrable to recipient E. coli, and transconjugates acquiring the plasmid from either donor strain also acquired resistance to the same agents. The number and size of fragments generated by plasmid digestion with DNA restriction endonuclease ClaI were similar. A review of clinical microbiology records showed that an E. coli strain isolated from the patient 3 w before the onset of shigellosis had identical antimicrobial resistance to the E. coli and Shigella isolated during the outbreak. These studies indicate that the index patient receiving prophylactic TMP/SMZ was the likely source of the R-plasmid for the outbreak strain of Shigella.
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PMID:Interspecies gene transfer in vivo producing an outbreak of multiply resistant shigellosis. 268 26

Analysis of six Shigella flexneri and four S. sonnei isolates with trimethoprim (Tp) resistance from clinical cases in Ontario has shown that, in all isolates, the Tp resistance is mediated by gene(s) on conjugative, multiple antibiotic-resistance plasmids. The physical and genetic characterization of these plasmids revealed that there are three different Tp resistance plasmids. One group, composed of all six S. flexneri plasmids, consists of plasmids which are about 70 megadaltons (MDa) and inhibit the fertility of an Escherichia coli Hfr strain (Fi+). A representative member of this group, pPT4, demonstrates a weak incompatibility reaction with IncFl plasmid R455-2. Another group, three of the four S. sonnei plasmids, contains plasmids which are about 43 MDa, Fi-, and mediate propagation of phage PRD1. The third group, the remaining S. sonnei plasmid, is 53 MDa, fi+, mediates propagation of phages fd and MS2, and is incompatible with IncFII plasmid R100. These plasmids also have been differentiated by restriction endonuclease fragment profiles. Analysis of pPT4 has revealed that the Tp resistance of this plasmid is transposable. The transposon, Tn536, is different from previously described Tp resistance transposons; it is 16 MDa, and in addition to Tp, it encodes resistance to mercuric chloride ions, spectinomycin, streptomycin, and sulfonamides.
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PMID:Genetic and physical characterization of trimethoprim resistance plasmids from Shigella sonnei and Shigella flexneri. 282 49

We have investigated the presence of the aerobactin system and the location of the aerobactin genes in enteroinvasive strains of Escherichia coli. Also, we cloned the aerobactin region and its flanking sequences from the chromosome of a strain of Shigella flexneri and compared the molecular organization of the aerobactin genes in the two genera. Of the 11 enteroinvasive E. coli strains studied, 5 possessed the aerobactin genes, which were located on the chromosome in each case. These strains produced and utilized aerobactin and also were susceptible to the bacteriocin cloacin-DF13. Restriction endonuclease mapping and hybridization experiments showed that the regions corresponding to the aerobactin-specific sequences were very similar in both enteroinvasive E. coli and S. flexneri. However, differences were found in the region corresponding to the aerobactin receptor gene. The regions flanking the aerobactin system in enteroinvasive E. coli and S. flexneri exhibited some similarities but were different from those in pColV-K30. Under iron-limiting conditions, aerobactin-producing enteroinvasive E. coli and S. flexneri synthesized outer-membrane proteins of 76 and 77 kDa, respectively, which cross-reacted immunologically with rabbit antiserum raised against the 74 kDa pColV-K30-encoded ferric aerobactin receptor.
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PMID:Flanking and internal regions of chromosomal genes mediating aerobactin iron uptake systems in enteroinvasive Escherichia coli and Shigella flexneri. 283 21

Although Shigella flexneri possesses the genes for two siderophore systems, enterobactin and aerobactin, the enterobactin system is only rarely utilized. To investigate the regulation of enterobactin expression in S. flexneri, all of the genes specifically required for synthesis and transport of enterobactin were cloned from both an expressing (Ent+) and a nonexpressing (Ent-) strain. Notable differences between the cloned genes included endonuclease restriction site changes and the presence of an IS1 element in the Ent- DNA. Southern hybridization revealed that this IS1 element, present at the 3' end of the entF gene, is conserved at this location in different strains and serotypes of Ent- S. flexneri. The Ent- cloned genes were tested for their ability to complement the defect in 11 different Escherichia coli enterobactin mutants. The Ent- genes fully complemented nine mutants but failed to complement the entF mutant AN117 and only partially complemented the entE mutant AN93. Whole-cell RNA isolated from E. coli and the Shigella strains was hybridized to 32P-labeled DNA containing the entB gene or a fragment carrying a portion of the entF gene. E. coli and the Ent+ Shigella strains exhibited derepression of transcription of these genes in low-iron media. Transcription in the Ent- strain remained repressed regardless of iron concentration. Expression of the entB and entF genes was also examined in an Ent- Shigella fur mutant. Expression of entF was only partially derepressed and entB remained fully repressed at all iron concentrations, suggesting that factors other than Fur are responsible for the repression of these enterobactin genes in the Ent- Shigella strains.
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PMID:Genetics and regulation of enterobactin genes in Shigella flexneri. 297 58

A group of transfer derepressed R factors (pKMR plasmids) was identified with the methods of conjugation and transformation in 2 antibiotic resistant strains of the dysentery bacillus, i. e. Shigella flexneri 3c and Sh. sonnei isolated from patients with acute dysentery. The antibiotic resistance in S. flexneri was controlled by plasmid pKMR 202-2 (Sm Tc Cm Km Su) with a molecular weight of 59 MD and that in Sh. sonnei was controlled by 2 plasmids, i. e. pKMR 203-2 (Ap Sm Tc Cm Km Su) and pKMR 203-3 (Ap Tc Cm Su) with molecular weights of 99 and 65 MD, respectively. When treated with restriction endonuclease BamH 1 plasmids pKMR 203-2 and pKMR 203-3 had each only one fragment with the similar molecular weight (7.7 MD). At the same time plasmid pKMR 202-3 differed from plasmid pKMR 202-2 only by the presence of an additional fragment BamH 1 with a molecular weight of 7.7 MD. The other 6 fragments of both plasmids had similar molecular weight. The data suggest that though plasmids pKMR 202-2 and pKMR 203-3 differ in their phenotypic features, they are closely related and possible belong to the same Inc-group. It was also shown that plasmid pKMR 202-2 segregated on transformation with formation of a nonconjugative plasmid pKMR 202-1 with a molecular weight of 16.6 MD.
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PMID:[Physicochemical characteristics of transfer derepressed pKMR plasmids]. 703 38


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