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)

Klebsiella marker systems include determination of susceptibility patterns, serotype, bacteriocin susceptibility, bacteriophage susceptibility, biotype, and plasmid content, size and endonuclease fragment size. Susceptibility patterns are useful only if unusual patterns (ie, aminoglycoside resistance) occur. Serotypes are stable, reproducible markers. Over 90% of isolates can be serotyped and epidemiologically unrelated strains are widely distributed among the 72 standard types. Antisera are not available commercially except to types 1 to 6 and serotyping is expensive and time-consuming. Bacteriocin susceptibility typing is easier and cheaper but reproducibility is sometimes poor. Depending on the producer strains used, between 67% and 96% of strains are typable. As a single typing method, bacteriophage typing is not very sensitive. Only 70% of strains are typable and 20% are of a single type. There are two major problems with most biotyping systems: poor reproducibility and poor sensitivity. A high percent of strains is the same type. Plasmid analysis is technically the most complicated but is important if strains are aminoglycoside resistant. No one method is ideal, and characterization of isolates from an outbreak is best done by using several different marker systems.
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PMID:Klebsiella marker systems. 388 91

An outbreak of 12 cases of infection occurred over a 9-month period in a Regional Referral Neonatal Intensive Care Unit. The pathogen was a gentamicin- and multiply-resistant Klebsiella oxytoca (K55), of high virulence. Seven of 10 neonates with septicaemia died, the majority within 24 h of the onset of infection. Screening for the resistant klebsiella revealed that 64 (39 per cent) of 164 neonates became carriers and remained so throughout their stay. Hand carriage appeared to be a mode of cross-contamination and infection. Cohorting colonized neonates together with rigorous cross-infection control measures eliminated this organism from the unit after 29 weeks. There is evidence to suggest that in one case the infecting organism was acquired from a contaminated blood gas analyser. It is necessary to use incompatibility grouping and restriction endonuclease digestion for complete characterization of plasmids and their molecular weights. However, the finding that each isolate examined carried the same five plasmids as judged by co-electrophoresis on agarose gels, and expressed the same extent and degree of transferable antibiotic resistance provides evidence to suggest that this outbreak was due to spread of a resistant clone of K. oxytoca (K55).
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PMID:Klebsiella infection in a neonatal intensive care unit: role of bacteriological surveillance. 608 92

The sizes of the zones of inhibition around routinely tested antibiotic disks classified gentamicin-resistant isolates of Klebsiella pneumoniae from one hospital into four major antibiotype classes. From each isolate of the prevalent class (A1), two plasmids could be transferred conjugally. One carried genes for resistance to tetracycline, sulfonamides, and chloramphenicol, and for the SHV beta lactamase. The other carried genes for two aminoglycoside-inactivating enzymes, APH (3')-I and AAC (3)-III, for the TEM 1 beta lactamase, and for resistance to sulfonamides. Transconjugants of either plasmid from any A1 isolate yielded the same DNA fragments after restriction endonuclease digestion, but the two plasmids had no fragments in common. Fragments or genes from either plasmid were variously combined or lacking in plasmids from variant isolates (A2, A3, and A4). Plasmids transferable from isolates of classes B and C shared no common DNA restriction fragments with each other or with either plasmid from Class A. Fragments and genes of the plasmids from C isolates, however, were identical with those of a plasmid endemic in a nearby hospital. Routine monitoring by diagnostic microbiology laboratories of distinctive antibiotypes and of the plasmids that produce them would aid infection control and antibiotic usage policy.
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PMID:Diagnostic microbiology laboratory susceptibility test results discriminate distinctive antibiotic resistance plasmids. 609 87

The genetic and biochemical properties of an endonuclease mediated by the mutagenesis-enhancing plasmid pKM101 have been investigated. Taking advantage of the observation that this endonuclease, unlike host-coded DNases, is active in the presence of EDTA, we have developed an assay with nondenaturing acrylamide gels containing DNA. We have localized the plasmid DNA sufficient for nuclease expression to a 0.8-kilobase sequence that is near regions of DNA necessary for conjugal transfer, and we have determined that this gene is transcribed clockwise on the pKM101 map. The pKM101 gene mediating this activity codes for a 16,000-dalton protein, which is the same molecular mass as the nuclease monomer, leading us to conclude that this gene codes for the nuclease itself rather than for an activator of some host-coded enzyme. Cellular fractionation experiments have shown that the enzyme is localized in the periplasm. We have not been able to demonstrate any physiological role for the enzyme, but we have ruled out a direct involvement of the nuclease in any of the following known plasmid-associated phenotypes: (i) mutagenesis enhancement, (ii) conjugal transfer, (iii) entry exclusion, (iv) fertility inhibition of coresident P-group plasmids, (v) killing of Klebsiella pneumoniae used as conjugal recipients, and (vi) plasmid curing induced by treatment of cells with fluorodeoxyuridine. In addition, we have shown that the enzyme does not restrict bacteriophage or affect the ability of the host to utilize DNA as a source of thymine. Finally, we have shown that 11 of the 26 other plasmids tested also elaborated EDTA-resistant DNases.
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PMID:Genetic localization and characterization of a pKM101-coded endonuclease. 622 33

Some restriction endonuclease fragments of nif DNA, when carried on small multicopy plasmids, inhibited nif expression in Klebsiella pneumoniae. A study of this inhibitory effect revealed, (1) that overproduction of the nifL gene product inhibited transcription of two nif operons examined, nifJ and nifHDKY and, (2) that when transcription was initiated from the promoter of the nifHDKY operon on multicopy plasmids there was a corresponding decrease in the transcription rates of the chromosomally located nifJ and nifHDKY but not the nifLA operon. Studies of transcription in vivo also showed that the nifA gene product was essential for transcription initiation from the nifHDKY and nifBQ promoters. These results, taken with earlier observations (see Discussion) provide evidence that the nifL and nifA gene products are respectively a repressor and activator of nif transcription initiation from all nif promoters except that of the nifLA operon.
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PMID:The use of cloned nif (nitrogen fixation) DNA to investigate transcriptional regulation of nif expression in Klebsiella pneumoniae. 627 43

Multicopy plasmids containing the hisDG region of Klebsiella pneumoniae were mutagenized with transposon Tn5. The resulting plasmids were examined for their ability to complement hisD and hisG mutations in Escherichia coli. The physical location of Tn5 on each of the hisD::Tn5 and hisG::Tn5 plasmids was determined by restriction endonuclease analysis. By combining the two types of data, a precise correlated physical and genetic map of the K. pneumoniae hisDG region was constructed. Based on this analysis, the minimum sizes of the hisD and the hisG genes were calculated to be 1100 bp and 900 bp, respectively. The hisO(P) region was also identified. The insertional specificity of transposon Tn5 was shown to be very low. One unanticipated result was obtained: Tn5 insertions in the plasmid-borne hisG gene were not polar on hisD.
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PMID:Construction of a correlated physical and genetic map of the Klebsiella pneumoniae hisDGO region using transposon Tn5 mutagenesis. 631 5

Restriction endonuclease-digested deoxyribonucleic acid (DNA) from 17 slow-growing Rhizobium strains was hybridized with 32P-labeled DNA of the Klebsiella pneumoniae nitrogenase structural gene (nifKDH) region. Sixteen of these strains contained two or more fragments that were homologous to K. pneumoniae nifKDH after cleavage with EcoRI or HindIII. Hybridization with nifKDH subclones revealed that most of the Rhizobium fragments were homologous to the HindIII-EcoRI portion of nifKDH (corresponding to the nifDH region), although fragments homologous to the EcoRI-HindIII portion of nifKDH (corresponding to the nifK region) were also present. Comigrating nif-homologous restriction endonuclease fragments were observed for strains isolated from different geographic locations and from nodules of different plant species. Nearly identical hybridization patterns were obtained for five R. japonicum strains which clearly differed in the pattern of restriction endonuclease fragments from their chromosomal DNA. This indicates that there is a high degree of conservation of DNA sequence surrounding the region of nif homology in these strains.
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PMID:Conservation of DNA regions adjacent to nifKDH homologous sequences in diverse slow-growing Rhizobium strains. 631 24

Cloned nitrogen fixation (nif) genes from Klebsiella pneumoniae hybridize to DNA from 19 out of 19 widely divergent nitrogen-fixing bacterial strains but do not hybridize to DNA from 10 different non-nitrogen-fixing species. K. pneumoniae nif DNA fragments that hybridize to DNA from other species contain part of the three structural genes that code for nitrogenase polypeptides. We have utilized this homology to clone an EcoRI restriction endonuclease fragment from Rhizobium meliloti that hybridizes to the K. pneumoniae nif structural genes. Some of the species whose DNA hybridizes with K. pneumoniae nif DNA have been postulated to have diverged from K. pneumoniae 3 x 10(9) years ago. Nitrogenase genes are the only known example of such highly conserved prokaryotic translated genes. Nitrogenase genes are either extraordinarily conserved in evolution or have been exchanged between different nitrogen-fixing species relatively recently in evolutionary time.
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PMID:Interspecies homology of nitrogenase genes. 698 49

The prevalence of possible cross-transmission of selected bacteria (Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, Pseudomonas aeruginosa, Staphylococcus aureus, and enterococci) among infected patients was evaluated in five intensive care units (ICUs) over 6 months. A total of 284 isolates from clinical specimens were typed by plasmid profile analysis (E. coli, K. pneumoniae, and E. cloacae), restriction endonuclease analysis of plasmid DNA (S. aureus), and/or pulse-field gel electrophoresis of chromosomal DNA (P. aeruginosa, enterococci, S. aureus, and other bacteria without plasmid DNA). By typing criteria, only 13% of the 177 isolates obtained after > 2 days in an ICU were classified as possibly cross-transmitted. Many patients whose cultures yielded bacteria of an identical type may have been the sources rather than the recipients of these organisms. Episodes of possible cross-transmission were scattered among all ICUs, usually affected only two patients, and were associated with most bacterial species. These data suggest that endemic bacterial cross-transmission in ICUs is relatively infrequent and that cross-transmitted bacteria are not common causes of endemic ICU-related nosocomial infections.
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PMID:Assessment of bacterial cross-transmission as a cause of infections in patients in intensive care units. 808 55

Restriction enzyme analysis by pulsed-field gel electrophoresis (PFGE) was developed for differentiation of hospital isolates of Klebsiella pneumoniae. Restriction patterns generated by SpeI digestion of genomic DNAs of 36 isolates from patients in two major teaching hospitals established 34 PFGE types. All strains were typable by this technique and the SpeI restriction patterns were reproducible, stable and easy to interpret. As PFGE profiles generated were heterogenous, the incidence of cross-infection appeared to be low in each of the hospitals. The higher discriminatory power of PFGE when compared to conventional restriction endonuclease analysis (REA) suggests that this technique will be very useful for epidemiological investigations of nosocomial K. pneumoniae outbreaks.
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PMID:Pulsed-field gel electrophoresis for differentiation of hospital isolates of Klebsiella pneumoniae. 810 75


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