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Biomedical subjects

R W Hedges

Publications and source records attributed to R W Hedges.

At least 37 records · Page 2Linked to original sources
PubMed1982

Phages C-2 and J: IncC and IncJ plasmid-dependent phages, respectively.

Phages C-2 and J were isolated from sewage. Phage C-2 was filamentous and formed plaques on Salmonella typhimurium strains carrying various C plasmids. It also plated on Proteus mirabilis and Serratia marcescens strains carrying particular C plasmids, but failed to form plaques on lines of Escherichia coli K12 strains harbouring most of these plasmids, although in all cases, phage multiplication on the strains was demonstrated. No phage increase occurred in any strain which lacked a C plasmid or contained plasmids of other incompatibility groups. The phage was sensitive to chloroform and, unlike other filamentous bacterial viruses, adsorbed to shafts of conjugative pili. It had a disc-like structure at the end which attached to the pilus. Phage C-2 had a buoyant density of 1 . 30 g cm-3 and a single-stranded circular DNA genome of 3 . 0 MDal. Phage J had an hexagonal head with an inter-apical distance of 40 nm and a short noncontractile tail. It was resistant to chloroform and diethyl ether. The phage formed plaques or propagated on E. coli strains harbouring some IncC plasmids and all IncJ and IncD plasmids tested. The phage did not form plaques but propagated on P. mirabilis and Ser. marcescens strains carrying these plasmids. It did not plate or propagate on S. typhimurium strains harbouring the plasmids. The plaques were very hazy and variable in size. The phage attached sparsely, at a site which appeared to be located at the base of the tail, to sides of conjugative pili.

Adsorption↗
PubMed1982

Plasmid R394 is a cointegrate.

Plasmids R394a and R394b which cointegrate to form R394 are described. They have molecular masses of 102 +/- 4 and 11.0 +/- 0.4 MDal, belong to the T and N incompatibility groups and confer resistance to kanamycin and ampicillin, respectively. R394a is self transmissible and mobilizes R394b, which is non-self transmissible. These findings clarify anomalies in the behaviour of R394 and support suggestions based on the properties of variant phages derived from R394.

Conjugation, Genetic↗
PubMed1982

Phages I alpha and I2-2: IncI plasmid-dependent bacteriophages.

Phage I alpha was isolated from sewage from Windhoek, South West Africa. It formed relatively clear plaques about 2 mm in diameter, on sensitive strains of Escherichia coli K12 and Salmonella typhimurium LT2. The phage had an hexagonal outline with a diameter of about 24 nm, contained RNA and was resistant to chloroform. Phage I alpha formed plaques or propagated only on organisms carrying I1 plasmids or the I gamma plasmid R621a. The efficiency of plating was higher on E. coli than on S. typhimurium hosts. The phage adsorbed along the length of shafts of I1 pili. Phage I2-2 was isolated from Pretoria sewage. It was a filamentous virus and individual virions varied considerably in length. Phage I2-2 formed turbid plaques which varied from pin point to about 1 mm in diameter on all hosts. It was resistant to RNAase and sensitive to chloroform. Phage I2-2 had a spectrum of activity limited to strains harbouring I2 plasmids but the adsorption site could not be demonstrated. The phage was not related serologically to phages Ifl or PR64FS.

Bacteriophage Typing↗
PubMed1982

Spread of a "Pseudomonas-specific" beta-lactamase to plasmids of enterobacteria.

Eleven isolates including Escherichia coli, Salmonella enteritidis, and Shigella sonnei, obtained in Brazil, Hong Kong, Indonesia, Thailand, and the United States, were found to produce beta-lactamase of the PSE-1 type, which was previously considered to be Pseudomonas specific. The enterobacterial strains produced a beta-lactamase with the same isoelectric point, immunological reactions, and substrate profile as those of the prototype PSE-1 enzyme determined by Pseudomonas plasmid RPL11. The producer strains were resistant to multiple antibiotics, and all contained plasmids, ranging in size from 37 x 10(6) to 130 x 10(6), that belonged to at last six incompatibility groups. Plasmids of IncH2 and IncFIme were shown to contain 8 x 10(6)-molecular-weight transposons Tn1401 and Tn1402 that encoded PSE-1 beta-lactamase production, resistance to streptomycin and spectinomycin via AAD(3"), and resistance to sulfonamide. PSE-1 beta-lactamase was not Pseudomonas specific and appeared to have spread among plasmids found in enterobacteria by transposition.

DNA Transposable Elements↗
PubMed1981

Phage C-1: an IncC group; plasmid-specific phage.

A phage was isolated from sewage and shown to form plaques on Salmonella typhimurium strains carrying C plasmids. It failed to multiply on strains lacking plasmids of this group. It also plated on Proteus mirabilis and Serratia marcescens strains carrying various IncC plasmids but failed to form plaques on Escherichia coli strains harbouring most of these plasmids, although in all cases, phage multiplication on the strains was demonstrated. No phage increase occurred in any of the strains which lacked an IncC plasmid or contained plasmids of other incompatibility groups. The phage is small, hexagonal in outline, contains RNA, is resistant to chloroform and adsorbs to the shafts of pili coded for by IncC plasmids.

Bacteriophages↗
PubMed1981

Phage X: a plasmid-dependent, broad host range, filamentous bacterial virus.

Phage X was isolated from sewage as plating on Escherichia coli or Salmonella typhimurium strains harbouring the incompatibility group X plasmid R6K. It also plated on a strain of Serratia marcescens carrying this plasmid. It failed to form plaques on Proteus mirabilis, P. morganii or Providencia alcalifaciens harbouring R6K, but did multiply on them. No phage increase occurred with homologous R- strains. Phage X also plated or registered an increase in titre on E. coli or S. typhimurium strains carrying various plasmids of incompatibility groups M, N, P-1, U or W as well as the unassigned plasmid R775. It adsorbed to pili determined by a group P-10 plasmid in a Pseudomonas aeruginosa strain but did not multiply on this organism. The phage was filamentous and curly, resistant to ribonuclease and diethyl ether and sensitive to chloroform. It adsorbed to the tips of pili.

Adsorption↗
PubMed1981

Phage t: a group T plasmid-dependent bacteriophage.

Phage t was isolated from sewage from Pretoria. It formed plaques only on Escherichia coli and Salmonella typhimurium strains that carried plasmids belonging to incompatibility group T. Five of six group T plasmids permitted visible lysis of R+ host strains. There was no visible lysis of E. coli J53-2 or S. typhimurium LT2trpA8 carrying the T plasmid Rts1 although the strains supported phage growth as indicated by at least a 10-fold increase in phage titre. The latter strains transferred the plasmid at high frequency to E. coli strain CSH2 and the resulting transconjugants plated the phage. Proteus mirabilis strain PM5006(R402) failed to support phage growth although it transferred the plasmid and concomitant phage sensitivity to E. coli J53-2. The phage was hexagonal in outline, RNA-containing, resistant to chloroform and adsorbed to the shafts of pili determined by T plasmids.

Escherichia coli↗
PubMed1981

Phage Folac: an Folac plasmid-dependent bacteriophage.

By enriching sewage with Escherichia coli or Salmonella typhimurium strains harbouring the plasmid EDP208, a constitutive pilus-producing derivative of plasmid F olac, a phage was isolated which plated on these two organisms but not on isogenic strains without the plasmid. The phage was named F olac; it has a hexagonal outline with a diameter of 28 nm, contained RNA, was resistant to chloroform, and probably adsorbed preferentially to the sides of EDP208 pili very near the tip. Phage multiplication could be demonstrated on E. coli or S. typhimurium strains carrying the plasmid F olac, but an increase in titre did not occur on E. coli strains carrying plasmids of the F complex. Results of phage multiplication experiments on strains carrying the depressed pilus-producing plasmids R71 or TP224-Tc, which determine pili serologically related to those of EDP208, were inconclusive. Phage F olac was found to be serologically related to phage UA-6, another isolate specific for EDP208.

Escherichia coli↗
PubMed1980

Dissemination of an antibiotic resistance plasmid in hospital patient flora.

The 2'' aminoglycoside nucleotidyltransferase, AAD (2''), which adenylates gentamicin, tobramycin, and kanamycin, became prevalent over several months in multiple strains and species of Enterobacteriaceae isolated at one hospital. Eight plasmids with the gene for this enzyme purified from different strains and species isolated at different times had similar EcoRI digestion fragments, indicating that the gene had disseminated on one plasmid without transposition. This 56.5-megadalton plasmid of incompatibility group M, which also carried three other resistance genes, spread, at first, largely in one strain of Klebsiella pneumoniae, which later disappeared. It transferred to some strains which tended not to colonize other patients and later circulated predominantly in Serratia marcescens. Computer surveillance of routine hospital laboratory results was able to detect and trace the gene and the plasmid and measure their effect on resistance prevalence.

Aminoglycosides↗
PubMed1979

The nature of the genetic determinant for the SHV-1 beta-lactamase.

In two unrelated plasmids of incompatibility groups FII and N the gene for the SHV-1 beta-lactamase exists as part of a transposable element of molecular weight 9.5 megadaltons. This transposon has moved onto plasmids of at least three incompatibility groups; PI, Ialpha and J. This confirms the suggestion that the recent spread of the SHV-1 beta-lactamase has been associated with the transposition of the genetic determinant of this enzyme between unrelated plasmids.

Base Sequence↗
PubMed1979

Properties of R plasmid R772 and the corresponding pilus-specific phage PR772.

R plasmid R772 was isolated from a strain of Proteus mirabilis and is a self-transmissible P-1 incompatibility group plasmid having a molecular weight of about 27 x 10(6). It renders bacterial hosts resistant to kanamycin. Phage PR772 was isolated as a phage dependent on the presence of R772 in bacterial hosts. It is hexagonal-shaped with a diameter of 53 nm, has a thick inner membrane and no tail. Vaguely defined appendages are sometimes apparent at some vertices and the phage possesses double-stranded DNA. The DNA has a guanine plus cytosine molar content of 48%. The phage is sensitive to chloroform and has a buoyant density of 1.26 g cm(-3). These observations suggested that the inner membrane of the phage could contain lipid. Phage PR772 differs in morphology from the double-stranded DNA plasmid-specific phages PR4 and PRR1 which adsorb to tips and sides, respectively, of sex pili coded for by P-1 incompatibility group plasmids. Phage PR772 formed clear plaques which varied in diameter. Serologically, phages PR772 and PR4 are possibly related though very distantly, but the two phages have identical host ranges. Phage PR772 adsorbed by one of its apices to tips of sex pili coded for by plasmid R772 in Escherichia coli. It also formed plaques on Salmonella typhimurium Proteus morganii and Providence strains harbouring this plasmid as well as strains of E. coli carrying plasmids of incompatibility groups N or W. The phage produced areas of partial clearing on lawns of P. mirabilis PM5006 harbouring plasmid R772, the P-1 incompatibility group plasmid RP4, the W group plasmid RSa or the N group plasmid N3, and on lawns of Providence strain P29 carrying plasmid RP4.

Bacteriophages↗
PubMed1979

Recombinant plasmids formed in vivo carrying and expressing two incompatibility regions.

The formation in vivo of recombinants between a plasmid of incompatibility group N (R1010-10) and plasmids of groups P (R751) and W (R388) is described. From examination of the molecular weights of these recombinant plasmids, they appear to be cointegrates. These cointegrates have the incompatibility properties of both 'parent' plasmids.

Anti-Bacterial Agents↗
PubMed1979

Types of beta-lactamase determined by plasmids in gram-negative bacteria.

Two species of beta-lactamase determined by plasmids in enteric bacteria that show some resemblance to TEM enzymes are described. Both are distinct from all other plasmid-mediated beta-lactamases and differ from the TEM beta-lactamases in ability to hydrolyze some substrates, in isoelectric point, in immunological specificity, and in susceptibility to inhibition. One of the enzyme species, mediated by plasmid p453, has been briefly described previously. We have discovered that this beta-lactamase, designated SHV-1, is unique in its response to inhibition by the sulfhydryl group reagent p-chloromercuribenzoate, because the hydrolysis of cephaloridine but not that of benzylpenicillin is affected. This enzyme is found in a variety of plasmid types which were transferred from several bacterial species collected from a wide geographic range. The other enzyme species is novel; only a single plasmid determining this kind of beta-lactamase (designated HMS-1) has been detected.

Cephalosporins↗
PubMed1978

An explanation for the apparent host specificity of Pseudomonas plasmid R91 expression.

Pseudomonas aeruginosa strain 9169 has been reported to contain a plasmid that expresses resistance to carbenicillin (Cb), kanamycin (Km), and tetracycline (Tc) in Escherichia coli but resistance only to Cb in certain Pseudomonas recipients. The triply resistant plasmid in E. coli belonged to incompatibility (Inc) group P or P-1, whereas the singly resistant plasmid in P. aeruginosa was compatible with IncP-1 plasmids and other plasmids of established Inc specificity but incompatible with plasmid pSR1 that is here used to define a new Pseudomonas Inc group P-10. Additional physical and genetic studies showed that strain 9169 contained not one but two plasmids: IncP-1 plasmid R91a, determining the Cb Km Tc phenotype, and IncP-10 plasmid R91, determining Cb that differed in molecular weight and in EcoRI and BamHI restriction endonuclease recognition sites. Plasmid multiplicity rather than host effects on plasmid gene expression can account for differences in the phenotype of strain 9169 transconjugants to E. coli and P. aeruginosa.

Carbenicillin↗