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W B Grubb

Publications and source records attributed to W B Grubb.

At least 55 records · Page 3Linked to original sources
PubMed1990

Conjugal transfer of plasmid pWBG637 from Staphylococcus aureus to Staphylococcus epidermidis and Streptococcus faecalis.

Plasmids pWBG636 (GmR) and pWBG642 (EmR) derived from the conjugative plasmid pWBG637 were tested for ability to transfer conjugatively to Staphylococcus epidermidis, Streptococcus faecalis, Bacillus subtilis and Escherichia coli. Both plasmids transferred to S. epidermidis and Strept. faecalis but not to B. subtilis and E. coli. Once in S. epidermis and Strept. faecalis they were transferred back to S. aureus. Restriction endonuclease analysis showed that the plasmids were stably maintained in S epidermidis and Strept. faecalis.

Conjugation, Genetic↗
PubMed1990

A new class of conjugative plasmid in Staphylococcus aureus.

Plasmid pWBG637, a Staphylococcus aureus conjugative plasmid having no known resistance phenotype, was compared with other conjugative plasmids in S. aureus by restriction endonuclease analysis, incompatibility testing and DNA-DNA hybridisation. It differed from the other conjugative plasmids on all three criteria and thus belongs to a new class of conjugative plasmids.

DNA Restriction Enzymes↗
PubMed1990

Excision of a conjugative plasmid from the staphylococcal chromosome.

Staphylococcus aureus isolate WBG1003 resistant to benzyl penicillin, cadmium, arsenate and streptomycin harbours two plasmids of 38.8 (pWBG621) and 4.4 (pWBG625) kb. In conjugation experiments two types of streptomycin-resistant transconjugants were obtained; one carried a 4.4-kb plasmid and the other, a 34.5-kb and a 4.4-kb plasmid. The 34.5-kb plasmid (pWBG620) has been found to be conjugative and able to mobilise non-conjugative plasmids. It has no detectable resistance phenotype and has not been detected in WBG1003 nor in the recipient used in the conjugation experiments. Restriction endonuclease analysis and DNA-DNA hybridisation have revealed that pWBG620 is unrelated to pWBG621 present in strain WBG1003. The data presented indicate that pWBG620 is in the chromosome of strain WBG1003 and that it excises during conjugation.

Blotting, Southern↗
PubMed1987

The international spread of methicillin-resistant Staphylococcus aureus.

A genetic analysis of representative methicillin-resistant Staphylococcus aureus (MRSA) being isolated in London and Dublin hospitals has demonstrated that the epidemic strains from two London hospitals are different from the Dublin strains, but indistinguishable from the epidemic strains of eastern Australia. The possibility that some strains of MRSA are more likely than others to spread within hospitals is discussed.

Australia↗
PubMed1986

Conjugative, staphylococcal plasmids carrying hitch-hiking transposons similar to Tn554: intra- and interspecies dissemination of erythromycin resistance.

Two staphylococcal plasmids, pWG4 and pWG25, encode production of a diffusible pigment and resistance to erythromycin and spectinomycin. The former was found occurring naturally in a clinical isolate of Staphylococcus aureus and the latter in S. epidermidis. Both plasmids are conjugative, capable of high-frequency, interspecies transfer, only isolated in the open-circular form and identical in molecular weight and pattern of restriction-endonuclease fragments. The only difference between the plasmids is in the expression of resistance, pWG4 encoding inducible and pWG25 constitutive erythromycin resistance. The resistance determinants of both plasmids behave as hitch-hiking transposons in cultural conditions that favour phage-mediated or phage-independent conjugation, always inserting a copy of themselves into the recipient's chromosome, except in S. epidermidis in which the chromosomal insertion site may be absent. The resistance determinants have been cloned and located on a 4 X 7 kbp EcoR1/HindIII restriction fragment which has a restriction map similar to that of the right arm of Tn554 (Murphy and Lofdahl, 1984). The hitch-hiking transposon of plasmid pWG25 has been designated Tn3853.

DNA Restriction Enzymes↗
PubMed1986

Isolation and characterisation of a family of small plasmids encoding resistance to nucleic acid-binding compounds in Staphylococcus aureus.

A family of small plasmids encoding resistance to nucleic acid-binding (NAB) compounds has recently been identified in strains of Staphylococcus aureus isolated in Italy, Texas and Western Australia. The mol. wts of the NAB-resistance plasmids are in the range (1.5-1.9) X 10(6) and all but one encode resistance to acridine yellow, ethidium bromide and quaternary ammonium compounds. The largest of the plasmids, pWG1773, differed in that it did not confer resistance to ethidium bromide. Restriction enzyme analysis of these plasmids revealed four distinct patterns corresponding to plasmids of four different mol. wts and physical maps were constructed based on the restriction patterns. Two plasmid types of molecular sizes approximately 2440 and 2240 base pairs had a 610-base pair region in common. Physical maps of the other two plasmid types were not related. The presence of a family of small NAB-resistance plasmids which carry no other known phenotypic markers provides further evidence for the strong selective advantage associated with maintenance of this determinant in clinical isolates of S. aureus.

Drug Resistance, Microbial↗
PubMed1986

Comparison of phage-mediated and conjugative transfer of staphylococcal plasmids in vitro and in vivo.

A strain of Staphylococcus aureus was constructed with which to compare transfer of resistance plasmids by the mechanisms of phage-mediated conjugation and conjugation. Transfer by each mechanism could be distinguished by the patterns of resistances transferred. Conjugation was favoured on dry absorbent surfaces, e.g., human skin, tissue and surgical gauze, whereas phage-mediated conjugation was favoured in fluids, e.g., milk and urine. The degree of hydration of the mating cells is postulated as one factor determining whether plasmids are transferred by phage-mediated conjugation or conjugation. Preliminary evidence indicates that topical creams and ointments affect the conjugative transfer of plasmids.

Anti-Bacterial Agents↗
PubMed1985

Genetics and epidemiology of methicillin-resistant Staphylococcus aureus isolated in a Western Australian hospital.

Strains of methicillin-resistant Staphylococcus aureus (MRSA) isolated in the Royal Perth Hospital (RPH) in Western Australia have been analysed genetically and three main types were characterized: (i) strains similar to those isolated in Europe before 1973. These strains caused small outbreaks in the RPH during the period 1966-1974, but have not been isolated in recent years, except from one patient with reactivation of osteomyelitis after 16 years; (ii) strains of the type prevalent in eastern and northern Australia, one of which caused a difficult-to-control outbreak in the RPH in 1982. Strains of this type have previously been isolated only from patients who had been in hospitals in eastern and northern Australia, but recently were isolated also from other patients--which indicates that this type of MRSA is now present in the Western Australian community; and (iii) strains, which are genetically different from either of the above two types, were isolated from patients who had been in hospitals in Southeast Asia, but have not yet caused an outbreak in the RPH.

Australia↗
PubMed1985

A plasmid for diffusible pigment production in Staphylococcus aureus.

Production of diffusible pigment in a strain of Staphylococcus aureus (WG260) has been associated with a plasmid of c.26 megadaltons which can be co-transduced with inducible erythromycin and spectinomycin resistance. However, the diffusible pigment plasmid can be lost from the transductants without loss of inducible erythromycin and spectinomycin resistance. The evidence suggests that the resistance determinants are located on an element similar or identical to transposon Tn554, and, during transduction of the diffusible pigment plasmid, a copy of the resistance determinants always inserts into the chromosome of the transductant. This is the first report of such an element occurring on a plasmid in a clinical isolate of S. aureus. To date, the diffusible pigment plasmid has been isolated only as the open-circular conformation of plasmid DNA and is probably a highly relaxable plasmid. The production of the orange, diffusible pigment was shown to be independent of colony pigmentation.

Chromosome Mapping↗
PubMed1985

A conjugative plasmid encoding production of a diffusible pigment and resistance to aminoglycosides and macrolides in Staphylococcus aureus.

A methicillin-resistant strain of Staphylococcus aureus, WG512, was isolated in 1968 and has been shown to harbour a plasmid, pWG14, which encodes the production of a diffusible pigment and resistance to kanamycin, neomycin, streptomycin, lincomycin, erythromycin and spectinomycin. Plasmid pWG14 has only been detected as a slowly migrating band of DNA during agarose-gel electrophoresis, and this was thought to be the open-circular form of the plasmid with an estimated molecular weight of 30-34 Mdal. The transfer properties of this plasmid were compared with a non-conjugative plasmid encoding tetracycline resistance and the class 2, conjugative plasmid described by Archer and Johnston (1983). Plasmid pWG14 shared many of the conjugative properties of the latter plasmid, including the ability to transfer at high frequency on the surface of a filter membrane and to transfer between non-lysogenic strains in the absence of Ca++ and in the presence of citrate of DNase I. However, unlike the class 2 plasmid, pWG14 was able to transfer in broth culture at low frequency and did not mobilise the non-conjugative plasmid. Furthermore, the class 2 plasmid and pWG14 were shown to belong to different incompatibility groups. A derivative of WG512, which had lost the ability to produce the diffusible pigment along with plasmid pWG14 but had retained the resistance determinants of plasmid pWG14 in the chromosome, was used to demonstrate that the conjugative mechanism of pWG14 was a property of the plasmid and not the resistance determinants.

Aminoglycosides↗
PubMed1985

Distribution of plasmid-borne resistance to nucleic acid binding compounds in methicillin-resistant Staphylococcus aureus.

Methicillin-resistant Staphylococcus aureus (MRSA) which are epidemic in Australian hospitals have been found to be genetically different from strains previously isolated in Australia and in Europe. A characteristic feature of the recent Australian isolates is a plasmid which encodes resistance to nucleic acid binding compounds (NAB) such as propamidine isethionate. Of 753 MRSA strains isolated from around the world in 1980-1983, c. 60% were NAB resistant. The determinant for this resistance could be transferred from 90% of strains to a recipient strain in mixed culture. A plasmid analysis revealed that, in general, the largest plasmid of MRSA isolates coded for NAB resistance and may carry other determinants for penicillinase production and resistance to gentamicin, trimethoprim, neomycin, tetracycline, cadmium and mercury. Some plasmids exhibited unusual behaviour with the appearance of deletion mutants after transfer and, in one case, a high-frequency alteration in the expression of gentamicin resistance from high-level to low-level resistance, correlated to a deletion of c. 0.5 megadalton of plasmid DNA. These results demonstrate that these NAB-resistance plasmids are not unique to Australian MRSA strains but are widely distributed throughout the world.

Benzamidines↗
PubMed1985

Evolution of Australian isolates of methicillin-resistant Staphylococcus aureus: a problem of plasmid incompatibility?

Methicillin-resistant Staphylococcus aureus (MRSA), currently causing problems in Australian hospitals, have chromosomal penicillinase and carry a new family of incompatibility group I (IncI) plasmids that encode resistance to nucleic acid-binding compounds (NAB). These plasmids may carry additional determinants for penicillinase production and resistance to gentamicin and trimethoprim. By comparison, earlier MRSA isolates from Australia were NAB-sensitive and the penicillinase determinants were carried on IncI plasmids. The possibility that these newer MRSA isolates have the same 'clonal' origin as other MRSA isolates has been investigated. Forcible maintenance of IncI penicillinase plasmids and NAC-resistance plasmids in the same cells resulted in various recombination events. Similar recombination events to those generated in the laboratory have been found in MRSA isolates.

Australia↗
PubMed1985

A resistance determinant to nucleic acid-binding compounds in methicillin-resistant Staphylococcus aureus.

Recent isolates of methicillin-resistant Staphylococcus aureus from Australia and several other countries carry a plasmid coding for high levels of resistance to propamidine isethionate and low levels of resistance to cetyltrimethyl-ammonium bromide. The reasons for the acquisition and retention of such a determinant are not known. To define the properties of this resistance determinant in more detail, the minimum inhibitory concentrations of a series of cationic agents, including ethidium bromide, were determined and a cationic-resistance profile prepared for several strains of S. aureus and their isogenic, sensitive derivatives. The compounds for which resistance is coded by this determinant all bind to nucleic acids. Hence the determinant has been designated the NAB (nucleic acid-binding compounds)-resistance determinant.

Amidines↗
PubMed1985

Transfer of plasmid-borne aminoglycoside-resistance determinants in staphylococci.

Aminoglycoside-resistance determinants in staphylococci are borne on conjugative and non-conjugative plasmids. The conjugative plasmids were found in methicillin-resistant strains of Staphylococcus aureus isolated recently in Darwin and Sydney, Australia and in Houston, Texas, USA. These plasmids and the class-2 conjugative plasmid reported by Archer and Johnston (1983) had similar patterns of EcoR1 restriction-endonuclease fragments, encoded resistance to gentamicin, kanamycin and neomycin, transferred to a non-lysogenic recipient in conditions that promoted close cell-to-cell contact and mobilised a small, non-conjugative plasmid. A further plasmid, pWG14, encoding resistance to kanamycin, neomycin, streptomycin, erythromycin and lincomycin, also displayed conjugative properties but did not mobilise the small, non-conjugative plasmid. The transfer frequency of all conjugative plasmids was stimulated by the addition of polyethylene glycol, particularly at concentrations above 20%, to mixtures of donor and recipient broth cultures. Polyethylene glycol appeared to promote close cell-to-cell contact between donor and recipient cells. A representative of the most common aminoglycoside-resistance plasmids in Australian isolates of methicillin-resistant S. aureus was non-conjugative and transferred by a bacteriophage-mediated system to a lysogenic recipient. With the exception of plasmid pWG14, the conjugative plasmids were also transferred by a bacteriophage-mediated system. Furthermore, cultural conditions that favoured conjugative transfer of plasmids inhibited bacteriophage-mediated transfer and vice versa. The efficacy of the two transfer systems for analysing the plasmids of gentamicin-resistant, methicillin-resistant isolates of S. aureus has been compared.

Aminoglycosides↗