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Biomedical subjects

D I Annear

Publications and source records attributed to D I Annear.

At least 19 recordsLinked to original sources
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↗
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

Control of methicillin-resistant Staphylococcus aureus (MRSA) in an Australian metropolitan teaching hospital complex.

In April 1982, a patient infected with methicillin-resistant Staphylococcus aureus (MRSA) was transferred to the Royal Perth Hospital from the Royal Darwin Hospital. Within three months, 19 patients and four staff members had become infected or colonized with MRSA. The outbreak was terminated only after all colonized inpatients were transferred to a separate isolation unit. After the outbreak, all new patients and new employees who had been in hospitals outside Western Australia in the previous 12 months were screened. From June 1, 1982, to June 30, 1984, 28 of the 649 patients (4.3%) screened on admission to the Royal Perth Hospital were found to be harbouring MRSA. During the same period only one of the 468 persons (0.2%) screened on application for employment at the Hospital was found to be colonized with MRSA. Since the policy of screening new patients and staff from hospitals outside Western Australia was introduced, no serious outbreak of MRSA has occurred.

Adolescent↗
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↗
PubMed1984

Genetic analysis of methicillin-resistant Staphylococcus aureus from a Western Australian hospital.

The isolates from an outbreak of methicillin-resistant Staphylococcus aureus (MRSA) at Royal Perth Hospital (RPH) during a 3 month period in 1982 have been compared genetically with MRSAs isolated at the same hospital during 1969-1973. The 1982 isolates are genetically similar to isolates from eastern Australia and appear to have been introduced by a patient transferred from a hospital in another Australian state. Methicillin-resistant Staph. aureus isolated during 1969-1973 were genetically distinguishable from the 1982 isolates but were similar to strains reported from elsewhere in the world during these years. This indicates that the MRSA strains currently prevalent in Australia are either a new type or are related to previous MRSAs but have undergone considerable genetic change. These results give further support to suggestions that the strains of MRSA currently being isolated in Australian hospitals have special properties which have facilitated their spread.

Australia↗
PubMed1978

Interaction between erythromycin and lincomycin in Streptococcus pyogenes.

Ten strains of Streptococcus pyogenes isolated were moderately resistant to erythromycin and highly but paradoxically resistant to lincomycin, and they showed antagonism between the two antibiotics. Another strain was moderately resistant to erythromycin and sensitive to lincomycin, and it showed synergism between the two antibodies.

Dose-Response Relationship, Drug↗
PubMed1976

Loss of resistance to methicillin and other antibiotics in Staphylococcus aureus associated with a chronic empyema.

A chronic empyema was investigated in a patient during a period of seven years. A strain of Staphylococcus aureus resistant to methicillin and four other antibiotics was isolated and the loss of all these determinants was shown to occur in vitro. A similarly sensitive organism was obtained directly from the patient during the later stages of his illness and the homogeneity of the phage patterns indicate that the organism was a true variant which evolved from the highly resistant one.

Anti-Bacterial Agents↗