Mupirocin-resistant methicillin-resistant Staphylococcus aureus in Western Australia.
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Drug Resistance, Microbial↗
Biomedical subjects
W B Grubb
Publications and source records attributed to W B Grubb.
Emergence of high-level mupirocin resistance in methicillin-resistant Staphylococcus aureus in Western Australia.
Six mupirocin-resistant Staphylococcus aureus were isolated from patients living in the northern part of Western Australia (WA). They were all resistant to methicillin, tetracycline, trimethoprim and cadmium and harboured similar 41.4 kb plasmids. Transfer and curing experiments with one of the isolates, WBG7569, demonstrated that the 41.4 kb plasmid encoded resistance to mupirocin, tetracycline, trimethoprim and cadmium. The isolates were compared by pulsed-field gel electrophoresis with methicillin-resistant S. aureus (MRSA) previously isolated from the Kimberley region in the northern-most part of WA (WA MRSA). The mupirocin-resistant isolates were found to be closely related to WA MRSA suggesting that they were WA MRSA which had acquired a new multiple-resistance plasmid encoding high-level mupirocin resistance.
Cadmium↗
Strongyloides ratti: fumarate reductase and succinate dehydrogenase activities of infective larvae.
Submitochondrial particles prepared from axenised infective (L3) larvae of S. ratti (homogonic-strain) were assayed spectrophotometrically for fumarate reductase (FR) and succinate dehydrogenase (SDH) and their kinetic properties characterised. The S. ratti FR (pH 8.2; 37 degrees C) exhibited a maximum specific activity of 3.45 nmol (min)-1 (mg protein)-1 at a sodium fumarate concentration of 0.3 mM. Interestingly, the FR activity declined at fumarate concentrations greater than 0.3 mM. The mechanism of this unusual inhibitory effect requires further study. The S. ratti SDH (pH 8.2; 37 degrees C) showed a Vmax of 17.4 nmol (min)-1 (mg protein)-1; the Kmsucc was 0.5 mM. Although the SDH:FR ratio cannot predicate vectorial electron flow as would occur in vivo, an in vitro ratio of 5.04:1 was observed for SMPs derived from S. ratti L3 larvae.
Animals↗
An alternative protocol for the serial passage and maintenance of a homogonic strain of Strongyloides ratti in female Sprague-Dawley rats.
A method which does not involve the tedious use of watch glass coprocultures for obtaining filariform infective (L3) larvae of Strongyloides ratti from faecal pellets of infected Sprague-Dawley rats is described. The alternative method utilises Baermannization (18 h) of faecal pellets to yield rhabditiform (L1) larvae of S. ratti and their subsequent culture for 72 h at 19 degrees C in tissue-culture-flasks containing only dechlorinated tap water to yield infective filariform (L3) larvae. The yields and infectivity of the L3 larvae obtained from the two methods were essentially similar.
Animals↗
The efficacy of two electron transport inhibitors (720C80 and 993C76) on murine strongyloidiasis: a comparison with albendazole.
The clinical efficacy of albendazole (ABZ) in the treatment of chronic uncomplicated strongyloidiasis has been reported to be highly variable. In our murine model of strongyloidiasis a single oral dose of 5 and 10 mg kg-1 ABZ reduced (at day 4 post infection) the faecal larval count (FLC) by 54.2 +/- 12.5% and 81.5 +/- 10.2%, respectively. 100 mg kg-1 ABZ reduced the FLC by 100%. Two inhibitors of protozoan and filarial electron transport (720C80 and 993C76) inhibited the endogenous O2 consumption of intact infective (L3) larvae of S. ratti by > 50% at 2 x 10(-5) M in vitro, and reduced the FLC by 72 +/- 9.3% and 62.0 +/- 10.3% respectively in vivo, at a dose of 70 mg kg-1. These results suggest that compounds designed as selective inhibitors of protozoan electron transport have significant efficacy against murine strongyloidiasis and may prove useful in the management of human strongyloidiasis.
Albendazole↗
Genetic analysis of community isolates of methicillin-resistant Staphylococcus aureus in Western Australia.
Methicillin-resistant Staphylococcus aureus (MRSA) obtained from patients who had not been hospitalized outside Western Australia (WA) were studied for antimicrobial resistance and plasmid content and by pulsed-field gel electrophoresis. They were found to be of several types, none of which appeared to be related to MRSA which have been previously studied. It appears that new MRSA strains have emerged in communities in the far north of WA and are being isolated at an increasing frequency in Perth hospitals 2000 km south.
Bacterial Typing Techniques↗
Genetic analysis of methicillin-resistant Staphylococcus aureus from a Nigerian hospital.
Methicillin-resistant strains of Staphylococcus aureus isolated during 1985 and 1987 at a Nigerian hospital were compared by resistance profiles, plasmid analysis, and pulsed-field gel electrophoresis of chromosomal DNA. The results indicated that the isolates from the two periods were unrelated with regard to all three aspects. None of the isolates was similar to the classical MRSA nor to the epidemic MRSA of Australia or the UK. The MRSA isolated in 1985 had a similar plasmid to MRSA isolates from Singapore, but differed from them when compared by pulsed-field gel electrophoresis.
Conjugation, Genetic↗
Typing of methicillin-resistant Staphylococcus aureus with IS256.
A simple one-step procedure is described for specifically amplifying and labelling insertion element IS256 which is associated with the gentamicin-resistance transposon Tn4001. The product has been used to probe DNA digests of methicillin-resistant Staphylococcus aureus. The resulting restriction fragment length polymorphisms were found to be able to distinguish isolates which were indistinguishable by other typing methods. The probe also hybridised with methicillin-resistant Staphylococcus aureus which were isolated before the emergence of gentamicin resistance, demonstrating its usefulness in typing species other than those that are gentamicin-resistant.
Bacterial Typing Techniques↗
Conjugative trimethoprim resistance in Staphylococcus aureus.
A multiply resistant Staphylococcus aureus isolate, WBG7410, harbours plasmids of 38, 26, 2.8, 2.4 and 1.9 kb and transfers trimethoprim and kanamycin resistance at high frequencies by conjugation. The transconjugants contained the 38-kb plasmid, pWBG707, and the 2.8-kb plasmid. Plasmid pWBG707 was shown to encode trimethoprim resistance, was conjugative and mobilised at high frequencies the 2.8-kb plasmid which presumably encodes kanamycin resistance. Plasmid pWBG707 was isolated mostly in the open circular form and analysis with EcoRI restriction endonuclease suggests that pWBG707 is a new conjugative plasmid distinct from the other conjugative plasmids reported in S. aureus.
Conjugation, Genetic↗
Difference spectroscopic characterisation of the cytochrome complement in Acanthocheilonema viteae.
(Dithionite-reduced) minus (ferricyanide-oxidised) difference spectra of 600 x g and 12,000 x g subcellular pellet fractions of adult male Acanthocheilonema viteae exhibited alpha-absorption maxima (296 K) attributable to Cyt c555, Cyt b562 and aa3 (600-605 nm). The gamma(Soret) maximum of both fractions was evident at 427 nm, with a shoulder at 432-434 nm. 600 x g and 12,000 x g pellet fractions of adult female and mixed-sex adult A. viteae exhibited similar absorption maxima. (Succinate-reduced)--(ferricyanide-oxidised) difference spectra of the 12,000 x g pellet fraction of mixed-sex adult A. viteae showed absorption maxima at 555 and 562 nm, 600 and 630 nm, suggesting the reduction of Cyt c555, Cyt b562, Cyt aa3 (600 nm) and an unidentified species (630 nm peak) Antimycin A (10(-6) M) induced the disappearance of the maxima at 555, 600 and 630 nm corresponding to Cyt c555, Cyt aa3 and the unidentified species; the maximum at 562 nm prevailed in the presence of antimycin A. These antimycin A induced changes can be cited as classical evidence for the functional involvement of these a, b and c type cytochromes in respiratory electron transport. (Dithionite reduced + CO)--(dithionite reduced) difference spectra suggest that adult A. viteae may have one or more CO-binding-species, one of which appears to be a low-spin-haemoprotein with a b-type or c-type haem, which has essentially an electron carrier function rather than a ligand binding function.
Animals↗
Typing of methicillin-resistant Staphylococcus aureus with an M13 repeat probe.
A bacteriophage M13 tandem repeat has been used to probe EcoRI digested genomic DNA of methicillin-resistant Staphylococcus aureus (MRSA). The patterns generated were found to be useful in typing MRSA and generally confirmed the relationships that had previously been recognized in other studies based on antimicrobial resistance and plasmid profiles. The epidemic MRSA of London hospitals (EMRSA) and the majority of the epidemic MRSA of eastern Australian hospitals (EA MRSA) gave the same pattern. However, two isolates previously classified as EA MRSA gave a different pattern and a third another pattern. One isolate from Dublin, two isolates from Nuneaton and two isolates from Singapore gave the same pattern as the two EA MRSA. With the exception of the early or classic MRSA all the other isolates examined gave their own distinctive patterns. With one exception the classic MRSA belonged to a separate group. The exception was of particular interest because it gave the same pattern as the majority of the EA MRSA. This suggests that there may be an evolutionary relationship between some of the classic MRSA and the EMRSA of London and the EA MRSA of Australia.
Bacterial Typing Techniques↗
Use of contour-clamped homogeneous electric field (CHEF) electrophoresis to type methicillin-resistant Staphylococcus aureus.
Strains of methicillin-resistant Staphylococcus aureus (MRSA) from Australia and the UK were compared by digesting their chromosomal DNA with the low-frequency-cutting restriction enzyme SmaI and separating the restriction fragment length polymorphisms (RFLPs) by contour-clamped homogeneous electric field (CHEF) electrophoresis. The numbers of restriction fragments produced were in the range 14-17 and the sizes of the bands were 7-700 kb. Generally, the results confirmed previous conclusions based on antimicrobial resistance and plasmid profiles. The earlier MRSA isolates were different from more recent isolates, and the epidemic MRSA from eastern Australia (EA MRSA) was the same as the epidemic MRSA (EMRSA) found in London hospitals. However, contrary to previous results, the EA MRSA did not constitute a homogeneous group. The results showed that comparison of RFLPs by CHEF electrophoresis is a useful technique for studying the epidemiology of MRSA.
Australia↗
Intra- and inter-species mobilisation of non-conjugative plasmids in staphylococci.
The ability of Staphylococcus aureus conjugative plasmids to mobilise non-conjugative resistance plasmids from clinical isolates of S. aureus and S. epidermidis was studied. Plasmids which could not be transferred by transduction or mixed-culture transfer were transferred from phage-typable and non-typable S. aureus and from S. epidermidis. Plasmids encoding single resistance determinants were transferred by mobilisation whereas multiple-resistance plasmids were transferred as co-integrates between the conjugative and non-conjugative plasmids. This study demonstrates that mobilisation is a useful tool for the transfer and study of staphylococcal plasmids and illustrates how antibiotic resistance could be transferred between staphylococci in vivo.
Anti-Bacterial Agents↗
Typing of Australian methicillin-resistant Staphylococcus aureus strains by pulsed field gel electrophoresis.
Twenty-six clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) collected from six Australian hospitals by a National Staphylococcal Study Group were examined by analysis of restriction fragment length polymorphisms (RFLPs) of chromosomal DNA with pulsed field gel electrophoresis. Digestion with the restriction endonuclease SmaI produced 13-17 bands of 7-700 kb. The digestion patterns were easily distinguished and isolates could be classified into 17 groups based on their RFLPs. Isolates giving a pattern associated with one group were from four hospitals in four different states. In another group, the isolates responsible were from three hospitals in two states and in a further group, the isolates were derived from two hospitals in different states. The remaining groups comprised only one member each. The method has promise for typing and studying the epidemiology of MRSA.
Australia↗
The response of intact Strongyloides ratti infective (L3) larvae to substrates and inhibitors of respiratory electron transport.
Live, intact third-stage larvae (L3s) of Strongyloides ratti in the absence of exogenous substrates consumed oxygen at a rate (E-QO2) of 181.8 +/- 12.4 ng atoms min-1 mg dry weight-1 at 35 degrees C. Respiratory electron transport (RET) Complex I inhibitor rotenone (2 microM) produced 33 +/- 6.5% inhibition of the E-QO2. Unusually the rotenone-induced inhibition was not relieved by 5 mM-succinate. The E-QO2 of intact L3s was refractory to RET Complex III inhibitor antimycin A at 2 microM; 4 microM-antimycin inhibited less than or equal to 10% of the E-QO2. The electron donor couple ascorbate/TMPD augmented the E-QO2 in the presence of rotenone (2 microM) and antimycin A (4 microM) by 110%. Azide (1 mM) stimulated the antimycin A refractory QO2 by 36.6 +/- 7.2% which was only partially inhibited by 1.0 mM-KCN (IC50 = 0.8 mM). The data suggest the presence of classical (CPW) and alternate (APW) electron transport pathways in S. ratti L3s.
Animals↗
A new incompatibility group plasmid in Staphylococcus aureus.
The conjugative plasmid pWBG637 and its derivatives, pWBG636 and pWBG642, were tested for incompatibility against conjugative and non-conjugative plasmids in Staphylococcus aureus. They were compatible with other conjugative plasmids and plasmids of the 14 established incompatibility groups. They therefore define a new Incompatibility group 15.
Conjugation, Genetic↗
Transposition of genes encoding kanamycin, neomycin and streptomycin resistance in Staphylococcus aureus.
The determinants encoding resistance to kanamycin, neomycin and streptomycin on plasmid pWBG628 have been shown to undergo recombination independent transposition to the chromosome of Staphylococcus aureus. Transposition of the determinants to a target plasmid corresponded to transfer of a 4.5 kb element which has been designated Tn3854.
DNA Transposable Elements↗
Transfer of resistance determinants from a multi-resistant Staphylococcus aureus isolate.
The clinical isolate Staphylococcus aureus WBG1024 was resistant to cadmium, benzyl penicillin, kanamycin, neomycin, streptomycin, tetracycline and trimethoprim and harboured a conjugative plasmid pWBG637 (34.5 kb) and non-conjugative plasmids of 23.8, 4.4, 2.8 and 1.9 kb. Transduction and mixed-culture transfer experiments demonstrated that the 4.4-kb plasmid (pWBG632) encoded resistance to tetracycline and the 23.8-kb plasmid (pWBG628) encoded resistance to cadmium, benzyl penicillin, kanamycin, neomycin and streptomycin. The conjugative plasmid pWBG637 was able to mobilise a further 4.4-kb plasmid (pWBG633) encoding streptomycin resistance and recombined with the multiresistance plasmid pWBG628 to produce transconjugantes of various resistance phenotypes.
Blotting, Southern↗