Probable chromosomal mutation to resistance to all aminoglycosides in Staphylococcus aureus selected by the therapeutic use of gentamicin: a preliminary report

A patient suffering from burns was treated with gentamicin: subsequently, a 'methicillin-resistant' strain of Staphylococcus aureus (B27), was isolated which was highly resistant to this antibiotic and all other aminoglycosides. In all other respects this isolate resembled the gentamicin-sensitive 'methicillin-resistant' S. aureus prevalent on the Yorkshire Regional Burns Unit. Subsequently, fusidic acid treatment was substituted for gentamicin therapy, and a fusidic acid-resistant variant was isolated from the same patient. This article reports a preliminary characterization of these isolates.

Plasmid fusions mediated by one end of TnA

We have observed plasmid fusions in a recA background mediated by a single end of TnA. These occur when transposase is provided either in cis or in trans. Insertions of the plasmid carrying the TnA inverted repeat sequence occur at many sites in the target plasmid. The point of fusion on the plasmid carrying TnA sequences always appears to be located in the region which carries the TnA inverted repeat sequence. In contrast to the transposition of an intact TnA element, plasmid fusions mediated by one end of TnA are very rare events. The implications of our results for models of transposition are discussed.

The role of TnA transposase in transposition immunity

The strength of expression of transposition immunity depends on the level of transposase available in the system, and on the location of the element to be transposed.

Persistence of DNA sequences of BK virus and JC virus in normal human tissues and in diseased tissues

Available evidence suggests that BK virus (BKV) and JC virus (JCV) persist in the kidneys of healthy individuals after primary infection and may reactivate when the host's immune response is impaired. Data supporting this hypothesis are presented. A previous study had shown BKV to be present in the kidneys of eight (57%) of 14 subjects. In the present study, which extended the investigation to a total of 30 subjects, BKV DNA was found in the renal tissues of 10 (33%) subjects, and JCV DNA was found in the renal tissues of three (10%) subjects. The viral DNA detected appeared not to be integrated with host DNA and to be isolated in foci. Investigation of normal and diseased brain tissue, including tissue from six subjects with multiple sclerosis, failed to reveal the presence of either JCV DNA or BKV DNA.

The persistence of papovavirus BK DNA sequences in normal human renal tissue

Evidence has accumulated indicating that BK virus, following an inapparent primary infection, persists in the renal organs of normal healthy individuals and reactivates upon immunosuppression. Data to support this hypothesis are presented and suggest that BK virus DNA sequences are present at very low levels in the kidneys of more than 50% of the population and that this persistence is localized in several foci within these organs.

Nonrandom segregation of nucleolar organizing chromosomes at mitosis?

The random assortment of non-homologous chromosomes at meiosis is one of the fundamental tenets of genetics, to which few exceptions have been documented. The segregation of mitotic chromatids is believed to be similarly random. We report here that we seem to have discovered a new exception to this rule, in that nucleolar organizing chromosomes remain associated with one another, held in the same lateral orientation, for several mitotic cycles.