Phase variation in meningococcal lipooligosaccharide biosynthesis genes.

Neisseria meningitidis expresses a range of lipooligosaccharide (LOS) structures, comprising of at least 13 immunotypes (ITs). Meningococcal LOS is subject to phase variation of its terminal structures allowing switching between ITs, which is proposed to have functional significance in disease. The objectives of this study were to investigate the repertoire of structures that can be expressed in clinical isolates, and to examine the role of phase-variable expression of LOS genes during invasive disease. Southern blotting was used to detect the presence of LOS biosynthetic genes in two collections of meningococci, a global set of strains previously assigned to lineages of greater or lesser virulence, and a collection of local clinical isolates which included paired throat and blood isolates from individual patients. Where the phase-variable genes lgtA, lgtC or lgtG were identified, they were amplified by PCR and the homopolymeric tracts, responsible for their phase-variable expression, were sequenced. The results revealed great potential for variation between alternate LOS structures in the isolates studied, with most strains capable of expressing several alternative terminal structures. The structures predicted to be currently expressed by the genotype of the strains agreed well with conventional immunotyping. No correlation was observed between the structural repertoire and virulence of the isolate. Based on the potential for LOS phase variation in the clinical collection and observations with the paired patient isolates, our data suggest that phase variation of LOS structures is not required for translocation between distinct compartments in the host.

Treatment of Staphylococcus aureus endocarditis using moxifloxacin.

The conventional treatment of staphylococcal endocarditis requires in-patient administration, is inconvenient, and is potentially toxic. Increasing experience with well-absorbed, well-tolerated and highly active agents such as the new quinolones has prompted interest in their use as therapeutic alternatives for the treatment of such infections. We describe a case of staphylococcal endocarditis which failed to respond to conventional therapy, but where the addition of moxifloxacin, an 8-methoxyquinolone, was curative.

Molecular analysis of the meningococcal LPS expression.

Lipopolysaccharide (LPS) is one of the major virulence factors of Neisseria meningitidis (1), with proposed roles in bacterial attachment to the host, invasion of host tissues, serum resistance, evasion of the host immune response, and the pathogenesis of sepsis syndrome. Accordingly it has become an important target for research.

Investigation of gaseous ozone for MRSA decontamination of hospital side-rooms.

A domestic, gaseous ozone generator was investigated for use in the decontamination of hospital side-rooms that have housed patients colonized with methicillin-resistant Staphylococcus aureus (MRSA). Three models of bacterial contamination were used. These were exposed to ozone generation in a standard hospital side-room for 4 and 7 h. A methicillin-sensitive and a methicillin-resistant strain of S. aureus were compared. Ozone concentrations of 0.14 ppm were reached, levels which are sufficient to cause mild pulmonary toxicity. Bacterial counts were reduced in the vicinity of the gas generator in most instances, but the effect elsewhere in the room was, at best, limited. MRSA appeared more resistant to the effects of ozone than methicillin-sensitive S. aureus. We conclude that the device tested would be inadequate for the decontamination of such hospital side-rooms.