1887

Abstract

The accessory gene regulator () of is a global regulator of the staphylococcal virulon, which includes secreted virulence factors and surface proteins. The locus is important for virulence in a variety of animal models of infection, and has been assumed by inference to have a major role in human infection. Although most human clinical isolates are , there have been several reports of -defective mutants isolated from infected patients. Since it is well known that the locus is genetically labile , we have addressed the question of whether the reported -defective mutants were involved in the infection or could have arisen during post-isolation handling. We obtained a series of new staphylococcal isolates from local clinical infections and handled these with special care to avoid post-isolation mutations. Among these isolates, we found a number of strains with non-haemolytic phenotypes owing to mutations in the locus, and others with mutations elsewhere. We have also obtained isolates in which the population was continuously heterogeneous with respect to functionality, with and variants having otherwise indistinguishable chromosomal backgrounds. This finding suggested that the variants arose by mutation during the course of the infection. Our results indicate that while most clinical isolates are haemolytic and , non-haemolytic and strains are found in infections, and that and variants may have a cooperative interaction in certain types of infections.

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2008-08-01
2020-04-03
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