Repair of Global Regulators inStaphylococcus aureus8325 and Comparative Analysis with Other Clinical Isolates

Abstract

The pathogenicity of Staphylococcus aureus strains varies tremendously (as seen with animals). It is largely dependent on global regulators, which control the production of toxins, virulence, and fitness factors. Despite the vast knowledge of staphylococcal molecular genetics, there is still widespread dispute over what factors must come together to make a strain highly virulent. S. aureus NCTC8325 (RN1 and derivatives) is a widely used model strain for which an incomparable wealth of knowledge has accumulated in the almost 50 years since its isolation. Although RN1 has functional agr, sarA, and sae global regulators, it is defective in two regulatory genes, rsbU (a positive activator of SigB) and tcaR (an activator of protein A transcription), and is therefore considered by many to be a poor model for studies of regulation and virulence. Here, we repaired these genes and compared the resulting RN1 derivatives with other widely used strains, Newman, USA300, UAMS-1, and COL, plus the parental RN1, with respect to growth, extracellular protein pattern, hemolytic activity, protein A production, pigmentation, biofilm formation, and mouse lethality. The tcaR-repaired strain, showed little alteration in these properties. However, the rsbU-repaired strain was profoundly altered. Hemolytic activity was largely decreased, the exoprotein pattern became much more similar to that of typical wild-type (wt) S. aureus, and there was a surprising increase in mouse lethality. We note that each of the strains tested has a mutational alteration in one or more other regulatory functions, and we conclude that the repaired RN1 is a good model strain for studies of staphylococcal regulation and pathobiology; although strain Newman has been used extensively for such studies in recent years, it has a missense mutation in saeS, the histidine kinase component of the sae signaling module, which profoundly alters its regulatory phenotype. If this mutation were repaired, Newman would be considerably improved as a model strain.As a classical, dangerous, and universal human pathogen, Staphylococcus aureus has aroused continuing interest in its epidemiology, pathogenesis, and antibiotic resistance and other features of its pathobiology. This interest has led, concomitantly with the development of bacterial molecular biology, to the development of a model strain for the analysis of staphylococcal molecular genetics in relation to the pathogenicity of the organism. This strain, NCTC8325, was isolated in 1960 from a sepsis patient and utilized as the propagating strain for phage 47 of the international phage typing system. It was originally chosen for research owing to its sensitivity to all known antibiotics and was initially used primarily for studies of antibiotic resistance transfer and carriage by plasmids (32). It is designated RN1 in the Novick lab strain collection and is presently maintained by the Central Public Health Laboratory, Colindale, London, United Kingdom, by the ATCC and by the recently established Network on Antimicrobial Resi...

Hypoxic regulation of neutrophil function and consequences for Staphylococcus aureus infection

“…For example, S. aureus strain NCTC8325, isolated from a historic sepsis patient and now maintained as the laboratory strain RN1, is fully antibiotic sensitive and also defective in two regulatory genes, one of which encodes a transcription activator of virulence factor protein A. In comparison, USA300 is a virulent community-acquired MRSA clinical isolate with high haemolytic activity and leukotoxin secretion [82]. Hence, it is conceivable that variations between strains used experimentally may underlie some of the conflicting results.…”

Pathogen-Triggered Activation of Plasmacytoid Dendritic Cells Induces IL-10–Producing B Cells in Response to Staphylococcus aureus

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Genome-wide screen for genes involved in eDNA release during biofilm formation by Staphylococcus aureus

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