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Staphylococcus aureus infection is a severe pathological condition which not only affects the infected organ but extensive antimicrobial therapy used to treat such an infection also produces detrimental effects on overall health of the infected individual There are disparate pathophysiological mechanisms associated with acute and chronic S aureus infection The acute infection is associated with more aggressive and invasive phenotype whereas the chronic infection is associated with less aggressive and mild inflammatory phenotype characterised by small colony variants SCV There are several regulatory factors which play a crucial role in such a dynamic shift in S aureus phenotype from a greater inflammatory and shorter intracellular persistence associated acute phase to a less cytotoxic and longer intracellular persistence associated chronic phase The study aimed at finding the specific role of such essential factors i e agr sig B sarA in dynamic switching of bacterial phenotype in acute and chronic S aureus infection To identify the role of these regulating factors in acute and chronic infection the investigators designed different mutant models single double triple mutant and studied the virulence of wild and mutant strains in different in vivo and in vitro infection models Wild type and mutant strains of S aureus LS1 and SH1000 were used for all the experiments under the study Mutant strains of agr Sig B sarA were generated by transduction of antibiotic resistant cassettes i e RN6911 IK181 and ALC136 respe using different phages i e 11 80 85 respe Wild type and mutant strains were grown stepwise i e wild type and single mutants were grown in first step whereas double and triple mutants were grown in second step the protein fraction were extracted sequentially
