Genetic Manipulation of S. aureus Strains

The S. aureus strains tested in the murine gastrointestinal colonization model are listed in Table 3; each was resistant to Sm. Mutations in the S. aureus ica locus, spa, and atl were moved into Sm-resistant Newman by transduction with phage 80α or phage 85 from the original antibiotic marked mutant strains [42 (link)–44 (link)]. The tagO::tet mutation was moved from S. aureus RN4220 into Newman Δatl as described previously [22 (link)]. Mutants were confirmed by PCR or Southern blot analysis and were phenotypically identical to the parental strains in terms of the growth rate, hemolysis on sheep blood agar plates, and the metabolic profile on API Staph test strips (Biomerieux, Inc., Durham, NC). S. aureus strains were cultivated in TSB to the logarithmic growth phase, unless otherwise noted. Sm (0.5 mg/ml; Sigma Chemical Co., St. Louis, Mo.), erythromycin (Em; 5 μg/ml; Sigma), tetracycline (Tc; 2.5 μg/ml; Sigma), or spectinomycin (Spc; 100 μg/ml; MP Biomedicals, Solon, OH) was added to culture medium for selection where appropriate.