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Abstract
Of 74 distinct strains of Staphylococcus aureus obtained from clinical sources, about 70 per cent. were resistant to high levels of streptomycin (MIC>1 mg per ml) and 30 per cent. resistant to lower levels (MIC about 100 μg per ml).
Streptomycin resistance in four strains exhibiting high-level resistance was stable on storage, whilst that in four strains with low-level resistance was unstable. Three of the latter were also resistant to other antibiotics; these resistances were also unstable, and in one of these strains (FAR4) there was evidence that streptomycin resistance was linked to erythromycin and neomycin resistance and to production of δ-haemolysin.
Strain 649 is resistant only to streptomycin (low-level resistance); plasmid DNA with a molecular weight of about 38 million daltons corresponding to this resistance was isolated from this strain. Attempts to correlate the CCC-DNA from the multi-resistant strain FAR4 with its resistances were unsuccessful.
Resistance to spectinomycin was not associated with resistance to streptomycin, but with erythromycin resistance or with neomycin resistance.
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