COMPARATIVE PHYSIOLOGY OF ANTIBIOTIC-RESISTANT STRAINS OF STAPHYLOCOCCUS AUREUS.

Brown, Ruby L. (North Carolina State College, Raleigh) and James B. Evans. Comparative physiology of antibiotic-resistant strains of Staphylococcus aureus. J. Bacteriol. 85:1409-1412. 1963.-A collection of antibiotic-resistant strains of Staphylococcus aureus isolated from clinical sources was studied with respect to nutritional requirements and common diagnostic tests. Contrary to numerous reports in the literature indicating changes in these characteristics in antibiotic-resistant mutants, the present cultures were typical members of the taxonomic species S. aureus. They were coagulase-positive, fermented both glucose and mannitol under anaerobic conditions, produced acetoin from glucose, grew and produced black colonies on tellurite glycine agar, required both thiamine and nicotinic acid, and did not require other vitamins or purines. It is suggested that in most instances these cultures from clinical sources represent spontaneous mutants having genetic changes limited largely to loci concerned with antibiotic resistance. Most reports of extensive changes in physiology and nutritive requirements by antibiotic-resistant strains of S. aureus are based on studies of resistant strains selected after exposing a large population of the parent sensitive strain to toxic levels of antibiotics, chemical mutagens, or irradiation. Such isolates may have widespread genetic damage at other loci in addition to those concerned with their antibiotic resistance.