The Influence of Antibiotics on the Origin of Small Colonies (G Variants), of Micrococcus Pyogenes var. Aureus1

Two forms of Staphylococcus aureus in blood of patients with staphylococcal sepsis

“…Further support for the concept that our patients were infected by two forms of the same infecting organism comes from the observation that in case 2, on three instances, hemolytic colonies appeared during prolonged incubation of the nonhemolytic form; these new hemolytic isolates were indistinguishable from the original hemolytic isolates based on phage typing and other properties, and remained stable during many subsequent generations of subculture. One feature of case 1 not entirely consistent with previous observations on variant forms of S. aureus was that both hemolytic and nonhemolytic isolates were equally susceptible to aminoglycosides (9,10,14,15).…”

“…(iii) The two stable isolates of S. aureus represented two forms of a single, initially infecting organism. In case 1, the nonhemolytic form resembled a variant of S. aureus, with the hemolytic form representing a typical S. aureus (parent) from which the variant was derived (9,15). Variant forms of S. aureus have been shown to have phage types that differ from the parent and from each other (9,12).…”

“…In the second case neither isolate appeared entirely typical, the hemolytic organism growing to a smaller size than the nonhemolytic one and both lacking alpha hemolysin. Several such variants frequently result from exposing a single S. aureus to a variety of stresses, including fatty acids and aminoglycosides, or from aging (6,8,9,12,14,15). In fact, two different phage types were represented among the nonhemolytic colonies from case 1, suggesting that this same kind of selection may occur in vivo.…”

Characterization of Gentamicin‐Resistant Respiratory‐Deficient (Res−) Variant Strains of Staphylococcus aureus

“…The recovery of dwarf or small colony variants of Staphylococcus aureus has been reported by a number of workers in the past (see 14,15,21,45, for reviews) . These variants were initially distinguished as (a) those which maintained the minute colony phenotype only in the presence of the selective agent (38) and (b) strains which were stable in the absence of the selective agent.…”

A site-directed Staphylococcus aureus hemB mutant is a small-colony variant which persists intracellularly

“…aureus SCVs were first described Ͼ80 years ago, and a number of studies support a pathogenic role for SCVs in diseases (1,2,31,34,38,40,41,47,50). Although S. aureus SCVs have been recognized for many years, the connection of this phenotype to persistent and recurrent infections has only recently been appreciated (36).…”