Colonial variation in Serratia marcescens together with antibiotic resistance

A strain of Serratia marcescens, isolated from the blood cultures of a patient receiving antibiotics, exhibited 3 unstable properties. These properties were resistance to aminoglycosides, colony size and pigment production. While resistance to aminoglycosides was linked to colony size, pigment production appeared independent of the other 2 properties. When multiple variation of properties occurs in colonies isolated from clinical material, this still may represent a pure culture.