Unstable gentamicin resistance with linkage to colony size in Pseudomonas aeruginosa.

Three strains of Pseudomonas aeruginosa have shown unstable resistance to gentamicin and a firm linkage between this property and the size of colonies produced on nutrient agar. The resistant parent cells yield distinctly smaller colonies than the sensitive variants. As a point of clinical interest, the smaller colonies may be obscured by the larger and the detection of gentamicin resistance compromised.