Induced Variations in a Penicillin-resistant Staphylococcus

Abstract

A coagulase-positive, phage-typable, mouse-virulent strain of Staphylococcus aureus, resistant to penicillin and streptomycin, was exposed to chloramphenicol for a sublethal time. Pairs of staphylococci were isolated by means of the de Fonbrune micromanipulator, held at 37[degree]C, and observed by phase-contrast microscopy. Variants showed reduced resistance to penicillin, loss of virulence, and loss or decrease in activities, suggesting that variants are the result of damage to the parent cell. It seems possible that spontaneous mutations are also the result of some similar cell disturbance.