Abstract
The present invention provides a method of detecting production of antibiotic-inactivating factor and for determining the antibiotic susceptibility of a microorganism comprising the following steps, a culture of the microorganism suspected of producing inactivating factors and/or whose susceptibility is to be determined is admixed with an antibiotic to which susceptibility is to be assayed, and a permeabilizing agent for the microorganism present in a non-growth-inhibiting micro- organism-permeabilizing effective amount to form an assay culture. The assay culture is incubated under appropriate culture conditions and for a time sufficient to determine production of antibiotic-inactivating factors and/or the susceptibility of the microorganism to the antibiotic. In another aspect, the present invention provides an improved method for antibiotic susceptibility testing of a microorganism in a culture by admixing the culture with an antibiotic to which susceptibility is to be assayed, and incubating the culture for a time sufficient to determine the susceptibility of the microorganism to the antibiotic, the improvement comprising admixing the culture with a permeabilizing agent for the microorganism present in a non-growth inhibiting microor- ganism-permeabilizing effective amount.