...right for appropriate antibiotic concentrations. Antibiotic Concentrations Antibiotic Recommended Stock Concentration...to be resistant to the antibiotic. On the second plate, streak out a strain that’s not resistant to the... be resistant to the antibiotic, (+) indicates that the tested strain is supposed to be resistant to the...that: The antibiotic broke down. You forgot to add the antibiotic. You added the antibiotic at too low... any antibiotic. Negative Result 3: Only the Non-resistant Strain Grows If only the non-resistant strain...one or more antibiotic resistance genes, which confer resistance to a specific antibiotic to the bacteria...resistance to that antibiotic - usually conferred by a plasmid carrying the antibiotic resistance gene. ...