Organisms that are either present in very low numbers, or that possess a characteristically slow growth rate, may require an extended incubation before they are detected in culture. Amplification and/or detection of unique sequences of either DNA or RNA provide for a more timely identification. This is true whether they are applied to the specimen for direct detection, or in some cases, to culture positive specimens for culture confirmation/identification.
Even for organisms that are easy to recover and identify (example: Staphylococcus aureus) various molecular methods offer the ability for either direct detection in clinical material, or more rapid identification that would greatly aid in treatment and/or clinical management decisions.