Final answer:
To determine the causative agent of an infection, a skin swab culture or blood culture is commonly used, depending on the infection's location. For viruses, EIA, RT-PCR, and PCR are suitable tests. In the case of suspected staphylococcal infections, samples from the wound are cultured and observed under a microscope or grown on blood agar.
Step-by-step explanation:
To determine the causative agent of an infection, different types of diagnostic tests can be used. If the suspected infection is on the skin, a skin swab culture is typically employed to collect cells or fluids for analysis. In the case of systemic infections or those involving the bloodstream, a blood culture would be indicated as it can detect presence of bacteria, fungi, or other microorganisms in the blood. For specific viruses, tests such as Enzyme ImmunoAssay (EIA), Reverse Transcription Polymerase Chain Reaction (RT-PCR), and Polymerase Chain Reaction (PCR) can detect the presence of a specific virus, with PCR being a particularly sensitive and widely-used method.
In the context of a suspected staphylococcal skin infection, culturing samples from the wound to observe the characteristic grapelike clusters of Staphylococcus under a microscope or growth on blood agar can be diagnostic. Additionally, a catalase test differentiates between Staphylococcus and Streptococcus, as the former is catalase-positive. When it comes to determining the minimum inhibitory concentration (MIC) of an antimicrobial drug, techniques like the Etest can be used, although some methods cannot be employed for this purpose. For example, direct fluorescent antibody tests are more suited for identifying bacteria in a sample using fluorescently-labeled monoclonal antibodies (mAb).