Final answer:
A cotton swab is used in microbiological studies for inoculating plates with bacterial cultures, collecting skin samples, and antibiotic susceptibility testing.
Step-by-step explanation:
In microbiological studies, a cotton swab is often used to inoculate a plate when preparing bacterial cultures. The process involves soaking the sterile swab in a bacterial suspension, then spreading it across the surface of an agar plate to create a lawn of bacterial colonies.
This technique is common in both academic and clinical laboratories for the purpose of isolating and identifying bacteria or for testing the effectiveness of antibiotics, through standardized methods such as the Kirby-Bauer assay.
Specific scenarios for utilizing a cotton swab would be when collecting a skin sample for microbial cultures, or when performing susceptibility testing in which the swab is used to evenly spread bacteria on a plate before applying antibiotic-impregnated disks to measure the zone of inhibition.
Another instance is the initial inoculation of agar plates with a bacterial suspension to ensure a uniform distribution of bacteria before further culturing or serial dilution.
It is important that the swab is sterile and that aseptic techniques are used throughout the process to prevent contamination. For precise results, the inoculum may be standardized to a known concentration, such as a 0.5 McFarland standard, to achieve uniformity in bacterial cell count.