MRSA (methicillin-resistant Staphylococcus aureus) bacteria growing on an agar plate Paper tab infused with vancomycin. The surrounding area it has diffused into, killing off all bacteria in the area, is called the zone of inhibition. Rectangular S VRSA (vancomycin-resistant Staphylococcus aureus) bacteria growing on an agar plate Paper tab infused with vancomycin. Note that the zone of inhibition is much smaller, demonstrating that the bacteria can grow in the presence of the antibiotic.
Microscopic examination
The analysis of minute organisms, cellular organization of any biological structure, and composition of body fluids with the help of a microscope is known as microscopic examination. The magnification of specimens or samples under study helps in attaining a clearer picture of it.
Gram Staining
Named after Hans Christian Gram, a Danish bacteriologist, Gram stain is one of the most powerful staining techniques within microbiology. This technique was introduced in 1882 to identify pneumonia-causing organisms. The Gram staining technique uses crystal violet or methylene blue as primary staining colors to distinguish gram-positive from gram-negative organisms. Under a microscope, the gram-positive organisms appear purple-brown, retaining the primary color. Gram-negative organisms appear pink or red as they do not acquire the color of the primary stain.
Q1: What is the difference between MRSA and VRSA? Q2: Why is there a clear zone (the “zone of inhibition”) around the paper disk in the top dish but not in the bottom dish? Q3: Why is the lack of a clear zone around the paper disk in the bottom dish so alarming?
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