What instruments are used to perform sterile transfer from one medium to another
Loop & needle
Loop & syringe
needle & syringe
all above are true
The Correct Answer is A
A. Loop & needle: In microbiology, a sterile inoculating loop or needle is commonly used to transfer microorganisms from one culture medium to another while maintaining aseptic technique. Loops are typically used for streaking or spreading bacteria on agar, while needles are used for stabbing into agar or transferring small amounts of culture into broth, allowing precise and sterile handling.
B. Loop & syringe: Syringes are generally not used for routine transfer of microbial cultures between media because they increase the risk of contamination and are more appropriate for measuring or injecting liquids rather than streaking or inoculating media.
C. Needle & syringe: Needles with syringes are mainly used in clinical or laboratory procedures for injecting liquids or drawing samples. They are not standard instruments for sterile transfer between culture media in microbiology because they are less precise for streaking or isolating colonies.
D. all above are true: Only the loop and needle are routinely used for sterile transfers in microbiology. Syringes are not standard instruments for transferring cultures between media, so this option is incorrect.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
A. The organism cannot tolerate salt: Mannitol Salt Agar (MSA) contains 7.5% NaCl, which inhibits the growth of most bacteria except halotolerant organisms. Growth on this medium indicates that the organism can tolerate high salt concentrations, so inability to tolerate salt is not supported by the observation.
B. The organism ferments mannitol: MSA contains mannitol and a pH indicator (phenol red). When bacteria ferment mannitol, acidic byproducts lower the pH, turning the agar yellow around the colonies. The presence of a yellow zone surrounding growth indicates that the organism is a mannitol fermenter, commonly seen with Staphylococcus aureus.
C. The organism is Gram-negative: MSA is selective for Gram-positive bacteria due to its high salt concentration. Gram-negative bacteria are typically inhibited and do not grow well on this medium. Therefore, growth on MSA suggests the organism is Gram-positive, not Gram-negative.
D. The organism produces hemolysin: Hemolysis is detected on blood agar, where lysis of red blood cells produces clear or greenish zones around colonies. The yellow zone on MSA is due to mannitol fermentation and not hemolysin production, so this observation does not indicate hemolysis.
Correct Answer is A
Explanation
A. To prevent distortion of cells: Allowing the smear to air-dry completely ensures that the bacterial cells retain their natural shape and size. If the smear is heat-fixed while still wet, the water can rapidly boil, causing cells to rupture, shrink, or burst, which distorts their morphology. Maintaining cell integrity is essential for accurate microscopic examination and identification of bacteria.
B. To speed up staining: Air-drying is not intended to speed up staining; in fact, it is a preparatory step to preserve cell structure before applying stains. Proper drying ensures that stains adhere evenly without artifacts caused by residual moisture.
C. To make the bacteria grow: Smear preparation does not promote bacterial growth. Heat fixing kills the bacteria, making them safe to handle and fixing them to the slide. Growth occurs only on appropriate culture media, not on a prepared smear.
D. To increase contrast: Contrast is primarily achieved through the staining process, such as Gram staining or simple stains. Air-drying itself does not enhance contrast; it only prepares the cells to be fixed and stained properly without distortion.
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