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Questions and Answers
What does the abbreviation 'R' stand for when classifying an organism's response to an antibiotic?
What does the abbreviation 'R' stand for when classifying an organism's response to an antibiotic?
The streak plate method does not require a sterile loop to pick up colonies.
The streak plate method does not require a sterile loop to pick up colonies.
False
What temperature is used to incubate the agar plates during the procedure?
What temperature is used to incubate the agar plates during the procedure?
37 degrees Celsius
The antibiotic classification indicating that growth is inhibited somewhat, but not effectively, is termed __________.
The antibiotic classification indicating that growth is inhibited somewhat, but not effectively, is termed __________.
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Match the following classifications with their meanings:
Match the following classifications with their meanings:
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What is the primary purpose of a culture and sensitivity test?
What is the primary purpose of a culture and sensitivity test?
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A stool culture can identify bacteria responsible for symptoms of intestinal disease.
A stool culture can identify bacteria responsible for symptoms of intestinal disease.
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What is the ideal specimen for a urine culture?
What is the ideal specimen for a urine culture?
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Before testing, a patient must not take any antibiotics for ___ hours.
Before testing, a patient must not take any antibiotics for ___ hours.
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What color do Gram-positive bacteria appear after Gram staining?
What color do Gram-positive bacteria appear after Gram staining?
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Match the type of sample with its purpose:
Match the type of sample with its purpose:
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Gram-negative bacteria appear violet after Gram staining.
Gram-negative bacteria appear violet after Gram staining.
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What can dilute urine and lead to inaccurate test results?
What can dilute urine and lead to inaccurate test results?
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Name one example of a Gram-negative bacilli.
Name one example of a Gram-negative bacilli.
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The _____ method is commonly used for antibiotic sensitivity testing.
The _____ method is commonly used for antibiotic sensitivity testing.
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A skin infection is characterized by symptoms like pain and redness at the site.
A skin infection is characterized by symptoms like pain and redness at the site.
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What type of containers should be used for collecting specimens for culture testing?
What type of containers should be used for collecting specimens for culture testing?
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Match the following bacterial groups with their examples:
Match the following bacterial groups with their examples:
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What is the purpose of antibiotic susceptibility testing?
What is the purpose of antibiotic susceptibility testing?
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What is the primary purpose of a blood culture?
What is the primary purpose of a blood culture?
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Antibiotic disks are placed on the agar after the plate is inoculated and incubated.
Antibiotic disks are placed on the agar after the plate is inoculated and incubated.
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What is the result observed under the microscope for Gram-positive bacteria?
What is the result observed under the microscope for Gram-positive bacteria?
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Antibiotics should not be taken by the patient for at least 24 hours before testing.
Antibiotics should not be taken by the patient for at least 24 hours before testing.
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What is bacteremia?
What is bacteremia?
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A blood culture is often performed to evaluate _____ fever.
A blood culture is often performed to evaluate _____ fever.
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Match the microbiological growth media with their descriptions:
Match the microbiological growth media with their descriptions:
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What must be done to the skin prior to obtaining a blood sample?
What must be done to the skin prior to obtaining a blood sample?
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Septicemia refers to the presence of bacteria in the blood without leading to sepsis.
Septicemia refers to the presence of bacteria in the blood without leading to sepsis.
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What temperature should media bottles be incubated at before taking a sample?
What temperature should media bottles be incubated at before taking a sample?
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What is the primary use of MacConkey agar?
What is the primary use of MacConkey agar?
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Chocolate agar is used primarily to grow Gram-positive bacteria.
Chocolate agar is used primarily to grow Gram-positive bacteria.
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What temperature should inoculated media be incubated at?
What temperature should inoculated media be incubated at?
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Gram-positive bacteria have a thick mesh-like cell wall made of __________.
Gram-positive bacteria have a thick mesh-like cell wall made of __________.
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Match the type of agar with its primary purpose:
Match the type of agar with its primary purpose:
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What is the first step in the preparation of growth media?
What is the first step in the preparation of growth media?
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Gram-negative bacteria retain the crystal violet dye in the Gram staining protocol.
Gram-negative bacteria retain the crystal violet dye in the Gram staining protocol.
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What should be done to prevent condensation of moisture on the plates during storage?
What should be done to prevent condensation of moisture on the plates during storage?
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Study Notes
Clinical Laboratory - Cultures and Sensitivity
- Culture is a lab test isolating microorganisms in a growth medium.
- It's used to identify microorganisms causing infections and for a definitive diagnosis.
- Culture and sensitivity tests are done to detect and identify bacteria causing infections, and to identify the best antibiotic for treatment.
Culture Samples - Specimen Collection
- Specimen collection for culture and sensitivity testing must adhere to standard precautionary techniques to prevent contamination.
Urine Sample
- A urine culture is done when a urinalysis shows an abnormal result, like increased white blood cells, suggesting an infection.
- Patients shouldn't take antibiotics 48 hours before testing.
- Sterile containers are used for urine samples.
- Sufficient urine sample quantity is essential, and morning mid-stream samples are ideal for quantitative bacteriuria examination.
- The sample must be in the lab within 30 minutes of collection.
- Using diuretics or drinking excessive fluids can dilute the urine, affecting the accuracy of bacteria concentration measurements.
Stool Sample
- Stool culture detects bacteria causing intestinal diseases (prolonged diarrhea, bloody diarrhea, increased gas, abdominal pain, fever).
- More than 50 types of bacteria normally reside in the intestines.
- Patients shouldn't take antibiotics 48 hours before testing.
- Enough stool sample is needed, and the sample should be in the lab promptly (within 30 minutes of collection).
Wound Sample
- Skin or wound cultures detect bacteria infecting skin, wounds, burns, surgical wounds, or animal bites.
- Common infection symptoms include site pain, redness, tenderness, swelling, warmth, red streaks, swollen lymph nodes, and pus.
- No antibiotics should be taken within 48 hours before testing.
- Samples should be taken with a sterile swab, and pus samples should be taken from deep inside the wound.
Blood Sample
- Blood culture identifies bacterial infections in the bloodstream.
- Blood normally doesn't contain bacteria.
- Bacteria can enter the bloodstream due to complications of infections like pneumonia or meningitis, surgery (especially on mucous membranes), catheters, or foreign bodies entering arteries or veins (including intravenous drug use).
- Bacterial bloodstream infections are serious as bacteria can spread to any part of the body.
- Blood cultures may be done for unexplained fever (PUO).
- Bacteremia is bacteria in the blood, while Septicemia is pathogenic organisms in the blood, leading to sepsis (where bacteria release toxins, causing fever, chills, toxicity, and reduced blood pressure).
Culture Media
- Nutrient Agar is a common non-fastidious bacteria growth medium for routine bacterial cultivation.
- Agar is a polysaccharide that solidifies culture media, having a high gelling capacity and being free of substance toxic to bacteria.
- This medium is the base for different types of media.
- Other types of media mentioned include Blood Agar Plate (BAP), Chocolate Agar (CHOC), MacConkey Agar (MAC) and Salmonella Shigella Agar (S.S Agar).
Gram Staining
- Gram staining is an empirical method for differentiating bacterial species into Gram-positive and Gram-negative based on their cell wall properties.
- Gram-positive bacteria have a thick cell wall (peptidoglycan); they stain purple.
- Gram-negative bacteria have a thinner cell wall; they stain pink.
Gram Stain Procedure
- Preparing a slide, mixing bacteria specimen with saline, observing and recording results as violet or red cells.
Antibiotics - Sensitivity Test
- This test determines antibiotic effectiveness against microorganisms.
- Kirby-Bauer Method (Agar diffusion method) is a common approach for antibacterial sensitivity testing.
- Tests involves inoculation of an agar plate with the organism, placing antibiotic disks onto the agar, and incubating.
- A zone of inhibition (no growth) around an effective antibiotic disk.
- Effective antibiotics create a zone of inhibition, meaning the antibiotic is sensitive, or inhibiting growth; resistance (R) means the antibiotic doesn't inhibit growth, and intermediate (I) means the antibiotic inhibits growth somewhat, but not completely.
Procedures - Streak Plate Method
- The streak plate method is used to isolate bacterial colonies for individual identification.
- Plates are dried, specific colonies are picked and streaked repeatedly on an agar plate.
- The plate is turned 90 degrees and repeated to ensure proper spacing.
- The agar surface is swabbed for complete coverage.
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Description
Test your knowledge on antibiotic classifications and microbiological testing methods. This quiz covers key concepts related to culture and sensitivity tests, Gram staining, and more. Perfect for students in microbiology or health sciences courses.
