Culture Bacterial Media Methods by Conventional, Automated Multiple Choice Question And Answers

Culture Media/Methods

Question 1. Which of the following will grow on chocolate agar?

1. Neisseria meningitidis
2. Haemophilus influenzae
3. Vibrio cholerae
4. Listeria monocytogenes
5. Staphylococcus aureus

Answer. All (1, 2, 3, 4, 5) (All options)

• Chocolate agar is a highly-enriched media, therefore supports the growth all the organisms given in the questions.

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Question 2. Which of the following is an enrichment media:

1. Alkaline peptone water
2. Monsour’s taurocholate Tellurite peptone water
3. Selenite F broth
4. All of the above

Answer. (4) (All of the above)

Question 3. Both Staphylococcus epidermidis and Escherichia coli were grown in lab simultaneously on a culture mediAfter overnight incubation, it was observed that only coli flourished whereas S. epidermidis didn’t grow. The possible reason(s) is/are:

1. Temperature of growth was set wrong
2. Culture media was selective coli produced colicin that inhibited S. epidermidis growth
3. Gram positives have more generation time
4. Culture media was differential

Answer. (2) (Culture media was selective)

• Temperature—Both coli and S. epidermidis grow at same temperature (37°C).
• Selective media—Addition of crystal violet to a media (e.g. MacConkey agar) makes it selective, which inhibits the growth staphylococci but not coli.
• Colicins are plasmid coded species specific anti-bactericidal substances produced by E.coli; they do not have any bactericidal effect on S.epidermidis.
• Generation time of staphylococci are slightly more than coli (30 min vs 20 min);however overnight incubation is sufficient for growth of both coli and S.epidermidis.
• Differential media can differentiate between two groups of organisms, e.g. MacConkey agar differentiating Gram-negatives into LF and NLF; however, it does not inhibit the growth of any organism. If any selective substances are added, it makes the differential media more selectivFor e.g. MacConkey agar added with crystal violet inhibitsS. aureus. Such MacConkey agar have properties of both selective and differential media.

Question 4. Oxidase positive:

1. Pseudomonas
2. Klebsiella
3. Staphylococcus
4. coli

Answer. (1) (Pseudomonas)

• Pseudomonas is oxidase positive.

Question 5. Antibiotic sensitivity testing is usually done on:

1. Blood agar
2. Chocolate agar
3. MacConkey agar
4. Mueller Hinton agar

Answer. (4) (Mueller Hinton agar)

Question 6. CLED medium is used in preference to MacConkey agar in relation to culture of organism involved in urine infection. The reason is:

1. It prevents swarming of Proteus
2. Differentiates LF and NLF
3. Promotes Staphylococcus and Candida
4. Identifies Pseudomonas

Answer. (3) (Promotes Staphylococcus & Candida)

CLED agar (Cysteine lactose electrolyte-deficient agar): This is similar to MacConkey agar,differentiates between LF and NLF. It is used as an alternative to combination of blood agar and MacConkey agar, for the processing of urine specimens.

• Advantages over MacConkey agar: It is less inhibitory than MacConkey agar, supports the growth of Gram-positive bacteria (except β hemolytic Streptococcus) and Candida.
• Advantage over blood agar: It can prevent the swarming of Proteus.

Question 7. Which of following culture media combination is/are true except:

1. Thayer-Martin media: Gonorrhea
2. Chocolate agar: Enriched media
3. Lowenstein-Jensen medium: Mycobacterium tuberculosis
4. Mueller-Hinton agar: Corynebacterium diphtheriae
5. MacConkey’s agar: Nonlactose fermenters form lactose fermenters

Answer. (4) (Mueller-Hinton agar)

• Thayer-Martin media: Gonorrhea (Selective media)
• Chocolate agar: Enriched media
• Lowenstein-Jensen Medium: Mycobacterium tuberculosis (selective media)
• Muller-Hinton agar: For antibiotic susceptibility test
• Mac Conkey’s agar: Differential media, differentiates LF (pink colony) and NLF (colorless colonies).

Question 8. Triple sugar iron test detects all the following properties except:

1. Gas
2. H2S
3. Sugar fermentation
4. Citrate utilization

Answer. (4) (Citrate utilization)

• TSI test detects- fermentation of sugars, gas & H2S production.

Question 9. TSI is:

1. Selective
2. Enrichment
3. Enriched
4. Composite

Answer. (4) (Composite)

• TSI is a popular composite medium, which indicated whether bacteria ferments glucose only, or lactose and sucrose also, with/without gas formation, besides indicating H2S production as well.

Question 10. Selective media for Shigella:

1. Wilson blair
2. TCBS
3. DCA
4. Blood agar

Answer. (3) (DCA)

• Deoxycholate citrate agar (DCA) and Xylose lysine deoxycholate (XLD) are selective media for Shigella.

Question 11. Recommended transport medium for stool specimen suspected to contain enteric pathogens is:

1. Amie’s medium
2. Buffered glycerol saline medium
3. MacConkey medium
4. Blood agar

Answer. (2) (Buffered…)

Recommended transport medium for stool specimen is:

• Buffered glycerol saline medium (when Salmonella or Shigella is suspected)
• VR medium-(when Vibrio cholerae is suspected).

Question 12. Agar conin nutrient agar is: (NEET Pattern Based)

1. 2%
2. 4%
3. 1%
4. 3%

Answer. (1) (2%)

• 2% of agar is routinely used for making solid media.

Question 13. Robertson cooked meat broth is an example:

1. Enriched media
2. Enrichment media
3. Nutrient media
4. Anaerobic media

Answer. (d) (Anaerobic…)

• Roberson-cooked meat broth is used for culture of anaerobic organisms.

Question 14. Blood agar is an example:

1. Enriched media
2. Enrichment media
3. Nutrient media
4. Special media

Answer. (1) (Enriched…)

• Enriched media contains extra nutritional factors like blood, serum, egg so that it supports the fastidious organisms, e.g. Blood agar, Chocolate agar, Loeffler’s serum slope.

Question 15. Which one of the following is true?

1. Agar has nutrient properties
2. Chocolate medium is selective medium
3. Addition of selective substances in a solid medium is called enrichment media
4. Nutrient broth is basal medium

Answer. (4) (Nutr….)

• Nutrient broth, Peptone water, and Nutrient Agar are the basal media
• Used to prepare solid media, but it has no nutritive value
• Chocolate medium is enriched medium
• Addition of selective substances in a solid medium is called selective medium.

Question 16. Smith Noguchi’s media is used for:

1. Salmonella
2. Klebsiella
3. Spirochetes
4. Bacillus

Answer. (3) (Spirochetes)

• Smith Noguchi’s medium: Is used for Nonpathogenic Treponemes
• Pathogenic Treponemes cannot be grown in artificial culture medium.

Question 17. To prevent swarming the % agar in Nutrient agar has to be increased at least to:

1. 2%
2. 4%
3. 6%
4. 8%

Answer. (3) (6%)

Agar concentration routinely used: (1) In solid media 2%, (2) Semisolid media 0.5-1%, (3) To inhibit swarming 6%.

Question 18. Northern blot is for:

1. Protein
2. DNA
3. RNA
4. DNA Protein interaction

Answer. (3) (RNA)

Western blot detects proteins; is so named for its similarity to Southern blot (detects DNA fragments) and Northern blot (detects mRNAs)

Question 19. Which of the following technique is based on RNA?

1. Reverse transcriptase PCR
2. Next generation sequencing
3. Sanger’s technique
4. Western blot

Answer. (1) [RT (Reverse transcriptase (PCR)]

• Reverse transcriptase PCR involves reverse transcription of RNA to DNA, followed by amplification of the DNA.

Question 20. In PCR, proofreading is done by:

1. Pfu Polymerase
2. TaPolymerase
3. Telomerase
4. DNA topoisomerase
5. Polymerases

Answer. (1, 2) (Pfu Polymerase, TaPolymerase) R

Pfu DNA polymerase, derived from Pyrococcus furiosus, has superior thermostability and proofreading properties compared to other thermostable polymerase such as Taq polymerase.

Question 21. PCR is used to:

1. Detect target plasmids
2. Amplify small amount of DNA
3. Seal the cut ends of DNA
4. Cleave the bacterial plasmid

Answer. (2) (Amplify small…)

• The polymerase chain reaction (PCR) is a biochemical technology in molecular biology to amplify a single or a few copies of a piece of DNA, generating thousands to millions of copies of a particular DNA sequence.

Question 22. Enzyme(s) used in polymerase chain reaction is/are:

1. Restriction endonuclease
2. DNA polymerase
3. Alkaline phosphate
4. RNA polymerase
5. Reverse transcriptase

Answer. (2) (DNA…)

• TaPolymerase is a DNA Polymerase that amplifies the target gene into millions of copy without denaturation. It is one of the basic requirements of PCR along with other requirements like primers, Nucleotide and Mg++ ion.
  About Other Options
• Restriction endonuclease: Required for RFLP (Restricted Fragment Length Polymorphism)
• Reverse transcriptase: Required for Reverse transcriptase PCR (RT-PCR)
• Alkaline phosphate: Required for ELISA
• RNA polymerase: Not required.

Question 23. All of the following are required in PCR except:

1. Deoxyribonucleotides
2. Thermostable enzyme/DNA polymerase
3. Dideoxyribonucleotides
4. Magnesium/ssDNA/Template DNA

Answer. (3) (Dideoxyribonucleotides)

Dideoxyribonucleotides is not used in PCR.

Requirement of PCR

• TaPolymerase: Obtained from Thermus aquaticus plant which can withstand the high temperature.
• Primers-short oligonucleotide complementary to a small sequence of the target DNA
• Deoxynucleotide, Mg++ ion
• Target DNA present in the sample.

Question 24. Northern bloting is used for separation of:

1. DNA
2. RNA
3. Proteins
4. None

Answer. (2) (RNA)

• Northern blotting is used for detection of- RNA
• Southern blotting is used for detection of- DNA
• Western blotting is used for detection of- Protein

Question 25. For PCR, Thermus acquaticus plant is used to prepare:

1. DNA polymerase
2. RNA polymerase
3. Primers
4. Restriction endonuclease II

Answer. (1) (DNA pol…)

The heat-stable DNA polymerase enzyme used for PCR is derived from plant Thermus acquaticus.

Question 26. DNA hybridization is called:

1. Southern blot
2. Northern blot
3. Eastern blot
4. Western blot

Answer. (1) (Southern blot)

• DNA hybridization is called Southern blot
• RNA hybridization is called Northern blot.