MCQ on Isolation and Identification of microorganisms (Medical Microbiology)

Multiple Choice Questions on Microbial Culture and Identification 

1) A bacteriological stain also known as the differential stain is used for the identification of acid-fast organisms, what is the name of the stain?
a)Negative stain
b)Gram stain
c)Ziehl-Neelsen stain
d)Schaeffer Fulton stain

2) A Capsule is a................................layer lying outside the bacterial cell and can be found in both gram-positive and gram-negative bacteria
a) Lipopolysaccharide layer
b) Polysaccharide
c) Phospholipid
d) None of the Above

3) Which of the following dye is commonly used for the Negative staining technique?
a) Crystal violet
b) India ink
c) Lactophenol cotton blue
d) Periodic acid- Schiff stain

4) All of the following are common stains used in microbiology laboratory, Except:
a) Bismarck brown
b) Lactophenol cotton blue
c) Ziehl - Neelsen stain
d) Crystal violet 

5) Gram staining technique is used for the differentiation of gram-positive and gram-negative bacteria. What color do gram-negative bacteria show when observed under the microscope after the staining procedure?
a) Blue
b) Pink
c) Purple
d)Green

6) MacConkey’s agar is both selective and differential media that is primarily used for the isolation of enteric bacteria. Which of the following metabolic property differentiate the pink colored colonies of E. coli from Salmonella spp that does not show any color?
a) Urease production
b) Hemolytic activity
c) Lactose fermentation
d) Hydrogen sulfide production

7) All of the following bacteria are catalase positive, except
a) E. coli
b) Shigella spp
c) Staphylococcus spp
d) Streptococcus spp

8) Which of the bacteria consists of flagella and shows a positive motility test?
a) Staphylococcus aureus
b) Yersinia pestis
c) Klebsiella pneumoniae
d) Proteus vulgaris

9) The metabolic reactions shown by different bacteria help in the identification and classification of bacteria, which of the following biochemical tests show a negative result for Escherichia Coli?
a) Lactose
b) Indole
c) Citrate
d) Glucose

10)The cultural characteristics of Clostridium perfringens are all of the given below, Except?
a) Microaerophilic
b) Spore-forming
c) Lecithinase positive
d) Stormy fermentation

11) …................is a rod-shaped, gram-positive, non-spore-forming medically important virulent foodborne pathogen that can easily grow in raw meat and vegetables, unpasteurized milk, cheese.
a) Rhizopus stolonifer
b) Listeria monocytogenes
c) Clostridium botulinum
d) Cryptococcus neoformans

12)Which of the following bacteria have a hemolytic property that can grow well in blood agar?
a) Bacillus anthracis
b) Proteus vulgaris
c) Streptococcus pyogenes
d) Candida albicans

13) All of the statements regarding Bacillus anthracis are true, Except
a) The causative agent of smallpox
b) Nonhemolytic colonies appear on Blood agar
c) Commonly transmitted from animals to humans
d) Endospore-forming bacteria

14) Which of the following bacteria is a part of the human gut and mouth flora that is also important in making some fermented dairy products?
a) Candida albicans
b) Lactobacillus acidophilus
c) Staphylococcus aureus
d) Micrococcus luteus

15) …............is a type of fungus that is a part of normal gut flora and it can be found as one of the common pathogens of the skin, vaginal, and or oral infections 
a) Neisseria gonorrhoea
b) Yersinia pestis
c) Coccidiodes immitis
d) Candida albicans
e) Penicillium marneffei

16) Which of the following organism of the Enterobacteriaceae family have the characteristics of swarming growth on culture media, produces urease enzyme, and is major urinary tract pathogen?
a) Proteus spp
b) Salmonella spp
c) Histoplasma spp
d) Klebsiella spp

17) The following microorganism is an encapsulated gram-negative bacillus that show lactose fermentation when grown in MacConkey agar.
a) Pseudomonas aeruginosa
b) Staphylococcus aureus
c) Streptococcus pneumoniae
d) Klebsiella pneumoniae

18) Which of the following media is one of the commonly used media for the proper isolation of gram negative pathogens such as Haemophilus spp and Neisseria gonorrhoeae?
a) Potato dextrose agar
b) Chocolate agar
c) Nutrient agar
d) Mac Conkey agar

19) All of the statements are true about Corynebacterium spp, Except
a) Requires a tellurite agar
b) Gram-positive
c) Colonies appear black or gray on agar
d) They are motile

20) Mannitol Salt agar with high salt concentration is both selective and differential media used for the isolation of which of the following gram-positive cocci?
a) Klebsiella spp
b) Streptococcus spp
c) Staphylococcus spp
d) Pseudomonas spp

21) Which of the following media is used for the routine bacteriological isolation of Salmonella and Shigella spp?
a) Xylose lysine deoxycholate agar
b)Thiosulfate citrate bile salts agar
c) Mannitol salt agar
d) Bile esculin agar

22) Which of the following is the selective media used for the cultivation and isolation of Neisseria gonorrhoeae and N. meningitidis?
a) Buffered charcoal- yeast extract agar
b)Thayer martin agar
c)Xylose lysine deoxycholate agar
d) Bile esculin agar

23) All of the following statements are correct about the most common bacteriological media called sheep blood agar that is used in the microbiology laboratory, Except
a) It consists of 5% of sheep blood
b) Used for the culture of common fastidious bacteria
c) It is used for the culture of hemolytic bacteria 
d) Used as a selective media for Mycobacterium tuberculosis

24) Select all the major and clinically important spore-forming bacteria
a) Bacillus anthracis
b) Aspergillus flavus
c) Lactobacillus acidophilus
d) Clostridium perfringens
e) Haemophilus influenzae

25) Biochemical tests are a common and conventional laboratory procedure in the differentiation and identification of enteric bacteria, which of the following test result (Indole, methylene, Voges-Proskauer, and Citrate) is correct in the identification of E.coli?
a) IMViC (+,+,-,-)
b) IMViC ( +,-,+,+)
c) IMViC ( -,-,+,-)
d) IMViC (+,-,+,-)

26) Select all the common specimens collected for the laboratory diagnosis of dermatophytes
a) Nail clippings
b) Skin scrapings
c) Hair 
d) Urine
e) Blood

27) Which of the following are the routine diagnostic methods performed for the microbial examination of blood specimen collected from a patient with a high fever for more than 2 days?
a) Direct microscopic examination
b) Culture media
c) Sero diagnosis 
d) Antibiotic susceptibility test
e) All of the above

28) Which of the following methods are the most common and routine culture methods performed in the microbiology lab for the proper isolation and identification of bacteria and fungi? Select all the correct answers
a) Streak culture/ surface plating
b) Stab culture
c) Pour plate culture
d) Liquid culture

29) Which of the following microorganisms can grow only as strict intracellular parasites?
a) Bacteria
b) Viruses
c) Fungi
d) Protozoa

30) What are the types of characteristics mainly used for the classification of protozoa? Select all the correct answers
a) Presence of flagella or cilia
b) The examination of the infection sites 
c) They are prokaryotes in cellular organization
d) Study of the life cycle of organisms





Multiple Choice Answers:
1. c)Ziehl-Neelsen stain
The correct answer is c)Ziehl-Neelsen stain, the stain mainly used for staining of acid fast bacteria such as Mycobacterium spp, and Nocardia spp. Negative stain is used for the identification of bacterial cell organization, presence of bacterial flagella. Gram stain technique is used for the staining of gram positive and gram negative bacteria. Schaeffer fulton stain is used for staining of endospores present in bacterial cells.

2. b)Polysaccharide
The correct answer is Polysaccharide, it is a carbohydrate present in cell wall of some encapsulated  bacteria. Lipopolysaccharide is present in cell wall of gram negative bacteria. Phospholipid is present in most of the cell membranes of microorganisms

3. b)India ink
Correct answer is India ink, used for the staining of fungi, mainly for the detection of Cryptococcus neoformans in cerebrospinal fluid. Crystal violet is used for the staining of bacterial cells. Lactophenol cotton blue is a common fungal stain. Periodic acid- Schiff stain is used for the staining of infected tissue cells, mainly used in histopathology.  

4. a)Bismarck brown
The correct answer is Bismarck brown, mainly used for histology study.  Lactophenol cotton blue is a fungal stain, , Crystal violet for the detection of bacteria, Ziehl - Neelsen stain for acid fast microorganisms.

5. b)Pink
The correct answer is pink color or red color, gram negative bacteria take the color of safranin stain used in gram staining technique whereas gram positive bacteria cell wall take the stain of crystal violet and appear purple or blue even after the use of decolorizer.

6. c)Lactose fermentation
The correct answer is Lactose fermentation, E. coli is lactose fermenter and Salmonella spp is non lactose fermenter. Urease production, hemolytic property, and Hydrogen sulfide production of bacteria is not detected in the MacConkey agar

7. d)Streptococcus spp
The correct answer is Streptococcus spp, it is catalase negative. Catalase test is one of the routine laboratory test done in a microbiology laboratory, it helps in the detection and differentiation of catalase positive and catalase negative bacteria

8. d) Proteus vulgaris
9. c) Citrate
10. a)Microaerophilic
11. b) Listeria monocytogenes
12. c) Streptococcus pyogenes
13. a) The causative agent of smallpox
14. b) Lactobacillus acidophilus
15. d)Candida albicans
16. a)Proteus spp
17. d) Klebsiella pneumoniae
18. b) Chocolate agar
19. d) They are motile
20. c)Staphylococcus spp
21. a) Xylose lysine deoxycholate agar
22. b) Thayer martin agar
23. d) Used as a selective media for Mycobacterium tuberculosis
24. a) Bacillus anthracisand (d) Clostridium perfringens
25. a) IMViC (+,+,-,-)
26. a), b) and c)
27. e) All of the above
28. a), b), c) and d)
29. d) Protozoa
30. a) Presence of flagella or cilia, b)The examination of the infection sites, and d) Study of the life cycle of organisms









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