MCQ on Isolation, classification and Identification of microorganisms (Medical Microbiology)

40 plus questions - Multiple Choice Questions on Classification, Culture, and Identification of the microorganisms

1. Which of the following microorganism has the cocci cell shapes and sizes arranged usually in tetrad structures?
a) Streptococcus pneumoniae
b) Staphylococcus aureus
c) Chlamydia trachomatis
d) Neisseria meningitidis

2. What are the different growth morphology and cell structures used for the classification of fungi? Select all the correct answers:
a) Yeast
b) Mold
c) Mycelia
d) Protozoa

3. Which of the following RNA virus is a highly contagious respiratory pathogen that can easily spread from person to person?
a) Coronavirus 
b) Dengue virus
c) Epstein Barr virus
d) Hepatitis B virus

4. Which of the following metabolic characteristic is a distinguishing characteristic and identification of colonies of E. coli?
a) Hydrogen sulfide formation
b) Indole Formation
c) Lactose fermentation    
d) Urea Degradation

5. Which of the following bacteria is an endospore-forming bacteria that is also a common foodborne pathogen?
a) Bordetella pertusis
b) Clostridium botulinum
c) Klebsiella pneumoniae
d) Streptococcus pneumoniae    

6. A 19-year-old male living in a tropical region of India visited the hospital. He came with a lesion on the lower part of the left leg that according to him first appeared about a week before visiting the hospital. A skin biopsy test was performed and the infection was diagnosed to be a parasitic infection.
Which of the following is a vector-borne disease that can be transmitted to humans by the bite of infected sandflies?
a) Leishmaniasis   
b) Lassa fever
c) Malaria
d) Yellow fever

7. Which of the following is the example of encapsulated gram-positive bacteria?
a) Klebsiella pneumoniae
b) Clostridium perfringens     
c) Streptococcus pneumoniae
d) Haemophilus influenzae

8. Which of the following morphological characteristics is an important identification characteristic of Neisseria gonorrhoeae?
a) Gram-Negative Diplococci
b) Gram-Positive Bacilli
c) Gram-Negative Bacilli
d) Gram-Positive Diplococci

9. A 7 year old girl developed a sore throat and fever for 2 days. On the second day, the symptoms got worse and she was taken to the hospital. Microscopic examination and culture of the sputum sample revealed gram-positive cocci that appear in chains.
Which of the following bacteria could be the possible pathogen?
a) Acinetobacter baumannii
b) Chlamydia trachomatis
c) Staphylococcus aureus
d) Streptococcus pyogenes

10. Which of the following are the growth morphology of the protozoa?
a) Multicellular and non motile
b) Unicellular and non motile
c) Multicellular 
d) Unicellular and motile

11. A 24 year old sexually active woman had an infection in the vaginal area with genital discharge while urinating. Urinary tract infection was suspected, urine sample and swab specimen were taken and cultured on suitable agar media, a microscopic examination was performed.
Which of the following gram negative bacteria is a sexually transmitted pathogen and cannot be isolated by using regular agar media used in the microbiology laboratory?
a) Mycobacterium tuberculosis
b) Chlamydia trachomatis
c) Neisseria meningitidis
d) Klebsiella oxytoca

12. Which of the following gram positive bacteria is a strict anaerobe and can only grow in the absence of oxygen?
a. Streptococcus pneumoniae
b. Bordetella pertussis
c. Clostridium tetani
d. Staphylococcus epidermidis

13. A 70 year old male visited a clinic with chronic cough, chest pain, fever, chills, and weakness. When examined he said the cough first started about a month ago, he said no other symptoms appeared in the first week, he complained about the loss of appetite due to which he lost some of his body weight. 
Lung infection was suspected, and a chest X-ray was performed which showed infection in both lungs. A sputum sample was taken for the lab diagnosis for the isolation and identification of the microorganism.
Which of the following could be the possible infection?
a) Candidiasis
b) Tuberculosis
c) Measles
d) Cystic fibrosis 

14. Which of the following pulmonary pathogens cannot be easily detected by the gram staining technique when performing a microscopy test?
a) Pseudomonas aeruginosa
b) Streptococcus pneumoniae
c) Bordetella pertussis
d) Mycobacterium tuberculosis

15. The cell structure of gram positive and gram negative bacteria appear as the picture given below after the gram staining procedure
                           Gram positive bacteria                              Gram negative bacteria

Which of the following bacterial cell structure possesses the thick layer of peptidoglycan?
a) Gram positive bacteria
b) Gram negative bacteria

16) 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

17) 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

18) 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

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

20) 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

21) 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

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

23) 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

24) The metabolic reactions are 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

25)Clostridium perfringens on agar can show all of the following cultural characteristics, Except?
a) Microaerophilic
b) Spore-forming
c) H2S production 
d) Haemolysis (alpha and beta)

26) … a rod-shaped, gram-positive, non-spore-forming medically important virulent foodborne pathogen. The common food source of bacteria is raw meat and vegetables, unpasteurized milk, cheese.
a) Rhizopus stolonifer
b) Listeria monocytogenes
c) Clostridium botulinum
d) Cryptococcus neoformans

27)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

28) 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

29) 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

30) … 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

31) Name the bacteria of the Enterobacteriaceae family that have the following characteristics? 

  • swarming growth on culture media 
  • producing a urease enzyme 
  • major urinary tract pathogen
a) Proteus spp
b) Salmonella spp
c) Histoplasma spp
d) Klebsiella spp

32) The following microorganism is an encapsulated gram-negative bacillus that shows lactose fermentation when grown in MacConkey agar. 
Select the correct answer:
a) Pseudomonas aeruginosa
b) Staphylococcus aureus
c) Streptococcus pneumoniae
d) Klebsiella pneumoniae

33) 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

34) 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

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

36) Which of the following culture media is used for the routine laboratory 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

37) 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

38) 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

39) 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

40) 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 (+,-,+,-)

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

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

43) 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

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

45) What are the types of general characteristics that are important for the identification and 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

1.  b) Staphylococcus aureus

2. d) Streptococcus pyogenesis a gram-positive coccus that appears in the chains. Acinetobacter baumannii is a gram-negative rod. Chlamydia trachomitis is gram-negative bacteria. Staphylococcus aureus is a gram-positive coccus present in clusters. 

3. a) Coronavirus. Coronavirus is an RNA virus that is a highly contagious respiratory pathogen. Dengue virus is an RNA virus transmitted to humans via mosquito bites. Epstein Barr virus is a DNA virus that causes infectious mononucleosis. The Hepatitis B virus is a DNA virus that causes liver infection. 

4. c) Lactose fermentation. E. coli is a lactose fermenter while Salmonella is a non-lactose fermenter. The lactose fermentation results in an acid environment thereby yielding a pink colony of E. coli. Hydrogen sulfide, indole formation, and urea degradation (Urease test) are different biochemical tests that are not related to MacConkey agar

5. b) Clostridium botulinum.  Clostridium botulinum is a gram positive foodborne pathogen. Bordetella pertussis is a gram negative bacteria and Klebsiella pneumoniae is a gram-negative bacteria that are common respiratory pathogens and do not form endospores. Streptococcus pneumoniae is a gram positive bacteria that is a common respiratory pathogen that does not produce endospores

6. a) Leishmaniasis, the infection commonly occurs in the tropical part of the world and is transmitted to humans from the bite of the infected sandflies. Lassa fever is transmitted to humans by rodents, Malaria, and Yellow fever are transferred to humans by the bite of mosquitoes.

7. c) Streptococcus pneumoniae is a gram positive encapsulated bacteria. Clostridium perfringens is a gram positive bacteria with no capsules present in the outer cell structure. Klebsiella pneumoniae and Haemophilus influenzae are gram negative encapsulated bacteria.

8. a) Gram-Negative DiplococciN. gonorrheae is one of the major pathogens that causes sexually transmitted disease. It is properly isolated and identified by using Chocolate agar. 

9. d) Streptococcus pyogenesis a gram positive coccus. Acinetobacter baumannii and Chlamydia trachomatis are gram negative bacteria. 

10. d) Unicellular and motile. Protozoa is a single cell eukaryotic, motile microorganism, an example is the most widely known Plasmodium falciparum that can cause malaria.

11. b) Chlamydia trachomatisis a gram negative bacteria that causes sexually transmitted disease that is mainly seen in women. It is one of the major pathogens of eye infection and blindness, the bacteria can be isolated by using egg yolk sac or tissue culture method. Mycobacterium tuberculosis is a gram negative, acid-fast bacteria that is a major pathogen of respiratory infections. Neisseria meningitidis is a gram negative diplococcus that is a major cause of meningitis. Klebsiella oxytoca is a gram negative bacillus that can cause colitis and sepsis in humans.

12. c) Clostridium tetani, is a gram positive, spore forming, and strictly anaerobic bacteria, isolation of the bacteria is difficult in the presence of even a tiny amount of oxygen. Streptococcus pneumonia is an anaerobic bacteria and can grow in the presence of a small amount of oxygen. 
Bordetella pertussis is a gram negative anaerobic bacteria. Mycoplasma pneumoniae is a gram positive bacteria that can grow anaerobically as well as aerobically. 

13. a) Tuberculosis, is a lung infection disease, it is one of the major bacterial diseases predominant in developing countries. It can be spread through respiratory secretions, the common symptoms are fever and cough.
Candidiasis is a fungal infection, skin infection, and mouth or vaginal infection that can occur due to the overgrowth of the fungus, Candida albicans. 
Measles is a disease caused by a virus, it is spread via respiratory droplets. The common symptoms are pink or red spots on the skin surface, dry cough, and runny nose. Children are more susceptible to this disease.
Cystic fibrosis is an inherited disease, infection in the lungs and digestive system. Symptoms include cough and lung infection.
14.d) Mycobacterium tuberculosis, is acid-fast bacilli that consist of mycolic acid in the cell wall. Thus it cannot be properly identified by using the common gram staining method. Ziehl-Neelsen stain is the stain used for acid-fast bacteria. 

15. a) Gram positive bacteria, peptidoglycan is present in both types of bacteria, however, in gram positive bacteria the layer is much thicker than in gram negative bacteria. 

16. c)Ziehl-Neelsen stain
Ziehl-Neelsen stain is mainly used for staining acid-fast bacteria such as Mycobacterium spp, and Nocardia spp. A negative stain is used for the identification of bacterial cell organization, and the presence of bacterial flagella. The gram stain technique is used for the staining of gram-positive and gram-negative bacteria. Schaeffer Fulton stain is used for staining endospores present in bacterial cells.

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

18. b)India ink
The 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.  

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

20. b)Pink
Gram negative bacteria take the color of safranin stain and appear pink or red. Gram positive bacterial cell wall takes the stain of crystal violet and appears purple or blue even after the use of a decolorizer.

21. c)Lactose fermentation
E. coli is lactose fermenter and Salmonella spp is non lactose fermenter. Urease productionhemolytic property, and Hydrogen sulfide production of bacteria are not detected in the MacConkey agar

22. d)Streptococcus spp
Streptococcus spp is catalase-negative. Catalase test is one of the routine laboratory tests done in a microbiology laboratory, it helps in the detection and differentiation of catalase positive and catalase negative bacteria

23. d) Proteus vulgaris

24. c) Citrate
In the IMViC test (Biochemical tests for Enterobacteriaceae family) E. coli shows a negative result for the Simmons citrate agar test, this means the bacteria do not use carbon as a source of energy and thus the agar color does not change, and remains green. E. coli shows positive lactose, indole, and glucose tests.

25. a)Microaerophilic
Clostridium perfringens is an obligate anaerobic bacteria that do not require oxygen to grow and thus it is not Microaerophilic, microaerophilic bacteria require low amounts of oxygen for growth. 
C. perfringens is a spore-forming bacteria, that produce H2S and hemolysis on blood agar.

26. b) Listeria monocytogenes
Option a) and d) are types of fungi. c) C. perfringens is a spore-forming bacteria that can easily grow in canned food and fermented products.

27. c) Streptococcus pyogenes
28. a) The causative agent of smallpox
29. b) Lactobacillus acidophilus
30. d)Candida albicans
31. a)Proteus spp
32. d) Klebsiella pneumoniae
33. b) Chocolate agar
34. d) They are motile
35. c)Staphylococcus spp
36. a) Xylose lysine deoxycholate agar
37. b) Thayer martin agar
38. d) Used as a selective media for Mycobacterium tuberculosis
39. a) Bacillus anthracisand (d) Clostridium perfringens
40. a) IMViC (+,+,-,-)
41. a), b) and c)
42. e) All of the above
43. a), b), c), and d)
44. d) Protozoa
45. 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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