MCQs and Answers on cultivation (culture/incubation), Isolation 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 media is formulated with additional nutrients to support the growth of fastidious or nutritionally demanding bacteria that may not grow well on basic media?

a) Differential media

b) Enriched media

c) Nutrient agar (media)

d) Selective media

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 visits a local healthcare center. He has a lesion on the lower part of the left leg, he reports the lesion first appeared 5 days ago. A skin biopsy test confirms a parasitic infection.

Which of the following is a vector-borne parasitic infection 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 is brought to a healthcare clinic, she has developed sore throat and fever for last 2 days, no other symptoms is observed by the physician. Microscopic examination and culture of the sputum sample reveals 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 comes to a local healthcare center with infection in the vaginal area and genital discharge while urinating. Urinary tract infection (UTI) is suspected, urine sample and genital swab specimen is taken for culture and identification of the possible pathogen.

Which of the following gram negative sexually transmitted bacteria has special growth requirements?

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 visits a emergency department with chronic cough, chest pain, fever, chills, and weakness. He reports the cough first started three weeks ago with no other symptoms in the first week, he complains about the loss of appetite due to which he has lost some of his body weight. Upon examination fever is noted, a chest X-ray reveals infection in both lungs, pneumonia is suspected. A sputum sample and a throat swab specimen is taken for the identification of the pathogen and diagnosis of the disease.

Which of the following could be the possible infection?

a) Candidiasis

b) Tuberculosis

c) Measles

d) Cystic fibrosis 

14. Among the following respiratory pathogens, which of the following is difficult to identify using the Gram staining technique in microscopy tests?

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) Identify the gram positive bacteria that shows alpha-hemolytic colonies and appear greenish on blood agar
a) Bacillus cereus

b) Streptococcus pneumoniae
c) Staphylococcus aureus
d) Streptococcus pyogenes 

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

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 flagella and shows a positive motility test?
a) Staphylococcus aureus
b) Yersinia pestis
c) Klebsiella pneumoniae
d) Proteus vulgaris

24) The metabolic reactions by bacteria can be observed by performing different biochemical tests, this helps in the identification and classification of bacteria.

Which of the following biochemical test shows 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) …...............................is a gram-positive, non-spore-forming virulent foodborne bacillus. It can grow at refrigeration temperatures in raw meat and vegetables, unpasteurized milk, and cheese.
a) Bacillus subtilis
b) Clostridium botulinum
c) Listeria monocytogenes
d) Yersinia pestis

27)Which of the following bacteria exhibits beta hemolysis on blood agar plates?
a) Bacillus anthracis
b) Proteus vulgaris
c) Streptococcus pyogenes
d) Candida albicans

28) All of the statements regarding Bacillus anthracis are true, Except
a) Causative agent of smallpox
b) Colonies are non-hemolytic when grown on Blood agar

c) Gram positive, spore-forming bacteria
d) Transmitted to humans through animals

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) …................................is a type of fungus that is a member of natural gut flora and is known to be a common cause of skin, vaginal, and 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 (MSA) 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 a primary media 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

Answers:

1.  b) Staphylococcus aureus

2. d) Streptococcus pyogenes, is 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. b) Enriched media. Enriched media are formulated with additional nutrients to support the growth of fastidious or nutritionally demanding bacteria that may not grow well on basic media. Examples include blood agar, which contains blood components like red blood cells.

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. It is a parasitic infection that 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 Diplococci, N. 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 pyogenes, is 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 trachomatis, is 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. b) Streptococcus pneumoniae. S. pneumoniae colonies are alpha-hemolytic and appear greenish on blood agar, the colony characteristics can aid in identifying the causative agent of an infection.

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 production, hemolytic 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. c) Listeria monocytogenes. L. monocytogenes is a pathogenic bacterium that can cause a serious foodborne illness called listeriosis, it can be transmitted through the consumption of contaminated food, such as unpasteurized dairy products, raw vegetables, and undercooked meats.

27. c) Streptococcus pyogenes. The bacteria completely lyses (beta hemolysis) red blood cells surrounding the colonies, creating a clear zone.

28. a) Causative agent of smallpox. The bacteria causes anthrax, a serious infectious disease that can affect humans and animals.

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 anthracis, and (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