MCQs on Bacterial Pathogenesis: Medical Microbiology

Key aspects of Bacterial pathogenesis/ General steps in bacterial pathogenesis
    • Adherence and Colonization 
    • Invasion
    • Immune Evasion
    • Toxin Production
    • Nutrient Acquisition
    • Host Cell Manipulation
    • Inflammation and Tissue Damage 

                     Multiple Choice Questions on Bacterial Pathogenesis
      Figure 1: Phagocyte activity and possible outcomes of phagocyte-bacterial interactions                                     (Source/Reference: Bailey & Scott’s Diagnostic Microbiology)

1) Which of the following microorganism is the major inhabitant of the human skin?
a) Escherichia coli
b) Staphylococcus epidermidis
c) Staphylococcus aureus
d) Streptococcus pyogenes

2) Select all the medically important bacteria which are frequently isolated pathogen  human infections?
a) Enteric bacteria 
b) Pseudomonas spp
c) Plasmodium spp
d) Staphylococcus spp
e) Mucor spp
f) Mycobacterium spp

3) All of the following pathogens are the major congenital pathogens that are transmitted from infected mother to baby, Except?
a) Treponema pallidum
b) Zika virus
c) Herpesvirus
d) Clostridium perfringens

4) Which of the following cocci-shaped bacteria usually grow in pairs?
a) Klebsiella spp
b) Neisseria spp
c) Pseudomonas spp
d) Clostridium spp
e) Nocardia spp

5) Which of the following microbe can live only inside the cell (obligate intracellular pathogen)?
a) Salmonella
b) Mycobacterium
c) Rickettsia
d) Vibrio

6)The upper respiratory tract of the human body typically harbors ..................................... as part of its normal flora, but an excessive proliferation of these bacteria can result in respiratory tract infections.
a) Lactobacillus acidophilus
b) Streptococcus spp
c) Vibrio cholerae
d) Clostridium difficile

7) Which of the following bacteria releases an endotoxin that causes muscular paralysis and ultimately may lead to infection of nervous system?
a) Clostridium botulinum
b) Bacillus cereus
c) Streptococcus pyogenes
d) Salmonella typhi

8) Which enzyme produced by Staphylococcus spp. is involved in the bacteria's defense mechanisms?
a) Coagulase
b) Lipase
c) Hyaluronidase
d) Proteases

9) Which of the following bacteria is predominantly present as a normal flora in the urogenital tract of a mother and a newborn female infant?
a) Candida albicans
b) Lactobacillus acidophilus
c) Histoplasma capsulatum
d) Neisseria gonorroheae

10) Which of the following gram positive bacteria is the causative pathogen for infection known as 'lock jaw'?
a) Clostridium tetani
b) Neisseria gonorroheae 
c) Yersinia pestis
d) Mycobacterium leprae

11) Name the bacterial pathogen transmitted to humans by the bite of fleas and can cause a serious and deadly infection
a) Salmonella typhi
b) Yersinia pestis
c) Shigella dysenteriae
d) Escherichia coli

12) Some bacteria and fungi need an iron receptors molecule for their growth which is an important virulence factor of bacterial pathogenesis, what is it called?
a) Siderophores
b) Ionophores
c) Siderocytes
d) None of the above

13) Which of the following is the example of toxin produced by Streptococcus pyogenes?
a) Cyanotoxin
b) Endotoxins
c) Pyrogenic toxin (exotoxins)
d) Shiga like toxin

14) Name the bacteria that is a common cause of toxic shock syndrome infection due to the release of the toxins.
a) Staphylococcus epidermidis
b) Staphylococcus aureus
c) E.coli
d) Yersinia pestis

15) Catalase test is one of the primary microbiological test used for the identification of the enzyme catalase in bacterial cells and differentiating various bacteria.
Which of the following is catalase negative bacteria?
a) E. Coli
b) Bacillus subtilis
c) Staphylococcus aureus
d) Streptococcus agalactiae

16) Staphylococcus aureus releases various types of toxins that increase the virulence of the bacteria, Select all the toxins released by S. aureus:
a) Aflatoxin
b) Mycotoxins
c) Leukocidins
d) Enterotoxins

17) Which pathogen is a major cause of dental disease?
a) Staphylococcus epidermidis
b) Streptococcus mutans
c) Staphylococcus aureus
d) Streptococcus agalactiae

18) The bacteria that commonly causes an eye infection is.............................
a) Chlamydia trachomatis
b) Staphylococcus aureus
c) Streptococcus pneumoniae
d) Streptococcus sanguinis

19) The most significant bacteria found in acne is .................................acnes.
a) Staphylococcus
b) Streptococcus
c) Propionibacterium
d) Bacillus

20) Which of the following bacteria is predominantly present as normal flora in urine?
a) Escherichia coli
b) Staphylococcus epidermidis
c) Staphylococcus aureus
d) Streptococcus pyogenes

21) The virulence factors of a bacteria are the important constituents of the bacteria that help in invading the host and initiating the infection. 
Select all the important virulence factors which help in the process of bacterial pathogenesis:
b)Exotoxins and endotoxins
c)Pili/ fimbriae
e) All of the above

22) Name the most possible bacteria associated with the opportunistic infections that occur in patients who have cystic fibrosis
a) Staphylococcus aureus
b) Pseudomonas aeruginosa
c) Chlamydia trachomatis
d) Candida albicans

23) Select all the microorganisms which are commonly transmitted to humans by the vectors such as ticks and fleas.
a) Rickettsia spp
b) Yersinia spp
c) Borrelia spp
d) Bacillus spp

24)Which of the following toxins releasing bacteria is frequently encountered as causative agents of human gastroenteritis?
a) Cryptococcus neoformans
b) Streptococcus pneumoniae
c) Salmonella typhi
d) Staphylococcus aureus

25) Identify the bacterial pathogen that commonly transmitted to humans through the consumption of contaminated food can invade the skin and lead to tissue damage
a) Rhizopus stolonifer
b) Bacillus cereus
c) Clostridium perfringens
d) Proteus mirabilis

Multiple Choice Answer Review:
1- b) Staphylococcus epidermidis

2-a), b), d), and f). c) Plasmodium spp is a parasite, a causative agent of malaria, e) Mucor spp is a fungi.
3- d) C. perfringens, is a bacteria that causes foodborne illness and most commonly found on raw meat and poultry.

4-b) Neisseria spp, usually grows in pair (diplococci). a) Klebsiella spp, c) Pseudomonas spp, d) Clostridium spp and e) Nocardia spp are rod shaped (bacilli) bacteria.

5-c) Rickettsia spp

6- b) Streptococcus spp, is a normal flora of upper respiratory tract, overgrowth of the bacteria results in infection of the respiratory tract. a) Lactobacillus acidophilus is a normal flora of intestine and vagina, c) Vibrio cholerae is a bacterial pathogen that causes foodborne illness and d) Clostridium difficile is a normal flora of the colon, overgrowth of the bacteria leads to inflammation of the colon, it can also be transmitted from person to person by spores.

7-a) Clostridium botulinum, is a bacteria that produces a potent neurotoxin responsible for the development of botulism.

8-d) Coagulase. Coagulase enzyme promotes the formation of blood clots and shields Staphylococcus spp from the host's immune system, it is an important factor in the bacterium's pathogenicity and its ability to cause diseases such as skin and soft tissue infections, and more serious conditions like septicemia and endocarditis.

9-b) Lactobacillus acidophilus, a) Candida albicans is a yeast, c) Histoplasma capsulatum is a dimorphic fungus, d) Neisseria gonorroheae is a diplococcus bacteria causes gonorrhea that is a sexually transmitted disease.

10-a) Clostridium tetani, a neurotoxin producing pathogen of  that causes Tetanus, also known as 'lock jaw' infection. b) Neisseria gonorroheae, c) Yersinia pestis and d) Mycobacterium leprae are gram negative bacteria.

11-b) Yersinia pestis. a) Salmonella typhi, c) Shigella dysenteriae and d) Escherichia coli are bacteria that causes foodborne illnesses.

12-a) Siderophores, Siderophores are small molecules produced by microorganisms, including bacteria and fungi. They function as a chelating agents, meaning they bind tightly to iron ions and form complexes that can be taken up by the microorganisms through specific transport systems on their cell membranes.

13-c)Pyrogenic toxin (exotoxins). S. pyogenes produces a family of pyrogenic exotoxins, including pyrogenic exotoxin A (SpeA) and pyrogenic exotoxin B (SpeB). These toxins are superantigens that stimulate a massive release of pro-inflammatory cytokines from immune cells, leading to fever, rash, and toxic shock-like symptoms in certain streptococcal infections.

14-b) Staphylococcus aureus, the bacteria may normally exist on a person's body and does not cause infection. It can cause infections as a result of another infection, such as pneumonia or skin wounds, the bacteria can penetrate into the bloodstream and cause infections.

15-d)Streptococcus agalactiae. Catalase is an enzyme that catalyzes the breakdown of hydrogen peroxide (H2O2) into water (H2O) and oxygen (O2).

16-c), and d). Leukocidins are produced by certain pathogenic bacteria, primarily Staphylococcus and Streptococcus species, enterotoxins are heat-stable that cause foodborne outbreaks.
a) Aflatoxin and b) Mycotoxins are fungal toxins.

17-b) Streptococcus mutans

18-a) Chlamydia trachomatis, trachoma infection by C. trachomatis is a severe eye infection that can lead to blindness if left untreated.

19-c) Propionibacterium. P. acnes is part of the normal microbial flora on the skin. When hair follicles become clogged with oil (sebum) and dead skin cells, it multiplies within the clogged hair follicles and produces metabolic byproducts, as a result immune response is activated that can lead to inflammation, redness, and acnes.

20-a) Escherichia coli
21-f) All of the above
22-b)P. aeruginosa

23-a), b), and c). d) Bacillus spp commonly causes foodborne illnesses that is transmitted to humans through consumption of contaminated water and food.

24-c) Salmonella typhi. It is a common gastroenteritis pathogen that is transmitted to humans through consumption of contaminated food and water.
b) Streptococcus pneumoniae is a gram positive bacteria that causes respiratory infections and c) Cryptococcus neoformans is a fungus that do not produce toxins.

25- c)Clostridium perfringens, it is a gram positive bacterium that can cause various infections, including food poisoning and gas gangrene (tissue damage). 
a) Rhizopus stolonifer is a fungal pathogen and common in breads. b) Bacillus cereus is a gram positive bacteria commonly causing foodborne illness, d) Proteus mirabilis is a gram negative bacteria, a common cause of urinary tract infection (UTI).