Medical Microbiology: Enteric Bacteria MCQ

Multiple Choice Question on Enteric Bacteria (E. coli, Salmonella spp and Shigella spp)

1) Intestines of humans and other mammals are the natural habitats of enteric organisms, a large family of bacteria is present as a normal flora, which of the following is not the normal flora of the intestine?
a) Escherichia spp
b) Salmonella spp
c) Staphylococcus spp
d) Proteus spp

2) Some enteric bacteria are part of normal inhabitants and incidentally cause disease but others such as.........are regularly pathogenic for humans.
a) Pseudomonas spp
b) Streptococcus spp
c) Salmonella spp
d) Proteus spp

3) All are the general characteristics of enteric bacteria, EXCEPT?
a) Catalase positive
b) Non-spore forming
c) Grow in media with bile salts
d) Nitrate negative

4) Enteric bacteria are mainly classified based on their ability to ferment various sugars including lactose. Which of the following bacteria is a non-lactose fermenter?
a) Klebsiella spp
b) Salmonella spp
c) Enterobacter spp
d) Citrobacter spp

5) Escherichia coli is one of the major enteric bacteria that causes diarrhea and is characterized according to its virulence properties. All are the types of E. coli, EXCEPT?
a) Enterohemorrhagic E. coli
b) Enteropathogenic E. coli
c) Enterotoxigenic E. coli
d) Enterolysogenic E. coli

6) After the bacteria is ingested, enteropathogenic E. coli (EPEC) attaches to the mucosal cells of the small intestine which results in malabsorption and diarrhea. Symptoms include watery diarrhea, vomiting, non-bloody stools which lasts for a short duration mostly 1-3 days. What are the two important factors of pathogenesis?
a) The chromosomal locus of enterocyte effacement (LEE)
b) The bundle-forming pilus encoded by a plasmid adherence factor (EAF)
c) Both of the above
d) None of the above

7) Enteroinvasive E. coli (EIEC) are nonmotile, non-lactose, or late lactose fermenters which are predominantly found in developing countries infecting children and travelers. Which of the following infection is similar to EIEC infection?
a) Bacillary dysentery
b) Shigellosis
c) Traveler’s diarrhea
d) Enteric fever

8) Enterobacteriaceae expresses a variety of virulent antigens, all of the following are the antigens, EXCEPT?
a) O antigen
b) K and Vi antigen
c) H antigen
d) D antigen

9) E. coli is one of the most common enteric bacteria in urinary tract infection (UTI) followed by Proteus mirabilis. All of the following is the characteristic feature Proteus mirabilis, EXCEPT?
a) Facultative aerobes
b) Urease positive
c) Motile
d) Citrate positive

10) Shigellosis is caused by Shigella dysenteriae in humans causing fever, abdominal cramps, diarrhea sometimes with blood. The infection is attributed to the …........ activity of Shiga toxin which increases the severity by tissue invasion of the large intestine.
a) Exotoxic
b) Enterotoxic
c) Cytotoxic
d) Neurotoxic

11) Enterotoxigenic E. coli (ETEC) produces two major types of toxins, heat-labile (LT) and heat-stable (ST) toxins. LT or cholera-like toxin activates adenylate cyclase (cAMP) whereas ST activates.............causing Travelers’ diarrhea.
a) Ribosomal dysfunction
b) Decarboxylase reaction
c) Guanylate cyclase
d) Fermentation of sugars

12) Which of the following is a rapid lactose fermenter, motile enteric bacteria, and is the major cause of a broad range of hospital-acquired infections such as pneumonia, urinary tract infections, and wound and device infections?
a) Streptococcus pyogenes
b) Pseudomonas aeruginosa
c) Mycobacterium tuberculosis
d) Enterobacter aerogenes

13) Salmonella typhi enter the human body through an oral route penetrating into the intestine and reaching the lymphatics and the bloodstream ultimately causing the infection "Typhoid".Which of the following are the most correct examples of the region of infection caused by the S. typhi?
a) Mononuclear phagocytic cells in the liver and Peyer’s patches of the small intestine
b) Liver, spleen, lymph nodes, and large intestine
c) Isolated follicles and Peyer’s patches of a large intestine
d) None of the above

14) Which type of salmonellae is primarily infectious for humans?
a) Salmonella typhi A
b) Salmonella paratyphi A, B, and C
c) Salmonella paratyphi A and B
d) Salmonella paratyphi A
15) The symptoms of typhoid fever develop in one to three weeks after exposure to S. typhi, all of the given below are the major symptoms, EXCEPT?
a) Weight gain
b) Headache
c) High-grade fever
d) Rashes

16) Which of the following Shigella spp produces a heat-labile exotoxin that affects both the gut and central nervous system resulting in diarrhea and meningismus?
a) Shigella sonnie
b) Shigella dysenteriae type 1
c) Shigella dysenteriae type 2
d) Shigella dysenteriae type 3

17) S. enteritidis and S. typhimurium causes enterocolitis and gastroenteritis in humans. What is the most common food for the transmission of this infection?
a) Raw meat
b) Eggs
c) Canned beans
d) Yogurt

18) The biochemical test used to identify and determine the ability of bacteria to convert tryptophan into indole is?
a) IMViC test
b) MRVP test
c) TSI test
d) Citrate test

19) Which one is not the selective culture media for salmonellae and shigellae?
a) Deoxycholate citrate agar
b) Xylose-lysine decarboxylase agar
c) Salmonella –Shigella agar
d) Blood agar

20) The Widal test is used for the detection of Salmonella typhi and other subspecies. This test is based on the principle where?
a) the antigens are detected using the neutralization assay
b) the antigen combines with its soluble antibody and form a lattice and develops a visible precipitate
c) the antigens bind to RBCs and form the agglutination
d) None of the above

Multiple Choice Answers