BACTERIOLOGY (COMLEX-USA LEVEL
1) QUESTIONS AND ANSWERS WITH
SOLUTIONS 2024
(1) Mycobacteria (2) Nocardia; Ziehl Neelsen stain - ANSWER What two bacteria are said to be acid fast
(+)? What is another name for the acid fast stain?
Acid fast (Ziehl Neelsen) stain - ANSWER What type of stain is used to detect bacteria with waxy cell
walls?
Cryptococcus - ANSWER What fungus is detected by india ink?
Polysaccharides; Iron - ANSWER A periodic acid-schiff stain test for the presence of _____, while a
prussian blue stain tests for the presence of _____.
Amyloid - ANSWER What does a congo red stain detect?
Red, Apple-green - ANSWER When viewed under a light microscope, what color does congo red stain
amyloid? What color is it when viewed under a polarizing light microscope?
Blue-violet; Pink-red - ANSWER After a gram stain, what color are gram (+) organisms? Gram (-)?
(1) Crystal violet (2) Gram's iodine (3) Alcohol (4) Safranin - ANSWER What are the four steps of gram
staining?
Mycoplasma - ANSWER What is the only bacteria without a cell wall?
Chlamydia - ANSWER What is the only bacteria without peptidoglycan in its cells wall?
Gram (-) - ANSWER Would you expect to find lipopolysaccharide (LPS) in gram (+) or gram (-) bacteria?
,(1) Bacillus (2) Clostridium - ANSWER What two bacteria have the ability to form spores?
(1) Streptococcus pneumoniae (2) Neisseria meningitidis (3) Haemophilus influenzae - ANSWER What
are the three clinically important encapsulated bacteria?
Lipid A - ANSWER What component of lipopolysaccharides makes up the endotoxin found in gram (-)
bacteria?
Gram (-) - ANSWER Are O antigens indicative of gram (+) or gram (-) bacteria?
(1) Stimulates macrophages (2) Activates the alternative pathway of complement (3) Activates factor 12
(hageman) of the coagulation cascade - ANSWER What are the three primary activities of endotoxin
(lipid A)?
Exotoxin; Endotoxin - ANSWER Which is more antigenic endotoxin or exotoxin? Which is more heat
stable?
Tetanus toxin; Mucle spasms - ANSWER What major exotoxin blocks glycine and GABA release? What is
its effect?
Tetanus toxin; Clostridium tetani - ANSWER What major exotoxin causes lockjaw, risus sardonicus, and
eventually paralysis of respiratory muscles? What bacterium is it associated with?
Botulinum toxin; Muscle paralysis (flaccid) - ANSWER What major exotoxin blocks the release of Ach at
neuromuscular junctions? What is its effect?
Botulinum toxin; Clostridium botulinum - ANSWER What is the most potent exotoxin? What bacterium is
it associated with?
Botulinum toxin - ANSWER What major exotoxin causes constipation followed by descending flaccid
paralysis?
, Diphtheria toxin; Corynebacterium diphtheria - ANSWER What major exotoxin features pharyngeal
pseudomembrane development, myocarditis, and muslce weakness/paralysis? What bacterium is it
associated with?
(1) Throat (2) Heart (3) Neural tissue - ANSWER What three parts of the body are most affected by
diphtheria toxin?
(1) Clostridium perfingens (2) Staphylococcus aureus - ANSWER What are the two bacteria that produce
alpha toxin?
Clostridium perfingens; Staphylococcus aureus - ANSWER Alpha toxin is produced by two different
organisms. Which organism causes marked skin necrosis? Which organism causes marked necrosis of
deep tissues?
Staphylococcus aureus; Superantigen (binds directly to MHC II proteins) - ANSWER What bacterium
produces toxic shock syndrome toxin (TSST-1)? What is the mechanism of action of TSST-1?
Toxic shock syndrome toxin (TSST-1) (2) Enterotoxin A-F - ANSWER What are the two super antigens
produced by staphylococcus aureus?
Cholera toxin; Massive watery diarrhea - ANSWER What major exotoxin binds to gangliosides in intestinal
cell membranes? What is its effect?
Pertussis toxin; Bordetella pertussis - ANSWER What major exotoxin causes whooping cough? What
bacterium is it associated with?
Pertusis (Whooping cough) - ANSWER What is the only bacterial infection known to cause
lymphocytosis?
(1) Heat labile (LT) (2) Heat stable (ST) - ANSWER What are the two major enterotoxins produced by E.
coli?
1) QUESTIONS AND ANSWERS WITH
SOLUTIONS 2024
(1) Mycobacteria (2) Nocardia; Ziehl Neelsen stain - ANSWER What two bacteria are said to be acid fast
(+)? What is another name for the acid fast stain?
Acid fast (Ziehl Neelsen) stain - ANSWER What type of stain is used to detect bacteria with waxy cell
walls?
Cryptococcus - ANSWER What fungus is detected by india ink?
Polysaccharides; Iron - ANSWER A periodic acid-schiff stain test for the presence of _____, while a
prussian blue stain tests for the presence of _____.
Amyloid - ANSWER What does a congo red stain detect?
Red, Apple-green - ANSWER When viewed under a light microscope, what color does congo red stain
amyloid? What color is it when viewed under a polarizing light microscope?
Blue-violet; Pink-red - ANSWER After a gram stain, what color are gram (+) organisms? Gram (-)?
(1) Crystal violet (2) Gram's iodine (3) Alcohol (4) Safranin - ANSWER What are the four steps of gram
staining?
Mycoplasma - ANSWER What is the only bacteria without a cell wall?
Chlamydia - ANSWER What is the only bacteria without peptidoglycan in its cells wall?
Gram (-) - ANSWER Would you expect to find lipopolysaccharide (LPS) in gram (+) or gram (-) bacteria?
,(1) Bacillus (2) Clostridium - ANSWER What two bacteria have the ability to form spores?
(1) Streptococcus pneumoniae (2) Neisseria meningitidis (3) Haemophilus influenzae - ANSWER What
are the three clinically important encapsulated bacteria?
Lipid A - ANSWER What component of lipopolysaccharides makes up the endotoxin found in gram (-)
bacteria?
Gram (-) - ANSWER Are O antigens indicative of gram (+) or gram (-) bacteria?
(1) Stimulates macrophages (2) Activates the alternative pathway of complement (3) Activates factor 12
(hageman) of the coagulation cascade - ANSWER What are the three primary activities of endotoxin
(lipid A)?
Exotoxin; Endotoxin - ANSWER Which is more antigenic endotoxin or exotoxin? Which is more heat
stable?
Tetanus toxin; Mucle spasms - ANSWER What major exotoxin blocks glycine and GABA release? What is
its effect?
Tetanus toxin; Clostridium tetani - ANSWER What major exotoxin causes lockjaw, risus sardonicus, and
eventually paralysis of respiratory muscles? What bacterium is it associated with?
Botulinum toxin; Muscle paralysis (flaccid) - ANSWER What major exotoxin blocks the release of Ach at
neuromuscular junctions? What is its effect?
Botulinum toxin; Clostridium botulinum - ANSWER What is the most potent exotoxin? What bacterium is
it associated with?
Botulinum toxin - ANSWER What major exotoxin causes constipation followed by descending flaccid
paralysis?
, Diphtheria toxin; Corynebacterium diphtheria - ANSWER What major exotoxin features pharyngeal
pseudomembrane development, myocarditis, and muslce weakness/paralysis? What bacterium is it
associated with?
(1) Throat (2) Heart (3) Neural tissue - ANSWER What three parts of the body are most affected by
diphtheria toxin?
(1) Clostridium perfingens (2) Staphylococcus aureus - ANSWER What are the two bacteria that produce
alpha toxin?
Clostridium perfingens; Staphylococcus aureus - ANSWER Alpha toxin is produced by two different
organisms. Which organism causes marked skin necrosis? Which organism causes marked necrosis of
deep tissues?
Staphylococcus aureus; Superantigen (binds directly to MHC II proteins) - ANSWER What bacterium
produces toxic shock syndrome toxin (TSST-1)? What is the mechanism of action of TSST-1?
Toxic shock syndrome toxin (TSST-1) (2) Enterotoxin A-F - ANSWER What are the two super antigens
produced by staphylococcus aureus?
Cholera toxin; Massive watery diarrhea - ANSWER What major exotoxin binds to gangliosides in intestinal
cell membranes? What is its effect?
Pertussis toxin; Bordetella pertussis - ANSWER What major exotoxin causes whooping cough? What
bacterium is it associated with?
Pertusis (Whooping cough) - ANSWER What is the only bacterial infection known to cause
lymphocytosis?
(1) Heat labile (LT) (2) Heat stable (ST) - ANSWER What are the two major enterotoxins produced by E.
coli?
