Microbiology BIO 3304 Chapter 21

Hemolytic uremic syndrome is caused by Staphylococcus aureus.

False

Horizontal gene transfer by bacteriophage is thought to be a very rare mechanism.

False

The capsule is considered a virulence factor for many pathogens. Explain how the capsule aids the pathogen in establishing the disease process.

Many bacterial pathogens possess a capsule to help them avoid phagocytosis and lysis by complement. Proper opsonization is hindered because the capsule is so thick that antibody and complement will be buried in the capsule and not recognized by the phagocyte for proper binding to the pathogen. Reduced phagocytosis will also delay the specific immune response because the processing of pathogen antigens by macrophage and presentation to T-cells will not occur properly. Thus, the antibody response will be delayed and the antibody-antigen complex will be unable to activate complement by the classical pathway for the formation of the membrane attack complex (MAC). All of these events allow the pathogen to go unchecked for a longer period of time thus enabling it to firmly establish the disease process.

The scientific name of a causative agent of bacterial meningitis is ____________ meningitidis.

Neisseria

Describe the mechanism of tetanus toxin in causing spastic paralysis.

Tetanus toxin is an A-B toxin and a neurotoxin. The toxin acts on inhibitory neurons, which normally function to stop muscle contraction through the release of the inhibitory neurotransmitters glycine and gamma-aminobutyric acid (GABA) that block acetylcholine release. The B subunit of the toxin binds to the inhibitory neuron and the A subunit enters the neuron to block the release of glycine and GABA. The result will be continuous acetylcholine release and continuous muscle contraction which can be so powerful that tendons, and even bones, may snap.

A toxin that is part of the cell structure and usually found in the surface elements of the cell is called an endotoxin.

True

Cellulitis is inflammation of the connective tissue and may be caused by Streptococcus pyogenes.

True

Enterotoxins produced by Staphylococcus aureus are weak superantigens.

True

Many pathogenic bacteria adhere to host cells via fimbriae.

True

Type III secretion systems of Gram negative bacteria allow for the direct secretion of toxin into the target cell.

True

How does the bacterial capsule act as a virulence factor? a) It prevents both phagocytosis and complement activation. b) It prevents complement activation. c) It prevents phagocytosis only. d) It acts as an enterotoxin. e) It allows the bacterium to bind to the cell surface and lyse the host cell.

a) It prevents both phagocytosis and complement activation.

Lipoteichoic acids are associated with which of these bacteria? a) Staphylococcus aureus b) Escherichia coli c) Shigella sonnei d) Klebsiella pneumoniae e) Neisseria gonorrhoeae.

a) Staphylococcus aureus

Perfringolysin is produced by Clostridium perfringens. What is its mechanism to cause lysis? a) Through pore formation within the host cell membrane. b) By disruption of protein synthesis. c) By disruption of membrane synthesis. d) Through the breakdown of membrane phospholipids. e) By destroying host cell membrane proteins.

a) Through pore formation within the host cell membrane.

For most pathogenic bacteria, what is the first step it takes to facilitate entry into its host? a) attachment b) toxin production c) protease production d) sequestering iron e) lysis of the host cell

a) attachment

Streptococcus pyogenes is not efficiently opsonized for phagocytosis because of this component of its capsule. a) hyaluronic acid b) lipid A c) lipopolysaccharides d) teichoic acid e) Protein A

a) hyaluronic acid

What directly causes the damage during an active Mycobacterium tuberculosis infection? a) A potent cytolysin that targets alveolar macrophages. b) A cell-mediated inflammatory response. c) A cytolysin that destroys lung tissue. d) Growth of the bacterium in macrophages. e) An exotoxin that enters into the bloodstream and targets heart muscle.

b) A cell-mediated inflammatory response.

Which of these are associated with Type III secretion systems? a) Gram positive bacteria b) Gram negative bacteria c) Staphylococcus aureus d) Streptococcus pyogenes e) pathogenic fungi

b) Gram negative bacteria

What is the primary effect of lipopolysaccharide (LPS) on the host? a) Attacks cells of the immune system. b) Triggers an intense inflammatory response. c) Acts as a neurotoxin. d) Causes diarrhea. e) Lyses epithelial cells.

b) Triggers an intense inflammatory response.

Staphylococcus aureus produces a potent exotoxin which causes cell damage that induces a very strong inflammatory response in the host. What is this toxin? a) pneumolysin b) α-toxin c) enterotoxin d) streptolysin O e) Protein A

b) a-toxin

The DTaP vaccine is designed to protect against which diseases? a) diarrhea, tetanus, and polio b) diphtheria, tetanus, and pertussis c) diarrhea, tetanus, and pertussis d) diphtheria, tetanus, and polio e) diarrhea, measles, and polio

b) diphtheria, tetanus, and pertussis

Select the example of a virulence factor that does not directly cause damage to host cells but elicits a strong, damaging inflammatory host response. a) immunoglobulin protease b) endotoxin c) cytotoxin d) fimbriae e) urease

b) endotoxin

Which of these symptoms is caused by a toxin produced by Clostridium botulinum? a) uncontrolled twitching b) flaccid paralysis c) spastic paralysis d) meningitis e) encephalitis

b) flaccid paralysis

Pathogenicity islands are blocks of genes on the bacterial chromosome that most likely arose from this process. a) spontaneous mutation b) horizontal gene transfer c) vertical gene transfer d) chemically induced mutagenesis e) mutation via gamma radiation

b) horizontal gene transfer

Which component of lipopolysaccharide is responsible for inducing a strong inflammatory response? a) phospholipid b) lipid A c) core polysaccharide d) O-antigen e) teichoic acid

b) lipid A

Which of these is NOT a mechanism of horizontal gene transfer? a) transduction b) transformation c) conjugation d) mother cell to daughter cell e) transposable elements

b) transformation

By what mechanism does the enzyme streptokinase allow Streptococcus pyogenes to spread through tissue? a) By lysing smooth muscle cells. b) By lysing skin epithelial cells. c) By breaking down fibrin clots. d) By lysing red blood cells. e) By lysing white blood cells.

c) By breaking down fibrin clots.

A person may develop strep throat several times because of the antigenic variations of this. a) teichoic acids b) capsule proteins c) M-protein d) lipopolysaccharide e) streptolysin-O

c) M-protein

Which of these virulence factors is NOT possessed by the pathogen Neisseria gonorrhoeae? a) Fimbriae for attachment. b) Secretory IgA protease. c) Production of urease. d) Endotoxin. e) The ability to change surface pilin antigens.

c) Production of urease.

Siderophores are a virulence factor because they allow the pathogen to perform what action? a) Lyse lymphocytes. b) Bind the Fc region of the antibody molecule. c) Scavenge for free iron. d) Compete with the host cells for glucose. e) Invade host cells.

c) Scavenge for free iron.

Botulinum toxin belongs to a group of toxins called A-B toxins. What does the term "A-B" refer to? a) Their antigen-binding properties. b) Their antibody-binding toxins. c) Their enzymatically active subunit and cell binding subunit. d) Their action on the brain. e) Their activation of B-cells.

c) Their enzymatically active subunit and cell binding subunit.

Staphylococcus aureus produces a fibronectin-binding protein as a virulence factor to aid in which activity? a) host cell lysis b) sequestering iron c) attachment d) toxin mediated cell inactivation e) avoiding antibodies

c) attachment

Listeriolysin is a cytolysin produced under acidic conditions by Listeria monocytogenes. What does this exotoxin allows the pathogen to do? a) lyse lymphocytes b) invade epithelial cells c) escape the endosome to avoid digestion d) lyse macrophages e) lyse neurons

c) escape the endosome to avoid digestion

Enteropathogenic and enterohemorrhagic strains of Escherichia coli attach to host cells in the intestinal lumen via this mechanism. a) fimbriae and capsule b) capsule and the surface protein intimin c) fimbriae and the surface protein intimin d) fimbriae and LPS e) LPS and capsule

c) fimbriae and the surface protein intimin

Tetanus toxin acts on inhibitory neurons by preventing the release of _________ from the neurons. a) acetylcholine b) glutamate and glutamine c) glycine and GABA d) acetylcholine and glutamate e) glycine and glutamate

c) glycine and GABA

Where is the diphtheria toxin gene located? a) A pathogenicity island. b) A conjugative plasmid. c) A transposon. d) A prophage. e) A cryptic plasmid.

d) A prophage

Neisseria meningitidis is the causative agent of meningitis. Which of these accounts for the damage caused by this bacterial infection? a) A potent exotoxin that lyses epithelial cells. b) A potent neurotoxin that targets brain cells. c) A cytolytic toxin that destroys B-cells. d) An endotoxin-induced inflammatory response. e) An exotoxin that destroys macrophages.

d) An endotoxin-induced inflammatory response.

Cattle may serve as a reservoir for E.coli strain O157:H7 because this strain does not cause any disease in cattle. This strain of E. coli can cause a potentially lethal Shiga toxin-mediated hemolytic uremic syndrome (HUS) in humans. Why don't cattle develop HUS? a) The shiga toxin is not expressed in cattle. b) E. coli is unable to effectively colonize the bovine intestine. c) A protease in the cattle destroys the toxin. d) Bovine kidney cells do not have a shiga toxin receptor. e) They produce antibody against the shiga toxin.

d) Bovine kidney cells do not have a shiga toxin receptor.

Which of these bacteria causes gangrene? a) Pseudomonas aeruginosa b) Corynebacterium diphtheriae c) Staphylococcus aureus d) Clostridium perfringens e) Bacillus subtilis

d) Clostridium perfringens

A person who has strep throat should always be treated with antibiotics to reduce the risk of sequelae. What are the two most common sequelae? a) Toxic shock syndrome and scarlet fever. b) Glomerulonephritis and scarlet fever. c) Toxic shock syndrome and pneumonia. d) Glomerulonephritis and rheumatic fever. e) Scarlet fever and rheumatic fever.

d) Glomerulonephritis and rheumatic fever.

What is the most common cause of pharyngitis and tonsillitis in children? a) Staphylococcus aureus b) Corynebacterium tuberculosis c) Mycoplasma pneumoniae d) Streptococcus pyogenes e) Streptococcus pneumoniae

d) Streptococcus pyogenes

All of the following are examples of how virulence factors facilitate establishment of disease by a pathogen EXCEPT: a) gaining entry into the host. b) evade or overcome host defenses. c) obtain nutrients from the host. d) antibiotic resistance. e) lyse host cells for nutrients.

d) antibiotic resistance.

Which cells are destroyed by hemolysins? a) lymphocytes b) macrophages c) epithelial cells d) red blood cells e) heart cells

d) red blood cells

Toxic shock syndrome caused by Staphylococcus aureus is mediated by an exotoxin that acts as a _____ . a) cytotoxin b) neurotoxin c) hemolysin d) superantigen e) superantibody

d) superantigen

What is the genus of the organism that causes pertussis? a) Corynebacterium b) Mycoplasma c) Streptococcus d) Mycobacterium e) Bordetella

e) Bordetella

Impetigo can be caused by Streptococcus pyogenes. Impetigo is a type of __________ . a) pneumonia b) sequelae c) toxic shock syndrome d) ear infection e) skin infection

e) skin infection

Exotoxins that act specifically on the intestine are called __________________.

enterotoxins

A bacterial toxin that is secreted by the cell is called a(n) _________.

exotoxin

Cytolysins are cytotoxins that act on the ________ membrane to lyse the cell.

plasma or cell or phagosome

A primary pathological feature of a Mycobacterium tuberculosis infection is the appearance of ___________ in the lungs.

tubercules

A substance produced by a pathogenic agent that enables it to gain entry into the host, avoid host defenses, or obtain nutrients is called a(n) __________ factor.

virulence