Microbiology Final Chapter 19
How does the toxin from Clostridium tetani produce its action? A) It fuses irreversibly to neuronal cytoplasmic membranes, blocking release of acetylcholine at synaptic clefts. B) The smaller polypeptide of its toxin can block the release of inhibitory neurotransmitters by inhibitory neurons in the central nervous system, causing simultaneous contraction of both muscles in an antagonistic pair. C) It is a pyrogenic toxin, which triggers a diffused rash and, later, sloughing of skin. D) It destroys tissues, including muscle and fat. E) It produces antibodies that attack the neuromuscular junctions in skeletal muscle and prevent them from relaxing.
B
Mycetoma, which is a painless long-lasting infection characterized by swelling, pus production, and draining sores, is caused by A) systemic tuberculosis. B) Nocardia. C) Actinomyces. D) penicillin-resistant staphylococci. E) cutaneous anthrax.
B
Otitis media may lead to dangerous meningitis in children due to infection with A) Streptococcus agalactiae. B) Streptococcus pneumoniae. C) Streptococcus mutans. D) Enterococcus. E) Mycoplasma pneumoniae.
B
The pathogenicity of primary tuberculosis is due to the fact that the mycobacteria A) are not phagocytized. B) prevent fusion of lysosomes with phagosomes. C) form a pseudomembrane. D) destroy helper T cells. E) are carried by macrophages to a variety of sites.
B
What is one feature that differentiates Staphylococcus aureus from other species of staphylococci? A) It has a slime layer capsule. B) It can produce coagulase. C) It can produce hyaluronidase. D) It can live on the surface of the skin and in cutaneous oil glands. E) It produces exfoliative toxins.
B
Which of the following bacteria cause Hansen's disease? A) Mycobacterium tuberculosis B) Mycobacterium leprae C) Clostridium difficile D) Listeria species E) Corynebacterium species
B
Compare and contrast the pathogenicity of Clostridium botulinum and Clostridium tetani, including mechanisms of action of their toxins and disease manifestations.
Both bacteria are anaerobic endospore-formers that produce neurotoxins. Disease results when the endospores are introduced deep into the tissues. Both neurotoxins interfere with motor control. Botulism toxin, produced by C. botulinum, binds the cytoplasmic membranes of motor neurons at the synapse and prevents the release of acetylcholine neurotransmitter and, consequently, prevents signaling to muscle cells. When muscle cells do not receive signals from motor neurons, they remain relaxed, resulting in a flaccid paralysis. Lack of motor control produces a long list of symptoms, the most serious of which is respiratory failure, because respiratory muscles can be affected by botulism toxin. Tetanus toxin, produced by C. tetani, targets inhibitory neurons, which release neurotransmitter that prevents muscle cells from responding to acetylcholine stimulation to contract. Under normal circumstances, when one muscle of an antagonistic pair is stimulated to contract, the other muscle is inhibited from contracting, allowing for normal movement by alternate flexion and extension. When tetanus toxin blocks the release of inhibitory neurotransmitter, both muscles of the antagonistic pair contract spasmodically and sometimes lock in continuous contraction, resulting in nonflaccid paralysis. Loss of control of the respiratory muscles can lead to respiratory failure. Tetanus toxin can also interfere with autonomic (involuntary) muscle control, which may result in irregular heartbeat and possibly heart failure.
Anthrax, which means "charcoal" in Greek, derives its name from A) the airborne endospores it produces. B) the staining properties of the bacillus under the microscope. C) the black eschars it produces on human skin. D) its ability to invade the bloodstream and produce toxemia. E) the high mortality it causes in infected individuals.
C
Listeria's virulence is directly related to its ability to A) produce powerful toxins. B) form very resistant endospores. C) live within cells and thus avoid exposure to the immune system of its host. D) easily become a pathogen in humans. E) resist most antimicrobial agents.
C
What differentiates virulent strains of Streptococcus pneumoniae from nonvirulent strains? A) the species-specific teichoic acid present in its cell wall B) the type of Lancefield antigen it produces C) the presence of a polysaccharide capsule that protects it from digestion after endocytosis D) the type of toxins it produces E) the extent of the hemolytic zone it produces when it is grown on blood agar
C
Which of the following bacteria divide by "snapping division" in which daughter cells remain attached in characteristic V-shapes? A) staphylococci B) enterococci C) Corynebacterium D) Listeria E) Mycobacterium
C
Which of the following diseases is considered an autoimmune disease triggered by bacterial infection? A) glomerulonephritis caused by the group A streptococci B) scarlet fever C) rheumatic fever D) impetigo E) toxic shock syndrome
C
Which of the following staphylococcal virulence factors produce the signs and symptoms of scalded skin syndrome? A) hyaluronidase B) staphylokinase C) exfoliative toxin D) leukocidin E) coagulase
C
________ media was developed especially to culture Corynebacterium diphtheriae.
Loffler's
________ is resistant to numerous antimicrobial agents; therefore, vancomycin must be used for these infections.
MRSA
In its role in the development of acne, ________ typically grows in sebaceous glands of the skin.
Propionibacterium
Staphylococcus aureus can produce a toxin that dissolves the desmosomes that hold the adjoining cytoplasmic membranes of cells together and causes the patient's skin cells to separate from each other.
True
The respiratory infection known as "walking pneumonia" is caused by Mycoplasma pneumoniae.
True
The neurotoxins of Clostridium botulinum produce ________ paralysis by preventing muscle contraction.
flaccid
When streptococcal infections involve the skin and surrounding lymph nodes, triggering pain and inflammation, the condition is known as ________.
erysipelas
The ability to produce ________ enables Staphylococcus aureus to penetrate and spread through tissues.
hyaluronidase
A "summer cold" that lasts for weeks and is characterized by sore throat, mild fever, dry cough, and malaise may be ________.
primary atypical pneumonia
A sample of fluid from the lungs contains microbes that grow in filaments, and the filaments tend to align with one another. The cells stain poorly in the Gram stain and are a pink-red when acid-fast stained. The bacteria in the sample are A) Mycobacterium species. B) Mycoplasma species. C) Nocardia species. D) Actinomyces species. E) not identifiable with this information.
A
During a stay in the hospital, an accident victim develops symptoms of bacteremia. A blood sample shows the presence of Gram-positive cocci in pairs. Lab tests determine that the bacteria are nonhemolytic and bile salt tolerant. The bacteremia is likely due to A) Enterococcus. B) Mycoplasma. C) Staphylococcus. D) Streptococcus. E) Listeria.
A
Mycoplasma pneumoniae is distinguished from other members of the genus A) because it is strictly aerobic. B) because it is a facultative anaerobe. C) by its lack of cytochromes. D) by the presence of sterols in its cytoplasmic membrane. E) by the presence of a rudimentary cell wall.
A
Streptococci are frequently classified by A) the bacteria's Lancefield antigen. B) the type of enzymes the bacteria produce. C) their staining properties. D) their ability to produce catalase. E) the diseases they produce.
A
The pus from an abscess in a patient's jaw contains microbes that form yellowish grainy masses and appear filamentous under the microscope. Neither antifungal medication nor a normal course of antibiotics has been effective in treating the infection. The abscess is likely the result of infection with A) Actinomyces. B) Mycobacterium. C) Nocardia. D) Propionibacterium. E) Streptococcus.
A
What is the most common disease caused by Propionibacterium? A) acne B) food poisoning C) pneumonitis D) folliculitis E) a sty
A
Which of the following bacteria can cause life-threatening pseudomembranous colitis? A) Clostridium difficile B) Staphylococcus aureus C) Streptococcus pyogenes D) Enterococcus species E) Clostridium botulinum
A
Which of the following has been historically classified as Gram-negative bacteria but is genetically more similar to low G + C Gram-positive bacteria? A) mycoplasmas B) Mycobacterium C) Clostridium D) Propionibacterium E) Nocardia
A
Which of the following statements about Bacillus anthracis is FALSE? A) It is primarily a disease of humans. B) It produces endospores. C) It has a capsule. D) It normally dwells in the soil and can survive in the environment for centuries or longer. E) It can be lethal even after treatment because antimicrobial drugs do not inactivate accumulated anthrax toxin.
A
Which of the following statements concerning tetanus is FALSE? A) Its only source is from deep puncture wounds from rusty nails. B) Its toxin causes simultaneous contraction of both muscles in an antagonistic pair. C) It is a small, motile, obligate anaerobe. D) It produces a terminal endospore that gives the cell a distinctive "lollipop" appearance. E) Its diagnostic feature is characteristic muscle contractions, which are often noted too late to save the patient.
A
Which of the following statements regarding Streptococcus pyogenes is FALSE? A) It produces protein A, which inhibits opsonization. B) It is beta-hemolytic. C) It has group A Lancefield antigens. D) It produces streptolysins. E) It can be lysogenized by a temperate bacteriophage to produce erythrogenic toxins.
A
Which of the following streptococci is associated with dental caries? A) viridans streptococci B) Streptococcus pyogenes C) Streptococcus pneumoniae D) Streptococcus equisimilis E) Streptococcus arginosus
A
In countries where tuberculosis is common, health care workers are vaccinated with ________, which contains attenuated Mycobacterium bovis bacteria.
BCG
The aerobic endospore-former ________ is a strict pathogen of humans and animals.
Bacillus anthracis
Which of the following statements about "flesh-eating" streptococci is FALSE? A) It is caused by a group A streptococcus. B) It is also known as necrotizing fasciitis because it travels along the fascia. C) It causes death in over 50% of cases. D) It is considered a common complication of pyoderma. E) It involves toxemia.
D
Why would Clostridium botulinum be a good microorganism to use for biological warfare?
Clostridium botulinum is an anaerobic, endospore-forming, Gram-positive bacillus that is common in soil and water. Its endospores survive improper canning of food. In canned food, they germinate and produce neurotoxins. Heating the food does not inactivate the neurotoxins. If the contaminated canned food is ingested, it produces a disease known as botulism. The botulism toxins bind irreversibly to neuronal cytoplasmic membranes and prevent the release of acetylcholine in the neuromuscular junction clefts. This leads to flaccid paralysis of the muscles affected. Eventually, the paralysis affects the diaphragm and leads to death due to respiratory failure. Scientists consider botulism toxin one of the deadliest toxins in the world. Even a small taste of contaminated food can cause full-blown disease and death. Therefore, a small amount of this toxin could wipe out large populations and would be ideal for biological warfare. Even when a person survives, recovery occurs slowly over several months.
Bacterial food poisoning resulting from ________ contamination is characterized by watery diarrhea accompanied by intestinal cramping but not fever, and it resolves in about a day.
Clostridium perfringens
Palisade cell arrangements are characteristic of ________.
Corynebacterium diphtheriae
A woman comes to the emergency department with fever and vomiting. She soon develops a red rash all over her body, and her blood pressure begins to drop. What is one possible diagnosis? A) erysipelas B) endocarditis C) scarlet fever D) toxic shock syndrome E) staphylococcal food poisoning
D
Bacteria collected from a severely inflamed wound are sent to the lab for analysis. The results come back as follows: Gram-positive cocci in irregular clusters, kinase and coagulase positive, and able to grow in the presence of most antibiotics except vancomycin. The bacteria in the wound are most likely A) Enterococcus. B) Staphylococcus epidermidis. C) Staphylococcus aureus. D) methicillin-resistant Staphylococcus aureus (MRSA). E) Streptococcus pyogenes (group A streptococcus).
D
How do group A streptococci camouflage themselves from white blood cells? A) They stain as Gram-positive. B) They grow in chains or pairs. C) They produce streptokinase, which breaks down blood clots. D) They have hyaluronic acid capsules. E) They have protein M in their capsule, which destabilizes complement and interferes with opsonization.
D
Over 90% of Staphylococcus aureus bacteria can withstand the effect of penicillin. Why? A) They have loosely organized polysaccharide slime layers. B) They produce coagulase. C) Cell division occurs in successively different planes, and the daughter cells remain attached to one another. D) They produce β-lactamase. E) They produce staphylokinase, which dissolves fibrin threads in blood clots.
D
The Quellung reaction is used to diagnose A) Staphylococcus aureus. B) Streptococcus pyogenes. C) Streptococcus agalactiae. D) Streptococcus pneumoniae. E) Streptococcus equisimilis.
D
Which of the following bacteria is a genus of high G + C Gram-positive bacteria? A) Staphylococcus B) Streptococcus C) Bacillus D) Mycobacterium E) Listeria
D
Which of the following bacteria produce one of the most deadly bacterial toxins known? A) Clostridium perfringens B) Clostridium difficile C) Clostridium tetani D) Clostridium botulinum E) Corynebacterium species
D
Which of the following statements about diphtheria is FALSE? A) Although all species of Corynebacterium are pathogenic, the agent of diphtheria is the most widely known. B) Its toxin destroys elongation factor, which is needed to synthesize polypeptides in eukaryotes. C) It produces a characteristic pseudomembrane that can adhere to the tonsils, uvula, palate, pharynx, and larynx. D) Its growth on Loffler's medium is used for absolute diagnosis of the bacterium. E) Its toxin can be absorbed into the blood from cutaneous lesions and can lead to cardiac arrhythmia, coma, and death.
D
Streptococcus agalactiae is associated with which of the following diseases? A) neonatal bacteremia B) neonatal meningitis C) neonatal pneumonia D) neonatal bacteremia and neonatal meningitis E) neonatal bacteremia, neonatal meningitis, and neonatal pneumonia
E
Untreated streptococcal pharyngitis may progress to A) scarlet fever. B) necrotizing fasciitis. C) rheumatic fever. D) scarlet fever or necrotizing fasciitis. E) scarlet fever or rheumatic fever.
E
Staphylococci divide by snapping division in which the daughter cells remain connected and form grapelike structures.
False
Streptococci are normal microbiota of the skin.
False
________ grow at temperatures up to 45°C, at pH levels as high as 9.6, and in 6.5% NaCl, but they lack structural and chemical elements that make them virulent in the intestinal tract.
Enterococci
A person comes into the clinic with a wound that is severely inflamed, very painful, and turning black and "bubbly." The diagnosis is leprosy.
False
Clostridium bacilli are high G + C Gram-positive, endospore-forming bacteria
False
Most cases of pneumonia are caused by a virus.
False
Mycobacterium leprae manifests itself in two different forms in a patient. What are these? What determines which form the patient will develop?
Mycobacterium leprae produces a disease known as leprosy in susceptible patients. The symptoms of the disease depend on the patient's cell-mediated immune response. In patients with a strong cell-mediated immune response, the patient is able to kill cells infected with the bacteria. In these individuals, the disease manifests as a nonprogressive form of the disease called tuberculoid leprosy. The bacteria cause nerve damage that leads to loss of sensation in regions of skin. In patients with weak cell-mediated immunity, the bacteria multiply in the skin and nerves and gradually lead to progressive loss of facial features, digits, and other body structures. This form of the disease is known as lepromatous leprosy.
The body limits the migration of ________ by binding it to the active sites of secretory IgA, which the bacteria overcome by secreting secretory IgA protease.
Streptococcus pneumoniae
A child with a long history of repeated cases of strep throat develops a heart murmur. What is the most likely diagnosis, and what has caused this condition to develop?
The child is most likely suffering from rheumatic fever. This is a complication of untreated type A streptococcal pharyngitis-that is, strep throat. The condition is not caused directly by streptococcus, but is actually an autoimmune response. Antibodies against the streptococcal antigen cross-react with heart antigens, leading to damage of the heart valves. Damage may be so extensive that the valves must be replaced when the patient reaches middle age.
A throat swab is taken from a patient with a respiratory infection. After 24 hours, 1- to 3-mm colonies develop, which are round, mucoid, nonpigmented, and dimpled in the middle. What is the most likely pathogen, and how could you confirm the diagnosis on the culture?
The colonies described are characteristic of Streptococcus pneumoniae. Diagnosis of this pathogen is confirmed if they are alpha-hemolytic on blood agar when grown aerobically and beta-hemolytic when grown anaerobically. Pneumococcal colonies can be differentiated from other colonies of alpha-hemolytic strains by adding a drop of bile to a colony. The bile triggers chemicals in S. pneumoniae that lyse the cells. The colony dissolves in a few minutes, confirming that they are pneumococcal colonies.
Enterococci have the ability to secrete bacteriocins, which inhibit the growth of other bacteria.
True
Group A streptococci are considered more virulent if their cytoplasmic membrane contains M protein.
True
In contrast to other mycobacteria, Mycobacterium avium-intracellulare simultaneously affects almost every organ in the body
True
Listeria's virulence is directly related to the production of a substance known as ________, which allows it to escape the phagosome into the host cell's cytosol, where it grows intracellularly.
listeriolysin O
Nocardia contains ________, so cells are difficult to stain with the Gram stain, but they are acid-fast.
mycolic acid