A Microbiology Knowledge Review Quiz
.
- 1.
Assume the following cells have no plasmids other than those mentioned. Which cell type would contain two molecules of DNA?
- A.
F+
- B.
F-
- C.
Hfr
Correct Answer
A. F+Explanation
The F+ cell type would contain two molecules of DNA. This is because F+ cells have a plasmid called F plasmid, which is a circular DNA molecule. Therefore, in F+ cells, there would be two molecules of DNA - the chromosomal DNA and the F plasmid DNA.Rate this question:
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- 2.
Assume the cells whose genotype is listed have no other plasmids than those indicated by the indicated genotype. Which bacterial is most likely to transfer chromosomal genes in linear order?
- A.
F+
- B.
F-
- C.
Hfr
- D.
Option 4
Correct Answer
C. HfrExplanation
The Hfr (High frequency of recombination) bacterial strain is most likely to transfer chromosomal genes in linear order. Hfr strains have the F plasmid integrated into their chromosome, allowing for the transfer of chromosomal genes during conjugation. This integration results in the transfer of genes in a linear order, as opposed to the F+ and F- strains which only transfer plasmid DNA. Therefore, the Hfr strain is the best choice for transferring chromosomal genes in a linear order.Rate this question:
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- 3.
What bacterial gene transfer process is most sensitive to extracellular nucle-ases?
- A.
Conjugation
- B.
Generalized transduction
- C.
Homologous recombination
- D.
Site-specific recombination
- E.
Specialized transduction
- F.
Transformation
Correct Answer
F. TransformationExplanation
Transformation is the bacterial gene transfer process that is most sensitive to extracellular nucleases. Transformation involves the uptake and incorporation of naked DNA from the environment into the bacterial cell. Extracellular nucleases can degrade the naked DNA before it is taken up by the cell, thereby preventing successful transformation.Rate this question:
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- 4.
Following specialized transduction, if any of the bacterial genes transferred in are to be stabilized, what process must occur?
- A.
Conjugation
- B.
Generalized transduction
- C.
Homologous recombination
- D.
Site-specific recombination
- E.
Specialized transduction
- F.
Transformation
Correct Answer
C. Homologous recombinationExplanation
Homologous recombination is the process that must occur to stabilize any of the bacterial genes transferred in after specialized transduction. Homologous recombination is a DNA repair process that involves the exchange of genetic material between two homologous DNA molecules. In this case, it would involve the integration of the transferred bacterial genes into the recipient bacterial genome, ensuring their stability and proper functioning. This process requires a high degree of sequence similarity between the transferred genes and the recipient genome for successful integration to occur.Rate this question:
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- 5.
The ability of a cell to bind DNA to its surface and import it is required for which genetic process?
- A.
Conjugation
- B.
Generalized transduction
- C.
Homologous recombination
- D.
Site-specific recombination
- E.
Specialized transduction
- F.
Transformation
Correct Answer
F. TransformationExplanation
The ability of a cell to bind DNA to its surface and import it is required for the genetic process of transformation. In transformation, a bacterial cell takes up foreign DNA from its surroundings and incorporates it into its own genome. This process allows for the transfer of genetic material between bacteria and can lead to the acquisition of new traits or the spread of antibiotic resistance genes.Rate this question:
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- 6.
The process by which bacterial or plasmid DNA may be mistakenly incor-porated (during assembly) into one phage being produced by the lytic life cycle and then DNA - transferred to another bacterial cell which may acquire some new genetic traits is called
- A.
Conjugation
- B.
Generalized transduction
- C.
Homologous recombination
- D.
Site-specific recombination
- E.
Specialized transduction
- F.
Transformation
Correct Answer
B. Generalized transductionExplanation
Generalized transduction is the process in which bacterial or plasmid DNA is mistakenly incorporated into a phage during assembly. This phage then transfers the DNA to another bacterial cell, which can result in the acquisition of new genetic traits. This process is different from specialized transduction, which involves the transfer of specific genes. Homologous recombination and site-specific recombination are mechanisms by which DNA can be rearranged or exchanged between chromosomes. Conjugation is the direct transfer of DNA between bacterial cells. Transformation is the uptake of DNA from the environment by a bacterial cell.Rate this question:
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- 7.
Lysogenic conversion
- A.
Is a change in pathogenicity due to the presence of a prophage
- B.
Is the induction of a prophage to its virulent state
- C.
Is the conversion of a virulent phage into a temperate phage
- D.
Refers to the incorporation of a prophage into the chromosome
- E.
Is the immunity that a prophage confers on a bacterium
Correct Answer
A. Is a change in pathogenicity due to the presence of a propHageExplanation
Lysogenic conversion refers to a change in pathogenicity caused by the presence of a prophage. This means that when a bacterium is infected by a temperate phage, the phage DNA becomes integrated into the bacterial chromosome and is replicated along with it during cell division. This integration can result in the expression of new genes or the alteration of existing ones, leading to a change in the bacterium's pathogenicity. Therefore, lysogenic conversion is a phenomenon where the presence of a prophage influences the pathogenic properties of the bacterium.Rate this question:
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- 8.
Which of the following events is most likely due to bacterial transformation?
- A.
A formerly non- toxigenic stran of Corynebacterium dephtheriae beocmes toxigenic
- B.
A non-encapsulated strain of streptococcus pneumoniae accquires a gene for capsule formation from the extract of an encapsulated strain
- C.
A strain of Neisseria gonorrhoeae starts producing a plasmid-encoded β-lactamase similar to that another gram-negative strain
- D.
A gene for gentamicin resistance from an Escherichia coli chromosome appears in the genome of a bacteriophage that has infected it
Correct Answer
B. A non-encapsulated strain of streptococcus pneumoniae accquires a gene for capsule formation from the extract of an encapsulated strainExplanation
Bacterial transformation is the process by which bacteria take up and incorporate foreign DNA into their genome. In this case, a non-encapsulated strain of Streptococcus pneumoniae acquiring a gene for capsule formation from the extract of an encapsulated strain is the most likely event due to bacterial transformation. This is because the non-encapsulated strain is able to incorporate the gene for capsule formation from the extract, resulting in the acquisition of the ability to produce capsules. This process is a common mechanism for bacteria to acquire new traits and genetic material.Rate this question:
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- 9.
A 12-year old girl experienced a GAS pharyngitis and within 3 weeks had chest pain and developed new murmurs of mitral regurgitation. Which of yhe following statement best typifies the disease she experienced?
- A.
It is a complication of group A streptococcal skin disease but usually not of pharyngitis
- B.
It is characterized by inflammatory lesions that may involve the heart, joints, subcutaneous tissues, and CNS
- C.
It is very common in developing countries but extremely rare and decreasing in incidence in the United States
- D.
Prophylaxis with benzathine penicillin is of little value
- E.
The pathogenesis is related to the similary between a staphylococcal antigen and a human cardiac antigen
Correct Answer
B. It is characterized by inflammatory lesions that may involve the heart, joints, subcutaneous tissues, and CNSExplanation
The correct answer suggests that the disease experienced by the 12-year-old girl is characterized by inflammatory lesions that can affect various parts of the body including the heart, joints, subcutaneous tissues, and CNS. This indicates that the disease is not limited to a specific area or organ but can involve multiple systems. This information helps in identifying the nature and extent of the disease and can guide further diagnosis and treatment.Rate this question:
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- 10.
A young child developed staphylococcal scaleded syndrome. Which one of the following toxins is most likely responsible for this syndrome?
- A.
Alpha toxin
- B.
Erythrogenic toxin
- C.
Exfoliative toxin
- D.
Staphylococcal enterotoxins A through F
- E.
Toxic shock syndrome toxin (TSST)
Correct Answer
C. Exfoliative toxinExplanation
Exfoliative toxin is most likely responsible for staphylococcal scaleded syndrome. This toxin is produced by Staphylococcus aureus and causes the detachment of the top layer of the skin, resulting in a widespread scaling rash. This syndrome is commonly seen in young children and is characterized by fever, irritability, and the presence of a generalized red rash that later desquamates.Rate this question:
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- 11.
43-year-old man who recently returned from a trip to rural Peru presents with severe watery diarrhea, vomiting, and dehydration. He also has marked leg cramps and has lots 8lb since his return form the trip. fecal culture is positive for V.cholerae. How does this bacterium exert its effect?
- A.
Activation of enterokinase on the brush border of epithelial cells
- B.
activation of cholecystokinin effects on pancreatic secretion
- C.
Closure of chloride channels in the enterocyte cell membrane
- D.
Inhibition of cyclic AMP in the enterocytes.
- E.
ADP-ribosylation of GS of the GPT-binding protein in enterocytes
Correct Answer
E. ADP-ribosylation of GS of the GPT-binding protein in enterocytesExplanation
Vibrio cholerae exerts its effect by ADP-ribosylating the GS (guanine nucleotide-binding protein) of the GPT (G protein-coupled receptor) in enterocytes. This leads to the activation of adenylate cyclase and subsequent increase in cyclic AMP (cAMP) levels within the enterocytes. Increased cAMP levels result in the activation of the cystic fibrosis transmembrane conductance regulator (CFTR) and subsequent secretion of chloride ions into the intestinal lumen. This leads to an osmotic imbalance, causing severe watery diarrhea and dehydration, as observed in the patient.Rate this question:
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- 12.
A 3-year-old girl from a family that does not believe in immunization to the emergency room with a sore throat, fever, malaise, and difficulty breathing. A gray membrane covering the pharynx is observed on physical emamination. Which of the following best describes C.diptheriae, the etiologic agent?
- A.
It produces at least one protein toxin consiting of two subunits, A and B, that cause severe spasmodic cough, usually in children
- B.
It produces a toxin that blocks protein synthesis in an infected cell and carries a lytic bacteriophage that produces the genetic information for toxin production
- C.
It secretes an erythrogenic toxin that causes the characteristic signs of scarlet fever
- D.
It secretes an exotoxin that has been called "verotoxin" and "Shiga-like toxin"; infection is mediated by specific attachment to mucosal membranes
- E.
It requires cysteine for growth
Correct Answer
E. It requires cysteine for growthExplanation
Corynebacterium diphtheriae, the etiologic agent of diphtheria, requires cysteine for growth. This means that the bacteria cannot grow in a medium that lacks cysteine, an amino acid. This characteristic is important in the laboratory for identifying and culturing the bacteria. The other options provided in the question are incorrect and do not accurately describe C. diphtheriae or its characteristics.Rate this question:
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- 13.
A 4-year-old girl awakens at midnight complaining of a sore throat and headache, and she has a fever of 1010F. Physical examination reveals an erythematous throat. A rapid strep test is positive. A throat swab is sent to the labotary for further testing. Which of the following best characterizes S pyogenes as the presumed etiologic agent?
- A.
It produces at least one protein toxin consisting of two subunits, A and B, that cause severe spasmodic cough. usually in children
- B.
It produces a toxin that blocks protein synsthesis in an infected cell and carries a lytic bacterophage that produces the genetic information for toxin production
- C.
It secretes an exotoxin that has been called "verotoxin" and "Shiga-like toxin"; infection is mediated by specific attachment to mucosal membranes
- D.
It secretes an erythrogenic toxin that causes the characteristic signs of scarlet fever
- E.
It has capsules of polyglutamic acid, which is toxic when ịnected into rabbits
Correct Answer
A. It produces at least one protein toxin consisting of two subunits, A and B, that cause severe spasmodic cough. usually in childrenExplanation
The correct answer describes the characteristics of Bordetella pertussis, which is the causative agent of whooping cough. It produces a protein toxin known as pertussis toxin, which consists of two subunits, A and B. This toxin is responsible for causing severe spasmodic cough, especially in children. Streptococcus pyogenes, on the other hand, is the causative agent of strep throat and does not produce a toxin that causes cough.Rate this question:
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- 14.
A severely burned firefighter develops a rapidly disseminating bacterial infection while hospitalized. "Green pus" is noted in the burned tissue, and cultures of both the tissue and blood yield small, oxidase-positive, gram-negative rods. Which of the following statements about this organism is correct?
- A.
Endotoxin is the only virulence factor known to be produced by these bacteria
- B.
Humans are the only known reservoir hosts for these bacteria
- C.
The bacteria are difficult to culture because they have numerous growth requirements
- D.
These are among the most antibiotic resistant of all clinically relevant bacteria
- E.
These highly motile bacteria can "swarm" over the surface of culture media
Correct Answer
D. These are among the most antibiotic resistant of all clinically relevant bacteriaExplanation
These bacteria are among the most antibiotic resistant of all clinically relevant bacteria. This means that they have the ability to resist the effects of antibiotics, making them difficult to treat and control. This is particularly concerning in the case of a severely burned firefighter who has developed a bacterial infection, as the infection may be more difficult to manage due to the limited treatment options available.Rate this question:
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- 15.
Vibrio cholerae is worldwide in distribution and continues to expand as water sources become polluted. Which of the following best describe this organism?
- A.
Cause of gastroenteritis, reservoir in birds and mammals, optimal growth at 107.60F (420C)
- B.
Human pathogen, halophilic, lactose-positive, sucrose-negative, causes gastrointestinal diseases primarily from ingestion of under-cooked seafood
- C.
Human pathogen, halophilic, lactose-positive, produces heat-labile, extracellular toxin, wound infections
- D.
Organism susceptible to acid; not an invasive organism
- E.
Urease-positive, cause of fetal distress in cattle
Correct Answer
A. Cause of gastroenteritis, reservoir in birds and mammals, optimal growth at 107.60F (420C)Explanation
The correct answer describes Vibrio cholerae as a cause of gastroenteritis, with a reservoir in birds and mammals, and optimal growth at a temperature of 107.60F (42°C). This suggests that Vibrio cholerae is a pathogenic bacterium that can cause gastrointestinal diseases in humans, and it is commonly found in the digestive systems of birds and mammals. Additionally, it thrives at a specific temperature range, which may contribute to its ability to survive and spread in polluted water sources.Rate this question:
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- 16.
A healthy 45-year-old female hat root canal treatment about 3 weeks ago. She not presents with a new heart murmur, fever, painful skin nodules, and abdominal pain, with an abnormal liver function test. Which of the following organisms would most likely cause endocarditis and be implicated in dental caries or root canal infections?
- A.
α-hemolytic strepticocci
- B.
Fragilis
- C.
E.coli
- D.
Lactobacillus
- E.
S.epidermidis
Correct Answer
A. &alpHa;-hemolytic strepticocciExplanation
The most likely organism to cause endocarditis and be implicated in dental caries or root canal infections is α-hemolytic streptococci. This group of bacteria is commonly found in the oral cavity and can cause infections in the heart valves (endocarditis) when they enter the bloodstream. The symptoms described in the patient, such as a new heart murmur and fever, are consistent with endocarditis. Additionally, the fact that the patient recently had a root canal treatment suggests a potential source of infection from the oral cavity. α-hemolytic streptococci are known to be associated with dental infections and can lead to systemic infections like endocarditis.Rate this question:
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- 17.
Chlamydiae are small, gram-negative rods once thought to be viruses. Which of the following best characterizes chlamydiae as distinct from viruses?
- A.
Cannot visualize with light microscope
- B.
Independent synthesis of proteins
- C.
Intracellular reproduction
- D.
Susceptibility to antimicrobial agents (penicillins)
- E.
Synthesis of ATP
Correct Answer
B. Independent synthesis of proteinsExplanation
Chlamydiae are distinct from viruses because they have the ability to independently synthesize proteins. Unlike viruses, which require a host cell to replicate and produce proteins, chlamydiae are capable of carrying out protein synthesis on their own. This is a characteristic of living organisms and sets chlamydiae apart from viruses.Rate this question:
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- 18.
S.pneumoniae cause significant morbidity and mortality due to capsular virulence factors. These capsules (55 antigenic types) are characterized by which of the following?
- A.
γ-Glutamyl polypeptide
- B.
Hyaluronic acid
- C.
Outer-membrane proteins
- D.
Repeating polysaccharide capsule of glucose and glucuronic acid
- E.
Sialic acid polymers
Correct Answer
A. γ-Glutamyl polypeptide -
- 19.
A 6-year-old girl presents to her pediatrician with fever, headache, and a sore throat. She has swollen tender cervical lymph nodes, and her oropharynx is red with gray-white exudate covering both her tonsils. A rapid strep test of her throat swab is possitive, and the culture subsequently grows β-hemolytic Streptococcus. Which of the following antibiotic therapies is most appropriate for treating this patient?
- A.
Ampicillin
- B.
Ceftriaxone
- C.
Erythromycin
- D.
Penicillin
- E.
Vancomycin
Correct Answer
D. PenicillinExplanation
Penicillin is the most appropriate antibiotic therapy for treating this patient. The clinical presentation of fever, headache, sore throat, swollen tender cervical lymph nodes, and the presence of gray-white exudate on both tonsils suggests a diagnosis of streptococcal pharyngitis, commonly known as strep throat. The positive rapid strep test and subsequent growth of beta-hemolytic Streptococcus in culture further supports this diagnosis. Penicillin is the drug of choice for treating streptococcal pharyngitis due to its efficacy, low cost, and narrow spectrum of activity against Streptococcus species.Rate this question:
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- 20.
Streptococcus mutans is best described by which of the following statements?
- A.
An anaerotic, filamentous bacterium that often causes cervicofacial osteomyelitis
- B.
A β-hemolytic organism that causes a diffuse, rapidly spreading cellulitis
- C.
A facultative anaerobe that is highly cariogenic and sticks to teeth by synthesis of a dextran
- D.
A facultative anaerobe that often inhabits the buccal mucosa early in a neonate's life and can cause bacterial andocarditis
- E.
A Facultative anaerobic, rod-shaped bacterium that sticks to teeth and is cariogenic
Correct Answer
C. A facultative anaerobe that is highly cariogenic and sticks to teeth by synthesis of a dextranExplanation
The correct answer states that Streptococcus mutans is a facultative anaerobe that is highly cariogenic and sticks to teeth by synthesis of a dextran. This means that Streptococcus mutans can survive in both aerobic and anaerobic conditions, it is highly involved in the formation of dental caries (cavities), and it adheres to teeth by producing a sticky substance called dextran. This explanation accurately describes the characteristics and behavior of Streptococcus mutans.Rate this question:
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- 21.
A 3-year-old girl, with no history of vaccination, is brought to the hospital with a sore throat, fever, malaise, and difficulty breathing. physical examination reveals a gray membrane covering the pharynx. Growth of the etiolgic agent on cysteine-tellurite agar forms gray to black colonies with a brown halo. The major virulence factor of this organism is only produced by those strains that will most likely have which of the following characteristics?
- A.
Encapsulated
- B.
Glucose fermenters
- C.
Lysogenic for β-prophage
- D.
Of the mitis strain
- E.
Sucrose fermenters
Correct Answer
C. Lysogenic for β-propHageExplanation
The correct answer is "Lysogenic for β-prophage." The major virulence factor of the organism causing the symptoms in the 3-year-old girl is produced only by strains that are lysogenic for β-prophage. This suggests that the organism has acquired the ability to produce the virulence factor through the integration of a prophage into its genome.Rate this question:
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