Block 9 Structural Toxin Genetic Xchange & Colonize Transmission MCQ
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Structural toxins, genetic exchange, gene expression
Microbial colonization, infection, transmission
Questions and Answers
- 1.
Your patient has septicemia from a Gram-negative bacterium infection. His family members are extremely concerned that he is so sick and ask you to explain what is happening. You tell them that the body's defenses are working to counteract the infection and you show them the hematology results that indicate the patient's neutrophil count is way above the normal range. His son, who is in high school, says he has heard of neutrophils and asks what causes the neutrophil count to increase in this way. Your answer would be?
- A.
The bacterium produces an endotoxin that can act directly on bone marrow cells to induce neutrophil production
- B.
There is a chemokine called 1L-8 that is produce by cells called macrophages and this can recruit neutrophils
- C.
The patient's lymphocytes are stimulated to produce a substance called IL-6 that can recruit neutrophils
- D.
The patient's macrophages produce a substance called TNF-a that can induce neutrophils
Correct Answer
B. There is a chemokine called 1L-8 that is produce by cells called macrophages and this can recruit neutrophilsExplanation
The correct answer explains that in response to the Gram-negative bacterium infection, macrophages produce a chemokine called IL-8. This chemokine acts as a signal to recruit neutrophils, which are a type of white blood cell that plays a crucial role in fighting off infections. Therefore, the increased neutrophil count observed in the patient's hematology results is a result of the body's immune response to the infection.Rate this question:
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- 2.
Your patient is a 19 year old student who presents with drowsiness, stiff neck and fever. Culture of the patient's blood reveals the presence of encapsulated Gram negative diplococci that can ferment glucose and maltose but not sucrose or lactose. What was the bacterial factor that was produced to induce the condition?
- A.
A superantigen
- B.
An enterotoxin
- C.
An endotoxin
- D.
An exotoxin
Correct Answer
C. An endotoxinExplanation
The correct answer is "An endotoxin." In this scenario, the presence of encapsulated Gram-negative diplococci suggests the bacteria Neisseria meningitidis, which is known to cause meningitis. The symptoms of drowsiness, stiff neck, and fever are consistent with this diagnosis. The fact that the bacteria can ferment glucose and maltose but not sucrose or lactose is a characteristic of N. meningitidis. Additionally, the presence of an endotoxin, which is a toxic component of the outer membrane of Gram-negative bacteria, is responsible for inducing the symptoms observed in the patient.Rate this question:
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- 3.
What are the primary components of the structure marked with an arrows produced by this Gram-negative, oxidase-positive, catalase-positive diplococcus that can survive in the bloodstream?
- A.
Polysaccharide, oligosaccharide, lipid A, phospholipids, and proteins
- B.
Polymerized monomers of disaccharide and peptide
- C.
Oligosaccharide, lipid A, phospholipid, and protein
- D.
Polymerized amino acids folded with secondary, tertiary and quaternary structure
- E.
Polysaccharide, nucleic acid, and proteins
Correct Answer
A. Polysaccharide, oligosaccharide, lipid A, phospholipids, and proteinsExplanation
The primary components of the structure marked with an arrow produced by this Gram-negative, oxidase-positive, catalase-positive diplococcus that can survive in the bloodstream are polysaccharide, oligosaccharide, lipid A, phospholipids, and proteins. These components are essential for the survival and function of the bacteria in the bloodstream, providing structural support, protection, and necessary biological processes.Rate this question:
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- 4.
Which of the following characteristics would not help determine the host range of a lytic bacteriophage?
- A.
The amino acid sequence of its tail fibers
- B.
The methylation pattern of its DNA
- C.
The frequency with which it can become a prophage
- D.
The DNA sequence of its promoter region
- E.
The G+C content of its genome
Correct Answer
C. The frequency with which it can become a prophageExplanation
The frequency with which a bacteriophage can become a prophage is not related to its host range. The host range of a bacteriophage is determined by its ability to recognize and bind to specific receptors on the surface of host bacteria. This recognition is typically mediated by the tail fibers of the bacteriophage, which interact with specific molecules on the bacterial surface. The amino acid sequence of the tail fibers is therefore crucial in determining the host range. The methylation pattern of the bacteriophage's DNA, the DNA sequence of its promoter region, and the G+C content of its genome may also play a role in determining the host range by influencing the bacteriophage's ability to infect and replicate within different host bacteria.Rate this question:
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- 5.
Streptococci are referred to as being naturally competent. What does this mean?
- A.
They are considered better able to adapt to new situations
- B.
They can carry out transduction
- C.
They can carry out transformation
- D.
They can carry out conjugation
Correct Answer
C. They can carry out transformationExplanation
In microbiology, genetics, cell biology and molecular biology, competence is the ability of a cell to take up extracellular ("naked") DNA from its environment. Competence may be differentiated between NATURAL COMPETENCE, a genetically specified ability of bacteria which is thought to occur under natural conditions as well as in the laboratory, and induced or artificial competence, which arises when cells in laboratory cultures are treated to make them transiently permeable to DNA.
In almost all NATURALLY COMPETENT bacteria components of extracellular filaments called type 4 pili (a type of fimbria) are involved in the transformation process, and DNA may enter the cells via DNA translocase. Some bacteria cut the DNA into short pieces before transporting it; others can take up very long intact fragments and circular plasmids. The details of the uptake machinery are not yet fully characterized in any system.Rate this question:
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- 6.
Will a bacterium that receives chromosomal DNA via conjugation from a donor Hfr bacterium become capable of passing this DNA on to other bacteria?
- A.
Yes, due to transfer of the tra genes
- B.
Yes, due to transfer of the mob element
- C.
Yes, due to transfer of the Hfr locus
- D.
Maybe, if the tra genes are transferred
- E.
Maybe, if the mob element is transferred
- F.
No, because the tra genes are present on a plasmid not on the chromosome
Correct Answer
D. Maybe, if the tra genes are transferredExplanation
Transfer operon, commonly called --tra operon,--- or tra genes, are some of the genes necessary for non-sexual transfer of genetic material in both gram-positive and gram-negative bacteria. The tra locus includes the pilin gene and regulatory genes, which together form pili on the cell surface, polymeric proteins that can attach themselves to the surface of F- bacteria and initiate the conjugation.
The---tra genes--- encode proteins which are useful for the propagation of the plasmid from the host cell to a compatible donor cell or maintenance of the plasmid. Not all transfer operons are the same. Some genes are only found in a few species or a single genus of bacteria while others (such as traL) are found in very similar forms in many bacterial species. Many of the transfer systems are incompatible. For example, oriT and mob are two origins of transfer which interact with different sets of transfer genes. A plasmid with a mob site (like many found in Rhodococcus species) cannot be transferred via transfer genes which normally interact with the oriT site (which is common in E. coli)
Each of the individual genes in the --tra operon--- codes for a different protein product. These products may perform a number of tasks including interaction with one another to perform mating pair functions and regulation of different regions of the tra operon itself,[5] or conjugative DNA metabolism and surface exclusion.[4] Also note that some proteins perform multiple functions or are associated closely with proteins which have non-similar functionsRate this question:
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- 7.
Which of the following best describes the accidental packaging of bacterial DNA into a bacteriophage during bacteriophage packaging for progeny phage production?
- A.
Specialized transduction
- B.
Accidental transduction
- C.
Conjugation
- D.
Generalized transduction
- E.
Transformation
Correct Answer
D. Generalized transductionExplanation
GENERALIZED TRANSDUCTION
Lytic lifecycle
Fragment of host DNA ACCIDENTALLY PACKAGED in phage instead of phage DNA
When that phage injects the bacterial DNA into a new host, bacterial genes are transferred
Phage DNA not present, so recipient cell is transduced, but not infected
LOW RATE OF SUCCESS
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SPECIALIZED TRANSDUCTION
Lysogenic phage
Prophage excises incorrectly, taking a piece of host chromosome with it
Similar to F’
May transfer enough phage DNA to be functional in new host
HIGH RATE OF SUCCESSRate this question:
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- 8.
A microbe is getting ready for sporulation using alternate sigma factors. What is the purpose of these factors?
- A.
Degrading phage DNA
- B.
Replicating DNA
- C.
Transcribing genes
- D.
Secreting peptides
- E.
Translating genes
Correct Answer
A. Degrading phage DNAExplanation
The purpose of the alternate sigma factors in a microbe getting ready for sporulation is to degrade phage DNA. These factors play a crucial role in the regulation of gene expression during sporulation, including the degradation of phage DNA to prevent the replication and spread of phages within the microbe.Rate this question:
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- 9.
A point mutation occurs in a human pathogen. It is localized to a nucleic acid affecting the expression and export of a collagenase enzyme, causing it to abnormally express collagenase activity at 25C. Which of the following changes could cause this effect?
- A.
The gene encoding the collagenase, causing altered temperature stability
- B.
A negative regulator of the operon, causing it to always be active via a structural change
- C.
A positive regulator of the operon, causing it to have a decreased affinity for its recognition sequence
- D.
The ribosome binding site, allowing more efficient translation
- E.
A sensor kinase, causing it to always be active via a structural change
Correct Answer
E. A sensor kinase, causing it to always be active via a structural changeExplanation
A point mutation in the sensor kinase gene could cause it to always be active, leading to a structural change in the protein. This structural change would result in the continuous activation of the pathway that regulates the expression and export of the collagenase enzyme. As a result, the collagenase enzyme would abnormally express collagenase activity at 25C. This mutation would not directly affect the gene encoding the collagenase, the negative or positive regulator of the operon, or the ribosome binding site.Rate this question:
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- 10.
You are discussing the different types of hepatitis with a patient who states that he is certain that all hepatitis viruses are similar. You thus go on to state that Hepatitis A virus is adapted to its mode of transmission, which is quite different from that of Hepatitis B. What is this important feature about Hepatitis A that is important for transmission?
- A.
It has no envelope
- B.
The virus kills the cell it infects
- C.
It has a positive sense, single, strand of RNA
- D.
It can bind to ICAM-1 (CD54)
Correct Answer
A. It has no envelopeExplanation
Hepatitis A virus is unique because it does not have an envelope. This is an important feature for transmission because the envelope of a virus helps protect it from the host's immune system. Without an envelope, the hepatitis A virus is more susceptible to being destroyed by the body's defenses, making it less likely to cause a persistent infection. Additionally, the lack of an envelope also means that the virus is more stable in the environment and can survive outside the body for longer periods, increasing the chances of transmission through contaminated food or water.Rate this question:
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- 11.
Your patient is in his late 30's and with a disheveled appearance. He is emaciated and dirty. He is pyrexic (102 F) and complains of fatigue, anorexia and palpitations. Upon examination you notice needle marks on both arms. You order a series of blood tests and cultures at 2 hour intervals and the laboratory returns an identification of Gram-positive, catalase and coagulase positive, cocci. What is the organism?
- A.
Staph. Aureus
- B.
Strep. Agalactiae
- C.
Staph. Epidermidis
- D.
Strep. pyogenes
- E.
Viridans group of streptococci
Correct Answer
A. Staph. AureusExplanation
The patient's symptoms, such as fatigue, anorexia, and palpitations, along with the presence of needle marks on both arms, suggest drug abuse. The identification of Gram-positive, catalase and coagulase positive, cocci in the blood cultures is consistent with Staphylococcus aureus, which is a common pathogen associated with drug abuse and can cause systemic infections. Therefore, the correct answer is Staph. Aureus.Rate this question:
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- 12.
Your patient is in his late 30's and with a disheveled appearance. He is emaciated and dirty. He is pyrexic (102 F) and complains of fatigue, anorexia and palpitations. Upon examination you notice needle marks on both arms. You order a series of blood tests and cultures at 2 hour intervals and the laboratory returns an identification of Gram-positive, catalase and coagulase positive, cocci. If you examine the patient further, which of the following signs might you expect to find?
- A.
Winterbottom's sign
- B.
Nikolsky's sign
- C.
Osler’s nodes
- D.
Brudzinski's sign
- E.
Kernig sign
Correct Answer
C. Osler’s nodesExplanation
Osler's nodes are painful, red, raised lesions found on the hands and feet. They are associated with a number of conditions, including infective endocarditis, and are caused by immune complex deposition.
Winterbottom's sign; - is seen in the early phase of African trypanosomiasis, a disease caused by the parasites Trypanosoma brucei rhodesiense and Trypanosoma brucei gambiense (African sleeping sickness). It is described as the swelling of lymph nodes (lymphadenopathy) along the back of the neck, in the posterior cervical chain of lymph nodes, as trypanosomes travel in the lymphatic fluid and cause inflammation.
It may be suggestive of cerebral infection
Nikolsky's sign: - is a clinical dermatological sign. The sign is positive when slight rubbing of the skin results in exfoliation of the outermost layer.
Nikolsky's sign is almost always present in toxic epidermal necrolysis and is associated with pemphigus vulgaris. It is useful in differentiating between pemphigus vulgaris (where it is present or positive) and bullous pemphigoid (where it is absent)
Kernig's sign-- is positive when the thigh is bent at the hip and knee at 90 degree angles, and subsequent extension in the knee is painful (leading to resistance).
This may indicate subarachnoid hemorrhage or meningitis.
Patients may also show opisthotonus—spasm of the whole body that leads to legs and head being bent back and body bowed backwards
Brudzinski's signs:
Jozef Brudzinski (1874–1917), a Polish pediatrician, is credited with several signs in meningitis. The most commonly used sign (Brudzinski's neck sign) is the appearance of involuntary lifting of the legs in meningeal irritation when lifting a patient's head off the examining couch, with the patient lying supine.
Other signs attributed to Brudzinski:
The symphyseal sign, in which pressure on the pubic symphysis leads to abduction of the leg and reflexive hip and knee flexion.
The cheek sign, in which pressure on the cheek below the zygoma leads to rising and flexion in the forearm.
Brudzinski's reflex, in which passive flexion of one knee into the abdomen leads to involuntary flexion in the opposite leg, and stretching of a limb that was flexed leads to contralateral extensionRate this question:
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- 13.
What is your diagnosis for the patient ? Your patient is in his late 30's and with a disheveled appearance. He is emaciated and dirty. He is pyrexic (102 F) and complains of fatigue, anorexia and palpitations. Upon examination you notice needle marks on both arms. You order a series of blood tests and cultures at 2 hour intervals and the laboratory returns an identification of Gram-positive, catalase and coagulase positive, cocci.
- A.
Bacterial endocarditts
- B.
Streptococcal pneumonia
- C.
Toxicity from injecting contaminated heroin
- D.
Bacterial meningitis
- E.
Osteomyelitis
- F.
He is a ROSS student, Just tired of studying micro/immuno
Correct Answer
A. Bacterial endocardittsExplanation
Osler's nodes are painful, red, raised lesions found on the hands and feet. They are associated with a number of conditions, including infective endocarditis, and are caused by immune complex deposition.Rate this question:
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- 14.
Which of the following is an example of localized spread?
- A.
Spread to the proximal lymph nodes by infected antigen presenting cells (dendritic cells and macrophages)
- B.
Spread by infected lymphocytes through lymphocyte recirculation
- C.
Spread by syncytia formation
- D.
Vertical spread from the mother to her foetus by macrophages
- E.
None of the above choices is an example of localized spread
Correct Answer
C. Spread by syncytia formationExplanation
A syncytium is a multinucleate cell which can result from multiple cell fusions of uninuclear cells.
Viral infection:
Syncytium caused by HSV-1 infection in Vero cells
Syncytia can also form when cells are infected with certain types of viruses, notably HIV and paramyxoviruses, e.g. Respiratory syncytial virus (RSV). During infection, viral fusion proteins used by the virus to enter the cell are transported to the cell surface where they can cause the host cell membrane to fuse with neighbouring cells.
HIV infects CD4+ T cells and makes the cell produce viral proteins, including fusion proteins. Then, the cell begins to display surface HIV glycoproteins, which are antigenic. Normally, a cytotoxic T cell will immediately come to "inject" lymphotoxins, such as perforin or granzyme, that will kill the infected T helper cell. However, if there are nearby T helper cells, the gp41 HIV receptors displayed on the surface of the T helper cell will bind to other similar lymphocytes. This makes dozens of T helper cells fuse cell membranes into a giant, nonfunctional syncytium, which allows the HIV virion to kill many T helper cells by infecting only one.Rate this question:
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Mar 20, 2023Quiz Edited by
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May 05, 2012Quiz Created by
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