micro-bio-exam2-brooklyn-college

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Studocu is not sponsored or endorsed by any college or university Micro BIO EXAM2 - brooklyn college Microbiology (Brooklyn College) Studocu is not sponsored or endorsed by any college or university Micro BIO EXAM2 - brooklyn college Microbiology (Brooklyn College) Downloaded by wik koza (wiktoriakoza2000@gmail.com) lOMoARcPSD|27457473

CHAPTER 15 1 . Adaptive Immunity Protection provided by immune responses that improve due to exposure to antigens; involves B cells and T cells. 2. Antibody Y-shaped protein that binds antigen. 3. Antigen Molecule that reacts specifically with either an antibody or an antigen receptor on a lymphocyte. 4. Antigen-Presenting Cells (APCs) Cells such as B cells, macrophages, and dendritic cells that can present exogenous antigens to naive or memory T cells, activating them. 5 . B Cell Type of lymphocyte programmed to make antibodies. 6. Cell-Mediated Immunity (CMI) Immunity involving a T-cell response. 7. Clonal Selection Process in which a lymphocyte’s antigen receptor binds to an antigen, allowing the lymphocyte to multiply. 8. Cytotoxic T Cell Type of lymphocyte programmed to destroy infected or cancerous “self” cells. 9. Dendritic Ce ll Cell type responsible for activating naive T cells. 10. E ffector Lymphocyte Differentiated descendant of an activated lymphocyte; it has properties that allow it to help eliminate antigen. 11. Helper T Cell Type of lymphocyte programmed to activate B cells and macrophages, and assist other parts of the adaptive immune response. 12. Humoral Immunity Immunity involving B cells and an antibody response. 13. Lymphocytes A group of white blood cells (leukocytes) involved in adaptive immunity; B cells and T cells are examples. 14. Major Histocompatibility Complex (MHC) Molecules Host cell surface proteins that present antigen to T cells. 15. Memory Lymphocytes Long- lived descendants of activated lymphocytes that can quickly respond when a specific antigen is encountered again. 1 6. Plasma Cell Effector form of a B cell; it functions as an antibody-secreting factory. 17 . TC Cell Effector form of a cytotoxic T cell; it induces apoptosis in infected or cancerous “self” cells. 18. TH Cell Effector form of a helper T cell; it activates B cells and macrophages, and releases cytokines that stimulate other cells of the immune system. Compare and contrast the general characteristics of humoral immunity and cell-mediated immunity. (10 points) · Humoral immunity is mediated by antibodies produced by B cells (B lymphocytes). 1 pt · The mature differentiated B cells that produce antibodies are called plasma cells. 1 pt · Antibodies target extracellular antigens (microbes and their toxins in the blood stream of ﬂuid tissues). 1 pt · Cell-mediated immunity is carried out by T cells (T lymphocytes). 1p t · There are two major classes of T cells, T-helper cells (CD4+) and cytotoxic T cells (CD8+) also called killer T cells. 2 pts · T-helper cells secrete cytokines are primarily involved in regulating immune responses. 2 pt · Cytotoxic T cells target and kill virally or bacterially infected cells of the body. 2 pt Downloaded by wik koza (wiktoriakoza2000@gmail.com) lOMoARcPSD|27457473

2. Please describe elements and mechanisms of mucosal immunity. (5 points) · Mediated by IgA antibodies (secretory antibodies) secreted into mucosal surfaces (1 pt) · Peyer’s patches are collections of lymphoid cells underlying the gastrointestinal tract. Peyer’s patches are an example of MALT (mucosal associated lymphoid tissue). They are examples of secondary lymphoid organs. (2 pts) · M cells may transfer antigens from the gut lumen to macrophages and dendritic cells within Payer’s patches (2 pts). 3. Please describe the relationship between antigens and epitopes . (5 points) · Antigens are molecules recognized by antibodies and other receptors of the immune system (such as TCRs on T cells or BCRs on B cells). The term antigen is a portmanteau from the term antibody generator. (2 pt) · Microorganisms, bacteria and viruses etc., have many antigens. A protein, or lipid or other element of a microorganisms could act as an antigen. (1 pt) · Epitopes are smaller regions (~10 or so amino acids) of an antigen that are specifically recognized and bound by antibodies and other lymphocyte receptors. Epitopes are sometimes referred to as antigenic determinants. (2 pt) · An antigen may have many different epitopes and a bacteria or virus could have 100s or more epitopes. (optional 1 pt) 4. Diagram a typical antibody (IgG class), labeling the various functional regions. Which region of an antibody determines its class? a. “Y” shaped with antigen recognition regions at the variable ends of the two arms and a constant region at the base. (3 points) b. Consists of two heavy chain protein subunits and two light chain protein subunits. They are held together by disulfide bonds. (2 points) c. The constant region defines an antibody’s class (1 point) 5. Brieﬂy describe five of the six functions antibodies can have in preventing infections. a. Complement system activation (1 point) b. Immobilization and prevention of adherence of microbial pathogens (1 point) c. Cross-linking bacteria or other microbial invaders (1 point) d. Antibody-dependent cellular cytotoxicity (ADCC) (1 point) e. Virus and toxin neutralization (1 point) f. Opsonization (1 point) 6 . Describe memory lymphocytes and their role in immune responses to microbial pathogens. a. Memory cells are long-lived descendants of activated T cells and B cells. (2 points) b. The memory cells are responsible for the rapid and strong secondary immune response if the antigen is detected again. (3 points) 7. Describe the clonal selection and expansion of B cells. Downloaded by wik koza (wiktoriakoza2000@gmail.com) lOMoARcPSD|27457473

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a. Development – naïve B cells recognize their specific antigen with their B cell receptor. (2 points) b. B cells become activated and proliferate because they recognized their antigen. They receive confirmation from T cells. (1 point) c. The proliferating B cells begin to differentiate into antibody-producing plasma cells and a few memory B cells. (1 point) d. Antibodies are churned out by plasma cells and go on to neutralize their foreign element they recognize and target the recognized bacteria or viruses for destruction (or infected host cells too). (2 point) 8. Describe the structure and function of the following classes of antibodies: IgA, IgE, IgG, and IgM. a. IgA are secretory antibodies. They are secreted in saliva, tears, breast milk, and into the mucosal surfaces of the body. They are formed from a dimer of two antibodies joined at the constant regions. They have a half-life of ~6 days. (3 point) b. IgE are similar “Y” monomer structure of IgG. They bind the the surface of basophils and mast cells through their constant domains. They trigger the release of histamines and other inﬂammatory mediators. Thought to target infections by worms and other parasites. (2 points) c. IgG is the standard monomeric immunoglobulin that circulates in the blood. It provides the longest-term protection (half-life ~21 days). Involved in neutralization, ADCC, opsonization, and complement activation. (3 points) d. IgM has a pentameric structure and is the first antibody class produced in primary response to a pathogen. (2 points) CHAPTER 16 A cute Infection An infection characterized by symptoms that develop fairly quickly and last a relatively short time. 2. C hronic Infection An infection that generally develops slowly and lasts for months or years. 3. Colonization Establishment and growth of a microorganism on a surface. 4. Endotoxin The lipopolysaccharide (LPS) component of the outer membrane of Gram- negative bacteria; lipid A is responsible for the toxic properties of LPS. 5. Exotoxi n A toxic protein produced by a microorganism; often simply referred to as a toxin. 6. I mmunocompromised Having a weakness or defect in the innate or adaptive defenses. 7. Infection Colonization by a pathogen on or within the body. 8. Infectious Disease An infection that prevents the body from functioning normally. 9. Latent Infection Infection in which the infectious agent is present but not causing symptoms. 10. Microbiome The total genetic information of a community of microorganisms in a given environment; also the community itself, in which case the term is often used synonymously with normal microbiota. 11. Normal Microbiota The group of microorganisms that routinely colonize the body of a healthy individual. Downloaded by wik koza (wiktoriakoza2000@gmail.com) lOMoARcPSD|27457473

12. Opportunistic Pathogen A microbe that causes disease only when introduced into an unusual location or into an immunocompromised host. 13. Primary Pathogen A microbe able to cause disease in an otherwise healthy individual. 14. Virulence Factors Traits of a microbe that promote pathogenicity. Please define the following terms: symbiosis, mutualism, commensalism, and parasitism. Explain why Escherichia coli and Bacteroides thetaiotamicron are considered mutualists in the human microbiome. Could they also be opportunistic pathogens? Explain your answer. a. Symbiosis – “living together” (2 pts) b. Mutualism – both the microorganism and the host benefit (2 pts) c. Commensalism – the microorganism benefits from the host but the host is not harmed (2 pts) d. Parasitism – the microorganism benefits and harms the host (2pts) e. E. coli produces vitamins that human host can use, B. thetaiotamicron degrades fiber and produces short-chain fatty acids that are beneficial for the host. Many other possibilities (2 pts) f. Yes, some strains are able to cause infections. Under certain conditions, dysbiosis, or immunocompromised individuals, can result in infections. (2pts) 2. What can happen if members of the normal microbiota in the intestinal tract are killed, or their growth suppressed? Give an example of when this might happen. a. This can open up space/environment for potential pathogens to grow. (3 pts) b. It can reduce the utilization of foods etc. consumed (2 pts) c. Good example is C. difficile infections associated with treatments with antibiotics. (2 pts) 3. What is an advantage of using metagenomics over using culture methods when studying the normal human microbiome? a. Not all microorganisms can be cultured in the lab, usually only ~5% or fewer of the total diversity of microorganisms can be routinely cultured. Metagenomics does not require culturing the bacteria, and relies on the DNA that can be isolated as a proxy for the microorganisms. (4 pts) b. Metagenomics is safer and less expensive than culturing microorganisms. (2 points) 4. List the four steps needed to satisfy Koch's postulates. Why is it not possible to use Koch's postulates to demonstrate that Treponema pallidum is the causative agent of syphilis in humans? a. Isolate a pure culture of the putative pathogen from an infected host (usually an animal model). (1 pt) b. Infect a healthy host with the purified putative pathogen. (1 pt) c. Observe the same symptoms, signs of infection seen in the originally infected host. (1 pt) d. Re-isolate the same putative pathogen from the 2nd infected host. (1 pt) e. Treponema pallidum is only able to infect humans so there is no animal model to test on. It is unethical to intentionally infect human hosts with a pathogen that causes serious, difficult to treat pathogens. (1 pt). Downloaded by wik koza (wiktoriakoza2000@gmail.com) lOMoARcPSD|27457473

5. How do Shigella species enter intestinal epithelial cells? How does this entry path help Shigella avoid the human immune response? a. The Shigella bacteria can enter via the M cells and pass across the intestinal mucosal barrier where they can be taken up by macrophages. (2 pts) b. They can then “rocket” through and out of the macrophages on an actin tail. (3 pts) c. They can rocket into the intestinal epithelia cells and then continue to infect across the epithelial cells. (2 pts) d. When the Shigella are inside the cells they cannot be targeted by a antibodies, complement factors, or phagocytic cells. (2 pts) CHAPTER 18 What are possible outcomes for the SARS-CoV-2 virus in regards to human infections? Support your answers with evidence from "What the Future May Hold for the Coronavirus and Us" from NY Times, 12 October 2021 article. a. As the virus continues to spread in the population, over months or years of accumulated mutations the virus could evolve more transmissible and virulent strains. (3 points) b. As the virus continues to spread in the population, over months or years of accumulated mutations the virus could evolve to become less virulent. It could eventually become similar to other common cold coronaviruses. c. Myxoviruses of rabbits in Australia has shown evidence for become both less virulent and more virulent. There is a theory of balanced pathogenicity. (3 points) 2. Describe the role of vaccines in providing herd immunity. Why is herd immunity important? a. Vaccines allow a population or community to create an environment where there are very few susceptible hosts. The lack of susceptible hosts makes it hard for the virus to continue to spread in the community. (2 points) b. No everyone in a community can be vaccinated. If there is effective immunity this protects those individuals that cannot be vaccinated. Compare and contrast the characteristics of attenuated and inactivated vaccines . a. Attenuated vaccines are living, weakened viruses. They cause mild or no symptoms and generally cannot cause a full-blown infection in a healthy individual. They generally provide excellent protection from future infection because they result in an excellent immune response. (3 points) b. Inactivated vaccines contain dead virus or pieces (components) of a virus. It is not possible to cause any infection and they are generally extremely safe. However, they do not always result in a robust protective response in the immune system. (3 points) 4. Describe how the Pfizer and Moderna SARS-CoV-2 vaccines work to provide effective immunity in humans? Downloaded by wik koza (wiktoriakoza2000@gmail.com) lOMoARcPSD|27457473

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a. The Pfizer and Moderna vaccines are mRNA vaccines. The mRNA codes for the SARS-CoV-2 spike protein. (2 points) b. The mRNA is delivered in a lipid vesicle and is taken up by cells at the site of vaccination. (2 points) c. Your cells that take up the mRNA in the vaccine then express the SARS-CoV-2 spike protein on their surface and that is what is recognized by cells of the immune system. The practice of deliberately stimulating the immune system is called -vaccination The procedure developed by the Chinese to protect against smallpox was called - variolation Variolation is a procedure once used to protect against - small pox The scientist who made variolation safer and more effective was - Jenner The term vaccination- is a general term that would include the process of variolation, was coined by Pasteur AND comes from the Latin for cow, vacca. The virus originally used for vaccination against smallpox is named- c owpox The last case of naturally contracted smallpox occurred in - 1977 Almost all of the antibodies found in a newborn are - result of passive immunity Which antibodies cross the placenta and protect the fetus? - IgG Herd immunity- occurs in a population in which a large percentage of the population is immune Attenuated agents are- weakened but replicating microbes Attenuated agents . may induce immunity after a single dose. may cause disease in immunocompromised individuals multiply in the body. may revert or mutate to disease-causing strains. Downloaded by wik koza (wiktoriakoza2000@gmail.com) lOMoARcPSD|27457473

All of the choices are correct. Inactivated immunizing agents are prepared by treatment with - Formalin The Salk vaccine - contains inactivated virus and protects only against nervous system infection. Whole agent vaccines may contain - viruses and bacteria Toxoids are used in vaccines against - diphtheria Substances that are contained in vaccines to help induce a better immune response are called- adjuvants A recombinant vaccine is used to protect against - hep B The most common adjuvant is - alum For which of the following childhood diseases is a subunit vaccine recommende d - pertussis Which type of vaccine has been used in place of inactivated whole cell vaccine? - Acellular subunit The vaccine that is stable to heat, has little unwanted material and causes minimal side effects is called a(n)- peptide A poorly understood, yet promising type of vaccine that causes the host to produce microbial antigens for a short time involves the use of- DNA DNA vaccines work by- having the cell use the introduced DNA to make the microbial protein antigen. Monoclonal antibodies obtained from a hybridoma provide- large amount of an antibody that is specific for a particular epitope Injection of a single antigen usually results in production of - a number of antibodies each recognizing a different epitope. Downloaded by wik koza (wiktoriakoza2000@gmail.com) lOMoARcPSD|27457473

Monoclonal antibodies- have the same variable regions The change from negative serum, without antibodies specific to an infecting agent, to positive serum, containing antibodies against that infecting agent, is called- seroconversion Immunological tests may determine the presence of - antigen or antibody If a positive reaction is last observed at a dilution of 1:256, the titer is - 256 Serological tests are most often conducted in - micrometer plates An immune complex is defined as - antigen combined with antibody . Precipitation reactions depend on- the antigen having two or more epitopes Precipitation reactions carried out in agarose are called - immunodiffusion test Precipitation occurs when- antibody combines with antigen at optimal proportions Immunodiffusion tests A. allow detection of specific antigens. B. are a simple method that produces visible results in the zone of optimal proportion. C. allow quantitation of antigen concentrations. D. All of the choices are correct. Agglutination tests can be used to diagnose diseases caused by - bacteria, virus, fungus, hormones The serology test that may show the antigen-antibody complex as yellow-green under the microscope while using an ultraviolet light is known as the- fluorescent antibody test Anti-human-gamma-globulin antiserum is often used in- indirect ELISA, Western blot and indirect fluorescent antibody test Blood for transfusion is frequently tested for HIV by using the - ELISA method Downloaded by wik koza (wiktoriakoza2000@gmail.com) lOMoARcPSD|27457473

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Which of the following methods allows monitoring of the progressive destruction of CD4 T cells during an HIV infection by tagging the cells with specific antibodies to CD4 surface proteins and measuring their concentrations in serum? - FACS Which of the following tests allows the separation of cells according to their sizes, densities, and surface markers tagged by specific fluorescent antibodies?- Fluoresce- activated cell sorter Active immunity develops only after a natural infection and not after vaccination. -FALSE Attenuated agents often give rise to a long-lasting immunity . -TRUE Inactivated vaccines typically require booster shots. - TRUE Recombinant vaccines and inactivated vaccines typically require several shots to be effective. TRUE Alum is an adjuvant. - TRUE An adjuvant has been developed from lipid A. -TRUE The effectiveness of DNA vaccines stems from the effective production of antibodies against the naked DNA molecule. - FALSE DNA vaccines are dangerous due to the possibility of the DNA causing reversion in the inactivated pathogen.- FALSE The risk of serious illness from measles is 500 times greater than from vaccination against the disease.- TRUE Agglutination reactions utilize particles rather than molecules. - TRUE A monoclonal antibody is typically IgE and recognizes several epitopes. -FALSE What would be a primary advantage of passive immunity with diseases such as tetanus or botulism- Time. You can quickly neutralize the toxin with a passive administration of antibodies to save the patient's life when none is available for them to make their own active immune response. What would be a primary advantage of using an attenuated agent rather than just an antigen from that agent for a vaccine- An attenuated agent strongly stimulates both the humoral Downloaded by wik koza (wiktoriakoza2000@gmail.com) lOMoARcPSD|27457473

(antibody) AND cell-mediated (T cell) portions of the adaptive immune response, giving the best comprehensive long-term protection available. Since many childhood diseases such as mumps and measles are rare now within the United States, why is it still important for children to be immunized against them? A. If we lose herd immunity by removing mandatory vaccination, our population will become susceptible to these illnesses again in a short period of time. B. There is always the likelihood that an individual from another country could import one of these illnesses into the United States, sparking an outbreak of new infections, if we aren't all properly vaccinated. C. By keeping the population vaccinated, we keep incidence rates of these illnesses very low. This helps to protect people that cannot be vaccinated (very young children, pregnant women, immunocompromised individuals, the elderly). D. Many of these diseases are HIGHLY contagious, and commonly through respiratory droplet (airborne) transmission. This makes an outbreak within a susceptible population very possible. Keeping the population resistant through mandatory vaccination prevents this possibility. E ALL OPTIONS ARE CORRECT Would antibodies produced by a patient in response to infection be monoclonal, or polyclonal? - Since a single pathogen has multiple antigens, and each antigen has multiple epitopes, the responding antibodies to a whole pathogen would be polyclonal. Why is a false positive more significant in HIV testing of patients than in screening donated blood for transfusions?- A false-positive in BLOOD is easily retestable. This makes it less significant, because we would simply quickly retest the blood to verify its actual HIV statu s. Downloaded by wik koza (wiktoriakoza2000@gmail.com) lOMoARcPSD|27457473

CHAPTER 20 You are running a biotech company developing a new antibiotic XYZ. Your research team presents their data and you see that the new XYZ has a low therapeutic index. Is that a good or bad thing? Explain your answer. a. Bad/not a good thing (2 points) b. A low therapeutic index means that the concentration of XYZ that kills bacteria is also close to the concentration that causes serious side effects in the patient. That means there is a very limited dose range that can be used and the likelihood of bacteria developing resistance or the patient having serious side effects is very high (3 points) 2. List four targets in bacteria that can be targeted by antibiotics. Explain why each of the fours is a good target. Name an antibiotic or class of antibiotics that targets each of the four targets you listed. a. Cell wall synthesis, metabolic pathways, protein synthesis, RNA polymerases, cell membranes, other (4 points) b. These are all targets that can be selectively targeted because they differ in bacteria from the host/patient (2 points) c. Many options – see slide 14 Mechanisms of Action of Antibacterial Medications (4 points) 3 . What are three characteristics of antimicrobials that need to be considered when developing or prescribing antibiotics? Describe why these are important aspects to keep in mind. a. Half-life/metabolism, excretion, tissue distribution, blood-brain barrier, toxicity, bacterial suppression and dysbiosis (3 points) b. Antimicrobial may work well in the laboratory under controlled conditions, but working in the human body is more complex. Antibiotics need to be effective in humans (2 points) 4. Why are antibiotic resistant bacteria so frequent and a risk and concern to human health? List three mechanisms of antibiotic resistance. a. A single antibiotic resistant bacterium and grow quickly and cause serious infection. Adaptation and selection happen very quickly in microorganisms (2 points) b. Many options. See slide 42 and 43 - Resistance to Antimicrobial Medications Downloaded by wik koza (wiktoriakoza2000@gmail.com) lOMoARcPSD|27457473

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MULTIPLE CHOICE One of the earliest researchers to explore the use of chemicals to kill microbial pathogens was- Ehrlich he arsenic compound that proved highly effective in treating syphilis was called - Salvarsan The first example of an antimicrobial drug synthesized in the laboratory was- Salvarsan Prontosil effectively acted on streptococci when the drug was split by enzymes to produce - Sulfanilamide The use of Salvarsan and Prontosil to treat microbial infections were early examples of- Chemotherapy Penicillin was discovered by- Fleming The most effective form of penicillin is- G One of the earliest antimicrobials isolated from a bacterium was- Streptomycin An antibiotic made by microorganisms and modified by chemists is called - semi-synthetic The antimicrobials produced by some molds and bacteria are generally called- antibiotics The toxicity of a given drug is expressed as the- Therapeutic index A high therapeutic index is - Less toxic to the patient Drugs that are bacteriostatic - inhibit the growth of bacteria Antimicrobials that kill microorganisms have the suffix- cidal Antimicrobials that inhibit the growth of microorganisms have the suffix -static A ntibiotics that affect various strains of Gram-positive bacteria and various strains of Gram- negative bacteria are called- broad spectrum The rate of elimination of an antimicrobial is expressed as its - half line Antibiotics that are most likely to disrupt the normal microbiota are termed - broad spectrum Downloaded by wik koza (wiktoriakoza2000@gmail.com) lOMoARcPSD|27457473

Drugs that are more effective when taken together are called - synergistic If drugs are less effective when taken together than when each is taken separately, they are called- antagonistic Which of the following bacteria have an innate resistance to penicillin -mycoplasma Which of the following drugs target peptidoglycan? - Penicillin, cephalosporin, vancomycin and bacitracin All members of the penicillin family have - betalactam rings Penicillin-binding proteins- a re enzymes and are involved in cell wall synthesis Beta lactamases- break beta- lactam ring The major class(es) of antibiotics that inhibit protein synthesis is/are - minoglycosides, tetracyclines, AND macrolides. Inhibitors of protein synthesis typically key on - ribosomes Which is true of aminoglycosides- They irreversibly bind to the 30S ribosomal subunit AND they are bactericidal. Fluoroquinolones typically target- DNA gyrase Sulfonamide and trimethoprim are both - examples of metabolic inhibitors AND folate inhibitors. Folic acid is ultimately used in the synthesis of - coenzymes Sulfonamides are similar in structure to - PABA Sulfonamides work as- competitive inhibitors. Trimethoprim and sulfonamides have a- synergistic effect Mycolic acids are targeted by isoniazid in the treatment of- M tuberculosis Downloaded by wik koza (wiktoriakoza2000@gmail.com) lOMoARcPSD|27457473

The lowest concentration of a drug that prevents growth of a microorganism - minimum inhibitory concentration The minimum bactericidal concentration is the lowest concentration of a specific antimicrobial drug that kills _______ of a specific type of bacteria- 99.9 % The diffusion bioassay- is similar in principle to the Kirby-Bauer AND determines the concentration of antimicrobial in a fluid. Which test is used to determine the susceptibility of a microorganism to an antimicrobial? - Kirby Bauer test The zone size obtained in the Kirby-Bauer test is influenced by the drug’s - size, stability, concentration . A commercial modification of the disk diffusion test is called the- E test Bacteria may become antibiotic resistant due to - D rug-inactivating enzymes. B. alteration in the target molecule. C. decreased uptake of the drug. D. increased elimination of the drug. E. All of the choices are correct. Spontaneous development of resistance to a particular antimicrobial is difficult if the drug - binds to several sites on the target molecule AND targets several different molecules The most common method of transfer of antimicrobial resistance is through the use of - R plasmids Compliance problems are leading to a large increase in antibiotic resistant strains Myobacterium Antiviral drugs may target - uncaring, nucleic acid synthesis AND viral assembly The target of most antifungal drugs is - ergosterol Downloaded by wik koza (wiktoriakoza2000@gmail.com) lOMoARcPSD|27457473

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The key characteristic of a useful antimicrobial is selective toxicity. - TRUE Antimicrobials that have a high therapeutic index are less toxic to the patient. - TRUE Broad-spectrum antibiotics have minimal effect on the normal microbiota. - FALSE Certain antimicrobials may be life-threatening. - TRUE Drugs that target peptidoglycan do not affect eukaryotes. - TRUE Beta-lactam drugs are only effective against growing bacteria. - TRUE The MBC may be determined by an extension of the MIC. - TRUE Antimicrobial resistance can be due to spontaneous mutation or gene acquisition. - TRUE Viruses are very effectively treated with antibiotics. - FALSE Antifungal drugs usually target the cell membrane. - TRUE In what clinical situation is it most appropriate to use a broad-spectrum antimicrobial? -In a case of bacterial meningitis. The infection spreads so quickly that we must treat it with an antibacterial drug as quickly as possible. We don't have time to determine which drug will work best, because the patient will die in the meantime. Why would antimicrobials that have toxic side effects be used at all (select the BEST reason)?- We want the largest possible number of choices of drugs in case a microbe shows resistance. With more possible weapons (even toxic ones), we have greater ability to eliminate infections. Why would co-administration of a bacteriostatic drug interfere with the effects of penicillin?- Penicillin interferes with cell wall production/stabilization by cross-linking of peptidoglycan. As such, it only works when the cells are actively replicating and MAKING new peptidoglycan. A bacteriostatic drug works by shutting down replication, holding the cells "static." This would interfere with the mode of action required by the penicillin . Downloaded by wik koza (wiktoriakoza2000@gmail.com) lOMoARcPSD|27457473

Why would it be important for the Kirby-Bauer disc diffusion test to use a standard concentration (number of cells in the sample) of each of the bacterial strains being tested?- If you were to use one strain that was stationary phase (high concentration, replicating very slowly or not at all), and another strain that was just beginning log phase (low concentration but replicating quickly), you could see dramatically different results in the disc diffusion test. This could skew your interpretations of resistance/susceptibility. Explain how using a combination of two antimicrobial drugs helps prevent the development of spontaneously resistant mutants. -It is highly unlikely that the microbe might spontaneously develop two specific mutations to resist the effects of a pair of drugs. As such, even if one drug is resisted by the microbe, the second drug will eliminate the mutated microbe, thus preventing the development of spontaneously resistant mutants overall. Why are nucleoside analogs active only against replicating viruses? -Nucleoside analogs work by being incorporated into growing strands of DNA/RNA. This indirectly shuts down further extension of these chains. However, new strands of viral DNA/RNA are only being created when the virus is replicating. As such, these drugs can only work when the virus is actively replicating as well. Downloaded by wik koza (wiktoriakoza2000@gmail.com) lOMoARcPSD|27457473

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micro-bio-exam2-brooklyn-college

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