Microbiology Ch. 15
Which of these eukaryotic molecules/structures can be responsible for movement of bacteria within host cells?
- Actin molecules = be responsible for movement of bacteria within host cells. - Some bacteria can use actin to propel themselves through the host cell cytoplasm and from one host cell to another = cadherins (bridge junctions) - The condensation of actin on one end of the bacteria propels them through the cytoplasm.
Compare and contrast the following aspects of endotoxins and exotoxins: bacterial source, chemistry, toxigenicity, and pharmacology. Give an example of each toxin.
- Bacterial source: Exotoxin = Gram +; Endotoxin = Gram - - Source: Exotoxin = proteins; Endotoxin = lipid A - Chemistry: Exotoxin = high; Endotoxin = low - Toxigenicity: Exotoxin = destroy certain; Endotoxin = systemic - pharmacology: Exotoxin = cell parts or physiological functions; Endotoxin = fever, weakness, aches and shock - Example: Exotoxin = Botulinum toxin; Endotoxin = Salmonellosis
How are capsules and cell wall components related to pathogenicity? Give specific examples.
- Encapsulated bacteria can resist phagocytosis and continue growing. Ex: Streptococcus pneumoniae and Klebsiella pneumoniae produce capsules that are related to their virulence. M protein found in the cell walls of Streptococcus pyogenes and mycolic acid in the cell walls of Mycobacterium help these bacteria resist phagocytosis.
Describe how hemolysins, leukocidins, coagulase, kinases, hyaluronidase, siderophores, and IgA proteases might contribute to pathogenicity.
- Hemolysins lyse red blood cells; hemolysis might supply nutrients for bacterial growth. - Leukocidins destroy neutrophils and macrophages that are active in phagocytosis; this decreases host resistance to infection. - Coagulase causes fibrinogen in blood to clot; the clot may protect the bacterium from phagocytosis and other host defenses. - Bacterial kinases break down fibrin; kinases can destroy a clot that was made to isolate the bacteria, thus allowing the bacteria to spread. - Hyaluronidase hydrolyzes the hyaluronic acid that binds cells together; this could allow the bacteria to spread through tissues. - Siderophores take iron from host iron-transport proteins, thus allowing bacteria to get iron for growth. - IgA proteases destroy IgA antibodies; IgA antibodies protect mucosal surfaces.
Describe the factors contributing to the pathogenicity of fungi, protozoa, and helminths.
- Pathogenic fungi do not have specific virulence factors; capsules, metabolic products, toxins, and allergic responses contribute to the virulence of pathogenic fungi. - Some fungi produce toxins that, when ingested, produce disease. - Protozoa and helminths elicit symptoms by destroying host tissues and producing toxic metabolic wastes.
Compare pathogenicity with virulence.
- The ability of a microorganism to produce a disease is called pathogenicity. - The degree of pathogenicity is virulence.
siderophores
- To obtain iron, some pathogens secrete proteins called siderophores - extract iron from transport proteins (Hb, transferrin) then enter cell as complex or iron only OR direct uptake of iron transport proteins via receptors - take iron away from iron-transport proteins by binding iron more tightly
How can viruses and protozoa avoid being killed by the host's immune response?
- Viruses avoid the host's immune response by growing inside host cells; some can remain latent in a host cell for prolonged periods. - Some protozoa avoid the immune response by mutations that change their antigens.
Streptococcus mutans
- bacterium that plays a key role in tooth decay, attaches to the surface of teeth by its glycocalyx - produces enzyme glucosyltransferase, converts glucose into a sticky polysaccharide called dextran, which forms the glycocalyx
parenteral route
- microorganisms gain access to the body when they are deposited directly into the tissues beneath the skin or into mucous membranes when these barriers are penetrated or injured ex: Punctures, injections, bites, cuts, wounds, surgery, and splitting of the skin or mucous membrane due to swelling or drying
adhesins
- surface molecule that helps attach pathogen and host, also called ligands that bind specifically to complementary protein receptors on the cells of certain host tissues. - made of glycoproteins or lipoproteins - located on a 1) pili, fimbriae, and flagella 2) capsules 3) biofilms 4) viral spikes 5) mechanical devices on worms (suckers, hooks)
portals of exit
- usually the same as entry = allows spreading through population 1) respiratory = coughing and sneezing 2) gastrointestinal = feces and saliva 3) genitourinary = urine and secretions 4) skin = sloughed cells 5) blood = biting arthropods, needles, syringes
LD50
-potency of a toxin is often expressed as the LD50 (lethal dose for 50% of a sample population). - This means that the smaller the dose, the more potent the toxin
cell wall components (3)
1) M-protein = heat and acid resistant protein on cell surface and fimbrial, resistant to phagocytosis 2) fimbriae and opa = protein to attach to host cells (N. gonorrhoeae) 3) mycolic acid = waxy lipid = cell wall of M. tuberculosis = digest phagocytes
portals of entry: mucous membrane (4)
1) conjunctiva = covers eyeball and lines eyelids 2) respiratory tract = most common! droplet inhalation of moisture and dust into mouth and nose 3) GI tract = ingesting contaminated food or water; contaminated fingers; microbes that survive bile cause disease = pathogens eliminated with feces = transmitted to other host 4) genitourinary tract: contracted sexually; cause STI
how does bacteria use host cell's cytoskeleton to enter the cell?
1) invasins 2) actin - inside the host cell
cytopathic effects of viral infections (9)
1) macromolecular synthesis within host cell stops 2) host cell lysosomes release their enzymes = destruction of intracellular contents and host cell death (cytocidial effects) 3) inclusion bodies = help identify causative agents in cytoplasm, viral parts ex: rabies 4)synctium = cell fusion to produce large multinucleate cells produced from infection of viruses 5) change in host cell's fxn with no visible change in infected cells 6) induce antigenic changes on surface of infected cells = elicit host antibody response against infected cell = target cell for destruction by host's IS 7) chromosomal change in host cell 8) cancer transform host cells = don't recognize contact inhibition = cells keep growing 9) produce interferons = inhibit synthesis of viral proteins and kill virus infected host cell by apoptosis
how do viruses evade the host immune system?
1) multiply inside the cell where components of IS can't detect them 2) rabies virus spikes mimic ACh = virus can bind to ACh receptors then enter host cell along with neurotransmitter 3) HIV suface is folded = binding sites to T cells within fold 4) CD4 long and slender = can reach attachment sites on virus where larger ABs can't make contact to form Ag-Ab complexes to tag foreign cell/molecule for destruction by phagocytes and complement
mechanism of microbes avoiding destruction by phagocytosis (4)
1) using host's nutrients = siderophores 2) direct damage in immediate vicinity of invasion 3) producing toxins, transported by blood and lymph that damages sites far removed from original site of invasion 4) inducing hypersensitivity reactions
All of the following bacteria release endotoxin EXCEPT A. Clostridium botulinum. B. Neisseria meningitidis. C. Proteus vulgaris. D. Haemophilus influenzae. E. Salmonella Typhi.
A. Clostridium botulinum.
Given the following LD50 values for Bacillus anthracis, through which portal of entry is it easiest to get anthrax? A. Cutaneous: 50 endospores B. All of the listed choices are equally easy portals of entry. C. Ingestion: 1 million endospores D. Inhalation: 20,000 endospores
A. Cutaneous: 50 endospores - The ID50 through the skin (cutaneous anthrax) is 10 to 50 endospores; - the ID50 for inhalation anthrax is inhalation of 10,000 to 20,000 endospores; -the ID50 for gastrointestinal anthrax is ingestion of 250,000 to 1,000,000 endospores. - These data show that cutaneous anthrax is significantly easier to acquire than either the inhalation or the gastrointestinal forms.
You conduct a Limulus amebocyte lysate (LAL) assay on a sample of fluid that should be sterile. The result is positive. What does this indicate? A. Endotoxin is present. B. Gram-negative bacteria are growing. C. The fluid is not sterile. D. Gram-positive bacteria are growing in the sample.
A. Endotoxin is present. - important to have a sensitive test to identify the presence of endotoxins in drugs, medical devices, and body fluids. - Materials that have been sterilized may contain endotoxins, even though no bacteria can be cultured from them. - One such laboratory test is called the Limulus amebocyte lysate (LAL) assay, which can detect even minute amounts of endotoxin.
Which one of these is NOT an example of pathogen entry via the parenteral route? A. Infection of a hair follicle B. Entry through a break in the skin caused by a cut C. Injection of the pathogen via a contaminated needle D. Injection via the bite of an infected insect
A. Infection of a hair follicle -Unbroken skin is impenetrable by most microorganisms
Which of the following statements about adherence is true? A. Most bacterial adhesins are glycoproteins or lipoproteins. B. Adhesins are always located on the bacterium's cell membrane. C. Most bacteria can adhere to any cell in the host. D. The host cell receptors for bacterial adhesins are usually proteins.
A. Most bacterial adhesins are glycoproteins or lipoproteins.
Which of the following organisms does NOT enter through the gastrointestinal tract? A. Rubella virus B. Hepatitis A virus C. Vibrio cholera D. Trichinella spiralis
A. Rubella virus - goes through respiratory tract
Which of these substances does NOT protect a bacterium from phagocytosis? A. Siderophore B. Capsule C. Leukocidin D. M protein
A. Siderophore - They are released and take the iron away from iron-transport proteins by binding the iron even more tightly. - Once the ironsiderophore complex is formed, it is taken up by siderophore receptors on the bacterial surface. - Then the iron is brought into the bacterium. - They do not protect a bacterium from phagocytosis.
Which of the following is an accurate statement about A-B toxins? A. They are proteins. B. They are a type of endotoxin. C. The A and B components must remain attached in order to exert their effects on the cell. D. The A component binds to a receptor on the host cell.
A. They are proteins. - A-B toxins were the first toxins to be studied intensively and are so named because they consist of two parts designated A and B, both of which are polypeptides (proteins). - Most exotoxins are A-B toxins.
The scum that builds up on shower doors, the formation of dental plaque on teeth, and the algae growth on the walls of swimming pools are all examples of __________. A. biofilms B. fimbriae C. glycocalyces D. capsules
A. biofilms - forms when microbes adhere to a particular surface that is typically moist and contains organic matter.
All of the following are methods of avoiding host antibodies EXCEPT A. membrane-disrupting toxins. B. IgA proteases. C. antigenic changes. D. inducing endocytosis. E. invasins.
A. membrane-disrupting toxins.
To prevent the disease botulism, which is caused by ingesting an exotoxin, it is necessary to
A.Boil food prior to consumption - exotoxin = protein = denatured
What could cover up attachment points on the organism thereby preventing phagocytosis by host cell? 1.M protein 2.capsules 3.Adhesins 4.Mycolic acid 5.Biofilms
All but #3: viscous extracellular polymeric substance of biofilms - may prevent phagocyte entrance, cover antigens, P. aeruginosa EPS (extraceulluar polymery substance) kills phagocytes!
Which of the following would be an example of an infection initiated via the parenteral route? A. An individual contracts gonorrhea as a result of unprotected sex. B. An individual contracts hepatitis B from an accidental stick with a contaminated needle. C. An individual contracts a hookworm infection as a result of walking around outside barefoot. D. An individual contracts a gastrointestinal infection by consuming contaminated water.
B. An individual contracts hepatitis B from an accidental stick with a contaminated needle.
Which of the following statements is FALSE? A. Hemolysins lyse red blood cells. B. Coagulase destroys blood clots. C. Kinase destroys fibrin clots. D. Hyaluronidase breaks down substances between cells. E. Leukocidins destroy neutrophils.
B. Coagulase destroys blood clots.
Which of these events leads to all of the others in a pyrogenic (fever) response? A. The hypothalamus releases prostaglandins. B. Endotoxin is released from the cell wall of gram-negative bacteria. C. IL-1 is released by macrophages. D. IL-1 travels via the blood to the hypothalamus. E. The body's thermostat is set to a higher level, and fever occurs.
B. Endotoxin is released from the cell wall of gram-negative bacteria = leads to all of the other listed stages in a pyrogenic response - bacterium is degraded in a vacuole, releasing endotoxins that induce the macrophage to produce cytokines, interleukin-1, and tumor necrosis factor alpha. - The cytokines are released into the bloodstream by the macrophages, through which they travel to the hypothalamus, the temperature control center of the brain. - The cytokines induce the hypothalamus to produce prostaglandins, which reset the body's "thermostat" to a higher temperature, producing fever.
Which one of these substances would NOT be produced at the same time as coagulase? A. Hemolysin B. Fibrinolysin C. Capsules D. Fimbriae
B. Fibrinolysin (streptokinase) = bacterial enzyme that breaks down fibrin and thus digests clots formed by the body to isolate the infection.
Which of these statements is NOT true for bacterial capsules? A. Pathogenic and nonpathogenic bacteria can produce capsules. B. Immune system antibodies are not produced against a capsule. C. The importance of the capsule to virulence for Streptococcus pneumoniae can be determined because there are strains both with and without the capsule. D. Capsules related to virulence are produced by the causative agents of anthrax and bubonic plague. E. For Streptococcus pneumoniae, the encapsulated strain is more virulent.
B. Immune system antibodies are not produced against a capsule. - human body can produce antibodies against the capsule, and when these antibodies are present on the capsule surface, the encapsulated bacteria are easily destroyed by phagocytosis.
Which of these statements is true regarding portals of exit? A. Polioviruses most often use the respiratory portal of exit. B. In most cases, a microbe uses the same portal for both entry and exit. C. The urinary tract is the most common portal of exit. D. The portal of exit for tuberculosis is the skin.
B. In most cases, a microbe uses the same portal for both entry and exit. - microbes leave the body via specific routes called portals of exit in secretions, excretions, discharges, or tissue that has been shed.
Which of the following statements about M protein is FALSE? A. It is a protein. B. It is readily digested by phagocytes. C. It is found on Streptococcus pyogenes. D. It is heat- and acid-resistant. E. It is found on fimbriae.
B. It is readily digested by phagocytes. - prevents phagocytosis
In mice, the LD50 for staphylococcal enterotoxin is 1350 ng/kg, and the LD50 for Shiga toxin is 250 ng/kg. Which of the following statements is true? A. More organisms of Staphylococcal bacteria must be ingested to cause infection, as compared to Shigella bacteria. B. Shiga toxin is more lethal than staphylococcal enterotoxin. C. Staphylococcal enterotoxin is the more lethal of the two toxins. D. The parenteral route is the preferred portal entry for Shigella bacteria.
B. Shiga toxin is more lethal than staphylococcal enterotoxin.
What do hyaluronidase & kinase have in common? A. They both directly prevent phagocytosis. B. They are both enzymes involved in evading host defense. C. They both break down components of the extracellular matrix. D. They are both critical components of microbial capsules. E. All are correct.
B. They are both enzymes involved in evading host defense.
Which of the following is NOT a cytopathic effect of viruses? A. increased cell growth B. toxin production C. inclusion bodies forming in the cytoplasm or nucleus D. host cells fusing to form multinucleated syncytia E. cell death
B. toxin production - does the most damage by bacteria - toxin transported by blood or lymph -> produce pathogenic properties = fever, shock, diarrhea - exotoxins and endotoxins = based on position relative to the cell
Which of the following cell wall components do/does NOT contribute to virulence? A. Opa B. fimbriae C. All of the listed choices contribute to virulence. D. mycolic acids E. M protein
C. All of the listed choices contribute to virulence. - Virulence is the degree of pathogenicity. - To cause disease, most pathogens must gain access to the host, adhere to host tissues, penetrate or evade host defenses, and damage the host tissues
Which of the following toxins is NOT produced by a bacterium as a result of lysogenic conversion? A. Staphylococcal enterotoxin B. Diphtheria toxin C. Endotoxin D. Botulinum neurotoxin
C. Endotoxin - One outcome of lysogeny is that the host bacterial cell and its progeny may exhibit new properties encoded by the bacteriophage DNA due to a prophage. - As a result of lysogenic conversion, the bacterial cell is immune to infection by the same type of phage. - Among the bacteriophage genes that contribute to pathogenicity are for example the genes for diphtheria toxin, erythrogenic toxins, and staphylococcal enterotoxin A.
Bacteriophages can contribute to bacterial virulence because they can A.Carry plasmids B.Produce toxins C.Give new gene sequences to the host bacteria D.Kill the bacteria causing release of endotoxins
C. Give new gene sequences to the host bacteria - how? Lysogenic conversion (genes on prophage or specialized transduction (genes adjacent to prophage)
The LD50 of Vibrio cholerae is 108 cells through the oral route. If the bacterial cells are ingested with bicarbonate, the LD50 drops to 104. Which of these explanations is the most likely? A. Sodium bicarbonate inactivates Vibrio cholerae. B. Sodium bicarbonate decreases the virulence of Vibrio cholerae. C. Stomach acid decreases the virulence of Vibrio cholerae. D. Vibrio cholerae makes toxins only in the presence of stomach acid. E. Stomach acid increases the virulence of Vibrio cholerae.
C. Stomach acid decreases the virulence of Vibrio cholerae by raising the pH of the stomach content and decreasing the number of cells.
Which of these conditions would NOT affect the ability of Streptococcus mutans to attach to teeth? A. The lack of the enzyme glucosyltransferase B. The lack of a glycocalyx C. The absence of Actinomyces, a bacterium that can be part of dental plaque D. The lack of sucrose E. The inability to form dextran
C. The absence of Actinomyces, a bacterium that can be part of dental plaque - Actinomyces have fimbriae that adhere to the glycocalyx of S. mutans. The combination of S. mutans, Actinomyces, and dextran makes up dental plaque and contributes to dental caries. S. mutans can independently attach to the surface of teeth and the absence of Actinomyces would NOT affect the ability to attach.
Which statement is NOT true of endotoxins? A. They can lyse amebocytes found in crab hemolymph. B. They are more heat-resistant than exotoxins are. C. They are eliminated from the body as a result of antitoxin production. D. Endotoxins are produced by Neisseria meningitidis and E. coli. E. They can induce chills, fever, aches, clotting, shock, and miscarriage.
C. They are eliminated from the body as a result of antitoxin production. - The body produces antibodies called antitoxins that provide immunity to exotoxins, NOT endotoxins.
Which statement is true of endotoxins? A. They increase blood pressure. B. They are produced by gram-positive bacteria. C. They are released upon cell lysis. D. They are disease specific. E. They are proteins.
C. They are released upon cell lysis.
Which one of these pairs is NOT correctly matched? A. IgA protease; digest antibodies B. leukocidin; lyses WBC membranes C. coagulase; lyses fibrin clots D. collagenase; breaks down connective tissue E. siderophore; traps iron
C. coagulase; lyses fibrin clots - Coagulases are bacterial enzymes that coagulate (clot), not lyse, the fibrinogen in blood.
Which of these viral cytopathic effects is most likely to be associated with the development of cancer? A. stimulation of interferon production B. cell death C. loss of contact inhibition D. inclusion bodies E. cell fusion
C. loss of contact inhibition - Viruses capable of causing cancer transform host cells. - Transformation results in an abnormal, spindle-shaped cell that does not recognize contact inhibition, meaning cells don't stop growing when they come in close contact with other cells. - The loss of contact inhibition results in unregulated cell growth.
How can capsules enable bacteria to evade the immune system?
Capsules block the complement biding sites on the surface of the pathogen = prevents phagocytosis - composed of polysaccharides similar to host's = not seen as foreign by IS ex: S. pyogenes = pneumonia
Which of these statements about toxoids is INCORRECT? A. Exotoxins can be altered by heat or chemicals to form toxoids. B. Toxoids stimulate the body to produce antitoxins without causing disease. C. Diphtheria and tetanus can be prevented by toxoid vaccinations. D. Gram-negative septic shock is commonly prevented by toxoids.
D. Gram-negative septic shock is commonly prevented by toxoids. - Gram-negative bacteria cause endotoxic shock and toxoids are altered exotoxins.
Which of the following organisms is NOT discharged through the respiratory tract? A. Bordetella pertussis B. Measles virus C. Histoplasma capsulatum D. Poliovirus
D. Poliovirus - discharged through the gastrointestinal tract
Which of the following organisms is NOT discharged through the respiratory tract? A. Bordetella pertussis B. Histoplasma capsulatum C. Measles virus D. Poliovirus
D. Poliovirus - it is discharged through the gastrointestinal tract.
Which pathogen and virulence factor are mismatched? A. Neisseria gonorrhoeae - IgA protease B. Streptococcus pneumoniae - capsule C. Clostridium - hyaluronidase D. Shigella sonnei - coagulase E. Streptococcus pyogenes - M protein
D. Shigella sonnei - coagulase
Based on the following LD50 values, which microbe is the most virulent? Assume each bacterium enters through the appropriate portal of entry. A. Vibrio cholerae: 108 cells B. Cryptosporidium: 50 cells C. E. col O157: 1000 cells D. Shigella: 10 cells
D. Shigella: 10 cells -The potency of a toxin is often expressed as the LD50 (lethal dose for 50% of a sample population). - A much smaller dose of the Shiga toxin would be needed to cause symptoms as compared to the other organisms = Shigella would be the most virulent.
Which of the following statements about exotoxins is generally FALSE? A. They have specific methods of action. B. They are more potent than endotoxins. C. They are produced by gram-positive bacteria. D. They are resistant to heat. E. They are composed of proteins.
D. They are resistant to heat.
The ID50 for cutaneous anthrax due to Bacillus anthracis is 10 to 50 endospores, while the ID50 for inhalation anthrax is 10,000 to 20,000 endospores. This means that __________. A. not enough information is available to answer this question B. both cutaneous and inhalation anthrax can easily be acquired C. inhalation anthrax is easier to acquire than cutaneous anthrax D. cutaneous anthrax is easier to acquire than inhalation anthrax E. neither cutaneous or inhalation anthrax can easily be acquired
D. cutaneous anthrax is easier to acquire than inhalation anthrax - virulence of a microbe is often expressed as the ID50 (infectious dose for 50% of a sample population). - Bacillus anthracis can cause infection via three different portals of entry: 1) The ID50 through the skin (cutaneous anthrax) is 10 to 50 endospores; 2) the ID50 for inhalation anthrax is inhalation of 10,000 to 20,000 endospores; 3) the ID50 for gastrointestinal anthrax is ingestion of 250,000 to 1,000,000 endospores.
All of the following are examples of entry via the parenteral route EXCEPT A. bite. B. skin cut. C. injection. D. hair follicle. E. surgery.
D. hair follicle.
All of the following contribute to a pathogen's invasiveness EXCEPT A. hyaluronidase. B. cell wall components. C. coagulases. D. toxins. E. capsules.
D. toxins.
Which of these is a cell wall component that contributes to invasiveness? A. Hemolysin B. Coagulase C. Endotoxin D. M protein
E. M protein - a heat resistant and acid resistant protein, is found on both the cell surface and fimbriae. - It mediates attachment of the bacterium to epithelial cells of the host and helps the bacterium resist phagocytosis by white blood cells. - The M protein thereby increases the virulence of the microorganism and contributes to invasiveness.
Capsules play a role in the virulence of all of the following EXCEPT __________. A. Yersinia pestis B. Bacillus anthracis C. Klebsiella pneumoniae D. Haemophilus influenzae E. Mycobacterium tuberculosis
E. Mycobacterium tuberculosis -The waxy lipid (mycolic acid) that makes up the cell wall increases virulence by resisting digestion by phagocytes, and the bacteria can even multiply inside phagocytes.
Which disease is correctly matched with the common portal of entry? A. Measles; parenteral route B. Chlamydia; skin C. Hookworm; mucous membranes of genitourinary tract D. Influenza; mucous membranes of genitourinary tract E. Poliomyelitis; mucous membranes of gastrointestinal tract
E. Poliomyelitis; mucous membranes of gastrointestinal tract - Microorganisms can gain access to the gastrointestinal tract in food and water and via contaminated fingers. - Most microbes that enter the body in these ways are destroyed by hydrochloric acid and enzymes in the stomach or by bile and enzymes in the small intestine. Those that survive can cause disease. - Microbes in the gastrointestinal tract can cause poliomyelitis, hepatitis A, typhoid fever, amebic dysentery, giardiasis, shigellosis (bacillary dysentery), and cholera. - These pathogens are then eliminated with feces and can be transmitted to other hosts via contaminated water, food, or fingers.
Which of the following statements is NOT true of A-B exotoxins? A. They consist of two polypeptide components. B. The A portion of the toxin is the active component. C. The B portion of the toxin binds to surface receptors on host cells. D. Many exotoxins are A-B toxins. E. They are produced only by gram-negative bacteria.
E. They are produced only by gram-negative bacteria. - Most exotoxins are A-B toxins. - Both gram-positive and gram-negative bacteria commonly may produce exotoxins.
Which of the following contributes to the virulence of a pathogen? A. numbers of microorganisms that gain access to a host B. evasion of host defenses C. numbers of microorganisms that gain access to a host and evasion of host defenses D. toxin production E. numbers of microorganisms that gain access to a host, evasion of host defenses, and toxin production
E. numbers of microorganisms that gain access to a host, evasion of host defenses, and toxin production
The graph below shows confirmed cases of enteropathogenic E. coli. Why is the incidence seasonal?
E.coli is gram -, rod shaped bacteria that causes diarrhea - it seems to have subsided as the season changed from fall to winter and to early spring - we can assume that the results were more accurate than the samples in Jan = error factor - bacterial level gradually increased from Jan to July = highest level and then gradually decreased to Sept - through the seasons the overall levels of E.coli decreased
1) Botulinum (in mice): LD50 = 0.03 ng/kg 2) Staphylococcal enterotoxin: LD50 = 1.35 mg/kg 3) Shiga toxin: LD50 = 250 ng/kg Which is the least potent toxin?
Staphylococcal bc least potent = requires more
Which of the following virulence factors would be found in Staphylococcus aureus?
Staphylokinase
How are superantigens different from other types of exotoxins?
Superantigens cause an overstimulation of the host immune system.
How do superantigens enable pathogens to hide from the immune system if they actually stimulate the immune system?
They cause the immune system to produce an exaggerated response, distracting it from the actual pathogen.
__________ are toxins modified to retain their ability to induce antibody formation but lose their toxicity.
Toxoids - toxins modified to retain their ability to induce antibody formation but lose their toxicity - body produces antibodies called antitoxins that provide immunity to exotoxins. - When exotoxins are inactivated by heat or by formaldehyde, iodine, or other chemicals, they no longer cause the disease but can still stimulate the body to produce antitoxins. - When toxoids are injected into the body as a vaccine, they stimulate antitoxin production so that immunity is produced.
Ergot and aflatoxin are toxins sometimes found in grains contaminated with fungi. (T/F)
True
Which of the following microorganisms actually grows inside the macrophage?
Tuberculosis bacterium
Bacterium; ID50: - E. coli O157:H7; 20 - Legionella pneumophila; 1 - Shigella; 10 - Treponema pallidum; 57 a) Which organism in the table most easily causes an infection? b) Which organism in the table causes the most severe disease?
a) Legionella pneumophila b) It cannot be determined from the information provided.
The earliest smallpox vaccines were infected tissue rubbed into the skin of a healthy person. The recipient of such a vaccine usually developed a mild case of smallpox, recovered, and was immune thereafter. What is the most likely reason this vaccine did not kill more people? a. Skin is the wrong portal of entry for smallpox. b. The vaccine consisted of a mild form of the virus. c. Smallpox is normally transmitted by skin-to-skin contact. d. Smallpox is a virus. e. The virus mutated.
a. Skin is the wrong portal of entry for smallpox.
Explain how drugs that bind each of the following would affect pathogenicity: a. iron in the host's blood b. Neisseria gonorrhoeae fimbriae c. Streptococcus pyogenes M protein
a. Would inhibit bacteria. b. Would prevent adherence of N. gonorrhoeae. c. S. pyogenes would not be able to attach to host cells and would be more susceptible to phagocytosis.
Which of the following does NOT contribute to fungal disease? a. cell walls b. toxins c. capsules d. allergic response of the host
a. cell walls
An encapsulated bacterium can be virulent because the capsule a. resists phagocytosis. b. is an endotoxin. c. destroys host tissues. d. kills host cells. e. has no effect; because many pathogens do not have capsules, capsules do not contribute to virulence.
a. resists phagocytosis.
pathogenicity
ability of a pathogen to cause disease by overcoming the host defenses
The fimbriae of Neisseria gonorrhea and enteropathogenic E. coli are examples of
adhesins and ligands. Submit
inclusion bodies
adjacent infected cells fused to make a large multinucleate cell in cytoplasm or nucleus of infected cell
IgA proteases
antibody that prevents attachment of microbe to mucosal membrane produced by N. gonorrhoeae
The ability of some microbes, such as Trypanosoma or Giardia to alter their surface molecules and evade destruction by the host's antibodies is called
antigenic variation.
coagulase
bacterial enzyme that coagulate (clot) the fibrinogen in blood - converts fibrinogen -> fibrin -> blood clot
lysogeny
bacteriophage -> prophage after putting their DNA into bacterial chromosome -> latent and don't cause lysis of bacterium - lysogenic conversion = host bacterial cell and progeny = new properties = bacterial cell immune to infection by same type of phagex
The cyanobacterium Microcystis aeruginosa produces a peptide that is toxic to humans. According to the graph below, during what season is this bacterium most toxic?
bacterium is most toxic when exposed to extremely low intensity light or in the absence of light.
Botulism is caused by ingestion of a proteinaceous exotoxin; therefore, it can easily be prevented by
boiling food prior to consumption.
Which of the following statements is true? a. The primary goal of a pathogen is to kill its host. b. Evolution selects for the most virulent pathogens. c. A successful pathogen doesn't kill its host before it is transmitted. d. A successful pathogen never kills its host.
c. A successful pathogen doesn't kill its host before it is transmitted.
What is the LD50 for the bacterial toxin tested in the example below? a. Dilution (μg/kg): 6; No. of Animals Died: 0; No. of Animals Survived: 6 b. Dilution (μg/kg): 12.5; No. of Animals Died: 0; No. of Animals Survived: 6 c. Dilution (μg/kg): 25; No. of Animals Died: 3; No. of Animals Survived: 3 d. Dilution (μg/kg): 50; No. of Animals Died: 4; No. of Animals Survived: 2 e. Dilution (μg/kg): 100; No. of Animals Died: 6; No. of Animals Survived: 0
c. Dilution (μg/kg): 25; No. of Animals Died: 3; No. of Animals Survived: 3
fungal disease symptoms
chronic infections = allergic responses - ingestion of Trichothecenes = fungal toxin inhibit protein synthesis = headaches, chills, nausea - proteases virulence factor degrade host cell membrane to allow attachment ex: candida - capsule prevents phagocytosis - ergotism = ergot toxin = hallucinations - LSD by C. purpurea - Aflatoxin= carcinogenic properties when ingested
Which of the following does not represent the same mechanism for avoiding host defenses as the others? a. Rabies virus attaches to the receptor for the neurotransmitter acetylcholine. b. Salmonella attaches to the receptor for epidermal growth factor. c. Epstein-Barr (EB) virus binds to the host receptor for complement. d. Surface protein genes in Neisseria gonorrhoeae mutate frequently. e. none of the above
d. Surface protein genes in Neisseria gonorrhoeae mutate frequently.
Which of the following is not a portal of entry for pathogens? a. mucous membranes of the b. respiratory tract b. mucous membranes of the gastrointestinal tract c. skin d. blood e. parenteral route
d. blood
the table shows the ID 50 for Staphylococcus aureus in wounds with and without the administration of ampicillin before surgery. Based on the data, the administration of ampicillin before surgery 1) Staphylococcus aureus: Portal of entry = Wound; ID50 = <10 2) Staphylococcus aureus: Portal of entry = Wound + Ampicillin; ID50 = 300
decreases the risk of staphylococcal infection.
LAL assay
detection of minute amounts of endotoxin and quantification of endotoxins in drugs and on medical devices - quantitated by spectrophotometer
neurotoxin by Algae
dinoflagellates = saxitoxin = shellfish poisoning - domoic acid = STM loss = amnesic shellfish poisoning
exotoxins
proteins produced by both gram + and - bacteria - secreted by cell or released by lysis - growth and metabolism - highly specific = disease specific - by product of growing cell - NO fever and small LD50 - enzymes can act over and over so even small amounts are harmful - soluble in body fluids = rapidly transported throughout body - many are phage gene products - destroy particular parts of host cells or inhibit metabolic fxns ex: botulism = due to ingestion of exotoxin
invasins
proteins that rearrange nearby actin filaments oft he cytoskeleton - used of Salmonella and E.coli in small intestinal ET cells - cause actin of host's microfilaments to rearrange = form basket that carries bacteria into the cell ex: salmonella alter host actin to enter host cell = membrane ruffling
Toxins that stimulate proliferation of T cells nonspecifically and provoke intense immune responses are called __________.
superantigens -antigens that provoke a very intense immune response. - They are bacterial proteins. - Through a series of interactions with various cells of the immune system, superantigens nonspecifically stimulate the proliferation of T cells.
Virulence factors include
A.toxins B.enzymes C.capsules
Why is it difficult for antibodies to destroy HIV?
Abs are too large to contact the binding site on the surface of the virus.
Which of these substances are most important in the establishment of biofilms? A. Exotoxins B. Siderophores C. Invasins D. Adhesins E. Hemolysins
Adhesins - most important in the establishment of biofilms - A biofilm forms when microbes adhere to a particular surface that is typically moist and contains organic matter. The first microbes to attach are usually bacteria. Once they adhere to the surface, they multiply and secrete a glycocalyx that further attaches the bacteria to each other and to the surface.
Which types of organisms produce the toxin responsible for paralytic shellfish poisoning?
Algae - produce the toxin responsible for paralytic shellfish poisoning - Alexandrium, are important medically because they produce a neurotoxin called saxitoxin. - Although mollusks that feed on the dinoflagellates that produce saxitoxin show no symptoms of disease, people who eat the mollusks develop paralytic shellfish poisoning, with symptoms similar to botulism.
Which of these effects is most likely to occur if a pathogen enters the body by a portal of entry other than the preferred one? A. Pathogens cannot enter by alternate routes. B. A more severe disease will result. C. A milder disease will result. D. The exact same disease will result.
C. A milder disease will result
All of the following are used by bacteria to attach to host cells EXCEPT A. M protein. B. fimbriae. C. A-B toxins. D. ligands. E. capsules.
C. A-B toxins - most exotoxins - A part = active enzyme component - B part = binding component - tetanus toxin that cause uncontrollable muscle contraction
Which would be the most UNLIKELY location to find adhesin molecules on a newly discovered bacterium? A. Fimbriae B. Cell wall C. Ribosomes D. Capsule E. Glycocalyx
C. Ribosomes
__________ are molecules on bacterial cell surfaces that enable them to adhere to the surface of host cells. A. Coagulases B. Invasins C. Siderophores D. Adhesins
D. Adhesins
Which of the following are possible locations for bacterial adhesins? A. Fimbriae B. Pili C. Flagella D. All of the listed choices are possible locations for bacterial adhesins.
D. All of the listed choices are possible locations for bacterial adhesins.
Which of the following diseases CANNOT be prevented by toxoids? A. Tetanus B. Diphtheria C. Botulism D. Gram-negative septic shock
D. Gram-negative septic shock - Gram-negative bacteria cause endotoxic shock and toxoids are altered exotoxins.
Which of the following enzymes breaks down the "glue" that holds cells together?
Hyaluronidase - may be mixed with drug to promote the spread of drug through body tissue
Which of the following genera is the most infectious? 1) Genus: Legionella; ID50: 1 cell; Genus: Shigella; ID50: 200 cells 2) Genus: Salmonella; ID50: 10^5 cells; Genus: Treponema; ID50: 52 cells
Legionella
Endotoxins are also known as
Lipid A
Hepatitis B virus transmitted by a finger-stick device enters the host via which portal of entry?
Parenteral -microorganism gained access to the body when it was deposited directly into the tissues beneath the skin
Saxitoxin is produced by __________.
dinoflagellates
collagenase
produced by Clostridium that breaks down protein collagen = forms protein component of CT
Which of these organisms does NOT produce an enterotoxin? A. Clostridium botulinum B. Vibrio cholerae C. Shigella spp. D. Staphylococcus aureus
A. Clostridium botulinum - organism produces an exotoxin (botulinum toxin).
Which domain of the A-B toxin binds to cell surface receptors on the host cell?
B domain
What is the general term for observable changes in cells that occur as a result of viral infection?
Cytopathic effects (CPE) - used to diagnose viral infections - cytocidal effects = cell death - noncytocidal effects = cell damage but not cell death
The pathogenicity of which of the following is NOT the result of lysogeny? A. Clostridium botulinum B. Corynebacterium diphtheriae C. Vibrio cholerae D. Streptococcus pyogenes E. Clostridium tetani
E. Clostridium tetani - A plasmid may carry the information that determines a microbe's pathogenicity. - An example of a virulence factor that is encoded by plasmid genes is the tetanus neurotoxin.
Which of the following would be the first sign of an infection that resulted in the release of endotoxin?
Fever
What cell structures does Neisseria gonorrhoeae use to attach and enter host epithelial cells?
Fimbriae - Neisseria gonorrhoeae grows inside human epithelial cells and leukocytes = use fimbriae and an outer membrane protein called Opa to attach to host cells. - Following attachment by both Opa and fimbriae, the host cells take in the bacteria.
Why is surviving in phagocyte significant in penetrating host IS?
IS can't detect them if they are inside of the cell = multiply more; increases virulence as phagocyte is a place for pathogens to hide, grow and spread throughout the body
How does the protozoan Trypanosoma evade detection by the immune system?
It can change the surface antigens frequently, preventing the immune system from tracking it. Submit
Why is a release of endotoxin into the bloodstream potentially deadly?
It can lower blood pressure and cause the patient to go into shock.
hemolysins
Membrane-disrupting toxins that destroy erythrocytes (red blood cells), also by forming protein channels
What are leukocidins?
Molecules that are capable of destroying phagocytes
Meningitis and gonorrhea are caused by
Neisseria species.
Cancer patients undergoing chemotherapy are normally more susceptible to infections. However, a patient receiving an antitumor drug that affects eukaryotic cytoskeletons was resistant to Salmonella. Provide a possible mechanism for the resistance.
Salmonella affects host cells by disrupting the plasma membrane with invasins; it then uses the host's cytoskeleton to cause further damage in the cell; the drug could disrupt one of these processes, or it could simply inhibit the division of salmonella cells
Which bacterial proteins can take iron from human lactoferrin?
Siderophore - concentration of free iron in the human body is fairly low because most of the iron is tightly bound to iron-transport proteins, such as lactoferrin, transferrin, and ferritin, as well as hemoglobin. - As an alternative to iron acquisition by siderophores, some pathogens have receptors that bind directly to iron-transport proteins and hemoglobin. - Then these are taken into the bacterium directly along with the iron.
For what reason might the ID50 for Salmonella Typhi decrease when a rat simultaneously ingests sulfa drugs with the pathogen?
The antimicrobial interferes with the microbiome enabling the pathogen to more easily establish infection.
How does a capsule help certain bacteria evade detection by the immune system?
The capsule is composed of polysaccharides that are similar to those found in the host; thus, the immune system does not recognize it as foreign.
How are immune cells able to detect foreign pathogens?
They are able to detect structures on the surfaces of foreign cells that are not found in the host.
How do fibrinolysins enhance a pathogen's virulence?
They break down fibrin proteins that are involved in clot formation, allowing the cells to penetrate deep into damaged skin.
When would endotoxins be released from a bacterial cell?
When the cell dies
virulence
degree/extent of pathogenicity
superantigens
antigens that provoke the intense immune response = bacterial proteins - bind to macrophages -> activate T cells (lymphocytes that regulate IS activation) -> release cytokines (small protein molecule that regulate IS response and cell to cell communication) -> cytokine storm = increase amount of cytokine in blood stream = fever, nausea, vomit, diarrhea, shock and death
A pathogen that is capable of antigenic variation can ________________.
avoid host immune defenses - Some pathogens can alter their antigens so that by the time the body's immune system has developed a specific response, the antigens have already been altered and are no longer recognized by the responding antibodies and T cells.
A drug that binds to mannose on human cells would prevent a. the entrance of Vibrio enterotoxin. b. the attachment of pathogenic E. coli. c. the action of botulinum toxin. d. streptococcal pneumonia. e. the action of diphtheria toxin.
b. the attachment of pathogenic E. coli.
In some cases, viral infections may __________.
cause cells to lose contact inhibition - Viruses capable of causing cancer transform host cells. - Transformation results in an abnormal, spindle-shaped cell that does not recognize contact inhibition, meaning cells don't stop growing when they come in close contact with other cells. - The loss of contact inhibition results in unregulated cell growth.
Superantigens produce intense immune responses by stimulating lymphocytes to produce
cytokines
An exotoxin that has the ability to kill or damage host cells is referred to as a(n)
cytotoxin.
The release of endotoxins as bacteria are destroyed by phagocytes causes the phagocytes to release tumor necrosis factor (TNF). The life-threatening loss of blood pressure due to the action of TNF is called __________.
endotoxic shock - produced by endotoxins is related to the secretion of a cytokine by macrophages - TNF secreted by phagocytosis of gram negative bacteria
Most pathogens that gain access through the skin
enter through hair follicles and sweat ducts.
kinase
enzyme that break down fibrin and digest clots formed by body to isolate the infection ex: streptokinase = break down blood clots that cause heart attacks
Some organisms are capable of orchestrating alterations that are collectively termed antigenic variation. This allows an organism to __________.
evade the host's immune system - Some pathogens can alter their surface antigens, by a process called antigenic variation. - Thus, by the time the body mounts an immune response against a pathogen, the pathogen has already altered its antigens and is unaffected by the antibodies.
Lysogenic bacteriophages contribute to bacterial virulence because bacteriophages
give new gene sequences to the host bacteria. Submit
Antibiotics can lead to septic shock if used to treat
gram-negative bacterial infections.
Septic shock can result from using antibiotics to treat
gram-negative bacterial infections.
The best description of direct damage by a pathogen is
host cells destroyed when pathogens metabolize and multiply -> cells lyse -> pathogens spread - pathogens extruded from host cell by exocytosis -> enter other host cells
Which of the following virulence factors is specifically involved in helping an organism to physically spread throughout the body?
hyaluronidase - involved in helping an organism to physically spread throughout the body - hydrolyzes hyaluronic acid, a type of polysaccharide that holds together certain cells of the body, particularly cells in connective tissue - digesting action is thought to be involved in the tissue blackening of infected wounds and to help the microorganism spread from its initial site of infection - produced by some clostridia that cause gas gangrene
portals of entry: skin
impenetrable for most microbes - enter through hair follicles and sweat gland ducts = opening of the skin
Helminths disease symptoms
interferes with host function = cellular damage ex: waste product of roundworm (metabolic waste) = cause symptoms
Siderophores are bacterial proteins that compete with the host's
iron-transport proteins. Submit
membrane disrupting toxins (2)
lyse host's cells by: 1) making protein channels into PM or disrupting phospholipid portion = kill phagocytes with leukocidins = decrease host resistance 2) hemolysins = cause RBCs lysis = frees iron from hemoglobin = secrete siderophores
Protozoa disease symptoms
malaria - invade host cells and reproduce within = Plasmodium - avoid host defense by growing in phagocytes and antigenic variation ex: trypanosoma
The symptoms of protozoan diseases are usually due to __________.
metabolic waste products
portals of entry: parenteral route
microbes deposited directly into tissue beneath skin or into mucous membrane when barriers are penetrated or injured ex: punctures, wounds due to swelling/drying
The most frequently used portal of entry for pathogens is the
mucous membranes of the respiratory tract.
Polio is transmitted by ingestion of water contaminated with feces containing polio virus. What portal of entry does polio virus use?
mucous membranes only
A patient who has been hospitalized with uncontrolled muscle spasms has probably been infected with bacteria that secrete a(n)
neurotoxin
If a patient has a deep tissue infection as the result of an animal bite on the arm, the portal of entry is described as the __________.
parenteral route
endotoxins
part of outer portion of cell wall of gram negative bacteria - Lipid A part released (LPS) - symptoms due to vigorous inflammation - large LD 50; bacterial cell death, ABxs and antibodies release endotoxins - produce fever and shock = phagocytes secrete TNF alpha after engulf gram - = increase permeability of blood capillaries = decrease blood volume and decrease BP = tissue hypoxia - TNF = weaken BBB = bacteria enter = infect CNS - heat stable = not readily inactivated by increase temp
Endotoxins are
part of the gram-negative cell wall.
An encapsulated bacterium can be virulent because the capsule
resists phagocytosis.
Endotoxins in sterile injectable drugs could cause
septic shock symptoms.
plasmids
small, circular DNA not connected to main bacterial chromosome and capable of independent replication - carry info that determines microbes pathogenicity ex: R factors = resistance of ABx
Bacteria that cause periodontal disease have adhesins for receptors on streptococci that colonize on teeth. This indicates that
streptococcal colonization is necessary for periodontal disease.
A person who attended a picnic early in the day develops a very high fever and is unresponsive by the evening. This person most likely has been exposed to a(n)
superantigen.
Symptoms of intense inflammation and shock occur in some gram-positive bacterial infections due to
superantigens
Measles viruses are capable of inactivating host defenses by
suppressing the immune system.
Injectable drugs are tested for endotoxins by
the Limulus amoebocyte lysate test.
The ID50 is
the dose that will cause an infection in 50 percent of the test population. ex: Bacillus anthracis = 3 portals of entry 1) skin 2) inhalation 3) gastrointestinal
Symptoms of protozoan and helminthic diseases are due to
tissue damage due to growth of the parasite on the tissues, waste products excreted by the parasite, and products released from damaged tissues.
Cytopathic effects are changes in host cells due to
viral infections.
Certain traits that allow pathogens to create infection and cause disease are termed
virulence factors.
