Ch. 15 Microbiology

Mucous membranes (portal of entry)

-Bacteria and viruses gain access to the body by penetrating mucous membranes lining respiratory tract, GI tract, genitourinary tract, and conjunctiva. Respiratory tract; inhaled into the nose or mouth in drops of moisture and dust particles. GI tract; Food and water via contaminated fingers. Genitourinary tract; sexually.

A-B toxins

-Part A is the active enzyme component. -Part B is the binding component. Ex: Diphtheria toxin.

Endotoxins

-Part of bacterial cells, and not a metabolic product. -Part of the outer portion of the cell wall of gram - bacteria. -These are lipids. -Released during multiplication and when gram - bacteria die and cell walls undergo lysis. -Signs and symptoms are chills, fever, weakness, generalized aches, shock, and even death.

Exotoxins

-Produced inside some bacteria (mostly gram -) as part of their growth and metabolism and are secreted by the bacterium into the surrounding medium or released following lysis. -Are proteins, and many are enzymes that catalyze only certain biochemical reactions. -Small amounts are harmful. -Can diffuse into the blood and rapidly transported throughout the body. -Among the most lethal substances known.

Fungi

-Some have metabolic products that are toxic to human hosts. -Chronic fungal infections can provoke an allergic response. -Trichothecenes are fungal toxins that inhibit protein synthesis in eukaryotic cells.

Which of the following virulence factors is specifically involved in helping an organism to physically spread throughout the body? A) hyaluronidase B) endotoxins C) siderophores D) hemolysin

A

Mycotoxins

A few mushrooms produce fungal toxins called ______ -Ex: phalloidin and amanitin

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) Stomach acid increases the virulence of Vibrio cholerae. B) Stomach acid decreases the virulence of Vibrio cholerae. C) Sodium bicarbonate decreases the virulence of Vibrio cholerae. D) Sodium bicarbonate inactivates Vibrio cholerae. E) Vibrio cholerae makes toxins only in the presence of stomach acid.

B

Which of the following organisms does NOT enter through the gastrointestinal tract? A) Hepatitis A virus B) Rubella virus C) Trichinella spiralis D) Vibrio cholera

B

Which of the following statements is NOT true of A-B exotoxins? A) Many exotoxins are A-B toxins. B) They are produced only by gram-negative bacteria. C) The B portion of the toxin binds to surface receptors on host cells. D) The A portion of the toxin is the active component. E) They consist of two polypeptide components.

B

Which of these eukaryotic molecules/structures can be responsible for movement of bacteria within host cells? A) Invasins B) Actin molecules C) Cilia D) Pseudopods E) Flagella

B

Which of these is a cell wall component that contributes to invasiveness? A) Coagulase B) M protein C) Endotoxin D) Hemolysin

B

Which of these statements is true regarding portals of exit? A) The portal of exit for tuberculosis is the skin. 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) Polioviruses most often use the respiratory portal of exit.

B

Which of these substances does NOT protect a bacterium from phagocytosis? A) Capsule B) Siderophore C) M protein D) Leukocidin

B

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) Gram-positive bacteria are growing in the sample. B) Endotoxin is present. C) Gram-negative bacteria are growing. D) The fluid is not sterile.

B

Which of these viral cytopathic effects is most likely to be associated with the development of cancer? A) cell death B) stimulation of interferon production C) loss of contact inhibition D) inclusion bodies E) cell fusion

C

Which statement is true of endotoxins? A) They are disease specific. B) They are proteins. C) They are released upon cell lysis. D) They are produced by gram-positive bacteria. E) They increase blood pressure.

C

Which one of these bacterial proteins can take iron from human lactoferrin? A) Protease B) Hyaluronidase C) Kinase D) Siderophore

D

Which one of these is NOT an example of pathogen entry via the parenteral route? A) Injection of the pathogen via a contaminated needle B) Injection via the bite of an infected insect C) Entry through a break in the skin caused by a cut D) Infection of a hair follicle

D

The parental route (portal of entry)

Deposited directly into the tissues beneath the skin or into mucous membranes. Punctures, injections, bites, cuts, wounds, surgery, and splitting of the skin or mucous membrane due to swelling or drying.

The pathogenicity of which of the following is NOT the result of lysogeny? A) Vibrio cholerae B) Clostridium botulinum C) Streptococcus pyogenes D) Corynebacterium diphtheriae E) Clostridium tetani

E

Which of these events leads to all of the others in a pyrogenic (fever) response? A) IL-1 travels via the blood to the hypothalamus. B) IL-1 is released by macrophages. C) The body's thermostat is set to a higher level, and fever occurs. D) The hypothalamus releases prostaglandins. E) Endotoxin is released from the cell wall of gram-negative bacteria.

E

Which of these statements is NOT true for bacterial capsules? A) The importance of the capsule to virulence for Streptococcus pneumoniae can be determined because there are strains both with and without the capsule. B) Capsules related to virulence are produced by the causative agents of anthrax and bubonic plague. C) For Streptococcus pneumoniae, the encapsulated strain is more virulent. D) Pathogenic and nonpathogenic bacteria can produce capsules. E) Immune system antibodies are not produced against a capsule.

E

Which of these substances are most important in the establishment of biofilms? A) Invasins B) Hemolysins C) Exotoxins D) Siderophores E) Adhesins

E

Which one of these pairs is NOT correctly matched? A) siderophore; traps iron B) IgA protease; digest antibodies C) leukocidin; lyses WBC membranes D) collagenase; breaks down connective tissue E) coagulase; lyses fibrin clots

E

Which statement is NOT true of endotoxins? A) They are more heat-resistant than exotoxins are. B) They can lyse amebocytes found in crab hemolymph. C) Endotoxins are produced by Neisseria meningitidis and E. coli. D) They can induce chills, fever, aches, clotting, shock, and miscarriage. E) They are eliminated from the body as a result of antitoxin production.

E

Aflatoxin

Has carcinogenic properties. Produced by the growth of the mold Aspergillus flavus.

Gas gangrene and food poisoning

Membrane-disrupting exotoxin. One exotoxin (cytotoxin) causes massive RBC destruction (hemolysis); another exotoxin (enterotoxin) is related to food poisoning and causes diarrhea.

Skin and soft tissue infection

Membrane-disrupting exotoxin. The panton-valentine leukocidin found in the community-acquired strain of MRSA makes pores in WBC membranes.

Leukocidins

Membrane-disrupting toxins that kill phagocytic leukocytes (white blood cells). Form protein channels. Active against macrophages, phagocytes present in tissues. Staphylococci and streptococci

The symptoms of protozoan diseases are usually due to __________.

Metabolic waste products

Biofilms

Microbes can come together in masses, cling to surfaces, and take in and share available nutrients in communities. Dental plaque on teeth, algae on walls of swimming pools, scum on shower doors. Play a role in evading phagocytes.

Invasins

Microbes produce surface proteins that rearrange nearby actin filaments of the cytoskeleton. Membrane ruffling is the result of disruption in the cytoskeleton of the host cell. Shigella and Listeria can use actin to propel themselves through the host cell cytoplasm and from one host cell to another.

Antigenic variation

Pathogens can alter their surface antigens.

Portals of entry

Pathogens gain entrance to the human body and other hosts through several avenues.

Adherence or adhesion

Pathogens means of attaching themselves to host tissues at their portal of entry.

Toxins

Poisonous substances that are produced by certain microorganisms.

Helminths

Presence of these often produces disease symptoms in a host. Use host tissue for their own growth or produce large parasitic masses; resulting cellular damage evokes the symptoms.

Protozoa

Presence of this and their waste products often produce disease symptoms in the host. Parasite prevents normal acidification and digestion; it can grow in the phagocytic vacuole. Antigenic variation.

Collagenase

Produced by several species of Clostridium, facilitates the spread of gas gangrene. Breaks down the protein collagen.

What bacteria impair phagocytosis?

Streptococcus pneumoniae, Haemophilus influenzae, Bacillus anthracis, Yersinia pestis.

Food poisoning

Superantigen exotoxin. Enterotoxin causes secretion of fluids and electrolytes that results in diarrhea.

Toxic shock syndrome

Superantigen exotoxin. Toxin causes secretion of fluids and electrolytes from capillaries that decreases blood volume and lowers blood pressure.

Toxins that stimulate proliferation of T cells nonspecifically and provoke intense immune responses are called __________.

Superantigens

Pathogenicity

Ability to cause disease by overcoming host defenses.

__________ are molecules on bacterial cell surfaces that enable them to adhere to the surface of host cells.

Adhesins

Which types of organisms produce the toxin responsible for paralytic shellfish poisoning?

Algae

Toxoids

Altered exotoxins. Exotoxins are inactivated by heat or by formaldehyde, iodine, or other chemicals, they no longer cause disease. Can be injected in the body as a vaccine.

Opa

An outer membrane protein to attach to host cells.

IgA proteases

Body produces a class of antibodies called IgA antibodies. Pathogens that have the ability to produce enzymes and can destroy these antibodies.

Antitoxins

Body produces these antibodies. They provide immunity to exotoxins.

Based on the following ID50 values, which microbe is the most virulent? Assume each bacterium enters through the appropriate portal of entry. A) Cryptosporidium: 50 cells B) E. col O157: 1000 cells C) Shigella: 10 cells D) Vibrio cholerae: 108 cells

C

Which of the following are possible locations for bacterial adhesins? A) Flagella B) Fimbriae C) All of the listed choices are possible locations for bacterial adhesins. D) Pili

C

Which of the following organisms is NOT discharged through the respiratory tract? A) Measles virus B) Histoplasma capsulatum C) Poliovirus D) Bordetella pertussis

C

Which of the following toxins is NOT produced by a bacterium as a result of lysogenic conversion? A) Botulinum neurotoxin B) Diphtheria toxin C) Endotoxin D) Staphylococcal enterotoxin

C

Which of these conditions would NOT affect the ability of Streptococcus mutans to attach to teeth? A) The inability to form dextran B) The lack of the enzyme glucosyltransferase C) The absence of Actinomyces, a bacterium that can be part of dental plaque D) The lack of a glycocalyx E) The lack of sucrose

C

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) A more severe disease will result. B) The exact same disease will result. C) A milder disease will result. D) Pathogens cannot enter by alternate routes.

C

Which of these statements about toxoids is INCORRECT? A) Diphtheria and tetanus can be prevented by toxoid vaccinations. B) Toxoids stimulate the body to produce antitoxins without causing disease. C) Gram-negative septic shock is commonly prevented by toxoids. D) Exotoxins can be altered by heat or chemicals to form toxoids.

C

Which one of these substances would NOT be produced at the same time as coagulase? A) Capsules B) Hemolysin C) Fimbriae D) Fibrniolysin

D

Streptolysins

Hemolysins produced by streptococci. Can cause lysis of red blood cells and white blood cells and other body cells.

Lysogenic conversion

Host bacterial cell and its progeny may exhibit new properties encoded by the bacteriophage DNA. Change in characteristic of microbe due to a prophage. Bacterial cell is immune to infection by the same type of phage.

Lipid A

Lipid portion of LPS (lipopolysaccharides) is the endotoxin.

Waxy lipid

Makes up the cell wall of M. tuberculosis increases virulence by resisting digestion by phagocytes, and bacteria can multiply inside phagocytes.

Hepatitis B virus transmitted by a finger-stick device enters the host via which portal of entry?

Parenteral

Ergot

Toxin itself, is an alkaloid that can cause hallucinations resembling those produced by LSD. A natural source of LSD. Constricts capillaries and can cause gangrene of limbs.

Saxitoxin is produced by __________.

dinoflagellates

Which of these organisms does NOT produce an enterotoxin? A) Clostridium botulinum B) Shigella spp. C) Staphylococcus aureus D) Vibrio cholerae

A

What are the cytopathic effects a virus can produce?

1. Macromolecular synthesis within host cell stops. 2. Host cell lysosomes made to release enzymes, resulting in destruction of intracellular contents and host cell death. 3. Inclusion bodies found in cytoplasm or nucleus of some infected cells. Arise at sites of earlier viral synthesis but don't contain assembled viruses or their components. Can help identify causative agent. 4. Several adjacent infected cells fuse to form very large multinucleate cells called a syncytium. 5. Result in changes in the host cell's functions with no visible changes in the infected cells. 6. Induce antigenic changes on the surface of the infected cells. Result of viral-gene encoded proteins. 7. Induce chromosomal changes in host cell. 8. Viruses capable of causing cancer transform host cells. Results in an abnormal, spindle shaped cell that does not recognize contact inhibition, cells don't stop growing when they come in close contact with other cells.

Capsules play a role in the virulence of all of the following EXCEPT __________. A) Mycobacterium tuberculosis B) Yersinia pestis C) Klebsiella pneumoniae D) Bacillus anthracis E) Haemophilus influenzae

A

Given the following LD50 values for Bacillus anthracis, through which portal of entry is it easiest to get anthrax? A) Cutaneous: 50 endospores B) Ingestion: 1 million endospores C) All of the listed choices are equally easy portals of entry. D) Inhalation: 20,000 endospores

A

Which of the following is an accurate statement about A-B toxins? A) They are proteins. B) The A and B components must remain attached in order to exert their effects on the cell. C) The A component binds to a receptor on the host cell. D) They are a type of endotoxin.

A

M protein

A heat-resistant and acid-resistant protein. Found on both the cell surface and fimbriae. Mediates attachment of the bacterium to epithelial cells of host and helps bacterium resist phagocytosis by white blood cells. Increases virulence of microorganism. S. pyogenes, N. gonorrhoeae.

Limulus amebocyte lysate assay

A laboratory test, which can detect even minute amounts of endotoxin. Resulting gel-clot (precipitate) is a positive test for presence of endotoxin.

Diphtheria

A-B exotoxin. Cytotoxin inhibits protein synthesis, especially in nerve, heart, and kidney cells.

Cholera

A-B exotoxin. Enterotoxin causes secretion of large amounts of fluids and electrolytes that result in diarrhea.

Traveler's diarrhea

A-B exotoxin. Enterotoxin causes secretion of large amounts of fluids and electrolytes that result in diarrhea.

Scalded skin syndrome

A-B exotoxin. Exotoxin causes skin layers to separate and slough off.

Tetanus

A-B exotoxin. Neurotoxin blocks nerve impulses to muscle relaxation pathway; results in uncontrollable muscle contractions.

Botulism

A-B exotoxin. Neurotoxin prevents transmission of nerve impulses; flaccid paralysis results.

Anthrax

A-B exotoxin. Two A components enter the cell via the same B. The A proteins cause. shock and reduce the immune response.

Gastric cancer

A-B toxin. Genotoxin causes breaks in DNA.

Superantigens

Antigens that provoke a very intense immune response. Bacterial proteins that combine with a protein on macrophages; stimulates the proliferation of immune cells called T cells. T cells are stimulated to release enormous amounts of chemicals called cytokines, small protein molecules produced by various body cells, that regulate immune responses and mediate cell-to-cell communication. Causes fever, nausea, vomiting, diarrhea, and sometimes shock and even death.

Adhesins or ligands

Attachment between pathogen and host is accomplished by means of surface molecules on the pathogen. Bind specifically to complementary surface receptors on the cells of certain host tissues. May be located on a microbe's glycocalyx or on other microbial surface structures, such as pili, fimbriae, and flagella.

Which of the following cell wall components do/does NOT contribute to virulence? A) Opa B) All of the listed choices contribute to virulence. C) mycolic acids D) fimbriae E) M protein

B

Kinases

Bacterial enzymes that break down fibrin and digest clots formed by the body to isolate the infection.

Coagulases

Bacterial enzymes that coagulate (clot) the fibrinogen in blood. Produced by some members of the genus Staphylococcus; may be involved in the walling-off process in boils produced by staphylococci.

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 __________.

Biofilms

Genotoxins

Cause breaks in eukaryotic DNA. Causes mutations, disrupts cell division, and may lead to cancer.

In some cases, viral infections may __________.

Cause cells to lose contact inhibition

Membrane-disrupting toxins

Cause lysis of host cells by disrupting their plasma membranes. Form protein channels in the plasma membrane; others disrupt the phospholipid portion of the membrane. -Ex: S. aureus (protein channels), C. perfringens (disrupts the phospholipids)

Intoxications

Caused by the presence of a toxin; not by microbial growth.

What is the general term for observable changes in cells that occur as a result of viral infection?

Cytopathic effects

Which disease is correctly matched with the common portal of entry? A) Influenza; mucous membranes of genitourinary tract B) Hookworm; mucous membranes of genitourinary tract C) Measles; parenteral route D) Poliomyelitis; mucous membranes of gastrointestinal tract E) Chlamydia; skin

D

Which of the following diseases CANNOT be prevented by toxoids? A) Botulism B) Tetanus C) Diphtheria D) Gram-negative septic shock

D

Direct damage

Disrupts host cell function. Uses host cell nutrients. Produce waste products. Multiplies in host cells and causes it to rupture.

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

Hyaluronidase

Enzyme secreted by certain bacteria, such as streptococci. Hydrolyzes hyaluronic acid, a polysaccharide that holds together certain cells of the body. Produced by some clostridia that cause gas gangrene.

Respiratory tract (portal of exit)

Exit in discharges from mouth and nose, during coughing or sneezing. Found in droplets formed from mucus.

GI tract (portal of exit)

Exit in feces or saliva. Feces can be contaminated with salmonellosis, cholera, typhoid fever, shigellosis, amebic dysentery, and poliomyelitis. Saliva can contain pathogens such as rabies, mumps, and infectious mononucleosis.

What cell structures does Neisseria gonorrhoeae use to attach and enter host epithelial cells?

Fimbriae

Skin (portal of entry)

Gain access to the body through openings in the skin, such as hair follicles and sweat gland ducts.

Skin or wound infections (portal of exit)

Infections transmitted from the skin include yaws, impetigo, ringworm, simplexvirus, and warts. Drainage from wounds can spread infections to another person directly or by contact with a contaminated fomite. Infected blood can be removed ad reinjected by biting insects and contaminated needles and syringes to spread infection within a population. Diseases include yellow fever, plague, tularemia, and malaria. AIDS and hepatitis B transmitted by needles and syringes.

Siderophores

Iron is required for the growth of most pathogenic bacteria. Some pathogens secrete these proteins.

Antibiotic-associated diarrhea

Membrane-disrupting exotoxin. Enterotoxin causes secretion of fluids and electrolytes that results in diarrhea; cytotoxin disrupts host cytoskeleton.

Hemolysins

Membrane-disrupting toxins that destroy erythrocytes (red blood cells), by forming protein channels. Staphylococci and streptococci.

Capsules

Resists the host's defenses by impairing phagocytosis, process by which certain cells of the body engulf and destroy microbes. Chemical nature appears to prevent the phagocytic cell from adhering to the bacterium. Glycocalyx around cell wall.

Which would be the most UNLIKELY location to find adhesin molecules on a newly discovered bacterium?

Ribosomes

Portals of exit

Secretion, excretions, discharges, or tissue that has been shed. Let pathogens spread through a population by moving from one susceptible host to another. Most common are respiratory tract and GI tract.

Genitourinary tract (portal of exit)

Sexually transmitted infections are found in secretions from the penis and vagina. Urine can contain pathogens responsible for typhoid fever and brucellosis, can exit via the urinary tract.

Algae

Some of these produce neurotoxins. Saxitoxin. Paralytic shellfish poisoning.

Interferons

Some virus-infected host cells produce substances called alpha and beta _____. Alpha and beta _____ protect neighboring uninfected cells from viral infection in two ways: inhibit synthesis of viral proteins and host cell proteins; kill virus-infected host cells by apoptosis.

Toxigenicity

The capacity of microorganisms to produce toxins.

Virulence

The degree of pathogenicity.

LD50

The potency of a toxin. Lethal dose for 50% of a sample population.

Toxemia

The presence of toxins in the blood.

ID50

The virulence of a microbe. Infectious dose for 50% of a sample population. The 50 is used to compare relative virulence under experimental conditions.

Cytopathic effects

The visible effects of viral infection. Cell death are cytocidal effects. Cell damage but not cell death are noncytocidal effects. Used to diagnose many viral infections.

__________ are toxins modified to retain their ability to induce antibody formation but lose their toxicity.

Toxoids

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 __________.

cutaneous anthrax is easier to acquire than inhalation anthrax

Some organisms are capable of orchestrating alterations that are collectively termed antigenic variation. This allows an organism to __________.

evade the host's immune system

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