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BIOL 455 Lecture Exam 3

Terms in this set (206)

What are viruses?
An infectious particle consisting of a nucleic acid and a protein coat. They are obligate intracellular parasites.
What can viruses infect?
Bacteria, fungi, plants, protists, and animals.
What is a host range?
The number of species and cell types that a virus is capable of infecting
What two things do viruses have in common with bacteria?
Organization & evolution
What three things do viruses lack that bacteria have?
Homeostasis, growth, and response to stimuli
A complete virus particle is called a ________ and consists of what?
virion, genome & capsid (and sometimes an envelope with spike proteins)
What are the two components of a nucleocapsid?
A capsid and nucleic acid
What is the name for a subunit of a capsomere?
Capsid
True or false: All viruses have envelopes
False
Viral spike proteins are _____________ that embed in the viral _______________
Glycoproteins, envelope
The + sense strand of DNA is the same sequence as ________
mRNA
The - sense strand of DNA is complementary to ________
mRNA
True or false: Viral genomes vary greatly and can have circular or linear , single or double strand, and segmented or non-segmented genetic material
True
What five steps in viral multiplication are common to all viruses?
1) Attachment
2) Entry
3) Biosynthesis
4) Maturation
5) Release
True or false: All viruses have a latent or lysogenic (bacteriophage) cycle in which they are present but not producing new viruses
False
What are bacteriophages?
Viruses that infect bacteria
What are the five steps in the lysogenic cycle?
1) Phage attaches to cell
2) Viral genome enters cell
3) Viral DNA is integrated into host genome
4) Hist cell replicates into chromosomes, creates new copy of phage DNA so both cells will contain phage DNA upon division
5) Phase DNA can be cut out of the bacterial genome and start making new phages, initiating the lytic cycle
What is a prophage?
Host genome with integrated viral DNA
What are the six steps in animal and plant virus multiplication?
1) Attachment - virus binds to receptor on cells
2) Entry - virus or nucleocapsid enters (endocytosis or fusion)
3) Uncoating - virus dissassembles
4) Biosynthesis - parts of virus are made, genome replicated
5) Maturation - virus assembled
6) Release - virus is released by lysing cell (non enveloped)l budding, or exocytosis
What are the five detailed steps of the lytic cycle (bacteriophages)?
1) Attachment - bacteriophage to bacterial cell
2) Entry - viral genome enters cell
3) Biosynthesis - parts of the phage are made
4) Maturation - phages are assembled
5) Release - phages are released into environment, cell is lysed
When viruses infecting plants or animals can have a latent phase and integrate into the host genome, they are called _____________
proviruses
How are viruses classified?
Baltimore classification: Realm, kingdom, phylum, class, order, family, genus, species
Viral genomes can either be ds, meaning ______________, or ss, meaning ______________
double stranded, single stranded
What does DdDP stand for? What does it do?
DNA-dependent DNA polymerase: makes DNA from DNA
What does DdRP stand for? What does it do?
DNA-dependent DNA polymerase: Makes RNA from DNA
What does RdRp stand for? What does it do?
RNA-dependent RNA polymerase: Makes RNA from RNA
What does RT stand for? What does it do?
Reverse transcriptase: Makes DNA from RNA
Baltimore group I are ___________ viruses
dsDNA
Adenoviruses, herpes viruses, and small pox are all examples of Baltimore group ____
I
Baltimore group II are ______ viruses
ssDNA
Parvoviruses and circoviruses are examples of Baltimore group _____
II
Baltimore group III are __________ viruses
dsRNA
Reoviruses (like bluetongue virus and rotavirus) are examples of Baltimore group _____
III
Baltimore group IV are _________ viruses
(+) ssRNA
Togaviruses, coronaviruses, and picoviruses are all part of Baltimore group _____
IV
Baltimore group V are __________ viruses
(-) ssRNA
Orthomyxoviruses (like influenza) and Rhaboviruses (like rabies) are part of Baltimore group ____
V
What is sepsis?
Microbial contamination. Medical definition: The harmful immune response to an infection, especially, but not limited to, a bacteria.
What is aspepsis?
The absence of significant contamination
What do aseptic techniques do?
Prevent microbial contamination
What do biocides (germidices) do?
Treatments that kill microbes
What is bacteriostasis?
Inhibiting, not killing, microbes
What is bacteriocide?
Killing microbes
How many biosafety levels are there? Which is used for the most dangerous and exotic pathogens?
4, BSL-4
BSL-4 utilizes _________ pressure in a "hot zone"
negative
What is sterilization?
Destroying all microbial life
What is disinfection?
Destroying harmful microbes on inanimate objects
What is antisepsis?
Destroying harmful microorganisms on living tissue
What is degerming?
Mechanical removal of microbes from a limited area
In food microbiology, what is commercial sterilization?
Killing C. botulinum endospores from canned goods
In food microbiology, what is sterilization?
Lowering microbial counts on eating utensil to safe levels
During treatment, microbes die at a ___________ rate.
Linear
What can affect the effectiveness of a treatment?
Type of microbe, number of microbes, environment, composition of item, time of exposure
What is required to kill endospore-forming bacteria (Bacillus spp. & Clostridium spp.)
Extreme heat or strong disinfectant
What is required to destroy Mycobacterium spp. cell walls?
Strong disinfectants
What bacteria often grows in disinfectants and responsible for many nosocomial (hospital-acquired) infections?
Pseudomonas spp.
True or false: Non-enveloped viruses (polio, norovirus, etc) are highly resistant to killing
True
What is required to kill Protozoan cysts & oocysts (Giardia & Cryptosporidium spp.)
Boiling
What are three ways control agent kill or inhibit microbial growth?
1) Alternation of membrane permeability
2) Damage/denature proteins (enzymes)
3) Damage to nucleic acids
What are the two major methods of microbial control?
Physical & chemical
Heat, filtration, pressure, desiccation, and osmotic pressure are all examples of _______________
physical disinfection
What is thermal death point (TDP)?
The lowest temperature for all bacteria in a liquid culture to be killed in 10 minutes
What is thermal death time (TDT)?
The lowest time for all bacteria in a liquid culture to be killed at a particular temperature.
What is decimal reduction time (DRT or D-value)?
The minutes it takes to kill 90% of a population at a given temperature. Calculated using the TDP and TDT
How does an autoclave work?
Uses pressurized steam to sterilize. 121 C at 15 psi for 15 minutes. Kills all microbes and endospores, but steam must contact item's surface.
How do retorts work?
They CAN commercially sterilize using steam (similar to an autoclave), but usually don't.
Large containers require ____________ sterilization times
longer
Endospores from what genus are used to calibrate machines utilizing moisture heat sterilization?
Bacillus spp.
What does HTST pasteurization do?
Reduces spoilage microbes and pathogens to extend shelf-life. DOES NOT STERILIZE.
What kind of pasteurization is mostly commonly used for dairy products?
High-temperature, short-time (HTST) at 72 C for 15 sec
UHT pasteurization (at 140 C for 4 sec) ___________ milk, allowing for room temperature storage
sterilizes
Flaming, incineration and cooking are all examples of what kind of sterilization? How does it kill microbes?
Dry heat sterilization, kills by oxidation
_________ temperature has a bacteriostatic effect
Low
What is pascalization? What is it used for?
High pressure that destroys microbe cells and denatures proteins without heat
What is desiccation? What does it do?
The absence of water, which prevents metabolism
What is osmotic pressure? What does it do?
Uses salts and/or sugars to create a hypertonic environment, which results in plasmolysis
X rays, gamma rays, and electron beams are all examples of _________________.
ionizing radiation
How does ionizing radiation kill microbes?
Ionizes water to create hydroxyl radicals (ROS), which damage DNA
UV rays are an example of ________________ radiation
non-ionizing
How does non-ionizing radiation affect microbes?
Damages DNA by creating thymine dimers that inhibit DNA replication
How do microwaves damage microbes?
Kill by heat, not especially antimicrobial
What are HEPA filters?
High-efficiency particulate air filters that remove microbes greater than 0.3 micrometers from air in clean rooms
What do membrane liquid filters do?
Remove microbes greater than 0.22 micrometers from liquids (0.2 micrometer filters are the gold standard)
What four factors affect disinfection?
Concentration of disinfectant, time, organic matter, pH
What is the use-dilution test?
A standard test by the American Association of Analytical Chemists. Metal cyclinders are dipped in test bacteria, dried, and placed in disinfectant before being transferred to culture media to determine if bacteria survived
What is a disk diffusion test?
Evaluates efficacy of chemical agents by applying soaked filters to culture containing pre-inoculated agar.
What are in-use tests used for?
To validate the effectiveness of disinfectant solution already in use and evaluates microbial contamination of cleaning solutions.
True or false: Soaps are effective against endospores
False
Soaps & detergents, acid-anionic sanitizers, cationic detergents, and quats are examples of _______________-
Surfactants
How are soaps & detergents chemically used to affect microbes?
Skin degerming; Sanitation by
mechanical removal by scrubbing
How are acid-anionic sanitizers used to chemically affect microbes?
Dairy & food-processing; plasma
membrane denaturing in most
bacteria
How are cationic detergents and quaternary ammonium compounds & quaternary ammonium compounds used to affect microbes?
Strong skin & surface sanitizer;
disrupt plasma membrane
When given the choice, should one use an air-dryer or clean paper towel to dry hands after washing?
Paper towel - the friction is essential for hand washing
How do alcohols affect bacteria, fungi, and enveloped viruses?
Kill by denaturing proteins and dissolving phospholipids
How do alcohols affect endospores non-enveloped viruses?
No effect
How do peroxygens affect microbes?
Kills bacteria, viruses, fungi, and endospores on inanimate objects.
Should hydrogen peroxides be used on wounds?
No, human skin cells contain catalase to break down the peroxide to water.
How does plasma, a form of electrically excited peroxygen gas, affect microbes?
Kills bacteria, viruses, fungi, and endospores at relatively low temperatures. Increasingly used for medical devices (biofilms!)
How do heavy metals affect microbes? What heavy metal is used to prevent ophthalmia neonatorum?
Denature proteins. Silver nitrate.
Iodine, a halogen, is one of the older disinfectants. How does it work?
Oxidizing agent that damages sulfur-containing amino acids, nucleotides, and fatty acids.
What is a tincture?
An iodine solution in aqueous alcohol.
What is an iodophor?
Iodine combined with organic molecules.
Chlorine gas & hypochlorites (halogens) affect microbes how?
They react with water to form hypochlorous acid, a strong oxidizing agent that damages sulfur-containing amino acids, nucleotides, and fatty acids.
How do phenolics & bisphenols affect microbes?
Damage phospholipids of plasma
membranes, causing leakage. Disinfectant residue is left behind.
How do bisguanides affect microbes? Against what are they effective?
Damage phospholipids of plasma membranes. Effective against Gram-positive bacteria, yeast, enveloped viruses and some Gram-negative bacteria.
Chlorohexidine is an example of a ______________ and is used in surgical hand scrubs.
bisguanide
How do aldehydes/alkylating agents affect microbes?
Inactivate proteins by cross-linking with some amino acid functional
groups. Kill bacteria, viruses, fungi, and endospores.
Formaldehyde and glutaraldehyde are examples of _____________
aldehydes
Chemical sterilization uses sterilants to cause alkylation. What is alkylation?
Replacing hydrogen atoms with a free radical
Nitrates & nitrites prevent _____________ germination in processed meats
endospore
What preservative prevents wine spoilage?
Sulfur dioxide
Who developed the concept of selective toxicity by identifying dyes that treated African sleeping sickness?
Paul Ehrlich
Who discovered arsenic compounds could treat syphilis?
Sahachiro Hato
Who truly discovered penicillin? Who is credited for the discovery?
Ernest Duchesne, Alexander Fleming
What are antimicrobials?
Agents selective for bacteria, viruses, fungi,
protozoa, helminths
What are the 5 kinds of antimicrobials?
Antibiotics (bacteria only), antivirals, antifungals, antiprotozoans, antiheminthics
What do bacteriostatic antibiotics do?
prevent growth
- Cannot kill bacteria
- Immune system removes
bacteria
What do bactericidal antibiotics kill?
Many only affect growing
bacteria
• Inhibitors of cell wall
synthesis only effective if
organism is building new cell
wall (log growth)
• Must take antibiotic until all
cells leave stationary phase
What is the best broad-spectrum antibiotics?
Tetracycline
What is a superinfection?
overgrowth of second pathogen after antibiotic
treatment kills normal microbiota
What is selective toxicity?
Selectively finding and destroying
pathogens without damaging the host
Drug efficacy
measure of only the drug's ability to treat whatever condition it is indicated for
What three things do drug effectiveness measure?
- Efficacy
- Tolerability
- Ease of use
What is antimicrobial dosage?
amount drug in a specific time interval
- Must reach optimum therapeutic level
- Must avoid toxicity (side effects)
What is the half-life of a drug?
The rate at which 50% of the drug is eliminated from the plasma
What is synergism in respect to antimicrobial therapy?
the effect of 2 drugs together is greater than the effect of either alone
What is antagonism in respect to antimicrobial therapy?
the effect of 2 drugs together is less than the effect of either alone
What is the disk-diffusion method?
Test effectiveness of chemotherapeutic agents. Zone of inhibition around disk determines sensitivity of an organism to an antibiotic
What is the E Test?
Determines minimal inhibitory concentration (MIC), or the lowest antibiotic concentration preventing bacterial growth.
What is MBC?
Microbial bactericidal concentration, or the lowest concentration of antimicrobial that kills a bacterium.
What is an antibiogram?
Report that records the susceptibility of organisms encountered clinically
What are the 5 antimicrobial modes of action?
1) Inhibit cell wall synthesis
2) Inhibit translation
3) Damage the plasma membrane
4) Inhibit nucleic acid synthesis
5) Inhibit essential metabolite synthesis
Penicillins prevent the synthesis of _________________-
peptidoglycan
Natural penicillins vs. Semisynthetic penicillins
Natural: extracted from penicillium cultures, narrow spectrum for gram positive bacteria
Semisynthetic: Contains chemically added side chains that make them resistant to bacterial penicillinases
What are the three types of penicillins
1) Penicillinase (beta-lactamase) resistant penicillin
2) Extended-spectrum penicillins
3) Penicillins + beta-lactamase inhibitors
What are some examples of antibiotics that inhibit cell wall synthesis?
Pencillins, cephalosporins, carbapenems, monobactam, polypeptide antibiotics (bacitracin and vancomycin)
What antibiotic is considered the last line of defense against antibiotic-resistant staph aureus?
Vancomycin
What are two examples of antimycobacterial antibiotics?
Isoniazis (INH) and ethambutol
Echinocandins are _______ drugs
antifungal
Chlorampehicol binds to the 50S subunit of the 70S ribosome, is broad spectrum, and is (bacteriostatic OR bactericidal)
bacteriostatic
Macrolides (such as erythromycin) binds to the 50S subunit of the 70S ribosome, os very broad spectrum, and is (bacteriostatic OR bactericidal)
bacteriostatic
Aminoglycosides (streptomycin, neomycin, etc.) change the shape of the 30S subunit of the 70S ribosome, can cause auditory damage, and are (bacteriostatic OR bactericidal)
bactericidal
Tetracyclines interfere with tRNA attachment to the 30S ribosomal subunit, are broad spectrum with penetrative properties, and are (bacteriostatic OR bactericidal)
bacteriostatic
Polymyxin B is (bacteriostatic OR bactericidal), interacts with LPS, and is used to treat gram-negative wound/skin infections
bactericidal
Daptomycin is (bacteriostatic OR bactericidal), attacks the bacterial cell membrane, and treats gram-positive skin infections
bactericidal
When fungal ergosterols are affected by antifungals, what happens?
The fungal cell membrane becomes excessively permeable.
What are three types of antifungals that affect fungal ergosterols?
Amphotericin B, imidazoles, and triazoles.
How does the antifungal drug Flucytosine affect fungi?
Interferes with DNA replication and mRNA transcription
Rifamycin and quinolone & fluroquinolones are _______________ inhibiting antifungal drugs
nucleic acid
What do sulfonamides do?
Inhibit folic acid synthesis and competitively bind to enzymes for PABA production
Quinine, chloroquine, artesmisinin, and metronidazole are _______________ drugs
antiprotozoan
Niclosamide, praziquantel, mebendazeole, albendazole, and ivermectin are all _________________ drugs
antihelminthic
Maraviroc, amantadine, rimantadine, and drugs in the clovir group are all ______________ drugs
antiviral
2 categories of antiviral drugs
1) Protease inhibitors
2) Imiquimod
What do persister cells do?
Microbes with genetic characteristics allowing
for their survival when exposed to an antibiotic
What are superbugs?
Bacteria that are resistant to large numbers of
antibiotics
What do resistance genes do?
(R genes) are often spread horizontally
among bacteria on plasmids or transposons
Over _____% of Streptococcus pneumoniae infections are now
penicillin-resistant in many countries
80
When was penicillin-resistant S. aureus first identified?
1947
What are the seven mechanisms of antibiotic resistance?
1) Efflux
2) Inactivation
3) Penetration
4) Target alternation
5) Target overproduction
6) Target bypass
7) Target mimicry
What does an antibiotic efflux pump do?
Remove toxic materials & drugs from cell. Confers cross-resistance to several classes of antibiotics at once
What enzyme is responsible for antibiotic inactivation?
beta-lactamase (penicillinase)
What is antibiotic penetration?
Gram-negative bacteria can alter porin proteins
True or false: DNA mutations in microbial genes can result in antibiotic target alterations
True
What is antibiotic target overproduction?
Enables enough active target to function properly
What is antibiotic enzymatic bypass?
Stop using the target and use another molecule
What is antibiotic target mimicry?
Microbes produce a molecule similar to the antibiotic target to sequester antibiotic
True or false: antibiotic resistance genes cannot be transferred to pathogenic bacteria by horizontal gene transfer
False
According to Dr. Herren, about what percent of all antibiotics go to agricultural use?
60%
What kind of treatment involves administering antibiotics to an entire group of animals to limit wide spread disease?
Metaphylaxis
About how long does it take to develop a new antibiotic?
15 years
What is pathology?
The study of disease. "Path-" meaning disease, and "-ology" meaning the study of.
What is etiology?
The study of the causes of disease. "Eti-" meaning cause and "-ology" meaning study of.
What is pathogenesis?
The development of disease
What is infection? How does that differ from disease?
Infection is the colonization of the body by pathogens (can be asymptomatic/subclinical). Disease is an abnormal state in which the body is not performing normal functions (signs, symptoms, syndromes)
What are the three "S" terms of disease?
Signs - measurable functions
Symptoms - feelings/experiences of function
Syndromes - specific group of signs & symptoms
True or false: infection always causes disease
False
What are examples of a noninfectious disease?
Disease from genetics, nutrition, environment, immune dysfunction, etc.
What is a communicable disease/
infectious disease spread from one host to another (direct or indirect)
What is a noncummunicable disease?
A disease that is not spread from one host to another
What is the incubation period?
interval
between initial infection and
first signs and symptoms
What is the prodromal period?
short period
after incubation; early, mild
symptoms
What is the period of illness?
When disease is most severe
What is the period of decline?
signs and
symptoms subside
What is the period of cavalescence?
body
returns to its prediseased state
What do Koch's Postulates prove?
The cause of an infectious disease
the ID50 is _______
the infectious dose for 50% of a sample population
The LD50 is _______
the lethal dose for 50% of a sample population
What are the steps in pathogenesis?
1) Entry/colonization - adherence
2) Spread - penetration, evasion, damage
3) Exit/transmission
What is a parenteral route with respect to pathogen entry?
When barriers are damaged, allowing pathogen entry. Examples: tetanus, gangrene, HIV
What is the process of adherence in respect to pathogenicity?
Pathogens attach to host tissues by adherence (adhesion). Adhesins (ligands) bind to receptors on the host cells. Some bacteria form biofilms.
Hemolysins, DNases, coagulases, and kinases are examples of _________________.
exoenzymes
_____________ are usually the primary means of virulence & host symptoms, including death.
Toxins
What is toxogenicity?
The ability of a microbe to produce a toxin
What is toxemia?
Toxin circulating in the blood
What is intoxication?
Disease caused by toxin and not by microbial growth
What are endotoxins?
Non-secreted lipopolysaccharides (lipid A portion)
What are exotoxins?
Secreted proteins
What assay is used to test for endotoxins? How is it done?
Limulus amebocyte lysate (LAL). Utilizes amebocytes in horseshoe crab blood that will lyse endotoxin, producing a clot.
What are antitoxins?
Antibodies against specific exotoxins
What ar toxoids?
Inactivated exotoxins used in vaccines
What are the three kinds of membrane-disrupting exotoxins?
Leukocidins, hemolysins, streptolysins
What are capsules?
Glycocalyx outside of the cell wall that impairs phagocytosis by host immune cells
What are some cytopathic effects from a viral infection?
Inclusion bodies in the cell cytoplasm, fusing cells to create a large syncytium, loss of contact inhibition in the cell (causes cancer), producing interferons
Ergot, aflatoxins, and mycotoxins originate from ___________.
fungi
True or false: The respiratory tract, gastrointestinal tract, genitourinary tract, skin, and blood can all serve as portals of exit for pathogens.
True
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