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Foundations Exam 3- Introduction to infectious disease
Terms in this set (119)
How many more people are infected with STIs per year?
The entry, establishment, and multiplication of pathogenic organisms within a host
Define infectious disease
The state of damage or toxicity in the body caused by an infectious agent (any deviation from health)
Any agent that is capable of causing disease in a susceptible host
An organism that lives on or within another organism, from which it obtains nutrients and enjoys protection. The parasite produces some degree of harm to host
An unequal relationship in which one species derives benefit without harming the other
Organisms living in an obligatory but mutually beneficial relationship
What is the difference between prokaryotes and eukaryotes?
Prokaryotes have no nucleus or membrane-bound organelles. Eukaryotes do. Most prokaryotes are unicellular but some are multicellular
Where can one find the normal flora? What is special about them?
They can be found on the skin and exposed mucous membranes. They stay out of sterile tissues or fluids. They adapt to avoid attention of body's defenses
What are transients?
The assortment of superficial microbes whose numbers and type vary depending on recent exposure. Greatly influenced by personal hygeine
What is microbial antagonism?
Bacterial flora benefit host by preventing overgrowth of harmful microbes
What can alter normal flora? What can add the flora back?
Antibiotics, dietary changes, and disease can alter normal flora. Probiotics can add it back
You can do this!
What are sites with normal resident microbes? If not listed, it's abnormal.
Upper respiratory tract
Outer opening of urethra
External ear and canal
External eye (lids, lashes, follicles)
Name three normal flora that can be found on the skin.
3) Candida (fungi)
Name four normal flora that can be found in the upper respiratory tract/oral cavity
3) Candida (fungi)
4) Entamoeba gingivalis (protozoa)
Name three normal flora that can be found in the GI tract
3) Coliforms (escherichia, enterobacter)
Name three normal flora that can be found in the genital tract.
Name two normal flora that can be found in the urinary tract.
Name two normal flora that can be found in the eye
Name three normal flora that can be found in the ear
What are the three categories of microorganisms with regards to oxygen requirements?
1) Those that use oxygen and detoxify it
2) Those that can neither use oxygen nor detoxify it
3) Those that do not use oxygen but can detoxify it
What are the seven oxygen requirement types listed?
Aerobe, obligate aerobe, microaerophile, facilitative anaerobes, anaerobe, obligate anaerobes, aerotolerate anaerobes
What is an aerobe?
Canuse oxygen in metabolism and can detoxify it
What is an obligate aerobe? Give three examples
Use oxygen for metabolism and cannot grow without it. Fungi, protozoa, many bacteria
What is a microaerophile? Give an example
Cannot grow at normal atmospheric concentrations of oxygen but require a small amount of it in metabolism. H. pylori
What is a facilitative anaerobe? Give two examples
Prefer aerobic but can grow with out oxygen using processes such as fermentation. EX: gram-negative intestinal bacteria and staphylococcus
What is an anerobe
Does not utilize oxygen
What is an obligate anaerobe? Where do they live? Give an example
Lack metabolic enzymes to detoxify oxygen, cannot survive in oxygen. Live in deep muds, lakes, oceans, and soil. Clostridium
What is an aerotolerant anaerobe? Give an example.
Does not utilize oxygen but can survive and grow in its presence. EX. lactobacilli
What are the CO2 requirements of microbes? What are capnophiles?
All microbes require some CO2. Capnophiles grow best at higher CO2 levels than normal atmosphere
Name the three types of microbes there are with regards to pH.
Alkinophiles (up to pH 10)
What are some (8) factors that weaken host defense?
1) Being elderly
2) Being an infant
3) Disorders of biochemical hemostasis
8) Hyposplenism and asplenia
What causes the elderly to have weakened defenses? How do they present?
1) Alterations in barriers of skin, lungs, and mucosal linings. Changes in immunity. Decrease response to vaccines. Chronic disease.
2) They present with lack of fever and have nonspecific decline of baseline status. Can have exacerbation of underlying illness
What are two reasons that infants have weakened defenses?
1) Immature immune systems
2) Lack of pathogen-specific immunoglobulins
How does diabetes mellitus affect host defenses?
Hyperglycemia impairs immune response. Vascular insufficiency. Sensory peripheral neuropathy. Colonization of S. aureus and Candida.
What do corticosteroids impair?
2) lymphocyte function
3) Impairment of wound healing (fibroblast function and collagen synthesis)
4) Patients recognition of infection
How does stress harm host defenses?
Reduced NKC activity and decreased lymphocyte mitogen response
What is the difference between a true pathogen and an opportunistic pathogen?
True pathogens can cause disease in healthy persons. Opportunistic cause disease when the host's defenses are compromised
What is the infectious dose? How does it relate to virulence? What is the infectious dose of organisms that pass through the stomach?
1) Estimated number of microbial cells required to make an infection
2) Organisms with smaller infectious dose have higher virulence
3) Organisms going through the stomach require a higher infectious dose
What are the five steps of developing an infection?
1) Find a portal of entry
2) Attach firmly
3) Survive host defenses
4) Cause damage and disease
5) Exit host
What are six common portals of entry?
Skin, conjunctiva, respiratory tract, GI tract, transplacental infection, urogenital tract
What is TORCH? What is it related to?
Toxoplasmosis, Other (syphilis), Rubella, Cytomegalovirus, Herpes simplex virus. Transplacental infection of a fetus
What is the process by which microbes gain a more stable foothold at the portal of entry?
Adhesion. Firm attachment is almost always required
What do bacteria/fungi/ and protozoa have that attach them to the host? Viruses? Parasites?
1) Fibriae, flegella, adhesive slimes or capsules
2) Specialized receptors
3) Suckers, hooks, barbs
What is the microbial property that improves its ability to evade host defenses?
What are three common categories of virulence factors?
1) Antiphagocytic f actors
What is a common antiphagocytic factor used by strep and staph?
Leukocidin (kills WBCs)
What is the antiphagocytic factor that makes it difficult for phagocytes to engulf the microorganism?
Slime layer or capsule
What are exoenzymes?
Extracellular enzymes that can dissolve extracellular barriers and penetrate through or between cells to underlying tissues
What are the five exoenzymes listed in class?
1) Mucinase (Amoebic dysentery)
2) Keratinase (can cause ring worm)
3) Collagenase (Clostridium)
4) Coagulase (staphylococci)
5) Bacterial kinase (Streptokinase and staphylokinase-- dissolve fibrin clots)
What are the two types of bacterial toxins?
Endotoxins (not secreted but is released after cell is damaged)
Exotoxins (secreted by living bacterial cell into infected tissue, includes neurotoxins and enterotoxins)
Compare and contrast toxicity of EX and ENDO
EX: Toxic in tiny ammounts
ENDO: Toxic in high doses
Compare effects on the body between EX and ENDO
EX: Specific to cell type
Compare chemical composition of EXO and ENDO
EX: Small proteins
ENDO: Lipopolysaccharide of cell wall
Compare heat denaturation at 60 degrees celcius of EXO and ENDO
Describe toxoid formation of EXO and ENDO?
EXO: Can make a toxoid
ENDO: Cannot make a toxoid
Describe immune response to EXO and ENDO
EXO: Stimulate antitoxins
ENDO: Do not stimulate antitoxins
Which causes a fever? Endo or exo?
Compare manner of release of EXO and ENDO
EXO: Secreted from live cell
ENDO: Released from cell wall during lysis
Compare the source of EXO and ENDO
EXO: A few GP and GN
ENDO: All GN
What are the four distinct phases of infection and disease?
Incubation, prodromal, period of invasion, convalescent period
During which stage does the organism multiply but the patient remains asymptomatic?
During which stage does the patient have a short period of mild symptoms? How long does it last?
Prodromal stage. 1-2 days
When does the MO multiply at high levels, have great toxicity, and is well established in target tissue? How does the patient feel?
Period of invasion. Is more sick and has specific signs and symptoms
In which stage do the symptoms decline as the patient responds to infection?
What is a localized infection? Give an example
When microbe enters a specific tissue, infects it, and remains confined to it. Boils, fungal skin infections
What is a focal infection? Give an example
Infectious agent breaks loose from local infection and is seeded or disseminated into other tissues. Strep throat causing scarlet fever
What is systemic infection? Give an example?
Occurs when microbe spreads through out the body to several sites and tissues, usually bloodstream. AIDS, syphilis, histoplasmosis, meningitis, rabies
What is a mixed infection?
Several organisms infecting the same site (Dental caries)
What is the difference between a resevoir and a source?
A reservoir is a primary habitat in the natural world from which the pathogen originates. A source is the person or item from which an infection is actually acquired
What are three types of asymptomatic carriers?
Incubation, convalescent, chronic
What is an incubation carrier?
Spread the infectious agent during incubation period
What is a convalescent carrier?
Spread the infection while recuperating without symptoms
What is a disease that is indigenous to animals that humans can acquire?
What is a vector?
An animal that transmits infectious agents
What is a biological vector? Mechanical?
B: Animal that transports and plays a role in life cycle of pathogen, serving as a site in which it can multiply.
M: Animal transports it but is not infected by it
What are characteristics of communicable disease?
Host can transmit it to another host. Can be through direct contact with infected people and their secretions or excretions- contagious.
What is a nosocomial infection?
No present upon admission to a hospital, but occured while being treated there
What is an endemic disease?
A native disease that prevails in a geographic region
What is an epidemic disease?
A sudden outbreak or increase in number of cases in a community
What is an antiseptic?
A growth-inhibiting agent used on tissues
What is sterilization?
Destroys all viable microbes including viruses and endospores
What is disinfection?
Destroys vegetative pathogens, not endospores. Used on inanimate objects.
Where are the two places that a bacterium can have genetic information?
Can bacteria have chromosomes made of RNA?
What are the three types of genes a bacterium can have?
Structural, genes that code for RNA, regulatory genes
What enzyme coils the genome tightly?
How many replication forks does a bacterial chromosome have?
What are the six steps of bacterial chromosome replication?
1) Chromosome is unwound by helicase
2) The template for the leading strand is 3' to 5'. Thus nucleotides are added 5' to 3'.
3) The template for the lagging strand is 5' to 3'. Thus synthesis must proceed backward
4) Before synthesis of the lagging strand, primase adds an RNA primer to direct DNA polymerase 3. Synthesis makes unlinked fragments called okazaki fragments
5) DNA polymerase 1 removes RNA primers and fills in the correct DNA nucleotides
6) Unjoined ends are linked by ligase
What are the four characteristics of plasmids?
1) Extrachromosomal genetic units
2) Double stranded DNA that is smaller than and replicates independently of the cell membrane
3) Genes are not essential for cell growt
4) Transmittable to other bacteria
List the five steps of binary fission
1) We see a parent cell getting ready to being cell cycle
2) The chromosome replicates and the cell enlarges
3) Chromosomes affix to the cytoskeleton and are separated into the forming cells. The septum begins to wall off the cells
4) The septum goes completely through the center and the cell has two seperate chambers
5) The cell cycle ends
What is recombination? What are the three types?
When a bacterium donates DNA to another bacterium resulting in a new strain. Conjugation, transformation, transduction
What is conjugation? What kind of bacteria do this?
Conjugation is when a plasma or fragment DNA is transferred from a donor cell to a recipient cell via direct connection. GN and GP do this.
What is transformation? What kind of bacteria do this?
Lysted bacterial cell breaks into fragments which are small enough to be accepted by recipient cell. The cell captures the DNA in the medium which is inserted into the chromosome of the new cell. GN and GP do this.
What is transduction?
Transfer of genetic material from one to another by means of a bacteriophage vector. Both bacterium must be of the same species
What are transposons?
DNA that can shift from one part of a genome to another. Can go from chromosome to plasmid, vise versa, or within a chromosome. May or may not replicate itself. Important for replacing damaged DNA, changes in traits of colony morphology, and transfer of drug resistance.
What are two ways that a new resistance can occur?
1) Spontaneous mutation in critical chromosomal genes
2) Acquisition of entire new genes or sets of genes via transfer from another species
What are the five mechanisms of drug resistance?
1) Drug inactivation
2) Uptake of drug into bacterium is decreased or eliminated
3) Engagement of a drug transport pump that moves it out of the bacterium
4) Binding sites for drug are decreased in number or affinity
5) An effective metabolic pathway is shut down or another pathway is used.
What are some (8) strategies to limit drug resistance?
1) Make accurate diagnosis and prescribe correct drug
2) Compliance with guidelines
3) Combined drug therapy
5) Reduce abx abuse
6) Limit certain antimicrobials
7) Increase availability of therapy to low-income populations
What are three ways to identify unknown microbes?
Phenotypic, genotypic, immunological
Describe a simple stain.
One dye is used, reveals shape, size, and arrangement
Describe a differential stain
Use a primary stain and a counterstain to distinguish cell types or parts (gram stain, acid fast stain, endospore stain)
Describe a structural stain
Reveal certain cell parts. (Capsule and flagellar stains)
In a gram stain, what do the colors reveal?
Purple are GP and red are GN
In an acid-fast stain, what do the colors reveal
Red are acid fast. Blue are non-acid fast
What stains purple on a gram stain?
Thick layers of peptidoglycan of a gram postive cell.
How do you perform a gram stain?
1) Use crystal voilet (primary dye) to dye both positive and negative
2) Use gram iodine to trap dye in gP cells but not gN cells
3) Use alcohol to try to decolorize the cells (P will not N will)
4) Use safranin to color red. (GP won't, GN will)
What are the three exceptions to the gram stain
Mycobacteria (use acid fast)
Spirochetes (GN but too small to be seen, use darkfield)
Mycoplasma (are neither GN or GP)
What is the chemical used in acid fast stains? What is it used to see? What is in the cellular wall?
3) Mycolic acid
What are the four major shapes of bacteria?
Coccus, bacillus, spiral, pleomorphic
What are the five types of cocci?
1) Diplococci: double
2) Streptococci: Chains
3) Staphylococci: irregular clusters
4) Tetrad: groups of four
5) Sarcina: packet (8-64)
What are the three types of bacilli?
1) Diplobacilli (pair)
2) Streptobacilli (Chain)
3) Palisades (cells of a chain repain partially attached by a small hinge)
What are the two major groups of bacterial appendages and what does each contain?
1) Motility- flagella
2) attachment or channels- fimbriae, pili, and glycocalyces
What are the four types of flagella?
1) Monotrichous- single flagellum at one end
2) Lophotrichous- small bunches emerging from the same side
3) Amphitrichous- flagella at both ends of cell
4) Peritrichous- flagella dispersed over surface of cell
When a flagella rotates counterclockwise, what happens? Clockwise?
What are fimbria? What are pili?
Fimbria: short numerous surface appendage on some bacteria that provides adhesion but not locomotion
Pili: stiff tubular appendages in GN bacteria that join cells for DNA exchange during conjugation
What are the two phases of a bacterium life cycle?
1) Vegetative cell: Actively feeding and dividing form
2) Endospore: small, dormant, resistant derivative
What are the nine steps of the sporulation cycle?
1) Vegetative cell
2) Chromosome is duplicated and separated
3) Cell is septated into a sporangium and forespore
4) Sporangium engulfs forespore
5) sporangium begins to actively synthesize spore layers around forespore
6) Cortex and outer coat layers are deposited
7) Spore completes maturation, sporangium starts to disintegrate
8) The free spore is released when the dead sporangium falls away
9) During germination, the spore swells and releases a vegetative cell
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