HTHS Mod 6

• the study of microorganisms (microbes)
• viruses, bacteria, parasites, fungi, & others

they do not have membrane bound nucleus, membrane bound organelles, or DNA that is organized into chromosomes

• Cytoplasm, ribosomes, nucleoid (chromosome), inclusion bodies, 
• SOME have capsules and some have plasmids
• *SINGLE-CELLED ORGANISMS

• consists of all the single-celled prokaryons
• consist of bacteria and cyanobacteria (blue green algae)

• Into 5 kingdoms, and are classified as either prokaryotes or eukaryotes

• Plantae, Animalia, Protista, Fungi, Monera
• "Pleasantly Ask Properly For Money"
• Kingdoms Monera, Protista, and Fungi especially cause problems for humans

• Prokaryotes belong to the Kingdom Monera and consist of the bacteria and cyanobacteria (blue-green algae)
• *all bacteria and other prokaryotic organisms are earth's most abundant form of life, inhabiting nearly every environmental niche on the planet and are among the smallest organism.
• *despite small size, bacteria have maximum surface area for absorption of nutrients.

• a nuclear region in prokaryotes which is the cell's single chromosome
• circular structure consisting mostly of DNA with small amounts of RNA

medical terminology ~ resembling something

store molecules essential to cell function

• consist of RNA and protein
• are abundant in cytoplasm of bacteria, often grouped in long chains called polyribosomes

Like in eukaryotic, made of large and small subunit and serve as site for protein synthesis

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• fills cell, consisting primarily of water and substances either suspended or dissolved in the water.
• These substances include lipoproteins, carbs, lipids and various enzymes.

• self-replicating extrachromosomal DNA that carry one or more pieces of genetic info
• One way bacteria can exchange info.. (Ex: becoming antibiotic resistant)
• not required to sustain life
• In pic, kinda oval, spherical loopy shape

• some prokaryotes have ability to secrete a capsule
• a protective structure that serves as a defense mechanism.
• tightly bound to cell wall, forms a gel-like (slime) covering that surrounds the bacterial wall
• Human phagocytes (cells that eat foreign invaders) have difficult time attacking
• capsule is considered a major contributor to pathogenicity

• main function is to provide (maintain) shape and stability
• long polymer resembling a chain-link fence
• on top of cell membrane
• contain large polymer called peptidoglycan
• many antibiotics target the cell wall

• makes up prokaryotic cell wall
• an immense, covalently-linked molecule arranged in layers resembling multiple layers of a chain-link fence which gives the cell support

• also called plasma membrane, DEEP TO CELL WALL. 
• Think of it was the "wall paper"
• just like in eukaryotic cell is bi-layer
• regulates transport of material in and out of the cell by transport mechanisms
• contains many complex molecules, including phospholipids, long-chain fatty acids and proteins

• used for locomotion
• organisms displaying a flagella are capable of various degrees of movement, and are said to be motile
• About 1/2 of all known bacteria have one

• singular: pilus, fimbria
• tiny tube-like projections from the cells surface associated w adherence or attachment to other bacteria cells (to transfer genetic material)
• *SEX FOR BACTERIA

another word for Pili

• bacteria are characterized by shape and size
• *before specific culture info is available, physicians use location and appearance characteristics to begin antibiotic therapy

• 1st: cocci
• 2nd: bacilli = coccobacilli - vibrios
• 3rd: spirillia and spirochetes

• singular: coccus
• ("berry, grain") spherical bacterial cells, non-motile
• subcategories: diplo (pair), strepto (chain), staphylo (irregular cluster) and tetra (group of four)

• Singular: bacillus
• rod-shaped bacteria, ("little rod, wand")
• Included coccobacilli and vibrios
• Ex: e coli

• those bacteria shaped btwn a cocci and bacilli
• are oval shaped
• Coccus ("berry, grain") + bacillus ("little rod, wand") = coccobacillus

• the bacteria shaped btwn cocci and bacilli
• exhibit a comma-shape
• *their single flagellum makes them appear to vibrate under the microscope, hence the name
• Ex: Causes cholera
• "collars and vibraters"

• Singular: spirillium
• either loosely-coiled or wavy
• division of one of "third" main bacterial shapes, are long, thin, spiral, rigid rod-shaped cells
• "Will-ya spill em, hold tight!"

• division of one of "third" main bacterial shapes
• are tightly coiled, corkscrew-shaped rods, non-rigid
• hard to see
• Ex: syphilis
• "phyllis cheats (chetes), uncork the wine n unwind"

cocci found in pairs

• cocci which form chains
• strepto- = chains of
• -cocci = round bacteria
• "Steps have straight lines, like chains are straight lines"

• cocci which form grape-like clusters
• staphylo- = clusters of
• -cocci = round
• "like when you bang a staph on the ground, round circles in irregular patters..."

Methasone Resistant Staph Aureus

• Archaeobacteria
• Gram-positive bacteria
• Mycoplasma
• Cyanobacteria
• Spirochetes
• Gram-negative bacteria
• Rickettsias (in eukaryotic cell)
• " Grampa Milo Aready Spoke, Gramndma Can Ride"

• Gram stains
• growth on special agars
• chemical ID helps differentiate and ID

• microscopic method for visualizing bacterial cells
• used when we want a quick look at what organisms might be causing the pt's disease
• Groups medically important bacteria into two categories: Gram positive or gram negative bacteria

• 1 ~ a sample is smeared on slide and fixed w heat
• 2 ~ slide is stained w crystal violet (purplish dye) for 1 - 2 minutes
• 3 ~ Gram's iodine is used to "fix" the crystal violet (helps to retain the stain)
• 4 ~ Acetone is used to decolorize the slide
• 5 ~ counter stain the slide with safranin (pink)

• stain purple
• have thick, peptidoglycan-rich cell wall that also contains teichoic acid, causes retention (holding it in) of crystal violet (blue) dye
• *when it's decolorized and counterstained, it stains purple cause it doesn't let go of the first stain

• stain pink
• have a thin peptidoglycan cell wall and a lipoprotein-rich (again, bi-layer membrane) cell membrane
• releases crystal violet dye when rinsed w alcohol
• The safranin (pink) counterstain is retained

• Gram-neg walls have an outer membrane, contains lipopolysaccharide, which is an endotoxin.
• This is a toxic component
• Endotoxin has been known to kill people with severe infections

• a nutritive substance, such as an agar gel or liquid medium, in which cultures of bacteria, fungi, animal cells, or plant cells are grown
• Can be liquid or semi-solid (called agar, which is kinda jello-like)
• *"agar plate" is the little slides for microscope

• sheeps blood agar (SBA)
• *blood to bacteria is like candy

• methods in which most bacteria can be studied
• promotes growth of the bacterial cell on artificial culture media.
• can be either liquid or semi-solid forms which contain agar (a neutral, gel-like substance derived from seaweed)

• dense masses of bacteria
• how they grow/form when mixed w nutrients

Enriched, Selective, Differential

• contains substances that bacteria love that encourage the growth of bacteris
• used as general overview of what's growing 
• include sheep's blood agar and chocolate agar

• contains inhibitors that allow certain types of bacteria to grow and form colonies while inhibiting others
• Ex: MacConkey agar allow only growth of gram negative organisms

• roughly groups bacteria based on fermentation of carbs.
• Gram-neg bacteria that use lactose will grow
• grow pink or red, if they don't use lactose, will be clear
• Ex: MacConkey agar which contain sugar lactose. Bacteria that ferment lactose turn red, those who don't are colorless

• pink, has bio-salts n stuff that gram-positive don't like, Gram-neg will grow
• both selective and differential

Aerobes, Anaerobic and Microaerophils

• LOVES OXYGEN
• require atmospheric oxygen, often enhances with additional carbon dioxide (CO₂)
• Use special incubators
• Ex: Streptococcus, Staphylococcus, and E. coli

• require special conditions that remove atmospheric oxygen (O₂)
• HATE OXYGEN
• Special chambers and jars that remove atmospheric oxygen may be used ; can use candle
• Ex: Clostridium species which cause disorders such as gangrene, botulism, and tetanus (stepping on rusty nail)

• these organisms grow best in environment of reduced oxygen and increased CO₂ (carbon dioxide)
• may be grown in a jar which a candle is lit before jar is sealed. (burning of candle uses the oxygen in jar and adds carbon dioxide)
• Ex: Camplybacter which causes intestinal disorders

• term used to describe cell division in bacteria
• process of growth and division continues as long as favorable environmental and adequate nutritional conditions exist
• also known as transverse fission

• Term used to describe cell division in bacteria
• another name for binary fission

• do not have cell cycle
• are continuously dividing and replicating their DNA, as long as their are in favorable and nutritional conditions
• Phases: Lag Phase and Log Phase

• 1. Nucleoid elongates
• 2. Nucleoid divides, cell wall and membrane begin to form transverse septum (similar to cleavage furrow)
• 3. Transverse septum becomes complete
• 4. Daughter cells separate

• Lag Phase
• Log Phase
• Stationary phase
• Decline (death) phase

• The "gear-up" phase
• not greatly increasing in #, but metabolically active (growing, synthesizing enzymes, and producing large amounts of ATP)
• do not reproduce in significant #'s during this phase

• the period of rapid, exponential growth
• generation time: genetically determined period of logarithmic growth
• will continue as long as there are sufficient nutrients and environment has suitable conditions for synthesis of ATP

• how long it takes a bacteria to divide
• the genetically determined period of logarithmic growth which varies by bacterial species from minutes to hours
• Most are under 10 hrs

• "leveling off" period, the phase of bacterial growth in which non-replicating cells (those dying off) are about the same in #'s as those still reproducing new cells
• Cells are running out of nutrients

• happens once the essential atmospheric, temp and nutritional conditions for log phase are depleted
• The # of cells dying is greater than # of new cells arising from division
• cells lose their ability to maintain metabolic funtions

• means "living together"
• bacteria may form 3 different symbiotic relationships w a living host:
• Mutalism, parasitism, and commensalism

• type of symbiotic relationship, both members of association benefit
• Ex: Escherichia coli (E. coli) in large intestine of humans. We provide nice, warm environment; we benefit from Vit. K produced from E. coli, which is essential for clotting process. Also ward off disease-causing organisms and help digest cell walls of plants. So, beneficial.

• one organism, the parasite, benefits from the relationship and the other organism, the host, is harmed.
• Many types
• Ex: malaria and tapeworms

• one organisms benefits and the other neither benefits or is harmed.
• Ex: bacteria which live on our skin

• the vast majority of microbes that make up our indigenous flora
• living within humans w/o causing disease

• Measles virus
• can penetrate the placenta and infect the fetus

• HIV
• another organism which can penetrate the placenta and infect the fetus

• *because they develop in sterile environment, newborns must acquire microorganisms from interaction w their environments ~ over time become part of their human microflora
• Therefore, newborns may become infected w pathogens during birth
• Ex: thrush (yeast) in throat or tongue, on "boonie"
• Group B streptococcus ~ acquired during birth (can be in vaginal tract), can cause severe, life-threatening infection
• Candida (yeast) ~ thrive cause of infant's moist skin and lack of normal flora

• a bacteria which live on or in body but do not usually cause disease 
• exist either as resident or transient, using secretions of host as nutritional sources
• Most in lower digestive tract
• Always present in varying pop. in following areas:
• The skin and hair (staphylococci, Bacillus species, others)
• Conjunctive (usually match those found of skin)
• Mouth, nose, and throat (staphylococci, streptococci, yeasts... etc)
• Passageways of intestinal, reprod and intestinal tracts.

• helps prevent disease-causing organisms from getting in and taking hold (causing illness)
• -In skin, conjunctiva, mouth, nose, throat, urinary, reproductive, and GI tracts

• "come and go" organisms that exist in same areas occupied by resident flora
• can be acquired almost anywhere, and may persist for hours, months, or years
• may become opportunists

transient microflora which may cause opportunistic infections in hosts whose protective mechanisms have been compromised or the pop. of resident microorganisms change

• when you take antibiotics, your killing off good flora also.
• So, the probiotic is a pill full of normal microbes to help replace the good flora that's being killed off by antibiotic

an organism which benefits from it's relationship with the host, but harms the host - causing infection

• often results in disease in the host
• depends on the organism's ability to invade the host, multiply, and avoid damage from host's defenses

• term used to describe the intensity of bacterial and other microbial infections
• varies greatly among different organisms, but is always a factor in infections
• Specific pathogenic mechanisms which contribute to this are adherence, colonization and formation of a capsule

Adherence, colonization, and formation of a capsule

• a specific pathogenic mechanisms in which bacteria use the pili to cling to the surface of host cells, multiply and form colonies
• *Ex: staphylococcus aureus has surface proteins that bind to human connective tissues, including blood.  Contribute to virulence of S. aureus

• an enzyme which contributes to the virulence of S.aureus
• surface proteins that bind to human connective tissues, including blood

• a specific pathogenic mechanism
• once in place within host tissue, bacterial replication forms colonies, and may overcome host defenses
• *colonization by small #'s of non-invasive organisms is normal in all animals including humans

• a specific pathogenic mechanism
• in certain pathogens, the capsule contributes to the organism's virulence because this thick, polysaccharide structure helps organisms resist host defense processes

the ability of organisms to penetrate host tissue, usually via special enzymes

• Hyaluronidase
• Coagulase
• Streptokinase and staphylokinase

• an enzyme which contributes to invasiveness and pathogenicity
• also known as spreading factor
• is produced by streptococci, staphylococci & some other pathogens
• the enzyme attacks hyaluronic acid which is the interstitial cement ("ground substance") of connective tissue
• "always think of mayonnaise when you see this, so think of "spreading mayonnaise" - for spreading factor"

• an enzyme which contributes to invasiveness and pathogenicity
• forms blood clots
• produced by some bacteria that accelerates the clotting of blood, often providing protection from host defenses leading to abscess formation.
• species of staphylococcus produce this enzyme

• an enzyme which contributes to invasiveness and pathogenictiy
• breaks down collagen, the framework of muscles

• an enzyme contributing to invasiveness and pathogenicity
• produced by pathogenic streptococci 
• "Kinase" enzymes digest fibrin and prevent the clotting of blood (by digesting blood clots)
• resulting reduction of fibrin allows more rapid diffusion of the infectious bacteria into host tissue
• *Used in human medicine, similar to enzyme derived from streptococcus, for people who form clots in blood when they shouldn't
• Ex: "flesh eating bacteria" is a streptococcus strain that produces streptokinase

• an enzyme contributing to invasiveness and pathogenicity
• produced by pathogenic staphylococci
• "Kinase" enzymes digest fibrin and prevent clotting of blood. (digest blood clots)
• resulting reduction of fibrin allows a more rapid diffusion of the infectious bacteria into host tissue

the protein in our blood clots

Exotoxins and endotoxins

• very powerful toxins secreted by living bacterial cell
• Mostly from gram-positive organisms
• *Botox: exotoxins from botulism, given in very small doses to relax muscles of face, therefore ridding of wrinkles
• Ex: botulism, gas gangrene, tetanus, and staphylococcal food poisoning

• found primarily in gram negative bacteria, are released only when gram-neg organism dies
• particular risk when giving antibiotics which may result in death of many organisms, leading to anaphylactic shock in pt.
• also cause non-specific gastrointestinal symptoms such as diarrhea, cramping, and generalized malaise
• associated w cholera, some types of salmonella & other similar types of toxin-associated bacterial food or water-borne infections

• is a feeling of general discomfort or uneasiness, of being "out of sorts", often the first indication of an infection or other disease.
• "general feeling of being unwell"

• dormant stage of some bacteria
• form when nutritional and environmental conditions are unfavorable for growth
• have thickened cell walls to withstand harsh conditions such as excessive cold, heat or dryness
• revert to active cells under favorable conditions
• *comprised of core (middle), cortex and spore coat
• Ex: clostridia species that cause tetanus, botulism and gas gangrene

a process by which endospores, which have been dormant, become active again

• by three fundamental processes:
• Transduction, transformation, and conjugation
• this exchange of genetic material may contribute to the ability of some bacteria to acquire antibiotic resistance

• just  "phage" for short
• virus that infects bacteria
• "bacteria-eating"

• a piece of bacterial chromosome which has been infected w a virus 
• host cell chromosome acquired both phage DNA and genes from previous host
• *virus gets in and takes over host DNA

• an asexual genetic process
• uses a bacteriophage to insert the resistant DNA into the bacterium

• virus invades bacteria, prophage formed in bacterial chromosome
• prophage splits off from bacterial chromosome (leaving some corrupted DNA behind)
• phage DNA incorporating some bacterial genes, replicates
• bacterial cell is lysed (explodes), phages are released
• phage infects new host cell, incorporates into chromosome & new host (again) acquires both phage DNA and genes from previous host

• when a bacterium dies, fragments of it's DNA are taken up by neighboring bacteria
• *not all bacteria have the ability to take in pieces and parts from other bacteria
• These naked DNA fragments are taken up by the recipient cell through the action of carrier proteins found in cell membrane
• Fragments are then "spliced" into host cell's DNA by enzymatic action

• differs from transformation and transduction cause it requires contact btwn 2 bacteria
• utilizes a plasmid
• transfers a greater amount of DNA than transformation or transduction
• *at the F-pilus (sex pilus) that DNA is transferred from 1 cell to another, usually in much larger amounts that other two

• "F" refers to "fertility"
• sex pilus of bacteria used in conjugation
• allows bacteria to adhere to each other
• "string" or "tube" like "penis" (but not really) from donor bacterium to recipient bacterium, to transfer large amounts of DNA

• extrachromosomal pieces of DNA in cytoplasm of some bacteria (separate chromosomal piece in cytoplasm, besides nucleoid)
• through plasmids, bacteria often develop drug resistance

plasmids which assist bacteria in developing drug resistance

The transfers of DNA which develops new strains of bacterium including antibiotic resistant strains

• include substances used to specifically treat infectious microbial diseases
• Can be bacteriocidal or bacteriostatic

an antimicrobial agent which kills the organism

an antimicrobial agent which inhibits organism growth and allows immune defenses to act against the invader

antimicrobial agents containing substances derived from other organisms

• some affect the cell wall (penicillin)
• some disrupt the cell membrane
• some alter protein synthesis and genetic activity

• Antimicrobials can either be:
• broad spectrum or narrow spectrum drugs
• spectrum of activity of antibiotics varies among the types of antibiotics

are effective against a wide range of microorganisms including both gram positive & gram negative bacteria

• are effective against a limited number of microorganisms or a single taxonomic group
• Ex: the use of penicillin to treat streptococcal pharyngitis

• increases each year, occurs through:
• Overuse of antibiotics (also through not finishing antibiotics... gives bacteria change to become resistant)
• Plasmids
• Genetic transfer mechanisms
• Development of neutralizing enzymes (neutralize effect of antibiotic) 
• Alteration of pathways used by antibiotic
• Altering cell membrane  (to block antibiotic entry into bacterial cell)

• also called the Kirby-Bauer method
• first widely used lab method in determining the susceptibility or resistance of a clinical isolate
• uses paper discs impregnated w a specific concentration of antimicrobial to be tested
• test organism is "seeded" over the plate & incubated for several hours
• Zones of inhibition are measured & compared to those for control organisms w known zone sizes.
• Results are reported as sensitive, intermediate or resistant

• Pharyngitis (streptococcus pyogenes), causes strep throat, common in winter
• Other bacterial infections invade ears, eyes, sinuses and upper bronchioles

• bacteria-caused pneumonia or bronchitis.. organism is down in lungs
• Haemophilus influenzae, Klebsiella pneumoniae, and Streptococcus pneumoniae are top 3 and ALL CONTAIN A CAPSULE VIRULENCE FACTOR

• often acquired from contaminated food or water
• include Salmonella and Shigella species as well as Staphylococcus aureus
• *E. Coli O157:H7, specific type of E. Coli common to the intestinal tract of cattle, has been linked to contaminated meats and veggies

• involve infections of the cerebrospinal fluid and meninges, can be caused by several bacteria
• Common examples are:
• In young children: Haemophilus influenzae 
• In young adults: Neisseria meningitidis 
• Vaccines are now available for protection

• caused by organisms who can secrete toxins which either cause disease directly, or trigger an abnormal response in the body which causes illness
• Ex: botulism, tetanus, and toxic shock syndrome

Chlamydia and Rickettsias

• Mycoplasma, Chlamydia, Rickettsias
• don't stain easily, different
• obligate intracellular organisms

cannot live freely, must live inside a eukaryotic host cell

• Obligate intracellular organisms
• The most common STD in the US; causing pelvic inflammatory disease (PTD) in women & urethritis in men.
• Another variant causes epidemic conjunctivitis in newborns acquired during passage through the birth canal
• Require a eukaryotic cell for replication
• Ex: Chlamydia trachomatis causes a variety of human infections

• A complex organism that has multiple serological variants which cause a variety of human infections.
• Ex: Trachoma, STD's and conjunctivitis in newborns acquired during birthing process

• an eye infection caused by Chlamydia trachomatis  

One of the leading causes of blindness in the world

• obligate intracellular parasites with complex life cycle
• normally inhabit arthropod vectors (such as ticks, lice, fleas, etc.)
• Transmission to humans is through a bit
• most prevalent in US is Rocky Mtn. Spotted Fever
• Lime Disease
• *Utah doesn't have tick that causes these diseases

• the tiniest free-living organisms
• unique in the bacterial world cause they do not have a cell wall ~ therefore have no set shape
• diverse in nature, especially in many animal & bird species
• Some species actually make up normal respiratory and urogenital microflora of humans

attaches to surface epithelial cell sites and causes a respiratory disease primary atypical pneumonia (walking pneumonia)

• are obligate intracellular parasites
• need a host cell; virus provides the RNA or DNA to replicate, takes over genetic machinery of host cell
• Contain RNA or DNA (NOT BOTH)
• RNA viruses also contain code for reverse transcriptase, enzyme which makes DNA from RNA
• Are DNA viruses OR RNA viruses
• Over half of all human infectious processes are due to viruses

they change their antigens frequently, so they are continually changing

in general, viruses are broadly classified as either RNA or DNA viruses based on the make-up of their genome

• Nucleic acid (RNA or DNA)
• Capsid
• envelope

• A virus contains either a single or double strand of DNA or RNA
• in nuclear region
• differing among viral groups

• protective coating enveloping the nucleic acid in viral cell
• determines the shape of the virus
• Composed of capsomeres
• can be helical, polyhedral (multi-sided), or in some cases bullet-shaped
• (NOT TO BE CONFUSED WITH THE BACTERIAL CAPSULE)

the individual protein subunits which make up capsids

• the combined capsid/nucleic acid arrangement 
• (viral structure)

• when present, are external to the capsid & are acquired from the combo's of proteins, lipids and carbs found in host cell
• many viruses have glycoprotein spikes
• These structures account for high degree of both host, and host cell, specificity of viruses
• many also serve to "hide" virus from being attacked by host's immune system

• also referred to viral progeny
• 5 step replication cycle:
• ~1 Adsorption
• ~2 Penetration
• ~3 Synthesis
• ~4 Maturation
• ~5 Release
• "A Penis Soothes My Rages"

a single, complete virus unit

• Step 1 in 5-step viral replication cycle
• Attachment of the virus to host cell
• W/ enveloped viruses, the glycoprotein spikes attach to specific matching sites on hosts cell wall
• W/ naked (non-enveloped) viruses, attach to specific molecular sites on cell surface

• Step 2 in 5-step viral replication
• follows quickly after adsorption, process by which virus enters host cell via endocytosis or fusion w cell membrane of host
• Once inside, virus uncoats
• free strand of nucleic acid then moves to host cell's nucleus
• "Sexual penetration requires no clothes"

upon entering host cell, virus immediately loses envelope and capsid

• Step 3 in 5-step viral replication
• produces new genetic material and varies btwn RNA and DNA viruses
• W/ DNA viruses, the DNA is synthesized in orderly manner in nucleus, using viral enzymes in transcription
• Proteins are synthesized in cytoplasm using host cytoplasmic enzymes and by using the host cell ribosomes and Golgi organelles

• Step 4 in 5-step viral replication
• the assembly, or "packaging" of the newly synthesized molecules into complete virions (new little baby viruses)
• occurs as soon as abundance of viral nucleic acid, enzymes and proteins have been synthesized
• some viruses are capable of inserting viral genetic material into host's genome permanently, which is then capable of producing new viruses. Can occur years after infection

• Step 5 in 5-step viral replication
• the departure of the new virions from the host cell
• is this final cycle of viral reproduction that may be the cause of symptoms in host
• Some viruses rupture host cell releasing virions; others release viruses and host cell remains intact in process called budding
• enveloped viruses form their envelopes from host cell membrane as they exit the cell

• viruses are very specific about which animal/animal cell they target for infection
• nature of infection depends on type of virus, system affected and host response
• Several types of viral infections that fall into two main categories: acute and latent (persistent)

• Disease cycle is relatively short
• Host cell rupture and virus spreads to neighboring cells
• After sufficient cellular damage, symptoms rapidly appear in infected host. 
• It's up to host's immune defenses to eradicate viral invaders, as well as provide measure of protection from future exposure to viral agent
• Ex: common cold (rhinovirus), influenza (types A and B), hepatitis viruses

• vary widely in scope
• once in cell, infection proceeds by replication of essential enzymes and proteins, but viral material (also called provirus) remains in host and replicates new virions when "triggered"
• virus becomes relatively inactive but reemerges
• provirus remains in host cell
• Replicates new virions when triggered by some external event (stress, fever, etc.)
• Ex: herpes virus, Epstein-barr Virus, HIV

• classic example of virus causing both acute and latent/persistent viral infection
• Cold sores are acute phase of herpes infection

• infectious mononucleosis
• immune system viruse

• cancer-producing viruses
• possess oncogenes that cause uncontrolled and abnormal division of host cells by altering cell cycle "checkpoints" 
• Ex: hepatitis B, Hepatitis C, Human Papilloma virus

cancer-causing genes which cause the uncontrolled and abnormal division of host cells

virus which has been directly linked to cervical cancer in women

• MOST EFFECTIVE means of preventing many viral diseases is through use of vaccines
• very few effective therapies; antibiotics are ineffective since they act on bacterial cell components not found in viruses
• Some antiviral drugs do slow down attachment of virus to host cell
• Some simply suppress, do not cure, viral infection
• Vaccines targets at viruses include polio vaccine, Gardasil for cervical cancer, and the hepatitis vaccines

• infectious proteins w/o genetic material (meaning no nucleic acid) that come into contact w normal proteins and transform them into more infectious prions
• Prion diseases are found in humans & other animals, derive name from proteinaceous infectious particle
• All known prion diseases affect the cells of the brain

• the current collective terminology for prion diseases
• "spongiform" comes from cytopathic effect on brain tissue
• infection produces microscopic holes in brain which resemble holes in sponge

• generally resistant to inactivation by heating to 90°, a temp that will inactivate most viruses
• infection is resistant to radiation treatments which inactivate organisms w genomes
• not susceptible to enzymes that inactivate RNA and DNA
• susceptible to protein denaturing agents

• bovine spongiform encephalopathy (BSE) : "mad cow disease," causes a slow loss of neural function and eventual death. Humans are believed to acquire by ingesting infected animal by-products
• Creutzfeldt-Jakob disease  the human variation; slow, neural degenerative disease, resulting in eventual death
• Scrapie variation in sheep
• Chronic wasting disease  variation in deer and elk
• NO EFFECTIVE TREATMENT FOR ANY PRION DISEASES

• important for decomposition and recycling of organic material
• include mushrooms
• medically important
• divided into two groups: yeasts and molds
• some are human pathogens, some are toxic and hallucinogenic

• produces spores whose arrangement and appearance depend on fungal species
• some cause opportunistic infections, especially among those w compromised immune systems
• Many affect respiratory system due to inhalation of spores from environment

• varies, but are usually limited to infections of the hair, nails and skin
• includes infections as athlete's foot, jock itch and ringworm
• other infections, usually found in tropical regions, cause moderate to serious infections

unicellular fungi; important in bread, beer & alcohol production, and other applications

Several species exist as normal flora, especially on mucus membranes and GI tract

• Some species are opportunistic pathogens of humans which take advantage of weakened defenses
• Most common caused by Candida albicans  which causes thrush (infection of mouth and pharynx) & vaginitis
• Those w diabetes & compromised immune systems most susceptible, systemic infections do occur

• two large groups: single-celled protozoa & multi-celled helminths (worms)
• Protozoa are in kingdom Protista
• Helminths, like humans, are in kingdom Animalia

• an organism that lives at the expense of another organism
• transmitted to humans by vectors ~ biologically, ex: mosquito transmitting malaria. ~ mechanically, Ex: transmission of parasite eggs to food by flies & other insects
• endemic to much of worlds population, especially in underdeveloped countries
• account for up to 20 million deaths per year, either from parasitic disease itself, or from complications from disease

• single-celled, in kingdom Protista
• in general, 2 stages: trophozoite & cyst stage

protozoa stage which is infective;  the motile, invasive form of the organism

protozoa stage which allows the organism to survive in a dormant state in the external environment

• very common protozoan disease for humans, found worldwide
• Humans become infected by ingesting the cysts in water contaminated by animal carriers
• a flagellated protozoan causing intense gastrointestinal distress & diarrhea
• can be treated w antibiotics

• common protozoan pathogenic for humans
• become more prevalent
• causes self-limiting GI symptoms
• Infected individuals can become chronic carriers, potentially have ability of infecting others
• associated with recreational water use (public swimming pools)

• common pathogenic protozoan for humans, who are intermediate hosts
• causes malaria
• first goes after liver, next generation affects red blood cells
• causes over 1 million deaths per year, most are young children in Africa
• several species, all transmitted by Anopheles mosquito
• organism invades RBC's during asexual phase of life cycle
• can't survive in humans w sickle-cell disease

• (Worms)
• come in four groups: flukes, tapeworms, roundworms and tissue parasites (which can be a roundworm, larval form or tapeworm)
• hosts are definitive or intermediate, or accidental

host for helminth which harbor the parasite when it reproduces by sexual reproduction

hosts for helminth which harbor the parasite at some developmental stage in it's life cycle

• hosts for helminth which are not part of the normal life cycle of the infectious parasite
• most are also 'dead end' hosts, they do not transmit the infection further

tapeworms and roundworms

• segmented worms that contain a head (scolex) and many segments (proglottids)
• are hermaphroditic, containing both ovaries and testes
• infective stage is larvae found in cattle and swine

• intestinal, found throughout world.
• Adults live in lumen of intestinal tract
• human infection occurs either by ingestion of mature egg (ovum) or by penetration of skin by larval stages found in warm, moist soil.

• Pinworms
• "Helminths"

• the giant intestinal roundworms
• "helminths"

can penetrate skin

common intestinal worm

• bacteria that causes pharyngitis
• "strep throat"
• upper respiratory tract infection
• common in winter

• one of top 3 bacterial organisms which can cause pneumonia
• contain a capsule virulence factor
• involved in lower respiratory tract infection (lungs)

• one of top 3 bacterial organisms which can cause pneumonia
• contain a capsule virulence factor
• involved in lower respiratory tract infection (lungs)

• one of top 3 bacterial organisms which can cause pneumonia
• contain capsule virulence factor
• involved in lower respiratory tract (lungs)

• type of bacterial organism which infects the GI tract
• acquired from contaminated food or water

• type of bacterial organism which infects GI tract
• acquired from contaminated food or water

• type of bacterial organism which can infect GI tract
• acquired from contaminated food or water

• a specific type of E.coli organism, bacterial
• common in intestinal tract of cattle, has been linked to contaminated meats and veggies

• type of bacterial organism which infects the cerebrospinal fluid and meninges
• particularly in young children
• vaccine is available

• type of bacterial organism with infects the cerebrospinal fluid and meninges 
• particularly in young adults
• vaccine is available

• botulism
• secretes toxins
• bacterial

• tetanus
• secretes toxins
• bacterial

• toxic shock syndrome
• secretes toxins
• bacterial

• species of yeast that cause the most common yeast infections
• causes thrush in the mouth and vaginitis