Exam 3

What are the characteristics of Clostridium difficile?

gram positive, rod shaped, spore forming, anaerobe

Where does C. diff. reside? What percentage of the bacterial infection there is it?

Naturally lives in the gut (2-5% bacterial population)

C. diff uses what type of situations to infect? (not the actual type of situation, the category)

opportunistic

In what situations can someone get C. diff?

antibiotic treatment, HAI, advanced age, immunocompromised, long stays in healthcare facility, gastrointestinal surgery

Explain why someone on antibiotic treatment is susceptible to C. diff?

The treatment eliminates the bacterial part of normal flora that surpasses C. diff overgrowth

What is Antibiotic Associated Colitis?

Collection of inflamed cells, dead cells, necrotic tissue, and fibrin that obstructs the intestine.

What are effects of Antibiotic associated colitis?

server diarrhea, abdominal pain, fever, pseudomembranousal colitis

What does C. diff produce that is part of infection?

toxins

How many death super year is C. diff associated with in the US?

14,000

Who is the main carrier of C. diff to the patient in the fecal-oral route?

Healthcare personnel

How can C. diff be detected?

stool culture, molecular, antigenic testing, detection of toxin

What is the problem with using stool culture in C. diff detection?

1. can show false negative (nontoxigenic strain)
2.turn around time is slow

Explain molecular testing detection of C. diff?

tests for the gene encoding the toxin

Explain antigenic testing in detection of C. diff?

specific antigens on the cell's surface

Explain detection of toxin in the detection of C. diff?

toxins degrade rapidly at room temperature

How can you treat C. diff?

Antibiotics for 10 days (must be completely healthy before take off), fecal transplant

What is the problem with using antibiotics to help treat C. diff?

The antibiotics can still kill the good flora in the gut

What antibiotic are used in treatment of C. diff?

metronidazole (flagyl), vancomycin

Explain feca; transplant in treating C. diff?

the transfer of feces from a healthy individual to an infected individual to reestablish the normal flora

Why are viruses important?

major cause of disease, new source of therapy, new viruses are emerging, important in genetic variation

What "world" are viruses a member of? Why?

the aquatic world. They make organic matter from particulate to dissolved

Why are viruses important in genetic variation?

they transfer genes between bacteria and others

What is a virion?

The complete virus particle, Consists of \> or \= 1 molecule of DNA or RNA enclosed in protein coat

Explain reproduction and cell division of virions

They cannot reproduce independently of living cells nor carry out cell division, but they can exist extracellularly

What type of cells do virions infect?

All types: bacterial viruses (bacteriophages), few archaea viruses (protists, fungi, plants, animals - most eukaryotic)

various are classified into families based on....

genome structure, morphology, life cycle, genetic relatedness

Describe the structure of virions?

range of 10-400nm in diameter, contain nucleocapsid, some have envelope

Describe the nucleocapsid

Nucleic acid (DNA, RNA) and protein coat (capsid)

What does "having" and envelope mean?

It is an enveloped virus

What does lacking an envelope mean?

It is a naked virus (no envelope)

Describe the capsid?

large macromolecular structure which serves as protein coat virus

What is the function of the capsid?

Protects the viral genetic material and aids in its transfer between host cells

What is a capsid made of?

protein subunits called promoters

Wha are the shapes of capsids?

helical, icosahedral, complex

Describe helical capsids

shaped like a hollow tube (nucleic acid in here) with protein walls. promoters self-assemble. Size of capsid is function of nucleic acid

Describe icosahedral capsids

regular polyhedron with 20 equilateral faces and 12 vertices

What capsid is "nature's favorite shape"?

icosahedral

Describe complex capsids

virus capsids that don't fit into the other categories

What is an example of a complex capsid?

Large bacteriophages ("final symmetry" - icosahedral head and helical tail), Poxvirus

Many viruses are bound by the envelope. Describe it.

outer, flexible, membranous layer

What are animal virus envelope made of?

Made of lipids and carbohydrates.

Where do animal viruses usually arise from?

host cell plasma or nuclear membranes

Describe envelope proteins in viruses

viral encoded, may project from the surface as spikes or peplomers

What are envelope proteins involved in?

viral attachment to host cell, ID of virus, may have enzymatic or other activity, may play a role in nucleic acid replication

Are viral genomes diverse or uniform?

Diverse

Describe the possibilities of a viral gnomes structure?

single or double stranded DNA or RNA, different size of nucleic acid, segmented or circular

The mechanism of viral multiplication used is dependent upon what?

viral structure and genome

What are the steps of viral multiplication?

Attachement (to host cell), entry, uncaring of genome (separated from protein coat), synthesis (new proteins made), assembly, release (of the virus)

What is another name for the attachment phase of viral multiplication?

Adsorption

Explain the attachment step of viral multiplication

attach to specific receptor which determines the host preference

The specific receptors in viral attachment may be what?

specific tissue (tropism), more than one host, more than one receptor, in lipid rafts providing entry of virus

What enters the cell in viral entry and uncoating?

the entire genome or the nucleocapsid. Varies between naked and enveloped virus

What methods are used in viral entry/uncoating?

1. fusion of the viral envelope with host membrane (nucleocapsid enters)
2. endocytosis in vesicle (endosome aids in uncoating)
3. injection of nucleic acid

What dictates the events of the synthesis stage of viral multiplication?

the genome

what is unique about RNA viruses in their synthesis stage of viral multiplication?

The virus must carry in or synthesize the proteins necessary to complete synthesis

Explain assembly in viral multiplication

complicated: bacteriophages happen instates, some are assembled in the nucleus and some in the cytoplasm, may be seen as paracrystalline structures in cell

How are non enveloped viruses released? What do the proteins attack?

they lyse the host cell. May attack the peptidoglycan or membrane

How are enveloped viruses released?

They use budding.

What first happens in budding (in release)?

viral proteins are first incorporated into the host membrane

What happens to the nucleocapsid in budding?

nucleocapsid may bind to viral proteins

Where is the envelope derived form in budding?

the envelope is derived from the host cell membrane but may be Golgi, ER, or other

What does the virus use host actin and oils for?

to propel though the host membrane

What are the different types of viral infections?

bacterial and archaeal, in eukaryotic cells, cancer

How do virulent phages work in bacterial and archaeal infections?

one choice: multiply immediately upon entry and lyse the bacterial host cell

How do temperate phages work in bact. and archaeal infections?

two choices: reproduce lytically or remain within host cell without destroying it

What do temperate phages do when they remain in the host cell? What is this called?

integrate their genome into the host genome. Called lysogeny

What does the prophage/bacteriophage do in lysogeny?

integrated phage genome

What do lysogens (lysogenic bacteria) do in lysogen? What cycle can it switch to?

infected bacterial host - appear normal, can switch from lysogenic to lytic cycle

What changes the phenotype of its host? What is a result of this?

temperate phage - bacteria may become immune to superinfection, phage may express pathogenic toxin or enzyme

What is the advantage of lysogen for the virus?

the phage is protected and remains viable but may not replicate

Under appropriate conditions, the phages will do what in lysogenic conversion?

lyse and release phage particles

What causes the appropriate conditions needed for phages to lyse and relate particles?

conditions cause induction \= prophage to initiate synthesis of new phage particles

In what cells do cytocidal infections happen?

eukaryotic cells

what happens in cytocidal infections?

cell death through lysis

Persistant infections occur in what cell types? How long?

eukaryotic cells, may last years

What are cytopathic effects (CPEs)?

degenerative changes, abnormalities (transformation into malignant cell)

Infected eukaryotic cells can transform into what type of cell?

malignant cell

What is a tumor?

growth or lump of tissue

what is neoplasia?

abnormal new cell growth and reproduction due to loss of regulation

What is anaplasia?

reversion to a more primitive or less differentiated state

What is metastasis?

spread of cancerous cells thought the body

What is carcinogenesis?

normal cells transform into cancer cells: multistep process, involves oncogenes

What are oncogenes?

Cancer causing genes that my come from the virus. May be transformed host proto-oncogenes

What cancer does Epstein Barr virus cause?

Burkitt's lymphoma

What cancer does Hep. B virus cause?

hepatocellular carcinoma

What cancer does Hep. C virus cause?

hepatocellular carcinoma

What cancer does the Human herpes virus 8 cause?

Kaposi's sarcoma

What cancer does HTLV -1 cause?

leukemia

What virus causes cervical cancer?

Human papilloma virus

What are possible mechanisms by which viruses can cause cancer?

1. Altered cell regulation
2. carry oncogene into cell and insert into genome
3. insertion of promoters or enhancer next to cellular photo-oncogenes

What happens in altered cell regulation that has the virus cause cancer?

viral proteins bind host cell tumor suppressor proteins

Describe the structure of HPV

nonenveloped icosahedral capsid

How many types of HPV are there?

over 120 known

How does HPV work?

infect keratinocytes of skin or mucous membrane

What is the most common sexually transmitted disease?

Human papilloma virus

What is a featured effect of HPV?

warts: plantars warts, verrucae vulgaris, anogenital codylomata

How is HPV involved in cancer?

cervical cancer. HPV types 16, 18, 31, and 45 can cause. They degrade p53 (the guardian of the cell - causes apoptosis to kill of any bad stuff, now they won't die)

How is non-sexual HPV transmitted?

virus attacks through direct contact (tiny cuts and abrasions), auto-inoculation (nearby skin or infected walking surfaces), prenatal

What is respiratory papillomatosis?

non-sexual HPV through prenatal transmission, warts in the larynx

How is HPV transmitted sexually?

genital infections, hands, shared objects