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Flashcards in HD3: Natural history of infection Deck (75)
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Koch's postulates:

The microorganism must be found in abundance in all organisms suffering from the disease, but should not be found in healthy organisms.
The microorganism must be isolated from a diseased organism and grown in pure culture.
The cultured microorganism should cause disease when introduced into a healthy organism.
The microorganism must be reisolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent.


What's the biggest change between the old and current koch's postulates?

nucleic acid sequence presence is looked at instead pathogen presence thanks to development of PCR


What are the modern Koch's postulates:

A nucleic acid sequence belonging to a putative pathogen should be present in most cases of an infectious disease. Microbial nucleic acids should be found preferentially in diseased organs known, and fewer/not in those organs that lack pathology.
With resolution of disease, the copy number of pathogen-associated nucleic acid sequences should decrease or become undetectable. With clinical relapse, the opposite should occur.
Where sequence detection predates disease, copy number correlates with severity of disease or pathology, there is more likely to be a causal relationship.
The nature of the microorganism should be consistent with the known biological characteristics of that group of organisms.
These sequence-based forms of evidence for microbial causation should be reproducible.


What's the difference between primmary and opportunistic pathogens?

Primary Pathogens
Cause disease in non-immunocompromised host

Opportunistic: Often commonly found pathogens. Only cause infection in damaged host


Give examples of what may allow an opporunistic pathogen infection?

Immunosupressed- chemotherapy, age, alcohol, infection (e.g. HIV, TB),diet.
Tissue damage- trauma, burns, radiation.
Catheter infections
Genetic defects
Change in host bacteria e.g. antibiotics, diet


What 3 things do primmary pathogens do to a healthy host cause disease?

Intrinsic virulence
Toxin production
Induction of abnormal host response


What is cellulitis?

Cellulitis (sel-u-LIE-tis) is a common, potentially serious bacterial skin infection. The affected skin appears swollen and red and is typically painful and warm to the touch. Cellulitis usually affects the skin on the lower legs, but it can occur in the face, arms and other areas


Droplet e.g. Influenza, rhinovirus, TB
Sexually e.g. HIV, syphillis
Blood- e.g. HBV, HIV, HCV.
Bites- anaerobic infection, HBV, Rabies
Give 3 further modes of transmission:

Feacal-oral e.g. salmonella, noravirus
Enviromental e.g. C.difficile,strongyloides, enterovirus
Vector bourne through lice, ticks, fleas, sandfly, mosquitos, tsetse fly.


What is the term used to describe that bacteria are able to regulate gene transcription and thus phenotype based upon their enviroment/medium (population density around them). The bacteria must possess three characteristics: to secrete a signaling molecule, an autoinducer, to detect the change in concentration of signaling molecules, and to regulate gene transcription as a response.[2] This process is highly dependent on the diffusion mechanism of the signaling molecules. QS Signaling molecules are usually secreted at a low level by individual bacteria. At low cell density, the molecules may just diffuse away. At high cell density, the local concentration of signaling molecules may exceed its threshold level, and trigger changes in gene expressions

quorum sensing


What are the 2 methods bacteria attach to host:

adherence though bacteria adhesions and host receptors
biofils (attachment and intracellular adhesions)


One example f adhesins interacting with host receptor is: interacting in fimbria salmonella.
what adhesin does HIV use to target CD4 T cells?
2) what are the major cellular targets for HIV-1?
3) where are they found?

CD4 with gp120 HIV protein
2) CD4 lymphoctyes (GI tract and other tissues, 1% in circulation) and macrophages (all tissues and lymphatic system)


What can make pathogens more virulent:

Ability to replicate within the host
Toxin production-
Cell death-
Survival with eukaryocytic cells.


How can cell death make pathogen's virulent

HIV and CD4 cells, apoptosis, direct toxicity on cells by pathogen (HCV) or immune system (HBV


What are the 2 ways toxins can be encoded? give 2 examples of each toxin:

Plasmid encoded- TSST, Tetanus neurotoxin
Phage encoded- Cholera Toxin, diptheria toxin.


what is a granuloma:

A granuloma is a structure formed during inflammation that is found in many diseases. It is a collection of immune cells known as macrophages.


What are the 3 types of immune invasion:

passive, active, aggressive


give 3 characteristics of passive immune evasion:

Latency e.g. herpes, Malaria
Can hide in sanctuary sites
Resistance to phagocytosis and destruction by lysosymes


give 3 characteristics of active immune evasion:

Production of immunomodulatory proteins


give 3 characteristics of aggressive immune evasion:

Counterattack on immune system e.g. HIV


a) pro or eu -karyotic?
b) single or multi cellular?
c) organelles membrane or non-membrane bound?
d) sexual or asexual reproduction (+term given)

1) pro
b) pro
c) non-mem
d) asexual (binary fission)


gram negative are purple or pink?



gram positive are purpleor pink?



According to class 1 of the baltimore classification system, what form doe the virus store its genetic material + 1 e.g.:

dsDNA - mRNA (herpes)


According to class 2 of the baltimore classification system, what form doe the virus store its genetic material + 1 e.g.:

ssDNA -dsDNA -mRNA (parvovirus)


According to class 3 of the baltimore classification system, what form doe the virus store its genetic material + 1 e.g.:

dsRNA- mRNA (rotavirus)


According to class 4 of the baltimore classification system, what form doe the virus store its genetic material + 1 e.g.:

(+) ssRNA- (-)ssRNA- mRNA
(hepatitisi C virus)


According to class 5 of the baltimore classification system, what form doe the virus store its genetic material + 1 e.g.:

(-)ssRNA- mRNA


According to class 6 of the baltimore classification system, what form doe the virus store its genetic material + 1 e.g.:

(+)ssRNA- DNA/RNA hybrid- dsDNA- mRNA


According to class 7 of the baltimore classification system, what form doe the virus store its genetic material + 1 e.g.:

dsDNA- ssRNA- mRNA


Fungal infections
1) eukaryotes or pro?
2) how do yeasts replicate?
3) ow do moulds replicate?
4) which method of replication is asexual?
5)what is the role of septae in fungus?
6) single or multicellular?

1) eukaryotes
2) mitosis
3) meiosis
4) mitosis is sexual, meiosis is asexual
5) septae is the cell membrane, it divides what would be a multinuclear fungus into many cells, it is relatively fluid
6) both