Micro Question

[Mellifera]

In FA, there are algorithms for bacteria that I plan to memorize. But I was wondering if it was high yield to memorize helical vs. icosahedral, envelope vs. no envelope for viruses? I already know family name, negative/positive strand, single strand/double strand, and RNA/DNA from the school year, but they never even talked about envelopes (other than HIV) and helical vs. icosahedral... so I'm thinking maybe it's not important. Can anyone who has taken the test please chime in? Thanks!

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[Mellifera]

Also, looking thru FA & MMRS I am now confused. Endotoxic shock is mediated by IL-1 & TNF. I thought that is how superantigens such as TSST-1 worked as well, but FA says IFN-gamma & IL-2 are responsible for toxic shock. CMMRS says TNF & IL-1. Which one is correct?

 

[doctorFred]

In FA, there are algorithms for bacteria that I plan to memorize. But I was wondering if it was high yield to memorize helical vs. icosahedral, envelope vs. no envelope for viruses? I already know family name, negative/positive strand, single strand/double strand, and RNA/DNA from the school year, but they never even talked about envelopes (other than HIV) and helical vs. icosahedral... so I'm thinking maybe it's not important. Can anyone who has taken the test please chime in? Thanks!

i don't know how important helical/icosahedral is, but i've seen sample test questions from multiple sources that required knowledge of enveloped vs. naked.

it is, however, extremely easy to remember. the naked DNA viruses are PAP, the naked RNA viruses are PR.
PAP is papiloma, parvo, adeno. PR is reo, picorna. (calic and astro are unlikely to come up on your test, hep e and norwalk.)

 

[opb]

I always thought that the mediators of toxic shock are cytokines such as IL-1 and TNF-alpha. Toxic shock syndrome is mediated in a similar way. These toxins are superantigens that stimulate non-specific release of cytokines which results in shock.

Interferon-gamma and IL-2 sound like the cytokines used for a DTH mediated by TH1 cells. For example, these cytokines are involved granulomatous responses, such as a TB infection.

 

[Mellifera]

Thanks for the replies. I understood TNF & IL-1 to be the mediators as well, but then pg 139 of FA says superantigens "bind directly to MHCII & T-cell receptor simultaneously, activating large numbers of T cells to stimulate release of IFN-gamma & IL-2." I guess IL-2 would make sense because Th cells release it, but what would IFN-gamma have to do with anything? It activates macrophages. I don't ever recall learning that macrophages played a role in toxic shock. I think it must be an error in FA.

 

[thejanitor99]

Also, looking thru FA & MMRS I am now confused. Endotoxic shock is mediated by IL-1 & TNF. I thought that is how superantigens such as TSST-1 worked as well, but FA says IFN-gamma & IL-2 are responsible for toxic shock. CMMRS says TNF & IL-1. Which one is correct?

My impression is this:

Endotoxic shock is mediated by LPS ( not an exotoxin) which causes release of TNF/IL1/NO to cause a high output shock

Superantigens are exotoxins ( not LPS) bind outside the antigen binding site on th TCR receptor and basically activate everything they possibly can via IL2 ( stimulates massive amounts on nonspecific T cells) and IFN-gamma ( stimulates macrophages to kill everything in site)

 

[DrFraud]

My impression is this:

Endotoxic shock is mediated by LPS ( not an exotoxin) which causes release of TNF/IL1/NO to cause a high output shock

Superantigens are exotoxins ( not LPS) bind outside the antigen binding site on th TCR receptor and basically activate everything they possibly can via IL2 ( stimulates massive amounts on nonspecific T cells) and IFN-gamma ( stimulates macrophages to kill everything in site)

Yes, this sounds correct. I also believe that endotoxins come from gram negative infections, and exotoxins are usually from gram + infections.

 

[DrFraud]

In FA, there are algorithms for bacteria that I plan to memorize. But I was wondering if it was high yield to memorize helical vs. icosahedral, envelope vs. no envelope for viruses? I already know family name, negative/positive strand, single strand/double strand, and RNA/DNA from the school year, but they never even talked about envelopes (other than HIV) and helical vs. icosahedral... so I'm thinking maybe it's not important. Can anyone who has taken the test please chime in? Thanks!

I can't think of any occasions where I had to make a selection between any two Micro Organisms based on an envelope or strand of DNA, but here is my general way to group enveloped/non-enveloped viruses. This does not work for every virus, but it's easier to learn the exceptions by glancing through first aid.

Bugs that are generally able to survive in the environment for an extended period of time tend to lack an envelope, and these can be spread via fecal-oral, fomites, etc. Examples include Hep A, Hep E, and andenoviruses.

Bugs that can not live for very long in the environment and that are spread via body fluids or insects tend to have an envelope, like Hep B, C, D, HIV, denge, yellow fever, etc.

This wasn't something that was taught to me, it was just something I figured out while studying, so I don't know how many exceptions there are, but I thought this was an easier way to remember the minutia. Maybe someone else will have something else to add as well.

Hope this helps.

 

[BusterDO]

My impression is this:

Endotoxic shock is mediated by LPS ( not an exotoxin) which causes release of TNF/IL1/NO to cause a high output shock

Superantigens are exotoxins ( not LPS) bind outside the antigen binding site on th TCR receptor and basically activate everything they possibly can via IL2 ( stimulates massive amounts on nonspecific T cells) and IFN-gamma ( stimulates macrophages to kill everything in site)

i agree, the receptor does care about the "what" or the "why", it just responds when activated.

 

[Mellifera]

I can’t think of any occasions where I had to make a selection between any two Micro Organisms based on an envelope or strand of DNA, but here is my general way to group enveloped/non-enveloped viruses. This does not work for every virus, but it's easier to learn the exceptions by glancing through first aid.

Bugs that are generally able to survive in the environment for an extended period of time tend to lack an envelope, and these can be spread via fecal-oral, fomites, etc. Examples include Hep A, Hep E, and andenoviruses.

Bugs that can not live for very long in the environment and that are spread via body fluids or insects tend to have an envelope, like Hep B, C, D, HIV, denge, yellow fever, etc.

This wasn't something that was taught to me, it was just something I figured out while studying, so I don't know how many exceptions there are, but I thought this was an easier way to remember the minutia. Maybe someone else will have something else to add as well.

Hope this helps.

That's an awesome way to remember it - thank you!