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Thread: What type microscopes r used to identify pathogenic bacteria

  1. #1 What type microscopes r used to identify pathogenic bacteria 
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    I would enjoy a link that shows the different ways bacteria are identified and by what means they are viewed if anyone knows of one. I have failed in finding one.

    Otherwise personal knowledge will be appreciated.

    Thanks.


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    Forum Cosmic Wizard i_feel_tiredsleepy's Avatar
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    You don't usually use a microscope to identify the bacteria, you use a microscope to identify the presence of bacteria in urine, blood, or other fluids. You'd have to perform a culture and then do either PCR or ELISA to identify the species. PCR is the much preferred method. In the old days they used to use a slew of biochemical assays that have become outdated, involving agar plates, diverse dyes, microscopic techniques, but these are mostly outdated now that we can use PCR, with the primers usually provided in pre-packaged kits.

    For a few common pathogens, like Streptoccocus pyogenes in throat infections, there are pre-existent test kits, usually functioning off of some sort of antibody marker.

    As for identifying the presence of a bacterial pathogen, a light microscope is used.


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    Is it due to difficulty in keeping the bacteria specimen viable for viewing under a microscope or is it due to the difficulty in microscopes detecting the bacteria because of the size of the bacteria being too small to view?

    There has to be a reason why people don't just point at the bacteria and say, yep that's a streptoccocus pyogenes if I ever seen one.
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    Forum Cosmic Wizard i_feel_tiredsleepy's Avatar
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    It's because pathogenic bacteria generally come in two shapes, rod and cocci. As do most benign bacteria, though you don't usually find those in blood or urine.

    Salmonella entereditis and Salmonella typhii, for example, are indistinguishable under a microscope, it's only with biochemical assays or DNA that you can identify them. They do make some interesting intestinal bacteria biochemical kits, I forget what they're called, you essentially run a rod through a tube of different growth media and then you can read the results in a day to identify the bacteria. There are fancier methods around now though.

    That's not to say you can't tell some bacteria apart by microscopy, it's just not the best way to identify all species.



    If you had a mixed population of these three bacteria (2 of the 3 are pathogens, S. mutans causes cavities), you would have a hard time telling that under a microscope. And you have to culture the bacteria to be able to get enough to get this nice of an image. Although, we have quick throat swab kits that can test for S. pyogenes in 10 minutes, it's just much easier not to use microscopy for identifying the species.

    Intestinal pathogens tend to be near impossible to tell apart by microscopy.

    What microscopy is useful for in diagnostics is to identify the presence of pathogens, taking a pretty good early guess at what some pathogen is in some cases, and sometimes seeing how bad an infection is. A couple E. coli in the urine is different than a whole bunch of E. coli and some blood in urine.
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    "I almost went to bed
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  6. #5  
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    Thanks, that pretty much answered my question.
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