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 Free Bacteriology Videos  




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  #1

I am creating and hosting free medical education videos on my Facebook page and YouTube channel which medical students might find useful. Videos covering the Basic Sciences and final year subjects will be uploaded and over the next few months we will be adding hundreds of more free videos.

The videos are available at www.facebook.com/mededuco and on YouTube. Just to add the videos are licensed under creative commons license rather than the standard YouTube license and are not monetised for advertisements on YouTube. Therefore, students will not be subjected to YouTube advertisements .Reference materials of peer reviewed journal papers related to the videos are provided for each video in the notes section on YouTube.

Here is an example of one the videos: www.youtube.com/watch?v=ra...qQZSSs7GBYJDFJvRZO&index=2




  #2

I just watched a couple of the videos, particularly the ones about gram staining and media.

Heat fixing of Gram stains works nicely. However, when we make smears directly from patient specimens (swabs, tissues, fluids), we let the inoculum dry and then flood the slide with methanol. This will fix the organisms to the slide without the distortion that can occur to white cells and other cells on the slide that can happen with heating. You can also flood the slide with the same acetone/alcohol you use for decolorizing, and this works quite nicely also. One of the labs I worked at for years used this method routinely.

Some of the media mentioned are not media that we use anymore in day-to-day clinical microbiology laboratories. Mannitol Salt seems to show up in college labs, but I have not seen it in actual use in a hospital micro lab ever, and I've been in the field for 40 years in the U.S. The media mentioned for growing Legionella bacteria is accurate, but there is currently a fifteen minute rapid test done on the patient's urine for Legionella antigen. The organism takes around five days to grow on the agar, and most labs do not stock it routinely, especially since the antigen testing is available. The antigen test is much more practical to screen patients for this disease.

The most commonly used agar in the clinical microbiology lab is Trypticase Soy Agar with 5% sheep blood (BAP), which is not mentioned in the video at all. Some places, particularly Australia, I believe, use horse blood. The hemolysis differs a bit between the two types of blood. Virtually every specimen plated in the micro lab gets inoculated onto BAP.

Thayer Martin not only can screen for Neisseria meningitidis, but also, and much more commonly in the US, Neisseria gonorrhoeae. Many labs are using PCR methodology to screen for GC and Chlamydia nowadays, so we don't see it growing on cultures nearly as often as in years past.

Hektoen does screen for Salmonella and Shigella. However, other non-pathogens will grow on this medium. Some species of Citrobacter produce H2S and this will grow quite nicely on HE, as will Proteus, and it also produces H2S. Any "suspicious" colony on HE needs to be screened. If it does turn out to be Salmonella or Shigella, serotyping is performed. If positive, the physician is notified and reporting to proper department of health agencies is begun. There are other stool media available for screening for enteric pathogens. MacConkey-Sorbitol agar uses Sorbitol instead of lactose. E. coli O157:H7 does not ferment sorbitol but can be lactose positive, so we look for non-sorbitol fermenting colonies on this agar to screen. We also use a special plate to screen for Campylobacter, which must be in a microaerophilic atmosphere at 42 degrees C for 2 days to grow, as it will not grow on conventional media in conventional atmospheric conditions and temperature.

I am obviously looking at these videos from a medical technologist's point of view. As most of you on these boards are medical students, you will be looking at them differently. I think they are worth viewing for the disease information. They are a bit short on the actual work-a-day information that I would need for what I do.





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