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You probably could use a wire loop, but the wooden sticks come with the agglutination kit, so we used them.

Hi Vincent. The use of antibiotics really depend on many factors - mainly host, pathogen, and antimicrobial factors. Host factors are the factors that are attributed to the person or animal that is being infected, such as the species being treated, other conditions or medications they have that could interfere, disease severity, etc. When considering pathogen factors, we need to think about resistance and virulence factors (which can often be attributed to chronicity and severity of infection) the pathogen may have. We can do this by looking at local trends in resistance. For example, in some areas, we've seen widespread resistance to beta-lactams in E. coli. If an E. coli infection was in this area, we might think about using an alternative class due to the resistance that is known. Lastly, antimicrobial factors need to be considered. We need to consider the components of a therapeutic regimen. In humans and animals, we may need to consider various routes of administration or how frequently it can be given. In animals used for food, we need to be conscientious of meat or milk withholding times. As you can see, there are generally a lot of things that go into what makes a drug best, and there isn't a "best" drug for ALL situations; there are just better choices for specific situations over others. The use of antimicrobials should be carefully considered for each individual situation (which is also a big component of antimicrobial stewardship). β-lactams, fluoroquinolones, aminoglycosides and trimethoprim-sulfamethoxazole have all been used to treat E. coli infections in human hospital settings, but it's not a one-size fits all.

Hi! You may want to go back through and re-watch the video. 3-2-1 is correct, and I explained the reasoning behind it.

I think you may be getting the RV tubes a bit confused. The white tube is tetrathionate broth, while the blue tube is Rappaport-Vassiliadis. Post-inoculation, the blue tube just becomes cloudy as seen in the picture.

Hi - these were done for a class that I was teaching. We didn't cover B. cereus in lab, so there will not be a video uploaded for this.

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A machine called a stomacher (also called paddle blenders) has paddles move back and forth that basically help to mix the sample to ensure that the bacteria are mixed throughout the sample. It essentially expels bacteria or other microbes from a solid (i.e., a food product in this case) into the liquid also added to the sample bag.

You likely need to improve your assay and/or ensure you're performing dilutions correctly as each sample is a dilution of the previous one and your results should be reflective of that. If you're getting higher numbers of positive samples on the 3rd and 4th dilutions than you are with the 1st and 2nd, there's likely an issue somewhere else.

I don't work with them a ton, but in my experience, the amount of agglutination you get is usually related to how much of the organism is included. In this case, we didn't have a lot of sample, which could be why the degree of agglutination wasn't as pronounced.