Hello everyone! This week in the laboratory component of this course we completed antibiotic susceptibility testing on various organisms. I am going to review and summarize the principle of one of the tests performed in the laboratory in order to help everyone have a firmer grasp of the underlying concepts behind the test we performed. How you all find this helpful!
Microdilution Method
The basic principle behind the tube broth dilution method and the microdilution method are the same. In both, two fold dilutions of antimicrobics are tested against a standardized concentration of an organism being tested. The lowest concentration of a drug that will inhibit the growth of a organism is determined (this is the MIC, or minimal inhibitory concentration) by this method. The microdilution method utilizes bacterial broth volumes of 0.05-0.1 ml and microtiter trays with dilutions of antimicrobics dehydrated or frozen in the wells. A standardized suspension of a organism is prepared and poured into a seed tray. A special inoculator device (we used the Renok inoculator device) is used to draw up the broth and dispense a specific amount in each microtiter well. The trays are then incubated in a regular incubator. The results are read after 16-20 hours. Bacterial growth is determined by observing the bottom of the well with a mirror and looking for turbidity. Turbidity indicates growth and clear solution indicates no growth. The MIC can then be determined by observing the amount of drug in the last clear well, going from highest concentration of antimicrobial to the lowest concentration of antimicrobial.
I was interested in finding an article concerning drug-resistant bacteria, so I found this interesting article and video concerning MRSA found on bedbugs! Hope you enjoy it!http://abcnews.go.com/Health/Wellness/bedbugs-carry-drug-resistant-bacteria-study/story?id=13571434
Thank you for the review of the microdillution method. In our infectious disease class one of the last topics we discussed was antimicrobial susceptibility testing, but this topic is certainly not a small one. The ultimate goal of identifying and isolating the disease causing bacteria in a patient is to know how to appropriately treat the patient and agent of disease. The antimicrobial suscpetibility testing allows a physician to prescribe the correct antibiotics for treatment.
ReplyDeleteVery interesting link with video. I had heard about this and have been worried when traveling just because of bedbugs in general. When I was in Atlanta last week, I noticed a big billboard warning about bedbugs (I think it was advertizing something to kill them). The funny thing was that it was right in front of the Holiday Inn!!
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