Serial Dilution Method

The serial dilution method is one of the most common methods for determining the sensitivity of microorganisms to antibiotics or other antimicrobial drugs. It is based on adding the same dose of microorganisms to a nutrient medium with a certain concentration of the test substance and determining the minimum concentration that does not allow them to grow and reproduce.

To carry out the serial dilution method, it is necessary to use nutrient media containing a certain amount of the test substance. Then, the same number of microorganisms that will be tested for sensitivity are added to each of the media. The media are then placed in an incubator for a specified period of time to allow the microorganisms to begin to grow.

Microbial growth in each medium is then determined. If microorganisms do not grow or grow weakly, then the concentration of the test substance is considered high and does not allow the microorganisms to multiply. If microorganisms grow well, then the concentration of the substance is considered low and allows them to multiply. Thus, using the serial dilution method, it is possible to determine what concentrations of the test substance will be effective in killing microorganisms.

The serial dilution method is widely used in medicine to determine the sensitivity of bacteria to antibiotics. It can also be used to determine the resistance of microorganisms to other antimicrobial substances, such as antiseptics or disinfectants. In addition, the serial dilution method can be used to determine the biological activity of various substances against microorganisms.

Serial dilution method

The method is used to determine the sensitivity (resistance) of microorganisms isolated to antibacterial agents when studying the effectiveness of microbiocenosis (local ecology of microorganisms in medical and food biotechnologies. The essence of the method is the introduction of the same alcohol-tested microorganisms (or tests). The method is based on the false formulation presented below “M - S factor", according to which each substance has a minimum (critical) amount, which is called the minimum inhibitory concentration (MIC), capable of suppressing the growth of some microorganisms, but does not dominate others. To characterize the action of a substance or antibiotic, the concept of minimum inhibitory concentration is used (MIC) as the lowest content (concentration) of the effective ingredient, ensuring the absence of visible colony growth after incubation for 7 days.

According to existing standards, the MIC/MPC should be at least 2 orders of magnitude from the MPC.

Serial dilution (MR) is a key method for microbiological quality control in scientific research and clinical practice. It is used to determine the resistance of microorganisms to drugs or enzymes, as well as to detect the virulence properties of microorganisms. This method can also be used to test the biochemical activity of drugs or enzymes against bacteria and fungi.

The essence of the MR method is that the culture of microorganisms under study is introduced into a nutrient medium in different concentrations of a certain drug and the concentration that stops cell growth is determined. In this way, it is possible to establish the minimum level of active substance required to inhibit growth. Usually to the drug