Minimum Bactericidal Concentration (MBC) Test

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Introduction of Minimum Bactericidal Concentration (MBC)

Minimum Bactericidal Concentration (MBC) refers to the minimum concentration of an antimicrobial drug that causes a 3-logarithmic decrease (99.9% killing) in the size of the standard inoculum. MBC test has been a powerful method to compare the germ-killing activity of several antimicrobial agents at once, for screening purposes. After a completed Minimum inhibitory Concentration (MIC) test, the MBC can be determined using a series of steps. The MBC is complementary to the MIC, while the MBC demonstrates the lowest level of antimicrobial agent results in microbial death and the MIC test demonstrates the lowest level of antimicrobial agent that inhibits growth.

In general, if the MBC is no more than four times the MIC, the antibacterial agents are regards as bactericidal. Sometimes, the MBC of some drugs is very close to its MIC. And if the MBC of the tested drug against the tested microorganism is ≧ 32 times the MIC, it can be determined that the microorganism has developed resistance to the tested drug.

Summary of The MBC Test

• Overnight culture of the microorganism then dilutes in Mueller Hinton Broth between 1 x 10^5 and 1 x 10^6 cfu/ml.
• Preparation of the test compounds at 2-fold serial dilutions.
• Preparation of the positive and negative control tube or well.
• Incubation of the tubes or microtiter plates at the appropriate temperature and duration and the turbidity indicates the growth of the microorganism
• The dilution corresponds to the MIC and two more concentrated test product dilutions are plated and enumerated to determine viable CFU/ml.

Fig.1 Illustration an example of the 96 well micro plate’s broth microdilution method for two S. pneumoniae strains vancomycin assay.

Weaknesses of The MBC Test:

• For different test microorganisms, an MBC must be determined individually for each microorganism.
• Mueller Hinton Broth is the recommended broth for this method and other media can negatively affect MBC values.
• The antimicrobial concentration to sanitize and disinfect microorganisms cannot be determined by the MBC testing results.

In the current severe situation of microbial diseases and drug resistance, Creative Biolabs is dedicated to the discovery and development of novel antifungal and antibacterial drugs. If you are interested in our services, please do not hesitate to contact us for more details.

Reference

1. Ataee, R.; et al. Determination of vancomycin minimum inhibitory concentration for ceftazidime resistant Streptococcus pneumoniaein Iran. Annals of clinical microbiology and antimicrobials. 2014, 13(1): 1-8.

For Research Use Only.