Minimum Inhibitory (MIC) and Minimum Bactericidal Concentration (MBC) Evaluations as R&D Tools
- Posted by Mark Goins
- On March 14, 2017
- antimicrobial efficacy, antiseptic, laboratory, microbiology
The Minimum Inhibitory Concentration (MIC) is defined as the lowest concentration of an antimicrobial ingredient or agent that is bacteriostatic (prevents the visible growth of bacteria). MICs are used to evaluate the antimicrobial efficacy of various compounds by measuring the effect of decreasing concentrations of antibiotic/antiseptic over a defined period in terms of inhibition of microbial population growth. These evaluations can be quite useful during the R&D phase of a product to determine appropriate concentrations required in the final product, as the concentration of drug required to produce the effect is normally several hundred to thousands of times less than the concentration found in the finished dosage form.
Various concentrations of the compounds are inoculated with cultured bacteria, and the results are measured using agar dilution or broth dilution (macro or micro) to determine at what level the MIC endpoint is established. Susceptibility testing is typically conducted using organisms that contribute to an infectious process warranting antimicrobial chemotherapy. A commonly used cocktail of bacteria is known as the ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species). The ESKAPE pathogens are considered the leading cause of nosocomial (hospital-related) infections and are known to be resistant to antimicrobial products. Other organisms such as aerobic or anaerobic bacteria, yeasts, or filamentous fungi, either alone or in multiple combinations can also be utilized. The FDA Tentative Final Monograph (TFM- section 333.470, page 31444) also provides guidance on organisms to use to determine the efficacy of products such as antiseptic handwash, healthcare personnel handwash, patient preoperative skin preparations, and surgical hand scrubs.
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Various concentrations of the compounds are inoculated with cultured bacteria, and the results are measured using agar dilution or broth dilution (macro or micro) to determine at what level the MIC endpoint is established. Susceptibility testing is typically conducted using organisms that contribute to an infectious process warranting antimicrobial chemotherapy. A commonly used cocktail of bacteria is known as the ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species). The ESKAPE pathogens are considered the leading cause of nosocomial (hospital-related) infections and are known to be resistant to antimicrobial products. Other organisms such as aerobic or anaerobic bacteria, yeasts, or filamentous fungi, either alone or in multiple combinations can also be utilized. The FDA Tentative Final Monograph (TFM- section 333.470, page 31444) also provides guidance on organisms to use to determine the efficacy of products such as antiseptic handwash, healthcare personnel handwash, patient preoperative skin preparations, and surgical hand scrubs.
(more…)