Experimental Approach to Determine and Compare the Minimum Bactericidal Concentration and the Minimum Inhibitory Concentration of Maximin 3

Abstract

Antimicrobial peptides (AMPs) are special types of proteins innate in many organisms that have a wide range of inhibitory abilities towards bacteria, fungi, viruses, and parasites. Interests and importance in studying and discovering new antimicrobial substances, including the AMPs, have grown significantly as the threat of antibiotic-resistant bacteria grew. Maximin 3 is an antimicrobial peptide from the Chinese red belly toad, Bombina maxima, and studies show that Maximin 3 has a wide range of inhibitory effects on many bacteria and viruses, including HIV. When studying the inhibitory and bactericidal effectiveness of an antimicrobial substance on a specific type of bacteria, evaluating the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) is crucial. MIC refers to the minimum amount of antimicrobial substances needed to inhibit the growth of the bacteria, and MBC refers to the minimum amount of antimicrobial substances needed to kill the bacteria. Both Maximin 3's and ampicillin's MIC and MBC values for E. Coli were experimentally tested to compare their relative inhibitory and bactericidal effectiveness. MIC was determined by observing any visible inhibition overnight from the antimicrobial substances pipetted into 12-well-plates containing bacteria cultured in liquid media. MBC was determined by observing the overnight bacterial growth on the agar plates when transferring bacteria-containing solutions from the 12-well-plates used to determine the MIC. The literature value of ampicillin's MIC was available for reference, and the experimental result showed that this value was consistent. Studying and understanding the MIC and MBC values may be helpful in determining the right amount of the specific antimicrobial substances needed to treat a specific bacteria to avoid possible intoxication related to the overdose of the antimicrobial substances. Additionally, the understanding of the range of MIC and MBC gaps can further be useful in determining a better treatment option clinically, as a narrower gap between MIC and MBC would indicate a narrower window for possible mutations of the bacteria that can ultimately lead to the development of antibiotic-resistant bacteria.