Theory

The Minimum Inhibitory Concentration (MIC) is defined as the lowest concentration of an antimicrobial agent, usually expressed in µg/mL or mg/L, that completely inhibits visible growth of a specific bacterial strain under standardised in vitro conditions. MIC determination is a key component of antibiotic susceptibility testing, commonly used in clinical microbiology and pharmaceutical research. The knowledge of MIC is essential for clinicians in order to determine the correct antibiotic concentration for treating infections caused by certain bacterial species. In case of seriously ill patients, who suffer from chronic infections having a history of failed therapies and have been treated with a broad spectrum of antibiotics, a precise effective dosage of antibiotics is required. Among other parameters, MIC is an important one.

MIC has a significant impact on the choice of a therapeutic strategy. The usage of proper dose is also required to reduce the potential side effects that are experienced by the patients. MIC is one of the best ways to prevent antibiotic resistance from developing across bacterial species. The genetically inherited ability of bacteria to resist the inhibitory effects of an antibiotic is known as antibiotic resistance. Instead of growth inhibition, bacteria continue to multiply when they are antibiotic-resistant. This phenomenon develops when too high of an antibiotic dose is prescribed to a patient, or when the infection is not caused by bacteria and an antibiotic is prescribed to the patient.

There are several methods to determine MIC of an antibiotic. These methods includes:

• Broth dilution method
• Antimicrobial gradient method
• Disk diffusion test