Broth microdilution is a laboratory technique used to determine the minimum inhibitory concentration (MIC) of antimicrobial agents against specific microorganisms. In this method, a series of test tubes or wells containing a liquid growth medium are prepared, each with a different concentration of the antimicrobial agent. The microorganisms are then added to these dilutions, allowing researchers to observe the lowest concentration that effectively inhibits growth. This technique is commonly used in microbiology to assess the effectiveness of antibiotics, such as penicillin or ciprofloxacin, against bacteria like Escherichia coli or Staphylococcus aureus. By identifying the MIC, healthcare professionals can make informed decisions about treatment options for infections.