Final answer:
Ciprofloxacin is the synthetic antimicrobial drug among the options given. It is a fully chemically synthesized compound that inhibits the activity of DNA gyrase.
Step-by-step explanation:
Among the antimicrobial drugs listed, ciprofloxacin is the synthetic drug. Penicillin, vancomycin, and erythromycin are all naturally occurring or semi-synthetic antibiotics derived from microbial sources. Ciprofloxacin, however, is a member of the fluoroquinolones, a group of antibiotic compounds that are entirely synthesized through chemical processes. It functions by inhibiting the activity of DNA gyrase, an enzyme essential for replication and transcription in bacteria, making it an effective antimicrobial agent.
Referring to the information provided for reference, nalidixic acid is an antimicrobial that inhibits the activity of DNA gyrase, and it is closely related to fluoroquinolones such as ciprofloxacin. Moreover, while compounds like erythromycin and tetracyclines, including aureomycin and Terramycin, may be semisynthetic, chloramphenicol stands out as being completely synthesized chemically. This supports the classification of ciprofloxacin as a synthetic antimicrobial agent.