What is the best agent to use against mycoplasma?

The best agent to use against mycoplasma is tetracycline. Mycoplasma species lack a cell wall, which makes them inherently resistant to antibiotics that target cell wall synthesis, such as penicillin and vancomycin. Tetracycline, on the other hand, works by inhibiting protein synthesis, effectively targeting the ribosomes of mycoplasma and leading to bacterial growth inhibition. This is why tetracycline is widely regarded as an effective treatment for infections caused by mycoplasma.

The other options do not effectively treat mycoplasma infections due to their mechanisms of action or the structural characteristics of mycoplasma.