M4 contains vancomycin, amphotericin B, and colistin and is suitable for transport of viruses, chlamydiae, Mycoplasma and Ureaplasma. The M4RT contains gentamicin and amphotericin B and is only suitable for transport of viruses and chlamydiae. M5 is similar to the M4, but it does not contain gelatin. M5 is suitable for transport of viruses, chlamydiae, Mycoplasma and Ureaplasma.