<P> Thayer - Martin agar (or Thayer - Martin medium) is a Mueller - Hinton agar with 5% chocolate sheep blood and antibiotics . It is used for culturing and primarily isolating pathogenic Neisseria bacteria, including Neisseria gonorrhoeae and Neisseria meningitidis, as the medium inhibits the growth of most other microorganisms . When growing Neisseria meningitidis, one usually starts with a normally sterile body fluid (blood or CSF), so a plain chocolate agar is used . Thayer - Martin agar was initially developed in 1964, with an improved formulation published in 1966 . </P> <P> It usually contains the following combination of antibiotics, called VCN inhibitor </P> <Ul> <Li> Vancomycin, which is able to kill most Gram - positive organisms, although some Gram - positive organisms such as Lactobacillus and Pediococcus are intrinsically resistant </Li> <Li> Colistin, which is added to kill most Gram - negative organisms except Neisseria, although some other Gram - negative organisms such as Legionella are also resistant </Li> <Li> Nystatin, which can kill most fungi </Li> <Li> Trimethoprim, which inhibits Gram - negative organisms, especially swarming Proteus </Li> </Ul>

Sheep blood agar contains an inhibitor to which of the following organisms