Which person is not regarded as one of the three main founders of bacteriology?

Louis Pasteur (December 27, 1822 – September 28, 1895) was a French chemist and microbiologist renowned for his discoveries of the principles of vaccination, microbial fermentation and pasteurization. He is regarded as one of the three main founders of bacteriology, together with Ferdinand Cohn and Robert Koch.

Ferdinand Julius Cohn (January 24, 1828 – June 25, 1898) was a German biologist who is regarded as one of the founders of modern bacteriology. His classification of bacteria into four groups based on shape (sphericals, short rods, threads, and spirals) is still in use today.

Robert Heinrich Hermann Koch (December 11, 1843 – May 27, 1910) was a celebrated German physician and pioneering microbiologist. As one of the founders of modern bacteriology, he is known for his role in identifying the specific causative agents of tuberculosis, cholera, and anthrax and for giving experimental support for the concept of infectious disease.

Derek Christopher Shepherd, M.D., also referred to as "McDreamy", is a fictional surgeon from the ABC medical drama Grey's Anatomy, portrayed by actor Patrick Dempsey.