It took very long for scientists to find out that infections were caused by bacteria because they are microscopic organisms and the knowledge of microbes was still non-existent. This changed with the invention of the Microscope by Hans and Zacharias Janssen in 1590.
Although Hans and Zacharias invented the microscope, microbes were not discovered until Robert Hooke and Antoni Van Leeuwenhoek created it as a scientific instrument.
Antoni Van Leeuwenhoek is credited for having discovered bacteria in 1676.
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