The cholera causing germ Vibrio cholerae was first discovered and described by which scientist?

Introduction / Context:
Cholera is a serious water borne disease, and understanding who first discovered its causative germ is an important part of medical history. The bacterium responsible, Vibrio cholerae, was first correctly observed and described by Italian scientist Filippo Pacini in the nineteenth century. This question checks whether you can pick Pacini from a list that also includes other famous medical scientists such as Robert Koch.

Given Data / Assumptions:
• The focus is on the scientist who discovered the cholera causing germ.
• Options are Filippo Pacini, Robert Koch, M. Laveran, and Felix Hoffman.
• We assume that the exam follows the increasingly common convention of crediting Pacini with the first correct identification of the bacterium, even though Koch also studied it later.

Concept / Approach:
The correct approach is to recognise the difference between first discovery and later confirmation or popularisation. Filippo Pacini observed the comma shaped bacteria in cholera patients and described them in detail. Robert Koch later investigated cholera as well, but Pacini's earlier work gives him priority as the discoverer in many exam oriented resources. Laveran is associated with the malaria parasite, and Felix Hoffman with synthesising aspirin. So only Pacini fits the exact wording of the question.

Step-by-Step Solution:
Step 1: Note that the question asks who discovered the cholera causing germ, not who later confirmed it.
Step 2: Recall that Italian scientist Filippo Pacini observed Vibrio cholerae in the mid nineteenth century and linked it to cholera cases.
Step 3: Understand that Robert Koch also studied cholera and confirmed the role of the bacterium but came later in time.
Step 4: Recognise that M. Laveran is famous for discovering the malaria parasite and not the cholera organism.
Step 5: Remember that Felix Hoffman is best known for developing aspirin, which has no direct connection with cholera germs.

Verification / Alternative check:
To verify, think of how many exam guides and general knowledge books phrase this fact. They often state that the cholera causing germ was discovered by Filippo Pacini and later confirmed by Robert Koch. Some sources may emphasise Koch for his broader contributions to bacteriology, but when the exact wording is discovered the germ, Pacini is usually the correct choice. Checking standard biology exam compilations supports this interpretation.

Why Other Options Are Wrong:
Robert Koch, although a very important bacteriologist, is not usually given priority as the first discoverer of the cholera germ in modern exam keys. M. Laveran discovered the malaria parasite in blood and therefore does not match cholera. Felix Hoffman synthesised acetylsalicylic acid, known as aspirin, which is unrelated to cholera. Therefore, these three options do not match the specific requirement of the question.

Common Pitfalls:
A common pitfall is to choose Robert Koch because his name appears frequently in discussions of disease causing bacteria. Students who only have partial knowledge may remember Koch but not Pacini. To avoid this, it helps to memorise a small table pairing Pacini with cholera germ and Koch with tuberculosis and general bacteriology methods. This clear mapping prevents confusion when both names appear together in multiple choice questions.

Final Answer:
The cholera causing germ was first discovered by Filippo Pacini.