Identifying Bacteria Causing Human Disease

The question asks to identify which organism among the given options is a bacterium that causes disease in the human body. To answer this, we need to examine each option and determine its type and the disease it causes.

Analyzing the Options for Pathogens

Let's look at each option provided:

• Varicella zoster: This is a type of virus. It is known to cause chickenpox, primarily in children, and shingles (herpes zoster) later in life in individuals who have previously had chickenpox.
• Trypanosoma gambiense: This is a type of protozoan parasite. It is one of the main causes of Human African Trypanosomiasis, also known as sleeping sickness, which is transmitted by the tsetse fly.
• Salmonella typhi: This is a type of bacterium. It is the causative agent of typhoid fever, a serious infectious disease spread through contaminated food and water.
• Plasmodium falciparum: This is a type of protozoan parasite. It is one of the species that causes malaria in humans, transmitted by the bite of infected female Anopheles mosquitoes.

Determining the Bacterium

From the analysis above, we can see the types of microorganisms represented by each option:

• Varicella zoster: Virus
• Trypanosoma gambiense: Protozoan parasite
• Salmonella typhi: Bacterium
• Plasmodium falciparum: Protozoan parasite

The question specifically asks for a bacterium that causes disease in the human body. Out of the given options, only Salmonella typhi is classified as a bacterium.

Disease Caused by Salmonella Typhi

Salmonella typhi causes typhoid fever. This is a significant disease affecting humans, characterized by high fever, weakness, stomach pain, headache, and sometimes a rash. It is spread via the fecal-oral route, often through contaminated food or water.

Conclusion

Based on the classification of each organism and the diseases they cause, Salmonella typhi is the only option that is a bacterium and causes disease in the human body (typhoid fever).

Revision Table: Key Pathogens & Diseases

Additional Information: Understanding Different Pathogen Types

Pathogens are microorganisms that can cause disease. They come in various forms, each with unique characteristics:

• Bacteria: These are prokaryotic organisms, meaning their cells lack a nucleus and other membrane-bound organelles. They reproduce asexually, usually by binary fission. While many bacteria are harmless or even beneficial, some are pathogenic, causing diseases like strep throat, tuberculosis, and typhoid fever (caused by Salmonella typhi).
• Viruses: Viruses are much smaller than bacteria and are not considered living organisms because they cannot reproduce or carry out metabolic processes outside of a host cell. They infect cells and hijack their machinery to make more viruses, causing diseases such as the common cold, flu, COVID-19, and chickenpox (caused by Varicella zoster).
• Parasites: Parasites are organisms that live in or on a host organism and get their food from or at the expense of their host. Protozoa are single-celled eukaryotic parasites, which can cause diseases like malaria (caused by Plasmodium falciparum) and sleeping sickness (caused by Trypanosoma gambiense). Other parasites include worms (helminths) and external parasites like ticks.

Understanding the difference between these types of pathogens is crucial for diagnosing and treating infectious diseases effectively.