05/10/2025
Bacteria are single-celled microorganisms that can exist in a variety of environments, from soil and water to inside the human body. They are microscopic, meaning they can't be seen without a microscope. Bacteria come in many shapes, such as spheres (cocci), rods (bacilli), and spirals (spirilla). While many bacteria are harmless and even beneficial (like those in our gut helping with digestion), some can cause infections.
When bacteria infect humans, they can cause illness by:
Releasing Toxins: Some bacteria produce harmful chemicals called toxins that can damage tissues or organs. For example, Clostridium botulinum produces botulinum toxin, which can cause botulism.
Invading Tissue: Some bacteria invade and multiply inside human tissues, causing inflammation and damage. This can lead to conditions like pneumonia (lungs infected by bacteria) or cellulitis (skin infection).
Compromising the Immune System: Certain bacteria can suppress or evade the immune system, allowing them to spread and cause disease. For example, Mycobacterium tuberculosis (the cause of tuberculosis) can persist in the lungs and avoid being destroyed by the immune system.
Infections caused by bacteria in humans can range from mild to severe, depending on the type of bacteria, the part of the body affected, and the immune systemโs response. Some common bacterial infections include:
Strep throat (caused by Streptococcus bacteria)
Tuberculosis (caused by Mycobacterium tuberculosis)
Urinary tract infections (UTIs) (often caused by Escherichia coli, or E. coli)
Pneumonia (can be caused by Streptococcus pneumoniae, among others)
Bacterial infections are typically treated with antibiotics, but not all bacteria are susceptible to all antibiotics. This has led to concerns about antibiotic resistance, where bacteria evolve to become immune to certain drugs.