It's important to understand that the vast majority of bacteria are either harmless or beneficial to humans. It's only a small percentage that cause disease. So, instead of asking "how bacteria don't help humans", it's more accurate to ask:

How do some bacteria harm humans?

Here are some ways bacteria can be harmful:

* Disease: Some bacteria are pathogenic, meaning they cause diseases. These diseases can range from mild infections like strep throat to serious conditions like pneumonia, tuberculosis, and food poisoning.

* Spoilage: Bacteria can spoil food by breaking it down and producing toxins, making it unsafe to eat. This leads to food waste and potential foodborne illness.

* Infections: Bacteria can enter the body through wounds, cuts, or other openings, causing infections. These infections can lead to a range of problems, from skin infections to life-threatening sepsis.

* Antibiotic Resistance: Overuse and misuse of antibiotics have led to the emergence of antibiotic-resistant bacteria, making infections harder to treat.

It's crucial to remember that:

* Most bacteria are beneficial or harmless. They play vital roles in our environment, including decomposing organic matter, producing oxygen, and aiding digestion.

* Antibiotics should only be used when prescribed by a doctor to treat bacterial infections.

* Good hygiene practices, such as washing hands frequently and cooking food thoroughly, can help prevent bacterial infections.

By understanding how bacteria can be harmful, we can take steps to protect ourselves and prevent the spread of disease.