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Bacterial Diseases

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Bacterial Diseases

Although some bacteria are beneficial for the hosts they inhabit, many bacteria are pathogens that can cause disease in humans. Bacteria are also capable of causing disease in plants too!

What are bacteria?

In this section, we will take a close look at bacteria, including the structure of bacteria, the transmission of bacterial diseases, and the treatment of bacterial infections.

Structure of bacteria

Bacteria are prokaryotic cells. In other words, they do not contain a nucleus, they are very small (relative to eukaryotic cells), and they have few organelles. Make sure you understand the difference between eukaryotic and prokaryotic cells!

To read more on this, please check our article on Cell Structure.

Bacterial cells contain DNA free in their cytoplasm due to their lack of a nucleus. The DNA in bacterial cells can also be arranged in plasmids, which are closed circles of DNA. Bacterial cells also have a cell wall around them.

Bacterial cells are smaller than plant cells or animal cells but are much bigger than viruses. Remember, viruses are neither prokaryotic nor eukaryotic!

Have a look at Figure 1 to see the structure of bacteria.

Transmission of bacteria

Infectious bacterial diseases can spread from one person to another, similar to other pathogens, such as fungi, viruses and protists. Many bacterial diseases spread through unprotected sexual contact or contaminated food or water consumption. Bacteria can also spread through the bodily fluids of an infected person.

Gonorrhoea and salmonella are just two examples of diseases in humans caused by bacteria.

Bacterial infection treatment

When treating bacterial infections, we need to use antibiotics.

Antibiotics are drugs that kill bacteria or stop them from reproducing. While they are effective, some bacteria can build up resistance to these antibiotics. Antibiotic resistance occurs when bacteria turn immune to the actions of the drugs designed to kill them.

This resistance will lead to antibiotics being ineffective against most bacterial infections in the long run. Antibiotic resistance is worrying because it will be harder to treat sick patients.

To prevent bacterial resistance to antibiotics, we need to ensure that we complete prescriptions of antibiotics to ensure all bacteria are killed. We also need to make sure we only use antibiotics to treat diseases that we know have been caused by bacteria rather than viruses or other pathogens. In other words, antibiotics only serve to kill or neutralise bacteria.

Have a look at Figure 2 to see how bacterial resistance develops.

Examples of bacterial diseases

This section will look at two examples of bacterial diseases in animal cells. These are gonorrhoea and salmonella. We'll also look at how bacteria can cause cholera and dental decay.

Cholera

Cholera is a disease caused by the bacteria Vibrio cholerae. Specifically, it is transmitted through the faeces of infected people. However, we don't go around eating other people's faeces, so how does it pass from one person to another? The cholera bacteria can be present in water and food contaminated by a patient's faeces.

The bacteria then release a toxin in the infected person's small intestine that causes chloride ions secretion to the intestinal cavity, which in turn causes an osmotic imbalance: water from the body ends up in the intestines, causing diarrhoea, dehydration and loss of salts. Releasing toxins is a common mechanism by which bacteria cause diseases.

Dental decay

Why do you clean your teeth? Have you ever wondered why your breath smells so bad when you wake up in the morning? Some bacteria live in your mouth and produce acids that chip away at the enamel on your teeth. Those acids are produced through the respiration of sugars by the bacteria.

If dental hygiene is deficient, these bacteria can eventually create holes in the teeth, which are what we know as cavities. Cavities can be filled to prevent the bacteria from working into the tooth. If that happens, it can be really painful. The bacteria that cause tooth decay can also cause gum disease.

Brushing one's teeth can help dislodge food and bacteria from our teeth, making it harder for them to accumulate and generate a lot of acid in one place, thus preventing tooth decay.

Gonorrhoea

Gonorrhoea is a sexually transmitted disease (STD). This means that it is a disease spread via unprotected sexual contact. Gonorrhoea infection can be asymptomatic.

An asymptomatic infection means that the person infected does not display any symptoms.

If the infected person displays symptoms, these could include having a thick green/yellow discharge from the penis or vagina alongside discomfort when urinating.

We can prevent the spread of gonorrhoea by wearing condoms., which act as a mechanical barrier. For more information on the different types of contraception, you can review our Contraception article! We treat gonorrhoea with antibiotics, as with all other bacterial diseases. If gonorrhoea is not treated, it could potentially lead to infertility.

Salmonella

Salmonella is not an STD; instead, it is spread through the consumption of contaminated or undercooked food. In other words, Salmonella causes food poisoning. This bacteria causes nausea, vomiting, abdominal pain and diarrhoea in infected people.

Poultry is vaccinated against this bacteria to prevent the spread of salmonella in the UK. Look at our Vaccination article for more information on how this works. Vaccinating poultry against salmonella makes it much less likely that we will get salmonella when eating poultry.

To prevent the spread of salmonella, we can also ensure that food is cooked thoroughly before eating it. We can make sure that the surfaces that we use to prepare food are cleaned before and after use. Most people recover from a salmonella infection without the need for antibiotics, but antibiotics can be prescribed if necessary.

Bacterial Diseases - Key takeaways

  • Bacteria are prokaryotic cells.
  • Many bacteria cause infection by releasing toxins into the affected organism.
  • Bacterial cells cause infections such as cholera and dental decay in animals.
  • These diseases can be prevented by sterilising food and water and brushing your teeth regularly.

Final Bacterial Diseases Quiz

Question

What are bacteria?

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Answer

Bacteria are prokaryotic cells.

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Question

What is a prokaryotic organism?

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Answer

A prokaryotic organism is an organism that does not contain a nucleus, it also does not have many organelles, and is much smaller than a eukaryotic cell.

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Question

How is gonorrhoea transmitted?


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Answer

Gonorrhoea is transmitted via sexual contact.

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How is salmonella transmitted?

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Answer

Salmonella is transmitted via eating undercooked food or eating food that has been prepared on a contaminated surface.

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 How is gonorrhoea treated?

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Answer

Gonorrhoea is treated using antibiotics. However, many gonorrhoea infections go away on their own without the need for treatment.

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How is salmonella treated?


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Answer

Salmonella is treated using antibiotics.

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Question

Which of the following may cause a green discharge?


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Answer

Salmonella

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Question

Which of the following is true about bacteria?


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Answer

They are prokaryotes

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Question

Which of the following is true about bacterial DNA?


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Answer

It is found in a nucleus

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What does communicable mean?


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Answer

Communicable refers to a disease that can be spread from person to person

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How do bacteria cause disease?


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Answer

Bacteria cause disease by releasing toxins in the affected organism.

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Question

What is salmonella?


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Answer

Salmonella is a bacterial disease that causes food poisoning. It causes symptoms like nausea and dehydration. It is spread by contaminated food, and contaminated food preparation surfaces.

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What is gonorrhoea?


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Answer

Gonorrhoea is a bacterial disease, also described as a sexually transmitted infection.

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What is a pathogen?


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Answer

A pathogen is a microorganism capable of causing harm in other microorganisms.

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What does transmission mean?


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Answer

Transmission refers to the way that pathogens are spread from one person to another.

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