What are bacterial infections?

Bacteria are tiny, single-celled organisms found inside and outside the body. Some types of bacteria can cause infections. Other types aren't harmful, and live on your skin or in your gut, help with digestion and support your overall health.

Bacterial infections can affect many parts of your body, including your:

• throat
• lungs
• skin
• bowel

Severe bacterial infections can be dangerous, especially for people with a weaker immune system or if the bacteria are resistant to treatment.

Other causes of infectious diseases include viruses, parasites and fungi.

Illnesses caused by bacterial infections

Bacteria can cause a range of infections and illnesses, for example:

• Legionnaires' disease
• meningococcal disease
• Q fever
• strep throat
• tuberculosis (TB)
• whooping cough (pertussis)

What are the symptoms of a bacterial infection?

The symptoms of a bacterial infection depend on where the infection is in your body and the type of bacteria. Common symptoms of bacterial infection include:

• fever
• feeling tired or unwell
• headache or muscle aches
• skin changes or rashes
• diarrhoea or vomiting
• wet cough or sore throat

What causes bacterial infections?

Bacterial infections happen when harmful bacteria enter your body and increase in number (multiply). They may also occur when bacteria that usually live on your skin or inside your body start to multiply uncontrollably, causing an infection.

Bacteria can enter your body through:

• a wound, cut or bite that breaks the skin
• eating or drinking contaminated food or water
• breathing in droplets from an infected person (for example, those released after they cough, sneeze or breathe nearby)
• touching contaminated surfaces and then touching your eyes, nose or mouth

Bacteria can also be transmitted by contact with infected blood or other bodily fluids.

Bacterial infections and weather events

Floods or environmental disruptions can bring harmful bacteria from soil to the surface. Flood water can come from weather events such as storms or cyclones.

Touching items affected by flooding can also increase your risk of bacterial infection. If you are in an area affected by flooding, avoid contact with flood water or any contaminated water and practice good hand hygiene. Wash your hands with soap and clean water. If soap and clean water isn't available, use hand sanitiser.

When should I see my doctor?

You should see your doctor if you have signs of a bacterial infection. Signs may depend on the type of bacteria and the part of your body that is infected.

Untreated bacterial infections can sometimes lead to serious, life-threatening conditions such as sepsis — a severe immune reaction to infection.

Learn more about sepsis.

How are bacterial infections diagnosed?

Your doctor will ask about your symptoms and general health.

If your doctor suspects a bacterial infection, they can refer you for testing to confirm the diagnosis and identify the type of bacteria or virus causing your illness. Body fluids that are commonly sent for testing include blood, saliva, urine and stool (poo).

There are a range of methods used to identify bacteria or viruses in samples:

• In a cell culture, the sample is kept in a laboratory and monitored to see if any bacteria grow. This is accurate but can take a few days.
• PCR testing finds bacteria by looking for their DNA (genetic material in the sample). PCR is fast but works best if your doctor already suspects a specific type of bacteria.
• Next-generation sequencing (NGS) is an advanced test that find any bacteria in a sample, even when your doctor doesn't suspect a specific type.
• Point-of-care (POC) tests are rapid tests designed to give immediate results.

Knowing the exact cause of your illness can help your doctor recommend the best treatment and avoid unnecessary antibiotic use, which can lead to antibiotic resistance.

How are bacterial infections treated?

Serious bacterial infections can be effectively treated with antibiotics. These medicines either kill the bacteria or stop them multiplying. This helps your body's immune system fight the bacteria.

Antibiotic resistance makes antibiotics less effective over time, so it's important to only take antibiotics as directed by your doctor or pharmacist.

Learn more about antibiotic resistance.

What are the complications of bacterial infections?

Untreated bacterial infections can lead to serious problems. For example, an untreated, infected cut can cause cellulitis, a spreading skin infection.

Untreated bacterial infections can sometimes lead to serious, life-threatening conditions.

• Septicaemia is a serious blood infection. It is when bacteria enter the bloodstream and cause blood poisoning.
• Sepsis is when the body damages its own tissues in response to a bad infection. Sepsis can cause shock, organ failure and death, if it's not treated quickly.

Can bacterial infections be prevented?

Bacterial infections can be contagious. Bacterial infections are spread between people through:

• coughing
• sneezing
• contact with infected skin or body fluids
• unprotected sex or sharing dirty needles

You can reduce the spread of infections by:

• washing your hands properly
• washing fruits and vegetables before eating them
• cooking food properly
• having safe sex
• not sharing needles

Resources and support

• Download the app Could this be sepsis? from the Australian Sepsis Network (ASN) to check your symptoms.
• The Australian Government has information about how you can reduce antibiotic resistance.
• The University of Queensland Australia has information about the difference between bacteria and viruses.

You can also call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available to speak with 24 hours a day, 7 days a week.

Do you prefer to read in languages other than English?

Health Translations offers information about antibiotic resistance in several languages.