Bacterial throat infection: how to recognise it and what to do

That scratchy, painful feeling in your throat can be hard to ignore, especially when you are not sure what is causing it. Is it just a common cold, or something that needs treatment? While most sore throats are harmless, some, like strep throat, require a different approach. Understanding the difference can help you decide what to do next.

Table of Contents

• What is a throat infection and what causes it?

• Sore throat or strep throat?

• Symptoms of a bacterial throat infection (strep throat)

• Which bacteria causes a throat infection?

• What happens if a bacterial throat infection is left untreated?

• Treatment: do you always need antibiotics?

• Testing for a bacterial throat infection at home

• When should you see a GP about a sore throat?

• Frequently asked questions about bacterial throat infections

What is a throat infection and what causes it?

A sore throat, or pharyngitis, is a scratchy or painful sensation in the back of the throat (pharynx). It occurs when the lining of the throat (the mucosa) becomes inflamed. It is commonly associated with pain when swallowing or speaking, redness, and sometimes swollen lymph nodes in the neck. In most cases, pharyngitis is caused by an infection, most often viral and sometimes bacterial, although it can have other causes as well. Distinguishing between these causes is important, as it determines the most appropriate treatment.

Most throat infections are viral and resolve on their own within a few days. Bacterial infections are less common but important to recognise. In particular, infections caused by group A Streptococcus (bacteria) (strep throat), as well as bacterial sinus infections, can lead to complications if left untreated.

Source: Cleveland Clinic, 2024; Cleveland Clinic, 2022

Sore throat or strep throat?

As mentioned earlier, strep throat (streptococcal infection), is a less common cause of a sore throat. Understanding the difference between these two infections can help you assess your symptoms and the right treatment:

Sore throat (usually viral)

• Most often caused by viruses (such as a cold or flu)

• Develops gradually

• Pain is usually mild to moderate, often scratchy or irritating

• Commonly comes with:

• Runny nose

• Cough

• Sneezing

• Red, watery eyes

• Mild body aches

• Relieve symptoms with rest, fluid and over the counter pain relievers. Typically clears up on its own within 5-7 days

Strep throat (bacterial)

• Caused by group A Streptococcus bacteria

• Comes on suddenly

• Pain is often severe, especially when swallowing

• Commonly comes with:

• Fever

• Swollen, tender lymph nodes

• Headache

• Loss of appetite

• Belly pain, especially in children

• Usually no cough or runny nose

• Tonsils may be red, swollen, with white patches or pus

• May require antibiotics to prevent complications

Source: Cleveland Clinic, 2025 

Symptoms of a bacterial throat infection (strep throat)

The following symptoms may indicate a bacterial throat infection (strep throat):

• Sudden sore throat

• Rapid onset of fever (often highest on the second day)

• Severe throat pain

• Pain when swallowing

• Red, sore, and swollen throat

• Red and swollen tonsils

• White patches, spots, or streaks of pus on the tonsils or throat

• Tiny red spots on the roof of the mouth (petechiae)

• Swollen and tender lymph nodes in the neck

• Chills

• Headache

• Loss of appetite

• Abdominal (stomach) pain

• Nausea and vomiting

• Rash (scarlet fever), often starting on the neck and chest and possibly spreading

• Rash that may feel rough, like sandpaper

Typically not present:

• Cough

• Runny nose or other cold-like symptoms

Source: Cleveland Clinic, 2022

Which bacteria causes a throat infection?

While most throat infections are caused by viruses, bacterial causes are clinically important to recognise. The most common bacterial cause is Streptococcus pyogenes, also known as group A β-hemolytic Streptococcus or Streptococcus pyogenes (group A strep). This is the bacterium responsible for strep throat.

Although less common, other bacteria can also cause throat infections. These include group C and G streptococci, Neisseria gonorrhoeae, Chlamydia trachomatis, Treponema pallidum, Arcanobacterium haemolyticum, Fusobacterium necrophorum, Mycoplasma pneumoniae, Chlamydia pneumoniae, Corynebacterium diphtheriae, Francisella tularensis, and Yersinia pestis.

Source: Goldin J, Graber M., 2024 

What happens if a bacterial throat infection is left untreated?

Most bacterial throat infections can be treated easily, but if left untreated, they can sometimes lead to complications. Antibiotics help reduce these risks.

The infection may spread to nearby areas such as the tonsils, sinuses, ears, skin, or even the blood.

In some cases, it can also trigger other conditions, including:

• Scarlet fever (a rash)

• Kidney inflammation

• Rheumatic fever (which can affect the heart and joints)

• Joint inflammation

These complications are uncommon, but they show why timely treatment is important.

Source: Mayo Clinic, 2023 

Treatment: do you always need antibiotics?

A common misconception is that antibiotics are always needed for a sore throat. That is not the case. Antibiotics are only appropriate for confirmed bacterial infections.

For viral throat infections:

• Get plenty of rest

• Stay well hydrated

• Use over-the-counter pain relief such as paracetamol or ibuprofen

For bacterial infections (such as strep):

• A GP may prescribe antibiotics (usually penicillin or amoxicillin)

Do not self-medicate with antibiotics. Incorrect use contributes to antibiotic resistance. If you’re unsure about your symptoms or they are severe, consult your GP.

Source:  Cleveland Clinic, 2025

Testing for a bacterial throat infection at home

Rapid strep tests are commonly used to check if a sore throat is caused by group A streptococcus (strep). They work quickly, giving results within 5 to 10 minutes, which makes them useful at home or in a doctor’s office.

These tests are generally reliable, especially when the result is positive. This means that if the test says you have strep, it’s very likely correct. However, they are not perfect at detecting every case. On average, they correctly identify about 85 out of 100 people with strep throat, meaning some cases may be missed.

While rapid strep tests are a useful and quick first step, they should not replace a professional medical diagnosis.

Source: Cohen, J. F. et al., 2016

When should you see a GP about a sore throat?

You should contact your GP if your sore throat lasts longer than a week or if you experience any of the following:

• Severe throat pain

• Difficulty breathing or swallowing

• Fever above 38°C

• A visible swelling in the back of the throat

• Blood in your saliva or phlegm

• A rash on your body

Soruce: Cleveland Clinic, 2024

Frequently asked questions about bacterial throat infections

Can a bacterial throat infection go away without antibiotics?

Yes, the body can sometimes clear the infection on its own. However, antibiotics can speed up recovery and reduce the risk of complications. It’s best to consult a GP if you’re unsure (Healthdirect Australia, 2023).

How long does a strep throat infection last?

With appropriate treatment, strep throat usually clears up within 7-10 days (Cleveland Clinic, 2022).

Can I spread a bacterial throat infection to others?

Yes, bacterial throat infections can be spread to others. For example, the strep throat is highly contagious. It can be spread through respiratory droplets and direct contact. Even without symptoms, you can still spread the infection to others (Cleveland Clinic, 2022).

What is the difference between tonsillitis and strep throat?

Tonsillitis is inflammation of the tonsils and can be viral or bacterial. Strep throat is specifically caused by group A Streptococcus bacteria and is never viral (Cleveland Clinic, 2022).