Background
Streptococcus often causes throat infections, including tonsillitis and pharyngitis- these are commonly referred to as ‘strep throat’. The most common subtype causing this is Group A β-haemolytic streptococcus
Streptococcal throat infections are often self-limiting, with symptoms resolving completely within two weeks. However it can sometimes lead to complications such as scarlet fever and rheumatic fever. Scarlet fever is when a characteristic rash develops after a streptococcal infection – this is known as a ‘scarlatina’ rash – it is diffuse, papular and has a texture like ‘sandpaper’. The rash develops as a result of a toxin produced by the streptococcus. A ‘strawberry tongue’ and circumoral pallor may be present, and desquamation of fingers and toes, and ‘Pastia’s’ lines in the flexures may also be present. Rheumatic fever is rare in developed countries, due to rapid diagnosis and availability of antibiotics.
Streptococcal throat infections are common in children aged 4-8 years and usually present in inter or early springtime. The streptococcal bacteria are spread by droplet transmission – for example coughing, sneezing or touching contaminated surfaces and then one’s face.
Signs & symptoms
- Sore throat
- Cervical lymphadenopathy
- Tonsillar hypertrophy and inflammation, with exudate
- Fever
- Headache
Diagnosis
Diagnosis of streptococcal throat infections is made by history and clinical examination.
The Centor criteria can be used to create a score, which indicates the likelihood of the patient having streptococcal pharyngitis, which can help guide management. These are as follows:
- Tonsillar exudate
- Tender anterior cervical lymphadenopathy
- Fever (>38 degrees Celsius)
- Absence of cough
Each of the above scores 1 point, a score of 3 or 4 indicates a 32-56% likelihood of streptococcal infection and NICE guidance recommends the consideration of antibiotic treatment.
A throat swab can be taken and cultured, to identify a causative bacterium; this is more useful if there is ambiguity about the diagnosis.
A rapid antigen test for the Group A Streptococcus is also available, however they are not currently recommended by NICE as they are not cost-effective.
Differentials
- Epiglottitis
- Viral pharyngitis (e.g. Epstein-Barr virus, measles, influenza)
- Peritonsilar abscess
- Diphtheria (uncommon in developed countries)
Management
- First line – supportive care (e.g. paracetamol, salt water gargle, encourage oral fluids and hot drinks). Consider using emollient cream for the rash +/- antihistamine if rash is itchy.
- If the Centor score is ≥ 3 (or patient has a microbiologically confirmed group A strep infection) then antibiotic therapy is recommended. Phenoxymethylpenicillin is commonly first line treatment.
- Antibiotic prophylaxis may be given if the patient has a history of rheumatic fever – to prevent a recurrence.
References
https://bestpractice.bmj.com/topics/en-gb/5
https://www.nice.org.uk/guidance/ng84/chapter/terms-used-in-the-guideline