SMI summary - throat related specimen

To investigate for:

Pharyngitis, Tonsillitis, Epiglottitis, Laryngitis.

Specimen types:

Throat swab, posterior pharyngeal swab, nasopharyngeal swab, pharyngeal washings, pus aspirate, oropharyngeal swab, throat gargle.

Target organisms - which organisms could cause following infections?

Pharyngitis (sore throat)

Viral (commonest),
Group A Streptococcus
Group C/G Streptococcus
Streptococcus anginosus group,
Corynebacterium – C diphtheriae, C. ulcerans,
Vincent’s angina – Borrelia vincentii and Fusobacterium species,
Arcanobacterium haemolyticum,
Fusobacterium necrophorum.
Neisseria gonorrhoeae.

Rare:

Francisella tularensis, Yersinia enterocolitica, Mycoplasma pneumoniae and Chlamydophila pneumoniae.

Other:

To test for carriage – Neisseria meningitidis, Staph aureus.

Epiglottitis

H. influenzae type b,
Group A Streptococcus
Pseudomonas species and
Mycobacterium tuberculosis.

In immunocompromised patients:

Candida species and Aspergillus

Tonsillitis

Viral infection,
Some bacterial infection – Group A Streptococcus.
Quinsy (peritonsillar abscess):
1. Streptococcus anginosus group,
2. Group A Streptococci,
3. Fusobacterium
4. Anaerobes (Prevotella, Porphyromonas and Peptostreptococcus species),
5. S. aureus

Laryngitis

Viral infection,
Corynebacterium diphtheriae (rare),
MRSA,
Group A streptococci,
Streptococcus pneumoniae,
Haemophilus influenzae and
Mycobacterium tuberculosis or
Fungal (Candida species, Blastomyces species)
Parasite infections.

Non-infectious aetiology:

smoking, alcohol misuse, voice overuse, gastroesophageal reflux disease (GERD), allergies, inhalation of irritants or chemicals.

When to test for Corynebacterium diptheriae/ Corynebacterium ulcerans?

Membranous or pseudomembranous pharyngitis/tonsillitis
Contact with a confirmed case within the last 10 days
Travel abroad to high risk area within the last 10 days
Contact with someone who has been to a high risk area within the last 10 days
Contact with any animals (including household pets, visiting a farm or petting zoo) within the last 10 days
Recent consumption of any type of unpasteurised milk or dairy products
The patient works in a clinical microbiology laboratory, or similar occupation, where Corynebacterium species may be handled

Reported diphtheria cases 2019 (WHO) https://apps.who.int/immunization_monitoring/globalsummary/timeseries/tsincidencediphtheria.html

Processing specimen

Gram stain

Stain for Vincent’s organisms: report on Vincent’s organisms detected.

Plate selection

Organisms should be isolated up to species level, except yeast – which can be left at yeast level.
Beta-haemolytic Streptococcus should be tested by Lancefield grouping.
Any C diphtheriae/ C ulcerans should be referred to the reference lab for toxigenicity test ASAP.
H influenza should be referred to the reference lab for grouping if it is epiglottitis.

C diphtheriae on telluride agar
(http://www.medical-labs.net/corynebacterium-diphtheriae-on-tellurite-agar-2180/)

Safety, infection control and public health - C diphtheriae/ C ulcerans

Corynebacterium diphtheriae, Corynebacterium ulcerans

C. diphtheriae and C. ulcerans are in Hazard group 2. Suspected and known isolates of C. diphtheriae /C. ulcerans should always be handled in a microbiological safety cabinet. Sometimes the nature of the work may dictate that full containment Level 3 conditions should be used eg for the propagation of C. diphtheriae/C. ulcerans in order to comply with COSHH 2004 Schedule 3 (4e).

Diphtheria is a notifiable disease in the UK.

Lab should immediately inform microbiologists
Infection control team should be notified ASAP.
UKHSA should be notified on suspicion, on an urgent basis for management of the case, contacts and outbreak.
In the healthcare setting, appropriate infection control measures should be taken.
All isolates should be referred to the reference lab for toxigenicity test.

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