Sore throat is characterized by redness and swelling of the mucosa and throat and enlarged lymph nodes. It can be caused by bacteria like Streptococcus pyogenes or viruses like Epstein-Barr. Symptoms include pain on swallowing, fever, and congested tonsils. Laboratory diagnosis involves collecting a throat swab for microscopy, culture, and antibiotic sensitivity testing to identify the causative organism. While most sore throats are viral and will resolve on their own, bacterial infections like Strep require antibiotic treatment to prevent complications. COVID-19 can also cause sore throat but usually with additional symptoms like fever, loss of taste/smell, and breathing difficulties.

1. Sore throat
Prepared By
Arpita Chandra
Medical Microbiology

2. Sore Throat
• Sore throat is essentially an acute tonsillitis and/or pharyngitis. It is
characterised by redness and oedema of mucosa, pseudo membrane
formation, and enlargement of cervical lymph nodes.
Pseudomembrane
Inflammation of tonsils

4. Causative agents
• Bacteria:-
1. Streptococcus pyogens
2. Streptococcus group C and G
3. Corynebacterium diptheriae
4. Haemophilus influenzae
5. Treponema vicentii
• Fungus
1. Candia albicans
• Virus
1. Epstein-Barr virus
2. Adenovirus
3. Coxsackie virus

5. Symptoms:-
Pain on swallowing Congested tonsils and pharynx Enlarged lymphnodes Pyrexia
• If untreated, streptococcal tonsillitis may give rise to complication such as
peritonsillar abscess, sinusitis or immune complex diseases (rheumatic fever,
glomerulonephritis)

6. Viral vs Bacterial Sore Throat
• The most common cause of a sore throat (pharyngitis) is a
viral infection, such as a cold or the flu. A sore throat caused
by a virus resolves on its own.
• Strep Throat (streptococcal infection- about 15%), less
common type of sore throat caused by bacteria, requires
treatment with antibiotics to prevent complications

7. Laboratory Diagnosis
• Specimen:-
Throat swab
• Collection:-
Two sterile Swabs should be used, one for direct microscopy and another
one for culture. These swabs should include exudate present in the throat.
• Direct microscopy:-
Gram staining and Albert staining may be used for staining the smears.

8. • Culture:-
Culture media are selected according to the organism suspected to be the
causative agent of sore throat.
Following media may be used for culture:-
-Blood agar
-Crystal violet blood agar
-loeffler’s serum slope
-Potassium tellurite blood agar
-Sabourd’s dextrose agar

10. • Identification:-
1. Colony Morphology
2. Gram Staining or Albert Staining
3. Other test for confirmation:
 For β-haemolytic streptococci
(a) Bacitracin sensitivity test for Str. Pyogens
(b) Lancefield grouping for all β-haemolytic streptococci
 For C.diptheriae
(a) Biochemical test
(b) Toxigenicity test
 Elek’s gel precipitation test
 Animal inoculation test

11.  For Candida albicans
(a) Germ tube test
(b) Carbohydrate fermentation assimilation test
• Antibiotic Sensitivity:-
All β-haemolytic group A Streptococci are sensitive to penicillin G, and
most are sensitive to erythromycin.
C.diptheriae is sensitive to penicillin

12. COVID-19
• If you have COVID, Its more common to have other symptoms in
addition to a sore throat.
“Only about 5-10% of COVID -19 patients will have an isolated
sore throat. Usually, they will have a touch of fever. Loss of taste
and smell and difficulty breathing.”

13. Thank
you