Microbiology Laboratory


Written by MicroDok

Throat swab culture is usually in the diagnosis of upper respiratory tract infections (URTIs) e.g. pharyngitis, Otitis media and epiglottitis. URTIs are infections of that begins from the larynx to the nostrils and, it also involves other communicating cavities that are connected to the respiratory tract and nostrils e.g. the middle ear and its sinuses.     

AIM: To isolate pathogenic bacteria from throat swab specimen as an aid in the diagnosis of upper respiratory tract infections.

MATERIAL/APPARATUS: Throat swab, blood agar (BA), chocolate agar (CA), cysteine lactose – electrolyte deficient (CLED) agar, inoculating loop, anaerobic jar, incubator, grease pencil, Bunsen burner.


  1. Label the CA, BA, and CLED plates with patient’s name and laboratory number using the grease pencil.
  2. Inoculate the throat swab specimen on the CLED, BA, and CA plates.
  3. Incubate the CLED and the BA plates in the incubator at 37oC overnight.
  4. Incubate the CA plate in the anaerobic jar at 37oC overnight.
  5. Examine the culture plates for significant bacterial growth after incubation.
  6. Perform biochemical tests on significant bacteria pathogens isolated.
  7. Perform antimicrobial susceptibility testing only on significant bacteria isolates.


Cultures of throat swabs are most reliable if inoculated promptly after collection. The normal throat flora includes an abundance of viridians Streptococci, Neisseria, diphtheroids, Staphylococci, small Gram negative rods, and other organisms.

The reporting of a throat swab culture should be done with utmost care so as not to report a normal bacterial flora found in the throat, giving that the oral cavity is flooded with a wide variety of bacteria that are resident in the mouth.

Microscopical analysis though of little significance can also be used in investigating an upper respiratory tract infection. It is not often used because of the predominance of Streptococci in all throats

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