Laboratory specimen and possible pathogens

 If pathogens are to be isolated successfully, the type of specimen, its collection time, and method of its dispatch to the laboratorty must be correct. Adequate information about the patient’s condition and antimicrobial treatment must also be sent in the Specimen.

Type of specimen

The correct type of specimen to be collected will depend on the pathogens to be isolated as follows;

SPUTUM

  • Possible pathogens

BACTERIA

Also Mycobacterium tuberculosis, Mycoplasma pneumoniae, and Legionella pneumophila

FUNGI AND ACTINOMYCETES

Pneumocystis jiroveci, Blastomyces dermatitidis, Histoplasma capsulatum, Aspergillus species, Candida albicans, Cryptococcus neoformans, and Nocardia species.

PARASITES

Paragonimus species

  • Commensals

Sputum as it is being collected passes through the pharynx and the mouth. It therefore becomes contaminated with small numbers of commensal organisms from the upper respiratory tract and mouth. These include;

BACTERIA

THROAT AND MOUTH SPECIMENS

  • Possible pathogens
    • GRAM POSITIVE
      • Streptococcus pyogenes
      • Other beta-haemolytic streptococci
      • Corynebacterium diphtheriae
    • GRAM NEGATIVE
      • Vincent’s organisms
    • Virus: 
      • Respiratory viruses, enteroviruses and herpes simplex virus type-I
    • FUNGI
      • Candida albicans and other yeasts.
    • Note: Pathogens in the upper respiratory tract such as Bordetella  pertussis, Streptococcus  pneumoniae, and Neisseria meningitidis, are usually more success-fully   isolated   from   naso-pharyngeal   secretions collected by aspiration.

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