Work up of ENT specimens in the clinical microbiology laboratory
ENT sites (sinus, tonsils, nasal, etc.) are typically predominantly colonized by normal flora. Allina Health Laboratory follows clinical infectious disease society of America (IDSA) guidelines, clinical laboratory standards of institute’s (CLSI) guidelines, and any pertinent laboratory regulatory standards for appropriate performance and reporting of test results for any cultures, including ENT samples.
- Antimicrobial susceptibility testing is not performed for every organism/result that has been reported, because the growth of every organism does not always signify the cause of infection.
- Our Laboratory follows guidelines in performing automated susceptibilities for potential pathogens. Any other reported organisms are not always considered “causation,” and more often, they represent colonizers. Patient management should be considered within the clinical context.
- Routine Susceptibility testing is not recommended for such organisms from ENT sites.
- Some potential pathogens commonly associated with ENT infections, such as Haemophilus influenzae, Moraxella catarrhalis, Actinomyces, or Nocardia, do not have susceptibility testing results as Ampicillin/Penicillin or sulfonamide is typically the drug of choice.
- Quality samples in appropriate transport media will produce quality results.
- For single organisms reported indicating predominant bacteria in the normal flora does not always indicate causative agent. Susceptibilities can be requested if clinically indicated.
According to IDSA guidelines and the American Thoracic Society’s report:
- Sinus specimens: In order to maximize optimal sensitivity and specificity of culture results and appropriate workup, swabs are not recommended for collecting sinus specimens
- Aspirate is much more productive of true etiologic agent(s) and is the specimen of choice.
- Surgical procedure samples (Tissues, aspirates, drainage from endoscopic guidance, ): are preferred over swabs.
- Nasal drainage: Examination of nasal drainage materials may be of no or little clinical values to determine the cause of maxillary sinusitis (IDSA).
- Examples of common colonizers of ENT sites: Coagulase Negative Staphylococcus, Corynebacterium species, Streptococcus viridans, Saprophytic Neisseria, etc,.
- The explanation of mixed or Normal flora in microbiology reports: Most ENT cultures are reported as “mixed flora” or normal flora, when there are no apparent pathogens and only have an overwhelming amount of mixed colonizing microorganisms. Antimicrobial susceptibility testing should not be performed on normal flora.
Society literature References for additional information:
Microbiology of Sinusitis | Proceedings of the American Thoracic Society (atsjournals.org)