Thursday, April 5, 2012

Sinus puncture: a traditional method to obtain sinus culture

Sinus puncture: a traditional method to obtain sinus culture

To decide an appropriate antimicrobial therapy for sinuses’ infection, a thorough understanding of the sinus microbiology is the prerequisite. Different methods, including sinus puncture, are used to analyze the microbiology. Sinus puncture, the traditional method to collect sinus aspirates, is used when the patient does not respond to the medicine, the patient’s condition deteriorates or the immune system of the patient is compromised / weak. The puncture will reveal bacteria causing the sinuses’ infection.

While obtaining sinus aspirates, normal flora and saprophytic organisms shall not contaminate the specimens. Even a slightest presence of normal flora in the sinus aspirates can mislead the physician because numerous indigenous anaerobic and aerobic bacteria reside in the nasopharyngeal mucous membranes.  The puncture is the best method to obtain such contamination free aspirates. The cultures based on contamination free aspirates can be studied and analyzed properly.
Two different approaches are adopted to puncture the maxillary sinus, which is easily accessible as compared to the other paranasal sinuses. The maxillary sinus can be punctured via the inferior meatus or the canine fossa. Before puncturing, the region lying below the inferior nasal turbinate and the nasal vestibule should be sterilized because S. aureus and other causative bacteria occur in large number in the nasal vestibule.
Despite all precautions, nasal flora may contaminate the specimens. So, the culture results can be misinterpreted. To avoid this, the acute infection has been redefined quantitatively. If the density of the bacterial species is high, the infection is acute. Bacterial density of 104 colony-forming units per millimeter helps in differentiating between contamination and bacterial colonization.
When quantitative analysis is not possible, a Gram stain of the specimens helps in semi-quantitative analysis.  Bacterial presence in the Gram stain aids in estimating the bacterial density. If a positive culture with high density of bacteria has several white blood cells, the infection may be bacterial. However, a Gram stain cannot distinguish between eosinophils and neutrophils.
The Scandinavian scientists have been using sinus puncture since mid 1950s. Now-a-days, even the US scientists also use the method. Sinus puncture is preferred for patients having severe sinuses’ infection. Sinus puncture is also common for research works. Sinus puncture is a safe method if performed by a professional and experienced doctor. It is less painful.  However, the invasive method may not be possible in primary care centers.

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