Sinus samples are obtained by surgery. One of the most common samples is “antral washings” from the maxillary sinus where volumes of saline are used to wash out sinus contents.
Acute sinusitis commonly involves upper respiratory tract organisms such as S. pneumoniae, H. influenzae, M. catarrhalis and Group A streptococcus. S. aureus, B. cepacia and P. aeruginosa are also potential pathogens especially in immunocompromised patients. Anaerobic and fungal cultures are done on request only.
Nasal and nasopharyngeal specimens are unacceptable for diagnosis of sinusitis and are cultured for Staphylococcus aureus colonization only.
Direct examination
Gram stain
Culture
| Media | Incubation |
| Blood Agar (BA) | CO2, 35°C x 48 hours |
| Chocolate Agar (CHOC) | CO2, 35°C x 48 hours |
| MacConkey Agar (MAC) | O2, 35°C x 48 hours |
If fungi requested, add:
| Sabouraud’s Heart Infusion Agar (SABHI) | O2, 30°C x 4 weeks |
| SABHI with Chloramphenicol (SABHI-C) | O2, 30°C x 4 weeks |
If anaerobes are requested, add:
| Wilkins Chalgren Agar (WC) | AnO2, 35°C x 48 hours |
| WC Nalidixic acid – Tween 80 (NAT) | AnO2, 35°C x 48 hours |
| WC Nalidixic acid – Vancomycin (NAV) | AnO2, 35°C x 48 hours |
A wide array of unusual organisms have been occasionally isolated so a moderate to heavy pure growth of any organism should raise suspicion and prompt consultation with the lead technologist or microbiologist.
Gram stain
Report with quantitation the presence of pus cells and organisms.
Culture
Negative report
“Normal oral flora” or “No growth”.
“No anaerobes isolated” if anaerobic culture is requested.
Positive report
Quantitate and report significant isolates with appropriate sensitivities. Report “Normal oral flora” if also present.
H.D. Izenberg. 2003. Nasal Sinus Cultures, 3.11.9.1 in Clinical Microbiology Procedures Handbook, 2nd ed. Vol.1 ASM Press, Washington, D.C.